Lund University Publications
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Lund University Lund University Publications2000-01-01T00:00+00:001dailyComposition of dyadic paraproducts
https://lup.lub.lu.se/search/publication/26c0336e-4ab2-4ee8-baa2-d6debf4e1611
Pott, SandraReguera, Maria CarmenSawyer, Eric T.Wick, Brett D.2016-08-06We obtain necessary and sufficient conditions to characterize the boundedness of the composition of dyadic paraproduct operators.https://lup.lub.lu.se/record/26c0336e-4ab2-4ee8-baa2-d6debf4e1611http://dx.doi.org/10.1016/j.aim.2016.04.024wos:000378099600016scopus:84966372550engAdvances in Mathematics; 298, pp 581-611 (2016)ISSN: 0001-8708MathematicsParaproductsSarason ConjectureToeplitz OperatorTwo-weight inequalitiesComposition of dyadic paraproductscontributiontojournal/articleinfo:eu-repo/semantics/articletextTight global linear convergence rate bounds for Douglas–Rachford splitting
https://lup.lub.lu.se/search/publication/b9459797-a905-4368-8076-95ea4a2edc47
Giselsson, Pontus2017-12Recently, several authors have shown local and global convergence rate results for Douglas–Rachford splitting under strong monotonicity, Lipschitz continuity, and cocoercivity assumptions. Most of these focus on the convex optimization setting. In the more general monotone inclusion setting, Lions and Mercier showed a linear convergence rate bound under the assumption that one of the two operators is strongly monotone and Lipschitz continuous. We show that this bound is not tight, meaning that no problem from the considered class converges exactly with that rate. In this paper, we present tight global linear convergence rate bounds for that class of problems. We also provide tight linear convergence rate bounds under the assumptions that one of the operators is strongly monotone and cocoercive, and that one of the operators is strongly monotone and the other is cocoercive. All our linear convergence results are obtained by proving the stronger property that the Douglas–Rachford operator is contractive.https://lup.lub.lu.se/record/b9459797-a905-4368-8076-95ea4a2edc47http://dx.doi.org/10.1007/s11784-017-0417-1wos:000414719100004scopus:85015059438engJournal of Fixed Point Theory and Applications; 19(4), pp 2241-2270 (2017)ISSN: 1661-7738MathematicsDouglas–Rachford splittingFixed-point iterationsLinear convergenceMonotone operatorsTight global linear convergence rate bounds for Douglas–Rachford splittingcontributiontojournal/articleinfo:eu-repo/semantics/articletextAsymptotics of Chebyshev polynomials, I : subsets of R
https://lup.lub.lu.se/search/publication/68bf08f1-a9da-4d03-bd49-7f218b0f65af
Christiansen, Jacob S.Simon, BarryZinchenko, Maxim2017-04We 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.https://lup.lub.lu.se/record/68bf08f1-a9da-4d03-bd49-7f218b0f65afhttp://dx.doi.org/10.1007/s00222-016-0689-xwos:000398170000004scopus:84988369421engInventiones Mathematicae; 208(1), pp 217-245 (2017)ISSN: 0020-9910MathematicsAsymptotics of Chebyshev polynomials, I : subsets of Rcontributiontojournal/articleinfo:eu-repo/semantics/articletextColour rearrangement for dipole showers
https://lup.lub.lu.se/search/publication/6e09cba0-942e-41b9-908f-7685c6179107
Bellm, Johannes2018-07-01We present an algorithm to rearrange the colour chains of dipole showers in the shower process according to the colour amplitudes of a simple matrix element. We implement the procedure in the dipole shower of Herwig and show comparisons to data.https://lup.lub.lu.se/record/6e09cba0-942e-41b9-908f-7685c6179107http://dx.doi.org/10.1140/epjc/s10052-018-6070-zpmid:30393463scopus:85050716094engEuropean Physical Journal C; 78(7), no 601 (2018)ISSN: 1434-6044MathematicsColour rearrangement for dipole showerscontributiontojournal/letterinfo:eu-repo/semantics/articletextZeros of random functions generated with de branges kernels
https://lup.lub.lu.se/search/publication/e2e4ef2f-8ff1-41fe-b7aa-7587771a6df2
