Dissertations / Theses on the topic 'Segmentation models'
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Camilleri, Liberato. "Statistical models for market segmentation." Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441119.
Full textHeiler, Matthias. "Image models for segmentation and recognition." [S.l. : s.n.], 2006. http://madoc.bib.uni-mannheim.de/madoc/volltexte/2006/1306.
Full textEslami, Seyed Mohammadali. "Generative probabilistic models for object segmentation." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8898.
Full textLi, Zhi. "Variational image segmentation, inpainting and denoising." HKBU Institutional Repository, 2016. https://repository.hkbu.edu.hk/etd_oa/292.
Full textYeo, Si Yong. "Implicit deformable models for biomedical image segmentation." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42416.
Full textBarker, Simon A. "Image segmentation using Markov random field models." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/272037.
Full textBarker, S. A. "Unsupervised image segmentation using Markov Random Field models." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596368.
Full textShepherd, T. "Dynamical models and machine learning for supervised segmentation." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18729/.
Full textLjolje, A. "Intonation and phonetic segmentation using hidden Markov models." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377219.
Full textChalana, Vikram. "Deformable models for segmentation of medical ultrasound images /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/8025.
Full textChaieb, Ines. "Essays on international asset pricing under segmentation and PPP deviations." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102485.
Full textThe second essay uses our theoretical model to address the question of whether the IFC investable indices are priced globally or locally. Indeed S&P/IFC provides two emerging market indices: the IFC global index (IFCG) and its subset the IFC investable index (IFCI). Since the IFCI is fully investable, both the academic and practitioners implicitly assume that this subset of emerging markets is priced in the global context. This is a critical assumption for corporate finance decisions and portfolio management. Hence, this essay investigates the pricing behavior of the IFCI index returns using a conditional version of our model that allows for segmentation and PPP deviations. The results suggest that local factors are important in explaining returns of the IFC investable indices and that the return behavior of IFCI indices is similar to that of the IFCG.
Chen, Liyuan. "Variational approaches in image recovery and segmentation." HKBU Institutional Repository, 2015. https://repository.hkbu.edu.hk/etd_oa/227.
Full textSchofield, Andrew John. "Neural network models for texture segmentation and target detection." Thesis, Keele University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358048.
Full textSubakan, Ozlem N. "Continuous mixture models for feature preserving smoothing and segmentation." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024915.
Full textLIMA, MAXIMILIANO MORENO. "FUZZY MODELS IN SEGMENTATION AND ANALYSIS OF BANK MARKETING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12290@1.
Full textEste trabalho tem como principal objetivo propor e desenvolver uma metodologia baseada em modelos fuzzy para a segmentação e caracterização dos segmentos que compõem o mercado bancário, permitindo um amplo conhecimento dos perfis de clientes, melhor adaptação das ofertas ao mercado e, conseqüentemente, melhores retornos financeiros. A metodologia proposta nesta dissertação pode ser dividida em três módulos principais: coleta e tratamento dos dados; definição dos segmentos; e caracterização e classificação dos segmentos. O primeiro módulo, denominado coleta e tratamento dos dados, abrange as pesquisas de marketing utilizadas na coleta dos dados e a aplicação de técnicas de pré-processamento de dados, para a limpeza (remoção de outliers e missing values) e normalização dos dados. O módulo de definição dos segmentos emprega o modelo fuzzy de agrupamento Fuzzy C-Means (FCM) na descoberta de grupos de clientes que apresentem características semelhantes. A escolha deste modelo de agrupamento deve-se à possibilidade de análise dos graus de pertinência de cada cliente em relação aos diferentes grupos, identificando os clientes entre segmentos e, conseqüentemente, elaborando ações efetivas para a sua transição ou manutenção nos segmentos de interesse. O módulo de caracterização e classificação dos segmentos é baseado em um Sistema de Inferência Fuzzy. Na primeira etapa deste módulo são selecionadas as variáveis mais relevantes, do ponto de vista da informação, para sua aplicação no processo de extração de regras. As regras extraídas para a caracterização dos segmentos são posteriormente utilizadas na construção de um sistema de inferência fuzzy dedicado à classificação de novos clientes. Este sistema permite que os analistas de marketing contribuam com novas regras ou modifiquem as já extraídas, tornando o modelo mais robusto e a segmentação de mercado uma ferramenta acessível a todos que dela se servem. A metodologia foi aplicada na segmentação de mercado do Banco da Amazônia, um banco estatal que atua na Amazônia Legal, cujo foco prioritário constitui o fomento da região. Avaliando a aplicação dos modelos fuzzy no estudo de caso, observam-se bons resultados na definição dos segmentos, com médias de valor de silhueta de 0,7, e na classificação da base de clientes, com acurácia de 100%. Adicionalmente, o uso destes modelos na segmentação de mercado possibilitou a análise dos clientes que estão entre segmentos e a caracterização desses segmentos por meio de uma base de regras, ampliando as análises dos analistas de marketing.
