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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.
121

Estimation de régularité locale

Servien, Rémi 12 March 2010 (has links) (PDF)
L'objectif de cette thèse est d'étudier le comportement local d'une mesure de probabilité, notamment au travers d'un indice de régularité locale. Dans la première partie, nous établissons la normalité asymptotique de l'estimateur des kn plus proches voisins de la densité et de l'histogramme. Dans la deuxième, nous définissons un estimateur du mode sous des hypothèses affaiblies. Nous montrons que l'indice de régularité intervient dans ces deux problèmes. Enfin, nous construisons dans une troisième partie différents estimateurs pour l'indice de régularité à partir d'estimateurs de la fonction de répartition, dont nous réalisons une revue bibliographique.
122

Géo localisation en environnement fermé des terminaux mobiles / Indoor geo-location static and dynamic geo-location of mobile terminals in indoor environments

Dakkak, Mustapha 29 November 2012 (has links)
Récemment, la localisation statique et dynamique d'un objet ou d'une personne est devenue l'un des plus importantes fonctionnalités d'un système de communication, du fait de ses multiples applications. En effet, connaître la position d'un terminal mobile (MT), en milieu extérieur ou intérieur, est généralement d'une importance majeure pour des applications fournissant des services basés sur la localisation. Ce développement des systèmes de localisation est dû au faible coût des infrastructures de réseau sans fil en milieu intérieur (WLAN). Les techniques permettant de localiser des MTs diffèrent selon les paramètres extraits des signaux radiofréquences émis entre des stations de base (BSs) et des MTs. Les conditions idéales pour effectuer des mesures sont des environnements dépourvus de tout obstacle, permettant des émissions directes entre BS et MT. Ce n'est pas le cas en milieu intérieur, du fait de la présence continuelle d'obstacles dans l'espace, qui dispersent les rayonnements. Les mesures prises dans ces conditions (NLOS, pour Non Line of Sight) sont imprévisibles et diffèrent de celles prises en condition LOS. Afin de réduire les erreurs de mesure, différentes techniques peuvent être utilisées, comme la mitigation, l'approximation, la correction à priori, ou le filtrage. En effet, l'application de systèmes de suivi (TSs) constitue une base substantielle pour la navigation individuelle, les réseaux sociaux, la gestion du trafic, la gestion des ressources mobiles, etc. Différentes techniques sont appliquées pour construire des TSs en milieu intérieur, où le signal est bruité, faible voire inexistant. Bien que les systèmes de localisation globaux (GPS) et les travaux qui en découlent fonctionnent bien hors des bâtiments et dans des canyons urbains, le suivi d'utilisateurs en milieu intérieur est bien plus problématique. De ce fait, le problème de prédiction reste un obstacle essentiel à la construction de TSs fiable dans de tels environnements. Une étape de prédiction est inévitable, en particulier, dans le cas où l'on manque d'informations. De multiples approches ont été proposées dans la littérature, la plupart étant basées sur un filtre linéaire (LF), un filtre de Kalman (KF) et ses variantes, ou sur un filtre particulaire (PF). Les filtres de prédiction sont souvent utilisés dans des problèmes d'estimation et l'application de la dérivation non entière peut limiter l'impact de la perte de performances. Ce travail présente une nouvelle approche pour la localisation intérieure par WLAN utilisant un groupement des coordonnées. Ensuite, une étude comparative des techniques déterministes et des techniques d'apprentissage pour la localisation intérieure est présentée. Enfin, une nouvelle approche souple pour les systèmes de suivi en milieu intérieur, par application de la dérivation non entière, est présentée / Recently, the static and dynamic geo-location of a device or a person has become one of the most important aspects of communication systems because of its multiple applications. In general, knowing the position of a mobile terminal (MT) in outdoor or indoor environments is of major importance for applications providing services based on the location. The development of localization systems has been mainly driven by the avail- ability of the affordable cost of indoor wireless local area network (WLAN) infrastructure. There exist different techniques to localize MTs with the different mainly depending on the type of the metrics extracted from the radio frequency signals communicated between base stations (BSs) and MTs. Ideal measurements are taken in environments which are free of obstacles and in direct ray tracings between BS and MT. This is not the case in indoor environment because the daily use of permanent obstacles in the work space scatters the ray tracings. Measurements taken in Non Line Of Sight (NLOS) are unpredictable and different from those taken in LOS. In order to reduce measurement errors, one can apply different techniques such as mitigation, approximation, prior correction, or filtering. Tracking systems (TSs) have many concrete applications in the space of individual navigation, social net- working, asset management, traffic management, mobile resource management, etc. Different techniques are applied to build TSs in indoor environments, where the signal is noisy, weak or even non-existent. While the Global Positioning System (GPS) devices work well outside buildings and in urban canyons, tracking an indoor user in a real-world environment is much more problematic. The prediction problem remains an essential obstacle to construct reliable indoor TSs. Then lacks of reliable wireless signals represent the main issue for indoor geo-location systems. This obviously calls for some sort of predictions and corrections to overcome signal reliability, which unavoidably open the door for a multitude of challenges. Varieties of approaches were proposed in the literature. The most used are the ones based on prediction filters, such as Linear Filter (LF), Kalman Filter (KF) and its derivatives, and Particle Filters (PF). Prediction filters are often used in estimation problems and applying Digital Fractional Differentiation can limit the impact of performance degradations. This work presents a novel approach for the WLAN indoor geo-location by using coordinates clustering. This approach allows overcoming the limitations of NLOS methods without applying any of mitigation, approximation, prior correction, or filtering approaches. Then a comparison study of deterministic and learning techniques for indoor geo-location is presented. Finally, it presents a novel soft approach for indoor tracking system by applying digital fractional integration (DFI) to classical prediction filters
123

