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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Contribuição ao dimensionamento e à avaliação operacional de terminais urbanos de passageiros metroviários e ferroviários. / Contribution of operational design and evaluation of urban passenger rail and subway terminals.

Guazzelli, Cauê Sauter 02 May 2011 (has links)
Esta pesquisa objetivou contribuir para o dimensionamento e a análise operacional de terminais metroviários e ferroviários brasileiros. Para tanto, iniciou-se com um levantamento bibliográfico sobre o tema, a partir do qual se procedeu à conceituação sistêmica do terminal, do seu dimensionamento operacional e do comportamento de pedestres no mesmo. Com base nesses conceitos, foi desenvolvido um modelo de simulação capaz de fornecer suporte aos processos de dimensionamento e avaliação operacional de terminais urbanos de passageiros ferroviários e metroviários. A pesquisa bibliográfica e uma pesquisa em campo suportaram a concepção do modelo, voltado para a realidade brasileira. A modelagem desenvolvida representa os passageiros ao passarem pelos processos envolvidos no embarque e desembarque do terminal. Devido à dificuldade de obtenção de dados operacionais, foi feita uma calibração do modelo por meio da comparação entre dados medidos em terminais durante sua operação e os resultados do modelo. Foram simulados cenários por meio do modelo e seus resultados analisados, o que permitiu sua comparação e a identificação de soluções que se adequam melhor aos requisitos do terminal. Os testes mostraram que o modelo é adequado para dar suporte à tomada de decisão ao planejador durante o planejamento e avaliação operacional desse tipo de terminal e representa um passo significativo para o desenvolvimento de um modelo mais completo, capaz de permitir sua aplicação a terminais mais complexos, incluindo o tratamento de componentes não operacionais. / This research aimed to contribute to the operational design and evaluation of urban passenger rail and subway terminals in Brazil. To this end, it began with a literature research on the subject that induced to systemic conceptualization of the terminal, its design and the operational pedestrian behavior in it. Based on these concepts, a simulation model was developed to support the processes of operational design and evaluation of urban passenger rail and subway terminals. The literature and field research supported the construction of the model, focused on the Brazilian reality. The model developed represents passengers traversing the processes involved in loading and unloading throughout the terminal. Due to the difficulty of obtaining operational data, a calibration of the model was performed by comparing data measured at terminals during operation and the model outputs. Scenarios were simulated by the model and its results analyzed, which allowed their comparison and identification of solutions that fit best the problem requirements. The tests showed that the model is suitable to support decision-making to the planner during the planning and operational evaluation of this type of terminal and represents a significant step towards developing a more complete model, able to allow its application to more complex terminals, including the treatment of non-operating components.
22

Plataforma de análise e simulação hidrológica - PLASH. / Plataform for hydrologic analysis and simulation - PLASH.

Cristiano de Pádua Milagres Oliveira 17 October 2012 (has links)
A modelagem matemática da hidrologia de bacias hidrográficas é largamente utilizada em estudos de diversos tipos de problemas encontrados na engenharia hidráulica e de recursos hídricos. Nestes últimos 150 anos, muitos pesquisadores realizaram observações e experimentos sobre a natureza do ciclo hidrológico para que pudessem entender e equacionar seu comportamento. Diversos modelos diferentes surgiram baseando-se em equacionamentos físicos e empíricos, sendo que muitos destes modelos clássicos são utilizados até hoje. Para se ter uma visão mais abrangente do tema, uma revisão do estado da arte é apresentada, com uma perspectiva histórica destes modelos e seus criadores, assim como uma classificação fundamentada em suas características. Também são examinados alguns dos sistemas computacionais para modelagem hidrológica de bacias hidrográficas mais utilizados atualmente. São discutidas as hipóteses de uma simplificação do ciclo hidrológico para eventos intensos utilizados em projetos. Cada componente do ciclo hidrológico simplificado é modelado utilizando um dos diferentes modelos hidrológicos propostos, com graus de complexidade distintos. Para cada um destes modelos é realizada uma análise de sensibilidades dos seus parâmetros. Baseado nos avanços tecnológicos mais recentes na ciência da computação foi desenvolvido, em paralelo a esta pesquisa, uma ferramenta computacional que compila todos os conceitos aqui apresentados e tem distribuição acadêmica livre. / The mathematical modeling of the watershed hydrology is widely used in studies of several problems related to hydraulic and water resources engineering. On these last 150 years, many researchers accomplished observations and experiments on the nature of the hydrologic cycle in order to understand and equates its behavior. Several different models appeared basing on physical and empiric equating, and many of these classic models are being used until today. To get a more comprehensive view on the theme, a state of the art revision is presented, with an historical perspective about these models and its creators, such as a classification based on its characteristics are presented. Also some computational systems of hydrologic modeling of watershed are also examined more used now. The hypotheses of a simplification of the hydrologic cycle are discussed for intense events used in projects. Each component of the simplified hydrologic cycle is modeled using one of the different hydrologic models proposed, with distinct grades of complexity. For each one of these models a sensibility analysis of their parameter is performed. Based on the more recent technological progresses in the computational science was developed, parallel to this research, a computational tool that compiles all the concepts here presented and has free academic distribution.
23

