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A polynomial formulation of adaptive strong stability preserving multistep methods
https://lup.lub.lu.se/search/publication/cc6cfde0240b4ba596c0d1c23250cbe5
Mohammadi, Fatemeh
Arevalo, Carmen
Fuhrer, Claus
2019
A new formulation of explicit multistep methods allows variable stepsizes by construction. This formulation can be used to construct timeadaptive strong stability preserving (SSP) multistep methods of any order for the solution of timedependent PDEs. The new formulation is implemented in a MATLAB package, and some numerical examples are presented.
http://lup.lub.lu.se/record/cc6cfde0240b4ba596c0d1c23250cbe5
http://dx.doi.org/10.1137/17M1158811
scopus:85062683583
eng
SIAM Journal on Numerical Analysis; 57(1), pp 2743 (2019)
ISSN: 00361429
Matematik
Adaptive SSP multistep methods
Strong stability preserving
TVD schemes
Variable stepsizes
A polynomial formulation of adaptive strong stability preserving multistep methods
contributiontojournal/article
info:eurepo/semantics/article
text

Generalization of Parameter Recovery in Binocular Vision for a Planar Scene
https://lup.lub.lu.se/search/publication/ec0babb2d0124f32856eccaada25b8ef
Örnhag, Marcus Valtonen
Heyden, Anders
2019
In this paper, we consider a mobile platform with two cameras directed towards the floor. In earlier work, this specific problem geometry has been considered under the assumption that the cameras have been mounted at the same height. This paper extends the previous work by removing the height constraint, as it is hard to realize in reallife applications. We develop a method based on an equivalent problem geometry, and show that much of previous work can be reused with small modification to account for the height difference. A fast solver for the resulting nonconvex optimization problem is devised. Furthermore, we propose a second method for estimating the height difference by constraining the mobile platform to pure translations. This is intended to simulate a calibration sequence, which is not uncommon to impose. Experiments are conducted using synthetic data, and the results demonstrate a robust method for determining the relative parameters comparable to previous work.
http://lup.lub.lu.se/record/ec0babb2d0124f32856eccaada25b8ef
http://dx.doi.org/10.1142/S0218001419400111
scopus:85062627714
eng
International Journal of Pattern Recognition and Artificial Intelligence; (2019)
ISSN: 02180014
Datorseende och robotik (autonoma system)
binocular vision
homography
planar motion
Relative pose estimation
SLAM
visual odometry
Generalization of Parameter Recovery in Binocular Vision for a Planar Scene
contributiontojournal/article
info:eurepo/semantics/article
text

The Distribution of Superconductivity Near a Magnetic Barrier
https://lup.lub.lu.se/search/publication/d875105c30ac4647a32f6aba30fea26f
Assaad, Wafaa
Kachmar, Ayman
PerssonSundqvist, Mikael
20190206
We consider the Ginzburg–Landau functional, defined on a twodimensional simply connected domain with smooth boundary, in the situation when the applied magnetic field is piecewise constant with a jump discontinuity along a smooth curve. In the regime of large Ginzburg–Landau parameter and strong magnetic field, we study the concentration of the minimizing configurations along this discontinuity by computing the energy of the minimizers and their weak limit in the sense of distributions.
http://lup.lub.lu.se/record/d875105c30ac4647a32f6aba30fea26f
http://dx.doi.org/10.1007/s0022001903284z
scopus:85061244597
eng
Communications in Mathematical Physics; (2019)
ISSN: 00103616
Annan fysik
Matematik
The Distribution of Superconductivity Near a Magnetic Barrier
contributiontojournal/article
info:eurepo/semantics/article
text

Estimating the hinderedsettling flux function from a batch test in a cone
https://lup.lub.lu.se/search/publication/02a90e3c6a4247f5ba1c21f0bef578aa
Bürger, Raimund
Careaga, Julio
Diehl, Stefan
Merckel, Ryan
Zambrano, Jesús
20181231
The hinderedsettling velocity function for the modelling, simulation and control of secondary settling tanks can be determined from batch tests. The conventional method is to measure the velocity of the descending sludgesupernatant interface (sludge blanket) as the change in height over time in a vessel with constant crosssectional area. Each such experiment provides one point on the flux curve since, under idealizing assumptions (monodisperse suspension, no walleffects), the concentration of sludge remains constant just below the sludge blanket until some wave from the bottom reaches it. A newly developed method of estimation, based on the theory of nonlinear hyperbolic partial differential equations, is applied to both synthetic and experimental data. The method demonstrates that a substantial portion of the flux function may be estimated from a single batch test in a conical vessel. The new method takes into consideration that during an ideal settling experiment in a cone, the concentration just below the sludge blanket increases with time since the mass of suspended solids occupy a reduced volume over time.
http://lup.lub.lu.se/record/02a90e3c6a4247f5ba1c21f0bef578aa
http://dx.doi.org/10.1016/j.ces.2018.07.029
scopus:85050301217
eng
Chemical Engineering Science; 192, pp 244253 (2018)
ISSN: 00092509
Kemiteknik
Matematik
Identification
Inverse problem
Partial differential equation
Sedimentation
Estimating the hinderedsettling flux function from a batch test in a cone
contributiontojournal/article
info:eurepo/semantics/article
text

Generalization of prostate cancer classification for multiple sites using deep learning
https://lup.lub.lu.se/search/publication/3794a793341a4efeadc1e19d9d3130a6
Arvidsson, Ida
Overgaard, Niels Christian
Marginean, Felicia Elena
Krzyzanowska, Agnieszka
Bjartell, Anders
Astrom, Kalle
Heyden, Anders
20180523
Deep learning has the potential to drastically increase the accuracy and efficiency of prostate cancer diagnosis, which would be of uttermost use. Today the diagnosis is determined manually from H&E stained specimens using a light microscope. In this paper several different approaches based on convolutional neural networks for prostate cancer classification are presented and compared, using three different datasets with different origins. The issue that algorithms trained on a certain site might not generalize to other sites, due to for example inevitable stain variations, is highlighted. Two different techniques to overcome this complication are compared; by training the networks using color augmentation and by using digital stain separation. Furthermore, the potential of using an autoencoder to get a more efficient downsampling is investigated, which turned out to be the method giving the best generalization. We achieve accuracies of 95% for classification of benign versus malignant tissue and 81% for Gleason grading for data from the same site as the training data. The corresponding accuracies for images from other sites are in average 88% and 52% respectively.
http://lup.lub.lu.se/record/3794a793341a4efeadc1e19d9d3130a6
http://dx.doi.org/10.1109/ISBI.2018.8363552
ISBN: 9781538636367
scopus:85048138355
eng
Radiologi och bildbehandling
Autoencoder
Convolutional neural network
Digital stain separation
Gleason grade
Prostate cancer
Generalization of prostate cancer classification for multiple sites using deep learning
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Estimating Uncertainty in Timedifference and Doppler Estimates
https://lup.lub.lu.se/search/publication/0f3549364b19442fbac5458cafd279c1
Flood, Gabrielle
Heyden, Anders
Åström, Karl
201801
Sound and radio can be used to estimate the distance between a transmitter and a sender by correlating the emitted and received signal. Alternatively by correlating two received signals it is possible to estimate distance difference. Such methods can be divided into methods that are robust to noise and reverberation, but give limited precision and subsample refinements that are sensitive to noise, but give higher precision when initialized close to the real translation. In this paper we develop stochastic models that can explain the limits in the precision of such subsample timedifference estimates. Using such models we provide new methods for precise estimates of timedifferences as well as Doppler effects. The method is verified on both synthetic and real data.
http://lup.lub.lu.se/record/0f3549364b19442fbac5458cafd279c1
http://dx.doi.org/10.5220/0006722002450253
ISBN: 9789897582769
scopus:85052020465
eng
Matematik
Datorseende och robotik (autonoma system)
Timedifference of Arrival
Subsample Methods
Doppler Effect
Uncertainty Measure
Estimating Uncertainty in Timedifference and Doppler Estimates
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Natural variation in the parameters of innate immune cells is preferentially driven by genetic factors
https://lup.lub.lu.se/search/publication/856ab6b2b1f140a6aa601f2d51d455cf
Patin, Etienne
Hasan, Milena
Bergstedt, Jacob
Rouilly, Vincent
Libri, Valentina
Urrutia, Alejandra
Alanio, Cécile
Scepanovic, Petar
Hammer, Christian
Jönsson, Friederike
Beitz, Benoît
Quach, Helene
Lim, Yoong Wearn
Hunkapiller, Julie
Zepeda, Magge
Green, Cherie
Piasecka, Barbara
Leloup, Claire
Rogge, Lars
Huetz, François
Peguillet, Isabelle
Lantz, Olivier
Fontes, Magnus
Santo, James P.
Thomas, Stéphanie
Fellay, Jacques
Duffy, Darragh
QuintanaMurci, Lluis
Albert, Matthew L
,
20180223
The quantification and characterization of circulating immune cells provide key indicators of human health and disease. To identify the relative effects of environmental and genetic factors on variation in the parameters of innate and adaptive immune cells in homeostatic conditions, we combined standardized flow cytometry of blood leukocytes and genomewide DNA genotyping of 1,000 healthy, unrelated people of Western European ancestry. We found that smoking, together with age, sex and latent infection with cytomegalovirus, were the main nongenetic factors that affected variation in parameters of human immune cells. Genomewide association studies of 166 immunophenotypes identified 15 loci that showed enrichment for diseaseassociated variants. Finally, we demonstrated that the parameters of innate cells were more strongly controlled by genetic variation than were those of adaptive cells, which were driven by mainly environmental exposure. Our data establish a resource that will generate new hypotheses in immunology and highlight the role of innate immunity in susceptibility to common autoimmune diseases.
http://lup.lub.lu.se/record/856ab6b2b1f140a6aa601f2d51d455cf
http://dx.doi.org/10.1038/s4159001800497
scopus:85042410142
eng
Nature Immunology; 19, pp 302314 (2018)
ISSN: 15292908
Immunologi inom det medicinska området
Natural variation in the parameters of innate immune cells is preferentially driven by genetic factors
contributiontojournal/article
info:eurepo/semantics/article
text

Efficient Solvers for Minimal Problems by Syzygybased Reduction
https://lup.lub.lu.se/search/publication/e10f73813eeb43e8b1385c3f8c2cde74
Larsson, Viktor
Åström, Karl
Oskarsson, Magnus
201707
In this paper we study the problem of automatically generatingpolynomial solvers for minimal problems. The maincontribution is a new method for finding small eliminationtemplates by making use of the syzygies (i.e. the polynomialrelations) that exist between the original equations. Usingthese syzygies we can essentially parameterize the setof possible elimination templates.We evaluate our method on a wide variety of problemsfrom geometric computer vision and show improvementcompared to both handcrafted and automatically generatedsolvers. Furthermore we apply our method on two previouslyunsolved relative orientation problems.
http://lup.lub.lu.se/record/e10f73813eeb43e8b1385c3f8c2cde74
http://dx.doi.org/10.1109/CVPR.2017.256
ISBN: 9781538604588
ISBN: 9781538604571
scopus:85041930337
eng
Datorseende och robotik (autonoma system)
Efficient Solvers for Minimal Problems by Syzygybased Reduction
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Towards Realtime TimeofArrival SelfCalibration using UltraWideband Anchors
https://lup.lub.lu.se/search/publication/ef87164359104eeb9f69e78b2dbc761c
Batstone, Kenneth John
Oskarsson, Magnus
Åström, Karl
201709
Indoor localisation is a currently a key issue, from robotics to the Internet of Things. With hardware advancements making UltraWideband devices more accurate and low powered (potentially even passive), this unlocks the potential of having such devices in common place around factories and homes, enabling an alternative method of navigation. Therefore, anchor calibration indoors becomes a key problem in order to implement these devices efficiently and effectively. In this paper, we study the possibility for sequentially gathering UltraWideband TimeofArrival measurements and using previously studied robust solvers, merge solutions together in order to calculate anchor positions in 3D in realtime. Here it is assumed that there is no prior knowledge of the anchor positions. This is then validated using UltraWideband TimeofArrival data gathered by a Bitcraze Crazyflie quadcopter in 2D motion, 3D motion and full flight.
http://lup.lub.lu.se/record/ef87164359104eeb9f69e78b2dbc761c
http://dx.doi.org/10.1109/IPIN.2017.8115885
scopus:85043464160
eng
Datorseende och robotik (autonoma system)
Towards Realtime TimeofArrival SelfCalibration using UltraWideband Anchors
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Polynomial Solvers for Saturated Ideals
https://lup.lub.lu.se/search/publication/9c5a8ff457af4ffa820ccb51ee4c0e65
Larsson, Viktor
Åström, Karl
Oskarsson, Magnus
201710
In this paper we present a new method for creating polynomialsolvers for problems where a (possibly infinite) subsetof the solutions are undesirable or uninteresting. Thesesolutions typically arise from simplifications made duringmodeling, but can also come from degeneracies which areinherent to the geometry of the original problem.The proposed approach extends the standard action matrixmethod to saturated ideals. This allows us to add constraintsthat some polynomials should be nonzero on thesolutions. This does not only offer the possibility of improvedperformance by removing superfluous solutions, butmakes a larger class of problems tractable. Previously,problems with infinitely many solutions could not be solveddirectly using the action matrix method as it requires azerodimensional ideal. In contrast we only require thatafter removing the unwanted solutions only finitely manyremain. We evaluate our method on three applications, optimaltriangulation, timeofarrival selfcalibration and optimalvanishing point estimation.
http://lup.lub.lu.se/record/9c5a8ff457af4ffa820ccb51ee4c0e65
http://dx.doi.org/10.1109/ICCV.2017.251
ISBN: 9781538610329
scopus:85041894297
eng
Datorseende och robotik (autonoma system)
Polynomial Solvers for Saturated Ideals
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

What is a “unimodal” cell population? Using statistical tests as criteria for unimodality in automated gating and quality control
https://lup.lub.lu.se/search/publication/9f0c36469c964e7f97cce4090526f34e
Johnsson, Kerstin
Linderoth, Magnus
Fontes, Magnus
20170901
Many automated gating algorithms for flow cytometry data are based on the concept of unimodal cell populations. However, in this article, we show that criteria previously used to make decisions on unimodality cannot adequately distinguish unimodal from bimodal densities. We show that dip and bandwidth tests for unimodality, taken from the statistics literature, can do this with consistent and low error rates. These tests also have the possibility to adjust the significance level to handle the tradeoff between failing to detect a second mode and seeing a second mode when there is none. The differences between the dip and bandwidth tests are elucidated using real data from the FlowCAP I challenge, also guidelines for flow cytometry data preprocessing are given.
http://lup.lub.lu.se/record/9f0c36469c964e7f97cce4090526f34e
http://dx.doi.org/10.1002/cyto.a.23173
scopus:85026477395
eng
Cytometry Part A; 91(9), pp 908916 (2017)
ISSN: 15524922
Biofysik
Sannolikhetsteori och statistik
automated gating
bandwidth test
calibration
data analysis
dip test
flow cytometry
quality control
unimodality
What is a “unimodal” cell population? Using statistical tests as criteria for unimodality in automated gating and quality control
contributiontojournal/article
info:eurepo/semantics/article
text

Cellular traction forces : a useful parameter in cancer research
https://lup.lub.lu.se/search/publication/a0a832ea7754480bb3da7f2501eb1093
Li, Zhen
Persson, Henrik
Adolfsson, Karl
Abariute, Laura
Borgström, Magnus T
Hessman, Dan
Åström, Kalle
Oredsson, Stina
Prinz, Christelle N
20171214
The search for new cancer biomarkers is essential for fundamental research, diagnostics, as well as for patient treatment and monitoring. Whereas most cancer biomarkers are biomolecules, an increasing number of studies show that mechanical cues are promising biomarker candidates. Although cell deformability has been shown to be a possible cancer biomarker, cellular forces as cancer biomarkers have been left largely unexplored. Here, we measure traction forces of cancer and normallike cells at high spatial resolution using a robust method based on dense vertical arrays of nanowires. A force map is created using automated image analysis based on the localization of the fluorescent tips of the nanowires. We show that the force distribution and magnitude differ between MCF7 breast cancer cells and MCF10A normallike breast epithelial cells, and that monitoring traction forces can be used to investigate the effects of anticancer drugs.
http://lup.lub.lu.se/record/a0a832ea7754480bb3da7f2501eb1093
http://dx.doi.org/10.1039/c7nr06284b
scopus:85027972721
scopus:85038413765
wos:000418098000005
eng
Nanoscale; 9(48), pp 1903919044 (2017)
ISSN: 20403372
Cancer och onkologi
Radiologi och bildbehandling
Journal Article
Cellular traction forces : a useful parameter in cancer research
contributiontojournal/article
info:eurepo/semantics/article
text

Semantic segmentation of microscopic images of H&E stained prostatic tissue using CNN
https://lup.lub.lu.se/search/publication/4a850c7f30194750803078fa984a2fcb
Isaksson, Johan
Arvidsson, Ida
Åström, Kalle
Heyden, Anders
20170630
There is a need for an automatic Gleason scoring system that can be used for prostate cancer diagnosis. Today the diagnoses are determined by pathologists manually, which is both a complex and a timeconsuming task. To reduce the pathologists' workload, but also to reduce variations between different pathologists, an automatic classification system would be of great use. Some previous works have aimed for this, but still more work needs to be done. It is probable that such a tool would benefit from having access to individually segmented, pathologically relevant objects from the images. Therefore, we have developed an algorithm for semantic segmentation of the microscopic images of H&E stained prostate tissue into Background, Stroma, Epithelial Cytoplasm and Nuclei. This algorithm is based on deep learning, or more specifically a convolutional neural network. The network design is inspired by architectures that previously have been proved successful in different applications. It consists of a contracting and an expanding part, which are symmetrical. We have reached an accuracy of 80 %, as measured by the mean of the intersection over union, for segmentation into four classes. Previous works have only investigated nuclei segmentation, and our network performed similar but for the more challenging task of four class segmentation.
http://lup.lub.lu.se/record/4a850c7f30194750803078fa984a2fcb
http://dx.doi.org/10.1109/IJCNN.2017.7965996
ISBN: 9781509061815
scopus:85031034057
eng
Radiologi och bildbehandling
Semantic segmentation of microscopic images of H&E stained prostatic tissue using CNN
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

A simulation model for settling tanks with varying crosssectional area
https://lup.lub.lu.se/search/publication/044368eb36e24669967d22119ca1d2ab
Bürger, Raimund
Careaga, Julio
Diehl, Stefan
20171102
A quasionedimensional model of the process of continuous sedimentation in clarifierthickeners (settlers) with variable crosssectional area is presented. The partial differential equation (PDE) model extends the settler model advanced by Bürger et al. (2013), which assumes a constant cross section. A reliable numerical method that handles the special features of the nonlinear PDE is presented along with an advantageous timestep condition for continuous and batch sedimentation under the condition of a variable crosssectional area. Simulations of continuous sedimentation show the effect of change of crosssectional area in the concentration inside the vessel and in the underflow. Simulations of batch settling in cones illustrate the versatility of the numerical scheme to include a vertex, where the area shrinks to zero.
http://lup.lub.lu.se/record/044368eb36e24669967d22119ca1d2ab
http://dx.doi.org/10.1080/00986445.2017.1360871
scopus:85029685838
wos:000413852100005
eng
Chemical Engineering Communications; 204(11), pp 12701281 (2017)
ISSN: 00986445
Beräkningsmatematik
Clarifierthickener
continuous sedimentation
nonlinear conservation PDE
numerical method
secondary clarifier
A simulation model for settling tanks with varying crosssectional area
contributiontojournal/article
info:eurepo/semantics/article
text

