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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
491

Movimentos dos olhos e topografias de controle de estímulos em treino de discriminação condicional e testes de equivalência / Eye movements and stimulus control topographies in conditional discrimination training and equivalence tests

William Ferreira Perez 08 December 2008 (has links)
A análise operante dos movimentos dos olhos tem-se mostrado uma medida auxiliar no estudo de controle de estímulos, posto que diferentes topografias de controle de estímulo (TCE) correlacionam-se a diferentes padrões de movimento dos olhos, segundo dados recentes da literatura. O presente estudo buscou analisar experimentalmente os efeitos de diferentes TCE (seleção/rejeição) sobre o padrão dos movimentos dos olhos de quatro participantes submetidos a treinos de discriminação condicional e testes de equivalência. Figuras sem sentido, letras do alfabeto ocidental, números e letras do alfabeto grego foram utilizadas como estímulos visuais. Inicialmente, durante a fase de Linha de Base (LB), todos os participantes foram submetidos a um treino AB/BC e aos testes de transitividade (AC), simetria (CB e BA), equivalência (CA) e reflexividade (AA, BB e CC), nessa ordem. Em seguida, em seqüências distintas para cada participante, foram conduzidas diferentes fases de treino em que o controle por rejeição ou por seleção passaram a ser favorecidos por meio da manipulação das proporções de S+ e de S-. Na fase de Controle por Rejeição (RJ), os participantes foram submetidos a um treino DE/EF no qual o estabelecimento da TCE por rejeição fora favorecido; em seguida, foram realizados os testes (DF, FE, ED, FD, DD, EE e FF). Na fase de Controle por Seleção (SL), os participantes foram submetidos a um treino GH/HI no qual a TCE por seleção fora favorecida; em seguida, foram realizados os testes (GH, IH, GH, IG, GG, HH e II). Dois dos participantes foram submetidos às fases experimentais na ordem LB RJ SL; para os outros dois, a ordem das duas últimas fases foi invertida (LB SL RJ). Todos os participantes apresentaram alta porcentagem de acerto nos testes seguintes às fases LB e SL. Na fase RJ, somente um participante apresentou desempenho indicativo de controle por rejeição, ou seja, falhas sistemáticas nos testes de transitividade, equivalência e reflexividade. Para esse participante, na fase RJ, a topografia de olhar somente o S- antes de escolher um dos comparações foi ocorreu em alta freqüência comparada a olhar somente o S+. Nessa mesma fase, a freqüência e a duração do olhar para o S- também foram maiores quando comparadas ao S+. O inverso se deu na fase SL, ou seja, houve uma alta freqüência da topografia de olhar somente o S+, bem como houve maiores freqüências e durações de olhar ao S+ comparadas ao S-. De modo geral, para os demais participantes, os quais foram bem-sucedidos nos testes seguintes à fase RJ, a topografia de olhar antes de escolher um dos comparações, bem como a freqüência e a duração da fixação do olhar foram maiores para o S+ do que ao S- ao longo de todas as fases. O presente estudo mostra que diferenças nas TCE estabelecidas foram acompanhadas de diferenças na topografia, na freqüência e na duração do olhar para o S+ e o S-. Além disso, os resultados sugerem que é necessário investigar procedimentos capazes de garantir o estabelecimento do controle exclusivo por seleção ou rejeição. / The operant analysis of eye movements has been taken as an auxiliary measure in the study of stimulus control. Other researches have already shown that different stimulus control topographies (SCT) are correlated with different patterns of eye movements. The present study used an equipment to track the eye movements of four participants during conditional discrimination training and equivalence tests. It aimed to verify, for different sets of stimuli, the effect of different SCT (selection/rejection) over the eye movements patterns. Nonsense figures, letters, numbers and greek letters were used as visual stimuli. Initially, during the Base Line (BL) phase, all participants were submitted to AB/BC relations training and to the tests of transitivity (AC), symmetry (BA and CB), equivalence (CA) and reflexivity (AA, BB and CC), in this sequence, without biasing the establishment of any SCT. In the Rejection Control (RJ) phase, participants were submitted to DE/EF relations training in which the SCT reject was biased. After that, they went through the tests (DF, FE, ED, FD, DD, EE e FF). In the Selection Control (SL) phase, participants were submitted to GH/HI relations training in which the SCT select was biased. After that, they were submitted to the testes (GH, IH, GH, IG, GG, HH e II). Two participants were exposed to experimental phases in the sequence BL RJ SL. For the other ones the order of the last two phases were inverted (BL SL RJ). Following the suggestions of previews studies, in order to bias reject and select control, depending on the experimental phase, the proportions of S+ and S- during the training were manipulated. All participants showed high scores during the tests of BL and SL phases. In RJ phase, only one participant showed systematic failures in transitivity, equivalence and reflexivity tests a typical rejection performance. For this participant, in RJ phase, it was verified a high frequency of the topography of looking only at the S- before choosing one of the comparisons. In this phase, the frequency and the duration of looking at the S- were also higher then looking at the S+. The opposite was observed in the SL phase - a high frequency of the topography of looking only at the S+ before choosing and also a high frequency and duration of looking at the S+. In general, for those participants who did not failed in the testes of RJ phase, the topography, the frequency and the duration of looking at the S+ were higher when compared to the S- along all the experimental phases. The present study shows that for different SCT it was also observed differences in the topography, frequency and duration of looking at the S+ or S-. The results also suggest that it is necessary to investigate what kind of procedures are able to increase the chances of select and reject control to be exclusively establish during the training.
492

