Spatial interaction models of the gravity type are widely used to model origindestination flows. They draw attention to three types of variables to explain variation in spatial interactions across geographic space: variables that characterise an origin region of a flow, variables that characterise a destination region of a flow, and finally variables that measure the separation between origin and destination regions. This paper outlines and compares two approaches, the spatial econometric and the eigenfunction-based spatial filtering approach, to deal with the issue of spatial autocorrelation among flow residuals. An example using patent citation data that capture knowledge flows across 112 European regions serves to illustrate the application and the comparison of the two approaches.(authors' abstract)

Introduction. Atherosclerotic plaque rupture may occur without warning leading to severe clinical events such as heart attack and stroke. The mechanisms causing plaque rupture are not well understood. It is hypothesized that mechanical forces may play an important role in the plaque rupture process and that image-based computational mechanical analysis may provide useful information for more accurate plaque vulnerability assessment. The objectives of this dissertation are: a) develop in vivo magnetic resonance imaging (MRI)-based 3D computational models with fluid-structure Interactions (FSI) for human atherosclerotic carotid plaques; b) perform mechanical analysis using 3D FSI models to identify critical stress/strain conditions which may be used for possible plaque rupture predictions. Data, Model, and Methods. Histological, ex vivo/ in vivo MRI data of human carotid plaques were provided by the University of Washington Medical School and Washington University Medical School. Blood flow was assumed to be laminar, Newtonian, viscous and incompressible. The Navier-Stokes equations with arbitrary Lagrangian-Eulerian (ALE) formulation were used as the governing equations for the flow model. The vessel and plaque components were assumed to be hyperelastic, isotropic, nearly-incompressible and homogeneous. The nonlinear Mooney-Rivlin model was used to describe the nonlinear properties of the materials with parameter values chosen to match available experimental data. The fully-coupled FSI models were solved by a commercial finite element software ADINA to obtain full 3D flow and stress/strain distributions for analysis. Validation of the computational models and Adina software were provided by comparing computational solutions with analytic solutions and experimental data. Several novel methods were introduced to address some fundamental issues for construction of in vivo MRI-based 3D FSI models: a) an automated MRI segmentation technique using a Bayes theorem with normal probability distribution was implemented to obtain plaque geometry with enclosed components; b) a pre-shrink process was introduced to shrink the in vivo MRI geometry to obtain the no-load shape of the plaque; c) a Volume Component-Fitting Method was introduced to generate a 3D computational mesh for the plaque model with deformable complex geometry, FSI and inclusions; d) a method using MRI data obtained under in vitro pressurized conditions was introduced to determine vessel material properties. Results. The effects of material properties on flow and wall stress/strain behaviors were evaluated. The results indicate that a 100% stiffness increase may decrease maximal values of maximum principal stress (Stress-P1) and maximum principal strain (Strain-P1) by about 20% and 40%, respectively; flow Maximum-Shear-Stress (FMSS) and flow velocity did not show noticeable changes. By comparing ex vivo and in vivo data of 10 plaque samples, the average axial (25%) and inner circumferential (7.9%) shrinkages of the plaques between loaded and unloaded state were obtained. Effects of the shrink-stretch process on plaque stress/strain distributions were demonstrated based on six adjusted 3D FSI models with different shrinkages. Stress-P1 and Strain-P1 increased 349.8% and 249% respectively with 33% axial stretch. The effects of a lipid-rich necrotic core and fibrous cap thickness on structure/flow behaviors were investigated. The mean values of wall Stress-P1 and Strain-P1 from lipid nodes from a ruptured plaque were significantly higher than those from a non-ruptured plaque (112.3 kPa, 0.235 & 80.1 kPa, 0.185), which was 40.2% and 26.8% higher, respectively (p<0.001). High stress/strain concentrations were found at the thin fibrous cap regions. These results indicate that high stress concentrations and thin fibrous cap thickness might be critical indicators for plaque vulnerability. Conclusion. In vivo image-based 3D FSI models and mechanical image analysis may have the potential to provide quantitative risk indicators for plaque vulnerability assessment.

