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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.
291

Dynamique vitreuse : de l'espace de phases à l'espace réel

Bertin, Eric 29 September 2003 (has links) (PDF)
Cette thèse aborde à l'aide de modèles simples la description de la dynamique vitreuse en termes d'espace des phases et ouvre des perspectives sur la description dans l'espace réel de cette dynamique, en mettant l'accent sur les liens entre les deux approches. Nous étudions d'abord certaines propriétés de la dynamique vitreuse dans l'espace des phases, comme la transition entre régimes entropique et activé ou l'ultramétricité dynamique. Dans le cas où le système est contraint d'évoluer entre différents minima d'énergie potentielle formant un réseau unidimensionnel, on observe également des propriétés de diffusion anormale, de localisation dynamique, de sous-vieillissement et de réponse non linéaire. Afin de faire le lien entre espace des phases et espace réel, nous caractérisons ensuite la structure spatiale des minima d'énergie potentielle d'un modèle désordonné unidimensionnel, d'où l'on déduit une échelle de longueur qui augmente en abaissant la température. Par ailleurs, nous mettons en évidence dans un modèle sans désordre avec contraintes cinétiques une échelle de longueur liée aux hétérogénéités dynamiques. Enfin, nous illustrons certains de ces concepts sur l'étude d'un effet mémoire (``l'effet Kovacs''), qui se traduit par une non-monotonicité de la relaxation du volume (ou de l'énergie) lors d'un saut en température.
292

Ising quantum chains

Karevski, Dragi 14 December 2005 (has links) (PDF)
The aim of this article is to give a pedagogical introduction to the exact equilibrium and nonequilibrium properties of free fermionic quantum spin chains. In a first part we present in full details the canonical diagonalisation procedure and review quickly the equilibrium dynamical properties. The phase diagram is analysed and possible phase transitions are discussed. The two next chapters are concerned with the effect of aperiodicity and quenched disorder on the critical properties of the quantum chain. The remaining part is devoted to the nonequilibrium dynamical behaviour of such quantum chains relaxing from a nonequilibrium pure initial state. In particular,<br />a special attention is made on the relaxation of transverse magnetization. Two-time linear response functions and correlation functions are also considered, giving insights on the nature of the final nonequilibrium stationnary state. The possibility of aging is also discussed.
293

Multivariate fault detection and visualization in the semiconductor industry

Chamness, Kevin Andrew 28 August 2008 (has links)
Not available / text
294

Spatial analysis of sea level rise associated with climate change

Chang, Biao 20 September 2013 (has links)
Sea level rise (SLR) is one of the most damaging impacts associated with climate change. The objective of this study is to develop a comprehensive framework to identify the spatial patterns of sea level in the historical records, project regional mean sea levels in the future, and assess the corresponding impacts on the coastal communities. The first part of the study suggests a spatial pattern recognition methodology to characterize the spatial variations of sea level and to investigate the sea level footprints of climatic signals. A technique based on artificial neural network is proposed to reconstruct average sea levels for the characteristic regions identified. In the second part of the study, a spatial dynamic system model (DSM) is developed to simulate and project the changes in regional sea levels and sea surface temperatures (SST) under different development scenarios of the world. The highest sea levels are predicted under the scenario A1FI, ranging from 71 cm to 86 cm (relative to 1990 global mean sea level); the lowest predicted sea levels are under the scenario B1, ranging from 51 cm to 64 cm (relative to 1990 global mean sea level). Predicted sea levels and SST's of the Indian Ocean are significantly lower than those of the Pacific and the Atlantic Ocean under all six scenarios. The last part of this dissertation assesses the inundation impacts of projected regional SLR on three representative coastal U.S. states through a geographic information system (GIS) analysis. Critical issues in the inundation impact assessment process are identified and discussed.
295