Análise econômica do impacto do manejo integrado de pragas sobre a produtividade da cana-de-açúcar no estado de São Paulo / Economic analysis of the integrated pest management impact on sugarcane productivity in the state of São Paulo

Gustavo Ferrarezi Giachini 10 February 2017 (has links)
Um dos principais desafios da agricultura, e mais especificamente da produção de cana-de-açúcar no Brasil, visando garantir o abastecimento do mercado doméstico e a competitividade nos mercados internacionais, é manter níveis elevados de produtividade. Embora tenha ocorrido um avanço significativo nas técnicas de produção nas últimas décadas, a produtividade desta lavoura se encontra, conforme alguns estudos disponíveis na literatura, aquém do seu nível potencial. Uma das alternativas para contribuir com o aumento da produtividade é a utilização de novas técnicas, como o Manejo Integrado de Pragas, por exemplo. Os trabalhos que avaliaram recentemente a produtividade do setor sugerem que há ganhos para os adotantes dessa técnica. Para o estado de São Paulo, porém, existem poucos estudos empíricos de avaliação de impacto no setor sucroalcooleiro. Portanto, o objetivo deste trabalho foi avaliar como a adoção de tecnologia, no caso o manejo integrado de pragas, pode impactar na produtividade da cana-de-açúcar nas Unidades de Produção Agropecuária (UPA) do estado de São Paulo, que constam no Levantamento Censitário de Unidades de Produção Agropecuárias (Projeto LUPA), do Instituto de Economia Agrícola (IEA). Para isto, utilizou-se o método de Propensity Score Matching (PSM) para medir o impacto da adoção tecnológica na produtividade. As estimativas mostraram efeitos positivos e significativos, indicando que o manejo integrado de pragas pode aumentar de 2,9 ton/ha a 4,4 ton/ha, aproximadamente, a produtividade da cana de açúcar. Os resultados indicam, também, que há maiores chances de adotar o manejo integrado de pragas osprodutores que apresentaram maiores níveis de instrução, os adeptos de técnicas de análise de solo, de adubação, mudas fiscalizadas entre outros. / One of the main challenges of agriculture, and more specifically of the production of sugarcane in Brazil, in order to guarantee domestic supply and competitiveness on the international markets, is to maintain high levels of productivity. Although there has been a significant advance in terms of production techniques in recent decades, the sugarcane yield, according to some studies in the literature, below its potential level. One of the alternatives to contribute to the productivity increase is the use of new techniques, such as Integrated Pest Management, for example. Papers that recently evaluated the agricultural productivity suggest that there are gains for the adopters of this technique. For the state of São Paulo, however, there are few empirical studies of impact assessment in the sugar and alcohol sector. Therefore, the objective of this study was to evaluate how the adoption of technology, in the specific case of the integrated pest management, can impact sugarcane\'s productivity in the Agricultural Production Units (UPA) of the State of São Paulo, which were in the Census Survey Of Agricultural Production Units (LUPA Project), published by the Institute of Agricultural Economics (IEA). For this purpose, the Propensity Score Matching method was implemented to measure the impact of technological adoption on productivity. Results suggested positive and significant effects, indicationg the Integrated Pest Management increases, approximately, the sugarcane productivity between 2,9 ton/ha to 4,4 ton/ha, according the empirical model specification. The analysis also highlighted a greater chance to adopt the integrated pest management by producers with highest levels of education, and the adopters of techniques of soil analysis, fertilization, and supervised seedlings.
493