A generalization of the sparse iterative covariancebased estimator
https://lup.lub.lu.se/search/publication/f2882b4bf82848148fa03f309ca6a9bd
Sward, Johan
Adalbjornsson, Stefan Ingi
Jakobsson, Andreas
20170616
In this work, we extend the popular sparse iterative covariancebased estimator (SPICE) by generalizing the formulation to allow for different norm constraint on the signal and noise parameters in the covariance model. For any choice of norms, the resulting generalized SPICE method enjoys the same benefits as the regular SPICE method, including being hyperparameter free, although the choice of norm is shown to govern the sparsity in the resulting solution. Furthermore, we show that there is a connection between the generalized SPICE and a penalized regression problem, both for the case were one allows the noise parameters to differ for each sample, and when treating each noise parameter as being equal. We examine the performance of the method for different choices of norms, and compare the results to the original SPICE method, showing the benefits of using the generalized version. We also provide a way of solving the generalized SPICE using a gridless method, which solves a semidefinite programming problem.
http://lup.lub.lu.se/record/f2882b4bf82848148fa03f309ca6a9bd
http://dx.doi.org/10.1109/ICASSP.2017.7952898
ISBN: 9781509041176
scopus:85023745907
eng
Signalbehandling
convex optimization
Covariance fitting
sparse reconstruction
A generalization of the sparse iterative covariancebased estimator
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Deblending seismic data by directionality penalties
https://lup.lub.lu.se/search/publication/30ab8234970246d58a205b8e1220fefc
Andersson, F.
Wittsten, J.
Ramirez, A. C.
Wiik, Torgeir
2016
In conventional seismic surveys, there is a waiting time between sequentially fired shots. This time is determined such that the deepest reflection of interest is recorded before the following source is fired. In a survey with simultaneous or blended sources, the waiting time between the firing of shots is not dependent on the deepest reflection of interest, it is usually much shorter and/or can have random time delays. Thus, the wavefields due to independent sources are overlapped in the records. The blended data exhibit strong discontinuities in the source direction, in contrast to the coherency expected from seismic measurements. A strategy for deblending could then be to suppress these discontinuities. In this paper, we propose to do this by designing an energy functional that uses a combination of individual functionals that penalize deviations from local plane waves in the reconstructed (deblended) data, as well as a least squares term that penalizes discrepancies between the deblended and the measured data. In this way, we derive a set of coupled nonlinear partial differential equations that we use for the deblending procedure.
http://lup.lub.lu.se/record/30ab8234970246d58a205b8e1220fefc
http://dx.doi.org/10.3997/22144609.201601410
ISBN: 9789462821859
scopus:85020204178
eng
Geologi
Energiteknik
Deblending seismic data by directionality penalties
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Timeresolved tracking of the atrioventricular plane displacement in Cardiovascular Magnetic Resonance (CMR) images
https://lup.lub.lu.se/search/publication/ec4147a5f8974e78981da690abca3c00
Seemann, Felicia
Pahlm, Ulrika
Steding Ehrenborg, Katarina
Ostenfeld, Ellen
DuboisRandé, JeanLuc
Atar, Dan
Arheden, Håkan
Carlsson, Marcus
Heiberg, Einar
2017
BACKGROUND:Atrioventricular plane displacement (AVPD) is an indicator for systolic and diastolic function and accounts for 60% of the left ventricular, and 80% of the right ventricular stroke volume. AVPD is commonly measured clinically in echocardiography as mitral and tricuspid annular plane systolic excursion (MAPSE and TAPSE), but has not been applied widely in cardiovascular magnetic resonance (CMR). To date, there is no robust automatic algorithm available that allows the AVPD to be measured clinically in CMR with input in a single timeframe. This study aimed to develop, validate and provide a method that automatically tracks the left and right ventricular AVPD in CMR images, which can be used in the clinical setting or in applied cardiovascular research in multicenter studies.METHODS:The proposed algorithm is based on template tracking by normalized crosscorrelation combined with a priori information by principal component analysis. The AVPD in each timeframe is calculated for the left and right ventricle separately using CMR longaxis cine images of the 2, 3, and 4chamber views. The algorithm was developed using a training set (n = 40), and validated in a test set (n = 113) of healthy subjects, athletes, and patients after STelevation myocardial infarction from 10 centers. Validation was done using manual measurements in end diastole and end systole as reference standard. Additionally, AVPD, peak emptying velocity, peak filling velocity, and atrial contraction was validated in 20 subjects, where timeresolved manual measurements were used as reference standard. Interobserver variability was analyzed in 20 subjects.RESULTS:In end systole, the difference between the algorithm and the reference standard in the left ventricle was (mean ± SD) 0.6 ± 1.9 mm (R = 0.79), and 0.8 ± 2.1 mm (R = 0.88) in the right ventricle. Interobserver variability in end systole was 0.6 ± 0.7 mm (R = 0.95), and 0.5 ± 1.4 mm (R = 0.95) for the left and right ventricle, respectively. Validation of peak emptying velocity, peak filling velocity, and atrial contraction yielded lower accuracy than the displacement measures.CONCLUSIONS:The proposed algorithm show good agreement and low bias with the reference standard, and with an agreement in parity with interobserver variability. Thus, it can be used as an automatic method of tracking and measuring AVPD in CMR.
http://lup.lub.lu.se/record/ec4147a5f8974e78981da690abca3c00
http://dx.doi.org/10.1186/s1288001701895
scopus:85025083129
wos:000395944400001
swe
BMC Medical Imaging; 17(19) (2017)
ISSN: 14712342
Biomedicinsk laboratorievetenskap/teknologi
Timeresolved tracking of the atrioventricular plane displacement in Cardiovascular Magnetic Resonance (CMR) images
contributiontojournal/article
info:eurepo/semantics/article
text

Action sequencing in the spontaneous swimming behavior of zebrafish larvae  implications for drug development
https://lup.lub.lu.se/search/publication/abd40bf47bf0459fa6ab93fbecf06c7e
Palmér, Tobias
Ek, Fredrik
Enqvist, Olof
Olsson, Roger
Åström, Kalle
Petersson, Per
20170609
All motile organisms need to organize their motor output to obtain functional goals. In vertebrates, natural behaviors are generally composed of a relatively large set of motor components which in turn are combined into a rich repertoire of complex actions. It is therefore an experimental challenge to investigate the organizational principles of natural behaviors. Using the relatively simple locomotion pattern of 10 days old zebrafish larvae we have here characterized the basic organizational principles governing the swimming behavior. Our results show that transitions between different behavioral states can be described by a model combining a stochastic component with a control signal. By dividing swimming bouts into a limited number of categories, we show that similar types of swimming behavior as well as standstills between bouts were temporally clustered, indicating a basic level of action sequencing. Finally, we show that pharmacological manipulations known to induce alterations in the organization of motor behavior in mammals, mainly through basal ganglia interactions, have related effects in zebrafish larvae. This latter finding may be of specific relevance to the field of drug development given the growing importance of zebrafish larvae in phenotypic screening for novel drug candidates acting on central nervous system targets.
http://lup.lub.lu.se/record/abd40bf47bf0459fa6ab93fbecf06c7e
http://dx.doi.org/10.1038/s41598017031447
scopus:85020675710
wos:000402957400072
eng
Scientific Reports; 7(1), no 3191 (2017)
ISSN: 20452322
Fysiologi
Journal Article
Action sequencing in the spontaneous swimming behavior of zebrafish larvae  implications for drug development
contributiontojournal/article
info:eurepo/semantics/article
text

Visual Odometry from Two Point Correspondences and Initial Automatic Tilt Calibration
https://lup.lub.lu.se/search/publication/2491a5f4e9eb4834b001078cf51d8a10
Wadenbäck, Mårten
Karlsson, Martin
Heyden, Anders
Robertsson, Anders
Johansson, Rolf
2017
Egomotion estimation is an important step towards fully autonomous mobile robots. In this paper we propose the use of an initial but automatic camera tilt calibration, which transforms the subsequent motion estimation to a 2D rigid body motion problem. This transformed problem is solved 2optimally using RANSAC and a twopoint method for rigid body motion. The method is experimentally evaluated using a camera mounted onto a mobile platform. The results are compared to measurements from a highly accurate external camera positioning system which are used as gold standard. The experiments show promising results on real data. © 2017 by SCITEPRESS  Science and Technology Publications, Lda.
application/pdf
http://lup.lub.lu.se/record/2491a5f4e9eb4834b001078cf51d8a10
http://dx.doi.org/10.5220/0006079903400346
http://lup.lub.lu.se/search/ws/files/26947230/visual_odometry_visapp_2017.pdf
scopus:85047851712
eng
info:eurepo/semantics/openAccess
Matematik
Datorseende och robotik (autonoma system)
Visual Odometry
Tilted Camera
Trajectory Recovery
Visual Odometry from Two Point Correspondences and Initial Automatic Tilt Calibration
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Entropy solutions of a scalar conservation law modeling sedimentation in vessels with varying crosssectional area
https://lup.lub.lu.se/search/publication/a306ae4957ae49c6b34013db551920b6
Bürger, Raimund
Careaga, Julio
Diehl, Stefan
2017
The sedimentation of an ideal suspension in a vessel with variable crosssectional area can be described by an initialboundary value problem for a scalar nonlinear hyperbolic conservation law with a nonconvex flux function and a weight function that depends on spatial position. The sought unknown is the local solids' volume fraction. For the most important cases of vessels with downwarddecreasing crosssectional area and flux functions with at most one infection point, entropy solutions of this problem are constructed by the method of characteristics. Solutions exhibit discontinuities that mostly travel at variable speed, i.e., they are curved in the spacetime plane. These trajectories are given by ordinary differential equations that arise from the jump condition. It is shown that three qualitatively different solutions may occur in dependence of the initial concentration. The potential application of the findings is a new method of flux identification via settling tests in a suitably shaped vessel. Related models also arise in flows of vehicular traffic, pedestrians, in pipes with varying crosssectional area, and on curved surfaces.
http://lup.lub.lu.se/record/a306ae4957ae49c6b34013db551920b6
http://dx.doi.org/10.1137/16M1083177
scopus:85019113706
wos:000402388000011
eng
SIAM Journal on Applied Mathematics; 77(2), pp 789811 (2017)
ISSN: 00361399
Matematik
Conservation law
Method of characteristics
Shock wave
Variable cross section
Entropy solutions of a scalar conservation law modeling sedimentation in vessels with varying crosssectional area
contributiontojournal/article
info:eurepo/semantics/article
text

Fast hyperbolic Radon transform represented as convolutions in logpolar coordinates
https://lup.lub.lu.se/search/publication/b7a08561a9cc4a30a8657ac3d6f6bc05
Nikitin, Viktor V.
Andersson, Fredrik
Carlsson, Marcus
Duchkov, Anton
20170801
The hyperbolic Radon transform is a commonly used tool in seismic processing, for instance in seismic velocity analysis, data interpolation and for multiple removal. A direct implementation by summation of traces with different moveouts is computationally expensive for large data sets. In this paper we present a new method for fast computation of the hyperbolic Radon transforms. It is based on using a logpolar sampling with which the main computational parts reduce to computing convolutions. This allows for fast implementations by means of FFT. In addition to the FFT operations, interpolation procedures are required for switching between coordinates in the timeoffset; Radon; and logpolar domains. Graphical Processor Units (GPUs) are suitable to use as a computational platform for this purpose, due to the hardware supported interpolation routines as well as optimized routines for FFT. Performance tests show large speedups of the proposed algorithm. Hence, it is suitable to use in iterative methods, and we provide examples for data interpolation and multiple removal using this approach.
http://lup.lub.lu.se/record/b7a08561a9cc4a30a8657ac3d6f6bc05
http://dx.doi.org/10.1016/j.cageo.2017.04.013
scopus:85018975523
wos:000404697000003
eng
Computers and Geosciences; 105, pp 2133 (2017)
ISSN: 00983004
Beräkningsmatematik
FFT
GPU
Interpolation
Multiples
Radon transforms
Fast hyperbolic Radon transform represented as convolutions in logpolar coordinates
contributiontojournal/article
info:eurepo/semantics/article
text

Convex envelopes for fixed rank approximation
https://lup.lub.lu.se/search/publication/63bd6d24aaa54f4499d15cf6686b8950
Andersson, Fredrik
Carlsson, Marcus
Olsson, Carl
201712
A convex envelope for the problem of finding the best approximation to a given matrix with a prescribed rank is constructed. This convex envelope allows the usage of traditional optimization techniques when additional constraints are added to the finite rank approximation problem. Expression for the dependence of the convex envelope on the singular values of the given matrix is derived and global minimization properties are derived. The corresponding proximity operator is also studied.
http://lup.lub.lu.se/record/63bd6d24aaa54f4499d15cf6686b8950
http://dx.doi.org/10.1007/s1159001711465
scopus:85018762595
wos:000415197500021
eng
Optimization Letters; 11(8), pp 17831795 (2017)
ISSN: 18624472
Matematik
Approximation
Convex envelope
Proximity operator
Rank constraint
Convex envelopes for fixed rank approximation
contributiontojournal/article
info:eurepo/semantics/article
text

Typical points and families of expanding interval mappings
https://lup.lub.lu.se/search/publication/99aa43bfb6bd42adbac5fc495d50ab73
Persson, Tomas
20170701
We study parametrised families of piecewise expanding interval mappings Ta : [0,1] → [0,1] with absolutely continuous invariant measures μa and give sufficient conditions for a point X(a) to be typical with respect to (Ta; μa) for almost all parameters a. This is similar to a result by D. Schnellmann, but with different assumptions.
http://lup.lub.lu.se/record/99aa43bfb6bd42adbac5fc495d50ab73
http://dx.doi.org/10.3934/dcds.2017170
scopus:85018299833
wos:000401072700020
eng
Discrete and Continuous Dynamical Systems; 37(7), pp 40194034 (2017)
ISSN: 10780947
Matematik
Families of mappings βtransformations
Invariant measures
Piecewise expanding interval mappings
Typical points
Typical points and families of expanding interval mappings
contributiontojournal/article
info:eurepo/semantics/article
text

GroupSparse Regression Using the Covariance Fitting Criterion
https://lup.lub.lu.se/search/publication/ef7c67239eea4b0eaeca9d00be69fc64
Kronvall, Ted
Adalbjörnsson, Stefan Ingi
Nadig, Santhosh
Jakobsson, Andreas
2017
In this work, we present a novel formulation for efficient estimation of groupsparse regression problems. By relaxing a covariance fitting criteria commonly used in array signal processing, we derive a generalization of the recent SPICE method for grouped variables. Such a formulation circumvents cumbersome model order estimation, while being inherently hyperparameterfree. We derive an implementation which iteratively decomposes into a series of convex optimization problems, each being solvable in closedform. Furthermore, we show the connection between the proposed estimator and the class of LASSOtype estimators, where a dictionarydependent regularization level is inherently set by the covariance fitting criteria. We also show how the proposed estimator may be used to form groupsparse estimates for sparse groups, as well as validating its robustness against coherency in the dictionary, i.e., the case of overlapping dictionary groups. Numerical results show preferable estimation performance, on par with a groupLASSO bestowed with oracle regularization, and well exceeding comparable greedy estimation methods.
http://lup.lub.lu.se/record/ef7c67239eea4b0eaeca9d00be69fc64
http://dx.doi.org/10.1016/j.sigpro.2017.03.025
scopus:85018743100
wos:000402214200013
eng
Signal Processing; 139, pp 116130 (2017)
ISSN: 01651684
Signalbehandling
Convex optimization
Covariance fitting
Group sparsity
GroupLASSO
Hyperparameterfree
SPICE
GroupSparse Regression Using the Covariance Fitting Criterion
contributiontojournal/article
info:eurepo/semantics/article
text

On the convergence rate of the DirichletNeumann iteration for unsteady thermal fluid structure interaction
https://lup.lub.lu.se/search/publication/0260cfd227474a38a38bd601979bedb8
Monge, Azahar
Birken, Philipp
2018
We consider the DirichletNeumann iteration for partitioned simulation of thermal fluidstructure interaction, also called conjugate heat transfer. We analyze its convergence rate for two coupled fully discretized 1D linear heat equations with jumps in the material coefficients across these. These are discretized using implicit Euler in time, a finite element method on one domain, a finite volume method on the other one and variable aspect ratio. We provide an exact formula for the spectral radius of the iteration matrix. This shows that for large time steps, the convergence rate is the aspect ratio times the quotient of heat conductivities and that decreasing the time step will improve the convergence rate. Numerical results confirmthe analysis and show that the 1D formula is a good estimator in 2D and even for nonlinear thermal FSI applications.
application/pdf
http://lup.lub.lu.se/record/0260cfd227474a38a38bd601979bedb8
http://dx.doi.org/10.1007/s0046601715113
http://lup.lub.lu.se/search/ws/files/25198795/article17.pdf
scopus:85034740185
eng
info:eurepo/semantics/openAccess
Computational Mechanics; 62(3), pp 525541 (2018)
ISSN: 01787675
Annan maskinteknik
On the convergence rate of the DirichletNeumann iteration for unsteady thermal fluid structure interaction
contributiontojournal/article
info:eurepo/semantics/article
text

Robust Online 3D Reconstruction Combining a Depth Sensor and Sparse Feature Points
https://lup.lub.lu.se/search/publication/052b8cdbedcf42bf8870f54dffc39249
Bylow, Erik
Olsson, Carl
Kahl, Fredrik
20170424
Online 3D reconstruction has been an active research area for a long time. Since the release of the Microsoft Kinect Camera and publication of KinectFusion [11] attention has been drawn how to acquire dense models in realtime. In this paper we present a method to make online 3D reconstruction which increases robustness for scenes with little structure information and little texture information. It is shown empirically that our proposed method also increases robustness when the distance between the camera positions becomes larger than what is commonly assumed. Quantitative and qualitative results suggest that this approach can handle situations where other wellknown methods fail. This is important in, for example, robotics applications like when the camera position and the 3D model must be created online in realtime.
http://lup.lub.lu.se/record/052b8cdbedcf42bf8870f54dffc39249
http://dx.doi.org/10.1109/ICPR.2016.7900211
ISBN: 9781509048472
scopus:85019134505
eng
Matematik
Datorseende och robotik (autonoma system)
Robust Online 3D Reconstruction Combining a Depth Sensor and Sparse Feature Points
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Decreased Diastolic Ventricular Kinetic Energy in Young Patients with Fontan Circulation Demonstrated by FourDimensional Cardiac Magnetic Resonance Imaging
https://lup.lub.lu.se/search/publication/2596035a88d84bbe91df919e2ceef442
Sjöberg, Pia
Heiberg, Einar
Wingren, Pär
Ramgren Johansson, Jens
Malm, Torsten
Arheden, Håkan
Liuba, Petru
Carlsson, Marcus
20170210
Fourdimensional (4D) flow magnetic resonance imaging (MRI) enables quantification of kinetic energy (KE) in intraventricular blood flow. This provides a novel way to understand the cardiovascular physiology of the Fontan circulation. In this study, we aimed to quantify the KE in functional single ventricles. 4D flow MRI was acquired in eleven patients with Fontan circulation (median age 12 years, range 3–29) and eight healthy volunteers (median age 26 years, range 23–36). Followup MRI after surgical or percutaneous intervention was performed in 3 patients. Intraventricular KE was calculated throughout the cardiac cycle and indexed to stroke volume (SV). The systolic/diastolic ratio of KE in Fontan patients was similar to the ratio of the controls’ left ventricle (LV) or right ventricle (RV) depending on the patients’ ventricular morphology (Cohen´s κ = 1.0). Peak systolic KE/SV did not differ in patients compared to the LV in controls (0.016 ± 0.006 mJ/ml vs 0.020 ± 0.004 mJ/ml, p = 0.09). Peak diastolic KE/SV in Fontan patients was lower than in the LV of the control group (0.028 ± 0.010 mJ/ml vs 0.057 ± 0.011 mJ/ml, p < 0.0001). The KE during diastole showed a plateau in patients with aortopulmonary collaterals. This is to our knowledge the first study that quantifies the intraventricular KE of Fontan patients. KE is dependent on the morphology of the ventricle, and diastolic KE indexed to SV in patients is decreased compared to controls. The lower KE in Fontan patients may be a result of impaired ventricular filling.
http://lup.lub.lu.se/record/2596035a88d84bbe91df919e2ceef442
http://dx.doi.org/10.1007/s0024601615656
scopus:85011872817
wos:000399219800005
eng
Pediatric Cardiology; 38(4), pp 669680 (2017)
ISSN: 01720643
Kardiologi
Radiologi och bildbehandling
CMR
Congenital heart disease
Fontan
Kinetic energy
Magnetic resonance imaging
MRI
Decreased Diastolic Ventricular Kinetic Energy in Young Patients with Fontan Circulation Demonstrated by FourDimensional Cardiac Magnetic Resonance Imaging
contributiontojournal/article
info:eurepo/semantics/article
text

On nodal domains in Euclidean balls
https://lup.lub.lu.se/search/publication/a3860d10cb3848548de0474edcfaccc7
Helffer, Bernard
Sundqvist, Mikael Persson
2016
Å. Pleijel (1956) has proved that in the case of the Laplacian with Dirichlet condition, the equality in the Courant nodal theorem (Courant sharp situation) can only be true for a finite number of eigenvalues when the dimension is ≥ 2. Recently Polterovich extended the result to the Neumann problem in two dimensions in the case when the boundary is piecewise analytic. A question coming from the theory of spectral minimal partitions has motivated the analysis of the cases when one has equality in Courant’s theorem. We identify the Courant sharp eigenvalues for the Dirichlet and the Neumann Laplacians in balls in ℝd, d ≥ 2. It is the first result of this type holding in any dimension. The corresponding result for the Dirichlet Laplacian in the disc in ℝ2 was obtained by B. Helffer, T. HoffmannOstenhof and S. Terracini.
http://lup.lub.lu.se/record/a3860d10cb3848548de0474edcfaccc7
http://dx.doi.org/10.1090/proc/13098
scopus:84987842178
wos:000384000300022
eng
Proceedings of the American Mathematical Society; 144(11), pp 47774791 (2016)
ISSN: 00029939
Matematisk analys
Ball
Courant theorem
Dirichlet
Neumann
Nodal domains
On nodal domains in Euclidean balls
contributiontojournal/article
info:eurepo/semantics/article
text

Using Optimal Transport for Estimating Inharmonic Pitch Signals
https://lup.lub.lu.se/search/publication/f27fa31f353c483489dd7f9aec49849d
Elvander, Filip
Adalbjörnsson, Stefan Ingi
Karlsson, Johan
Jakobsson, Andreas
20170619
In this work, we propose a novel multipitch estimation technique that is robust with respect to the inharmonicity commonly occurring in many applications. The method does not require any a priori knowledge of the number of signal sources, the number of harmonics of each source, nor the structure or scope of any possibly occurring inharmonicity. Formulated as a minimum transport distance problem, the proposed method finds an estimate of the present pitches by mapping any found spectral line to the closest harmonic structure. The resulting optimization is a convex and highly tractable linear programming problem. The preferable per formance of the proposed method is illustrated using both simulated and real audio signals.
http://lup.lub.lu.se/record/f27fa31f353c483489dd7f9aec49849d
http://dx.doi.org/10.1109/ICASSP.2017.7952172
scopus:85023779451
eng
Sannolikhetsteori och statistik
Signalbehandling
Using Optimal Transport for Estimating Inharmonic Pitch Signals
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Lieb–Thirring Inequalities for Finite and Infinite Gap Jacobi Matrices
https://lup.lub.lu.se/search/publication/a81fa61516ff4db6ab8a2a81103284f0
Christiansen, Jacob S.
Zinchenko, Maxim
201706
We establish Lieb–Thirring power bounds on discrete eigenvalues of Jacobi operators for Schatten class perturbations under very general assumptions. Our results apply, in particular, to perturbations of reflectionless Jacobi operators with finite gap and Cantortype essential spectrum.
http://lup.lub.lu.se/record/a81fa61516ff4db6ab8a2a81103284f0
http://dx.doi.org/10.1007/s000230160546x
scopus:85009801430
wos:000401325900003
eng
Annales Henri Poincare; 18(6), pp 19491976 (2017)
ISSN: 14240637
Matematik
Lieb–Thirring Inequalities for Finite and Infinite Gap Jacobi Matrices
contributiontojournal/article
info:eurepo/semantics/article
text