Hybrid Kinetic Monte Carlo Models of Cellular Processes in Interactive Dynamic Microenvironments

Timothy James Sego (7041083) 16 October 2019 (has links)
Living tissue consists primarily of cells and extracellular matrix. Cells perform functions, communicate, respire and remodel extracellular matrix. Likewise, diffusive chemical conditions and extracellular matrix exhibit their own effects on cellular and intracellular processes, depending on the consistency of the matrix and phenotype of the cell. These interactions produce the emergent phenomena of tissue function, repair and morphology. Computational modeling seeks to quantify these processes for the purposes of fundamental study and predictive capability in various applications, including wound healing, tumor vascularization and biofabrication of living tissue. Hybrid kinetic Monte Carlo models are well known to be capable of predicting observed behaviors like cell sorting and spheroid fusion due to differential adhesion and energy minimization. However, no hybrid model sufficiently provides a formal treatment of full cell, chemical and matrix interactivity in a dynamic environment, including heterogeneous matrix conditions, advecting materials, and intracellular processes. In this work, hybrid kinetic Monte Carlo models are developed to describe full interactivity of cells, soluble signals and insoluble signals in a complex, dynamic microenvironment at the cellular level. Modeling of intracellular chemical dynamics and effects on the cellular state is developed as stochastic processes, and cell perform metabolic and matrix remodeling activities. Computational models of select \textit{in vivo} and \textit{in vitro} phenomena are developed and simulated, showing the ability to simulate new phenomena concerning cell viability, growth dynamics, highly heterogeneous cellular distributions, and complex tissue structures resulting from phenomena like intercellular signaling, matrix remodeling, and cell polarity.
24

Optimisation of Urban Water Supply Headworks Systems Using Probabilistic Search Methods and Parallel Computing

Cui, Lijie January 2003 (has links)
Realistic optimisation of the operation and planning of urban water supply headworks systems requires that the issues of complexity and stochastic forcing be addressed. The only reliable way of accomplishing this is to use simulation models in conjunction with the Monte Carlo method which generates multiple hydro-climate replicates. However, such models do not easily interface with traditional optimisation methods. Probabilistic search methods such as the genetic algorithm (GA) and the shuffled complex evolution method (SCE) can be coupled to a generalised simulation model and thus accommodate complexity as well as stochastic inputs. However, optimisation of complex urban water supply systems is computationally intractable if Monte Carlo methods have to be used. This study first compared the GA and the SCE method using a simple case study. Both methods were found to cope well with the piecewise flat objective function surface typical of the headworks optimisation problem. This is because they have the inherent capability of vigorously exploring beyond the domain of a flat region. The SCE method is recommended especially when fast location of a good solution is desired. Nonetheless, the GA was preferred due to its inherent parallelism. Two methods were then explored to improve computational efficiency and turnaround time: parallel computing and replicate compression. The Sydney headworks system was used as a case study to investigate the key aspects of a full-scale headworks optimisation. It was concluded that the speedup was nearly proportional to the number of processors employed. Replicate compression can very significantly reduce the computational turnaround time for Monte Carlo simulation; unfortunately, this conclusion must be tempered by the limitation that the objective function depends on penalties arising from restrictions only. Critical analysis of the GA results suggested the optimised results were sound. The case study demonstrated the feasibility of parallel GA to identify near-optimal solutions for a complex system subject to stochastic forcing. / PhD Doctorate
25