Algoritmo kNN para previsão de dados temporais: funções de previsão e critérios de seleção de vizinhos próximos aplicados a variáveis ambientais em limnologia / Time series prediction using a KNN-based algorithm prediction functions and nearest neighbor selection criteria applied to limnological data

Ferrero, Carlos Andres 04 March 2009 (has links)
A análise de dados contendo informações sequenciais é um problema de crescente interesse devido à grande quantidade de informação que é gerada, entre outros, em processos de monitoramento. As séries temporais são um dos tipos mais comuns de dados sequenciais e consistem em observações ao longo do tempo. O algoritmo k-Nearest Neighbor - Time Series Prediction kNN-TSP é um método de previsão de dados temporais. A principal vantagem do algoritmo é a sua simplicidade, e a sua aplicabilidade na análise de séries temporais não-lineares e na previsão de comportamentos sazonais. Entretanto, ainda que ele frequentemente encontre as melhores previsões para séries temporais parcialmente periódicas, várias questões relacionadas com a determinação de seus parâmetros continuam em aberto. Este trabalho, foca-se em dois desses parâmetros, relacionados com a seleção de vizinhos mais próximos e a função de previsão. Para isso, é proposta uma abordagem simples para selecionar vizinhos mais próximos que considera a similaridade e a distância temporal de modo a selecionar os padrões mais similares e mais recentes. Também é proposta uma função de previsão que tem a propriedade de manter bom desempenho na presença de padrões em níveis diferentes da série temporal. Esses parâmetros foram avaliados empiricamente utilizando várias séries temporais, inclusive caóticas, bem como séries temporais reais referentes a variáveis ambientais do reservatório de Itaipu, disponibilizadas pela Itaipu Binacional. Três variáveis limnológicas fortemente correlacionadas são consideradas nos experimentos de previsão: temperatura da água, temperatura do ar e oxigênio dissolvido. Uma análise de correlação é realizada para verificar se os dados previstos mantem a correlação das variáveis. Os resultados mostram que, o critério de seleção de vizinhos próximos e a função de previsão, propostos neste trabalho, são promissores / Treating data that contains sequential information is an important problem that arises during the data mining process. Time series constitute a popular class of sequential data, where records are indexed by time. The k-Nearest Neighbor - Time Series Prediction kNN-TSP method is an approximator for time series prediction problems. The main advantage of this approximator is its simplicity, and is often used in nonlinear time series analysis for prediction of seasonal time series. Although kNN-TSP often finds the best fit for nearly periodic time series forecasting, some problems related to how to determine its parameters still remain. In this work, we focus in two of these parameters: the determination of the nearest neighbours and the prediction function. To this end, we propose a simple approach to select the nearest neighbours, where time is indirectly taken into account by the similarity measure, and a prediction function which is not disturbed in the presence of patterns at different levels of the time series. Both parameters were empirically evaluated on several artificial time series, including chaotic time series, as well as on a real time series related to several environmental variables from the Itaipu reservoir, made available by Itaipu Binacional. Three of the most correlated limnological variables were considered in the experiments carried out on the real time series: water temperature, air temperature and dissolved oxygen. Analyses of correlation were also accomplished to verify if the predicted variables values maintain similar correlation as the original ones. Results show that both proposals, the one related to the determination of the nearest neighbours as well as the one related to the prediction function, are promising
124