Large displacement 3D scene flow with occlusion reasoning
https://lup.lub.lu.se/search/publication/d22596d7d5db4c0db3dd60b7094af553
Zanfir, Andrei
Sminchisescu, Cristian
20160217
The emergence of modern, affordable and accurate RGBD sensors increases the need for single view approaches to estimate 3dimensional motion, also known as scene flow. In this paper we propose a coarsetofine, dense, correspondencebased scene flow formulation that relies on explicit geometric reasoning to account for the effects of large displacements and to model occlusion. Our methodology enforces local motion rigidity at the level of the 3d point cloud without explicitly smoothing the parameters of adjacent neighborhoods. By integrating all geometric and photometric components in a single, consistent, occlusionaware energy model, defined over overlapping, imageadaptive neighborhoods, our method can process fast motions and large occlusions areas, as present in challenging datasets like the MPI Sintel Flow Dataset, recently augmented with depth information. By explicitly modeling large displacements and occlusion, we can handle difficult sequences which cannot be currently processed by state of the art scene flow methods. We also show that by integrating depth information into the model, we can obtain correspondence fields with improved spatial support and sharper boundaries compared to the state of the art, largedisplacement optical flow methods.
http://lup.lub.lu.se/record/d22596d7d5db4c0db3dd60b7094af553
http://dx.doi.org/10.1109/ICCV.2015.502
ISBN: 9781467383912
scopus:84973855972
wos:000380414100494
eng
Datorseende och robotik (autonoma system)
Large displacement 3D scene flow with occlusion reasoning
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Matrix backpropagation for deep networks with structured layers
https://lup.lub.lu.se/search/publication/6cd0105eea6b4c849026e45487668188
Ionescu, Catalin
Vantzos, Orestis
Sminchisescu, Cristian
20160217
Deep neural network architectures have recently produced excellent results in a variety of areas in artificial intelligence and visual recognition, well surpassing traditional shallow architectures trained using handdesigned features. The power of deep networks stems both from their ability to perform local computations followed by pointwise nonlinearities over increasingly larger receptive fields, and from the simplicity and scalability of the gradientdescent training procedure based on backpropagation. An open problem is the inclusion of layers that perform global, structured matrix computations like segmentation (e.g. normalized cuts) or higherorder pooling (e.g. logtangent space metrics defined over the manifold of symmetric positive definite matrices) while preserving the validity and efficiency of an endtoend deep training framework. In this paper we propose a sound mathematical apparatus to formally integrate global structured computation into deep computation architectures. At the heart of our methodology is the development of the theory and practice of backpropagation that generalizes to the calculus of adjoint matrix variations. We perform segmentation experiments using the BSDS and MSCOCO benchmarks and demonstrate that deep networks relying on secondorder pooling and normalized cuts layers, trained endtoend using matrix backpropagation, outperform counterparts that do not take advantage of such global layers.
http://lup.lub.lu.se/record/6cd0105eea6b4c849026e45487668188
http://dx.doi.org/10.1109/ICCV.2015.339
ISBN: 9781467383912
scopus:84973922889
wos:000380414100331
eng
Datorseende och robotik (autonoma system)
Matrix backpropagation for deep networks with structured layers
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Steadystate analyses of activated sludge processes with plugflow reactor
https://lup.lub.lu.se/search/publication/b855bb10508f4a73affc76c3a3691550
Diehl, S.
Zambrano, Jesús
Carlsson, B.
20170201
Activated sludge processes (ASPs) consisting of a plugflow reactor (PFR) and a settler are analyzed in steadystate operation using a reduced model consisting of one soluble substrate and one particulate biomass component modelling the dominating biological process. Monod biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steadystate settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steadystate concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steadystate behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steadystate solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steadystate equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.
http://lup.lub.lu.se/record/b855bb10508f4a73affc76c3a3691550
http://dx.doi.org/10.1016/j.jece.2016.06.038
scopus:85009115689
wos:000398950800081
eng
Journal of Environmental Chemical Engineering; 5(1), pp 795809 (2017)
Vattenteknik
Naturresursteknik
Activated sludge process
BürgerDiehl settler model
Plugflow biological reactor
Secondary clarifier
Solids residence time (SRT)
Steadystate analyses of activated sludge processes with plugflow reactor
contributiontojournal/article
info:eurepo/semantics/article
text

On constitutive functions for hindered settling velocity in 1D settler models : Selection of appropriate model structure
https://lup.lub.lu.se/search/publication/66244af1ebe0495dbbcc741552956d26
Torfs, Elena
Balemans, Sophie
Locatelli, Florent
Diehl, Stefan
Bürger, Raimund
Laurent, Julien
François, Pierre
Nopens, Ingmar
20170301
Advanced 1D models for Secondary Settling Tanks (SSTs) explicitly account for several phenomena that influence the settling process (such as hindered settling and compression settling). For each of these phenomena a valid mathematical expression needs to be selected and its parameters calibrated to obtain a model that can be used for operation and control. This is, however, a challenging task as these phenomena may occur simultaneously. Therefore, the presented work evaluates several available expressions for hindered settling based on longterm batch settling data. Specific attention is paid to the behaviour of these hindered settling functions in the compression region in order to evaluate how the modelling of sludge compression is influenced by the choice of a certain hindered settling function. The analysis shows that the exponential hindered settling forms, which are most commonly used in traditional SST models, not only account for hindered settling but partly lump other phenomena (compression) as well. This makes them unsuitable for advanced 1D models that explicitly include each phenomenon in a modular way. A powerlaw function is shown to be more appropriate to describe the hindered settling velocity in advanced 1D SST models.
http://lup.lub.lu.se/record/66244af1ebe0495dbbcc741552956d26
http://dx.doi.org/10.1016/j.watres.2016.11.067
scopus:85004065487
wos:000394200800004
eng
Water Research; 110, pp 3847 (2017)
ISSN: 00431354
Vattenteknik
1D modelling
Batch settling test
Calibration
Compression settling
Secondary clarifier
On constitutive functions for hindered settling velocity in 1D settler models : Selection of appropriate model structure
contributiontojournal/article
info:eurepo/semantics/article
text

RungeKutta Restarters for Multistep Methods in Presence of Frequent Discontinuities
https://lup.lub.lu.se/search/publication/a8110737d1524ffca79989385f4e0b61
Mohammadi, Fatemeh
Arévalo, Carmen
Führer, Claus
20170515
Differential equations with discontinuities or differential equations coupled to discrete systems require frequent reinitializations of the numerical solution process. The classical starting process of multistep methods, based on increasing the order in the initialization phase, is computationally expensive when frequent discontinuities occur. Instead we propose to use the stage values or weight vectors of these specially constructed explicit Runge–Kutta methods for starting processes. Two practical examples demonstrate these methods.
http://lup.lub.lu.se/record/a8110737d1524ffca79989385f4e0b61
http://dx.doi.org/10.1016/j.cam.2016.09.042
scopus:85006093164
wos:000392784600023
eng
Journal of Computational and Applied Mathematics; 316, pp 287297 (2017)
ISSN: 03770427
Teknik och teknologier
Beräkningsmatematik
Multistep Methods
Error estimation
Runge–Kutta methods
Discontinuities
RungeKutta Restarters for Multistep Methods in Presence of Frequent Discontinuities
contributiontojournal/article
info:eurepo/semantics/article
text

Discretized multilevel elution trajectory: A proofofconcept demonstration
https://lup.lub.lu.se/search/publication/2ee32c3dc82c4cada325ee0ed883c12c
Sellberg, Anton
Holmqvist, Anders
Magnusson, Fredrik
Andersson, Christian
Nilsson, Bernt
20170120
Biomolecular and pharmaceutical downstream processing is dominated by chromatographic separation, which is associated with high product quality, low capacity and high costs. The separation can be optimized to minimize the costs while achieving a high purity. This paper presents an experimental validation of a discretized multilevel elution (DiME) trajectory, implemented on commercially available chromatography equipment. The tertiary protein separation of ribonuclease A, cytochrome C and lysozyme was used as a case study. A mechanistic model was calibrated using step and linear gradient experiments. The model was simulated together with the state sensitivities with respect to model parameters, which was used in the Levenberg–Marquardt algorithm to fit the model response to the experimental data. The model was used to solve the dynamic optimization problem of maximizing the yield of cytochrome C given a 95% purity requirement, 1000 s processing time and 50 salt concentration levels in the elution trajectory. The model was spatially discretized using finite volumes and temporally discretized using direct collocation. The corresponding nonlinear programming problem was solved with IPOPT. Once the optimal salt trajectory was found it was experimentally implemented on an ÄKTA Pure using an OPC interface. The optimal trajectory was analyzed inline by UV absorbance measurements and offline by analysis of collected fractions. The results presented in this study show the successful experimental realization of DiME trajectories and how to use model calibration, optimization and control to realize DiME trajectories for any chromatography separation problem.
http://lup.lub.lu.se/record/2ee32c3dc82c4cada325ee0ed883c12c
http://dx.doi.org/10.1016/j.chroma.2016.12.038
scopus:85009888094
wos:000392681400009
eng
Journal of Chromatography A; 1481, pp 7381 (2017)
ISSN: 00219673
Kemiska processer
Discretized multilevel elution trajectory: A proofofconcept demonstration
contributiontojournal/article
info:eurepo/semantics/article
text

On the semiclassical analysis of the ground state energy of the Dirichlet Pauli operator
https://lup.lub.lu.se/search/publication/7b3e0eae62b4459e8c953e90c218f230
Helffer, Bernard
Persson Sundqvist, Mikael
2017
We complete and improve the results of a recent paper by Ekholm, Kovařík and Portmann in connection with a question of C. Guillarmou about the semiclassical expansion of the lowest eigenvalue of the Pauli operator with Dirichlet conditions. We exhibit connections with the properties of the torsion function in mechanics, the exit time of a Brownian motion and the analysis of the low eigenvalues of some Witten Laplacian.
http://lup.lub.lu.se/record/7b3e0eae62b4459e8c953e90c218f230
http://dx.doi.org/10.1016/j.jmaa.2016.11.058
scopus:85008233263
wos:000393148100007
eng
Journal of Mathematical Analysis and Applications; 449(1), pp 138153 (2017)
ISSN: 0022247X
Matematisk analys
Dirichlet
Pauli operator
Semiclassical
Torsion
On the semiclassical analysis of the ground state energy of the Dirichlet Pauli operator
contributiontojournal/article
info:eurepo/semantics/article
text

Conjugate priors for Gaussian emission plsa recommender systems
https://lup.lub.lu.se/search/publication/39791dc47bc64cbe99ab83ade70ec89b
Adalbjörnsson, Stefan
Swärd, Johan
Berg, Magnus Örn
Andersen, Søren Vang
Jakobsson, Andreas
20161128
Collaborative filtering for recommender systems seeks to learn and predict user preferences for a collection of items by identifying similarities between users on the basis of their past interest or interaction with the items in question. In this work, we present a conjugate prior regularized extension of Hofmann's Gaussian emission probabilistic latent semantic analysis model, able to overcome the overfitting problem restricting the performance of the earlier formulation. Furthermore, in experiments using the EachMovie and MovieLens data sets, it is shown that the proposed regularized model achieves significantly improved prediction accuracy of user preferences as compared to the latent semantic analysis model without priors.
http://lup.lub.lu.se/record/39791dc47bc64cbe99ab83ade70ec89b
http://dx.doi.org/10.1109/EUSIPCO.2016.7760618
ISBN: 9780992862657
scopus:85006073806
eng
Signalbehandling
Sannolikhetsteori och statistik
Collaborative filtering
Probabilistic matrix factorization
Recommender systems
Conjugate priors for Gaussian emission plsa recommender systems
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Multipitch estimation via fast group sparse learning
https://lup.lub.lu.se/search/publication/b0b4b62c08e242c49ed85ed83dd61c3d
Kronvall, Ted
Elvander, Filip
Adalbjörnsson, Stefan Ingi
Jakobsson, Andreas
20161201
In this work, we consider the problem of multipitch estimation using sparse heuristics and convex modeling. In general, this is a difficult nonlinear optimization problem, as the frequencies belonging to one pitch often overlap the frequencies belonging to other pitches, thereby causing ambiguity between pitches with similar frequency content. The problem is further complicated by the fact that the number of pitches is typically not known. In this work, we propose a sparse modeling framework using a generalized chroma representation in order to remove redundancy and lower the dictionary's blockcoherency. The found chroma estimates are then used to solve a small convex problem, whereby spectral smoothness is enforced, resulting in the corresponding pitch estimates. Compared with previously published sparse approaches, the resulting algorithm reduces the computational complexity of each iteration, as well as speeding up the overall convergence.
http://lup.lub.lu.se/record/b0b4b62c08e242c49ed85ed83dd61c3d
http://dx.doi.org/10.1109/EUSIPCO.2016.7760417
ISBN: 9780992862657
scopus:85006008598
eng
European Signal Processing Conference (EUSIPCO); pp 10931097 (2016)
ISSN: 20761465
Signalbehandling
Sannolikhetsteori och statistik
Multipitch estimation via fast group sparse learning
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

On the Structure of Positive SemiDefinite Finite Rank General Domain Hankel and Toeplitz Operators in Several Variables
https://lup.lub.lu.se/search/publication/cdb1c7d9cc8d4567a58184d8d4f19235
Andersson, Fredrik
Carlsson, Marcus
201704
Multivariate versions of the Kronecker theorem in the continuous multivariate setting has recently been published, that characterize the generating functions that give rise to finite rank multidimensional Hankel and Toeplitz type operators defined on general domains. In this paper we study how the additional assumption of positive semidefinite affects the characterization of the corresponding generating functions. We show that these theorems become particularly transparent in the continuous setting, by providing elegant ifandonlyif statements connecting the rank with sums of exponential functions. We also discuss how these operators can be discretized, giving rise to an interesting class of structured matrices that inherit desirable properties from their continuous analogs. In particular we describe how the continuous Kronecker theorem also applies to these structured matrices, given sufficient sampling. We also provide a new proof for the CarathéodoryFejér theorem for block Toeplitz matrices, based on tools from tensor algebra.
http://lup.lub.lu.se/record/cdb1c7d9cc8d4567a58184d8d4f19235
http://dx.doi.org/10.1007/s1178501605966
scopus:84992699610
wos:000398768500003
eng
Complex Analysis and Operator Theory; 11(4), pp 755784 (2017)
ISSN: 16618254
Matematik
CarathéodoryFejér theorem
Finite rank
Hankel
Kronecker theorem
Sums of exponentials
Toeplitz
On the Structure of Positive SemiDefinite Finite Rank General Domain Hankel and Toeplitz Operators in Several Variables
contributiontojournal/article
info:eurepo/semantics/article
text

The influence of magnetic steps on bulk superconductivity
https://lup.lub.lu.se/search/publication/29fca92e56884a588cac87f232599e03
Assaad, Wafaa
Kachmar, Ayman
20161201
We study the distribution of bulk superconductivity in presence of an applied magnetic field, supposed to be a step function, modeled by the GinzburgLandau theory. Our results are valid for the minimizers of the twodimensional GinzburgLandau functional with a large GinzburgLandau parameter and with an applied magnetic field of intensity comparable with the GinzburgLandau parameter.
http://lup.lub.lu.se/record/29fca92e56884a588cac87f232599e03
http://dx.doi.org/10.3934/dcds.2016087
scopus:84992134074
eng
Discrete and Continuous Dynamical Systems; 36(12), pp 66236643 (2016)
ISSN: 10780947
Matematik
GinzburgLandau equation
Magnetic fields
Type II superconductors
The influence of magnetic steps on bulk superconductivity
contributiontojournal/article
info:eurepo/semantics/article
text

Asymptotics of Chebyshev polynomials, I : subsets of R
https://lup.lub.lu.se/search/publication/68bf08f1a9da4d03bd497f218b0f65af
Christiansen, Jacob S.
Simon, Barry
Zinchenko, Maxim
201704
We consider Chebyshev polynomials, (Formula presented.), for infinite, compact sets (Formula presented.) (that is, the monic polynomials minimizing the (Formula presented.)norm, (Formula presented.), on (Formula presented.)). We resolve a (Formula presented.) year old conjecture of Widom that for finite gap subsets of (Formula presented.), his conjectured asymptotics (which we call Szegő–Widom asymptotics) holds. We also prove the first upper bounds of the form (Formula presented.) (where (Formula presented.) is the logarithmic capacity of (Formula presented.)) for a class of (Formula presented.)’s with an infinite number of components, explicitly for those (Formula presented.) that obey a Parreau–Widom condition.
http://lup.lub.lu.se/record/68bf08f1a9da4d03bd497f218b0f65af
http://dx.doi.org/10.1007/s002220160689x
scopus:84988369421
wos:000398170000004
eng
Inventiones Mathematicae; 208(1), pp 217245 (2017)
ISSN: 00209910
Matematik
Asymptotics of Chebyshev polynomials, I : subsets of R
contributiontojournal/article
info:eurepo/semantics/article
text

Recovering Planar Motion from Homographies Obtained using a 2.5Point Solver for a Polynomial System
https://lup.lub.lu.se/search/publication/df237e6f35dd40df8c0d0a293c8f3b2c
Wadenbäck, Mårten
Åström, Karl
Heyden, Anders
20160819
We present a minimal solver for a special kind of homography arising in applications with planar camera motion (e.g. mobile robotics applications). Since the camera motion we consider only has five degrees of freedom, an explicit parametrisation allows us to reduce the required number of point correspondences to 2.5. Using fewer point correspondences is beneficial when used together with RANSAC, but more importantly, the proposed special solver ensures that the estimated homography is of the correct type (in contrast to the DLT, which estimates a general homography). Our method works by enforcing eleven independent polynomial constraints on the elements of this kind of homography matrix, through the framework of the action matrix method for solving polynomial equations. Some analytical investigation using symbolic software has been conducted in order to understand the properties of the polynomial system, and these results have been used to help guide our design of the solver. Additionally, we provide a direct method to recover the sought motion parameters from the homography matrix. We demonstrate that it is possible to recover both the homography and its generating parameters efficiently and accurately.
http://lup.lub.lu.se/record/df237e6f35dd40df8c0d0a293c8f3b2c
http://dx.doi.org/10.1109/ICIP.2016.7532903
ISBN: 9781467399616
scopus:85006705702
eng
Datorseende och robotik (autonoma system)
Robotteknik och automation
Matematik
planar motion
polynomial solver
homography
action matrix
Recovering Planar Motion from Homographies Obtained using a 2.5Point Solver for a Polynomial System
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Structural topology optimization of multibody systems
https://lup.lub.lu.se/search/publication/606829522ffd4b44820cf3072ec90f29
Ghandriz, Toheed
Führer, Claus
Elmqvist, Hilding
20160923
Flexible multibody dynamics (FMD) has found many applications in control, analysis and design of mechanical systems. FMD together with the theory of structural optimization can be used for designing multibody systems with bodies which are lighter, but stronger. Topology optimization of static structures is an active research topic in structural mechanics. However, the extension to the dynamic case is less investigated as one has to face serious numerical difficulties. One way of extending static structural topology optimization to topology optimization of dynamic flexible multibody system with large rotational and transitional motion is investigated in this paper. The optimization can be performed simultaneously on all flexible bodies. The simulation part of optimization is based on an FEM approach together with modal reduction. The resulting nonlinear differentialalgebraic systems are solved with the error controlled integrator IDA (Sundials) wrapped into Python environment by Assimulo (Andersson et al. in Math. Comput. Simul. 116(0):26–43, 2015). A modified formulation of solid isotropic material with penalization (SIMP) method is suggested to avoid numerical instabilities and convergence failures of the optimizer. Sensitivity analysis is central in structural optimization. The sensitivities are approximated to circumvent the expensive calculations. The provided examples show that the method is indeed suitable for optimizing a wide range of multibody systems. Standard SIMP method in structural topology optimization suggests stiffness penalization. To overcome the problem of instabilities and mesh distortion in the dynamic case we consider here additionally element mass penalization.
http://lup.lub.lu.se/record/606829522ffd4b44820cf3072ec90f29
http://dx.doi.org/10.1007/s1104401695427
scopus:84988693272
wos:000390126700009
eng
Multibody System Dynamics; 39(1), pp 135148 (2016)
ISSN: 13845640
Matematik
Flexible multibody dynamics
SIMP
Structural topology optimization
Transient response
Structural topology optimization of multibody systems
contributiontojournal/article
info:eurepo/semantics/article
text