Antezana, JorgeMarzo, JordiOlsen, Jan Fredrik2017-04-01We study the point process given by the set of real zeros of random series generated with orthonormal bases of reproducing kernels of de Branges spaces. We find an explicit formula for the intensity function in terms of the phase of the Hermite-Biehler function generating the de Branges space. We prove that the intensity of the point process completely characterizes the underlying de Branges space.https://lup.lub.lu.se/record/e2e4ef2f-8ff1-41fe-b7aa-7587771a6df2http://dx.doi.org/10.1093/imrn/rnw078wos:000404042200002scopus:85024474492engInternational Mathematics Research Notices; 2017(8), pp 2284-2299 (2017)ISSN: 1073-7928MathematicsZeros of random functions generated with de branges kernelscontributiontojournal/articleinfo:eu-repo/semantics/articletextFast Classification of Empty and Occupied Parking Spaces Using Integral Channel Features
https://lup.lub.lu.se/search/publication/3c98a5ce-4f2b-4ae8-af77-5767e050bdfe
Ahrnbom, MartinÅström, KarlNilsson, Mikael2016-12-16In 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.https://lup.lub.lu.se/record/3c98a5ce-4f2b-4ae8-af77-5767e050bdfehttp://dx.doi.org/10.1109/CVPRW.2016.200ISBN: 9781467388504wos:000391572100193scopus:85010189034engMathematicsComputer Vision and Robotics (Autonomous Systems)Fast Classification of Empty and Occupied Parking Spaces Using Integral Channel Featurescontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextTransferring and compressing convolutional neural networks for face representations
https://lup.lub.lu.se/search/publication/04a61dac-b616-4585-8046-f35e569f7933
Grundström, JakobChen, JiandanLjungqvist, Martin GeorgÅström, Kalle2016In this work we have investigated face verification based on deep representations from Convolutional Neural Networks (CNNs) to find an accurate and compact face descriptor trained only on a restricted amount of face image data. Transfer learning by fine-tuning CNNs pre-trained on large-scale object recognition has been shown to be a suitable approach to counter a limited amount of target domain data. Using model compression we reduced the model complexity without significant loss in accuracy and made the feature extraction more feasible for real-time use and deployment on embedded systems and mobile devices. The compression resulted in a 9-fold reduction in number of parameters and a 5-fold speed-up in the average feature extraction time running on a desktop CPU. With continued training of the compressed model using a Siamese Network setup, it outperformed the larger model.https://lup.lub.lu.se/record/04a61dac-b616-4585-8046-f35e569f7933http://dx.doi.org/10.1007/978-3-319-41501-7_3ISBN: 978-3-319-41500-0ISBN: 978-3-319-41501-7wos:000386604000003scopus:84978872481engLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics); 9730, pp 20-29 (2016)ISSN: 0302-9743ISSN: 1611-3349MathematicsComputer Vision and Robotics (Autonomous Systems)Transferring and compressing convolutional neural networks for face representationscontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextRadially Weighted Besov Spaces and the Pick Property
https://lup.lub.lu.se/search/publication/662de4ac-8f63-47d5-8144-a4b1f282223c
Aleman, AlexandruHartz, MichaelMcCarthy, John E.Richter, Stefan2019For s∈ ℝ the weighted Besov space on the unit ball Bd of ℂd is defined by (Formula presented.). Here Rs is a power of the radial derivative operator (Formula presented.), V denotes Lebesgue measure, and ω is a radial weight function not supported on any ball of radius < 1. Our results imply that for all such weights ω and ν, every bounded column multiplication operator (Formula presented.) induces a bounded row multiplier (Formula presented.). Furthermore we show that if a weight ω satisfies that for some α > −1 the ratio ω(z)∕(1 −|z|2)α is nondecreasing for t0 < |z| < 1, then (Formula presented.) is a complete Pick space, whenever s ≥ (α + d)∕2.https://lup.lub.lu.se/record/662de4ac-8f63-47d5-8144-a4b1f282223chttp://dx.doi.org/10.1007/978-3-030-14640-5_3scopus:85066734560engTrends in Mathematics; pp 29-61 (2019)ISSN: 2297-0215ISSN: 2297-024XMathematicsBesov spaceComplete Pick spaceMultiplierRadially Weighted Besov Spaces and the Pick Propertycontributiontobookanthology/chapterinfo:eu-repo/semantics/bookParttextStochastic Analysis of Time-Difference and Doppler Estimates for Audio Signals
https://lup.lub.lu.se/search/publication/accd2b07-96d1-4159-b3a7-79f530e45b45