Alterações na legislação brasileira de manejo florestal e seus efeitos na distribuição espacial e polinização de espécies madeireiras amazônicas / Changes in Brazilian forest management legislation and their effects on spatial distribution and pollination of Amazonian timber species

Sontag, Vanessa Erler 29 August 2017 (has links)
Conhecer o comportamento espacial e demográfico e a dinâmica genética das espécies madeireiras e manter uma distância entre as árvores que permita sua reprodução é essencial para o desenvolvimento de procedimentos de manejo que visem a conservação das espécies e garantia de estoques futuros de madeira. No entanto, quando uma área é explorada para fins madeireiros, as árvores remanescentes podem não ficar a uma distância viável a polinização. A legislação brasileira atual limita a exploração de espécies com baixa densidade de ocorrência e define alguns critérios para a escolha das árvores remanescentes, porém, eles levam em consideração apenas o número de indivíduos e não os fatores ecológicos e genéticos das espécies além de serem os mesmos aplicados a toda Amazônia. O objetivo deste trabalho foi analisar o comportamento espacial de três espécies madeireiras, a Manilkara huberi, a Hymenaea courbaril e o Handroanthus serratifolius, em quatro áreas de estudo na Amazônia brasileira a partir de inventários de empresas florestais e verificar a implicação das últimas mudanças ocorridas na legislação no processo de polinização dessas espécies. O trabalho foi dividido em duas partes. A primeira verificou se essas três espécies possuem o mesmo padrão espacial em diferentes regiões da Amazônia e discutiu a questão da raridade presente na legislação. Foi calculada a densidade e a matriz do vizinho mais próximo para todos os indivíduos antes do corte das três espécies em cada área de estudo e as distâncias plotadas em um gráfico quantil-quantil. Os resultados mostraram que a Manilkara huberi é uma espécie que pode ser encontrada em alta ou baixa densidade e em agregados ou não dependendo da região de ocorrência, diferente do Handroanthus serratifolius que apresenta uma densidade e padrão de distribuição semelhante independente da região de ocorrência. A Hymenaea courbaril permeia entre essas duas situações. Notou-se uma semelhança na distribuição das espécies entre as áreas próximas. A segunda parte analisou as consequências da alteração da legislação na distância entre as árvores remanescentes das três espécies e verificou se essa distância era viável para o processo de polinização. Foi simulado o corte a partir de cenários legislativos, em que apenas o diâmetro mínimo de corte (DMC) foi alterado. Os resultados mostraram que houve uma diminuição na distância entre árvores. A diminuição favoreceu o processo de polinização visto que os polinizadores precisam percorrer menores distâncias na busca por alimento. A legislação tem tomado um caminho mais conservativo, porém há muito o que ser desenvolvido, visto que cada espécie possui sua própria ecologia reprodutiva mas são manejadas da mesma forma. / The information about the spatial and demographic behavior and the genetic dynamic of timber species and maintaining a distance between trees that allows their reproduction is essential for the development of management procedures to conserve species and guarantee future wood stocks. However, when an area is harvested for timber purposes, the remaining trees may not stay at a feasible distance for pollination. Current Brazilian legislation limits the exploitation of low-density species and defines some criteria for choosing the remaining trees. However, they take into account only the number of individuals and not the ecology and genetic aspects of the species. Besides, the same criteria are applied to the entire Amazon. The aim of this study was to analyze the spatial behavior of three timber species, Manilkara huberi, Hymenaea courbaril and Handroanthus serratifolius, in four study areas in the Brazilian Amazon Forest. Companies inventories were used to verify the implication of the latest changes in the Brazilian legislation on the pollination process of these species. The study was divided into two parts. The first one verified if these three species have the same spatial pattern in different regions of the Amazon and discussed the rarity issue in the legislation. The density and the nearest neighbor distance matrix were calculated for all individuals before cutting for the three species in each study area and the distances were plotted on a quantile-quantile plot. The results showed that Manilkara huberi can be found in high or low density and aggregated or not depending on the region of occurrence. On the other hand, other than Handroanthus serratifolius populations present similar densities and distribution patterns despite region of occurrence. Hymenaea courbaril permeates between these two situations. The distribution of this species among nearby areas showed similarity. The second part of this work analyzed the consequences of changes in Brazilian forest management legislation on the distance between the remaining trees of the three species and verified whether this distance was feasible for the pollination process. The cutting was simulated based on two legislative scenarios, in which only the minimum cut diameter (MCD) was changed. The results showed that there was a decrease in the distance between trees due to the increase of the density of remaining individuals. The distance decrease favored the pollination process, since pollinators need to travel shorter distances searching for food. Brazilian forest legislation has taken a more conservative path, but there is still much to be developed, since each species has its own reproductive ecology, even so are managed the same way.
125