Smartphone Positioning in MultiFloor Environments Without Calibration or Added Infrastructure
https://lup.lub.lu.se/search/publication/54a28c03d39e4836a4aa451d8626c5d6
Burgess, Simon
Åström, Karl
Högström, Mikael
Lindquist, Björn
Ljungberg, Rasmus
20161007
Indoor positioning for smartphone usershas received a lot of attention in recent years. Whilemany solutions have been developed, most rely on aneed for predeployment of infrastructure or collectingground truth data to train on. In this paper we see whatcan be done using existing WiFiinfrastructure andReceived Signal Strength from these to smartphones,not using any calibration of the signal environment ormanually set WiFi positions. We expand on previouswork by using a multifloor model taking into account dampening between floors, and optimize a targetfunction consisting of least squares residuals, to findpositions for WiFis and the smartphone measurementlocations simultaneously. Pressure sensors are used todo floor estimation. The method was tested inside twomultistory buildings, with 5 stories each, with medianerrors of smartphone positions of 12.5m and 16.4m andwith WiFi median position errors of 7.16m and 19.4mrespectively. Correct floor detection was achieved for96% of all smartphone positions.
http://lup.lub.lu.se/record/54a28c03d39e4836a4aa451d8626c5d6
http://dx.doi.org/10.1109/IPIN.2016.7743653
ISBN: 9781509024254
scopus:85004168791
eng
Telekommunikation
Smartphone Positioning in MultiFloor Environments Without Calibration or Added Infrastructure
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Robust TimeofArrival Self Calibration with Missing Data and Outliers
https://lup.lub.lu.se/search/publication/6505724206a7482c8bec0010f5a11197
Batstone, Kenneth John
Oskarsson, Magnus
Åström, Karl
20160902
The problem of estimating receiversender node positionsfrom measured receiversender distances is a key issue indifferent applications such as microphone array calibration, radioantenna array calibration, mapping and positioning using ultrawidebandand mapping and positioning using roundtriptimemeasurements between mobile phones and WiFiunits. Thanks torecent research in this area we have an increased understandingof the geometry of this problem. In this paper, we study theproblem of missing information and the presence of outliers inthe data. We propose a novel hypothesis and test frameworkthat efficiently finds initial estimates of the unknown parametersand combine such methods with optimization techniques toobtain accurate and robust systems. The proposed systems areevaluated against current stateoftheart methods on a large setof benchmark tests. This is evaluated further on WiFi roundtriptime and ultrawideband measurements to give a realisticexample of self calibration for indoor localization.
http://lup.lub.lu.se/record/6505724206a7482c8bec0010f5a11197
http://dx.doi.org/10.1109/EUSIPCO.2016.7760673
ISBN: 9780992862657
scopus:85006056423
eng
Signalbehandling
Robust TimeofArrival Self Calibration with Missing Data and Outliers
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Fast Classification of Empty and Occupied Parking Spaces Using Integral Channel Features
https://lup.lub.lu.se/search/publication/3c98a5ce4f2b4ae8af775767e050bdfe
Ahrnbom, Martin
Åström, Karl
Nilsson, Mikael
20161216
In this paper we present a novel, fast and accurate system for detecting the presence of cars in parking lots. The system is based on fast integral channel features and machine learning. The methods are well suited for running embedded on low performance platforms. The methods are tested on a database of nearly 700,000 images of parking spaces, where 48.5% are occupied and the rest are free. The experimental evaluation shows improved robustness in comparison to the baseline methods for the dataset.
http://lup.lub.lu.se/record/3c98a5ce4f2b4ae8af775767e050bdfe
http://dx.doi.org/10.1109/CVPRW.2016.200
ISBN: 9781467388504
scopus:85010189034
wos:000391572100193
eng
Matematik
Datorseende och robotik (autonoma system)
Fast Classification of Empty and Occupied Parking Spaces Using Integral Channel Features
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Uncovering symmetries in polynomial systems
https://lup.lub.lu.se/search/publication/1506a56cc1654b8889cd9dbfc521c5d5
Larsson, Viktor
Åström, Kalle
2016
In this paper we study symmetries in polynomial equation systems and how they can be integrated into the action matrix method. The main contribution is a generalization of the partial pfold symmetry and we provide new theoretical insights as to why these methods work. We show several examples of how to use this symmetry to construct more compact polynomial solvers. As a second contribution we present a simple and automatic method for finding these symmetries for a given problem. Finally we show two examples where these symmetries occur in real applications.
http://lup.lub.lu.se/record/1506a56cc1654b8889cd9dbfc521c5d5
http://dx.doi.org/10.1007/9783319464879_16
ISBN: 9783319464862
ISBN: 9783319464879
scopus:84990041155
wos:000389384800016
eng
Lecture Notes in Computer Science (LNCS); 9907, pp 252267 (2016)
ISSN: 03029743
ISSN: 16113349
Matematik
Uncovering symmetries in polynomial systems
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Fourier dimension of random images
https://lup.lub.lu.se/search/publication/08c91cf1fc98460ca304893c220edf5a
Ekström, Fredrik
20161001
Given a compact set of real numbers, a random Cm + αdiffeomorphism is constructed such that the image of any measure concentrated on the set and satisfying a certain condition involving a real number s, almost surely has Fourier dimension greater than or equal to s/ (m+ α). This is used to show that every Borel subset of the real numbers of Hausdorff dimension s is Cm + αequivalent to a set of Fourier dimension greater than or equal to s/ (m+ α). In particular every Borel set is diffeomorphic to a Salem set, and the Fourier dimension is not invariant under Cmdiffeomorphisms for any m.
http://lup.lub.lu.se/record/08c91cf1fc98460ca304893c220edf5a
http://dx.doi.org/10.1007/s1151201602373
scopus:84979587640
wos:000384531500011
eng
Arkiv for Matematik; 54(2), pp 455471 (2016)
ISSN: 00042080
Matematik
Fourier dimension of random images
contributiontojournal/article
info:eurepo/semantics/article
text

Secondorder constrained parametric proposals and sequential searchbased structured prediction for semantic segmentation in RGBD images
https://lup.lub.lu.se/search/publication/14ee5cbdf53846098cce4491f15ef696
Banica, Dan
Sminchisescu, Cristian
20151014
We focus on the problem of semantic segmentation based on RGBD data, with emphasis on analyzing cluttered indoor scenes containing many visual categories and instances. Our approach is based on a parametric figureground intensity and depthconstrained proposal process that generates spatial layout hypotheses at multiple locations and scales in the image followed by a sequential inference algorithm that produces a complete scene estimate. Our contributions can be summarized as follows: (1) a generalization of parametric max flow figureground proposal methodology to take advantage of intensity and depth information, in order to systematically and efficiently generate the breakpoints of an underlying spatial model in polynomial time, (2) new region description methods based on secondorder pooling over multiple features constructed using both intensity and depth channels, (3) a principled searchbased structured prediction inference and learning process that resolves conflicts in overlapping spatial partitions and selects regions sequentially towards complete scene estimates, and (4) extensive evaluation of the impact of depth, as well as the effectiveness of a large number of descriptors, both predesigned and automatically obtained using deep learning, in a difficult RGBD semantic segmentation problem with 92 classes. We report state of the art results in the challenging NYU Depth Dataset V2 [44], extended for the RMRC 2013 and RMRC 2014 Indoor Segmentation Challenges, where currently the proposed model ranks first. Moreover, we show that by combining secondorder and deep learning features, over 15% relative accuracy improvements can be additionally achieved. In a scene classification benchmark, our methodology further improves the state of the art by 24%.
http://lup.lub.lu.se/record/14ee5cbdf53846098cce4491f15ef696
http://dx.doi.org/10.1109/CVPR.2015.7298974
ISBN: 9781467369640
scopus:84959216973
eng
Datorseende och robotik (autonoma system)
Secondorder constrained parametric proposals and sequential searchbased structured prediction for semantic segmentation in RGBD images
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

CityScale Localization for Cameras with Known Vertical Direction
https://lup.lub.lu.se/search/publication/13749ab8b71b4184b1d7c5fa5e3bd181
Svärm, Linus
Enqvist, Olof
Kahl, Fredrik
Oskarsson, Magnus
20170701
We consider the problem of localizing a novel image in a large 3D model, given that the gravitational vector is known. In principle, this is just an instance of camera pose estimation, but the scale of the problem introduces some interesting challenges. Most importantly, it makes the correspondence problem very difficult so there will often be a significant number of outliers to handle. To tackle this problem, we use recent theoretical as well as technical advances. Many modern cameras and phones have gravitational sensors that allow us to reduce the search space. Further, there are new techniques to efficiently and reliably deal with extreme rates of outliers. We extend these methods to camera pose estimation by using accurate approximations and fast polynomial solvers. Experimental results are given demonstrating that it is possible to reliably estimate the camera pose despite cases with more than 99% outlier correspondences in cityscale models with several millions of 3D points.
http://lup.lub.lu.se/record/13749ab8b71b4184b1d7c5fa5e3bd181
http://dx.doi.org/10.1109/TPAMI.2016.2598331
scopus:85020387389
wos:000402744400014
eng
IEEE Transactions on Pattern Analysis and Machine Intelligence; 39(7), pp 14551461 (2017)
ISSN: 01628828
Matematik
Datorseende och robotik (autonoma system)
Localization,
Camera Pose
Position Retrieval
CityScale Localization for Cameras with Known Vertical Direction
contributiontojournal/article
info:eurepo/semantics/article
text

Trust No One: Low Rank Matrix Factorization Using Hierarchical RANSAC
https://lup.lub.lu.se/search/publication/7f903c057cc04b659922a65dc6f60e68
Oskarsson, Magnus
Batstone, Kenneth
Åström, Kalle
20160601
In this paper we present a system for performing low rank matrix factorization. Lowrank matrix factorization is an essential problem in many areas including computer vision, with applications in e.g. affine structurefrommotion, photometric stereo, and nonrigid structure from motion. We specifically target structured data patterns, with outliers and large amounts of missing data. Using recently developed characterizations of minimal solutions to matrix factorization problems with missing data, we show how these can be used as building blocks in a hierarchical system that performs bootstrapping on all levels. This gives an robust and fast system, with stateoftheart performance.
http://lup.lub.lu.se/record/7f903c057cc04b659922a65dc6f60e68
scopus:84986309382
eng
Matematik
Datorseende och robotik (autonoma system)
Trust No One: Low Rank Matrix Factorization Using Hierarchical RANSAC
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Feasibility study for the implementation of an automatic system for the detection of social interactions in the waiting area of automatic milking stations by using a video surveillance system
https://lup.lub.lu.se/search/publication/1a3271f70576476aa9fcf7fd8610dc1e
Guzhva, O.
Ardö, H.
Herlin, A.
Nilsson, M.
Åström, K.
Bergsten, C.
20160901
A wellplanned waiting area is crucial for automatic milking systems. In an enclosed waiting area, cows of different rank compete for entering the milking station and they are exposed for a variety of social interactions. Such interactions could increase standing time and delay milking, which may result in stress, lameness, impaired welfare and reduced performance. The aim was to monitor the waiting area in a free stall dairy by the use of three video cameras to detect occurrence of social interactions by using improved image segmentation and tracking methods. The surveillance system observed 252 cows having free access to any of four milking stations during 24 h over a period of two weeks. A twostep pattern recognition approach was used. In the first step geometric features (distances) were extracted from every pair of cows in every frame. These features form the input of the second step. It consists of a classifier of the behaviour of the cows. A support vector machine was used to realise this classifier. The social interactions were identified based on collision of geometrical shapes segmented from the image and positively identified as cows by experienced observers. The results showed that the proposed system was capable of a fairly accurate detection of social interactions.
http://lup.lub.lu.se/record/1a3271f70576476aa9fcf7fd8610dc1e
http://dx.doi.org/10.1016/j.compag.2016.07.010
scopus:84978194426
wos:000383527100050
eng
Computers and Electronics in Agriculture; 127, pp 506509 (2016)
ISSN: 01681699
Matematik
Datorseende och robotik (autonoma system)
Computer vision
Dairy cattle
Object recognition
Precision Livestock Farming
Social interactions
Feasibility study for the implementation of an automatic system for the detection of social interactions in the waiting area of automatic milking stations by using a video surveillance system
contributiontojournal/article
info:eurepo/semantics/article
text

Additive domain decomposition operator splittings – convergence analyses in a dissipative framework
https://lup.lub.lu.se/search/publication/1a867584b8984d44aa15c45f9acf9b79
Hansen, Eskil
Henningsson, Erik
2017
We analyze temporal approximation schemes based on overlapping domain decompositions. As such schemes enable computations on parallel and distributed hardware, they are commonly used when integrating largescale parabolic systems. Our analysis is conducted by first casting the domain decomposition procedure into a variational framework based on weighted Sobolev spaces. The time integration of a parabolic system can then be interpreted as an operator splitting scheme applied to an abstract evolution equation governed by a maximal dissipative vector field. By utilizing this abstract setting, we derive an optimal temporal error analysis for the two most common choices of domain decomposition based integrators. Namely, alternating direction implicit schemes and additive splitting schemes of first and second order. For the standard firstorder additive splitting scheme we also extend the error analysis to semilinear evolution equations, which may only have mild solutions. The theoretical results are finally illustrated by numerical experiments.
http://lup.lub.lu.se/record/1a867584b8984d44aa15c45f9acf9b79
http://dx.doi.org/10.1093/imanum/drw043
wos:000405416900016
scopus:85019518727
eng
IMA Journal of Numerical Analysis; 37(3), pp 14961519 (2017)
ISSN: 14643642
Beräkningsmatematik
domain decomposition
convergence order
additive splitting schemes
alternating direction implicit schemes
parabolic equations
semilinear evolution equations
Additive domain decomposition operator splittings – convergence analyses in a dissipative framework
contributiontojournal/article
info:eurepo/semantics/article
text

A comparison of Rosenbrock and ESDIRK methods combined with iterative solvers for unsteady compressible flows
https://lup.lub.lu.se/search/publication/046e254068a04ba8bddc2f88ba9f79e4
Blom, David S.
Birken, Philipp
Bijl, Hester
Kessels, Fleur
Meister, Andreas
van Zuijlen, Alexander H.
201612
In this article, we endeavour to find a fast solver for finite volume discretizations for compressible unsteady viscous flows. Thereby, we concentrate on comparing the efficiency of important classes of time integration schemes, namely time adaptive Rosenbrock, singly diagonally implicit (SDIRK) and explicit first stage singly diagonally implicit RungeKutta (ESDIRK) methods. To make the comparison fair, efficient equation system solvers need to be chosen and a smart choice of tolerances is needed. This is determined from the tolerance TOL that steers time adaptivity. For implicit RungeKutta methods, the solver is given by preconditioned inexact Jacobianfree NewtonKrylov (JFNK) and for Rosenbrock, it is preconditioned Jacobianfree GMRES. To specify the tolerances in there, we suggest a simple strategy of using TOL/100 that is a good compromise between stability and computational effort. Numerical experiments for different test cases show that the fourth order Rosenbrock method RODASP and the fourth order ESDIRK method ESDIRK4 are best for fine tolerances, with RODASP being the most robust scheme.
http://lup.lub.lu.se/record/046e254068a04ba8bddc2f88ba9f79e4
http://dx.doi.org/10.1007/s104440169468x
scopus:84978032472
wos:000388179700007
eng
Advances in Computational Mathematics; 42(6), pp 14011426 (2016)
ISSN: 15729044
Beräkningsmatematik
Rosenbrock methods
NavierStokes equations
ESDIRK
Jacobianfree NewtonKrylov
Unsteady flows
Time adaptivity
A comparison of Rosenbrock and ESDIRK methods combined with iterative solvers for unsteady compressible flows
contributiontojournal/article
info:eurepo/semantics/article
text

Identification of ETV6RUNX1like and DUX4rearranged subtypes in paediatric Bcell precursor acute lymphoblastic leukaemia
https://lup.lub.lu.se/search/publication/cdebe51384d8452183178265a856617a
Lilljebjörn, Henrik
Henningsson, Rasmus
HyreniusWittsten, Axel
Olsson, Linda
OrsmarkPietras, Christina
Von Palffy, Sofia
Askmyr, Maria
Rissler, Marianne
Schrappe, Martin
Cario, Gunnar
Castor, Anders
Pronk, KeesJan
Behrendtz, Mikael
Mitelman, Felix
Johansson, Bertil
Paulsson, Kajsa
Andersson, Anna K.
Fontes, Magnus
Fioretos, Thoas
20160606
Fusion genes are potent driver mutations in cancer. In this study, we delineate the fusion gene landscape in a consecutive series of 195 paediatric Bcell precursor acute lymphoblastic leukaemia (BCP ALL). Using RNA sequencing, we find inframe fusion genes in 127 (65%) cases, including 27 novel fusions. We describe a subtype characterized by recurrent IGHDUX4 or ERGDUX4 fusions, representing 4% of cases, leading to overexpression of DUX4 and frequently cooccurring with intragenic ERG deletions. Furthermore, we identify a subtype characterized by an ETV6RUNX1like geneexpression profile and coexisting ETV6 and IKZF1 alterations. Thus, this study provides a detailed overview of fusion genes in paediatric BCP ALL and adds new pathogenetic insights, which may improve risk stratification and provide therapeutic options for this disease.
http://lup.lub.lu.se/record/cdebe51384d8452183178265a856617a
http://dx.doi.org/10.1038/ncomms11790
scopus:84973305001
wos:000377384300001
eng
Nature Communications; 7, no 11790 (2016)
ISSN: 20411723
Medicinsk genetik
Identification of ETV6RUNX1like and DUX4rearranged subtypes in paediatric Bcell precursor acute lymphoblastic leukaemia
contributiontojournal/article
info:eurepo/semantics/article
text

Fast Algorithms and Efficient GPU Implementations for the Radon Transform and the BackProjection Operator Represented as Convolution Operators
https://lup.lub.lu.se/search/publication/454d9aeb79284cb7b9783836a2fa9f14
Nikitin, Viktor
Andersson, Fredrik
Carlsson, Marcus
20160510
The Radon transform and its adjoint, the backprojection operator, can both be expressed as convolutions in logpolar coordinates. Hence, fast algorithms for the application of these operators can be constructed by using FFT, if data is resampled at logpolar coordinates. Radon data is typically measured on an equally spaced grid in polar coordinates, and reconstructions are represented (as images) in Cartesian coordinates. Therefore, in addition to FFT, several steps of interpolation have to be conducted in order to apply the Radon transform and the backprojection operator by means of convolutions. However, in comparison to the interpolation conducted in Fourierbased gridding methods, the interpolation performed in the Radon and image domains will typically deal with functions that are substantially less oscillatory. Reasonable reconstruction results can thus be expected using interpolation schemes of moderate order. It also provides better control over the artifacts that can appear due to measurement errors.Both the interpolation and the FFT operations can be efficiently implemented on Graphical Processor Units (GPUs). For the interpolation, it is possible to make use of the fact that linear interpolation is hardwired on GPUs, meaning that it has the same computational cost as direct memory access. Cubic order interpolation schemes can be constructed by combining linear interpolation steps and this provides important computation speedup.We provide details about how the Radon transform and the backprojection can be implemented efficiently as convolution operators on GPUs. For large data sizes, these algorithms are several times faster than those of other software packages based on GPU implementations of the Radon transform and the backprojection operator. Moreover, the gain in computational speed is substantially higher when comparing against other CPU based algorithms.
http://lup.lub.lu.se/record/454d9aeb79284cb7b9783836a2fa9f14
http://dx.doi.org/10.1137/15M1023762
scopus:84976621336
wos:000385275400006
eng
SIAM Journal of Imaging Sciences; 9(2), pp 637664 (2016)
ISSN: 19364954
Matematik
Fast Algorithms and Efficient GPU Implementations for the Radon Transform and the BackProjection Operator Represented as Convolution Operators
contributiontojournal/article
info:eurepo/semantics/article
text

Towards Grading Gleason Score using Generically Trained Deep convolutional Neural Networks
https://lup.lub.lu.se/search/publication/839c04b4164c414586209a6f2e5139c4
Källén, Hanna
Molin, Jesper
Heyden, Anders
Lundström, Claes
Åström, Karl
2016
We developed an automatic algorithm with the purpose to assist pathologists to report Gleason score on malignant prostatic adenocarcinoma specimen. In order to detect and classify the cancerous tissue, a deep convolutional neural network that had been pretrained on a large set of photographic images was used. A specific aim was to support intuitive interaction with the result, to let pathologists adjust and correct the output. Therefore, we have designed an algorithm that makes a spatial classification of the whole slide into the same growth patterns as pathologists do. The 22layer network was cut at an earlier layer and the output from that layer was used to train both a random forest classifier and a support vector machines classifier. At a specific layer a small patch of the image was used to calculate a feature vector and an image is represented by a number of those vectors. We have classified both the individual patches and the entire images. The classification results were compared for different scales of the images and feature vectors from two different layers from the network. Testing was made on a dataset consisting of 213 images, all containing a single class, benign tissue or Gleason score 35. Using 10fold cross validation the accuracy per patch was 81 %. For whole images, the accuracy was increased to 89 %.
application/pdf
http://lup.lub.lu.se/record/839c04b4164c414586209a6f2e5139c4
http://dx.doi.org/10.1109/ISBI.2016.7493473
ISBN: 9781479923496
http://lup.lub.lu.se/search/ws/files/8106067/ISBI2016_prostata.pdf
scopus:84978387816
wos:000386377400275
eng
info:eurepo/semantics/openAccess
Matematik
Datorseende och robotik (autonoma system)
Prostate Cancer
Gleason Score
Deep Learning
Convolutional Neural Networks
Towards Grading Gleason Score using Generically Trained Deep convolutional Neural Networks
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Efficient simulations of tubulindriven axonal growth
https://lup.lub.lu.se/search/publication/f50c6428f0a54f91bde3f332753fe894
Diehl, Stefan
Henningsson, Erik
Heyden, Anders
201608
This work concerns efficient and reliable numerical simulations of the dynamic behaviour of a movingboundary model for tubulindriven axonal growth. The model is nonlinear and consists of a coupled set of a partial differential equation (PDE) and two ordinary differential equations. The PDE is defined on a computational domain with a moving boundary, which is part of the solution. Numerical simulations based on standard explicit timestepping methods are too time consuming due to the small time steps required for numerical stability. On the other hand standard implicit schemes are too complex due to the nonlinear equations that needs to be solved in each step. Instead, we propose to use the Peaceman–Rachford splitting scheme combined with temporal and spatial scalings of the model. Simulations based on this scheme have shown to be efficient, accurate, and reliable which makes it possible to evaluate the model, e.g. its dependency on biological and physical model parameters. These evaluations show among other things that the initial axon growth is very fast, that the active transport is the dominant reason over diffusion for the growth velocity, and that the polymerization rate in the growth cone does not affect the final axon length.
http://lup.lub.lu.se/record/f50c6428f0a54f91bde3f332753fe894
http://dx.doi.org/10.1007/s108270160604x
scopus:84977079437
wos:000379186900004
eng
Journal of Computational Neuroscience; 41(1), pp 4563 (2016)
ISSN: 15736873
Beräkningsmatematik
Neurovetenskaper
Neurite elongation
Partial differential equation
Numerical simulation
Peaceman–Rachford splitting scheme
Polymerization
Microtubule cytoskeleton
Efficient simulations of tubulindriven axonal growth
contributiontojournal/article
info:eurepo/semantics/article
text