Respostas de observação na tarefa de pareamento ao modelo: analisando topografias de controle de estímulos e seus efeitos sobre a formação de equivalência / Observing responses on the MTS task: Stimuli control topography analysis and their equivalence relations effects

Eliana Isabel de Moraes Hamasaki 02 April 2009 (has links)
Entendendo que o estudo das topografias de controle de estímulo (TCEs) pode ser beneficiado em um procedimento de discriminação condicional para a investigação de controle complexo de estímulos, em especial na formação de classes de estímulos equivalentes, o presente estudo busca investigar essa questão diretamente, por meio de um software que executa o matching-to-sample (MTS) de uma maneira modificada. Tal modificação na tarefa de MTS consiste basicamente da introdução de respostas de observação (ROs) como um possível recurso para a descrição e a avaliação do estabelecimento de diferentes TCEs tanto ao longo do treino de discriminações condicionais como dos testes para verificar a formação de classes de estímulos equivalentes. Para tanto, foram planejados três experimentos. No Experimento 1, os objetivos foram a) investigar a ocorrência e seqüência de ROs e b) analisar a probabilidade do estabelecimento de diferentes TCEs (seleção e rejeição). Participaram três estudantes universitários. Na tarefa, MTS com atraso de 0s e três estímulos de comparação, estes e o estímulo modelo apresentavam-se inicialmente cobertos, tornando-se visíveis somente após a emissão de ROs. Todos os participantes apresentaram sucesso na formação de equivalência, com probabilidades de respostas de escolha ao S+ sob controle tanto da TCE seleção como da TCE rejeição, demonstrando que as ROs tornaram-se um recurso efetivo para esse tipo de investigação. No Experimento 2, foram apresentadas variações metodológicas com o objetivo de favorecer o estabelecimento de uma ou de outra TCE (seleção ou rejeição), durante o treino das relações condicionais e verificar os efeitos destas variações no desempenho obtido nos testes. Participaram seis estudantes universitários submetidos a uma condição na qual a observação ao S+ (três participantes) ou ao S- (três participantes) foi impedida em 70% das tentativas de treino. Os resultados indicaram que as restrições à observação de S+ produziram maior prejuízo à formação de equivalência do que as restrições as restrições à observação de S-, além de se evidenciar a relativa falta de coerência entre as TCEs planejadas e as estabelecidas pelos participantes. Para o Experimento 3, no qual participaram 12 estudantes universitários, o arranjo experimental programado durante a fase de treino foi: a) definir S+ a partir da primeira RO emitida como uma situação favorecedora do estabelecimento da TCE seleção (para três participantes, em 100% das tentativas e para outros três, em aproximadamente 80% das tentativas) ; e b) definir o S+ a partir da terceira RO como uma situação favorecedora do estabelecimento da TCE rejeição (em 100% das tentativas para três participantes e em, aproximadamente 80%, para outros três). Nos resultados, destacou-se o sucesso da formação de classes de estímulos equivalentes no desempenho apresentado por todos os participantes sob as condições 1ª/80% e 3ª/80% e por apenas um participante da condição 1ª/100%. Nos desempenhos bem-sucedidos nos testes, identificou-se o estabelecimento de ambas TCEs, especialmente sob as condições 3ª/80% (todos os participantes) ou, majoritariamente da TCE seleção (único participante da condição 1ª/100%). O conjunto geral dos dados permite discutir que o favorecimento a uma ou outra TCE pode alterar o treino de condicionalidade, pois o sucesso na formação de equivalência parece ser produto de uma provável simultaneidade das diferentes TCEs. Neste sentido, há que se investir ainda mais nas manipulações cujo foco seja o planejamento de diferentes favorecimentos. / Understanding that the study of stimulus control topographies (SCT\'s) may be benefited on a conditional discrimination procedure to investigate the complex control of stimuli, specially in the classes formation of equivalent stimuli, this study investigates this issue directly, through a software that executes the matching-to-sample task (MTS) in a modified way. This change in the task of MTS consists basically of responses to observing responses (OR\'s) as a possible resource for describing and evaluating the establishment of much different TSC\'s, both during the long training of conditional discrimination and during the testing to verify the classes training of equivalent stimuli. For this, three experiments were designed. In Experiment 1, the objectives were a) to investigate the occurrence and sequence of OR\'s and b) to analyze the establishment probability of different SCT\'s (selection and rejection). Three under-graduate students participated. In the task, MTS with delay of 0s and three stimuli for comparison, the model and the stimulus were initially covered up and became visible only after the OR\'s issuance. All participants had success in the equivalence formation, with probabilities of responses choice to S+ under control of both the SCT selection and the SCT rejection, demonstrating that the OR\'s have become an effective resource for such research. In Experiment 2, methodological changes were made with the objective of encouraging the establishment of either SCT (selection or rejection) during the conditional relations training and to see the effects of these variations in performance obtained in the tests. Six under-graduate students participated submitted to a condition in which the observation of S+ (three participants) or the S- (three participants) was prevented in 70% of attempts at training. The results indicated that the restrictions on the observation of S+ produced more injury to the restrictions equivalence formation than the ones on the observation of S-, in addition to demonstrating the relative lack of coherence between the SCT\'s planned and established by the participants. For Experiment 3, in which 12 under-graduate students participated, the experimental apparatus programmed during the training was: a) to define S+ from the first issued OR as a situation favoring the TSC selection establishment (for three participants, 100% of attempts and three others, in approximately 80% of attempts), and b) to set the S+ from the third RO as a situation favoring the TSC rejection establishment (in 100% of attempts to three participants and approximately 80%, other three). In the results, the classes formation success of equivalent stimuli in the performance shown by all participants under the conditions 1st / 3rd and 80% / 80% and by only one participant of the 1st condition / 100% stood out. In the successful performance in tests, the establishment of two SCT\'s, specially under conditions of 3 / 80% (all participants), or primarily of SCT selection (single participant of the 1st condition / 100%) was identified. The general data set allows us to discuss the bias that either SCT may change the conditionality practice, since the success in equivalence formation seems to be a likely simultaneity product of the different SCT\'s. Accordingly, it is necessary to invest more in the manipulations in which the focus is the different bias planning.
494

