Hierarchical inference of disparity

Disparity selective cells in V1 respond to the correlated receptive fields of the left and right retinae, which do not necessarily correspond to the same object in the 3D scene, i.e., these cells respond equally to both false and correct stereo matches. On the other hand, neurons in the extrastriate visual area V2 show much stronger responses to correct visual matches [Bakin et al, 2000]. This indicates that a part of the stereo correspondence problem is solved during disparity processing in these two areas. However, the mechanisms employed by the brain to accomplish this task are not yet understood. Existing computational models are mostly based on cooperative computations in V1 [Marr and Poggio 1976, Read and Cumming 2007], without exploiting the potential benefits of the hierarchical structure between V1 and V2. Here we propose a two-layer graphical model for disparity estimation from stereo. The lower layer matches the linear responses of neurons with Gabor receptive fields across images. Nodes in the upper layer infer a sparse code of the disparity map and act as priors that help disambiguate false from correct matches. When learned on natural disparity maps, the receptive fields of the sparse code converge to oriented depth edges, which is consistent with the electrophysiological studies in macaque [von der Heydt et al, 2000]. Moreover, when such a code is used for depth inference in our two layer model, the resulting disparity map for the Tsukuba stereo pair [middlebury database] has 40% less false matches than the solution given by the first layer. Our model offers a demonstration of the hierarchical disparity computation, leading to testable predictions about V1-V2 interactions

Quadruple-peaked Line-of-sight Velocity Distributions in Shell Galaxies

We present an improved study of the expected shape of the line-of-sight velocity distribution in shell galaxies. We found a simple analytical expression connecting prominent and in principle observable characteristics of the line profile and mass-distribution of the galaxy. The prediction was compared with the results from a test-particle simulation of a radial merger.Comment: 2 pages, 1 figure, to appear in the Proceedings of JENAM 2010, Symposium 2: "Environment and the formation of galaxies: 30 years later

Learning sparse representations of depth

This paper introduces a new method for learning and inferring sparse representations of depth (disparity) maps. The proposed algorithm relaxes the usual assumption of the stationary noise model in sparse coding. This enables learning from data corrupted with spatially varying noise or uncertainty, typically obtained by laser range scanners or structured light depth cameras. Sparse representations are learned from the Middlebury database disparity maps and then exploited in a two-layer graphical model for inferring depth from stereo, by including a sparsity prior on the learned features. Since they capture higher-order dependencies in the depth structure, these priors can complement smoothness priors commonly used in depth inference based on Markov Random Field (MRF) models. Inference on the proposed graph is achieved using an alternating iterative optimization technique, where the first layer is solved using an existing MRF-based stereo matching algorithm, then held fixed as the second layer is solved using the proposed non-stationary sparse coding algorithm. This leads to a general method for improving solutions of state of the art MRF-based depth estimation algorithms. Our experimental results first show that depth inference using learned representations leads to state of the art denoising of depth maps obtained from laser range scanners and a time of flight camera. Furthermore, we show that adding sparse priors improves the results of two depth estimation methods: the classical graph cut algorithm by Boykov et al. and the more recent algorithm of Woodford et al.Comment: 12 page

Shell galaxies as laboratories for testing MOND

Tests of MOND in ellipticals are relatively rare because these galaxies often lack kinematic tracers in the regions where the MOND effects are significant. Stellar shells observed in many elliptical galaxies offer a promising way to constrain their gravitational field. Shells appear as glowing arcs around their host galaxy. They are observed up to ~100 kpc. The stars in axially symmetric shell systems move in nearly radial orbits. The radial distributions of shell locations and the spectra of stars in shells can be used to constrain the gravitational potential of their host galaxy. The symmetrical shell systems, being especially suitable for these studies, occur in approximately 3% of all early-type galaxies. Hence the shells substantially increase the number of ellipticals in which MOND can be tested up to large radii. In this paper, we review our work on shell galaxies in MOND. We summarize the paper B\'{i}lek et al. (2013), where we demonstrated the consistency of shell radii in an elliptical NGC 3923 with MOND, and the work B\'{i}lek et al. (2014), in which we predicted a giant (~200 kpc), as yet undiscovered shell of NGC 3923. We explain the shell identification method, which was used in these two papers. We further describe the expected shape of line profiles in shell spectra in MOND which is very special due to the direct relation of the gravitational field and baryonic matter distribution (B\'{i}lek et al., 2014, in preparation).Comment: 21 pages, 8 figures, 1 table, accepted for publication in the special MOND issue of the Canadian Journal of Physic

Dinamika tržišne orijentacije hrvatskog gospodarstva

It was the goal of this research to examine the dynamics of Croatian transformation to market orientation and test whether the market orientation model changes with time as the business environment changes. Based on the literature analysis, we proposed a hypothetical model which relies on behavioural approach in understanding market orientation. To empirically test the hypothetical model, we used data previously collected for 2001, and by replicating the same questionnaire now collected data for 2011. Data was analyzed by hierarchical regression analysis on the two sets of data. Our findings reveal that Croatian organizations reached the level of moderate market orientation leaving space for improvement. Findings also reveal that higher level of market orientation correlates with higher business performance. Furthermore, with development of ICT, the model of market orientation modified in time in a way that in predicting successful market oriented reaction, specific information on consumer satisfaction gains importance, while general information from competitor and consumer databases lose importance. Despite the changes in the relationships among the elements of market orientation, the model itself similarly predicts performance today as it did ten years ago. Managers are advised to increase implementation of market orientation especially focusing on market responsiveness as such behaviour will lead to better performance.Cilj ovog rada je bio ispitati dinamiku transformacije hrvatskog gospodarstva prema tržišnoj orijentaciji, te ispitati mijenja li se s vremenom model tržišne orijentacije slijedeći promjene u poslovnom okruženju. Analizom literature predložen je hipotetski model koji se oslanja na bihevioristički pristup u razumijevanju tržišne orijentacije. Kako bi se hipotetski model empirijski dokazao, korišteni su podaci prethodno prikupljeni 2001. godine, te su repliciranjem istog upitnika, u 2011. godinu prikupljeni novi podaci. Podaci su obrađeni korištenjem hijerarhijskih regresijskih analiza na dva seta podataka. Rezultati ukazuju da su hrvatski poslovni subjekti dosegli stupanj umjerene tržišne orijentacije, te stoga imaju prostora za poboljšanje, a da viši stupanj tržišna orijentacija korelira s većim poslovnim uspjehom. Nadalje, uslijed razvoja informacijske i komunikacijske tehnologije model tržišne orijentacije modificira se kroz vrijeme na način da u predviđanju uspješne tržišno orijentirane reakcije, specifične informacije o zadovoljstvu potrošača dobivaju značaj, dok opće informacije iz baza podataka o konkurentima i potrošačima gube značaj. Unatoč promjenama u odnosima elemenata modela tržišne orijentacije, sam model u podjednakoj mjeri predviđa uspjeh poslovnog subjekta kao i prije deset godina. Menadžerima se savjetuje da u što većoj mjeri implementiraju tržišnu orijentaciju posebice se pri tom fokusirajući na tržišno orijentiranu reakciju obzirom da će tako ostvariti veći tržišni uspjeh

Dinamika tržišne orijentacije hrvatskog gospodarstva

It was the goal of this research to examine the dynamics of Croatian transformation to market orientation and test whether the market orientation model changes with time as the business environment changes. Based on the literature analysis, we proposed a hypothetical model which relies on behavioural approach in understanding market orientation. To empirically test the hypothetical model, we used data previously collected for 2001, and by replicating the same questionnaire now collected data for 2011. Data was analyzed by hierarchical regression analysis on the two sets of data. Our findings reveal that Croatian organizations reached the level of moderate market orientation leaving space for improvement. Findings also reveal that higher level of market orientation correlates with higher business performance. Furthermore, with development of ICT, the model of market orientation modified in time in a way that in predicting successful market oriented reaction, specific information on consumer satisfaction gains importance, while general information from competitor and consumer databases lose importance. Despite the changes in the relationships among the elements of market orientation, the model itself similarly predicts performance today as it did ten years ago. Managers are advised to increase implementation of market orientation especially focusing on market responsiveness as such behaviour will lead to better performance.Cilj ovog rada je bio ispitati dinamiku transformacije hrvatskog gospodarstva prema tržišnoj orijentaciji, te ispitati mijenja li se s vremenom model tržišne orijentacije slijedeći promjene u poslovnom okruženju. Analizom literature predložen je hipotetski model koji se oslanja na bihevioristički pristup u razumijevanju tržišne orijentacije. Kako bi se hipotetski model empirijski dokazao, korišteni su podaci prethodno prikupljeni 2001. godine, te su repliciranjem istog upitnika, u 2011. godinu prikupljeni novi podaci. Podaci su obrađeni korištenjem hijerarhijskih regresijskih analiza na dva seta podataka. Rezultati ukazuju da su hrvatski poslovni subjekti dosegli stupanj umjerene tržišne orijentacije, te stoga imaju prostora za poboljšanje, a da viši stupanj tržišna orijentacija korelira s većim poslovnim uspjehom. Nadalje, uslijed razvoja informacijske i komunikacijske tehnologije model tržišne orijentacije modificira se kroz vrijeme na način da u predviđanju uspješne tržišno orijentirane reakcije, specifične informacije o zadovoljstvu potrošača dobivaju značaj, dok opće informacije iz baza podataka o konkurentima i potrošačima gube značaj. Unatoč promjenama u odnosima elemenata modela tržišne orijentacije, sam model u podjednakoj mjeri predviđa uspjeh poslovnog subjekta kao i prije deset godina. Menadžerima se savjetuje da u što većoj mjeri implementiraju tržišnu orijentaciju posebice se pri tom fokusirajući na tržišno orijentiranu reakciju obzirom da će tako ostvariti veći tržišni uspjeh

Nonlocal Schrödinger equations in metric measure spaces

In this note we consider the pointwise convergence to the initial data for the solutions of some nonlocal dyadic Schrödinger equations on spaces of homogeneous type. We prove the a.e. convergence when the initial data belongs to a dyadic version of an L2 based Besov space.Fil: Actis, Marcelo Jesús. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; ArgentinaFil: Aimar, Hugo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; ArgentinaFil: Bongioanni, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; ArgentinaFil: Gomez, Ivana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; Argentin