Multifractal analysis of some multiple ergodic averages
https://lup.lub.lu.se/search/publication/b8135123179944abb2c544e0a702e245
Fan, Ai Hua
Schmeling, Jörg
Wu, Meng
20160604
In this paper we study the multiple ergodic averages, on the symbolic space σm = (0,1,...,m1}N* where m≥ 2, ℓ ≥ 2, q≥ 2 are integers. We give a complete solution to the problem of multifractal analysis of the limit of the above multiple ergodic averages. Actually we develop a noninvariant and nonlinear version of thermodynamic formalism that is of its own interest. We study a large class of measures (called telescopic product measures). The special case of telescopic product measures defined by the fixed points of some nonlinear transfer operators plays a crucial role in studying the level sets of the limit, which are not shiftinvariant. These measures share many properties with Gibbs measures in the classical thermodynamic formalism. Our work also concerns variational principle, pressure function and Legendre transform in this new setting.
http://lup.lub.lu.se/record/b8135123179944abb2c544e0a702e245
http://dx.doi.org/10.1016/j.aim.2016.03.012
scopus:84962228302
wos:000376472400007
eng
Advances in Mathematics; 295, pp 271333 (2016)
ISSN: 00018708
Matematisk analys
Hausdorff dimension
Multifractal
Multiple ergodic average
Multifractal analysis of some multiple ergodic averages
contributiontojournal/article
info:eurepo/semantics/article
text

On shrinking targets for piecewise expanding interval maps
https://lup.lub.lu.se/search/publication/226c637a1f434ba3b93eca64c828088f
Persson, Tomas
RAMS, MICHAŁ
201704
For a map (Formula presented.) with an invariant measure (Formula presented.), we study, for a (Formula presented.)typical (Formula presented.), the set of points (Formula presented.) such that the inequality (Formula presented.) is satisfied for infinitely many (Formula presented.). We give a formula for the Hausdorff dimension of this set, under the assumption that (Formula presented.) is piecewise expanding and (Formula presented.) is a Gibbs measure. In some cases we also show that the set has a large intersection property.
http://lup.lub.lu.se/record/226c637a1f434ba3b93eca64c828088f
http://dx.doi.org/10.1017/etds.2015.49
scopus:84940068591
wos:000395899300015
eng
Ergodic Theory and Dynamical Systems; 37(02), pp 646663 (2017)
ISSN: 01433857
Matematik
On shrinking targets for piecewise expanding interval maps
contributiontojournal/article
info:eurepo/semantics/article
text

Recent Developments on Direct Relative Orientation
https://lup.lub.lu.se/search/publication/a60a4feefc504e13b66866bcc618e580
Stewenius, Henrik
Engels, Christopher
Nistér, David
2006
http://lup.lub.lu.se/record/788338
scopus:33744544949
eng
ISPRS Journal of Photogrammetry and Remote Sensing; 60(4), pp 284294 (2006)
ISSN: 09242716
Matematik
Sixpoint method
Relative orientation
Fivepoint method
Gröbner basis
Recent Developments on Direct Relative Orientation
contributiontojournal/article
info:eurepo/semantics/article
text

Using Conic Correspondences in Two Images to Estimate the Epipolar Geometry
https://lup.lub.lu.se/search/publication/9660bbf5de1e46839760ca06520c5212
Kahl, Fredrik
Heyden, Anders
1998
In this paper it is shown hour corresponding conics in two images can be used to estimate the epipolar geometry in terms of the fundamental/essential matrix. The corresponding conics can, be images of either planar celtics or silhouettes of quadrics. It is shown that one conic correspondence gives two independent constraints on the fundamental matrix and a method to estimate the fundamental matrix from at least four corresponding conics is presented. Furthermore, a new type of fundamental matrix for describing conic correspondences is introduced. Finally, it is shown that the problem of estimating the fundamental matrix from 5 point correspondences and 1 conic correspondence in general has 10 different solutions. A method to calculate these solutions is also given together with an experimental validation
http://lup.lub.lu.se/record/787366
http://dx.doi.org/10.1109/ICCV.1998.710803
ISBN: 81 7319 221 9
scopus:0032309499
eng
Matematik
computational geometry
computer vision
motion estimation
conic correspondences
epipolar geometry
image estimation
planar celtics
silhouettes
quadrics
fundamental matrix
Using Conic Correspondences in Two Images to Estimate the Epipolar Geometry
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Many body problems with ``spin''related contact interactions
https://lup.lub.lu.se/search/publication/9aba4948dcc148489591f27e9df7b38f
Albeverio, Sergio
Fei, ShaoMing
Kurasov, Pavel
2001
http://lup.lub.lu.se/record/758096
scopus:0042964911
eng
Reports in Math. Physics; 47(2), pp 157165 (2001)
Matematik
Many body problems with ``spin''related contact interactions
contributiontojournal/article
info:eurepo/semantics/article
text

Tracking and positioning using phase information from estimated multipath components
https://lup.lub.lu.se/search/publication/b7aa1925bc8e431fba67ce5bbaa8875a
Zhu, Meifang
Vieira, Joao
Kuang, Yubin
Åström, Karl
Molisch, Andreas
Tufvesson, Fredrik
2015
High resolution radio based positioning and tracking is a key enabler for new or improved cellular services. In this work, we are aiming to track user movements with accuracy down to centimeters using standard cellular bandwidths of 2040 MHz. The goal is achieved by using phase information from the multipath components (MPCs) of the radio channels. First, an extended Kalman filter (EKF) is used to estimate and track the phase information of the MPCs. Each of the tracked MPCs can be seen as originating from a virtual transmitter at an unknown position. By using a time difference of arrival (TDOA) positioning algorithm based on a structureofmotion approach and translating the tracked phase information into propagation distances, the user movements can be estimated with a standard deviation of the error of 4.0 cm. The paper should be viewed as a proofofprinciple and it is shown by measurements that phase based positioning can be a promising solution for movement tracking in cellular systems with extraordinary accuracy.
application/pdf
http://lup.lub.lu.se/record/7373465
http://lup.lub.lu.se/search/ws/files/6072560/7373469.pdf
scopus:84947785323
eng
info:eurepo/semantics/openAccess
Elektroteknik och elektronik
Tracking and positioning using phase information from estimated multipath components
contributiontoconference/paper
info:eurepo/semantics/conferenceObject
text

Rank one perturbations, approximations and selfadjoint extensions
https://lup.lub.lu.se/search/publication/29aae1ea07e64b64a3406037a42041d2
Albeverio, Sergio
Kurasov, Pavel
1997
http://lup.lub.lu.se/record/758074
scopus:0031212486
eng
J. Func. Anal.; 148, pp 152169 (1997)
Matematik
Rank one perturbations, approximations and selfadjoint extensions
contributiontojournal/article
info:eurepo/semantics/article
text

Globally Optimal Estimates for Geometric Reconstruction Problems
https://lup.lub.lu.se/search/publication/a1dbdea4f8a54aec866f9c72c987e463
Kahl, Fredrik
Henrion, Didier
2005
http://lup.lub.lu.se/record/787874
scopus:33745842405
eng
Matematik
Globally Optimal Estimates for Geometric Reconstruction Problems
contributiontoconference/paper
info:eurepo/semantics/conferenceObject
text

How hard is 3view triangulation really?
https://lup.lub.lu.se/search/publication/e68f971be24e4a9689f1ac6be6117236
Stewenius, Henrik
Schaffalitzky, F
Nister, D
2005
We present a solution for optimal triangulation in three views. The solution is guaranteed to find the optimal solution because it computes all the stationary points of the (maximum likelihood) objective function. Internally, the solution is found by computing roots of multivariate polynomial equations, directly solving the conditions for stationarity. The solver makes use of standard methods from computational commutative algebra to convert the rootfinding problem into a 47
http://lup.lub.lu.se/record/616506
http://dx.doi.org/10.1109/ICCV.2005.115
ISBN: 076952334X
wos:000233155100089
scopus:33745968244
eng
Matematik
scene geometry
image motion analysis
nonsymmetric eigenproblem
rootfinding problem
computational commutative algebra
multivariate polynomial equation
maximum likelihood objective function
3view triangulation
optimal triangulation
How hard is 3view triangulation really?
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Multilinear Constraints in the Infinitesimaltime Case
https://lup.lub.lu.se/search/publication/0cd9fffeceb144b7a46149ebc7d4cc6f
Åström, Karl
Heyden, Anders
1996
In this paper we study the infinitesimaltime case of the so called multilinear constraints that exist for each subsequence in a sequence of images. These constraints link the infinitesimal motion of the image points with the infinitesimal viewer motion. The analysis is done both for calibrated and uncalibrated cameras. Two simplifications are also presented for the uncalibrated camera case. One simplification is made using affine reduction and kinetic depth. The second simplification is based upon a projective reduction with respect to the image of a planar patch
http://lup.lub.lu.se/record/787300
http://dx.doi.org/10.1109/CVPR.1996.517168
ISBN: 0 8186 7258 7
scopus:0029711434
eng
Matematik
image sequences
motion estimation
Multilinear Constraints in the Infinitesimaltime Case
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Revisiting the PnP Problem: A Fast, General and Optimal Solution
https://lup.lub.lu.se/search/publication/796e79a41c654d8f9bc9e329b47e65a4
Zheng, Yinqiang
Kuang, Yubin
Sugimoto, Shigeki
Åström, Karl
Okutomi, Masatoshi
2013
In this paper, we revisit the classical perspectivenpoint (PnP) problem, and propose the first noniterative O(n) solution that is fast, generally applicable and globally optimal. Our basic idea is to formulate the PnP problem into a functional minimization problem and retrieve all its stationary points by using the Gr¨obner basis technique. The novelty lies in a nonunit quaternion representation to parameterize the rotation and a simple but elegant formulation of the PnP problem into an unconstrained optimization problem. Interestingly, the polynomial system arising from its firstorder optimality condition assumes twofold symmetry, a nice property that can be utilized to improve speed and numerical stability of a Gr¨obner basis solver. Experiment results have demonstrated that, in terms of accuracy, our proposed solution is definitely better than the stateofthe art O(n) methods, and even comparable with the reprojection error minimization method.
application/pdf
http://lup.lub.lu.se/record/4249625
scopus:84898785848
eng
info:eurepo/semantics/restrictedAccess
Matematik
computer vision
pose
pnp
Revisiting the PnP Problem: A Fast, General and Optimal Solution
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Euclidean Reconstruction from Constant Intrinsic Parameters
https://lup.lub.lu.se/search/publication/400d4984295743f79bf31c2ed237b88a
Heyden, Anders
Åström, Karl
1996
A new method for Euclidean reconstruction from sequences of images taken by uncalibrated cameras, with constant intrinsic parameters, is described. Our approach leads to a variant of the so called Kruppa equations. It is shown that it is possible to calculate the intrinsic parameters as well as the Euclidean reconstruction from at least three images. The novelty of our approach is that we build our calculation on a projective reconstruction obtained without the assumption on constant intrinsic parameters. This assumption simplifies the analysis, because a projective reconstruction is already obtained and we need “only” to find the correct Euclidean reconstruction among all possible projective reconstructions
http://lup.lub.lu.se/record/787294
http://dx.doi.org/10.1109/ICPR.1996.546045
ISBN: 0 8186 7282 X
scopus:84898834635
eng
Matematik
image reconstruction
image sequences
matrix algebra
Euclidean Reconstruction from Constant Intrinsic Parameters
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Improving Robustness for InterSubject Medical Image Registration Using a FeatureBased Approach
https://lup.lub.lu.se/search/publication/ea7c6a4d108442d9bfa2de648162e08c
Svärm, Linus
Enqvist, Olof
Kahl, Fredrik
Oskarsson, Magnus
2015
We propose new featurebased methods for rigid and affine image registration. These are compared to stateoftheart intensitybased techniques as well as existing featurebased methods. On challenging datasets of brain MR and wholebody CT images, a significant improvement in terms of speed, robustness to outlier structures and dependence on initialization is shown.
http://lup.lub.lu.se/record/8519275
http://dx.doi.org/10.1109/ISBI.2015.7163998
scopus:84944322842
eng
Medicinsk bioteknik
Matematik
Computer vision
image registration
medical image analysis
optimization
Improving Robustness for InterSubject Medical Image Registration Using a FeatureBased Approach
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Practical Robust TwoView Translation Estimation
https://lup.lub.lu.se/search/publication/a68dd0a6edd34f92af85683396b0c302
Fredriksson, Johan
Larsson, Viktor
Olsson, Carl
2015
Outliers pose a problem in all real structure from motion
systems. Due to the use of automatic matching methods
one has to expect that a (sometimes very large) portion of
the detected correspondences can be incorrect. In this paper
we propose a method that estimates the relative translation
between two cameras and simultaneously maximizes
the number of inlier correspondences.
Traditionally, outlier removal tasks have been addressed
using RANSAC approaches. However, these are random in
nature and offer no guarantees of finding a good solution.
If the amount of mismatches is large, the approach becomes
costly because of the need to evaluate a large number of
random samples. In contrast, our approach is based on the
branch and bound methodology which guarantees that an
optimal solution will be found. While most optimal methods
trade speed for optimality, the proposed algorithm has competitive
running times on problem sizes well beyond what is
common in practice. Experiments on both real and synthetic
data show that the method outperforms stateoftheart alternatives,
including RANSAC, in terms of solution quality.
In addition, the approach is shown to be faster than
RANSAC in settings with a large amount of outliers.
application/pdf
http://lup.lub.lu.se/record/5276657
http://dx.doi.org/10.1109/CVPR.2015.7298884
ISBN: 9781467369640
http://lup.lub.lu.se/search/ws/files/5646111/5276663.pdf
scopus:84959249513
eng
info:eurepo/semantics/openAccess
Matematik
Datorseende och robotik (autonoma system)
Twoview estimation
computer vision
optimization
Practical Robust TwoView Translation Estimation
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Stochastic Modelling and Analysis of Subpixel Edge Detection
https://lup.lub.lu.se/search/publication/268242d8dfd04e7a9a9d22dd84cb21d4
Åström, Karl
Heyden, Anders
1996
Stochastic analysis of edge detectors can be made either by theoretical modeling of the image formation process and the edge detectors or by empirical stochastic analysis of the edge locations. In this paper we study and model the image formation process in detail. In particular the much neglected discretisation process is modelled and taken into account. This makes it possible to define and analyse subpixel edge detection. The theoretical results are verified through stochastic analysis of both simulated and real image data
http://lup.lub.lu.se/record/787636
http://dx.doi.org/10.1109/ICPR.1996.546729
ISBN: 0 8186 7282 X
scopus:0007121109
eng
Matematik
computer vision
edge detection
interpolation
modelling
smoothing methods
statistical analysis
stochastic processes
Stochastic Modelling and Analysis of Subpixel Edge Detection
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Generalised Epipolar Constraints
https://lup.lub.lu.se/search/publication/b09d30244c244e8ea45c1c186c01c0c0
Åström, Karl
Cipolla, R.
Giblin, P. J.
1996
http://lup.lub.lu.se/record/787186
scopus:84957882786
eng
Matematik
Generalised Epipolar Constraints
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Multiview reconstruction of space curves
https://lup.lub.lu.se/search/publication/f8c385245f9c4d839fd71ce679bffe87
Kahl, Fredrik
August, Jonas
2003
Is the real problem in resolving correspondence using current stereo algorithms the lack of the "right" matching criterion? In studying the related task of reconstructing threedimensional space curves from their projections in multiple views, we suggest that the problem is more basic: matching and reconstruction are coupled, and so reconstruction algorithms should exploit ths rather than assuming that matching can be successfully performed before reconstruction. To realize this coupling, a generative model of curves is introduced which has two key components: (i) a prior distribution of general space curves and (ii) an image formation model whch discribes how 3D curves are projected onto the image plane. A novel aspect of the image formation model is that it uses an exact description of the gradient field of a piecewise constant image. Based on this forward model, a fully automatic algorithm for solving the inverse problem is developed for an arbitrary number of views. The resulting algorithm is robust to partial occlusion, deficiencies in image curve extraction and it does not rely on photometric information. The relative motion of the cameras is assumed to be given. Several experiments are carried out on various realistic scenarios. In particular, we focus on scenes where traditional correlationbased methods would fail.
http://lup.lub.lu.se/record/611933
http://dx.doi.org/10.1109/ICCV.2003.1238461
wos:000186833000135
other:CODEN: PICVES
scopus:0344120679
eng
Matematik
Stereo algorithms
Piecewise constant image
Curve extraction
Multiview reconstruction of space curves
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Simultaneous Reconstruction of Scene Structure and Camera Locations from Uncalibrated Image Sequences
https://lup.lub.lu.se/search/publication/4f49b101bd7e4bb49e5476745632c1ff
Sparr, Gunnar
1996
The paper deals with the structuremotion problem for images of point configurations taken by uncalibrated cameras. Using a parametrisation by affine shape and kinetic depth, a complete and explicit characterisation of the imaging geometry is given, including the shape of the object configuration and the positions of the cameras relative to the scene. No epipolar geometry is used. It is shown that not only the projective but also the affine structure of the scene can be recovered when knowing the relative placement of five of the camera centres (four if they are coplanar). Variational algorithms for reconstruction and motion are presented, thus avoiding numerically unstable solving of algebraic equations. Any number of points in any number of images can be treated simultaneously and uniformly, without preselection of reference points. The performances of the algorithms are illustrated on simulations and experiments
http://lup.lub.lu.se/record/787499
http://dx.doi.org/10.1109/ICPR.1996.546043
ISBN: 0 8186 7282 X
scopus:84898834959
eng
Matematik
computational geometry  computer vision  image reconstruction  image sequences  motion estimation  variational techniques
scene structure reconstruction  camera locations  uncalibrated image sequences  structuremotion  parametrisation  kinetic depth  imaging geometry  image recovery  camera centres  variational algorithms  structure motion analysis
Simultaneous Reconstruction of Scene Structure and Camera Locations from Uncalibrated Image Sequences
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Transcriptional regulation of aquaporins in accessions of Arabidopsis in response to drought stress.
https://lup.lub.lu.se/search/publication/2dc75bcd3b3b425b855bc0fcddbcc674
Alexandersson, Erik
Danielson, Jonas
Råde, Johan
Moparthi, Vamsi
Fontes, Magnus
Kjellbom, Per
Johanson, Urban
2010
Summary Aquaporins facilitate water transport over cellular membranes and are therefore believed to play an important role in water homeostasis. In higher plants aquaporinlike proteins, also called major intrinsic proteins (MIPs), are divided into 5 subfamilies. We have previously shown that MIP transcription in Arabidopsis thaliana generally is downregulated in leaves upon drought stress, apart from two members of the Plasma membrane Intrinsic Protein (PIP) subfamily, AtPIP1;4 and AtPIP2;5, which are upregulated. In order to assess if this regulation is general or accessionspecific we monitored gene expression of all PIPs in five Arabidopsis accessions. Overall drought regulation of PIPs was well conserved for all five accessions tested suggesting a general and fundamental physiological role of this drought response. In addition, significant differences among accessions were identified for transcripts of three PIP genes. Principal component analysis showed that most of the PIP transcriptional variation during drought stress could be explained by one variable linked to leaf water content. PromoterGUS constructs of AtPIP1;4, AtPIP2;5 and also AtPIP2;6, which is unresponsive to drought stress, had distinct expression patterns concentrated to the base of the leaf petioles and parts of the flowers. The presence of drought stress response elements within the 1.6 kb promoter regions of AtPIP1;4 and AtPIP2;5, was demonstrated by comparing transcription of the promoter reporter construct and the endogenous gene upon drought stress. Analysis by ATTEDII and other webbased bioinformatical tools showed that several of the MIPs downregulated upon drought are strongly coexpressed, whereas AtPIP1;4, AtPIP2;5 and AtPIP2;6 are not coexpressed.
http://lup.lub.lu.se/record/1524172
http://dx.doi.org/10.1111/j.1365313X.2009.04087.x
wos:000274336900010
pmid:19947979
scopus:76449084321
eng
Plant Journal; 61, pp 650660 (2010)
ISSN: 1365313X
Matematik
Datorseende och robotik (autonoma system)
Biologiska vetenskaper
Transcriptional regulation of aquaporins in accessions of Arabidopsis in response to drought stress.
contributiontojournal/article
info:eurepo/semantics/article
text

Distribution theory for discontinuous test functions and differential operators with generalized coefficients
https://lup.lub.lu.se/search/publication/8d21f46af31543daa5a7f0962302aedf
Kurasov, Pavel
1996
Investigation of the differential operators with the generalized coefficients having singular support on a disjoint set of points requires the consideration of the distribution theory with the set of discontinuous test functions. Such a distribution theory for test functions having discontinuity at one point is developed. A fourparameter family of Schrodinger operators, formed by the operators with singular potential, singular metrics and singular gauge field, is considered. It is proved that this family of singular interactions describes all possible selfadjoint extensions of the second derivative operator defined on the functions vanishing in a neighbourhood of the point. Approximation by operators with smooth coefficients is discussed. (C) 1996 Academic Press, Inc.
http://lup.lub.lu.se/record/758068
http://dx.doi.org/10.1006/jmaa.1996.0256
scopus:0030187273
eng
Journal of Mathematical Analysis and Applications; 201(1), pp 287323 (1996)
ISSN: 0022247X
Matematik
POINT INTERACTIONS
ONEDIMENSION
Distribution theory for discontinuous test functions and differential operators with generalized coefficients
contributiontojournal/article
info:eurepo/semantics/article
text