The main aim of this work is to propose and develop a methodology base don fuzzy models for segmentation and characterization of segments comprising the bank segment, allowing broad knowledge of client profiles, better suiting market needs, hence offering better financial results. The methodology proposed in this work may be divided into three main modules: data collection and treatment; definition of segments; and characterization and classification of segments. The first module, denominated data collection and treatment, encompasses marketing research used in data collection and application of techniques for pre-processing of data, for data trimming (removal of outliers and missing values) and normalization. The definition of segments adopts the Fuzzy C-Means (FCM) grouping model in identifying groups of clients with similar characteristics. The choice for this grouping model is due to the possibility of analyzing the membership coefficient of each client in connection with the different groups, thus identifying clients among segments and consequently elaborating effective actions for their transition to or maintenance in the segments of interest. The module of characterization and classification of segments is based on a Fuzzy Inference System. In the first stage, the most relevant variables from the information standpoint are selected, for application in the process of rule extraction. The rules extracted are then used in the construction of a fuzzy inference system dedicated to classifying new clients. This system allows marketing analysts to contribute with new rules or modify those already extracted, making the model more robust and the turning market segmentation into a tool accessible to all using it. This methodology was applied in the market segmentation of Banco da Amazônia, stte- contrlled bank acting in the Amazon region, with main focus of which is fostering the region´s development. The application of fuzzy models in the case study generated good results in the definition of segments, with average silhouette value of 0.7, and accuracy of 100% for client base classification. Furthermore, the use of these models in market segmentation allowed the analysis of clients classified between segments and the characterization of those segments by means of a set of rules, improving the analyses made by marketing analysts.
Budvytis, Ignas. "Novel probabilistic graphical models for semi-supervised video segmentation." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648293.
Full textBou, Albert. "Deep Learning models for semantic segmentation of mammography screenings." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265652.
Full textDenna uppsats undersöker hur väl moderna metoder presterar på semantisk segmentering av mammografibilder. Detta görs genom att utvärdera flera semantiska segmenteringsmetoder på ett dataset som är framtaget under detta examensarbete. Utvärderingarna genomförs genom att återimplementera flertalet semantiska segmenteringsmodeller för djupinlärning i Tensorflow och algoritmerna valideras på referensdatasetet Cityscapes. Därefter tränas modellerna också på det dataset med medicinska mammografi-bilder som är samlat och annoterat vid Science for Life Laboratory i Stockholm. Dessutom visar detta examensarbete att det är möjligt att öka segmenteringsprestandan genom att använda en adversarial träningsmetod efter att den klassiska träningsalgoritmen har konvergerat.
Rada, Lavdie. "Variational models and numerical algorithms for selective image segmentation." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/11093/.
Full textBadshah, Noor. "Fast iterative methods for variational models in image segmentation." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501735.
Full textPereañez, Marco. "Enlargement, subdivision and individualization of statistical shape models: Application to 3D medical image segmentation." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/441754.