New paradigms for approximate nearest-neighbor search

Ram, Parikshit 20 September 2013 (has links)
Nearest-neighbor search is a very natural and universal problem in computer science. Often times, the problem size necessitates approximation. In this thesis, I present new paradigms for nearest-neighbor search (along with new algorithms and theory in these paradigms) that make nearest-neighbor search more usable and accurate. First, I consider a new notion of search error, the rank error, for an approximate neighbor candidate. Rank error corresponds to the number of possible candidates which are better than the approximate neighbor candidate. I motivate this notion of error and present new efficient algorithms that return approximate neighbors with rank error no more than a user specified amount. Then I focus on approximate search in a scenario where the user does not specify the tolerable search error (error constraint); instead the user specifies the amount of time available for search (time constraint). After differentiating between these two scenarios, I present some simple algorithms for time constrained search with provable performance guarantees. I use this theory to motivate a new space-partitioning data structure, the max-margin tree, for improved search performance in the time constrained setting. Finally, I consider the scenario where we do not require our objects to have an explicit fixed-length representation (vector data). This allows us to search with a large class of objects which include images, documents, graphs, strings, time series and natural language. For nearest-neighbor search in this general setting, I present a provably fast novel exact search algorithm. I also discuss the empirical performance of all the presented algorithms on real data.
296

Imprégnation forcée de fluides dans des milieux poreux

Delbos, Aline 21 October 2010 (has links) (PDF)
Cette thèse porte sur les capacités d'extraction d'une mousse déposée sur un support poreux dans le but d'y déloger un contaminant ayant imprégné la porosité. Nous avons donc considéré l'imprégnation forcée de fluides dans un pore unique, étudiée pour deux cas particuliers : (i) lors de l'impact d'une goutte de liquide à l'aplomb d'un pore unique vertical cette situation visant à modéliser l'imprégnation du poreux par le contaminant, et (ii) lors de l'aspiration d'une mou sse liquide à travers le pore qui illustre la compétition d'aspiration entre la mousse et le poreux. Dans chaque cas, le diamètre du pore est inférieur à celui des gouttes ou des bulles.Pour le premier cas, nous nous sommes intéressés au volume et à la profondeur d'imprégnation pour des surfaces hydrophiles et hydrophobes. Nous établissons les diagrammes d'imprégnation en fonction du diamètre du pore et de la vitesse d'impact et un travail de modélisation nous permet de déterminer les limites entre les différentes régions de ces digrammes.Pour le second cas, nous montrons que lors de l'aspiration, la mousse entre dans le pore uniquement dans un domaine bien déterminé dans le diagramme fraction liquide, rapport de taille pore/bulle et débit d'aspiration. En dehors de ce domaine, l'aspiration peut faire entrer soit le gaz seul, soit le liquide seul. La encore, un travail de modélisation nous permet de prédire les limites des différentes zones du diagramme. Dans une dernière partie, nous revenons à un problème pratique d'imprégnation sur support textile et quantifions les capacités d'extraction d'une mousse dans cette configuration dans le but d'y déloger un contaminant
297

Spatial diffusion of multimedia technologies among educators a case study of Puerto Rico /

Rodríguez Benítez, Javier. January 2009 (has links)
Thesis (M.A.)--State University of New York at Binghamton, Department of Geography, 2009. / Includes bibliographical references.
298

The spatial demography of reported crime an examination of urban-rural crime articulation and associated spatio-temporal diffusion processes, U.S. 1990 - 2000 /

Porter, Jeremy Reed, January 2008 (has links)
Thesis (Ph.D.)--Mississippi State University. Department of Sociology, Anthropology, and Social Work. / Title from title screen. Includes bibliographical references.
299

O uso de modelos matemáticos como ferramenta para avaliar a distribuição espacial de insetos-praga da cultura da soja no estado do Paraná / The use of mathematical models as a tool to evaluate the spatial distribution of insects-prague of soybean culture in the state of Paraná

