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Satellite positioning measurements are never perfectly unbiased. Due to multiple types of errors affecting the signal transmission through an open space and urban areas each positioning measurement contains certain degree of uncertainty. Satellite signal receivers also do not receive the signal continuously, but the localization information is received discretely. Sampling rate and positioning error provide uncertainty towards the various positioning algorithms used in localization, logistics and in intelligent transport systems applications. This thesis examines the effect of positioning error and sampling rate on geometric and topological map matching algorithms and on the precision of route tracking within these algorithms. Also the effects of the different network density on the performance of the algorithms are evaluated. It also creates the platform for simulation and evaluation of map matching algorithms. Map matching is the process of attaching the initial positioning measurement to the network. A number of authors presented their algorithms during past decades, which shows how complex topic the map matching is, mostly due to the changing environmental and network conditions. Geometric and topological map matching algorithms are chosen, modelled and simulated and their response to the different input combinations is evaluated. Also the recommendations for possible ITS applications are carried out in terms of proposed requirements of the receiver. The results confirm general expectation that the map matching overall improves the initial position error and that map matching serves as a form of error mitigation. Also the correlation between the increase of the original positioning error and the increase of the map matching error is universal for all the algorithms in the thesis. But the comparison of the algorithm also showed large differences between the topological and geometric algorithms and their ability to cope with distorted input data. Whereas topological algorithms were clearly performing better in scenarios with smaller initial error and smaller sampling rate, geometric matching proves to be more effective in heavily distorted or very sparsely sampled data set. That is caused mostly by the ability to easily leave the wrongly mapped position which is in these situations comparative advantage of simple geometric algorithms. Following work should concentrate on involving even more algorithms into the comparison, which would produce more valuable results. Also the simulation  of the errors using the error magnitude simulation with known an improved error modelling could increase the generalization of the results.

The main topic of this thesis concerns t-SNE, a dimensionality reduction technique that has gained much popularity for showing great capability of preserving well-separated clusters from a high-dimensional space. Our goal with this thesis is twofold. Firstly we give an introduction to the use of dimensionality reduction techniques in visualization and, following recent research, show that t-SNE in particular is successful at preserving well-separated clusters. Secondly, we perform a thorough series of experiments that give us the ability to draw conclusions about the quality of embeddings from running t-SNE on samples of data using different sampling techniques. We are comparing pure random sampling, random walk sampling and so-called hubness sampling on a dataset, attempting to find a sampling method that is consistently better at preserving local information than simple random sampling. Throughout our testing, a specific variant of random walk sampling distinguished itself as a better alternative to pure random sampling.

Neste trabalho foi realizada uma revisão bibliográfica acerca das metodologias encontradas na literatura de como são aplicados os métodos para o uso analítico de dados provenientes de pesquisas que envolvem esquemas amostrais complexos. Objetivou-se mostrar e discutir alguns estudos que avaliam o impacto de ignorar o plano amostral na análise dos dados. Foi feito também um levantamento de artigos com o objetivo de fazer um estudo de trabalhos publicados em jornais, revistas ou periódicos, cujos assuntos abordados tratam da incorporação da estrutura complexa da amostra na análise. Essa revisão evidenciou que os métodos clássicos de análise, ou seja, aqueles que supõem que os dados provém de uma amostragem aleatória simples, podem levar a resultados incorretos produzindo conclusões errôneas ou equivocadas quando os dados provém de esquemas amostrais complexos. / This work was carried out a literature review about the methodologies found in the literature of how the methods for data analytical use from research involving complex sampling schemes are applied. It was aimed to show and discuss some studies that assess the impact of ignoring the sampling scheme in the data analysis. It was also made a survey of articles in order to make a study of works published in newspapers, magazines or periodicals, which addressed issues dealing with the incorporation of the complex structure of the sample in the analysis. This review shown that the classical methods of analysis, i.e. those who assume that the data comes from a simple random sampling can lead to incorrect results producing quite erroneous and misleading conclusions when the data come from complex sample schemes.