A bihyperbolic finite volume method on quadrilateral meshes
https://lup.lub.lu.se/search/publication/ec8c5ef81cee4123a4c5cf1b253b7a4f
Schroll, Achim
Svensson, Fredrik
2006
A nonoscillatory, high resolution reconstruction method
on quadrilateral meshes in 2D is presented. It is a twodimensional extension of Marquina's hyperbolic method.
The generalization to quadrilateral meshes allows the method to simulate realistic flow problems in complex domains. An essential point in the construction of the method is a second order accurate approximation of gradients on an irregular, quadrilateral mesh. The resulting scheme is optimal in the sense that it is third order accurate and the reconstruction requires only nearest neighbour information.
Numerical experiments are presented and the computational results are compared to experimental data.
application/pdf
http://lup.lub.lu.se/record/527277
http://lup.lub.lu.se/search/ws/files/5204172/624051.pdf
scopus:32944460299
eng
info:eurepo/semantics/openAccess
Journal of Scientific Computing; 26(2), pp 237260 (2006)
ISSN: 15737691
Matematik
high resolution finite volume scheme
quadrilateral mesh.
hyperbolic reconstruction
Conservation law
A bihyperbolic finite volume method on quadrilateral meshes
contributiontojournal/article
info:eurepo/semantics/article
text

Globally Optimal Estimates for Geometric Reconstruction Problems
https://lup.lub.lu.se/search/publication/0dcd354bb6484b9bb7e0f7ca289cbc2f
Kahl, Fredrik
Henrion, Didier
2007
http://lup.lub.lu.se/record/788365
scopus:34247638173
eng
International Journal of Computer Vision; 74(1), pp 315 (2007)
ISSN: 15731405
Matematik
Globally Optimal Estimates for Geometric Reconstruction Problems
contributiontojournal/article
info:eurepo/semantics/article
text

Sparse Localization of Harmonic Audio Sources
https://lup.lub.lu.se/search/publication/3b47fdaa5d514c2ebfba2b0e0b08345a
Adalbjörnsson, Stefan Ingi
Kronvall, Ted
Burgess, Simon
Åström, Karl
Jakobsson, Andreas
2016
In this paper, we propose a novel method for estimating the locations of near and/or farfield harmonic audio sources impinging on an arbitrary, but calibrated, sensor array. Using a joint pitch and location estimation formed in two steps, we first estimate the fundamental frequencies and complex amplitudes under a sinusoidal model assumption, whereafter the location of each source is found by utilizing both the difference in phase and the relative attenuation of the magnitude estimates. As audio recordings often consist of multipitch signals exhibiting some degree of reverberation, where both the number of pitches and the source locations are unknown, we propose to use sparse heuristics to avoid the necessity of detailed a priori assumptions on the spectral and spatial model orders. The method’s performance is evaluated using both simulated and measured audio data, with the former showing that the proposed method achieves nearoptimal performance, whereas the latter confirms the method’s feasibility when used with real recordings.
application/pdf
http://lup.lub.lu.se/record/8409978
http://dx.doi.org/10.1109/TASLP.2015.2497798
http://lup.lub.lu.se/search/ws/files/4311040/8410148.pdf
scopus:84957545669
eng
info:eurepo/semantics/openAccess
IEEE/ACM Transactions on Audio, Speech, and Language Processing; 24(1), pp 117129 (2016)
ISSN: 23299290
Signalbehandling
Multipitch estimation
near and farfield localization
TDOA
block sparsity
convex optimization
ADMM
nonconvex sparsity
Sparse Localization of Harmonic Audio Sources
contributiontojournal/article
info:eurepo/semantics/article
text

Optimal Correspondences from Pairwise Constraints
https://lup.lub.lu.se/search/publication/b5c1671eca084042839074a832753454
Enqvist, Olof
Josephson, Klas
Kahl, Fredrik
2009
Correspondence problems are of great importance in computer vision. They appear as subtasks in many applications such as object recognition, merging partial 3D reconstructions and image alignment. Automatically matching features from appearance only is difficult and errors are frequent. Thus, it is necessary to use geometric consistency to remove incorrect correspondences. Typically heuristic methods like RANSAC or EMlike algorithms are used, but they risk getting trapped in local optima and are in no way guaranteed to ﬁnd the best solution. This paper illustrates how pairwise constraints in combination with graph methods can be used to efficiently ﬁnd optimal correspondences. These ideas are implemented on two basic geometric problems, 3D3D registration and 2D3D registration. The developed scheme can handle large rates of outliers and cope with multiple hypotheses. Despite the combinatorial explosion, the resulting algorithm which has been extensively evaluated on real data, yields competitive running times compared to state of the art
application/pdf
http://lup.lub.lu.se/record/1454017
http://dx.doi.org/10.1109/ICCV.2009.5459319
ISBN: 9781424444199
http://lup.lub.lu.se/search/ws/files/4311163/1454018.pdf
wos:000294955300167
scopus:77953183492
eng
info:eurepo/semantics/openAccess
pp 12951302 (2009)
ISSN: 15505499
Matematik
Datorseende och robotik (autonoma system)
Computer Vision
Geometry
Pairwise Constraints
Optimal
Optimal Correspondences from Pairwise Constraints
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Automatic registration of multimodal microscopy images for integrative analysis of prostate tissue sections
https://lup.lub.lu.se/search/publication/cb3371d9a6e048c2a102c25401895f61
Lippolis, Giuseppe
Edsjö, Anders
Helczynski, Leszek
Bjartell, Anders
Overgaard, Niels Christian
2013
Background
Prostate cancer is one of the leading causes of cancer related deaths. For diagnosis, predicting the outcome of the disease, and for assessing potential new biomarkers, pathologists and researchers routinely analyze histological samples. Morphological and molecular information may be integrated by aligning microscopic histological images in a multiplex fashion. This process is usually timeconsuming and results in intra and interuser variability. The aim of this study is to investigate the feasibility of using modern image analysis methods for automated alignment of microscopic images from differently stained adjacent paraffin sections from prostatic tissue specimens.
Methods
Tissue samples, obtained from biopsy or radical prostatectomy, were sectioned and stained with either hematoxylin & eosin (H&E), immunohistochemistry for p63 and AMACR or Time Resolved Fluorescence (TRF) for androgen receptor (AR).
Image pairs were aligned allowing for translation, rotation and scaling. The registration was performed automatically by first detecting landmarks in both images, using the scale invariant image transform (SIFT), followed by the wellknown RANSAC protocol for finding point correspondences and finally aligned by Procrustes fit. The Registration results were evaluated using both visual and quantitative criteria as defined in the text.
Results
Three experiments were carried out. First, images of consecutive tissue sections stained with H&E and p63/AMACR were successfully aligned in 85 of 88 cases (96.6%). The failures occurred in 3 out of 13 cores with highly aggressive cancer (Gleason score ≥ 8). Second, TRF and H&E image pairs were aligned correctly in 103 out of 106 cases (97%).
The third experiment considered the alignment of image pairs with the same staining (H&E) coming from a stack of 4 sections. The success rate for alignment dropped from 93.8% in adjacent sections to 22% for sections furthest away.
Conclusions
The proposed method is both reliable and fast and therefore well suited for automatic segmentation and analysis of specific areas of interest, combining morphological information with protein expression data from three consecutive tissue sections. Finally, the performance of the algorithm seems to be largely unaffected by the Gleason grade of the prostate tissue samples examined, at least up to Gleason score 7.
application/pdf
http://lup.lub.lu.se/record/4057761
http://dx.doi.org/10.1186/1471240713408
http://lup.lub.lu.se/search/ws/files/4174815/4057762.pdf
wos:000324290300001
scopus:84883522410
eng
info:eurepo/semantics/openAccess
BMC Cancer; 13, pp 408418 (2013)
ISSN: 14712407
Cancer och onkologi
Multiplex analysis
Histological sections
Hematoxylin & Eosin
p63/AMACR
Time resolved fluorescence imaging
Image registration
Scale invariant feature transform
Prostate cancer
Automatic registration of multimodal microscopy images for integrative analysis of prostate tissue sections
contributiontojournal/article
info:eurepo/semantics/article
text

Sparse Chroma Estimation for Harmonic Audio
https://lup.lub.lu.se/search/publication/e540815d9d1a40b18259471d22c5de26
Kronvall, Ted
Juhlin, Maria
Adalbjörnsson, Stefan Ingi
Jakobsson, Andreas
20150419
This work treats the estimation of the chromagram for harmonic audio signals using a block sparse reconstruction framework. Chroma has been used for decades as a key tool in audio analysis, and is typically formed using a Fourierbased framework that maps the fundamental frequency of a musical tone to its corresponding chroma. Such an approach often leads to problems with tone ambiguity, which we avoid by taking into account the harmonic structure and perceptional attributes in music. The performance of the proposed method is evaluated using real audio files, clearly showing preferable performance as compared to other commonly used methods.
application/pdf
http://lup.lub.lu.se/record/8046460
http://dx.doi.org/10.1109/ICASSP.2015.7178035
ISBN: 9781467369978
http://lup.lub.lu.se/search/ws/files/3858710/8046463.pdf
wos:000368452400116
scopus:84946079229
eng
info:eurepo/semantics/openAccess
Proceedings of the IEEE International Conference on Acoustic, Speech and Signal Processing; pp 579583 (2015)
ISSN: 2379190X
Sannolikhetsteori och statistik
chromagram
block sparsity
total variation
convex optimization
ADMM
Sparse Chroma Estimation for Harmonic Audio
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Fast reliable simulations of secondary settling tanks in wastewater treatment with semiimplicit time discretization
https://lup.lub.lu.se/search/publication/7d58467f9a4c49648cb69687006c8845
Diehl, Stefan
Farås, Sebastian
Mauritsson, Gustav
2015
The biokinetic and sedimentation processes of wastewater treatment plants can be modelled by a large system of coupled nonlinear ordinary and partial differential equations (ODEs and PDEs). The subprocess of continuous sedimentation, which contains concentration discontinuities, is modelled by a degenerate parabolic conservation PDE with spatially discontinuous coefficients. A spatial discretization of this PDE described in Bürger et al. (2013) results in a large system of methodoflines ODEs for the entire plant and simulation can be performed by integration in time. In practice, standard time integration methods available in commercial simulators are often used. Shortages of such methods are here shown, such as the smearing of shock waves by Runge–Kutta methods and long execution times. A semiimplicit time discretization, which is described in detail, provides substantially shorter computational times and is more efficient than standard methods.
http://lup.lub.lu.se/record/5421965
http://dx.doi.org/10.1016/j.camwa.2015.05.005
wos:000359963200006
scopus:84937727750
eng
Computers & Mathematics with Applications; 70(4), pp 459477 (2015)
ISSN: 08981221
Matematik
Beräkningsmatematik
Kemiteknik
Vattenbehandling
Nonlinear conservation PDE
Methodoflines (MOL)
Efficiency
Activated sludge process
Activated Sludge Model no. 1 (ASM1)
Benchmark Simulation Model (BSM)
Fast reliable simulations of secondary settling tanks in wastewater treatment with semiimplicit time discretization
contributiontojournal/article
info:eurepo/semantics/article
text

Nodal domains in the square – the Neumann case
https://lup.lub.lu.se/search/publication/31e252fe02044e6986fc50e5d5356f04
Helffer, Bernard
Persson Sundqvist, Mikael
2015
A. Pleijel has proved that in the case of the Laplacian on the square with Neumann condition, the equality in the Courant nodal theorem (Courant sharp situation) can only be true for a finite number of eigenvalues. We identify five Courant sharp eigenvalues for the Neumann Laplacian in the square, and prove that there are no other cases.
http://lup.lub.lu.se/record/8539801
wos:000365392600004
scopus:84943530258
eng
Moscow Mathematical Journal; 15(3), pp 455495 (2015)
ISSN: 16093321
Matematisk analys
Nodal domains
Courant theorem
Square
Neumann
Nodal domains in the square – the Neumann case
contributiontojournal/article
info:eurepo/semantics/article
text

Band functions in the presence of magnetic steps
https://lup.lub.lu.se/search/publication/e78970c560524352bddec32ac81baf35
Hislop, P. D.
Popoff, N.
Raymond, N.
Persson Sundqvist, Mikael
2016
We complete the analysis of the band functions for twodimensional magnetic Schrodinger operators with piecewise constant magnetic fields. The discontinuity of the magnetic field can create edge currents that flow along the discontinuity, which have been described by physicists. Properties of these edge currents are directly related to the behavior of the band functions. The effective potential of the fiber operator is an asymmetric double well (eventually degenerated) and the analysis of the splitting of the bands incorporates the asymmetry. If the magnetic field vanishes, the reduced operator has essential spectrum and we provide an explicit description of the band functions located below the essential spectrum. For nondegenerate magnetic steps, we provide an asymptotic expansion of the band functions at infinity. We prove that when the ratio of the two magnetic fields is rational, a splitting of the band functions occurs and has a natural order, predicted by numerical computations.
http://lup.lub.lu.se/record/8386464
http://dx.doi.org/10.1142/S0218202516500056
wos:000364233000005
scopus:84947019389
eng
Mathematical Models and Methods in Applied Sciences; 26(1), pp 161161 (2016)
ISSN: 17936314
Matematisk analys
band functions
edge currents
Magnetic Schrodinger operators
Band functions in the presence of magnetic steps
contributiontojournal/article
info:eurepo/semantics/article
text

Actions in the Eye: Dynamic Gaze Datasets and Learnt Saliency Models for Visual Recognition
https://lup.lub.lu.se/search/publication/e4efe293637e4466ac49c9675eeea446
Mathe, Stefan
Sminchisescu, Cristian
2015
Systems based on bagofwords models from image features collected at maxima of sparse interest point operators have been used successfully for both computer visual object and action recognition tasks. While the sparse, interestpoint based approach to recognition is not inconsistent with visual processing in biological systems that operate in 'saccade and fixate' regimes, the methodology and emphasis in the human and the computer vision communities remains sharply distinct. Here, we make three contributions aiming to bridge this gap. First, we complement existing stateofthe art large scale dynamic computer vision annotated datasets like Hollywood2 [1] and UCF Sports [2] with human eye movements collected under the ecological constraints of visual action and scene context recognition tasks. To our knowledge these are the first large human eye tracking datasets to be collected and made publicly available for video, vision. imar. ro/eyetracking (497,107 frames, each viewed by 19 subjects), unique in terms of their (a) large scale and computer vision relevance, (b) dynamic, video stimuli, (c) task control, as well as freeviewing. Second, we introduce novel dynamic consistency and alignment measures, which underline the remarkable stability of patterns of visual search among subjects. Third, we leverage the significant amount of collected data in order to pursue studies and build automatic, endtoend trainable computer vision systems based on human eye movements. Our studies not only shed light on the differences between computer vision spatiotemporal interest point image sampling strategies and the human fixations, as well as their impact for visual recognition performance, but also demonstrate that human fixations can be accurately predicted, and when used in an endtoend automatic system, leveraging some of the advanced computer vision practice, can lead to state of the art results.
http://lup.lub.lu.se/record/7602115
http://dx.doi.org/10.1109/TPAMI.2014.2366154
wos:000355931100009
scopus:84961654805
eng
IEEE Transactions on Pattern Analysis and Machine Intelligence; 37(7), pp 14081424 (2015)
ISSN: 19393539
Datorseende och robotik (autonoma system)
Visual action recognition
human eyemovements
consistency analysis
saliency prediction
large scale learning
Actions in the Eye: Dynamic Gaze Datasets and Learnt Saliency Models for Visual Recognition
contributiontojournal/article
info:eurepo/semantics/article
text

The ground state energy of the three dimensional GinzburgLandau functional. Part II: Surface regime
https://lup.lub.lu.se/search/publication/16afa2d8c7c14a6ca2fb9d6b3e4d0ab4
Fournais, Søren
Kachmar, Ayman
Persson Sundqvist, Mikael
2013
We study the GinzburgLandau model of superconductivity in three dimensions and for strong external magnetic fields. For magnetic field strengths above the phenomenologically defined second critical field it is known from Physics that superconductivity should be essentially restricted to a region near the boundary. We prove that the expected region does indeed carry superconductivity. Furthermore, we give precise energy estimates valid also in the regime around the second critical field which display the transition from bulk superconductivity to surface superconductivity. (C) 2012 Elsevier Masson SAS. All rights reserved.
http://lup.lub.lu.se/record/4215933
http://dx.doi.org/10.1016/j.matpur.2012.09.002
wos:000326359700007
scopus:84873570698
eng
Journal des Mathématiques Pures et Appliquées; 99(3), pp 343374 (2013)
ISSN: 00217824
Matematik
GinzburgLandau functional
Thermodynamic limits
Elliptic estimates
Variational methods
Magnetic Schrodinger operators
Semiclassical
analysis
The ground state energy of the three dimensional GinzburgLandau functional. Part II: Surface regime
contributiontojournal/article
info:eurepo/semantics/article
text

Multiscale ReverseTimeMigrationType Imaging Using the Dyadic Parabolic Decomposition of Phase Space
https://lup.lub.lu.se/search/publication/758fafc773dd4c5b9e795ca142ffc143
Andersson, Fredrik
de Hoop, Maarten V.
Wendt, Herwig
2015
We develop a representation of reversetime migration (RTM) in terms of Fourier integral operators, the canonical relations of which are graphs. Through the dyadic parabolic decomposition of phase space, we obtain the solution of the wave equation with a boundary source and homogeneous initial conditions using wave packets. On this basis, we develop a numerical procedure for the reversetime continuation from the boundary of scattering data and for RTM. The algorithms are derived from those we recently developed for the discrete approximate evaluation of the action of Fourier integral operators and inherit their conceptual and numerical properties.
http://lup.lub.lu.se/record/8548774
http://dx.doi.org/10.1137/15M1022057
wos:000367019300008
scopus:84954307465
eng
SIAM Journal of Imaging Sciences; 8(4), pp 23832411 (2015)
ISSN: 19364954
Matematik
Fourier integral operators
reversetime migration
dyadic parabolic
decomposition
caustics
reflection seismology
restricted angle
transform
Multiscale ReverseTimeMigrationType Imaging Using the Dyadic Parabolic Decomposition of Phase Space
contributiontojournal/article
info:eurepo/semantics/article
text

A FrostmanType Lemma for Sets with Large Intersections, and an Application to Diophantine Approximation
https://lup.lub.lu.se/search/publication/55e9f0fa2246464f8dade66b76e37691
Persson, Tomas
Reeve, Henry W. J.
2015
We consider classes G(s)([0, 1]) of subsets of [0, 1], originally introduced by Falconer, that are closed under countable intersections, and such that every set in the class has Hausdorff dimension at least s. We provide a Frostmantype lemma to determine if a limsup set is in such a class. Suppose that E = lim supE(n) subset of [0, 1], and that mu(n) are probability measures with support in En. If there exists a constant C such that integral integral vertical bar x  y vertical bar(s) d mu(n)(x) d mu(n)(y) < C for all n, then, under suitable conditions on the limit measure of the sequence (mu(n)), we prove that the set E is in the class G(s)([0, 1]). As an application we prove that, for alpha > 1 and almost all lambda is an element of (1/2, 1), the set Elambda(alpha) = {x is an element of [0, 1] : vertical bar x  s(n vertical bar) < 2(alpha n) infinitely often}, where s(n) is an element of {(1  lambda)Sigma(n)(k=0) a(k)lambda(k) and a(k) is an element of {0, 1}}, belongs to the class G(s) for s <= 1/alpha. This improves one of our previously published results.
http://lup.lub.lu.se/record/7432960
http://dx.doi.org/10.1017/S0013091514000066
wos:000353900900014
scopus:84928594501
eng
Proceedings of the Edinburgh Mathematical Society; 58(2), pp 521542 (2015)
ISSN: 14643839
Matematik
classes with large intersections
diophantine approximation
Hausdorff dimension
A FrostmanType Lemma for Sets with Large Intersections, and an Application to Diophantine Approximation
contributiontojournal/article
info:eurepo/semantics/article
text

BayesFlow: latent modeling of flow cytometry cell populations.
https://lup.lub.lu.se/search/publication/19fc7cac9174498fa41237744704b729
Johnsson, Kerstin
Wallin, Jonas
Fontes, Magnus
2016
Flow cytometry is a widespread singlecell measurement technology with a multitude of clinical and research applications. Interpretation of flow cytometry data is hard; the instrumentation is delicate and can not render absolute measurements, hence samples can only be interpreted in relation to each other while at the same time comparisons are confounded by intersample variation. Despite this, most automated flow cytometry data analysis methods either treat samples individually or ignore the variation by for example pooling the data. A key requirement for models that include multiple samples is the ability to visualize and assess inferred variation, since what could be technical variation in one setting would be different phenotypes in another.
http://lup.lub.lu.se/record/8592365
http://dx.doi.org/10.1186/s128590150862z
pmid:26755197
wos:000367874000001
scopus:84953851427
eng
BMC Bioinformatics; 17(1), no 25 (2016)
ISSN: 14712105
Matematisk analys
Flow cytometry
Bayesian hierarchical models
Modelbased clustering
BayesFlow: latent modeling of flow cytometry cell populations.
contributiontojournal/article
info:eurepo/semantics/article
text

Shortest Paths with HigherOrder Regularization
https://lup.lub.lu.se/search/publication/2e3f7fc4c7da4f30a3b5e014123415d7
Ulén, Johannes
Strandmark, Petter
Kahl, Fredrik
2015
This paper describes a new method of finding thin, elongated structures in images and volumes. We use shortest paths to minimize very general functionals of higherorder curve properties, such as curvature and torsion. Our method uses line graphs to find the optimal path on a given discretization, often in the order of seconds on a single computer. The curves are then refined using local optimization making it possible to recover very smooth curves. We are able to place constraints on our curves such as maximum integrated curvature, or a maximum curvature at any point of the curve. To our knowledge, we are the first to perform experiments in three dimensions with curvature and torsion regularization. The largest graphs we process have over a hundred billion arcs. Experiments on medical images and in multiview reconstruction show the significance and practical usefulness of higher order regularization.
http://lup.lub.lu.se/record/5149781
http://dx.doi.org/10.1109/TPAMI.2015.2409869
wos:000364831700018
scopus:84960943376
eng
IEEE Transactions on Pattern Analysis and Machine Intelligence; 37(12), pp 25882600 (2015)
ISSN: 19393539
Matematik
Shortest Paths with HigherOrder Regularization
contributiontojournal/article
info:eurepo/semantics/article
text