Ensemble learning is a promising direction of research in machine learning, in which an ensemble classifier gives better predictive and more robust performance for classification problems by combining other learners. Meanwhile agent-based systems provide frameworks to share knowledge from multiple agents in an open context. This thesis combines multi-agent knowledge sharing with ensemble methods to produce a new style of learning system for open environments. We now are surrounded by many smart objects such as wireless sensors, ambient communication devices, mobile medical devices and even information supplied via other humans. When we coordinate smart objects properly, we can produce a form of collective intelligence from their collaboration. Traditional ensemble methods and agent-based systems have complementary advantages and disadvantages in this context. Traditional ensemble methods show better classification performance, while agent-based systems might not guarantee their performance for classification. Traditional ensemble methods work as closed and centralised systems (so they cannot handle classifiers in an open context), while agent-based systems are natural vehicles for classifiers in an open context. We designed an open and social ensemble learning architecture, named J-model, to merge the conflicting benefits of the two research domains. The J-model architecture is based on a service choreography approach for coordinating classifiers. Coordination protocols are defined by interaction models that describe how classifiers will interact with one another in a peer-to-peer manner. The peer ranking algorithm recommends more appropriate classifiers to participate in an interaction model to boost the success rate of results of their interactions. Coordinated participant classifiers who are recommended by the peer ranking algorithm become an ensemble classifier within J-model. We evaluated J-model’s classification performance with 13 UCI machine learning benchmark data sets and a virtual screening problem as a realistic classification problem. J-model showed better performance of accuracy, for 9 benchmark sets out of 13 data sets, than 8 other representative traditional ensemble methods. J-model gave better results of specificity for 7 benchmark sets. In the virtual screening problem, J-model gave better results for 12 out of 16 bioassays than already published results. We defined different interaction models for each specific classification task and the peer ranking algorithm was used across all the interaction models. Our research contributions to knowledge are as follows. First, we showed that service choreography can be an effective ensemble coordination method for classifiers in an open context. Second, we used interaction models that implement task specific coordinations of classifiers to solve a variety of representative classification problems. Third, we designed the peer ranking algorithm which is generally and independently applicable to the task of recommending appropriate member classifiers from a classifier pool based on an open pool of interaction models and classifiers.

Spatial interaction models of the gravity type are used in conjunction with sample data on flows between origin and destination locations to analyse international and interregional trade, commodity, migration and commuting patterns. The focus is on the classical log-normal model version and spatial econometric extensions that have recently appeared in the literature. These new models replace the conventional assumption of independence between origin-destination flows with formal approaches that allow for spatial dependence in flow magnitudes. The paper also discusses problems that arise in applied practice when estimating (log-normal) spatial interaction models. (authors' abstract)

The main aim of this paper is to propose a methodology for implementation of spatial interaction models in the GIS environment. This methodology is then verified by creating functional tool for calculating potential accessibility model. The first part summarizes the available literature about those issues. The second part presents the source data and analysis methodology. ESRI ArcGIS and Python are main technologies used. Subsequently, a description of creation tool itself. In conclusion the test analyses and results are described and discussed. Powered by TCPDF (www.tcpdf.org)