O controle de qualidade na indústria mineira visa à extração de recursos naturais com confiabilidade e efetividade a um custo mínimo. A compreensão e a aplicação da teoria da amostragem (Theory of Sampling ou TOS), desenvolvida por Pierre Gy, de forma integrada ao gerenciamento do processo, são essenciais para alcançar esse objetivo. Por este motivo, ressalta-se a importância de expor os benefícios de uma amostragem correta a todos os níveis hierárquicos de um empreendimento mineiro, a fim de se obter o engajamento da equipe técnica e operacional, assim como o orçamento necessário para financiar treinamentos e compra de equipamentos adequados para uma amostragem precisa e acurada. Uma amostra jamais apresentará características idênticas àquelas do material de origem, devido à existência do erro fundamental de amostragem, que está associado à heterogeneidade constitucional do material. Ainda existem os demais erros que surgem no decorrer das operações de amostragem, como, por exemplo, o erro de segregação e agrupamento, associado à heterogeneidade distribucional e onde a força da gravidade assume papel preponderante. Cada etapa do processo de amostragem gera um erro que deve ser conhecido para a determinação da confiabilidade das estimativas. Neste contexto, os testes de heterogeneidade são uma ferramenta imprescindível para adquirir o conhecimento sobre a variabilidade natural da jazida e para conduzir a amostragem de uma forma correta, gerando amostras representativas. O presente trabalho estuda a heterogeneidade do minério de alumínio da região oeste do Pará, a partir dos resultados obtidos em diferentes experimentos descritos na literatura com base na teoria da amostragem. Os resultados dos experimentos permitem, então, otimizar os protocolos de amostragem, assim como determinar as massas mínimas representativas para amostras de bauxita. / Quality control in the mineral industry context is directed to extraction of natural resources with reliability, effectiveness and minimum cost. The understanding and application of the Theory of Sampling (TOS), developed by Pierre Gy, integrated with, process management are essential for reaching this objective. For this reason, it is important that all levels of personnel in a mining enterprise are made aware of the benefits of correct sampling so as to gain the engagement of the technical and operational team and equally, the necessary budget for training and purchase of appropriate equipment for sampling that is precise and accurate. Samples will never present exactly the same characteristics as the lot from which they originate because of the constitutional heterogeneity which generates the fundamental sampling error. Other errors arise in sampling operations; for example, the grouping and segregation errors related to distributional heterogeneity, where gravity assumes the most important role. Each stage of the sampling process produces an error which must be known for determining the reliability of the estimates. In this context, the heterogeneity tests are an essential tool for knowing the natural variability of the deposit, and to conduct sampling in a correct manner to generate representative samples. The present work studies the heterogeneity of the aluminum ore in western Pará, based on the results of different heterogeneity experiments described by the TOS. Results allow the optimization of sampling protocols as well as the determination of the minimum masses representative samples of bauxite.

Paralelamente à aceitação dos reservatórios de carbono florestais para mitigar o impacto do dióxido de carbono emitido à atmosfera, gera-se uma demanda de técnicas que permitam mensurar e monitorar o carbono das florestas nos projetos de desenvolvimento limpo. Os erros que provém da amostragem, são muito maiores que os associados ao processo de análise de amostras, assim, é importante desenvolver planos de amostragem adequados que permitam alcançar a precisão desejada e sem viés na informação. Desta maneira, o objetivo do estudo foi conhecer o comportamento do estoque de carbono nos solos, na fazenda Três Lagoas, localizada no Município de Angatuba, São Paulo, Brasil, área com diferente cobertura e uso de solo: Eucalipto, Pastagem e Floresta Nativa, e conhecer como o sistema de amostragem influencia as estimativas assim como o esforço amostral necessário para a determinação do estoque de carbono. Coletaram-se 406 unidades amostrais distribuídas nas profundidades 0-10 cm e 10-20 cm e por meio da estatística clássica determinou-se que o estoque de carbono é de 39,6 MgC.ha-1. O menor esforço amostral necessário foi determinado na amostragem sistemática estratificada, com uma distância de amostragem na grade de 979 m. A geoestatística foi uma ferramenta que permitiu conhecer o alcance prático da variável (650 m). Pelo valor da diferença do critério de Akaike, os modelos: exponencial, Matérn com kappa 1, kappa 2 e esférico foram iguais. Difere entre eles o alcance prático que cada modelo determinou. O modelo esférico apresentou o maior alcance prático e o menor esforço amostral comparado aos outros modelos. Conclui-se que existem diferenças nos sistemas de amostragem empregados, os quais dependem das variáveis de estudo, da profundidade e do uso do solo. Tanto a estatística clássica quanto a geoestatística mostraram ser ferramentas úteis na predição do estoque de carbono em solos. / As the forestry carbon pools are accepted to mitigate the impact of carbon dioxide, a technical demand appears looking to measure and monitor the forest carbon inside clean development projects. The errors coming from sampling are bigger than those associated to the sample analysis process; therefore, its important to develop proper sampling plans that allow reaching accuracy without information bias. This way, the study developed inside Tres Lagoas Farm, in Angatuba, Sao Paulo, Brazil, aims to know the soil carbon stock behavior inside an area with different soil usage and occupation: eucalyptus, pasture and native forest, to know how the sampling system influences the estimative and the sampling efforts needed to carbon stock estimation. Using classical statistics was found that the carbon stock is 39,6 MgC.ha-1 coming from 406 sample units in a 0-10 cm and 10-20 cm depth. The less sampling effort needed was established by a stratified systematic sampling, with a sampling distance of 979m. Geostatistics was an important tool that allows knowing the variable practical range, (650 m). The models: exponential, Matérn with kappa 1, kappa 2 and spherical were the same by the Akaike criterion difference value. Among them, the difference is the practical range that each model showed. The spherical model showed the higher practical range and the less sampling effort compared to the other models used in this study. Concluding, there are differences among the used sampling systems, because they depend on the study, depth and soil usage variables. Classical statistics and geostatistics seemed to be useful tools on the prediction of soil carbon stock.