Operação de busca exata aos K-vizinhos mais próximos reversos em espaços métricos / Answering exact reverse k-nerarest neighbors queries in metric space

Oliveira, Willian Dener de 19 March 2010 (has links)
A complexidade dos dados armazenados em grandes bases de dados aumenta cada vez mais, criando a necessidade de novas operações de consulta. Uma classe de operações que tem apresentado interesse crescente são as chamadas Consultas por Similaridade, sendo as mais conhecidas as consultas por Abrangência (\'R IND. q\') e por k-Vizinhos mais Proximos (kNN), sendo que esta ultima obtem quais são os k elementos armazenados mais similares a um dado elemento de referência. Outra consulta que é interessante tanto para consultas diretas quanto como parte de operações de análises mais complexas e a operação de consulta aos k-Vizinhos mais Próximos Reversos (RkNN). Seu objetivo e obter todos os elementos armazenados que têm um dado elemento de referência como um dos seus k elementos mais similares. Devido a complexidade de execução da operação de RkNN, a grande maioria das soluções existentes restringem-se a dados representados em espaços multidimensionais euclidianos (nos quais estão denidas tambem operações cardinais e topológicas, além de se considerar a similaridade como sendo a distância Euclidiana entre dois elementos), ou então obtém apenas respostas aproximadas, sujeitas a existência de falsos negativos. Várias aplicações de análise de dados científicos, médicos, de engenharia, financeiros, etc. requerem soluções eficientes para o problema da operação de RkNN sobre dados representados em espaços métricos, onde os elementos não podem ser considerados estar em um espaço nem Euclidiano nem multidimensional. Num espaço métrico, além dos próprios elementos armazenados existe apenas uma função de comparação métrica entre pares de objetos. Neste trabalho, são propostas novas podas de espaço de busca e o algoritmo RkNN-MG que utiliza essas novas podas para solucionar o problema de consultas RkNN exatas em espaços métricos sem limitações. Toda a proposta supõe que o conjunto de dados esta em um espaço métrico imerso isometricamente em espaço euclidiano e utiliza propriedades da geometria métrica válida neste espaço para realizar podas eficientes por lei dos cossenos combinada com as podas tradicionais por desigualdade triangular. Os experimentos demonstram comparativamente que as novas podas são mais eficientes que as tradicionais podas por desigualdade triangular, tendo desempenhos equivalente quando comparadas em conjuntos de alta dimensionalidade ou com dimensão fractal alta. Assim, os resultados confirmam as novas podas propostas como soluções alternativas eficientes para o problema de consultas RkNN / Data stored in large databases present an ever increasing complexity, pressing for the development of new classes of query operators. One such class, which is enticing an increasing interest, is the so-called Similarity Queries, where the most common are the similarity range queries (\'R IND. q\') and the k-nearest neighbor queries (kNN). A k-nearest neighbor query aims at retrieving the k stored elements nearer (or more similar) to a given reference element. Another important similarity query is the reverse k-nearest neighbor (RkNN), useful both for queries posed directly by the analyst and for queries that are part of more complex analysis processes. The objective of a reverse k-nearest neighbor queries is obtaining the stored elements that has the query reference element as one of their k-nearest neighbors. As the RkNN operation is a rather expensive operation, from the computational standpoint, most existing solutions only solve the query when applied over Euclidean multidimensional spaces (as these spaces also define cardinal and topological operations besides the Euclidean distance between pairs of elements) or retrieve only approximate answers, where false negatives can occur. Several applications, like the analysis of scientific, medical, engineering or financial data, require efficient and exact answers for the RkNN queries over data which is frequently represented in metric spaces, that is where no other property besides the similarity measure exists. Therefore, for applications handling metrical data, the assumption of Euclidean metric or even multidimensional data cannot be used. In this work, we propose new pruning rules based on the law of cosines, and the RkNN-MG algorithm, which uses them to solve RkNN queries in a way that is exact, faster than the existing approaches, that is not limited for any value of k, and that can be applied both over static and over dynamic datasets. The new pruning rules assume that the data set is in a metric space that can be embedded into an Euclidean space and use metric geometry properties valid in this space to perform effective pruning based on the law of cosines combined with the traditional pruning based on the triangle inequality property. The experiments show that the new pruning rules are alkways more efficient than the traditional pruning rules based solely on the triangle inequality. The experiments show that for high high dimensionality datasets, or for metric datasets with high fractal dimensionality, the performance improvement is smaller than for for lower dimensioinality datasets, but it\'s never worse. Thus, the results confirm that the our pruning rules are efficient alternative to solve RkNN queries in general
126