Full textEsta tesis presenta tres propuestas originales y complementarias para mejorar la calidad de los modelos estadísticos de formas (SSMs) que mejoran la precisión de la segmentación de la imagen médica en aplicaciones difíciles. Proponemos, primero, mejorar la riqueza estadística de los SSMs por medio de una técnica para unir la representación de forma y las propiedades estadísticas de muchos modelos pre-existentes sin observaciones adicionales. Segundo, mejorar la representacion geométrica de los SSMs modelando simultáneamente las características globales y locales del objecto o de multiples anatomias. Por último, mejorar la especificidad de los SSMs mediante la integración de metadatos del paciente no derivados de la imagen, tales como, variables demográficas, conductuales y de entorno clínico, en la construcción de los modelos. Estas técnicas son demostradas y validadas en imágenes de resonancia magnética (MRI) y tomografía computarizada (CT) y en anatomias como el corazón, el cerebro y la espina dorsal humanos.
Wang, Chaohui. "Distributed and Higher-Order Graphical Models : towards Segmentation, Tracking, Matching and 3D Model Inference." Phd thesis, Ecole Centrale Paris, 2011. http://tel.archives-ouvertes.fr/tel-00658765.
Full textKozinski, Mateusz. "Segmentation of facade images with shape priors." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1017/document.
Full textThe aim of this work is to propose a framework for facade segmentation with user-defined shape priors. In such a framework, the user specifies a shape prior using a rigorously defined shape prior formalism. The prior expresses a number of hard constraints and soft preference on spatial configuration of segments, constituting the final segmentation. Existing approaches to the problem are affected by a compromise between the type of constraints, the satisfaction of which can be guaranteed by the segmentation algorithm, and the capability to approximate optimal segmentations consistent with a prior. In this thesis we explore a number of approaches to facade parsing that combine prior formalism featuring high expressive power, guarantees of conformance of the resulting segmentations to the prior, and effective inference. We evaluate the proposed algorithms on a number of datasets. Since one of our focus points is the accuracy gain resulting from more effective inference algorithms, we perform a fair comparison to existing methods, using the same data term. Our contributions include a combination of graph grammars for expressing variation of facade structure with graphical models encoding the energy of models of given structures for different positions of facade elements. We also present the first linear formulation of facade parsing with shape priors. Finally, we propose a shape prior formalism that enables formulating the problem of optimal segmentation as the inference in a Markov random field over the standard four-connected grid of pixels. The last method advances the state of the art by combining the flexibility of a user-defined grammar with segmentation accuracy that was reserved for frameworks with pre-defined priors before. It also enables handling occlusions by simultaneously recovering the structure of the occluded facade and segmenting the occluding objects. We believe that it can be extended in many directions, including semantizing three-dimensional point clouds and parsing images of general urban scenes
Demirkol, Onur Ali. "Segmentation Of Torso Ct Images." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607431/index.pdf.
Full textwatershed transformation and region merging. Moreover, a comparative analysis is performed among these methods to obtain the most efficient segmentation method for each tissue and organ in torso. Some improvements are proposed for increasing accuracy of some image segmentation methods.
Soliman, Ahmed Talaat Elsayed. "Hidden Markov Models Based Segmentation of Brain Magnetic Resonance Imaging." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_theses/80.
Full textGomes, Vicente S. A. "Global optimisation techniques for image segmentation with higher order models." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1334450/.
Full textCorneli, Marco. "Dynamic stochastic block models, clustering and segmentation in dynamic graphs." Thesis, Paris 1, 2017. http://www.theses.fr/2017PA01E012/document.