Analysis and optimisation of stable matching in combined input and output queued switches

Schweizer, Andreas January 2009 (has links)
Output queues in network switches are known to provide a suitable architecture for scheduling disciplines that need to provide quality of service (QoS) guarantees. However, today’s memory technology is incapable of meeting the speed requirements. Combined input and output queued (CIOQ) switches have emerged as one alternative to address the problem of memory speed. When a switch of this architecture uses a stable matching algorithm to transfer packets across the switch fabric, an output queued (OQ) switch can be mimicked exactly with a speedup of only two. The use of a stable matching algorithm typically requires complex and time-consuming calculations to ensure the behaviour of an OQ switch is maintained. Stable matching algorithms are well studied in the area in which they originally appeared. However, little is presently known on how the stable matching algorithm performs in CIOQ switches and how key parameters are affected by switch size, traffic type and traffic load. Knowledge of how these conditions affect performance is essential to judge the practicability of an architecture and to provide useful information on how to design such switches. Until now, CIOQ switches were likely to be dismissed due to the high complexity of the stable matching algorithm when applied to other applications. However, the characteristics of a stable matching algorithm in a CIOQ switch have not been thoroughly analysed. The principal goal of this thesis is to identify the conditions the stable matching algorithm encounters in a CIOQ switch under realistic operational scenarios. This thesis provides accurate mathematical models based on Markov chains to predict the value of key parameters that affect the complexity and runtime of a stable matching algorithm in CIOQ switches. The applicability of the models is then backed up by simulations. The results of the analysis quantify critical operational parameters, such as the size and number of preference lists and runtime complexity. These provide detailed insights into switch behaviour and useful information for switch designs. Major conclusions to be drawn from this analysis include that the average values of the key parameters of the stable matching algorithm are feasibly small and do not strongly correlate with switch size, which is contrary to the behaviour of the stable matching ii algorithm in its original application. Furthermore, although these parameters have wide theoretical ranges, the mean values and standard deviations are found to be small under operational conditions. The results also suggest that the implementation becomes very versatile as the completion time of the stable matching algorithm is not strongly correlated to the network traffic type; that is, the runtime is minimally affected by the nature of the traffic.
495