BranchandBound Methods for Euclidean Registration Problems.
https://lup.lub.lu.se/search/publication/84eaed0393e9470d99a98837632deff3
Olsson, Carl
Kahl, Fredrik
Oskarsson, Magnus
2009
In this paper, we propose a practical and efficient method for finding the globally optimal solution to the problem of determining the pose of an object. We present a framework that allows us to use pointtopoint, pointtoline, and pointtoplane correspondences for solving various types of pose and registration problems involving euclidean (or similarity) transformations. Traditional methods such as the iterative closest point algorithm or bundle adjustment methods for camera pose may get trapped in local minima due to the nonconvexity of the corresponding optimization problem. Our approach of solving the mathematical optimization problems guarantees global optimality. The optimization scheme is based on ideas from global optimization theory, in particular convex underestimators in combination with branchandbound methods. We provide a provably optimal algorithm and demonstrate good performance on both synthetic and real data. We also give examples of where traditional methods fail due to the local minima problem.
http://lup.lub.lu.se/record/1367607
http://dx.doi.org/10.1109/TPAMI.2008.131
wos:000264144500002
pmid:19299855
scopus:64849097743
eng
IEEE Transactions on Pattern Analysis and Machine Intelligence; 31(5), pp 783794 (2009)
ISSN: 19393539
Matematik
BranchandBound Methods for Euclidean Registration Problems.
contributiontojournal/article
info:eurepo/semantics/article
text

Efficient algorithm for edge cracked geometries
https://lup.lub.lu.se/search/publication/d52f64a78f2b4dff8d9296093a9af003
Englund, Jonas
2006
The stress field in a finite, edge cracked specimen under load is computed using algorithms based on two slightly different integral equations of the second kind. These integral equations are obtained through left regularizations of a first kind integral equation. In numerical experiments it is demonstrated that the stress field can be accurately computed. Highly accurate stress intensity factors and Tstresses are presented for several setups and extensive comparisons with results from the literature are made. For simple geometries the algorithms presented here achieve relative errors of less than 10(10). It is also shown that the present algorithms can accurately handle both geometries with arbitrarily shaped edge cracks and geometries containing several hundred edge cracks. All computations were performed on an ordinary workstation. Copyright (c) 2005 John Wiley & Sons, Ltd.
http://lup.lub.lu.se/record/404936
http://dx.doi.org/10.1002/nme.1599
wos:000238584800004
scopus:33745543356
eng
International Journal for Numerical Methods in Engineering; 66(11), pp 17911816 (2006)
ISSN: 10970207
Matematik
stress intensity factor
integral equation
edge crack
fast multipole
method
Tstress
Efficient algorithm for edge cracked geometries
contributiontojournal/article
info:eurepo/semantics/article
text

Automatic control and adaptive timestepping
https://lup.lub.lu.se/search/publication/41378d55ee2b4139af52f5811cc93404
Söderlind, Gustaf
2002
Adaptive timestepping is central to the efficient solution of initial value problems in ODEs and DAEs. The error committed in the discretization method primarily depends on the timestep size h, which is varied along the solution in order to minimize the computational effort subject to a prescribed accuracy requirement. This paper reviews the recent advances in developing local adaptivity algorithms based on well established techniques from linear feedback control theory, which is introduced in a numerical context. Replacing earlier heuristics, this systematic approach results in a more consistent and robust performance. The dynamic behaviour of the discretization method together with the controller is analyzed. We also review some basic techniques for the coordination of nonlinear equation solvers with the primary stepsize controller in implicit timestepping methods.
http://lup.lub.lu.se/record/323359
http://dx.doi.org/10.1023/A:1021160023092
wos:000179313300019
scopus:0036441379
eng
Numerical Algorithms; 31(14), pp 281310 (2002)
ISSN: 15729265
Matematik
control theory
ordinary differential equations
adaptivity
error
control
stepsize control
Automatic control and adaptive timestepping
contributiontojournal/article
info:eurepo/semantics/article
text

Operating charts for continuous sedimentation II: Step responses
https://lup.lub.lu.se/search/publication/3c9ee1ac345c40f19f8a90f0ee7a4ec5
Diehl, Stefan
2005
The process of continuous sedimentation of particles in a liquid has often been predicted by means of operating charts and massbalance considerations, where the underlying constitutive assumption is the one by Kynch. Much more complex operating charts (concentrationflux diagrams) can be obtained from a onedimensional model of an ideal continuous clarifierthickener unit. The engineering concept of 'optimal operation' is defined generally as a special type of solution of the model equation, which is a conservation law with a source term and a spacediscontinuous flux function. All qualitatively different step responses (with the unit initially in optimal operation in steady state) are presented and classified in terms of operating charts. Quantitative information relating several interesting variables are also presented concerning, for example, the time until overflow occurs as a function of the feed concentration and flux.
http://lup.lub.lu.se/record/213068
http://dx.doi.org/10.1007/s1066500564301
wos:000233350400003
scopus:28444479441
eng
Journal of Engineering Mathematics; 53(2), pp 139185 (2005)
ISSN: 00220833
Vattenbehandling
Vattenteknik
Matematik
Kemiteknik
thickener
operating charts
step response
continuous sedimentation
settling
Operating charts for continuous sedimentation II: Step responses
contributiontojournal/article
info:eurepo/semantics/article
text

Operating charts for continuous sedimentation III: control of step inputs
https://lup.lub.lu.se/search/publication/3cced738f94c4c39a519d63cc8327206
Diehl, Stefan
2006
The main purposes of a clarifierthickener unit is that it should produce a high underflow concentration and a zero effluent concentration. The main difficulty in the control of the clarificationthickening process (by adjusting a volume flow) is that it is nonlinear with complex relations between concentrations and volume flows via the solution of a PDE  a conservation law with a source term and a spacediscontinuous flux function. In order to approach this problem, control objectives for dynamic operation and strategies on how to meet these objectives are presented in the case when the clarifierthickener unit initially is in steady state in optimal operation and is subjected to step input data. A complete classification of such solutions is given by means of an operating chart (concentrationflux diagram).
http://lup.lub.lu.se/record/406007
http://dx.doi.org/10.1007/s1066500577203
wos:000238272400003
scopus:33745089598
eng
Journal of Engineering Mathematics; 54(3), pp 225259 (2006)
ISSN: 00220833
Reglerteknik
Matematik
Kemiteknik
Vattenteknik
Vattenbehandling
thickener
control
operating charts
continuous sedimentation
step response
Operating charts for continuous sedimentation III: control of step inputs
contributiontojournal/article
info:eurepo/semantics/article
text

Timestep adaptivity in variational integrators with application to contact problems
https://lup.lub.lu.se/search/publication/a7786cec58f84849a043c08b80c3c132
Modin, Klas
Führer, Claus
2006
Variable timestep methods, with general stepsize control objectives, are developed within the framework of variational integrators. This is accomplished by introducing discrete transformations similar to Poincares time transformation. While gaining from adaptive timesteps, the resulting integrators preserve the structural advantages of variational integrators, i.e., they are symplectic and momentum preserving. As an application, the methods are utilized for dynamic multibody systems governed by contact force laws. A suitable scaling function defining the stepsize control objective is derived.
http://lup.lub.lu.se/record/378569
http://dx.doi.org/10.1002/zamm.200610286
wos:000241653700005
scopus:33750554275
eng
Zeitschrift für Angewandte Mathematik und Mechanik; 86(10), pp 785794 (2006)
ISSN: 00442267
Matematik
contact problems
variable stepsize methods
variational integrators
transformations
Poincare
time scaling
Timestep adaptivity in variational integrators with application to contact problems
contributiontojournal/article
info:eurepo/semantics/article
text

A fast and highly automated approach to myocardial motion analysis using phase contrast magnetic resonance imaging.
https://lup.lub.lu.se/search/publication/e9ae70b741674a69ae96b5f51a4902f8
Bergvall, Erik
Cain, Peter
Arheden, Håkan
Sparr, Gunnar
2006
Purpose: To develop a fast and highly automated method for calculating twodimensional myocardial motion and deformation using velocity encoded magnetic resonance imaging. Materials and Methods: Twodimensional phase contrast magnetic resonance imaging was used to acquire time resolved velocity maps of the myocardium. Cardiac motion was calculated by an iterative integrationregularization scheme of low computational cost. Image segmentation was performed using active appearance models. Results: Validation of motion tracking was performed in N = 47 subjects using saturation gridtagging and closely followed "taglines." Image segmentation was validated vs. manual delineation. Conclusion: The speed and limited user interaction gives the method good potential for use in clinical practice.
http://lup.lub.lu.se/record/154340
http://dx.doi.org/10.1002/jmri.20565
pmid:16568435
wos:000237124800006
scopus:33646186816
eng
Journal of Magnetic Resonance Imaging; 23(5), pp 652661 (2006)
ISSN: 15222586
Radiologi och bildbehandling
analysis
kinematics
magnetic resonance imaging
cardiovascular system
velocity mapping
image
A fast and highly automated approach to myocardial motion analysis using phase contrast magnetic resonance imaging.
contributiontojournal/article
info:eurepo/semantics/article
text

Online Arabic handwriting recognition with templates
https://lup.lub.lu.se/search/publication/f80182ea3f124d52b81c65ed7f6134bb
Sternby, Jakob
Morwing, Jonas
Andersson, Jonas
Friberg, Christer
2009
After a long period of focus on western and East Asian scripts there is now a general trend in the online handwriting recognition community to explore recognition of other scripts such as Arabic and various Indic scripts. One difficulty with the Arabic script is the number and position of diacritic marks associated to Arabic characters. This paper explores the application of a template matching scheme to the recognition of Arabic script with a novel algorithm for dynamically treating the diacritical marks. Template based systems are robust to conditions with scarce training data and in experiments the proposed system outperformed a reference system based on the promising stateoftheart network technique of BLSTM. Experiments have been conducted in an environment similar to that of many handheld devices with promising results both in terms of memory consumption and response time. (C) 2009 Elsevier Ltd. All rights reserved.
http://lup.lub.lu.se/record/1492224
http://dx.doi.org/10.1016/j.patcog.2008.12.017
wos:000269727800017
scopus:68249125168
eng
42(12), pp 32783286 (2009)
ISSN: 18735142
ISSN: 00313203
Matematik
Diacritic
Branchandbound
Modeling
Template
Arabic
Online
HWR
Graph
Trie
Online Arabic handwriting recognition with templates
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

A new automated method for analysis of gatedSPECT images based on a threedimensional heart shaped model
https://lup.lub.lu.se/search/publication/f6c0eb2ca5bd4c26977bc855cababc7e
Lomsky, M
Richter, Jens
Johansson, L
El Ali, Henrik Hussein
Åström, Karl
Ljungberg, Michael
Edenbrandt, Lars
2005
A new automated method for quantification of left ventricular function from gatedsingle photon emission computed tomography ( SPECT) images has been developed. The method for quantification of cardiac function (CAFU) is based on a heart shaped model and the active shape algorithm. The model contains statistical information of the variability of left ventricular shape. CAFU was adjusted based on the results from the analysis of five simulated gatedSPECT studies with well defined volumes of the left ventricle. The digital phantom NURBSbased CardiacTorso (NCAT) and the MonteCarlo method SIMIND were used to simulate the studies. Finally CAFU was validated on ten rest studies from patients referred for routine stress/rest myocardial perfusion scintigraphy and compared with CedarSinai quantitative gatedSPECT (QGS), a commercially available program for quantification of gatedSPECT images. The maximal differences between the CAFU estimations and the true left ventricular volumes of the digital phantoms were 11 ml for the enddiastolic volume (EDV), 3 ml for the endsystolic volume (ESV) and 3% for the ejection fraction (EF). The largest differences were seen in the smallest heart. In the patient group the EDV calculated using QGS and CAFU showed good agreement for large hearts and higher CAFU values compared with QGS for the smaller hearts. In the larger hearts, ESV was much larger for QGS than for CAFU both in the phantom and patient studies. In the smallest hearts there was good agreement between QGS and CAFU. The findings of this study indicate that our new automated method for quantification of gatedSPECT images can accurately measure left ventricular volumes and EF.
http://lup.lub.lu.se/record/235862
http://dx.doi.org/10.1111/j.1475097X.2005.00619.x
wos:000229956800008
pmid:15972026
scopus:21644456448
eng
Clinical Physiology and Functional Imaging20020101+01:00; 25(4), pp 234240 (2005)
ISSN: 14750961
Fysiologi
image processing
computerassisted diagnosis
gatedSPECT
radionuclide imaging
A new automated method for analysis of gatedSPECT images based on a threedimensional heart shaped model
contributiontojournal/article
info:eurepo/semantics/article
text

Algebraic Properties of Multilinear Constraints
https://lup.lub.lu.se/search/publication/064e4342ee7347a693b65f5ea02b31be
Heyden, Anders
Åström, Karl
1997
In this paper the different algebraic varieties that can be generated from multiple view geometry with uncalibrated cameras have been investigated. The natural descriptor, Vn, to work with is the image of P3 in P2 x P2 x ... x P2 under a corresponding product of projections, (A(1) x A(2) x ... x A(m)).
Another descriptor, the variety Vb, is the one generated by all bilinear forms between pairs of views, which consists of all points in P2 x P2 x ... x P2 where all bilinear forms vanish. Yet another descriptor, the variety Vt, is the variety generated by all trilinear forms between triplets of views. It has been shown that when m = 3, Vb is a reducible variety with one component corresponding to Vt and another corresponding to the trifocal plane.
Furthermore, when m = 3, Vt is generated by the three bilinearities and one trilinearity, when m = 4, Vt is generated by the six bilinearities and when m greater than or equal to 4, Vt can be generated by the ((m)(2)) bilinearities. This shows that four images is the generic case in the algebraic setting, because Vt can be generated by just bilinearities. Furthermore, some of the bilinearities may be omitted when m greater than or equal to 5. (C) 1997 by B. G. Teubner Stuttgart  John Wiley & Sons Ltd.
http://lup.lub.lu.se/record/788211
http://dx.doi.org/10.1002/(SICI)10991476(19970910)20:13<1135::AIDMMA908>3.0.CO;29
scopus:0031237868
eng
Mathematical Methods in the Applied Sciences; 20(13), pp 11351162 (1997)
ISSN: 10991476
Datorseende och robotik (autonoma system)
Matematik
Algebraic Properties of Multilinear Constraints
contributiontojournal/article
info:eurepo/semantics/article
text

Global Optimization through Rotation Space Search
https://lup.lub.lu.se/search/publication/b1c4e168d74442a087da46a7a651434e
Hartley, Richard I
Kahl, Fredrik
2009
This paper introduces a new algorithmic technique for solving certain problems in geometric computer vision. The main novelty of the method is a branchandbound search over rotation space, which is used in this paper to determine camera orientation. By searching over all possible rotations, problems can be reduced to known fixedrotation problems for which optimal solutions have been previously given. In particular, a method is developed for the estimation of the essential matrix, giving the first guaranteed optimal algorithm for estimating the relative pose using a cost function based on reprojection errors. Recently convex optimization techniques have been shown to provide optimal solutions to many of the common problems in structure from motion. However, they do not apply to problems involving rotations. The search method described in this paper allows such problems to be solved optimally. Apart from the essential matrix, the algorithm is applied to the camera pose problem, providing an optimal algorithm. The approach has been implemented and tested on a number of both synthetically generated and real data sets with good performance.
http://lup.lub.lu.se/record/1311470
http://dx.doi.org/10.1007/s1126300801869
wos:000262986100004
scopus:59149100446
eng
International Journal of Computer Vision; 82(1), pp 6479 (2009)
ISSN: 15731405
Matematik
Global optimization
Essential matrix
Branchandbound algorithm
Global Optimization through Rotation Space Search
contributiontojournal/article
info:eurepo/semantics/article
text

A regulator for continuous sedimentation in ideal clarifier–thickener units
https://lup.lub.lu.se/search/publication/346ec245058a47dcbb0d772ddbcb1a3d
Diehl, Stefan
2008
The purpose of this paper is to present a regulator for control of the continuoussedimentation process in a clarifier–thickener unit when this is modelled in one space dimension and when the settling properties of the solids obey Kynch’s assumption. The model is a scalar hyperbolic conservation law with spacediscontinuous flux function and point source. The most desired type of solution contains a large discontinuity. A common objective is to control the movement of this discontinuity subject to the requirement that the effluent of the process have zero concentration of particles. In addition, there may be a requirement that the underflow concentration of the thickened suspension lie above a predefined value. Based on previous results on the nonlinear behaviour of the process, a nonlinear regulator is presented. It controls the location of the large discontinuity indirectly by controlling the total mass. The process is stabilized significantly and large input oscillations can be handled.
http://lup.lub.lu.se/record/793628
http://dx.doi.org/10.1007/s1066500791493
wos:000253528000003
scopus:39749142230
eng
Journal of Engineering Mathematics; 60(34), pp 265291 (2008)
ISSN: 00220833
Reglerteknik
Matematik
Vattenbehandling
Vattenteknik
Kemiteknik
Control
Clarifier–thickener
Continuous sedimentation
Nonlinear regulator
Dynamic behaviour
A regulator for continuous sedimentation in ideal clarifier–thickener units
contributiontojournal/article
info:eurepo/semantics/article
text

On the speed of convergence of Newton's method for complex polynomials
https://lup.lub.lu.se/search/publication/22457e126989430195cc71d52d7245aa
Bilarev, Todor
Aspenberg, Magnus
Schleicher, Dierk
2016
We investigate Newton's method for complex polynomials of arbitrary degree d, normalized so that all their roots are in the unit disk. For each degree d, we give an explicit set Sd of 3.33d log(2) d(1 + o(1)) points with the following universal property: for every normalized polynomial of degree d there are d starting points in Sd whose Newton iterations find all the roots with a low number of iterations: if the roots are uniformly and independently distributed, we show that with probability at least 12/d the number of iterations for these d starting points to reach all roots with precision epsilon is O(d(2) log(4) d + d log vertical bar log epsilon vertical bar). This is an improvement of an earlier result by Schleicher, where the number of iterations is shown to be O(d(4) log(2) d + d(3) log(2) d vertical bar log epsilon vertical bar) in the worst case (allowing multiple roots) and O(d(3) log(2) d(log d + log delta) + d log vertical bar log epsilon vertical bar) for wellseparated (socalled deltaseparated) roots. Our result is almost optimal for this kind of starting points in the sense that the number of iterations can never be smaller than O(d(2)) for fixed e. It provides theoretical support for an empirical study, by Schleicher and Stoll, in which all roots of polynomials of degree 10(6) and more were found efficiently.
http://lup.lub.lu.se/record/8728531
http://dx.doi.org/10.1090/mcom/2985
wos:000369093400007
scopus:85000799269
eng
Mathematics of Computation; 85(298), pp 693705 (2016)
ISSN: 10886842
Beräkningsmatematik
On the speed of convergence of Newton's method for complex polynomials
contributiontojournal/article
info:eurepo/semantics/article
text

Stiffness 19522012. Sixty years in search of a definition
https://lup.lub.lu.se/search/publication/a580a50e9f8948149fa77ec1353a442b
Söderlind, Gustaf
Jay, Laurent
Manuel, Calvo
2015
Although stiff differential equations is a mature area of research in scientific computing, a rigorous and computationally relevant characterization of stiffness is still missing. In this paper, we present a critical review of the historical development of the notion of stiffness, before introducing a new approach.
A functional, called the stiffness indicator, is defined terms of the logarithmic norms of the differential equation's vector field. Readily computable along a solution to the problem, the stiffness indicator is independent of numerical integration methods, as well as of operational criteria such as accuracy requirements.
The stiffness indicator defines a local reference time scale $\Delta t$, which may vary with time and state along the solution. By comparing $\Delta t$ to the range of integration $T$, a large stiffness factor $T/\Delta t$ is a necessary condition for stiffness. In numerical computations, $\Delta t$ can be compared to the actual step size $h$, whose stiffness factor $h/\Delta t$ depends on the choice of integration method. Thus $\Delta t$ embodies the mathematical aspects of stiffness, while $h$ accounts for its numerical and operational aspects.
To demonstrate the theory, a number of highly nonlinear test problems are solved. We show, inter alia, that the stiffness indicator is able to distinguish the complex and rapidly changing behavior at (locally unstable) turning points, such as those observed in the van der Pol and Oregonator equations. The new characterization is mathematically rigorous, and in full agreement with observations in practical computations.
http://lup.lub.lu.se/record/5265741
http://dx.doi.org/10.1007/s1054301405033
wos:000354704400009
scopus:84929712609
eng
BIT Numerical Mathematics; 55(2), pp 531558 (2015)
ISSN: 00063835
Matematik
Initial value problems
stability
logarithmic norms
stiffness
stiffness indicator
stiffness factor
reference time scale
step size
Stiffness 19522012. Sixty years in search of a definition
contributiontojournal/article
info:eurepo/semantics/article
text

A multifractal mass transference principle for Gibbs measures with applications to dynamical Diophantine approximation
https://lup.lub.lu.se/search/publication/ee8a9922299f4e0b9f964d5da70696ea
Fan, AiHua
Schmeling, Jörg
Troubetzkoy, Serge
2013
Let mu be a Gibbs measure of the doubling map T of the circle. For a mugeneric point x and a given sequence {r(n)} subset of R+, consider the intervals (Tn x  r(n) (mod 1), Tn x + r(n) (mod 1)). In analogy to the classical Dvoretzky covering of the circle, we study the covering properties of this sequence of intervals. This study is closely related to the local entropy function of the Gibbs measure and to hitting times for moving targets. A mass transference principle is obtained for Gibbs measures that are multifractal. Such a principle was proved by Beresnevich and Velani [Ann. Math. 164 (2006) 971992] for monofractal measures. In the symbolic language, we completely describe the combinatorial structure of a typical relatively short sequence; in particular, we can describe the occurrence of 'atypical' relatively long words. Our results have a direct and deep numbertheoretical interpretation via inhomogeneous dyadic Diophantine approximation by numbers belonging to a given (dyadic) Diophantine class.
http://lup.lub.lu.se/record/4201015
http://dx.doi.org/10.1112/plms/pdt005
wos:000326748500006
scopus:84890238925
eng
Proceedings of the London Mathematical Society; 107, pp 11731219 (2013)
ISSN: 00246115
Matematik
A multifractal mass transference principle for Gibbs measures with applications to dynamical Diophantine approximation
contributiontojournal/article
info:eurepo/semantics/article
text