Learning compact representations for large scale image search / Apprentissage de représentations compactes pour la recherche d'images à grande échelle

Jain, Himalaya 04 June 2018 (has links)
Cette thèse aborde le problème de la recherche d'images à grande échelle. Pour aborder la recherche d'images à grande échelle, il est nécessaire de coder des images avec des représentations compactes qui peuvent être efficacement utilisées pour comparer des images de manière significative. L'obtention d'une telle représentation compacte peut se faire soit en comprimant des représentations efficaces de grande dimension, soit en apprenant des représentations compactes de bout en bout. Le travail de cette thèse explore et avance dans ces deux directions. Dans notre première contribution, nous étendons les approches de quantification vectorielle structurée telles que la quantification de produit en proposant une représentation somme pondérée de codewords. Nous testons et vérifions les avantages de notre approche pour la recherche approximative du plus proche voisin sur les caractéristiques d'image locales et globales, ce qui est un moyen important d'aborder la recherche d'images à grande échelle. L'apprentissage de la représentation compacte pour la recherche d'images a récemment attiré beaucoup d'attention avec diverses approches basées sur le hachage profond proposées. Dans de telles approches, les réseaux de neurones convolutifs profonds apprennent à coder des images en codes binaires compacts. Dans cette thèse, nous proposons une approche d'apprentissage supervisé profond pour la représentation binaire structurée qui rappelle une approche de quantification vectorielle structurée telle que PQ. Notre approche bénéficie de la recherche asymétrique par rapport aux approches de hachage profond et apporte une nette amélioration de la précision de la recherche au même débit binaire. L'index inversé est une autre partie importante du système de recherche à grande échelle en dehors de la représentation compacte. À cette fin, nous étendons nos idées pour l'apprentissage de la représentation compacte supervisée pour la construction d'index inversés. Dans ce travail, nous abordons l'indexation inversée avec un apprentissage approfondi supervisé et essayons d'unifier l'apprentissage de l'indice inversé et de la représentation compacte. Nous évaluons minutieusement toutes les méthodes proposées sur divers ensembles de données accessibles au public. Nos méthodes surpassent ou sont compétitives avec l'état de l'art. / This thesis addresses the problem of large-scale image search. To tackle image search at large scale, it is required to encode images with compact representations which can be efficiently employed to compare images meaningfully. Obtaining such compact representation can be done either by compressing effective high dimensional representations or by learning compact representations in an end-to-end manner. The work in this thesis explores and advances in both of these directions. In our first contribution, we extend structured vector quantization approaches such as Product Quantization by proposing a weighted codeword sum representation. We test and verify the benefits of our approach for approximate nearest neighbor search on local and global image features which is an important way to approach large scale image search. Learning compact representation for image search recently got a lot of attention with various deep hashing based approaches being proposed. In such approaches, deep convolutional neural networks are learned to encode images into compact binary codes. In this thesis we propose a deep supervised learning approach for structured binary representation which is a reminiscent of structured vector quantization approaches such as PQ. Our approach benefits from asymmetric search over deep hashing approaches and gives a clear improvement for search accuracy at the same bit-rate. Inverted index is another important part of large scale search system apart from the compact representation. To this end, we extend our ideas for supervised compact representation learning for building inverted indexes. In this work we approach inverted indexing with supervised deep learning and make an attempt to unify the learning of inverted index and compact representation. We thoroughly evaluate all the proposed methods on various publicly available datasets. Our methods either outperform, or are competitive with the state-of-the-art.
127