Improving the Efficiency and Robustness of Intrusion Detection Systems

Fogla, Prahlad 20 August 2007 (has links)
With the increase in the complexity of computer systems, existing security measures are not enough to prevent attacks. Intrusion detection systems have become an integral part of computer security to detect attempted intrusions. Intrusion detection systems need to be fast in order to detect intrusions in real time. Furthermore, intrusion detection systems need to be robust against the attacks which are disguised to evade them. We improve the runtime complexity and space requirements of a host-based anomaly detection system that uses q-gram matching. q-gram matching is often used for approximate substring matching problems in a wide range of application areas, including intrusion detection. During the text pre-processing phase, we store all the q-grams present in the text in a tree. We use a tree redundancy pruning algorithm to reduce the size of the tree without losing any information. We also use suffix links for fast linear-time q-gram search during query matching. We compare our work with the Rabin-Karp based hash-table technique, commonly used for multiple q-gram matching. To analyze the robustness of network anomaly detection systems, we develop a new class of polymorphic attacks called polymorphic blending attacks, that can effectively evade payload-based network anomaly IDSs by carefully matching the statistics of the mutated attack instances to the normal profile. Using PAYL anomaly detection system for our case study, we show that these attacks are practically feasible. We develop a formal framework which is used to analyze polymorphic blending attacks for several network anomaly detection systems. We show that generating an optimal polymorphic blending attack is NP-hard for these anomaly detection systems. However, we can generate polymorphic blending attacks using the proposed approximation algorithms. The framework can also be used to improve the robustness of an intrusion detector. We suggest some possible countermeasures one can take to improve the robustness of an intrusion detection system against polymorphic blending attacks.
496

Signal reconstruction from incomplete and misplaced measurements

Sastry, Challa, Hennenfent, Gilles, Herrmann, Felix J. January 2007 (has links)
Constrained by practical and economical considerations, one often uses seismic data with missing traces. The use of such data results in image artifacts and poor spatial resolution. Sometimes due to practical limitations, measurements may be available on a perturbed grid, instead of on the designated grid. Due to algorithmic requirements, when such measurements are viewed as those on the designated grid, the recovery procedures may result in additional artifacts. This paper interpolates incomplete data onto regular grid via the Fourier domain, using a recently developed greedy algorithm. The basic objective is to study experimentally as to what could be the size of the perturbation in measurement coordinates that allows for the measurements on the perturbed grid to be considered as on the designated grid for faithful recovery. Our experimental work shows that for compressible signals, a uniformly distributed perturbation can be offset with slightly more number of measurements.
497

Indigo : une approche multi-stratégique et adaptative pour un alignement sémantique intégrant le contexte des données à apparier

Bououlid Idrissi, Youssef January 2008 (has links)
Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal
498