Full textThis thesis focuses on the statistical analysis of dynamic graphs, both defined in discrete or continuous time. We introduce a new extension of the stochastic block model (SBM) for dynamic graphs. The proposed approach, called dSBM, adopts non homogeneous Poisson processes to model the interaction times between pairs of nodes in dynamic graphs, either in discrete or continuous time. The intensity functions of the processes only depend on the node clusters, in a block modelling perspective. Moreover, all the intensity functions share some regularity properties on hidden time intervals that need to be estimated. A recent estimation algorithm for SBM, based on the greedy maximization of an exact criterion (exact ICL) is adopted for inference and model selection in dSBM. Moreover, an exact algorithm for change point detection in time series, the "pruned exact linear time" (PELT) method is extended to deal with dynamic graph data modelled via dSBM. The approach we propose can be used for change point analysis in graph data. Finally, a further extension of dSBM is developed to analyse dynamic net- works with textual edges (like social networks, for instance). In this context, the graph edges are associated with documents exchanged between the corresponding vertices. The textual content of the documents can provide additional information about the dynamic graph topological structure. The new model we propose is called "dynamic stochastic topic block model" (dSTBM).Graphs are mathematical structures very suitable to model interactions between objects or actors of interest. Several real networks such as communication networks, financial transaction networks, mobile telephone networks and social networks (Facebook, Linkedin, etc.) can be modelled via graphs. When observing a network, the time variable comes into play in two different ways: we can study the time dates at which the interactions occur and/or the interaction time spans. This thesis only focuses on the first time dimension and each interaction is assumed to be instantaneous, for simplicity. Hence, the network evolution is given by the interaction time dates only. In this framework, graphs can be used in two different ways to model networks. Discrete time […] Continuous time […]. In this thesis both these perspectives are adopted, alternatively. We consider new unsupervised methods to cluster the vertices of a graph into groups of homogeneous connection profiles. In this manuscript, the node groups are assumed to be time invariant to avoid possible identifiability issues. Moreover, the approaches that we propose aim to detect structural changes in the way the node clusters interact with each other. The building block of this thesis is the stochastic block model (SBM), a probabilistic approach initially used in social sciences. The standard SBM assumes that the nodes of a graph belong to hidden (disjoint) clusters and that the probability of observing an edge between two nodes only depends on their clusters. Since no further assumption is made on the connection probabilities, SBM is a very flexible model able to detect different network topologies (hubs, stars, communities, etc.)
Ivins, James P. "Statistical snakes: active region models." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484310.
Full textBuchta, Christian, and Sara Dolnicar. "Learning by simulation. Computer simulations for strategic marketing decision support in tourism." SFB Adaptive Information Systems and Modelling in Economics and Management Science, WU Vienna University of Economics and Business, 2003. http://epub.wu.ac.at/1718/1/document.pdf.
Full textSeries: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
Molin, Joel. "Foreground Segmentation of Moving Objects." Thesis, Linköping University, Department of Electrical Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52544.
Full textForeground segmentation is a common first step in tracking and surveillance applications. The purpose of foreground segmentation is to provide later stages of image processing with an indication of where interesting data can be found. This thesis is an investigation of how foreground segmentation can be performed in two contexts: as a pre-step to trajectory tracking and as a pre-step in indoor surveillance applications.
Three methods are selected and detailed: a single Gaussian method, a Gaussian mixture model method, and a codebook method. Experiments are then performed on typical input video using the methods. It is concluded that the Gaussian mixture model produces the output which yields the best trajectories when used as input to the trajectory tracker. An extension is proposed to the Gaussian mixture model which reduces shadow, improving the performance of foreground segmentation in the surveillance context.
Patenaude, Brian Matthew. "Bayesian statistical models of shape and appearance for subcortical brain segmentation." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:52f5fee0-60e8-4387-9560-728843e187b3.
Full textKantedal, Simon. "Evaluating Segmentation of MR Volumes Using Predictive Models and Machine Learning." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-171102.
Full textZeng, Jingying. "Latent Factor Models for Recommender Systems and Market Segmentation Through Clustering." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1491255524283942.
Full textAxberg, Elin, and Ida Klerstad. "Similarity models for atlas-based segmentation of whole-body MRI volumes." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-172792.
Full textLind, Johan. "Make it Meaningful : Semantic Segmentation of Three-Dimensional Urban Scene Models." Thesis, Linköpings universitet, Datorseende, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-143599.