A Data Mining Framework To Detect Tariff Code Circumvention In Turkish Customs Database

Bastabak, Burcu 01 September 2012 (has links) (PDF)
Customs and foreign trade regulations are made to regulate import and export activities. The majority of these regulations are applied on import procedures. The country of origin and the tariff code become important when determining the tax amount of the merchandise in importation. Anti-dumping duty is defined as a financial penalty, published by the Ministry of Economy, enforced for suspiciously low priced imports in order to protect the local industry from unfair competition. It is accrued according to tariff code and the country of origin. To avoid such an obligation in order to not to pay tax, a tariff code that is different from the original tariff code may be declared on the customs declaration which is called as &quot / Tariff Code Circumvention&quot / . To identify such misdeclarations, a physical examination of the merchandise is required. However, with limited personnel resources, the physical examination of all imported merchandise is not possible. In this study, a data mining framework is developed on Turkish customs database in order to detect &ldquo / Tariff Code Circumvention&rdquo / . For this purpose, four types of products, which are the most circumvented goods in the Turkish customs, have been chosen. First, with the help of Risk Analysis Office, the significant features are identified. Then, Infogain algorithm is used for ranking these features. Finally, KNN algorithm is applied on the Turkish customs database in order to identify the circumvented goods automatically. The results show that the framework is able to find such circumvented goods successfully.
128

Equilibrium and Non-equilibrium Monte Carlo Simulations of Microphases and Cluster Crystals