Semantic Enrichment of Ontology Mappings

Arnold, Patrick 04 January 2016 (has links) (PDF)
Schema and ontology matching play an important part in the field of data integration and semantic web. Given two heterogeneous data sources, meta data matching usually constitutes the first step in the data integration workflow, which refers to the analysis and comparison of two input resources like schemas or ontologies. The result is a list of correspondences between the two schemas or ontologies, which is often called mapping or alignment. Many tools and research approaches have been proposed to automatically determine those correspondences. However, most match tools do not provide any information about the relation type that holds between matching concepts, for the simple but important reason that most common match strategies are too simple and heuristic to allow any sophisticated relation type determination. Knowing the specific type holding between two concepts, e.g., whether they are in an equality, subsumption (is-a) or part-of relation, is very important for advanced data integration tasks, such as ontology merging or ontology evolution. It is also very important for mappings in the biological or biomedical domain, where is-a and part-of relations may exceed the number of equality correspondences by far. Such more expressive mappings allow much better integration results and have scarcely been in the focus of research so far. In this doctoral thesis, the determination of the correspondence types in a given mapping is the focus of interest, which is referred to as semantic mapping enrichment. We introduce and present the mapping enrichment tool STROMA, which obtains a pre-calculated schema or ontology mapping and for each correspondence determines a semantic relation type. In contrast to previous approaches, we will strongly focus on linguistic laws and linguistic insights. By and large, linguistics is the key for precise matching and for the determination of relation types. We will introduce various strategies that make use of these linguistic laws and are able to calculate the semantic type between two matching concepts. The observations and insights gained from this research go far beyond the field of mapping enrichment and can be also applied to schema and ontology matching in general. Since generic strategies have certain limits and may not be able to determine the relation type between more complex concepts, like a laptop and a personal computer, background knowledge plays an important role in this research as well. For example, a thesaurus can help to recognize that these two concepts are in an is-a relation. We will show how background knowledge can be effectively used in this instance, how it is possible to draw conclusions even if a concept is not contained in it, how the relation types in complex paths can be resolved and how time complexity can be reduced by a so-called bidirectional search. The developed techniques go far beyond the background knowledge exploitation of previous approaches, and are now part of the semantic repository SemRep, a flexible and extendable system that combines different lexicographic resources. Further on, we will show how additional lexicographic resources can be developed automatically by parsing Wikipedia articles. The proposed Wikipedia relation extraction approach yields some millions of additional relations, which constitute significant additional knowledge for mapping enrichment. The extracted relations were also added to SemRep, which thus became a comprehensive background knowledge resource. To augment the quality of the repository, different techniques were used to discover and delete irrelevant semantic relations. We could show in several experiments that STROMA obtains very good results w.r.t. relation type detection. In a comparative evaluation, it was able to achieve considerably better results than related applications. This corroborates the overall usefulness and strengths of the implemented strategies, which were developed with particular emphasis on the principles and laws of linguistics.
499

Graphical models and point set matching / Modelos Gráficos e Casamento de Padrões de Pontos

Caetano, Tiberio Silva January 2004 (has links)
Casamento de padrões de pontos em Espaços Euclidianos é um dos problemas fundamentais em reconhecimento de padrões, tendo aplicações que vão desde Visão Computacional até Química Computacional. Sempre que dois padrões complexos estão codi- ficados em termos de dois conjuntos de pontos que identificam suas características fundamentais, sua comparação pode ser vista como um problema de casamento de padrões de pontos. Este trabalho propõe uma abordagem unificada para os problemas de casamento exato e inexato de padrões de pontos em Espaços Euclidianos de dimensão arbitrária. No caso de casamento exato, é garantida a obtenção de uma solução ótima. Para casamento inexato (quando ruído está presente), resultados experimentais confirmam a validade da abordagem. Inicialmente, considera-se o problema de casamento de padrões de pontos como um problema de casamento de grafos ponderados. O problema de casamento de grafos ponderados é então formulado como um problema de inferência Bayesiana em um modelo gráfico probabilístico. Ao explorar certos vínculos fundamentais existentes em padrões de pontos imersos em Espaços Euclidianos, provamos que, para o casamento exato de padrões de pontos, um modelo gráfico simples é equivalente ao modelo completo. É possível mostrar que inferência probabilística exata neste modelo simples tem complexidade polinomial para qualquer dimensionalidade do Espaço Euclidiano em consideração. Experimentos computacionais comparando esta técnica com a bem conhecida baseada em relaxamento probabilístico evidenciam uma melhora significativa de desempenho para casamento inexato de padrões de pontos. A abordagem proposta é signi- ficativamente mais robusta diante do aumento do tamanho dos padrões envolvidos. Na ausência de ruído, os resultados são sempre perfeitos. / Point pattern matching in Euclidean Spaces is one of the fundamental problems in Pattern Recognition, having applications ranging from Computer Vision to Computational Chemistry. Whenever two complex patterns are encoded by two sets of points identifying their key features, their comparison can be seen as a point pattern matching problem. This work proposes a single approach to both exact and inexact point set matching in Euclidean Spaces of arbitrary dimension. In the case of exact matching, it is assured to find an optimal solution. For inexact matching (when noise is involved), experimental results confirm the validity of the approach. We start by regarding point pattern matching as a weighted graph matching problem. We then formulate the weighted graph matching problem as one of Bayesian inference in a probabilistic graphical model. By exploiting the existence of fundamental constraints in patterns embedded in Euclidean Spaces, we prove that for exact point set matching a simple graphical model is equivalent to the full model. It is possible to show that exact probabilistic inference in this simple model has polynomial time complexity with respect to the number of elements in the patterns to be matched. This gives rise to a technique that for exact matching provably finds a global optimum in polynomial time for any dimensionality of the underlying Euclidean Space. Computational experiments comparing this technique with well-known probabilistic relaxation labeling show significant performance improvement for inexact matching. The proposed approach is significantly more robust under augmentation of the sizes of the involved patterns. In the absence of noise, the results are always perfect.
500