Na tentativa de compreender o processo de ensino-aprendizagem no curso de graduação em Física buscaram-se elementos que fossem significativos para a elaboração de uma síntese que estabelecesse, com alguma abrangência, as principais características desse processo. Dentre várias alternativas, optou-se por uma análise do conteúdo que é estudado no curso de graduação. Para isso, foram consideradas as interações físicas, pois as investigações relativas aos vários modelos construídos pela Física para interpretá-las são muito frequentes nas diversas atividades desenvolvidas no curso de graduação. Os pressupostos teóricos, que condicionaram a escolha dos elementos para as análises do processo de ensino-aprendizagem, baseiam-se na concepção de que o conhecimento físico corresponde a construções intelectuais elaboradas por seres humanos em vários momentos históricos. Estas construções estão inscritas numa cultura, numa sociedade e numa história. A elas estão associadas diferentes visões de mundo. Os modelos para a interpretação das interações físicas foram apresentados segundo diferentes visões de mundo. A investigação das várias imagens relativas a eles fornece elementos significativos para um distanciamento de várias teorias estudadas durante o curso de graduação, possibilitando a percepção de suas totalidades e, também, da complexidade existente no conhecimento construído pela Física. Durante o curso de graduação os estudantes entram em contato com diferentes concepções sobre a natureza física através de conteúdos estudados nas várias disciplinas e estes conteúdos são reconstruídos por eles. As investigações sobre os modelos de interação construídos pelos estudantes indicaram a existência de diversas concepções que contêm os elementos estudados no curso de graduação, mas são articuladas de formas peculiares, através de composições híbridas dos conceitos aprendidos. Estes resultados indicam que, no curso de graduação em Física, faltam discussões que explicitem as significações dos conceitos e, também, as articulações existentes nas diferentes teorias. / Intending to understand the process of teaching and learning in the graduation course of Physics, we have searched for significant elements to elaborate an abstract in order to establish the principals characters at this process with some enlargement. These were many alternatives so we chose to analysis the content in the graduation course. So, we have considered the physics interactions because the investigations about many models constructed by Physics to interpret they are very frequent on the several activities that are developed in the graduation course. The elements that stipulated our choice to analysis the process of teaching and learning have its theoreticians presuppositions based in the consider that physics knowledge correspond to intellectuals constructions elaborated by human beings in many historic moments. And associated with them, there are different visions of world. The models in order to make an interpretation of the physics interactions were presented by different visions of world and the investigation about many images related with these models give us significant elements in order to keep on distance from many theories that were studied during the graduation course which make possible the perception of its totalities and also the complexity that exists in the knowledge that was constructed by Physics. During the graduation course, the students become in touch with different conceptions about the nature of Physics through contents that were studied in many subjects and they reconstruct these contents. The investigations about the interaction models constructed by students the existence of several conceptions, which content the studied elements on the graduation course, but they are articulated in peculiars forms through hybrids compositions of the learned concepts. These results indicate that in the graduation course of Physics, discussions that show the signification of concepts and also the articulations existing in different theories, are lacked.

O crescimento acelerado da produção científica brasileira nos anos recentes foi acompanhado pela expansão das colaborações científicas domésticas. Neste estudo, olhamos mais atentamente esse assunto na tentativa pioneira de identificar padrões espaciais da produção e colaboração científica no Brasil, e avaliar o papel da proximidade geográfica na determinação das interações entre os pesquisadores brasileiros. Por meio de uma base única composta por mais de um milhão de pesquisadores registrados na Plataforma Lattes e de sete milhões de publicações científicas, coletamos e consolidamos informações sobre as colaborações científicas inter-regionais em termos de redes de coautorias entre 1.347 municípios brasileiros ao longo do período compreendido entre 1990 e 2010, o que permitiu uma abrangência de dados e perspectiva de análise inéditas na literatura. Os efeitos da distância geográfica nas redes de colaboração são mensurados para as diferentes áreas do conhecimento por meio da estimação de modelos de interações espaciais. Os principais resultados sugerem fortes evidências de um processo de desconcentração espacial da produção científica nos últimos anos associado à expansão das redes de colaboração e ao aumento da participação de autores das regiões cientificamente menos tradicionais, tais como Sul e Nordeste. Ademais, também encontramos evidência de que a distância ainda desempenha papel crucial na determinação da intensidade dos fluxos de conhecimento nas redes de colaboração científica no Brasil, embora a magnitude do efeito varie entre as redes das diferentes áreas do conhecimento. Por exemplo, verificamos que o distanciamento de 200 quilômetros entre dois pesquisadores implica na redução média de 22% ou 45% na probabilidade de haver colaboração entre eles, caso eles sejam de Linguística, Letras e Artes ou Ciências Exatas e da Terra, respectivamente. / Recent years have witnessed an accelerated growth of Brazilian scientific production that was accompanied by an expansion of domestic research collaboration. In this paper we look more closely at this issue in a pioneering attempt to identify spatial patterns of research production and collaboration in Brazil, and to measure the role of geographical proximity in determining interaction between Brazilian researchers. Using a unique database comprised of over one million researchers registered in the Brazilian Lattes Platform and seven million scientific publications, we collect and consolidate information on interregional research collaboration in terms of co-authorship networks among 1,347 Brazilian cities over the period between 1990 and 2010, which enabled a range of data and analysis perspective unprecedented in literature. The effects of geographical distance on research collaboration are measured for different knowledge areas under the estimation of spatial interaction models. The main results suggest strong evidence of spatial de-concentration of scientific production in the last years with expansion of research collaboration networks and an increased participation of authors in scientifically less traditional regions, such as South and Northeast. Moreover, we also find evidence that distance still plays a crucial role in determining the intensity of knowledge flows in scientific collaboration networks in Brazil, although the magnitude of such effects varies among networks of different knowledge areas. For instance, we found that the distancing of 200 kilometers between two researchers implies an average reduction of 22% or 45% on probability of collaboration among them, if they are of Linguistics, Letters and Arts or Exact and Earth Sciences, respectively.

Na tentativa de compreender o processo de ensino-aprendizagem no curso de graduação em Física buscaram-se elementos que fossem significativos para a elaboração de uma síntese que estabelecesse, com alguma abrangência, as principais características desse processo. Dentre várias alternativas, optou-se por uma análise do conteúdo que é estudado no curso de graduação. Para isso, foram consideradas as interações físicas, pois as investigações relativas aos vários modelos construídos pela Física para interpretá-las são muito frequentes nas diversas atividades desenvolvidas no curso de graduação. Os pressupostos teóricos, que condicionaram a escolha dos elementos para as análises do processo de ensino-aprendizagem, baseiam-se na concepção de que o conhecimento físico corresponde a construções intelectuais elaboradas por seres humanos em vários momentos históricos. Estas construções estão inscritas numa cultura, numa sociedade e numa história. A elas estão associadas diferentes visões de mundo. Os modelos para a interpretação das interações físicas foram apresentados segundo diferentes visões de mundo. A investigação das várias imagens relativas a eles fornece elementos significativos para um distanciamento de várias teorias estudadas durante o curso de graduação, possibilitando a percepção de suas totalidades e, também, da complexidade existente no conhecimento construído pela Física. Durante o curso de graduação os estudantes entram em contato com diferentes concepções sobre a natureza física através de conteúdos estudados nas várias disciplinas e estes conteúdos são reconstruídos por eles. As investigações sobre os modelos de interação construídos pelos estudantes indicaram a existência de diversas concepções que contêm os elementos estudados no curso de graduação, mas são articuladas de formas peculiares, através de composições híbridas dos conceitos aprendidos. Estes resultados indicam que, no curso de graduação em Física, faltam discussões que explicitem as significações dos conceitos e, também, as articulações existentes nas diferentes teorias. / Intending to understand the process of teaching and learning in the graduation course of Physics, we have searched for significant elements to elaborate an abstract in order to establish the principals characters at this process with some enlargement. These were many alternatives so we chose to analysis the content in the graduation course. So, we have considered the physics interactions because the investigations about many models constructed by Physics to interpret they are very frequent on the several activities that are developed in the graduation course. The elements that stipulated our choice to analysis the process of teaching and learning have its theoreticians presuppositions based in the consider that physics knowledge correspond to intellectuals constructions elaborated by human beings in many historic moments. And associated with them, there are different visions of world. The models in order to make an interpretation of the physics interactions were presented by different visions of world and the investigation about many images related with these models give us significant elements in order to keep on distance from many theories that were studied during the graduation course which make possible the perception of its totalities and also the complexity that exists in the knowledge that was constructed by Physics. During the graduation course, the students become in touch with different conceptions about the nature of Physics through contents that were studied in many subjects and they reconstruct these contents. The investigations about the interaction models constructed by students the existence of several conceptions, which content the studied elements on the graduation course, but they are articulated in peculiars forms through hybrids compositions of the learned concepts. These results indicate that in the graduation course of Physics, discussions that show the signification of concepts and also the articulations existing in different theories, are lacked.

O crescimento acelerado da produção científica brasileira nos anos recentes foi acompanhado pela expansão das colaborações científicas domésticas. Neste estudo, olhamos mais atentamente esse assunto na tentativa pioneira de identificar padrões espaciais da produção e colaboração científica no Brasil, e avaliar o papel da proximidade geográfica na determinação das interações entre os pesquisadores brasileiros. Por meio de uma base única composta por mais de um milhão de pesquisadores registrados na Plataforma Lattes e de sete milhões de publicações científicas, coletamos e consolidamos informações sobre as colaborações científicas inter-regionais em termos de redes de coautorias entre 1.347 municípios brasileiros ao longo do período compreendido entre 1990 e 2010, o que permitiu uma abrangência de dados e perspectiva de análise inéditas na literatura. Os efeitos da distância geográfica nas redes de colaboração são mensurados para as diferentes áreas do conhecimento por meio da estimação de modelos de interações espaciais. Os principais resultados sugerem fortes evidências de um processo de desconcentração espacial da produção científica nos últimos anos associado à expansão das redes de colaboração e ao aumento da participação de autores das regiões cientificamente menos tradicionais, tais como Sul e Nordeste. Ademais, também encontramos evidência de que a distância ainda desempenha papel crucial na determinação da intensidade dos fluxos de conhecimento nas redes de colaboração científica no Brasil, embora a magnitude do efeito varie entre as redes das diferentes áreas do conhecimento. Por exemplo, verificamos que o distanciamento de 200 quilômetros entre dois pesquisadores implica na redução média de 22% ou 45% na probabilidade de haver colaboração entre eles, caso eles sejam de Linguística, Letras e Artes ou Ciências Exatas e da Terra, respectivamente. / Recent years have witnessed an accelerated growth of Brazilian scientific production that was accompanied by an expansion of domestic research collaboration. In this paper we look more closely at this issue in a pioneering attempt to identify spatial patterns of research production and collaboration in Brazil, and to measure the role of geographical proximity in determining interaction between Brazilian researchers. Using a unique database comprised of over one million researchers registered in the Brazilian Lattes Platform and seven million scientific publications, we collect and consolidate information on interregional research collaboration in terms of co-authorship networks among 1,347 Brazilian cities over the period between 1990 and 2010, which enabled a range of data and analysis perspective unprecedented in literature. The effects of geographical distance on research collaboration are measured for different knowledge areas under the estimation of spatial interaction models. The main results suggest strong evidence of spatial de-concentration of scientific production in the last years with expansion of research collaboration networks and an increased participation of authors in scientifically less traditional regions, such as South and Northeast. Moreover, we also find evidence that distance still plays a crucial role in determining the intensity of knowledge flows in scientific collaboration networks in Brazil, although the magnitude of such effects varies among networks of different knowledge areas. For instance, we found that the distancing of 200 kilometers between two researchers implies an average reduction of 22% or 45% on probability of collaboration among them, if they are of Linguistics, Letters and Arts or Exact and Earth Sciences, respectively.

With the increasing share of variable renewable generation, balancing electric powersystems could become a major concern for system operators because of their variableand hardly predictable nature. However, gas technologies appear as a solutionto provide this flexibility, but the impacts on the gas power system have hardly beeninvestigated. In this thesis, consulting reports on the subject matter, regulator suggestions andgas-electricity interaction models in scientific literature are studied and four sourcesare identified to be used for balancing: linepack, storage facilities, liquefied natural gasand intraday gas supply from adjacent areas. Then, a gas-electricity model for flexibility supply is designed and three case studies are simulated in order to analyze bothgas and electric power systems’ behaviors. In these case studies, electricity generation,contribution of gas sources and costs are analysed. The study concludes that critical situations on gas market that can occur, e.g. incases of large variation in the net electricity demand and limited availability of linepackand storage facilities, the need of intraday modulation can exceed the possibilities toprovide for it. Then, gas cannot be supplied to power plants during peak periods, andmore gas than necessary is used during off-peak periods. The case studies also showthat day-ahead forecast errors in variable renewable generation can be handled mucheasier than variations by the gas system but leads to higher costs.