Zhang, Kai January 2012 (has links)
<p>Soft matter systems exhibiting spatially modulated patterns on a mesoscale are characterized by many long-lived metastable phases for which relaxation to equilibrium is difficult and a satisfactory thermodynamic description is missing. Current dynamical theories suffer as well, because they mostly rely on an understanding of the underlying equilibrium behavior. This thesis relates the study of two canonical examples of modulated systems: microphase and cluster crystal formers. Microphases are the counterpart to gas-liquid phase separation in systems with competing short-range attractive and long-range repulsive interactions. Periodic lamellae, cylinders, clusters, etc., are thus observed in a wide variety of physical and chemical systems, such as multiblock copolymers, oil-water surfactant mixtures, charged colloidal suspensions, and magnetic materials. Cluster crystals in which each lattice site is occupied by multiple particles are formed in systems with steep soft-core repulsive interactions. Dendrimers have been proposed as a potential experimental realization. In order to access and understand the equilibrium properties of modulated systems, we here develop novel Monte Carlo simulation methods. A thermodynamic integration scheme allows us to calculate the free energy of specific modulated phases, while a [N]pT ensemble simulation approach, in which both particle number and lattice spacing fluctuate, allows us to explore their phase space more efficiently. With these two methods, we solve the equilibrium phase behavior of five schematic modulated-phase-forming spin and particle models, including the axial next-nearest-neighbor Ising (ANNNI) model, the Ising-Coulomb (IC) model, the square-well linear (SWL) model, the generalized exponential model of index 4 (GEM-4) and the penetrable sphere model (PSM). Interesting new physics ensues. In the ANNNI layered regime, simple phases are not found to play a particularly significant role in the devil's flowers and interfacial roughening plays at most a small role. With the help of generalized order parameters, the paramagnetic-modulated critical transition of the ANNNI model is also studied. We confirm the XY universality of the paramagnetic-modulated transition and its isotropic nature. With our development of novel free energy minimization schemes, the determination of a first phase diagram of a particle-based microphase former SWL is possible. We identify the low temperature GEM-4 phase diagram to be hybrid between the Gaussian core model (GCM) and the PSM. The system additionally exhibits S-shaped doubly reentrant phase sequences as well as critical isostructural transitions between face-centered cubic (FCC) cluster solids of different integer occupancy. The fluid-solid coexistence in the PSM phase diagram presents a crossover behavior around T~0.1, below which the system approaches the hard sphere limit. Studying this regime allows us to correct and reconcile prior DFT and cell theory work around this transition.</p> / Dissertation
129

Single-Query Robot Motion Planning using Rapidly Exploring Random Trees (RRTs)

Bagot, Jonathan 20 August 2014 (has links)
Robots moving about in complex environments must be capable of determining and performing difficult motion sequences to accomplish tasks. As the tasks become more complicated, robots with greater dexterity are required. An increase in the number of degrees of freedom and a desire for autonomy in uncertain environments with real-time requirements leaves much room for improvement in the current popular robot motion planning algorithms. In this thesis, state of the art robot motion planning techniques are surveyed. A solution to the general movers problem in the context of motion planning for robots is presented. The proposed robot motion planner solves the general movers problem using a sample-based tree planner combined with an incremental simulator. The robot motion planner is demonstrated both in simulation and the real world. Experiments are conducted and the results analyzed. Based on the results, methods for tuning the robot motion planner to improve the performance are proposed.
130

Simple, Faster Kinetic Data Structures

Rahmati, Zahed 28 August 2014 (has links)
Proximity problems and point set embeddability problems are fundamental and well-studied in computational geometry and graph drawing. Examples of such problems that are of particular interest to us in this dissertation include: finding the closest pair among a set P of points, finding the k-nearest neighbors to each point p in P, answering reverse k-nearest neighbor queries, computing the Yao graph, the Semi-Yao graph and the Euclidean minimum spanning tree of P, and mapping the vertices of a planar graph to a set P of points without inducing edge crossings. In this dissertation, we consider so-called kinetic version of these problems, that is, the points are allowed to move continuously along known trajectories, which are subject to change. We design a set of data structures and a mechanism to efficiently update the data structures. These updates occur at critical, discrete times. Also, a query may arrive at any time. We want to answer queries quickly without solving problems from scratch, so we maintain solutions continuously. We present new techniques for giving kinetic solutions with better performance for some these problems, and we provide the first kinetic results for others. In particular, we provide: • A simple kinetic data structure (KDS) to maintain all the nearest neighbors and the closest pair. Our deterministic kinetic approach for maintenance of all the nearest neighbors improves the previous randomized kinetic algorithm. • An exact KDS for maintenance of the Euclidean minimum spanning tree, which improves the previous KDS. • The first KDS's for maintenance of the Yao graph and the Semi-Yao graph. • The first KDS to consider maintaining plane graphs on moving points. • The first KDS for maintenance of all the k-nearest neighbors, for any k ≥ 1. • The first KDS to answer the reverse k-nearest neighbor queries, for any k ≥ 1 in any fixed dimension, on a set of moving points. / Graduate

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