di Baja, Gabriella SannitiFred, AnaDe Marsico, MariaFlood, GabrielleHeyden, AndersÅström, Kalle2019Pairwise comparison of sound and radio signals can be used to estimate the distance between two units that send and receive signals. In a similar way it is possible to estimate differences of distances by correlating two received signals. There are essentially two groups of such methods, namely methods that are robust to noise and reverberation, but give limited precision and sub-sample refinements that are more sensitive to noise, but also give higher precision when they are initialized close to the real translation. In this paper, we present stochastic models that can explain the precision limits of such sub-sample time-difference estimates. Using these models new methods are provided for precise estimates of time-differences as well as Doppler effects. The developed methods are evaluated and verified on both synthetic and real data.https://lup.lub.lu.se/record/accd2b07-96d1-4159-b3a7-79f530e45b45http://dx.doi.org/10.1007/978-3-030-05499-1_7ISBN: 9783030054984scopus:85060089291engLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics); 11351 LNCS, pp 116-138 (2019)ISSN: 0302-9743ISSN: 1611-3349MathematicsDoppler effectSub-sample methodsTime-difference of arrivalUncertainty measureStochastic Analysis of Time-Difference and Doppler Estimates for Audio Signalscontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextSolvability and complex limit bicharacteristics
https://lup.lub.lu.se/search/publication/08cb567c-b80a-4c77-9a81-146d00b310a2
Dencker, Nils2020We shall study the solvability of pseudodifferential operators which are not of principal type. The operator will have complex principal symbol satisfying condition (Ψ) and we shall consider the limits of semibicharacteristics at the set where the principal symbol vanishes of at least second order. The convergence shall be as smooth curves, and we shall assume that the normalized complex Hamilton vector field of the principal symbol over the semicharacteristics converges to a real vector field. Also, we shall assume that the linearization of the real part of the normalized Hamilton vector field at the semibicharacteristic is tangent to and bounded on the tangent space of a Lagrangean submanifold at the semibicharacteristics, which we call a grazing Lagrangean space. Under these conditions one can invariantly define the imaginary part of the subprincipal symbol. If the quotient of the imaginary part of the subprincipal symbol with the norm of the Hamilton vector field switches sign from − to + on the bicharacteristics and becomes unbounded as they converge to the limit, then the operator is not solvable at the limit bicharacteristic.https://lup.lub.lu.se/record/08cb567c-b80a-4c77-9a81-146d00b310a2http://dx.doi.org/10.1007/978-3-030-31531-3_16scopus:85088574486engOperator Theory: Advances and Applications; 276, pp 247-276 (2020)ISSN: 0255-0156ISSN: 2296-4878MathematicsSolvability and complex limit bicharacteristicscontributiontobookanthology/chapterinfo:eu-repo/semantics/bookParttextStructural topology optimization of multibody systems
https://lup.lub.lu.se/search/publication/60682952-2ffd-4b44-820c-f3072ec90f29
Ghandriz, ToheedFührer, ClausElmqvist, Hilding2016-09-23Flexible 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 differential-algebraic 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.https://lup.lub.lu.se/record/60682952-2ffd-4b44-820c-f3072ec90f29http://dx.doi.org/10.1007/s11044-016-9542-7wos:000390126700009scopus:84988693272engMultibody System Dynamics; 39(1), pp 135-148 (2016)ISSN: 1384-5640MathematicsFlexible multibody dynamicsSIMPStructural topology optimizationTransient responseStructural topology optimization of multibody systemscontributiontojournal/articleinfo:eu-repo/semantics/articletextLieb–Thirring inequalities for complex finite gap Jacobi matrices
https://lup.lub.lu.se/search/publication/ffe60301-c4de-49bc-81c9-0ad0b94b8a4a
Christiansen, Jacob S.Zinchenko, Maxim2017-09We establish Lieb–Thirring power bounds on discrete eigenvalues of Jacobi operators for Schatten class complex perturbations of periodic and more generally finite gap almost periodic Jacobi matrices.https://lup.lub.lu.se/record/ffe60301-c4de-49bc-81c9-0ad0b94b8a4ahttp://dx.doi.org/10.1007/s11005-017-0961-zscopus:85019551756wos:000408007900008engLetters in Mathematical Physics; 107(9), pp 1769-1780 (2017)ISSN: 0377-9017MathematicsComplex perturbationsEigenvalues estimatesFinite gap Jacobi matricesLieb–Thirring inequalities for complex finite gap Jacobi matricescontributiontojournal/articleinfo:eu-repo/semantics/articletextDetermining the consistency of resolved triplets and fan triplets