Telles, Aline Mara dos Santos 24 April 2017 (has links)
CAPES / Glycine max (L.) Merrill é uma das principais culturas agrícolas do país e integra um conjunto de atividades agrícolas com maior evidência no mercado mundial. Este trabalho objetiva determinar através de modelos em quais regiões do Estado Chrysodeixis includens Walker, 1858 (Lepidoptera: Erebidae), Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Erebidae), Euschistus heros Fabricius, 1794 (Hemiptera: Pentatomidae) e Nezara viridula Lineaus, 1758 (Hemiptera: Pentatomidae) tem maior ocorrência, bem como analisar possíveis influências sobre uma mudança na distribuição populacional. Foram obtidos dados oficiais relativos ao número de receitas agronômicas emitidas para cada município quanto aos principais alvos biológicos, classificação dos principais produtos utilizados e ingredientes ativos mais utilizados, através da Agência de Defesa Agropecuária do Paraná (ADAPAR), referentes à cultura da soja das safras 2014/2015 e 2015/2016. Com auxílio do aplicativo Google Earth™, coletaram-se as coordenadas geográficas (latitude e longitude), no formato UTM, de cada município. Foram calculados os percentuais de receitas emitidas (RE) de cada município, após a organização dos dados iniciou-se a manipulação destes no programa Quantum Gis® 2.16. Na seqüência, realizou-se o cálculo do percentual do número de RE por classificação dos produtos utilizados e dos ingredientes ativos, ambos para as safras 2014/15 e 2015/16. A partir do relatório das informações recebidas por meio do Sistema de Controle do Comércio e Uso de Agrotóxicos no Estado do Paraná (SIAGRO), foi possível calcular o volume em toneladas de inseticida comercializado e o volume para os ingredientes ativos com maior número de RE das safras 2014/15 e 2015/16. Foram cruzadas informações de número de RE por município e a área plantada em hectares, descrita em percentual, servindo de apoio para uma possível justificativa da distribuição dos insetos-praga estudados. A análise da distribuição das principais pragas da soja, através da emissão dos receituários agronômicos, demonstra ser uma ferramenta capaz de estimar a amplitude dessa distribuição. Observou-se que a região Oeste do Paraná teve os maiores índices de emissão de receituários agronômicos emitidos para o controle de A. gemmatalis, C. includens, E. heros e N. viridula nas duas safras (2014/15 e 2015/16). No entanto, não foi possível afirmar que houve mudanças na distribuição da população desses insetos-praga devido ao uso dos inseticidas aplicados, pois, os dados obtidos não sustentam essa afirmação. Sendo assim, são necessários estudos mais centralizados e com dados mais detalhados para afirmar as possíveis causas nas diferenças de distribuição dos insetos-praga. A técnica de modelagem e o uso de programas geoestatísticos, constitui uma alternativa potencial para a implementação de protocolos de controle, consequentemente reduzindo os impactos ambientais gerados pela aplicação excessiva e em períodos inadequados dos agrotóxicos. / Glycine max (L.) Merrill is one of the main agricultural crops of the country and it integrates a set of agricultural activities with more evidence in the world market. This work aims to determine through models in which regions of the State Chrysodeixis includens Walker, 1858 (Lepidoptera: Erebidae), Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Erebidae), Euschistus heros Fabricius, 1794 (Hemiptera: Pentatomidae) and Nezara viridula Lineaus, 1758 (Hemiptera: Pentatomidae) has a higher occurrence, as well as to analyze possible influences on a change in the population distribution. Official data were obtained regarding the number of agronomic recipes issued for each municipality regarding the main biological targets, classification of the main products used and active ingredients most used, through the Agência de Defesa Agropecuária do Paraná (ADAPAR), regarding the crop of soybeans 2014/2015 and 2015/2016. Using the Google Earth ™ application, the geographic coordinates (latitude and longitude) in the UTM format of each municipality were collected. The percentages of revenues generated (RE) of each municipality were calculated, after the organization of the data the manipulation of these data was initiated in the program Quantum Gis® 2.16. Subsequently, the percentage of RE numbers was calculated by classification of the products used and the active ingredients, both for the 2014/15 and 2015/16 crops. Based on the information received through the Sistema de Controle do Comércio e Uso de Agrotóxicos no Estado do Paraná (SIAGRO), it was possible to calculate the volume in tons of commercialized insecticide and the volume for the active ingredients with the highest number of RE 2014/15 and 2015/16 crops. Information on RE numbers per municipality was cross-referenced and the area planted in hectares, described as a percentage, was used to support a possible justification for the distribution of the pest insects studied. The analysis of the distribution of the main pests of the soybean, through the emission of the agronomic prescriptions, proves to be a tool capable of estimating the amplitude of this distribution. It was observed that the western region of Paraná had the highest rates of emission of agronomic prescriptions issued for the control of A. gemmatalis, C. includens, E. heros and N. viridula in the two harvests (2014/15 and 2015/16) . However, it was not possible to affirm that there were changes in the population distribution of these insect pests due to the use of applied insecticides, because the data obtained do not support this assertion. Therefore, more centralized studies and more detailed data are needed to ascertain the possible causes in the distribution differences of the pest insects. The modeling technique and the use of geostatistical programs constitute a potential alternative for the implementation of control protocols, consequently reducing the environmental impacts generated by excessive application and inadequate periods of pesticides.
300