Steadystate analysis of activated sludge processes with a settler model including sludge compression
https://lup.lub.lu.se/search/publication/267e0e1ab30d439f93bb4f3438a1335a
Diehl, Stefan
Zambrano, Jesús
Carlsson, Bengt
2016
A reduced model of a completely stirredtank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the BürgerDiehl settler model, which consists of a partial differential equation. Steadystate solutions of this partial differential equation are obtained from an ordinary differential equation, making steadystate analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludgeblanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steadystate mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steadystate concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration.
http://lup.lub.lu.se/record/8045344
http://dx.doi.org/10.1016/j.watres.2015.09.052
pmid:26476681
wos:000367276500010
scopus:84944462976
eng
Water Research; 88(1), pp 104116 (2016)
ISSN: 18792448
Matematik
Kemiteknik
Vattenbehandling
Vattenteknik
Bioreactor
BürgerDiehl settler model
Growth kinetics
Limiting flux
Secondary settling tank
Solids residence time (SRT).
Steadystate analysis of activated sludge processes with a settler model including sludge compression
contributiontojournal/article
info:eurepo/semantics/article
text

On the Ktheory of the C*algebra associated with a onesided shift space
https://lup.lub.lu.se/search/publication/22c08fe488624631879fb04e1562e5e3
Carlsen, Toke Meier
Silvestrov, Sergei
2010
Onesided shift spaces are a special kind of noninvertible topological dynamical system with which one can associate a C*algebra. We show how to construct the C*algebra associated with a onesided shift space as the CuntzPimsner C*algebra of a C*correspondence and use this to compute its Ktheory.
http://lup.lub.lu.se/record/1752768
http://dx.doi.org/10.3176/proc.2010.4.04
wos:000284152200004
scopus:79951836115
eng
Proceedings of the Estonian Academy of Sciences; 59(4), pp 272279 (2010)
ISSN: 17367530
Matematik
C*algebras
shift spaces
C*correspondences
Ktheory of C*algebras
CuntzPimsner C*algebras
operator algebra
symbolic dynamics
On the Ktheory of the C*algebra associated with a onesided shift space
contributiontojournal/article
info:eurepo/semantics/article
text

Adaptive Fingerprint Image Enhancement with Emphasis on Preprocessing of Data
https://lup.lub.lu.se/search/publication/44d2238cb59f47568264e4baa1caf856
Ström Bartunek, Josef
Nilsson, Mikael
Sällberg, Benny
Claesson, Ingvar
2013
This article proposes several improvements to an
adaptive fingerprint enhancement method that is based on
contextual filtering. The term adaptive implies that parameters
of the method are automatically adjusted based on the input
fingerprint image. Five processing blocks comprise the adaptive
fingerprint enhancement method, where four of these blocks are
updated in our proposed system. Hence, the proposed overall
system is novel. The four updated processing blocks are; preprocessing,
global analysis, local analysis and matched filtering.
In the preprocessing and local analysis blocks, a nonlinear
dynamic range adjustment method is used. In the global analysis
and matched filtering blocks, different forms of order statistical
filters are applied. These processing blocks yield an improved
and new adaptive fingerprint image processing method. The
performance of the updated processing blocks is presented in the
evaluation part of this paper. The algorithm is evaluated towards
the NIST developed NBIS software for fingerprint recognition on
FVC databases.
application/pdf
http://lup.lub.lu.se/record/3294696
http://dx.doi.org/10.1109/TIP.2012.2220373
wos:000314717800019
scopus:84872237660
eng
info:eurepo/semantics/closedAccess
IEEE Transactions on Image Processing; 22(2), pp 644656 (2013)
ISSN: 19410042
Matematik
successive mean quantization transform
Fourier transform
image processing
directional filtering
spectral feature estimation
Adaptive Fingerprint Image Enhancement with Emphasis on Preprocessing of Data
contributiontojournal/article
info:eurepo/semantics/article
text

An Adaptive Penalty MultiPitch Estimator with SelfRegularization
https://lup.lub.lu.se/search/publication/8237a0fe8f524404b201fcf4d2bf7c75
Elvander, Filip
Kronvall, Ted
Adalbjörnsson, Stefan Ingi
Jakobsson, Andreas
2016
This work treats multipitch estimation, and in particular the common misclassification issue wherein the pitch at half the true fundamental frequency, the suboctave, is chosen instead of the true pitch. Extending on current group LASSObased methods for pitch estimation, this work introduces an adaptive total variation penalty, which enforces both group and block sparsity, as well as deals with errors due to suboctaves. Also presented is a scheme for signal adaptive dictionary construction and automatic selection of the regularization parameters. Used together with this scheme, the proposed method is shown to yield accurate pitch estimates when evaluated on synthetic speech data. The method is shown to perform as good as, or better than, current stateoftheart sparse methods while requiring fewer tuning parameters than these, as well as several con ventional pitch estimation methods, even when these are given oracle model orders. When evaluated on a set of ten musical pieces, the method shows promising results for separating multipitch signals.
http://lup.lub.lu.se/record/8864026
http://dx.doi.org/10.1016/j.sigpro.2016.02.015
scopus:84961214480
wos:000377325400006
eng
Signal Processing; 127, pp 5670 (2016)
ISSN: 01651684
Signalbehandling
Sannolikhetsteori och statistik
Multipitch estimation
block sparsity
adaptive sparse penalty
selfregularization
ADMM
An Adaptive Penalty MultiPitch Estimator with SelfRegularization
contributiontojournal/article
info:eurepo/semantics/article
text

Information metrics for improved traffic model fidelity through sensitivity analysis and data assimilation
https://lup.lub.lu.se/search/publication/2531d9a7e4fa4efcac6a7c7aa7fe915e
Sopasakis, Alexandros
Katsoulakis, Markos
2016
We develop theoretical and computational tools which can appraise traffic flow models and optimize their performance against current
timeseries traffic data and prevailing conditions. The proposed methodology perturbs the parameter space and undertakes pathwise analysis
of the resulting time series. Most importantly the approach is valid even under nonequilibrium conditions
and is based on procuring pathspace (timeseries) information. More generally we propose a mathematical methodology
which quantifies traffic information loss.
In particular the method undertakes sensitivity analysis on available traffic data and optimizes the traffic
flow model based on two information
theoretic tools which we develop. One of them, the relative entropy rate, can adjust and optimize model parameter values in
order to reduce the information loss. More precisely, we use the relative entropy rate as an information metric between time
series data and parametrized stochastic
dynamics describing a microscopic traffic model. On the other hand, the pathspace Fisher Information Matrix, (pFIM) reduces
model complexity and can even be used to control fidelity. This is achieved by eliminating unimportant model
parameters or their combinations. This results in easier regression of parametric models with a smaller number of parameters.
The method reconstructs the Markov Chain and emulates the traffic dynamics through Monte Carlo simulations.
We use the microscopic interaction model from \cite{SK} as a representative traffic flow model to illustrate this
parameterization methodology. During the comparisons we use both synthetic and real, rushhour, traffic data
from highway US101 in Los Angeles, California.
http://lup.lub.lu.se/record/8560288
http://dx.doi.org/10.1016/j.trb.2016.01.003
scopus:84956640670
wos:000375505500001
eng
Transportation Research. Part B: Methodological; 86, pp 118 (2016)
ISSN: 01912615
Transportteknik och logistik
Sannolikhetsteori och statistik
Traffic model parametrization
Information theoretic tools
Relative entropy rate
Fisher information matrix
Stochastic microscopic dynamics
Inverse dynamic Monte Carlo.
Information metrics for improved traffic model fidelity through sensitivity analysis and data assimilation
contributiontojournal/article
info:eurepo/semantics/article
text

Human3.6M: Large Scale Datasets and Predictive Methods for 3D Human Sensing in Natural Environments.
https://lup.lub.lu.se/search/publication/6a72990919b5487990791140039117b3
Ionescu, Catalin
Papava, Dragos
Olaru, Vlad
Sminchisescu, Cristian
2014
We introduce a new dataset, Human3.6M, of 3.6 Million 3D Human poses, acquired by recording the performance of 11 subjects, under 4 different viewpoints, for training realistic human sensing systems and for evaluating the next generation of human pose estimation models. Besides increasing the size the current state of the art datasets by several orders of magnitude, we aim to complement such datasets with a diverse set of poses encountered in typical human activities (taking photos, posing, greeting, eating, etc.), with synchronized image, motion capture and depth data, and with accurate 3D body scans of all subjects involved. We also provide mixed reality videos where 3D human models are animated using motion capture data and inserted using correct 3D geometry, in complex real environments, viewed with moving cameras, and under occlusion. Finally, we provide large scale statistical models and detailed evaluation baselines for the dataset illustrating its diversity and the scope for improvement by future work in the research community. The dataset and code for the associated largescale learning models, features, visualization tools, as well as the evaluation server, are available online at http://vision.imar.ro/human3.6m.
http://lup.lub.lu.se/record/4223588
http://dx.doi.org/10.1109/TPAMI.2013.248
pmid:24344079
wos:000338209900004
scopus:84903127719
eng
IEEE Transactions on Pattern Analysis and Machine Intelligence; 36(7), pp 13251339 (2014)
ISSN: 19393539
Matematik
3D human pose estimation
human motion capture data
articulated body modeling
optimization
large scale learning
structured prediction
Fourier kernel approximations
Human3.6M: Large Scale Datasets and Predictive Methods for 3D Human Sensing in Natural Environments.
contributiontojournal/article
info:eurepo/semantics/article
text

Determination of normalized electric eigenfields in microwave cavities with sharp edges
https://lup.lub.lu.se/search/publication/c070638c64394b5e8fcb0d7e25c69af4
Helsing, Johan
Karlsson, Anders
2016
The magnetic field integral equation for axially symmetric cavities with perfectly conducting piecewise smooth surfaces is discretized according to a highorder convergent FourierNyström scheme. The resulting solver is used to accurately determine eigenwavenumbers and normalized electric eigenfields in the entire computational domain.
application/pdf
http://lup.lub.lu.se/record/8165500
http://dx.doi.org/10.1016/j.jcp.2015.09.054
http://lup.lub.lu.se/search/ws/files/1841746/8165517.pdf
wos:000365041900019
scopus:84945574441
eng
info:eurepo/semantics/openAccess
Journal of Computational Physics; 304, pp 465486 (2016)
ISSN: 00219991
Beräkningsmatematik
magnetic field integral equation (MFIE)
corner singularity
Nyström discretization
body of revolution (BOR)
radio frequency (RF) cavity
wakefield
Determination of normalized electric eigenfields in microwave cavities with sharp edges
contributiontojournal/article
info:eurepo/semantics/article
text

LowRank SecondOrder Splitting of LargeScale Differential Riccati Equations
https://lup.lub.lu.se/search/publication/98982f5062394500b0db1ead943cea2c
Stillfjord, Tony
2015
We apply first and secondorder splitting schemes to the differential Riccati equation. Such equations are very important in e.g. linear quadratic regulator (LQR) problems, where they provide a link between the state of the system and the optimal input. The methods can also be extended to generalized Riccati equations, e.g. arising from LQR problems given in implicit form. In contrast to previously proposed schemes such as BDF or Rosenbrock methods, the splitting schemes exploit the fact that the nonlinear and affine parts of the problem, when considered in isolation, have closedform solutions. We show that if the solution possesses lowrank structure, which is frequently the case, then this is preserved by the method. This feature is used to implement the methods efficiently for largescale problems. The proposed methods are expected to be competitive, as they at most require the solution of a small number of linear equation systems per time step. Finally, we apply our lowrank implementations to the Riccati equations arising from two LQR problems. The results show that the rank of the solutions stay low, and the expected orders of convergence are observed.
application/pdf
http://lup.lub.lu.se/record/5265732
http://dx.doi.org/10.1109/TAC.2015.2398889
http://lup.lub.lu.se/search/ws/files/1815034/5275983.pdf
wos:000367284100027
scopus:84942872964
eng
info:eurepo/semantics/openAccess
IEEE Transactions on Automatic Control; 60(10), pp 27912796 (2015)
ISSN: 00189286
Matematik
Differential Riccati equation
largescale
lowrank
Riccati differential equation
splitting methods
LowRank SecondOrder Splitting of LargeScale Differential Riccati Equations
contributiontojournal/article
info:eurepo/semantics/article
text

L2Roe: A lowdissipation version of Roe's approximate Riemann solver for low Mach numbers
https://lup.lub.lu.se/search/publication/b0952dd2babe42bf81632ba0dc4eefba
Osswald, Kai
Siegmund, Alexander
Birken, Philipp
Hannemann, Volker
Meister, Andreas
20150924
A modification of the Roe scheme called L2Roe for low dissipation low Mach Roe is presented. It reduces the dissipation of kinetic energy at the highest resolved wave numbers in a low Mach number test case of decaying isotropic turbulence. This is achieved by scaling the jumps in all discrete velocity components within the numerical flux function. An asymptotic analysis is used to show the correct pressure scaling at low Mach numbers and to identify the reduced numerical dissipation in that regime. Furthermore, the analysis allows a comparison with two other schemes that employ different scaling of discrete velocity jumps, namely, LMRoe and a method of Thornber et al. To this end, we present for the first time an asymptotic analysis of the last method. Numerical tests on cases ranging from low Mach number (M∞=0.001) to hypersonic (M∞=5) viscous flows are used to illustrate the differences between the methods and to show the correct behavior of L2Roe. No conflict is observed between the reduced numerical dissipation and the accuracy or stability of the scheme in any of the investigated test cases.
http://lup.lub.lu.se/record/8146348
http://dx.doi.org/10.1002/fld.4175
scopus:84945380019
wos:000374344700001
eng
International Journal for Numerical Methods in Fluids; (2015)
ISSN: 10970363
Beräkningsmatematik
Riemann solvers
finite volume methods
low mach
asymptotic analysis
numerical dissipation
L2Roe: A lowdissipation version of Roe's approximate Riemann solver for low Mach numbers
contributiontojournal/article
info:eurepo/semantics/article
text

Increasing clinical severity during a dengue virus type 3 Cuban epidemic: deep sequencing of evolving viral populations
https://lup.lub.lu.se/search/publication/0d4cafc77c32457bba320d79702834f9
RodriguezRoche, Rosmari
Blanc, Hervé
Bordería, Antonio V
Díaz, Gisell
Henningsson, Rasmus
Gonzalez, Daniel
Santana, Emidalys
Alvarez, Mayling
Castro, Osvaldo
Fontes, Magnus
Vignuzzi, Marco
Guzman, Maria G
20160217
During the DENV3 epidemic occurred in Havana in 20012002, severe disease was associated with the infection sequence DENV1/DENV3, whilst the sequence DENV2/DENV3 was associated with mild/asymptomatic infections. To determine the role of the virus in the increasing severity demonstrated during the epidemic serum samples collected at different point times were studied. A total of 22 fulllength sequences were obtained using a deep sequencing approach. Bayesian phylogenetic analysis of consensus sequences revealed that two DENV3 lineages were circulating in Havana at that time, both grouped within genotype III. The predominant lineage is closely related to Peruvian and Ecuadorian strains, whilst the minor lineage is related to Venezuelan strains. According to consensus sequences, relatively few nonsynonymous mutations were observed; only one was fixed during the epidemic at position 4380 in the NS2B gene. Intrahost genetic analysis indicated that a significant minor population was selected and became predominant towards the end of the epidemic. In conclusion, greater variability was detected during the epidemic's progression in terms of significant minority variants, particularly in the nonstructural genes. An increasing trend of genetic diversity towards the end of the epidemic was only observed for synonymous variant allele rates, with higher variability in secondary cases. Remarkably, significant intrahost genetic variation was demonstrated within the same patient during the course of secondary infection DENV1/DENV3, including changes in the structural proteins PrM and E. Therefore, the dynamic of evolving viral populations in the context of heterotypic antibodies could be related to the increasing clinical severity observed during the epidemic.
http://lup.lub.lu.se/record/8825146
http://dx.doi.org/10.1128/JVI.0264715
pmid:26889031
scopus:84964953214
wos:000375125400008
eng
Journal of Virology; 90(19), pp 43204333 (2016)
ISSN: 10985514
Infektionsmedicin
Increasing clinical severity during a dengue virus type 3 Cuban epidemic: deep sequencing of evolving viral populations
contributiontojournal/article
info:eurepo/semantics/article
text

In Defense of 3DLabel Stereo
https://lup.lub.lu.se/search/publication/0bbd40f953734cdfa78903f470b97e46
Olsson, Carl
Ulén, Johannes
Boykov, Yuri
2013
It is commonly believed that higher order smoothness
should be modeled using higher order interactions. For example,
2nd order derivatives for deformable (active) contours
are represented by triple cliques. Similarly, the 2nd
order regularization methods in stereo predominantly use
MRF models with scalar (1D) disparity labels and triple
clique interactions. In this paper we advocate a largely
overlooked alternative approach to stereo where 2nd order
surface smoothness is represented by pairwise interactions
with 3Dlabels, e.g. tangent planes. This general paradigm
has been criticized due to perceived computational complexity
of optimization in higherdimensional label space.
Contrary to popular beliefs, we demonstrate that representing
2nd order surface smoothness with 3D labels leads
to simpler optimization problems with (nearly) submodular
pairwise interactions. Our theoretical and experimental results
demonstrate advantages over stateoftheart methods
for 2nd order smoothness stereo.
http://lup.lub.lu.se/record/3914799
http://dx.doi.org/10.1109/CVPR.2013.226
wos:000331094301100
scopus:84887358167
eng
pp 17301737 (2013)
ISSN: 10636919
ISSN: 21636648
Datorseende och robotik (autonoma system)
Matematik
In Defense of 3DLabel Stereo
contributiontobookanthology/conference
info:eurepo/semantics/conferencePaper
text

Superconductivity between HC2 and HC3
https://lup.lub.lu.se/search/publication/fca07935d31a41878a00979f3c6c6d44
Helffer, Bernard
Fournais, Søren
Persson Sundqvist, Mikael
2011
Superconductivity for Type II superconductors in external magnetic fields of magnitude between the second and third critical fields is known to be restricted to a narrow boundary region. The profile of the superconducting order parameter in the Ginzburg–Landau model is expected to be governed by an effective onedimensional model. This is known to be the case for external magnetic fields sufficiently close to the third critical field. In this text we prove such a result on a larger interval of validity.
http://lup.lub.lu.se/record/4221747
http://dx.doi.org/10.4171/JST/12
scopus:84994181305
eng
Journal of Spectral Theory; 1(3), pp 273298 (2011)
ISSN: 1664039X
Matematik
Spectral theory
Ginzurg–Landau functional
Ordinary differential operator
Superconductivity between HC2 and HC3
contributiontojournal/article
info:eurepo/semantics/article
text

Phase field modelling of stress corrosion
https://lup.lub.lu.se/search/publication/811b5d069d5d4b89acc47ae7bb8f7c23
Ståhle, Per
Hansen, Eskil
2015
The evolution of surfaces exposed to an aggressive environment and mechanical load is studied. This is a process of stress corrosion that leads to pitting, crack initiation and growing cracks. In conventional fracture analyses a known or a postulated crack is required. A serious complication is that a large part of the lifetime of a crack or a surface flaw is spent during the initiation of the crack. The knowledge of the mechanisms leading from a pit, flaw, scratch, etc. to a crack is very limited. The motivation for the present study is to provide a model that will increase the understanding of the transition from stress induced surface roughening and pitting to growing cracks. The evolution of the originally flat surface involves free strain energy, chemical energy and gradient energy. A phase field model is used to capture the driving forces that the free energy causes. The flat surface is unstable and develop a waviness. Initially while the waves are shallow a spectrum of favoured spatial frequencies are found to be in accordance with the AsaroTillerGrinfeld theory. Later the surface curvature becomes larger at the depressions than at the higher parts of the surface. This increases the growth rate of formed pits. The pits finally develop into cracks. Also massive branching of pits and cracks is observed. (C) 2014 Elsevier Ltd. All rights reserved.
http://lup.lub.lu.se/record/5069986
http://dx.doi.org/10.1016/j.engfailanal.2014.07.025
wos:000347757600002
scopus:84911869294
eng
Engineering Failure Analysis; 47, pp 241251 (2015)
ISSN: 13506307
Matematik
Maskinteknik
Stress corrosion
Crack initiation
Surface morphology
Phase field
model
Antiplane strain
Phase field modelling of stress corrosion
contributiontojournal/article
info:eurepo/semantics/article
text

Nonlinear approximation of functions in two dimensions by sums of wave packets
https://lup.lub.lu.se/search/publication/7bbc049ac062456bb2f345f640e10c75
Andersson, Fredrik
Carlsson, Marcus
de Hoop, Maarten V.
2010
We consider the problem of approximating functions that arise in waveequation imaging by sums of wave packets. Our objective is to find sparse decompositions of image functions, over a finite range of scales. We also address the naturally connected task of numerically approximating the wavefront set. We present an approximation where we use the dyadic parabolic decomposition, but the approach is not limited to only this type. The approach makes use of expansions in terms of exponentials, while developing an algebraic structure associated with the decomposition of functions into wave packets. (c) 2009 Elsevier Inc. All rights reserved.
http://lup.lub.lu.se/record/1630780
http://dx.doi.org/10.1016/j.acha.2009.09.001
wos:000278798300005
scopus:78049424870
eng
Applied and Computational Harmonic Analysis; 29(2), pp 198213 (2010)
ISSN: 1096603X
Matematik
AAK theory in two variables
Prony's method in two variables
Wave packets
Dyadic parabolic decomposition
Nonlinear approximation
Nonlinear approximation of functions in two dimensions by sums of wave packets
contributiontojournal/article
info:eurepo/semantics/article
text