« Les gens qui parlent ensemble votent ensemble ». En écrivant ces quelques mots, le sociologue britannique William Miller résumait, à la fin des années 1970, une tradition de recherche déjà ancienne : le vote, en tant qu‟expérience de groupe, se joue d‟abord dans les rapports que les citoyens ordinaires entretiennent avec ceux avec qui ils vivent quotidiennement. La recherche présentée dans cette thèse propose de réinterroger cette hypothèse par l‟intermédiaire d‟une enquête visant à saisir comment le contexte social d‟appartenance – entendu comme l‟entourage relationnel d‟un individu - structure la pratique des échanges politiques, et en quoi cette pratique peut-elle impacter les comportements électoraux individuels. L‟enquête en question a donc consisté à adapter la technique de l‟échantillonnage en boule-de-neige à la passation de questionnaires de personne à personne. Partant d‟un échantillon de base de dix personnes mobilisées à trois reprises – en 2009, 2010 et 2012 – il m‟a ainsi été possible d‟identifier des chaînes de relations grâce à la circulation de questionnaires au sein des cercles d‟interconnaissance des participants. En plus de données statistiques, l‟enquête s‟appuie sur une analyse ethnographique de la phase de construction des différents échantillons. Ce travail repose sur le postulat selon lequel les questionnaires élaborés constituent des "objets politiques", avec pour conséquence que les échanges de questionnaires au sein des populations étudiées instaurent de fait un cadre d'interactions présentant une dimension "politique". L‟étude ethnographique de la mise en oeuvre de cette passation offre ainsi l‟occasion de porter un regard original sur les moyens par lesquels des citoyens ordinaires organisent des échanges à dimension politique au sein de leurs réseaux d‟appartenance. Les résultats de cette analyse, confrontés à celle des échanges politiques plus ordinaires pratiqués au sein des contextes identifiés au cours de l‟enquête, montrent que le politique, loin d‟obéir à des logiques autonomes, prend sa source et prolonge les normes et les identités sociales produites par les groupes. La structure sociale du contexte – notamment son degré de cohésion – et sa composition en termes de ressources économiques, culturelles et politiques, déterminent le déroulement des échanges politiques et leur capacité à créer de la mobilisation et à faire en sorte que les identités collectives se traduisent en choix électoraux. / “People who talk together vote together”. By writing these few words, the British sociologist William Miller resumed, at the end of the 1970‟s, an old research tradition : voting, as a group experience, depends on the contacts that ordinary citizens maintain with those they live with everyday. The research presented in this thesis dissertation suggests questioning again this hypothesis by the mean of a survey that aims to understand how the social context of belonging – i.e. the relational surrounding of a person – shapes the practice of political exchange, and how this practice can affect individual electoral behavior. This survey consisted in an adaptation of the snowball sampling technique around the person-to-person transfer of questionnaires. Starting with a first sample of 10 people called up three times – in 2009, 2010, and 2012 – I could identify many chains of contacts by following the flow of questionnaires within circles of acquaintances of participants. Additionally with statistical data, the survey is based on an ethnographic analysis of the sampling procedure. This work is founded on the assumption that questionnaires elaborated for the survey constitute "political objects", with the consequence that the exchanges of questionnaires within the populations studied establish a setting of interactions with a political dimension. The ethnographic analysis of the elaboration of the transfer allows having an original look on the means by which ordinary citizens organize some political exchanges within the social networks they belong to. The results of this analysis, compared to the one of more ordinary exchanges practiced within social contexts identified during the survey, show that politics, far to respond to independent logics, take their origins in social norms and identities produced by groups. The social structure of context – mainly its cohesion degree – and its composition in terms of economic, cultural and political resources, determine the flow of political exchanges and their ability to create mobilization and to make possible the translation of collective identities into electoral choices.