Probability on the spaces of curves and the associated metric spaces via information geometry; radar applications / Probabilités sur les espaces de chemins et dans les espaces métriques associés via la géométrie de l’information ; applications radar

Le Brigant, Alice 04 July 2017 (has links)
Nous nous intéressons à la comparaison de formes de courbes lisses prenant leurs valeurs dans une variété riemannienne M. Dans ce but, nous introduisons une métrique riemannienne invariante par reparamétrisations sur la variété de dimension infinie des immersions lisses dans M. L’équation géodésique est donnée et les géodésiques entre deux courbes sont construites par tir géodésique. La structure quotient induite par l’action du groupe des reparamétrisations sur l’espace des courbes est étudiée. À l’aide d’une décomposition canonique d’un chemin dans un fibré principal, nous proposons un algorithme qui construit la géodésique horizontale entre deux courbes et qui fournit un matching optimal. Dans un deuxième temps, nous introduisons une discrétisation de notre modèle qui est elle-même une structure riemannienne sur la variété de dimension finie Mn+1 des "courbes discrètes" définies par n + 1 points, où M est de courbure sectionnelle constante. Nous montrons la convergence du modèle discret vers le modèle continu, et nous étudions la géométrie induite. Des résultats de simulations dans la sphère, le plan et le demi-plan hyperbolique sont donnés. Enfin, nous donnons le contexte mathématique nécessaire à l’application de l’étude de formes dans une variété au traitement statistique du signal radar, où des signaux radars localement stationnaires sont représentés par des courbes dans le polydisque de Poincaré via la géométrie de l’information. / We are concerned with the comparison of the shapes of open smooth curves that take their values in a Riemannian manifold M. To this end, we introduce a reparameterization invariant Riemannian metric on the infinite-dimensional manifold of these curves, modeled by smooth immersions in M. We derive the geodesic equation and solve the boundary value problem using geodesic shooting. The quotient structure induced by the action of the reparametrization group on the space of curves is studied. Using a canonical decomposition of a path in a principal bundle, we propose an algorithm that computes the horizontal geodesic between two curves and yields an optimal matching. In a second step, restricting to base manifolds of constant sectional curvature, we introduce a detailed discretization of the Riemannian structure on the space of smooth curves, which is itself a Riemannian metric on the finite-dimensional manifold Mn+1 of "discrete curves" given by n + 1 points. We show the convergence of the discrete model to the continuous model, and study the induced geometry. We show results of simulations in the sphere, the plane, and the hyperbolic halfplane. Finally, we give the necessary framework to apply shape analysis of manifold-valued curves to radar signal processing, where locally stationary radar signals are represented by curves in the Poincaré polydisk using information geometry.

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