https://lup.lub.lu.se/search/publication/fdca8f46-46f9-4f36-9165-05a3ec839dfb
Jansson, JesperLingas, AndrzejRajaby, RameshSung, Wing Kin2018-07-01The R+-F+-Consistency problem takes as input two sets R+ and R- of resolved triplets and two sets F+ and F- of fan triplets, and asks for a distinctly leaf-labeled tree that contains all elements in R+ ⊂ F+ and no elements in R- ⊂ F- as embedded subtrees, if such a tree exists. This article presents a detailed characterization of how the computational complexity of the problem changes under various restrictions. Our main result is an efficient algorithm for dense inputs satisfying R-=θ whose running time is linear in the size of the input and therefore optimal.https://lup.lub.lu.se/record/fdca8f46-46f9-4f36-9165-05a3ec839dfbhttp://dx.doi.org/10.1089/cmb.2017.0256scopus:85050286790pmid:29451395engJournal of Computational Biology; 25(7), pp 740-754 (2018)ISSN: 1066-5277Mathematicscomputational complexityphylogenetic treerooted triplets consistencytree algorithmDetermining the consistency of resolved triplets and fan tripletscontributiontojournal/articleinfo:eu-repo/semantics/articletextEnforcing the General Planar Motion Model : Bundle Adjustment for Planar Scenes
https://lup.lub.lu.se/search/publication/da1ecf18-5412-46a0-ac15-428465dba720
De Marsico, MariaSanniti di Baja, GabriellaFred, AnaFred, AnaValtonen Örnhag, MarcusWadenbäck, Mårten2020In this paper we consider the case of planar motion, where a mobile platform equipped with two cameras moves freely on a planar surface. The cameras are assumed to be directed towards the floor, as well as being connected by a rigid body motion, which constrains the relative motion of the cameras and introduces new geometric constraints. In the existing literature, there are several algorithms available to obtain planar motion compatible homographies. These methods, however, do not minimise a physically meaningful quantity, which may lead to issues when tracking the mobile platform globally. As a remedy, we propose a bundle adjustment algorithm tailored for the specific problem geometry. Due to the new constrained model, general bundle adjustment frameworks, compatible with the standard six degree of freedom model, are not directly applicable, and we propose an efficient method to reduce the computational complexity, by utilising the sparse structure of the problem. We explore the impact of different polynomial solvers on synthetic data, and highlight various trade-offs between speed and accuracy. Furthermore, on real data, the proposed method shows an improvement compared to generic methods not enforcing the general planar motion model.https://lup.lub.lu.se/record/da1ecf18-5412-46a0-ac15-428465dba720http://dx.doi.org/10.1007/978-3-030-40014-9_6ISBN: 9783030400132scopus:85079559362engLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics); 11996 LNCS, pp 119-135 (2020)ISSN: 0302-9743ISSN: 1611-3349MathematicsBundle adjustmentPlanar motionSLAMVisual OdometryEnforcing the General Planar Motion Model : Bundle Adjustment for Planar Scenescontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextOn-line Arabic handwriting recognition with templates
https://lup.lub.lu.se/search/publication/f80182ea-3f12-4d52-b81c-65ed7f6134bb
Sternby, JakobMorwing, JonasAndersson, JonasFriberg, Christer2009After a long period of focus on western and East Asian scripts there is now a general trend in the on-line 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 state-of-the-art 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.https://lup.lub.lu.se/record/1492224http://dx.doi.org/10.1016/j.patcog.2008.12.017wos:000269727800017scopus:68249125168eng42(12), pp 3278-3286 (2009)ISSN: 0031-3203ISSN: 1873-5142MathematicsDiacriticBranch-and-boundModelingTemplateArabicOn-lineHWRGraphTrieOn-line Arabic handwriting recognition with templatescontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertext