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Langford, William P. "A space-time flow optimization model for neighborhood evacuation." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FLangford.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2010.Thesis Advisor: Alderson, David L. Second Reader: Church, Richard L. "March 2010." Author(s) subject terms: Evacuation, Network, Flow Optimization, Space-Time network. Includes bibliographical references (p. 41-42). Also available in print.
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Hone, David M. "Time and space resolution and mixed layer model accuracy." Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/9080.
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The oceanic turbulent boundary layer is a critical region to understand for oceanic and atmospheric prediction. This thesis answers two fundamental questions: (1) what is the response of the ocean mixed layer system to transient forcing at the air sea surface? (2) what is the necessary time and space resolution in an ocean mixed layer model to resolve important transient responses? Beginning with replication of de Szoeke and Rhines' work, additional physical processes were added to include more realistic viscous dissipation and anisotropy in the three-dimensional turbulent kinetic energy (TKE) budget. These refinements resulted in modification of de Szoeke and Rhines' findings. Firstly, TKE unsteadiness is important for a minimum of 10 to the 5th power seconds. Secondly, viscous dissipation should not be approximated as simply proportional to shear production. Thirdly, entrainment shear production remains significant for a minimum of one pendulum-day. The required temporal model resolution is dependent on the phenomena to be studied. This study focused on the diurnal, synoptic, and annual cycles, which the one-hour time step of the Naval Postgraduate School model adequately resolves. The study of spatial resolution showed unexpectedly that model skill was comparable for 1 m, 10 m and even 20 m vertical grid spacing
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Ehlers, Ricardo Sandes. "Bayesian model discrimination for time series and state space models." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843599/.
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In this thesis, a Bayesian approach is adopted to handle parameter estimation and model uncertainty in autoregressive moving average (ARMA) time series models and dynamic linear models (DLM). Bayesian model uncertainty is handled in a parametric fashion through the use of posterior model probabilities computed via Markov chain Monte Carlo (MCMC) simulation techniques. Attention is focused on reversible jump Markov chain Monte Carlo (RJMCMC) samplers, which can move between models of different dimensions, to address the problem of model order uncertainty and strategies for proposing efficient sampling schemes in autoregressive moving average time series models and dynamic linear models are developed. The general problem of assessing convergence of the sampler in a dimension-changing context is addressed by computing estimates of the probabilities of moving to higher and lower dimensional spaces. Graphical and numerical techniques are used to compare different updating schemes. The methodology is illustrated by applying it to both simulated and real data sets and the results for the Bayesian model selection and parameter estimation procedures are compared with the classical model selection criteria and maximum likelihood estimation.
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Mellor, Dale. "The modified turning bands (MTB) model for space-time rainfall." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357808.
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Granholm, George Richard 1976. "Near-real time atmospheric density model correction using space catalog data." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/44899.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.Includes bibliographical references (p. 179-184).
Several theories have been presented in regard to creating a neutral density model that is corrected or calibrated in near-real time using data from space catalogs. These theories are usually limited to a small number of frequently tracked "calibration satellites" about which information such as mass and crosssectional area is known very accurately. This work, however, attempts to validate a methodology by which drag information from all available low-altitude space objects is used to update any given density model on a comprehensive basis. The basic update and prediction algorithms and a technique to estimate true ballistic factors are derived in detail. A full simulation capability is independently verified. The process is initially demonstrated using simulated range, azimuth, and elevation observations so that issues such as required number and types of calibration satellites, density of observations, and susceptibility to atmospheric conditions can be examined. Methods of forecasting the density correction models are also validated under different atmospheric conditions.
by George Richard Granholm.
S.M.
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Mukherjee, Smarajit. "Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384.
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Kotecha, Vinay. "Solitons on lattices and curved space-time." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3845/.
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This thesis is concerned with solitons (solutions of certain nonlinear partial differential equations) in certain cases when the underlying space is either a lattice or curved. Chapter 2 of the thesis is concerned with the outcome of collisions between a kink (a 1-dimensional soliton) and an antikink for certain topological discrete (TD) systems. The systems considered are the TD sine-Gordon and the TD ø(^4) For the TD sine-Gordon system it is found that the kink can support an internal shape mode which plays an important role during the collisions. In particular, this mode can be excited during collisions and this leads to spectacular resonance effects. The outcome of any particular collision has sensitive dependence on the initial conditions and could be either a trapped kink-antikink state, a "reflection" or a "transmission”. Such resonance effects are already known to exist for the conventional discrete ø(^4) system, and the TD ø(^4) system is no different, though the results for the two are not entirely similar. Chapter 3 considers the question of the existence of explicit travelling kink solutions for lattice systems. In particular, an expression for such a solution for the integrable lattice sine-Gordon system is derived. In Chapter 4, by reducing the Yang-Mills equations on the (2 + 2)-dimensional ultrahyperbolic space-time, an integrable Yang-Mills-Higgs system on (2 + 1) dimensional de Sitter space-time is derived. It represents the curved space-time version of the Bogomolny equations for monopoles on R(^3) . Using twister methods, various explicit solutions with gauge groups U(l) and SU(2) are constructed. A multi-solution SU(2) solution is also presented.
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Guadagnin, Fábio. "Identidades espaço-temporais em Terra de Areia/RS : um estudo sobre o tempo e a geografia." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15274.
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A utilização do conceito de tempo como uma categoria de análise em Geografia não é tão rara quanto se imagina, mas tampouco é tão presente e reflexiva quanto se gostaria. Ainda mais raros são os trabalhos de pesquisa que incluem de maneira efetiva a dimensão espaçotemporal na análise geográfica. Esta pesquisa apresenta, portanto, uma discussão em torno de autores que analisam esta perspectiva, na tentativa de construir os conceitos de espaço-tempo, temporalidade (velocidade de transporte de matéria e informação) e identidade espaçotemporal, ao mesmo tempo em que tenta articulá-los ao universo conceitual da Geografia. Adicionalmente, esta pesquisa também tenta demonstrar uma possibilidade de uso efetivo destes conceitos na análise de um recorte espacial específico. O trabalho de campo experimental foi desenvolvido na cidade de Terra de Areia, no Litoral Norte do Rio Grande do Sul, onde diversos fluxos lentos e rápidos convivem proximamente, gerando conflitos temporais manifestados nos hábitos, gestos e sentimentos dos habitantes da localidade.The use of the concept of time as a category of analysis in Geography is not as rare as we imagine, but neither is as reflexive or common as we would like it to be. Even more rare are the scientific works that include in an effective way the space-time dimension in geographical analysis. This research presents, therefore, a discussion about authors who discuss this perspective, in trying to build the concepts of space-time, temporality (matter and information transport speed) and spatial-temporal identity at the same time that tries to link them to the conceptual universe of Geography. Also, this research tries to demonstrate a possibility of effective use of these concepts in the analysis of a specific portion of space. The experimental field work was developed in the city of Terra de Areia, in the northern coast of Rio Grande do Sul/Brazil, where several flows with different speeds live closely, generating temporal conflicts manifested in habits, gestures and feelings of the inhabitants of the town.
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Boguta, Maria. "A New Space-Time Model for Interacting Agents in the Financial Market." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-3180.
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In this thesis we present a new space-time model of interacting agents in the financial market. It is a combination of the Curie-Weiss model and a model introduced by Järpe. We investigate properties such as the critical temperature and magnetization of the system. The distribution of the Hamiltonian function is obtained and a hypothesis test of independence is derived. The results are illustrated in an example based on real data.
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Parashkevov, Atanas. "Advances in space and time efficient model checking of finite state systems." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09php223.pdf.
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Bibliography: leaves 211-220 This thesis examines automated formal verification techniques and their associated space and time implementation complexity when applied to finite state concurrent systems. The focus is on concurrent systems expressed in the Communicating Sequential Processes (CSP) framework. An approach to the compilation of CSP system descriptions into boolean formulae in the form of Ordered Binary Decision Diagrams (OBDD) is presented, further utilised by a basic algorithm that checks a refinement or equivalence relation between a pair of processes in any of the three CSP semantic models. The performance bottlenecks of the basic refinement checking algorithms are identified and addressed with the introduction of a number of novel techniques and algorithms. Algorithms described in this thesis are implemented in the Adelaide Tefinement Checking Tool.
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Bhattacharyya, Mainak. "A model reduction approach in space and time for fatigue damage simulation." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN019/document.
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L'objet de ce projet de recherche est de prédire la durée de vie d'éléments mécaniques qui sont soumis à des phénomènes de fatigue cyclique. L'idée est de développer un schéma numérique novateur pour prédire la rupture de structures sous de tels chargements. Le modèle est basé sur la mécanique des milieux continus qui introduit des variables internes pour décrire l'évolution de l'endommagement. Le défi repose dans le traitement des cycles de chargement pour la prédiction de la durée de vie, particulièrement pour la prédiction de la durée de vie résiduelle de structures existantes. Les approches traditionnelles de l'analyse de la fatigue sont basées sur des méthodes phénoménologiques utilisant des relations empiriques. De telles méthodes considèrent des approximations simplificatrices et sont incapables de prendre en compte aisément des géométries ou des charges complexes associées à des problèmes d'ingénierie réels. Une approche basée sur la description de l'évolution thermodynamique d'un milieu continu est donc utilisée pour modéliser le comportement en fatigue. Cela permet de considérer efficacement des problèmes d'ingénierie complexe et la détérioration des propriétés du matériau due à la fatigue peut être quantifiée à l'aide de variables internes. Cependant, cette approche peut être numériquement coûteuse et, par conséquent, des approches numériques sophistiquées doivent être utilisées.La stratégie numérique sur laquelle ce projet est basé est singulière par rapport aux schémas incrémentaux en temps usuellement utilisés pour résoudre des problèmes élasto-(visco)plastique avec endommagement dans le cadre de la mécanique des milieux continus. Cette stratégie numérique appelée méthode LATIN (Large Time Increment method) est une méthode non-incrémentale qui recherche la solution de manière itérative sur l'ensemble du domaine spacio-temporel. Une importante innovation de la méthode LATIN est d'incorporer une stratégie de réduction de modèle adaptative pour réduire de manière très importante le coût numérique. La Décomposition Propre Généralisée (PGD) est une stratégie de réduction de modèle a priori qui sépare les quantités d'intérêt spacio-temporelles en deux composantes indépendantes, l'une dépendant du temps, l'autre de l'espace, et estime itérativement les approximations de ces deux composantes. L'utilisation de l'approche LATIN-PGD a montré son efficacité depuis des années pour résoudre des problèmes élasto-(visco)plastiques. La première partie de ce projet vise à étendre cette approche aux modèles incorporant de l'endommagement.Bien que l'utilisation de la PGD réduise les coûts numériques, le gain n'est pas suffisant pour permettre de résoudre des problèmes considérant un grand nombre de cycles de chargement, le temps de calcul peut être très conséquent, rendant les simulations de problèmes de fatigue intraitables même en utilisant les techniques LATIN-PGD. Cette limite peut être dépassée en introduisant une approche multi-échelle en temps, qui prend en compte l'évolution rapide des quantités d'intérêt lors d'un cycle et leur évolution lente au cours de l'ensemble des cycles. Une description type « éléments finis » en temps est proposée, où l'ensemble du domaine temporel est discrétisé en éléments temporels, et seulement les cycles nodaux, qui forment les limites des éléments, sont calculés en utilisant la technique LATIN-PGD. Puis, des fonctions de forme classiques sont utilisées pour interpoler les quantités d'intérêt à l'intérieur des éléments temporels. Cette stratégie LATIN-PGD à deux échelles permet de réduire le coût numérique de manière significative, et peut être utilisée pour simuler l'évolution de l'endommagement dans une structure soumise à un chargement de fatigue comportant un très grand nombre de cyclesThe motivation of the research project is to predict the life time of mechanical components that are subjected to cyclic fatigue phenomena. The idea herein is to develop an innovative numerical scheme to predict failure of structures under such loading. The model is based on classical continuum damage mechanics introducing internal variables which describe the damage evolution. The challenge lies in the treatment of large number of load cycles for the life time prediction, particularly the residual life time for existing structures.Traditional approaches for fatigue analysis are based on phenomenological methods and deal with the usage of empirical relations. Such methods consider simplistic approximations and are unable to take into account complex geometries, and complicated loadings which occur in real-life engineering problems. A thermodynamically consistent continuum-based approach is therefore used for modelling the fatigue behaviour. This allows to consider complicated geometries and loads quite efficiently and the deterioration of the material properties due to fatigue can be quantified using internal variables. However, this approach can be computationally expensive and hence sophisticated numerical frameworks should be used.The numerical strategy used in this project is different when compared to regular time incremental schemes used for solving elasto-(visco)plastic-damage problems in continuum framework. This numerical strategy is called Large Time Increment (LATIN) method, which is a non-incremental method and builds the solution iteratively for the complete space-time domain. An important feature of the LATIN method is to incorporate an on-the-fly model reduction strategy to reduce drastically the numerical cost. Proper generalised decomposition (PGD), being a priori a model reduction strategy, separates the quantities of interest with respect to space and time, and computes iteratively the spatial and temporal approximations. LATIN-PGD framework has been effectively used over the years to solve elasto-(visco)plastic problems. Herein, the first effort is to solve continuum damage problems using LATIN-PGD techniques. Although, usage of PGD reduces the numerical cost, the benefit is not enough to solve problems involving large number of load cycles and computational time can be severely high, making simulations of fatigue problems infeasible. This can be overcome by using a multi-time scale approach, that takes into account the rapid evolution of the quantities of interest within a load cycle and their slow evolution along the load cycles. A finite element like description with respect to time is proposed, where the whole time domain is discretised into time elements, and only the nodal cycles, which form the boundary of the time elements, are calculated using LATIN-PGD technique. Thereby, classical shape functions are used to interpolate within the time element. This two-scale LATIN-PGD strategy enables the reduction of the computational cost remarkably, and can be used to simulate damage evolution in a structure under fatigue loading for a very large number of cycles
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Karunaratne, Senani Bandara. "Modelling soil organic Carbon in space and time." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/10289.
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In recent times there is an increasing interest in the quantification of the variation in soil organic carbon (SOC) in space and time. Quantification of this variation is important since SOC is important for many soil physical, chemical and biological properties and soil processes which lead to sustainable crop production in agricultural soil. In addition, SOC also helps to reduce the impacts of climatic change if it can be stored in soil for the long term in what is called “soil carbon sequestration”. The focus of the work included in this thesis is to model the space and time variation using both statistical as well as process/mechanistic models of SOC. In process modelling of SOC, the Rothamsted carbon model (RothC model) was used to assess the spatial and temporal changes in SOC. The RothC model can be used to simulate the variation of SOC over the time using readily available spatial data. Therefore, this research has (a) tested the application of mid infra red / partial least-square regression models (MIR/PLSR models) in predicting SOC in archived soil data in combination with newly collected SOC data; (b) assessed changes in SOC using legacy soil data as the baseline survey; (c) mapped the measurable SOC fractions related to RothC model at the catchment scale; (d) simulated SOC across a catchment with the RothC model using readily available spatial data; (e) calibrated the rate constants of the RothC model at the catchment scale using Bayesian inverse modelling. The first research chapter (chapter 3) concentrates on the development of MIR/PLSR models to predict total SOC in archived soil datasets in relation to legacy soil datasets. The legacy soil information can be used to assess the temporal changes of SOC if they are considered to be the baseline survey. However, the use of legacy soil data directly for comparison will not be possible due to differences in the laboratory method used to measure SOC (analytical) and in the sampling support (see chapter 4 for more details). Therefore, an attempt was made to predict total SOC for archived soil data which corresponds to a legacy soil dataset collected in year 2000 in combination with newly collected data in year 2010. A total of eight (8) different MIR/PLSR calibration models were developed to predict SOC in archived soils. In development of these models an attempt was made to select samples (n = 24) from archived soil data using different sampling strategies which were used in combination (spiking) with the newly collected dataset for year 2010. It was found that all developed calibration models performed well based on internal cross validation. However, the independent validation results revealed sample selection through the Kernnard Stone algorithm performed best compared to other approaches, e.g. conditional latin hypercube sampling. In practical terms, it is not possible to analyse a large number of soil samples in archives with traditional lab based methods. Therefore, development of effective and practical oriented MIR/PLSR models will be cost effective and save laboratory processing time in relation to the determination of total SOC in archived soil properties. Chapter 4 is focused on the assessment of the change in SOC at the catchment scale using legacy soil data as the baseline survey. In this chapter two main approaches were used to assess the change in SOC namely; design-based inference methods and model-based inference methods. It also demonstrated “how to get design-based estimates when the sampling design is non-probabilistic” which is common for most legacy datasets. Design-based inference was carried out to see the change in SOC after calculating the 95 % confidence interval around the mean for the considered soil-land use complexes (SLU). If the 95 % confidence intervals for a considered SLU complex overlap each other, then it was concluded that the change is statistically not significant at the 0.05 probability level. In the model-based approach digital soil mapping (DSM) techniques were utilized where linear mixed models (LMM) were used to map the changes in SOC across the catchment. This chapter also reported issues with legacy soil data when they are used as the baseline survey and some of the ways to overcome those issues. Both statistical inference methods revealed that there is a drop in SOC between the two surveys (year 2000 and year 2010). However, that drop was not reported as statistically significant at the 0.05 probability level for both inference methods. Chapter 5 is focused on mapping measurable fractions of the RothC model at the catchment scale. The measurable fractions of the RothC model were predicted based on MIR spectra acquired for the 2010 dataset using newly developed MIR/PLSR models from the Australian carbon research programme (SCaRP) lead by CSIRO (2009 – 2012). Even though there are many papers related to mapping SOC there are only very few papers that are available related to mapping of SOC fractions. According to the reviewed literature this is the first time that measurable fractions of SOC related to the RothC model have been mapped. For the mapping purposes three separate LMMs were used and developed models were validated with leave-one-out-cross validation. In addition, conditional sequential Gaussian simulations were carried out to assess the uncertainties related to predicted maps. Throughout this chapter it is discussed how these DSM outputs can be used as inputs to the RothC model in order to run it spatially. Finally chapter 6 and 7 are focused on process modelling of SOC with RothC model. Chapter 6 highlights different ways of running RothC model spatially across a catchment. As the first step, the RothC model was initialized across the landscape using different initialization methods. A novel approach was tested where temporal C inputs were predicted from MODIS derived NPP data. Once data is prepared simulations across landscapes were carried out with 50 model combinations. These different model combinations consisting of different rate constants (2 levels), methods of initialization (5 levels) and sources of C inputs (5 levels) were compared (2 × 5 × 5 = 50 model combinations). It was found that different methods of initialization resulted in statistically significant initial SOC pools that are used as part of the RothC model. Further, it revealed that at the end of the simulations, (after 10 years) total SOC was statistically different at the 0.05 probability level based on different combinations. Results highlighted that there is great potential to use satellite derived products as drivers for future modelling of SOC. In chapter 7 Bayesian inverse modelling was utilized to estimate the uncertainty of the rate constants of the RothC model. The RothC model was re-programmed and calibrated in a Bayesian context using the “DREAM” algorithm. Once the posterior probability density functions (PDF) for the four (4) rate constants were obtained, they were used to carry out simulations using the entire PDF. Simulated results show the uncertainty created due to uncertainty about the model rate constants. This is an important step since process models such as RothC are widely applied to assess the impact of future climatic scenarios in relation to SOC without any calibration or assessment of uncertainties of the simulations. According to reviewed literature this is the first application of DREAM algorithm in calibration of RothC model rate constants for a catchment scale dataset.
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Silveira, Emerson Lizandro Dias. "TRANSFORMAÇÕES NA ORGANIZAÇÃO ESPACIAL DO MUNICÍPIO DE RIO PARDO RS." Universidade Federal de Santa Maria, 2009. http://repositorio.ufsm.br/handle/1/9308.
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The present thesis aims to understand the process of territorial organization of Rio Pardo County (RS) from territorial transformations throughout distinct historical
moments, since its foundation until the contemporary action of new political and economical factors which take place in the county observed. The main objectives sought here are: (a) characterize the differing marks of economic stagnation undertaken by the county along time; (b) apprehend the economic effects of the globalization process in the Gaucha economy as well as in Rio Pardo county which is responsible for transformations in traditional agricultural activities; (c) comprehend
the State role and also the public policies and private companies in Rio Pardo, that redefine new dynamics and territorial functionalities; (d) verify how such new
dynamics cause repercussion in the social and economic sectors; as well as in the culture, reorganizing the territory of the county observed. The methodology of this
study is based on the dialectic method, aiming to comprehend along time the different historical periods of development and stagnation that Rio Pardo went
through; and its social-territorial consequences. The research was carried out through a collection of primary data, such as semi-structured and open interviews
and photographic record taken during field work. All secondary data was extracted from publications of the Statistic and Geographical Brazilian Institute, from FEE
(State Economical Foundation) and Emater. The territorial organization of Rio Pardo county is the result of a historical process that is confused with Rio Grande do Sul
own history. In reason of many transformations of the social, political and economic order suffered by the gaucho territory, the city was losing importance in the political and economic scenarios; as it kept its productive base set in the traditional and animal agriculture; therefore becoming a stagnated territory with no economic dynamics able to attract investments and develop itself. Currently in reason of the new capitalist thinking in Rio Grande do Sul and different public policies towards development, it s possible to notice new dynamics taking place in the territory and causing technical, cultural, political and economical changes in Rio Pardo.A presente dissertação busca compreender o processo de organização espacial do município de Rio Pardo(RS) a partir das transformações territoriais em distintos momentos históricos, desde sua fundação, até a ação contemporânea dos novos atores econômicos e políticos que se articulam no município em estudo. Os objetivos específicos buscam: (a) caracterizar os diferentes marcos de estagnação econômica sofridos pelo município ao longo do tempo;(b) apreender os efeitos do processo de globalização na economia gaúcha e no município de Rio Pardo, o qual é responsável por transformações nas atividades agrícolas tradicionais; (c) compreender o papel do estado, das políticas públicas e das empresas privadas em Rio Pardo, os quais redefinem novas dinâmicas e funcionalidades espaciais; (d) verificar como as novas dinâmicas repercutem nos setores econômicos, sociais e na cultura, reorganizando o espaço do município em estudo. A metodologia de pesquisa embasa-se no método dialético, buscando compreender, ao longo do tempo, os diferentes períodos históricos de desenvolvimento e estagnação que Rio Pardo sofreu, bem como suas consequências sócioespaciais. A pesquisa foi realizada a partir da coleta de dados primários, tais como entrevistas semiestruturadas e abertas e registros fotográficos através de trabalho de campo. Os dados secundários foram extraídos de publicações do Instituto Brasileiro de Geografia e Estatística, da FEE (Fundação de Economia e Estatística) e Emater. A organização espacial do município de Rio Pardo é resultado de um processo histórico que confunde-se com a própria história do Rio Grande do Sul. Em função de diversas transformações de ordem econômica, política, social e cultural sofridas pelo território gaúcho, a cidade foi perdendo importância no cenário econômico e político, pois manteve sua base produtiva assentada na agropecuária tradicional, tornando-se um espaço estagnado, sem dinamismo econômico capaz de atrair investimentos e de se desenvolver. Atualmente, em função das novas lógicas capitalistas no Rio Grande do Sul e de diferentes políticas públicas desenvolvimentistas, percebem-se novas dinâmicas que se desenham no espaço e provocam mudanças econômicas, políticas, culturais e técnicas em Rio Pardo.
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Demel, Samuel Seth. "Modeling and computations of multivariate datasets in space and time." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/15578.
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Doctor of PhilosophyDepartment of Statistics
Juan Du
Spatio-temporal and/or multivariate dependence naturally occur in datasets obtained in various disciplines; such as atmospheric sciences, meteorology, engineering and agriculture. There is a great deal of need to effectively model the complex dependence and correlated structure exhibited in these datasets. For this purpose, this dissertation studies methods and application of the spatio-temporal modeling and multivariate computation. First, a collection of spatio-temporal functions is proposed to model spatio-temporal processes which are continuous in space and discrete over time. Theoretically, we derived the necessary and sufficient conditions to ensure the model validity. On the other hand, the possibility of taking the advantage of well-established time series and spatial statistics tools makes it relatively easy to identify and fit the proposed model in practice. The spatio-temporal models with some ARMA discrete temporal margin are fitted to Kansas precipitation and Irish wind datasets for estimation or prediction, and compared with some general existing parametric models in terms of likelihood and mean squared prediction error. Second, to deal with the immense computational burden of statistical inference for multi- ple attributes recorded at a large number of locations, we develop Wendland-type compactly supported covariance matrix function models and propose multivariate covariance tapering technique with those functions for computation reduction. Simulation studies and US tem- perature data are used to illustrate applications of the proposed multivariate tapering and computational gain in spatial cokriging. Finally, to study the impact of weather change on corn yield in Kansas, we develop a spatial functional linear regression model accounting for the fact that weather data were recorded daily or hourly as opposed to the yearly crop yield data and the underlying spatial autocorrelation. The parameter function is estimated under the functional data analysis framework and its characteristics are investigated to show the influential factor and critical period of weather change dictating crop yield during the growing season.
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De, Swarup. "A Bayesian Space-Time Dynamic Linear Model for Radioactivity Deposition after a Nuclear Accident." Thesis, Open University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503619.
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Yang, Yong. "Simulation the transmission of airborne infectious disease by individual space-time activity-based model." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440623.
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Bengtsson, Thomas. "Time series discrimination, signal comparison testing, and model selection in the state-space framework /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9974611.
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Zhang, Xiaohui. "Integration of a stochastic space-time rainfall model and distributed hydrologic simulation with GIS." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282409.
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This research presents an integration of a stochastic space-time rainfall model and distributed hydrologic simulation with GIS. The integrated simulation system consists of three subsystems: a stochastic space-time rainfall model, a geographical information system (GIS), and a distributed physically-based hydrologic model. The developed stochastic space-time rainfall model is capable of estimating the storm movement and simulating a random rainfall field over a study area, based on the measurement from three raingauges. An optimization-based lag-k correlation method was developed to estimate the storm movement, and a stochastic model was developed to simulate the rainfall field. A GIS tool, ARC/INFO, was integrated into this simulation system. GIS has been applied to automatically extract the spatially distributed parameters for hydrologic modeling. Digital elevation modeling techniques were used to process a high resolution digital map. A distributed physically-based hydrologic model, operated in HEC-1, simulated the stochastic, distributed, interrelated hydrological processes. The Green-Ampt equation is used for modeling the infiltration process, kinematic wave approximation for infiltration-excess overland flow, and the diffusion wave model for the unsteady channel flow. Two small nested experimental watersheds in southern Arizona were chosen as the study area where three raingauges are located. Using five recorded storm events, a series of simulations were performed under a variety of conditions. The simulation results show the model performs very well, by comparing the simulated runoff peak flow and runoff depth with the measured ones, and evaluated by the model efficiency. Both model structure and model parameter uncertainties were investigated in the sensitivity analysis. The statistical tests for the simulation results show that it is important to model stochastic rainfall with storm movement, which caused a significant change in runoff peak flow and runoff depth from that where the input is only one gage data. The sensitivity of runoff to roughness factor N and hydraulic conductivity Ks were intensively investigated. The research demonstrated this integrated system presents an improved simulation environment for the distributed hydrology.
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LUPPI, MASSIMILIANO. "Analysis of species distribution in time and space for wildlife conservation." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/138011.
Full textAbstract:
Lo scopo principale della mia tesi è l’individuazione e l’applicazione di appropriati approcci modellistici, a casi di studio riguardanti l’analisi della distribuzione delle specie, l’ecologia del paesaggio e la qualità degli habitat, all’interno di aree a differente impatto antropico o in stato di abbandono.
Nella prima parte ho analizzato gli andamenti demografici e le distribuzioni degli uccelli nidificanti in Lombardia negli agro-ecosistemi. I dati, raccolti mediante la tecnica dei punti di ascolto, derivano principalmente dal monitoraggio a lungo termine degli uccelli nidificanti in Lombardia. La distribuzione ed abbondanza delle specie è stata stimata utilizzando dei modelli additivi generalizzati (GAM). Ho valutato il tasso di variazione medio annuo per 20 specie di uccelli, tra il 1992 e il 2016, applicando il modello di crescita geometrica della popolazione. Dieci specie mostrano un declino significativo, mentre cinque specie sono in aumento. Considerando i due estremi sull’intero periodo considerato, l’allodola ha mostrato un significativo declino della popolazione, perdendo circa il 90% della popolazione iniziale, mentre la popolazione del colombaccio è aumentata di circa il 2000% dal 1992.
Successivamente, ho utilizzato il metodo delle curve di risposta per indagare i cambiamenti nella distribuzione altitudinale degli uccelli nidificanti su un lungo periodo (1982-2015) nelle Alpi centrali, e per un periodo più corto (2006-2015) per confrontare le dinamiche occorse nelle Alpi centrali ed occidentali. Durante il periodo lungo, tutte le specie hanno presentato almeno un cambiamento all’interno della loro distribuzione altitudinale. La maggior parte delle specie forestali si è espansa verso altitudini superiori ed inferiori, probabilmente stimolati da una ricrescita del bosco o da un aumento della temperatura. Quasi tutte le specie di prateria hanno contratto la parte inferiore della distribuzione altitudinale, muovendosi verso quote maggiori. Durante il periodo più corto, entrambe le aree alpine hanno mostrato un aumento delle specie con un movimento verso il basso, confermando la rilevanza di questo contrastante andamento. Le specie e i gruppi ecologici considerati rivelano delle differenze nei cambiamenti nella distribuzione altitudinale, probabilmente dovuti all’interazione tra processi locali e ad ampia scala (cambiamenti climatici ed espansione foreste).
Nella seconda e terza parte della mia tesi di dottorato, ho studiato il ruolo dell’ambiente nel determinare la distribuzione spaziale delle farfalle usando un approccio multi-scala. Ho analizzato gli effetti di diversi tipi di uso del suolo, delle caratteristiche degli habitat e delle azioni gestionali sulla ricchezza ed abbondanza delle farfalle usando dei modelli GAMM. I modelli hanno mostrato che un incremento delle superfici artificiali a scala di paesaggio portato ad una diminuzione dell’effetto positivo svolto dai prati a scala locale. Inoltre l’abbondanza di fonti nettare è il fattore più importante nel determinare la ricchezza ed abbondanza delle farfalle. Questo risultato, insieme con l’effetto negativo del numero di tagli dei prati sull’abbondanza e l’effetto positivo di uno strato erbaceo più alto, sottolinea l’importanza di adottare misure gestionali corrette degli habitat semi-naturali, per la conservazione delle farfalle ed in generale della biodiversità.The general aim of my thesis is the identification and the application of appropriate modelling approaches, concerning wildlife conservation, ranging from the analysis of species distribution and population trends, to ecological connectivity and the habitat management, within area affected by different human impact or land abandonment. The specific objectives of the project are developed in the following case studies. Species distribution modelling and population trends of breeding birds in agro-ecosystems: the case of Lombardy (Italy) We analysed the population trends and distributions of breeding birds in Lombardy, focusing on agro-ecosystem species. We collected data following a stratified random sampling design by means of point counts technique. Species distribution and abundance were estimated using generalised additive models (GAMs). We assessed the mean annual variation rate for 19 species, between 1992 and 2015, applying the discrete population growth model. Over the whole period, as extreme values at regional scale, the Skylark showed a significant population decline, losing about the 90% of initial population, while the Common Wood Pigeon presented a fourfold increase. Long- and medium-term changes in the altitudinal distribution of breeding birds in the Italian Alps We used the response curve shape method to investigate changes in altitudinal distributions of breeding birds over a long-term period (1982-2015) in the central Alps, and over a medium-term period (2006-2015) to compare the dynamics occurred in the central and western Alps. During the long-term period, all species exhibited changes in at least one part of their altitudinal distribution. Most woodland species expanded towards higher and lower altitudes, probably stimulated by forest regrowth and/or temperature increase. Almost all alpine grassland species retracted the lower portion of their altitudinal range, moving towards the summit. During the medium-term period, both alpine areas showed an increase in species moving downwards, which confirms the relevance of this apparently contrasting pattern. Ecological connectivity assessment in a strongly structured fire salamander (Salamandra salamandra) population The aim of this study was to assess the ecological connectivity of fire salamander populations by means of a landscape genetic approach. The degree of isolation between populations could be evaluated measuring their genetic distances, which depend on the respective geographic (isolation by distance, IBD) and/or ecological (isolation by resistance, IBR) distances. The latter were calculated using the circuit theory, applied to habitat suitability maps. Mantel tests between distance matrices highlighted how the genetic distance in Prealpine and Eastern foothill lowland populations was related to geographic distance, while it was explained by the ecological distance, in fragmented populations of Western foothill lowland. Local and landscape drivers of butterfly richness and abundance in a human-dominated area We analysed the effects of habitat variables (local scale) and land-use variables (local and landscape scale) on butterfly richness and abundance using GAMM models. The local scale habitat models showed that the abundance of nectar plants is the most important driver of species richness and abundance. This result, together with the negative effect of the number of cuts of meadows on butterfly abundance and the positive effect of the taller herbaceous layer, highlighted the importance to adopt correct management measures in semi-natural habitats. Considering the land-use models an increase of artificial surfaces at the landscape scale leaded to a decrease of the positive effect played by meadows at local scale, which is one of the primary habitats for butterflies.
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Frederick, Lorinda A. "Deterrence and space-based missile defense /." Maxwell AFB, Ala. : School of Advanced Air and Space Studies, 2008. https://www.afresearch.org/skins/rims/display.aspx?moduleid=be0e99f3-fc56-4ccb-8dfe-670c0822a153&mode=user&action=downloadpaper&objectid=2c4a986d-2074-4005-b963-1b697e841d8c&rs=PublishedSearch.
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Seidl, Christoph. "Integrated Management of Variability in Space and Time in Software Families." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-218036.
Full textAbstract:
Software Product Lines (SPLs) and Software Ecosystems (SECOs) are approaches to capturing families of closely related software systems in terms of common and variable functionality (variability in space). SPLs and especially SECOs are subject to software evolution to adapt to new or changed requirements resulting in different versions of the software family and its variable assets (variability in time). Both dimensions may be interconnected (e.g., through version incompatibilities) and, thus, have to be handled simultaneously as not all customers upgrade their respective products immediately or completely. However, there currently is no integrated approach allowing variant derivation of features in different version combinations.
In this thesis, remedy is provided in the form of an integrated approach making contributions in three areas: (1) As variability model, Hyper-Feature Models (HFMs) and a version-aware constraint language are introduced to conceptually capture variability in time as features and feature versions. (2) As variability realization mechanism, delta modeling is extended for variability in time, and a language creation infrastructure is provided to devise suitable delta languages. (3) For the variant derivation procedure, an automatic version selection mechanism is presented as well as a procedure to derive large parts of the application order for delta modules from the structure of the HFM. The presented integrated approach enables derivation of concrete software systems from an SPL or a SECO where both features and feature versions may be configured.
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Le, Coënt Adrien. "Guaranteed control synthesis for switched space-time dynamical systems." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN039/document.
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Dans le présent travail de thèse, nous souhaitons approfondir l’étude des systèmes à commutation pour des problèmes aux dérivées partielles en explorant de nouvelles pistes d’investigation, incluant notamment la question de la synthèse de contrôle garanti par décomposition de l’espace des états, la synthèse de contrôle nécessitant la réduction de modèle, le contrôle des différentes sources d’erreur sur des quantités d’intérêt, et la mesure des incertitudes sur les états et les paramètres du modèle. Nous envisageons l’utilisation de méthodes de calcul ensemblistes associées à des méthodes de réduction de modèle, ainsi que l’utilisation d’observateurs d’état pour l’estimation en ligne du systèmeIn this thesis, we focus on switched control systems described by partial differential equations, and investigate the issues of guaranteed control of such systems using state-space decomposition methods. The use of state-space decomposition methods requires model order reduction, control of the different sources of error for quantities of interest, and measure of uncertainties on the states and parameters of the system. We are considering using set-based computation methods, in association with model order reduction techniques, along with the use of state-observers for on-line estimation of the system
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CARLOS, MAURO LAWALL EVARISTO. "A STATISTICAL INVESTIGATION ON TIME SERIES MODELS FOR COUNT DATA: GARMA MODEL AND THE STATE SPACE POISSON GAMMA MODEL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10009@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO presente trabalho tem como objetivo principal investigar por meio de simulação Monte Carlo algumas propriedades estatísticas dos modelos GARMA (Generalized Autoregressive Moving Average) para séries temporais de dados de contagem. Os modelos GARMA são uma extensão dos Modelos Lineares Generalizados de McCullagh e Nelder para situações de dados dependentes, caracterizando-se pela adição de um termo extra ao preditor linear, o qual passa a incorporar termos autoregressivos (AR) e de médias móveis (MA). As propriedades estatísticas investigadas foram às condições de estacionariedade dos modelos GARMA e os critérios de identificação da ordem (p,q) dos polinômios AR e MA que definem o modelo. Os resultados encontrados indicam que os critérios AIC BIC e Hannan-Quin utilizados foram razoavelmente eficazes na identificação da ordem dos modelos e que as condições de estacionariedade estabelecidas empiricamente em termo de restrições no espaço paramétrico são bastante complexas exigindo um estudo mais detalhado. Como objetivo secundário testamos os modelo GARMA em séries reais, ajustando os modelos GARMA- Poissson e GARMA-Binomial Negativa ao número de caso de poliomielite nos EUA e ao número de infartos do miocárdio no município do Rio de Janeiro. Os resultados indicam que os modelos foram capazes de explicar, de forma econômica, a variação destas séries.
The main objective of this dissertation is to investigate, using Monte Carlo simulations, some statistical properties of GARMA (Generalized Autoregressive Moving Average ) models for time series of count data. GARMA models are extensions of the Generalized Linear Models to dependent data, in which autoregressive (AR) and/or moving average (MA) terms are incorporated into the linear predictor. The statistical properties targeted in our investigation were the model stationarity conditions and the identification criteria for selection of model orders, the lag structure (p,q) associated with the AR and MA terms. Our results suggest that AIC, BIC and Hann-Quinn criteria worked relatively well in identifying the model order, and that the conditions for stationarity established empirically in terms of parameter space restrictions were not totally conclusive, requiring further investigation. As a secondary objective we tested the model against real data, by fitting both a GARMA-Poisson and a GARMA-Negative Binomial to the series of number of cases of poliomyelitis on the US and the number of heart-attacks in Rio de Janeiro city. The results we found indicate that these models were able to explain, in a parsimonious way, the variation of both series.
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Acheson, Emily. "Predicting Disease Vector Distributions Through Space and Time Using Environmental and Vector Control Data." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32797.
Full textAbstract:
Within this thesis, I performed a systematic review of approaches to broad-scale modelling of disease vector distributions and determined the most widely used methods predict current species niches and project the models forward under future climate scenarios without temporal validation. I then provided a forward-looking summary of emerging techniques to improve the reliability and transferability of those models, including historical calibration.
I then predicted Anopheles mosquito distributions across Tanzania in 2001 (before large-scale ITN distributions) and compared this model with countrywide ITN use by 2012 to assess where the most suitable mosquito habitats were located and whether ITN rollouts in Tanzania ensured coverage of such areas. I concluded that ITNs in Tanzania did not optimally target areas most at risk of malaria. In doing so, I provided a new approach to monitoring and evaluating vector control interventions across large spatial scales.
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Brien, Jeffrey. "Mixed Emotions: Can People Feel Happy and Sad at the Same Time?" Thesis, Boston College, 2003. http://hdl.handle.net/2345/426.
Full textAbstract:
Thesis advisor: Timothy A. DuketI studied whether or not people can feel happy and sad at the same moment in time. Participants used a computerized procedure to continuously rate their feelings as they viewed backwardly masked faces designed to elicit pleasant, unpleasant, or mixed feelings. The backward masking procedure and grid were poorly calibrated as participants found all conditions to be unpleasant. Evidence is presented that participants did not perceive the mask faces as neutral. Directions for future studies are discussed
Thesis (BA) — Boston College, 2003
Submitted to: Boston College. College of Arts and Sciences
Discipline: Psychology
Discipline: College Honors Program
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Manikku, Acharige Niranjan Sanjeeva Wimalathunge. "Space-time modelling of soil moisture: prediction and forecasting for improved agricultural management." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/21122.
Full textAbstract:
Knowledge of soil moisture is crucial in every agricultural system. Accurate soil moisture estimates are valuable guides to management decisions such as crop selection and estimation of yield potential. However, soil moisture is highly variable temporally and spatially in the landscape and very challenging to monitor. Existing soil moisture monitoring approaches lack in appropriate resolution for current agricultural requirements. Therefore, this thesis develops novel space-time models for predicting and forecasting soil moisture at a 90 m spatial resolution. A water balance model (unsaturated and multi-layer) was presented to estimate soil moisture with a combination of soil moisture sensing, remote sensing and readily available geospatial data, which parameterise the soil water balance equation. The model was further improved by optimising the parameters (infiltration and evapotranspiration) and using machine learning techniques. The prediction quality was reasonable: topsoil (Concordance = 0.69, Accuracy = 0.05 cm3cm-3); subsoil (Concordance = 0.72, Accuracy = 0.04 cm3cm-3); and root-zone (Concordance = 0.75, Accuracy = 0.05 cm3cm-3). Also, three farm-scale soil moisture surveys were performed using a mobile cosmic-ray probe platform at strategic time points of the farming year. Estimates were validated with the soil moisture obtained from 0-30 cm soil layer (Concordance = 0.87, Accuracy = 0.05 cm3cm-3). Moreover, a model (stochastic plus machine learning) was presented to forecast soil moisture: one month; three months; and six months into the future. One month lead times had the greatest forecast quality (Concordance > 0.9, Accuracy < 0.02) with the forecast quality declining with longer lead times. The subsoil was more forecastable than the topsoil. Thus, these new approaches for soil moisture modelling would have real utility across agricultural regions of Australia where they are likely to be most beneficial in management of agri-food production systems.
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Björnberg, Jakob Erik. "Graphical representations of Ising and Potts models stochastic geometry of the quantum Ising model and the space-time Potts model /." Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11267.
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Björnberg, Jakob Erik. "Graphical representations of Ising and Potts models : Stochastic geometry of the quantum Ising model and the space-time Potts model." Doctoral thesis, KTH, Matematik (Inst.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11267.
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HTML clipboard Statistical physics seeks to explain macroscopic properties of matter in terms of microscopic interactions. Of particular interest is the phenomenon of phase transition: the sudden changes in macroscopic properties as external conditions are varied. Two models in particular are of great interest to mathematicians, namely the Ising model of a magnet and the percolation model of a porous solid. These models in turn are part of the unifying framework of the random-cluster representation, a model for random graphs which was first studied by Fortuin and Kasteleyn in the 1970’s. The random-cluster representation has proved extremely useful in proving important facts about the Ising model and similar models. In this work we study the corresponding graphical framework for two related models. The first model is the transverse field quantum Ising model, an extension of the original Ising model which was introduced by Lieb, Schultz and Mattis in the 1960’s. The second model is the space–time percolation process, which is closely related to the contact model for the spread of disease. In Chapter 2 we define the appropriate space–time random-cluster model and explore a range of useful probabilistic techniques for studying it. The space– time Potts model emerges as a natural generalization of the quantum Ising model. The basic properties of the phase transitions in these models are treated in this chapter, such as the fact that there is at most one unbounded fk-cluster, and the resulting lower bound on the critical value in 
. In Chapter 3 we develop an alternative graphical representation of the quantum Ising model, called the random-parity representation. This representation is based on the random-current representation of the classical Ising model, and allows us to study in much greater detail the phase transition and critical behaviour. A major aim of this chapter is to prove sharpness of the phase transition in the quantum Ising model—a central issue in the theory— and to establish bounds on some critical exponents. We address these issues by using the random-parity representation to establish certain differential inequalities, integration of which gives the results. In Chapter 4 we explore some consequences and possible extensions of the results established in Chapters 2 and 3. For example, we determine the critical point for the quantum Ising model in and in ‘star-like’ geometries.HTML clipboard Statistisk fysik syftar till att förklara ett materials makroskopiska egenskaper i termer av dess mikroskopiska struktur. En särskilt intressant egenskap är är fenomenet fasövergång, det vill säga en plötslig förändring i de makroskopiska egenskaperna när externa förutsättningar varieras. Två modeller är särskilt intressanta för en matematiker, nämligen Ising-modellen av en magnet och perkolationsmodellen av ett poröst material. Dessa två modeller sammanförs av den så-kallade fk-modellen, en slumpgrafsmodell som först studerades av Fortuin och Kasteleyn på 1970-talet. fk-modellen har sedermera visat sig vara extremt användbar för att bevisa viktiga resultat om Ising-modellen och liknande modeller. I den här avhandlingen studeras den motsvarande grafiska strukturen hos två näraliggande modeller. Den första av dessa är den kvantteoretiska Isingmodellen med transverst fält, vilken är en utveckling av den klassiska Isingmodellen och först studerades av Lieb, Schultz och Mattis på 1960-talet. Den andra modellen är rumtid-perkolation, som är nära besläktad med kontaktmodellen av infektionsspridning. I Kapitel 2 definieras rumtid-fk-modellen, och flera probabilistiska verktyg utforskas för att studera dess grundläggande egenskaper. Vi möter rumtid-Potts-modellen, som uppenbarar sig som en naturlig generalisering av den kvantteoretiska Ising-modellen. De viktigaste egenskaperna hos fasövergången i dessa modeller behandlas i detta kapitel, exempelvis det faktum att det i fk-modellen finns högst en obegränsad komponent, samt den undre gräns för det kritiska värdet som detta innebär. I Kapitel 3 utvecklas en alternativ grafisk framställning av den kvantteoretiska Ising-modellen, den så-kallade slumpparitetsframställningen. Denna är baserad på slumpflödesframställningen av den klassiska Ising-modellen, och är ett verktyg som låter oss studera fasövergången och gränsbeteendet mycket närmare. Huvudsyftet med detta kapitel är att bevisa att fasövergången är skarp—en central egenskap—samt att fastslå olikheter för vissa kritiska exponenter. Metoden består i att använda slumpparitetsframställningen för att härleda vissa differentialolikheter, vilka sedan kan integreras för att lägga fast att gränsen är skarp. I Kapitel 4 utforskas några konsekvenser, samt möjliga vidareutvecklingar, av resultaten i de tidigare kapitlen. Exempelvis bestäms det kritiska värdet hos den kvantteoretiska Ising-modellen på
, samt i ‘stjärnliknankde’ geometrier.QC 20100705
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Björnberg, Jakob Erik. "Graphical representations of Ising and Potts models : stochastic geometry of the quantum Ising model and the space-time Potts model." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/224774.
Full textAbstract:
Statistical physics seeks to explain macroscopic properties of matter in terms of microscopic interactions. Of particular interest is the phenomenon of phase transition: the sudden changes in macroscopic properties as external conditions are varied. Two models in particular are of great interest to mathematicians, namely the Ising model of a magnet and the percolation model of a porous solid. These models in turn are part of the unifying framework of the random-cluster representation, a model for random graphs which was first studied by Fortuin and Kasteleyn in the 1970's. The random-cluster representation has proved extremely useful in proving important facts about the Ising model and similar models. In this work we study the corresponding graphical framework for two related models. The first model is the transverse field quantum Ising model, an extension of the original Ising model which was introduced by Lieb, Schultz and Mattis in the 1960's. The second model is the space-time percolation process, which is closely related to the contact model for the spread of disease. In Chapter 2 we define the appropriate 'space-time' random-cluster model and explore a range of useful probabilistic techniques for studying it. The space-time Potts model emerges as a natural generalization of the quantum Ising model. The basic properties of the phase transitions in these models are treated in this chapter, such as the fact that there is at most one unbounded fk-cluster, and the resulting lower bound on the critical value in Z. In Chapter 3 we develop an alternative graphical representation of the quantum Ising model, called the random-parity representation. This representation is based on the random-current representation of the classical Ising model, and allows us to study in much greater detail the phase transition and critical behaviour. A major aim of this chapter is to prove sharpness of the phase transition in the quantum Ising model - a central issue in the theory - and to establish bounds on some critical exponents. We address these issues by using the random-parity representation to establish certain differential inequalities, integration of which give the results. In Chapter 4 we explore some consequences and possible extensions of the results established in Chapters 2 and 3. For example, we determine the critical point for the quantum Ising model in Z and in 'star-like' geometries.
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Bitto, Angela, and Sylvia Frühwirth-Schnatter. "Achieving shrinkage in a time-varying parameter model framework." Elsevier, 2019. http://dx.doi.org/10.1016/j.jeconom.2018.11.006.
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Shrinkage for time-varying parameter (TVP) models is investigated within a Bayesian
framework, with the aim to automatically reduce time-varying Parameters to staticones,
if the model is overfitting. This is achieved through placing the double gamma shrinkage
prior on the process variances. An efficient Markov chain Monte Carlo scheme is devel-
oped, exploiting boosting based on the ancillarity-sufficiency interweaving strategy. The
method is applicable both to TVP models for univariate a swell as multivariate time series.
Applications include a TVP generalized Phillips curve for EU area inflation modeling and
a multivariate TVP Cholesky stochastic volatility model for joint modeling of the Returns
from the DAX-30index.
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Silva, Rogério Marques. "ESPAÇO E TEMPO NAS MINAS DO CAMAQUÃ EM CAÇAPAVA DO SUL/RS." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/9285.
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Currently, one lives a reality where the economic issue has great importance. Facing this, the
geographical space, a product of socio-economic changes over time, can serve as an important
focus of research in what refer to such trends. In this context, it is found Minas do Camaquã,
at the municipality of Caçapava do Sul, in Rio Grande do Sul, an assembly of working towns
formed over 130 years of copper exploitation, as object of study, which purpose is to attempt
to understand the spatial changes throughout the process of copper extraction and the future
trends for this space. The methodology of the research starts up from a dialectic vision, where
in the beginning was researched the history of the site survey in order to study the different
special conformations along the copper production. Later, we tried to understand the
dynamics of space during and after the activity of mining through interviews and skilled
application of questionnaires, verifying as well the probable trends space for the coming
years. From 1942, the Brazilian Copper Company - CBC came to extract copper in the
region. From this moment on, the local landscape would include a structure formed by an
urban industrial area and a set of seven towns in addition to clubs, squares, hospitals and
others. After 50 years, the depth of copper reserves combined with low prices and Brazilian
policy of privatization, were the reasons that prompted the closing activities in 1996. From
this moment on, all the mining structure was abandoned. From about 5000 residents,
remained around 400. Whole towns have been shut down. Buildings were demolished. After
12 years form the closing of activities, one can verify that there are some ideas being worked
on, but still far from solve the needs of the city. Successive municipal governments and their
neglect with the local make today from Minas do Camaquã, a post-industrial space which
peculiarities keep resemblance to many degraded areas, like railway cities shut deactivated
and former military bases, in what refer to the underprivileged position within the production
process. The mining return face of the current studies of the geology of the region and tourist
activity because of the beautiful scenery of this region, come as opportunities to develop the
local economy.Atualmente, vive-se uma realidade onde a questão econômica possui grande importância. Diante disto, o espaço geográfico, produto das transformações sócio-econômicas ao longo do tempo, pode servir de importante foco de pesquisa no que confere a tais tendências. Neste contexto, apresenta-se as Minas do Camaquã, no município de Caçapava do Sul, no Rio Grande do Sul, um conjunto de vilas operárias formadas ao longo de 130 anos de exploração de cobre, como objeto de estudo, cujo objetivo se é a tentativa do entendimento das transformações espaciais ao longo do processo de extração de cobre verificando-se ainda as tendências futuras para este espaço. A metodologia de pesquisa parte de uma visão dialética, onde inicialmente realizou-se o levantamento da história do local a fim de se estudar as diferentes conformações espaciais ao longo da produção de cobre. Posteriormente, buscou-se através de entrevistas qualificadas e aplicação de questionários o entendimento da dinâmica espacial durante e após o término da atividade de mineração, verificando-se ainda as prováveis tendências espaciais para os próximos anos. A partir de 1942, a Companhia Brasileira do cobre - CBC passou a extrair cobre nesta região. Deste momento em diante, a paisagem local passaria a comportar uma estrutura urbana formada por uma área industrial e um conjunto de sete vilas além de clubes, praças, hospitais entre outros. Após 50 anos, a profundidade das reservas de cobre, aliada aos baixos preços do minério e a política brasileira de privatizações, foram os motivos que levaram o encerramento das atividades no ano de 1996. Deste momento em diante, toda a estrutura dos tempos de mineração foi abandonada. De aproximadamente 5000 moradores, restaram cerca de 400. Vilas inteiras foram desativadas. Prédios foram demolidos. Após 12 anos do término das atividades, pode-se verificar que existem algumas idéias sendo trabalhadas, porém ainda muito longe de sanar as necessidades da localidade. Sucessivos governos municipais e seu descaso com o local fazem hoje das Minas do Camaquã, um espaço pós-industrial cujas especificidades guardam semelhanças a muitas áreas degradadas, como cidades ferroviárias desativadas e antigas bases militares, no que confere à posição desprivilegiada dentro do processo produtivo. A volta da mineração diante dos atuais estudos da geologia da região e a atividade turística devido as belas paisagens desta região, surgem como possibilidades de dinamizar a economia local.
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Nail, Amy Jeanette. "Quantifying local creation and regional transport using a hierarchical space-time model of ozone as a function of observed NOx, a latent space-time VOC process, emissions, and meteorology." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-08092007-123658/.
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We explore the ability of a space-time model to decompose the 8-hour ozone concentration on a given day at a given site into the parts attributable to local emissions and regional transport, and ultimately to assess the efficacy of past and future emission control programs. We model ozone as created plus transported ozone plus an error term that has a seasonally varying spatial covariance. The created component uses atmospheric chemistry results to express ozone created on a given day at a given site as a function of the observed NOx concentration, the latent VOC concentration, and temperature. The ozone transported to a given day at a given site is expressed as a weighted average of the ozone observed at all sites on the previous day, where the weights are a function of wind speed and direction that appropriately distribute weight across redundant information. The latent VOC process model has a mean trend that includes emissions from various source types, temperature, a workday indicator variable, and an error term that has a seasonally varying spatial covariance. We fit the model using likelihood methods, and we compare our predictions to observations from a withheld dataset and to those predictions of CMAQ, the deterministic model used by EPA to assess emission control programs. We find that the model predictions based on the mean trend and the random deviations from this mean outperform CMAQ predictions according to multiple criteria, but predictions based on the mean trend alone underperform CMAQ predictions.
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Tang, Fan. "Structural time series clustering, modeling, and forecasting in the state-space framework." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/6002.
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This manuscript consists of two papers that formulate novel methodologies pertaining to time series analysis in the state-space framework.
In Chapter 1, we introduce an innovative time series forecasting procedure that relies on model-based clustering and model averaging. The clustering algorithm employs a state-space model comprised of three latent structures: a long-term trend component; a seasonal component, to capture recurring global patterns; and an anomaly component, to reflect local perturbations. A two-step clustering algorithm is applied to identify series that are both globally and locally correlated, based on the corresponding smoothed latent structures. For each series in a particular cluster, a set of forecasting models is fit, using covariate series from the same cluster. To fully utilize the cluster information and to improve forecasting for a series of interest, multi-model averaging is employed. We illustrate the proposed technique in an application that involves a collection of monthly disease incidence series.
In Chapter 2, to effectively characterize a count time series that arises from a zero-inflated binomial (ZIB) distribution, we propose two classes of statistical models: a class of observation-driven ZIB (ODZIB) models, and a class of parameter-driven ZIB (PDZIB) models. The ODZIB model is formulated in the partial likelihood framework. Common iterative algorithms (Newton-Raphson, Fisher Scoring, and Expectation Maximization) can be used to obtain the maximum partial likelihood estimators (MPLEs). The PDZIB model is formulated in the state-space framework. For parameter estimation, we devise a Monte Carlo Expectation Maximization (MCEM) algorithm, using particle methods to approximate the intractable conditional expectations in the E-step of the algorithm. We investigate the efficacy of the proposed methodology in a simulation study, and illustrate its utility in a practical application pertaining to disease coding.
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Wanzenböck, Iris, and Philipp Piribauer. "R&D networks and regional knowledge production in Europe. Evidence from a space-time model." WU Vienna University of Economics and Business, 2015. http://epub.wu.ac.at/4652/1/wp207.pdf.
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In this paper we estimate space-time impacts of the embeddedness in R&D networks on regional knowledge production by means of a dynamic spatial panel data model with non-linear effects for a set of 229 European NUTS-2 regions in the period 1999-2009. Embeddedness refers to the positioning in networks where nodes represent regions that are linked by joint R&D endeavours in European Framework Programmes. We observe positive immediate impacts on regional knowledge production arising from increased embeddedness in EU funded R&D networks, in particular for regions with lower own knowledge endowments. However, long-term impacts of R&D network embeddedness are comparatively small.(authors' abstract)Series: Department of Economics Working Paper Series
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ESPINOZA, SERGIO EDUARDO CONTRERAS. "STATE SPACE MODEL FOR TIME SERIES WITH BIVARIATE POISSON DISTRIBUTION: AN APPLICATION OF DURBIN-KOOPMAN METODOLOGY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5470@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOORGANIZAÇÕES DOS ESTADOS AMERICANOS
UNIVERSIDAD DEL BÍO-BÍO
Nesta tese, consideramos um modelo de espaço de estado bivariado para dados de contagem. A abordagem usada para resolver integrais não- analíticas que se apresentam no modelo é uma natural extensão da metodologia proposta por Durbin & Koopman - (DK), no sentido de que o Modelo Gaussiano Aproximador deve possuir algumas matrizes de covariâncias diagonais. Esta modificação traz a vantagem de viabilizar o uso do tratamento univariado para séries multivariadas com as recursões de Kalman, o qual, como se sabe, é mais eficiente do que o tratamento usual e facilita o uso de inicializações exatas destas mesmas recursões. O vetor de estado do modelo proposto é definido usando-se abordagem estrutural, onde os elementos do vetor de estado têm interpretação direta como tendência e sazonalidade. Apresentamos exemplos simulados e reais para ilustrar o modelo.
In this thesis we consider a state space model for bivariate observations of count data. The approach used to solve the non analytical integrals that appears as the solution of the resulting non-Gaussian filter is a natural extension of the methodology advocated by Durbin and Koopman (DK). In our approach the aproximated Gaussian Model (AGM), has a diagonal Covariance matrix, while in the original DK, this is a full matrix. This modification make it possible to use univariate Kalman recursoes to construct the AGM, resulting in a computationally more efficient solution for the estimation of a Bivariate Poisson model. This also facilitates the use of exact initialization of those recursions. The state vector is specified using the structural approach, where the state elements are components which have direct interpretation, such as trend and seasonals. In our bivariate set up the dependence between the bivariate vector of time series is accomplished by use of common components which drive both series. We present both simulation and real life examples illustrating the use of our model.
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Roelly, Sylvie, and Michel Sortais. "Space-time asymptotics of an infinite-dimensional diffusion having a long- range memory." Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2006/670/.
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We develop a cluster expansion in space-time for an infinite-dimensional system of interacting diffusions where the drift term of each diffusion depends on the
whole past of the trajectory; these interacting diffusions arise when considering the Langevin dynamics of a ferromagnetic system submitted to a disordered external magnetic field.
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Pasquali, Flavia. "State space models for the analysis and forecasting of climatic time series." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23081/.
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We analyse climatic time series with state space models in order to compute the forecast distribution. The task is challenging since the temperature series are characterised by large temporal and cross-sectional dimensions. We modify and apply the three-step method proposed in Li et al. Journal of Econometrics 2020, which exploit the cross information in order to improve prediction.
We fit the linear Gaussian state space model to different univariate time series, estimating the model parameters with the Kalman filter and computing the prediction errors. The prediction error time series are then jointly analysed by means of a dynamic factor model. The estimation procedure follows the two-step approach suggested by Doz, Giannone, and Reichlin in the context of macro-economic time series nowcasting. Finally, the simulation smoother by Durbin and Koopman allows to sample scenarios conditional on the observed time series and to reconstruct the forecast distribution.
The results we obtained are promising. They demonstrate the feasibility of the entire procedure. Our explorations involved just a climatic parameter (the maximum temperature) and a reduced sample of data (8 years on a weekly basis for twenty climatic stations) , but we preliminarily tested the whole approach on much longer time series - up to 150 years - with a richer cross-sectional structure - up to 10.000 stations - experiencing viable computational times and very promising estimation results.
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Valenti, Eduardo da Silva. "Modelo cartográfico digital temático para simulação e previsão de inundações no município de Porto Alegre - RS." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/28477.
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Desastres naturais sempre fizeram parte da vida dos seres humanos, porém nos últimos anos devido ao crescimento dos grandes centros urbanos, da dificuldade de aplicação e cumprimento de políticas de preservação ambiental e de alterações climáticas crescentes, as catástrofes naturais estão se tornando comuns, e no caso particular deste estudo os danos causados por cheias têm afetado as populações próximas aos leitos hídricos, causando prejuízos materiais, mortes, desaparecimentos, flagelados e desalojados. Para se conhecer melhor o comportamento destes eventos extremos e aumentar a segurança evitando com isto a perda de vidas e minimizando o prejuízo econômico que advém destes desastres, se faz necessário um estudo das possíveis áreas afetadas identificando os locais de risco e quantificando a criticidade de um evento de grande magnitude. Com base em estudos de eventos anteriores, como os registros de grandes enchentes, e utilizando técnicas modernas de posicionamento por GPS (Global Positioning System), processamento digital de imagens geradas por satélites e representação temática do nivelamento geométrico destas cheias, pode-se reproduzir em modelos estes eventos e quantificá-los com uma boa precisão de seus efeitos nos dias atuais. A simulação destes eventos extremos em um modelo de base confiável que, disponibilizado à defesa civil, traz um conhecimento prévio dos possíveis efeitos de uma ocorrência deste tipo, onde poderão ser planejadas rotas de fugas e ações mitigadoras, minimizando perdas de vidas e grandes prejuízos econômicos. Os mesmos modelos servem também de ferramenta de análise de impacto e planejamentos para melhoria do plano diretor de desenvolvimento social, econômico, ambiental e pesquisas na área acadêmica. Os modelos apresentados contemplam apenas uma pequena parte das possibilidades que um trabalho como este viabiliza na área da pesquisa. Os mapas temáticos com as curvas de nível, médias das enchentes registradas, área destinada à preservação ambiental da orla do rio e o mapa das regiões onde o evento extremo de 41 atingiu, ficam disponibilizados para livre utilização.Natural disasters have always been part of the human lives, but in recent years due to growth of large urban centers, the difficulty of implementation and compliance of environmental preservation policies and increasing climate change, natural disasters are becoming common, and in the particular case of this study the damage caused by floods have affected populations beds near the water resources, causing material damage, deaths, disappearances, flagellates and homeless. To better understand the behavior of these extreme events and increase safety avoiding the lives loss and minimizing the economic losses that arise from these disasters, it is necessary to study the possible affected areas identifying the risk sites and quantifying the criticality of an event of great magnitude. Based on studies of past events, as the records of large floods, and using modern techniques of GPS positioning, digital image processing generated by satellites and thematic representation of capping geometry of these floods, we can play in these models events and quantify them with a good accuracy of its effects today. The simulation of these extreme events in a confident base model that available to bring the civil defense prior knowledge of the possible effects of an event this kind, which may be planned escape routes and mitigating actions minimizing loss of life and large economic losses. The same models also serve as analysis impact tool and planning for improvement of the master plan for social development, economic, environmental and research in the academic area. The models presented cover only a small part of the possibility that a work like this enables on research area. Thematic maps with contour lines, medium flood recorded, for environmental conservation area bordering the river and the map of the regions where the extreme event of 41 hit, are available for free use.
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Wang, Guang Chao. "Modeling Waves in A Human Brain by Space-Time Conservation Element and Solution Element Method." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313571236.
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Justen, Andreas. "A time-space constrained approach for modeling travel and activity patterns." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16378.
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Gegenstand der Arbeit ist die Entwicklung eines tour-basierten Verkehrsnachfragemodells zur Abbildung von Aktivitätenketten unter Berücksichtigung von raum-zeitlichen constraints. Den theoretischen Hintergrund bildet ein hierarchisch organisierter Entscheidungsprozess, um die theoretisch möglichen Entscheidungskombinationen zu reduzieren und damit eine wahrscheinlichkeitsbasierte Berechnung zu ermöglichen. Als Beispieltour dient die Aktivitätenkette ‚Wohnen-Arbeit-Sekundäraktivität-Wohnen’, auf deren Basis auch die statistischen Analysen der Mobilitätsbefragung Santiagos durchgeführt werden. Unter Verwendung eines GIS werden so genannte ‚Suchräume’ (Aktionsräume in denen Sekundäraktivitäten durchgeführt werden) ermittelt. Ein Ergebnis der Datenanalyse sind Grenzwerte der maximalen täglichen Reisezeit für eine Reihe von Modus-Kombinationen. Die Zeitfenster von Startzeiten und Aktivitätendauer werden in Abhängigkeit sozioökonomischer Gruppen ermittelt. Die Bestimmung der Suchräume erfolgt in Abhängigkeit von Arbeitsdauer sowie Distanz zwischen Wohn- und Arbeitsort. Beide Kriterien erwiesen sich in der Analyse als statistisch signifikant. Der Vergleich zwischen Modell und Empirie (Santiagos Mobilitätsbefragung) deutet darauf hin, dass die Suchräume geeignet sind und die Mehrheit der beobachteten Zielwahlentscheidungen beinhalten. Zur Berechnung der Wahrscheinlichkeitspfade (unter Verwendung der Programmsyntax von SPSS) wird ein im Umfang auf sieben Ziele reduziertes Alternativenset pro Wohn- und Arbeitsstandort bestimmt. Dabei werden Erreichbarkeit und Attraktivität der Ziele innerhalb des Suchraumes berücksichtigt. Die erzielten Ergebnisse stützen das Argument, dass die raum-zeitlichen constraints (tägliche Reisezeit, Suchräume) eine effektive Reduktion der kombinatorischen Vielfalt zulassen. Die Erfahrungen aus der Berechnung der Beispieltour eignen sich zum Übertrag auf weitere Tour-Typen, um eine Modellierung der städtischen Gesamtverkehrsnachfrage zu ermöglichen.In this thesis we develop a tour-based approach for modeling activity and travel pattern considering time-space constraints. A hierarchical structure of choice-making builds theoretical background for the model and is based on a set of axiomatic rules. Our central argument is that the time-space constraints can be used for reducing the number of choices and, respectively, control the combinatorics associated with the probabilistic approach. The empirical analysis of our use case, a tour of type ‘Home-Work-SecondaryActivity-Home’, is based on Santiago’s travel survey. In addition, we apply GIS to estimate the so-called search spaces (potential areas where secondary activities are realized) and justify their sizes with the empirical findings. From the data analysis we identify thresholds for the tour-based maximum daily travel times considering a set of mode combinations. We define regimes of starting times and duration of activities depending on socio-economic user groups. The estimation of search spaces is realized considering the time spent at work as well as the distance between the home and work locations. Both criteria were found to be statistically significant. The comparison of modeled results with survey observations allowed concluding that the search spaces are realistic since they capture most of the observed trip destinations. For the estimation of spatial path flows of activities and trips (using SPSS programming language), we define a final choice set of no more than seven alternatives per primary location considering zone-based accessibility and land-use attractiveness. The obtained results support the argument that time-space constraints (daily travel time, search spaces) allow an effective control of combinatorial complexity. Basing on the experience obtained in process of modeling the exemplary tour, the approach can be applied to further tour types offering the possibility to estimate the entire transport demand of Santiago city.
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Nguyen, Duc M. "Controllability and Observability of the Discrete Fractional Linear State-Space Model." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2574.
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This thesis aims to investigate the controllability and observability of the discrete fractional linear time-invariant state-space model. First, we will establish key concepts and properties which are the tools necessary for our task. In the third chapter, we will discuss the discrete state-space model and set up the criteria for these two properties. Then, in the fourth chapter, we will attempt to apply these criteria to the discrete fractional model. The general flow of our objectives is as follows: we start with the first-order linear difference equation, move on to the discrete system, then the fractional difference equation, and finally the discrete fractional system. Throughout this process, we will develop the solutions to the (fractional) difference equations, which are the basis of our criteria.
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Gardner, Elvert L. ""Sowing seeds in barren soil" : why space power theory just won't grow /." Maxwell AFB, Ala. : School of Advanced Air and Space Studies, 2008. https://www.afresearch.org/skins/rims/display.aspx?moduleid=be0e99f3-fc56-4ccb-8dfe-670c0822a153&mode=user&action=downloadpaper&objectid=27104bd2-feb9-40b4-87ff-0bc531c869db&rs=PublishedSearch.
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Vikas, Sharma. "Development of Space-Time Finite Element Method for Seismic Analysis of Hydraulic Structures." Kyoto University, 2018. http://hdl.handle.net/2433/235094.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第21374号
農博第2298号
新制||農||1066(附属図書館)
学位論文||H30||N5147(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 村上 章, 教授 藤原 正幸, 教授 渦岡 良介
学位規則第4条第1項該当
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TUNINETTI, MARTA. "Water footprint assessment in space and time to support local and global sustainability." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2706873.
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Crop production vastly dominates global freshwater use, accounting for nearly 70% of the total withdrawal and around 90% of the total consumption. Human beings are currently using 30% of precipitation-recharged soil moisture and less than 10% (i.e., 3800 km3yr-1}) of the maximum available renewable freshwater resources in the word. Notwithstanding, water resource availability is highly variable in space and time, and different studies have shown a significant mismatch between water use and availability. Accordingly, two-third of global population live under conditions of sever water scarcity for at least one month per year. Moreover, as a consequence of larger food demand and changing living standards, toward more caloric and protein intense diets, global water use has increased by 6-8 times during the past century. At the same time, areas equipped for irrigation have doubled with actual irrigation having unavoidable consequences for aquifers and river ecosystems. Future scenarios of climate change are expected to worsen this picture. Indeed, the rising trends of water demand may continue in the future, harshening the conditions in areas reaching critical thresholds of acceptable water balance. In this context, the goals of this thesis are (i) to identify the main determinants of water use efficiency in agriculture; (ii) to introduce a link prediction algorithm applied to the international trade of agricultural goods; (iii) to introduce a novel indicator to monitor the (mis)match between water use and supply. This thesis quantifies the crop water footprint (CWF, or amount of water use per unit weight of crop) of nine major crops (i.e., wheat, rice, maize, soybean, barley, potatoes, sugar cane, sugar beet, and cotton) through a daily soil water balance run on a grid with a 5’x5’ spatial resolution. The model considers scenarios of rainfed and irrigated crops, also exploring multi-cropping patterns. Quantitative assessments of green and blue (separated into surface and ground) CWF are mapped and analysed in order to identify and monitor the major local drivers of water use, such as climatic conditions, precipitation rate during the growing season, cropping calendar, soil properties, crop yields and agricultural management practises. Results show that crop yield is the most important determinant of the total CWF. Moreover, results of a first-order sensitivity analysis show that, e.g., wheat CWF is mostly sensitive to the length of the growing period, rice CWF to the reference evapotranspiration depth, soybean and maize CWF to the planting date. The CWF model has been adopted also to validate a Fast Track approach, recently developed to study the CWF changes in time, which are generally kept aside in Water Footprint assessments. This approach ascribes the temporal CWF changes only to the yield variations, while it assumes the evapotranspiration depth as time-invariant. This thesis shows the good performance of this approach and also provides an uncertainty analysis. Accordingly, the Fast Track approach shows an error three times smaller than the uncertainty associated with the CWF model. Following the yields patterns, CWF has significantly decreased along the period 1961-2013, but with different rates depending on the crop and the location of the production sites. In the second part of the thesis, the crop water footprint is compared to the local water availability, to assess the sustainability of crop production. In order to understand the size of local (mis)match between crop water use and available water resources, we introduce a water debt repayment time indicator (WD). The WD quantifies the time the hydrological cycle takes to replenish the water resources used for annual crop production, distinguishing the different sustainability levels of soil-, surface-, and ground-water. This indicator highlights the locations and typology of threats imposed by agricultural production on water resources. On a global average, we found that wheat and rice production critically overuses ground water resources, especially in China and the US, and cotton production overuses both surface -and ground-water, particularly in the US. Locally, unsustainable annual crop production is found over the Sabarmati basin (due to wheat) in India, and in the Chao Phraya basin (due to rice and sugarcane) in Thailand, where the water debt repayment time exceeds 5 years in many cultivated areas. Including in the same framework analyses on water use efficiencies (through the CWF) and measure of water use (un)sustainability (through the WD) enables screening analyses at finding specific solutions in cases of low water use efficiencies and/or in critical situation of overuses. While local drivers monitor the water use for production, global drivers attempt to explore the globalization of water resources that happens through the international trade of agricultural goods. Why do countries become trade patterns, hence establishing a more or less stable relation, which implies externalization of water resources use? The third part of this thesis answers to this question through the elaboration of a threshold-based link prediction algorithm, aiming at finding the drivers behind link activation. Accordingly, a link is expected to exist depending on the predicted virtual water volume traded from the source node to the target node: the link is modelled as active when the volume is higher than 1000 m3y-1, non-active otherwise. This algorithm is able to capture 84% of the currently active links and 93% of non-active links. Country population, geographical distance between countries and fertilizers use are the major drivers to explain link existence. The link prediction model may be applied to build future scenarios of virtual water trade, in order to understand how local consumption and production patterns could affect the trade network.
Finally, in order to understand how close water demand to water availability is, we introduce a water debt (WD) indicator. The WD quantifies the payback time the hydrological cycle takes to replenish the water resources used for annual crop production. Hence, it highlights the locations and typology of threats imposed by agricultural production on water resources. E.g., the annual production of the nine study crops arise a WD of 10 years with the ground water resources of the US High Plain aquifer, mostly as a consequence of maize and soybean production. This indicator intends to connect and integrate water resource management with other environmental issues, such as the carbon footprint. In short, the thesis contributes advancing our knowledge in the spatio-temporal explicit water footprint assessments, virtual water trade network, sustainable water use. The models developed in this thesis and the results shown in the following chapters allow (i) to explore pathways toward improved water use efficiencies and more sustainable water withdrawals, (ii) to model backward and forward trade network dynamics, and (iii) to project future water use scenarios.
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Meyer, Steven J. "GPS Receiver Testing on the Supersonic Naval Ordnance Research Track (SNORT)." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609808.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThere is an interest in using Global Positioning System (GPS) receivers to find: Time Space Position Information (TSPI), miss distances between a missile and target, and using the data real time as an independent tracking aid for range safety. Ashtech, Inc. has several standalone GPS receivers they believe can work at high g levels. This paper investigates how the Ashtech GPS receivers work under high g loading in one axis. The telemetry system used to collect data from the receivers and the reconstruction of the data will also be discussed. The test was done at SNORT (Supersonic Naval Ordnance Research Track) located at NAWS, China Lake, CA. The g level obtained was about +23 g’s with a deceleration of -15 g’s. The velocity reached was about Mach 2.0. A summary of the errors is included.
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Sakai, Kotaro. "Seismic Performance Analysis of Fill Dams Using Velocity Based Space-Time Finite Element Method." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263700.
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Mastalir, Anthony J. "The US response to China's ASAT : an international security space alliance for the future /." Maxwell AFB, Ala. : School of Advanced Air and Space Studies, 2008. https://www.afresearch.org/skins/rims/display.aspx?moduleid=be0e99f3-fc56-4ccb-8dfe-670c0822a153&mode=user&action=downloadpaper&objectid=4b87f6c0-936b-40bf-98d5-f8139a39e139&rs=PublishedSearch.
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Lochau, Malte [Verfasser]. "Model-based Quality Assurance of Cyber-Physical Systems with Variability in Space, over Time and at Runtime / Malte Lochau." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1147968470/34.
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Frühwirth-Schnatter, Sylvia. "Applied State Space Modelling of Non-Gaussian Time Series using Integration-based Kalman-filtering." Department of Statistics and Mathematics, WU Vienna University of Economics and Business, 1993. http://epub.wu.ac.at/1558/1/document.pdf.
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The main topic of the paper is on-line filtering for non-Gaussian dynamic (state space) models by approximate computation of the first two posterior moments using efficient numerical integration. Based on approximating the prior of the state vector by a normal density, we prove that the posterior moments of the state vector are related to the posterior moments of the linear predictor in a simple way. For the linear predictor Gauss-Hermite integration is carried out with automatic reparametrization based on an approximate posterior mode filter. We illustrate how further topics in applied state space modelling such as estimating hyperparameters, computing model likelihoods and predictive residuals, are managed by integration-based Kalman-filtering. The methodology derived in the paper is applied to on-line monitoring of ecological time series and filtering for small count data. (author's abstract)Series: Forschungsberichte / Institut für Statistik
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Uhl, Philip J. "A Spatio-Temporal Data Model for Zoning." BYU ScholarsArchive, 2002. https://scholarsarchive.byu.edu/etd/1.
Full textAbstract:
Planning departments are besieged with temporal/historical information. While for many institutions historical information can be relegated to archives, planning departments have a constant need to access and query their historical information, particularly their historical spatial information such as zoning. This can be a cumbersome process fraught with inaccuracies due to the changing organizational methods and the extended historical legacies of most municipalities. Geographic Information Systems can be a tool to provide a solution to the difficulties in querying spatio-temporal planning data. Using a data model designed specifically to facilitate the querying of historical zoning information, queries can be performed to answer basic zoning questions such as "what is the zoning history for a specific parcel of land?" This work outlines this zoning data model, its implementation, and its testing using queries basic to the needs of planning departments.