Full textRuckert, Daniel. "Segmentation and tracking in cardiovascular images using geometrically deformable models and templates." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286210.
Full textTrajkovska, Vera [Verfasser], and Christoph [Akademischer Betreuer] Schnörr. "Learning Probabilistic Graphical Models for Image Segmentation / Vera Trajkovska ; Betreuer: Christoph Schnörr." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1177689987/34.
Full textRathke, Fabian [Verfasser], and Christoph [Akademischer Betreuer] Schnörr. "Probabilistic Graphical Models for Medical Image Segmentation / Fabian Rathke ; Betreuer: Christoph Schnörr." Heidelberg : Universitätsbibliothek Heidelberg, 2015. http://d-nb.info/1180395042/34.
Full textFerrand, M. "Data-driven, memory-based computational models of human segmentation of musical melody." Thesis, University of Edinburgh, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.650869.
Full textBoussaid, Haithem. "Efficient inference and learning in graphical models for multi-organ shape segmentation." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2015. http://www.theses.fr/2015ECAP0002/document.
Full textThis thesis explores the use of discriminatively trained deformable contour models (DCMs) for shape-based segmentation in medical images. We make contributions in two fronts: in the learning problem, where the model is trained from a set of annotated images, and in the inference problem, whose aim is to segment an image given a model. We demonstrate the merit of our techniques in a large X-Ray image segmentation benchmark, where we obtain systematic improvements in accuracy and speedups over the current state-of-the-art. For learning, we formulate training the DCM scoring function as large-margin structured prediction and construct a training objective that aims at giving the highest score to the ground-truth contour configuration. We incorporate a loss function adapted to DCM-based structured prediction. In particular, we consider training with the Mean Contour Distance (MCD) performance measure. Using this loss function during training amounts to scoring each candidate contour according to its Mean Contour Distance to the ground truth configuration. Training DCMs using structured prediction with the standard zero-one loss already outperforms the current state-of-the-art method [Seghers et al. 2007] on the considered medical benchmark [Shiraishi et al. 2000, van Ginneken et al. 2006]. We demonstrate that training with the MCD structured loss further improves over the generic zero-one loss results by a statistically significant amount. For inference, we propose efficient solvers adapted to combinatorial problems with discretized spatial variables. Our contributions are three-fold:first, we consider inference for loopy graphical models, making no assumption about the underlying graph topology. We use an efficient decomposition-coordination algorithm to solve the resulting optimization problem: we decompose the model’s graph into a set of open, chain-structured graphs. We employ the Alternating Direction Method of Multipliers (ADMM) to fix the potential inconsistencies of the individual solutions. Even-though ADMMis an approximate inference scheme, we show empirically that our implementation delivers the exact solution for the considered examples. Second,we accelerate optimization of chain-structured graphical models by using the Hierarchical A∗ search algorithm of [Felzenszwalb & Mcallester 2007] couple dwith the pruning techniques developed in [Kokkinos 2011a]. We achieve a one order of magnitude speedup in average over the state-of-the-art technique based on Dynamic Programming (DP) coupled with Generalized DistanceTransforms (GDTs) [Felzenszwalb & Huttenlocher 2004]. Third, we incorporate the Hierarchical A∗ algorithm in the ADMM scheme to guarantee an efficient optimization of the underlying chain structured subproblems. The resulting algorithm is naturally adapted to solve the loss-augmented inference problem in structured prediction learning, and hence is used during training and inference. In Appendix A, we consider the case of 3D data and we develop an efficientmethod to find the mode of a 3D kernel density distribution. Our algorithm has guaranteed convergence to the global optimum, and scales logarithmically in the volume size by virtue of recursively subdividing the search space. We use this method to rapidly initialize 3D brain tumor segmentation where we demonstrate substantial acceleration with respect to a standard mean-shift implementation. In Appendix B, we describe in more details our extension of the Hierarchical A∗ search algorithm of [Felzenszwalb & Mcallester 2007] to inference on chain-structured graphs
Chen, Zhibin. "Segmentation of MRI images using non parametric deformable models integrating fuzzy technique." Reims, 2009. http://theses.univ-reims.fr/exl-doc/GED00001122.pdf.
Full textThe research goal of this thesis is to develop an automatic segmentation method to segment brain MRI images into different tissues (gray matter, white matter, and cerebrospinal fluid), providing quantitative and precise brain measurements. In this dissertation, we have developed three non-parametric deformable models integrating statistical information and fuzzy information of images to segment the brain into different tissue types from multi types of MRI images. We firstly present a histogram analysis based algorithm, where the intensity distribution of the MRI images is modeled via the mixture Gaussian model (MGM). The parameters of components in MGM are estimated via the Expectation Maximization (EM) algorithm. Then the estimated parameters are used to guide the evolution of the level set curves to achieve the brain tissue segmentation. We then propose an improved algorithm to region-based geometric active contour. Thanks to the new regional term, the new algorithm solves the underlying stability problem associated with the original algorithm, and achieves convergence with less iteration number compared with the original algorithm. Finally, we present a multiclass algorithm by integrating fuzzy segmentation with the level set methods. The algorithm uses a set of ordinary differential equations; each of them represents a class to be segmented. The multiclass algorithm reduces the computational complexity compared with the existing multiphase algorithm, so speeds up the convergence rate. All algorithms are evaluated with simulated and real MRI images, and quantitative analyses are provided. The results are very encouraging
Schwaller, Loïc. "Exact Bayesian Inference in Graphical Models : Tree-structured Network Inference and Segmentation." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS210/document.
Full textIn this dissertation we investigate the problem of network inference. The statistical frame- work tailored to this task is that of graphical models, in which the (in)dependence relation- ships satis ed by a multivariate distribution are represented through a graph. We consider the problem from a Bayesian perspective and focus on a subset of graphs making structure inference possible in an exact and e cient manner, namely spanning trees. Indeed, the integration of a function de ned on spanning trees can be performed with cubic complexity with respect to number of variables under some factorisation assumption on the edges, in spite of the super-exponential cardinality of this set. A careful choice of prior distributions on both graphs and distribution parameters allows to use this result for network inference in tree-structured graphical models, for which we provide a complete and formal framework.We also consider the situation in which observations are organised in a multivariate time- series. We assume that the underlying graph describing the dependence structure of the distribution is a ected by an unknown number of abrupt changes throughout time. Our goal is then to retrieve the number and locations of these change-points, therefore dealing with a segmentation problem. Using spanning trees and assuming that segments are inde- pendent from one another, we show that this can be achieved with polynomial complexity with respect to both the number of variables and the length of the series
Suzani, Amin. "Automatic vertebrae localization, identification, and segmentation using deep learning and statistical models." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50722.
Full textApplied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
Möller, Sebastian. "Image Segmentation and Target Tracking using Computer Vision." Thesis, Linköpings universitet, Datorseende, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-68061.
Full textI detta examensarbete undersöks möjligheterna att detektera och spåra intressanta objekt i multispektrala infraröda videosekvenser. Den nuvarande metoden, som använder sig av rektanglar med fix storlek, har sina nackdelar. Dessa nackdelar kommer att lösas med hjälp av bildsegmentering för att uppskatta formen på önskade mål.Utöver detektering och spårning försöker vi också att hitta formen och konturen för intressanta objekt för att kunna använda den exaktare passformen vid kontrastberäkningar. Denna framsegmenterade kontur ersätter de gamla fixa rektanglarna som använts tidigare för att beräkna intensitetskontrasten för objekt i de infraröda våglängderna. Resultaten som presenteras visar att det för vissa objekt, som motmedel och facklor, är lättare att få fram en bra kontur samt målföljning än vad det är med helikoptrar, som var en annan önskad måltyp. De svårigheter som uppkommer med helikoptrar beror till stor del på att de är mycket svalare vilket gör att delar av helikoptern kan helt döljas i bruset från bildsensorn. För att kompensera för detta används metoder som utgår ifrån att objektet rör sig mycket i videon så att rörelsen kan användas som detekteringsparameter. Detta ger bra resultat för de videosekvenser där målet rör sig mycket i förhållande till sin storlek.
Engelbeen, Céline. "The segmentation problem in radiation therapy." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210107.
Full textMathematically, the segmentation problem amounts to decomposing a given nonnegative integer matrix A into a nonnegative integer linear combination of some binary matrices. These matrices have to respect the consecutive ones property. In clinical applications several constraints may arise that reduce the set of binary matrices which respect the consecutive ones property that we can use. We study some of them, as the interleaf distance constraint, the interleaf motion constraint, the tongue-and-groove constraint and the minimum separation constraint.
We consider here different versions of the segmentation problem with different objective functions. Hence we deal with the beam-on time problem in order to minimize the total time during which the patient is irradiated. We study this problem under the interleaf distance and the interleaf motion constraints. We consider as well this last problem under the tongue-and-groove constraint in the binary case. We also take into account the cardinality and the lex-min problem. Finally, we present some results for the approximation problem.
/Le problème de segmentation intervient lors de l'élaboration d'un plan de radiothérapie. Après que le médecin ait localisé la tumeur ainsi que les organes se situant à proximité de celle-ci, il doit aussi déterminer les différents dosages qui devront être délivrés. Il détermine alors une borne inférieure sur le dosage que doit recevoir la tumeur afin d'en avoir un contrôle satisfaisant, et des bornes supérieures sur les dosages des différents organes situés dans le champ. Afin de respecter au mieux ces bornes, le plan de radiothérapie doit être préparé de manière minutieuse. Nous nous intéressons à l'une des étapes à réaliser lors de la détermination de ce plan: l'étape de segmentation.
Mathématiquement, cette étape consiste à décomposer une matrice entière et positive donnée en une combinaison positive entière linéaire de certaines matrices binaires. Ces matrices binaires doivent satisfaire la contrainte des uns consécutifs (cette contrainte impose que les uns de ces matrices soient regroupés en un seul bloc sur chaque ligne). Dans les applications cliniques, certaines contraintes supplémentaires peuvent restreindre l'ensemble des matrices binaires ayant les uns consécutifs (matrices 1C) que l'on peut utiliser. Nous en avons étudié certaines d'entre elles comme celle de la contrainte de chariots, la contrainte d'interdiciton de chevauchements, la contrainte tongue-and-groove et la contrainte de séparation minimum.
Le premier problème auquel nous nous intéressons est de trouver une décomposition de la matrice donnée qui minimise la somme des coefficients des matrices binaires. Nous avons développé des algorithmes polynomiaux qui résolvent ce problème sous la contrainte de chariots et/ou la contrainte d'interdiction de chevauchements. De plus, nous avons pu déterminer que, si la matrice donnée est une matrice binaire, on peut trouver en temps polynomial une telle décomposition sous la contrainte tongue-and-groove.
Afin de diminuer le temps de la séance de radiothérapie, il peut être désirable de minimiser le nombre de matrices 1C utilisées dans la décomposition (en ayant pris soin de préalablement minimiser la somme des coefficients ou non). Nous faisons une étude de ce problème dans différents cas particuliers (la matrice donnée n'est constituée que d'une colonne, ou d'une ligne, ou la plus grande entrée de celle-ci est bornée par une constante). Nous présentons de nouvelles bornes inférieures sur le nombre de matrices 1C ainsi que de nouvelles heuristiques.
Finalement, nous terminons par étudier le cas où l'ensemble des matrices 1C ne nous permet pas de décomposer exactement la matrice donnée. Le but est alors de touver une matrice décomposable qui soit aussi proche que possible de la matrice donnée. Après avoir examiné certains cas polynomiaux nous prouvons que le cas général est difficile à approximer avec une erreur additive de O(mn) où m et n représentent les dimensions de la matrice donnée.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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