Verification of Rural Traffic Simulator, RuTSim 2

Akililu, Meaza Negash January 2012 (has links)
Traffic models based on micro-simulation are becoming increasingly important as traffic analysistools. Due to the detailed traffic description, different micro-simulation models are needed tosimulate different traffic environments. The Rural Traffic Simulator, RuTSim, is a unique microtrafficsimulation model for traffic on rural roads. RuTSim is developed at VTI with support fromthe Swedish Transport Administration. Currently, a new version of the RuTSim model has beenimplemented based on the earlier one but with some enhancements. Due to these enhancements,the new implementation of RuTSim should be verified before being used to analyze real worldproblems. In this master’s thesis, a verification of the new implementation of the RuTSim model, RuTSim 2,has been carried out. This paper includes a description of traffic micro-simulation models forrural roads in general and a description of RuTSim model in particular. Common verificationtechniques of the simulation models are also discussed in this study. Based on the theoretical assessments, a model-to-model comparison verification scheme isselected to verify the RuTSim 2 model. That is, the model verification is performed by comparingthe simulation outputs from RuTSim 2 to the old version of RuTSim (RuTSim 1), since RuTSim1 is well verified and calibrated. Statistical hypothesis tests are used to check whether the meanand standard deviation differences of the simulation outputs between the two simulators aresignificant or not. Based on the verification results, the new version of the RuTSim model has comparable modelingof vehicle-vehicle and vehicle-infrastructure interactions as the old version. Furthermore, thehypothesis test results show that the differences of the mean simulation results of the twosimulators are not significant. Therefore, the new implementation of RuTSim model, RuTSim 2,has been proven to be equivalent model as the old version.
26

Monitoring the effects of drought on wheat yields in Saskatchewan

Chipanshi, Aston Chipampe 01 January 1996 (has links)
In order to reduce the vulnerability of wheat production to drought, a calibrated and validated CERES Wheat crop simulation model was used to predict wheat yields on major soil textural groups using historical weather data at Swift Current, Saskatoon and Melfort. Yields were predicted using a run-out technique which involved the use of actual weather data to the prediction date and historical weather data from 1960 to 1990 for the remainder of the growing season. Yield predictions were made at five Julian dates during the crop calendar and these dates coincided with crop emergence, terminal spikelet initiation, end of the vegetative growth, heading and start of grain filling. Three sample years were used as case studies to test the applicability of the run-out method in making yield predictions. Sample base years were those with the lowest, medium and highest yields between 1960 and 1990 and these were selected from ranked yield values using quartiles. Test years were termed base years and weather files that were joined with the test years were run-out years. Each base year had 30 run-out years (1960-1990) and the mean of each run-out year was compared with the observed yield at the end of the season. Run-out yields for each base year were summarised as simple probability distributions so that yields exceeding certain values could be selected. Run-out yields at five prediction dates were found to be in close agreement with observed yields at the end of the growing season. To account for the variability in yields that can be found between places within the same climatic zone, simulated yields were re-classified by soil type and water stress level. These modifiers (soil type and water stress level) showed that chances of getting high yields diminish from Melfort to Swift Current at all prediction points due to the high variability of yield factors. Yield predictions that were made as above suggested that if historical weather records are combined with available weather data during the growing season, a good indication of yields can be obtained ahead of the harvest time and this could allow producers and those in the agri-business to decide on alternative actions of minimizing losses when prospects of getting a good yield are poor.
27

Finding a representative day for simulation analyses

Watson, Jebulan Ryan 23 November 2009 (has links)
Many models exist in the aerospace industry that attempt to replicate the National Airspace System (NAS). The complexity of the NAS makes it a system that can be modeled in a variety of ways. While some NAS models are very detailed and take many factors into account, runtime of these simulations can be on the magnitude of hours (to simulate a single day). Other models forgo details in order to decrease the runtime of their simulation. Most models are capable of simulating a 24 hour period in the NAS. An analysis of an entire year would mean running the simulation for every day in the year, which would result in a long run time. The following thesis work presents a tool that is capable of giving the user a day that can be used in a simulation and will produce results similar to simulating the entire year. Taking in parameters chosen by the user, the tool outputs a single day, multiple days, or a composite day (based on percentages of days). Statistical methods were then used to compare each day to the overall year. On top of finding a single representative day, the ability to find a composite day was added. After implementing a brute force search technique to find the composite day, the long runtime was deemed inconvenient for the user. To solve this problem, a heuristic search method was created that would search the solution space in a short time and still output a composite day that represented the year. With a short runtime, the user would be able to run the program multiple times. Once the heuristic method was implemented, it was found that it performed well enough to make it an option for the user to choose. The final version of this tool was used to find a representative day and the result was used in comparison with output data from a NAS simulation model. Because the tool found the representative day based on historical data, it could be used to validate the effectiveness of the simulation model. The following thesis will go into detail about how this tool, the Representative Day Finder, was created.
28

Modelling water discharge and nitrogen loads from drained agricultural land at field and watershed scale /

Salazar, Osvaldo, January 2009 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.
29

Land-use and land-cover dynamics and rural livelihood perspectives, in the semi-arid areas of Central Rift Valley of Ethiopia

Garedew, Efrem, January 2010 (has links) (PDF)
Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2010. / Härtill 4 uppsatser.
30

In-vivo and postmortem biomechanics of abdominal organs under compressive loads : experimental approach in a laparoscopic surgery setup /

Brown, Jeffrey Dale, January 2003 (has links)
Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 234-239).

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