Análise exploratória de dados espaciais aplicada a produtividade de milho no estado do Paraná / Exploratory analysis of spatial data applied to corn yield in the state of Paraná

Seffrin, Rodolfo 20 April 2017 (has links)
A cultura do milho é uma das atividades agrícolas mais importantes para a economia no Brasil e a utilização de modelos estatísticos pode auxiliar a tomada de decisão neste setor produtivo. O presente estudo visou identificar áreas com correlação e autocorrelação espacial para a produtividade de milho e suas variáveis preditoras (temperatura média, precipitação pluvial, radiação solar, potencialidade agrícola do solo e altitude), e também, verificar o modelo de regressão espacial mais adequado para a explicação da cultura. O estudo foi realizado utilizando dados de municípios do estado do Paraná referente a safras de verão dos anos agrícolas de 2011/2012, 2012/2013 e 2013/2014. Os softwares utilizados para a análise estatística e geração dos mapas temáticos foram o ArcMap 9.3 e GeoDa 1.6.7. A identificação da dependência espacial entre as variáveis foi realizada por meio do índice de Moran Global (Univariado e Bivariado) e o índice local de associação espacial (LISA), concluindo-se que para todos os anos e critérios de vizinhança utilizados, houve autocorrelação espacial significativa ao nível de 1% para todas as variáveis. Verificouse ainda que a temperatura média, precipitação e altitude, estão correlacionadas significativamente (P-value<5%) com a produtividade do milho em todos os anos e critérios estudados. As variáveis: radiação solar e potencialidade agrícola do solo não apresentaram correlação significativa para alguns dos anos (2012/2013) e matrizes de vizinhança (contingência queen e vizinho mais próximo). Para determinar o modelo de regressão mais apropriado para a estimativa da produtividade de milho, foi adotado o diagnóstico estatístico do modelo de regressão OLS - Ordinary Least Square, que verifica se é necessário aplicar algum modelo de regressão espacial para explicação dos dados. Para todos anos agrícolas foi recomendado a utilização do modelo de regressão espacial SAR – Spatial Lag Model, sendo que apenas para o ano agrícola 2013/2014 pode ser recomendado o modelo Spatial Error Model (CAR). A regressão espacial (SAR e CAR) adotada para a estimativa da produtividade de milho em diferentes anos, obteve melhores resultados quando comparada com os resultados da regressão que não incorpora a autocorrelação espacial dos dados (OLS). O coeficiente de determinação R², os critérios de informação bayesiano (BIC) e o máximo valor do logaritmo da função verossimilhança (Log-likelihood), apresentou melhora significativa na estimação da produtividade do milho quando utilizado SAR e CAR. / Corn cultivation is one of the most important agricultural activities for the Brazilian economy and the use of statistical models can help decision making in this productive sector. The present study aimed to identify areas with correlation and spatial autocorrelation for maize productivity and its predictive variables (mean temperature, rainfall, solar radiation, soil potential and altitude), and to verify the spatial regression model most appropriate for The explanation of culture. The study was carried out using data from municipalities in the state of Paraná referring to summer crops of the 2011/2012, 2012/2013 and 2013/2014 agricultural years. The software used for the statistical analysis and generation of thematic maps were ArcMap 9.3 and GeoDa 1.6.7. The identification of spatial dependence among variables was performed using the Moran Global Index (Univariate and Bivariate) and the local spatial association index (LISA). It was concluded that for all the years and neighborhood criteria used, there was spatial autocorrelation Significant at the 1% level for all variables. It was also verified that the average temperature, precipitation and altitude, are correlated significantly (P-value <5%) with corn yield in all years and criteria studied. The variables: solar radiation and soil agricultural potential did not present significant correlation for some of the years (2012/2013) and neighborhood matrices (queen contingency and nearest neighbor). To determine the most appropriate regression model for estimating maize productivity, the OLS - Ordinary Least Square regression model was used to verify if it is necessary to apply some spatial regression model to explain the data. For all agricultural years it was recommended to use the spatial regression model Spatial Lag Model (SLM), and only for the agricultural year 2013/2014 can the Spatial Error Model (SEM) be recommended. The spatial regression (SLM and SEM) adopted for estimating maize productivity in different years yielded better results when compared with regression results that did not incorporate spatial data autocorrelation (OLS). The coefficient of determination R², the Bayesian information criteria (BIC) and the maximum log-likelihood value, showed a significant improvement in corn productivity estimation when using SLM and SEM.

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