Lattice-based cryptography has generated considerable interest in the last two decades due toattractive features, including conjectured security against quantum attacks, strong securityguarantees from worst-case hardness assumptions and constructions of fully homomorphicencryption schemes. On the other hand, even though it is a crucial part of many lattice-basedschemes, Gaussian sampling is still lagging and continues to limit the effectiveness of this newcryptography. The first goal of this thesis is to improve the efficiency of Gaussian sampling forlattice-based hash-and-sign signature schemes. We propose a non-centered algorithm, with aflexible time-memory tradeoff, as fast as its centered variant for practicable size of precomputedtables. We also use the Rényi divergence to bound the precision requirement to the standarddouble precision. Our second objective is to construct Falcon, a new hash-and-sign signaturescheme, based on the theoretical framework of Gentry, Peikert and Vaikuntanathan for latticebasedsignatures. We instantiate that framework over NTRU lattices with a new trapdoor sampler.

by Carl Ka-fai Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Includes bibliographical references. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter §1.1 --- Directional Data and Computer Simulation --- p.1 / Chapter §1.2 --- Computer Simulation Techniques --- p.2 / Chapter §1.3 --- Implementation and Preliminaries --- p.4 / Chapter Chapter 2 --- Generating Random Points on the N-sphere --- p.6 / Chapter §2.1 --- Methods --- p.6 / Chapter §2.2 --- Comparison of Methods --- p.10 / Chapter Chapter 3 --- Generating Variates from Non-uniform Distributions on the Circle --- p.14 / Chapter §3.1 --- Introduction --- p.14 / Chapter §3.2 --- Methods for Circular Distributions --- p.15 / Chapter Chapter 4 --- Generating Variates from Non-uniform Distributions on the Sphere --- p.28 / Chapter §4.1 --- Introduction --- p.28 / Chapter §4.2 --- Methods for Spherical Distributions --- p.29 / Chapter Chapter 5 --- Generating Variates from Non-uniform Distributions on the N-sphere --- p.56 / Chapter §5.1 --- Introduction --- p.56 / Chapter §5.2 --- Methods for Higher Dimensional Spherical Distributions --- p.56 / Chapter Chapter 6 --- Summary and Discussion --- p.69 / References --- p.72 / Appendix 1 --- p.77 / Appendix 2 --- p.98

by Chi-van Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 71-72). / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- The Model and the Bayes risk --- p.7 / Chapter § 2.1 --- The Model / Chapter § 2.2 --- The Bayes risk / Chapter Chapter 3 --- The Algorithm --- p.16 / Chapter § 3.1 --- A finite algorithm / Chapter § 3.2 --- The Number Theoretical Method for Optimization / Chapter § 3.2.1 --- NTMO / Chapter § 3.2.2 --- SNTMO / Chapter Chapter 4 --- Quadratic Loss Function --- p.26 / Chapter §4.1 --- The Bayes risk / Chapter § 4.2 --- An optimal plan / Chapter § 4.3 --- Numerical Examples / Chapter Chapter 5 --- Conclusions and Comments --- p.42 / Chapter § 5.1 --- Comparison between various plans / Chapter § 5.2 --- Sensitivity Analysis / Chapter § 5.3 --- Further Developments / Tables --- p.46 / Appendix A --- p.60 / Appendix B --- p.65 / References --- p.71