Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

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.

O objetivo desta pesquisa foi recalibrar um modelo de simulação de rodovias de pista simples a fim de seja possível usá-lo no estudo de estradas do Estado de São Paulo. O modelo escolhido para recalibração é o TRARR (TRAffic on Rural Roads) versão 4.0, desenvolvido na Austrália pelo ARRB Transport Research Ltd. A recalibração do modelo consistiu em alterar parâmetros referentes ao desempenho (relação potência/massa) e características (massa, comprimento) dos veículos pesados e um parâmetro relativo ao comportamento dos veículos quando viajando em pelotões, de tal modo que os resultados da simulação ficassem compatíveis com os observados em campo. As medidas de desempenho escolhidas para a recalibração foram: a porcentagem de veículos trafegando em pelotões, a velocidade média dos veículos e a taxa de ultrapassagens. Os dados para a recalibração do modelo foram coletados num trecho de 2,8 km de extensão, na rodovia SP 255, entre as cidades paulistas de Araraquara e Ribeirão Preto. No processo de recalibração, as medidas de desempenho observadas no campo foram comparadas com as produzidas pelas versões recalibrada e original do simulador. Ao final da recalibração, pôde-se concluir que as duas versões do modelo são capazes de simular adequadamente o trecho estudado, sendo que o modelo recalibrado produz resultados ligeiramente melhores que os da versão original. O modelo recalibrado foi validado simulando-se um trecho de 10 km de extensão da SP 255 e comparando-se os valores medidos no trecho para as medidas de desempenho escolhidas com os valores produzidos pela versão recalibrada do simulador. Os resultados dessa comparação indicam que o modelo pode ser considerado capaz de simular adequadamente a operação de rodovias de pista simples no Estado de São Paulo. Os resultados do estudo também sugerem que a precisão pode ser melhorada com um ajuste fino de alguns dos parâmetros não modificados durante a recalibração. / The objective of this research is to recalibrate a two-lane highway simulation model to allow its employment within the context of the São Paulo state highways, Brazil. The model chosen for this recalibration is TRARR (TRAffic on Rural Roads) version 4.0, originally developed a in Australia by ARRB Transport Research Ltd. The procedure used for the model recalibration consisted in modifying input parameters related to heavy vehicle dimensions and performance characteristics (power/mass ratio, weight and length) as well as to the behavior of vehicles in platoons, in such a way that the model outputs are compatible with real traffic behavior. Three measures of performance were chosen for recalibration of the model: percent of jouney time spent following, average speed and overtaking rate. Data for model recalibration were collected at a 2.8 km rural section of SP 225, a highway which connects the cities of Ribeirão Preto and Araraquara in the state of São Paulo (Brazil). The recalibration procedure was based on comparisons of the measures of performance observed on the real highway with those produced by the simulator\'s recalibrated and original versions. At the end of the recalibration process, both the recalibrated and the original models were considered capable of reproducing the traffic behavior on a two-lane highway similar to the ones in the state of São Paulo. Furthermore, it was concluded that the recalibrated model is capable of producing results slightly better than the original one. The recalibrated model was submitted to a validation procedure in which a 10 km section of SP 255 was simulated and the measures of perfomance obtained with the model were compared to field observations. The results of the validation procedure indicate that recalibrated version of TRARR is capable of simulating traffic operations on rural two-lane highways in the state of São Paulo. The results of the research also suggest that the model results may be improved with fine-tuning of some of the parameters that were not modified during the recalibration procedure.

CluSys is a simulation platform that is developed by LuK GmbH & Co. KG to support product development engineers. It integrates different simulation calculation kernels and provides a collaborative environment for tool-independent chain simulation processes. The data between simulation modules in chain simulations is exchanged by defining intercommunications between individual parameters manually. This thesis provides a concept to automate the data exchange process between the parameters of different simulation models based on their physical meaning. Different approaches implemented in contemporary simulation environments are discussed, analyzed and a customized solution compatible with CluSys based on abstract interface approach is developed. This concept is implemented using an SQL database creating a parameter dictionary and an automatic intercommunication interface that uses the dictionary to recognize the parameters and define data exchange processes between them automatically. The implemented solution makes the data exchange between parameters of different simulation models independent of their labels, module names or units.

Comprendre les phénomènes consiste souvent a interroger les modèles mathématiques des systèmes considérés. En particulier. il s'agit d'obtenir par leur intermédiaire des réponses fiables aux questions de type « pourquoi'? ». Nous y réussissons dès lors que les modèles sont acceptables et intelligibles: c'est l'idée directrice de la thèse. Ce double réquisit est ainsi étudié; d'abord dans l'analyse des modèles analytiques puis dans celle des modèles de simulation. Cela a permis dans un premier temps de mettre en lumière le rôle positif des idéalisations dans la compréhension par les modèles analytiques. Puis, dans un second temps, il a été possible d'identifier les conséquences du tournant computationnel. Il demeure en effet un fossé entre le modèle computationnel et ses résultats, il cause, notamment de l'opacité épistémologique des simulations numériques. Or ce fossé semble doublement entraver notre compréhension des phénomènes simulés. En effet, d'une part, certaines difficultés d'ordre épistémologique, qui sont propre à la justification et a l'utilisation des modèles de simulation, contreviennent il leur acceptabilité. D'autre part, puisque la simulation ne peut pas faire l'objet d'une inspection directe, il est difficile pour l'utilisateur de faire la relation entre les résultats de cette simulation et le contenu du modèle : celui-ci devenant par là-même inintelligible. Néanmoins. les représentations visuelles semblent jouer un rôle fondamental en permettant de surmonter le problème de l'opacité des simulations et ainsi d'assurer une fonction explicative. / Understanding phenomena often requires using mathematical models of the target systems. ln particular, this requires obtaining. through them. reliable answers to why-questions. In this context, we achieve understanding once the models are acceptable and intelligible; this is the central assumption in this thesis. This double requirement is thus studied first in the analysis of analytical models. and then in the analysis of simulation models. This study first allowed us to highlight the positive role of idealizations in understanding through analytical models. Next, it allowed for an identification of the consequences of the computational turn. There is in fact a gap between a computational model and its results. partly because of the epistemic opacity of computer simulations. This gap seems to doubly hinder our understanding of simulated phenomena. On the one hand, some epistemological difficulties arise which are specific to the justification and the use of simulation models. These difficulties contravene their acceptability. On the other hand, since simulation is not open to direct inspection. it seems difficult for a user to make the relation between the model content and its results. Nevertheless, visual representations seem to play a fundamental function in allowing us to overcome the opacity issue. and thus to provide us with explanatory elements to our why-questions.

In the past decade South Africa experienced major political and economic changes. In addition to these major changes, South Africa is a highly diverse country and a country of extremes in many respects. Within this dynamic and diverse environment the agricultural sector has to survive and grow financially. In order to survive and grow, good decision-making within the agricultural sector in terms of policies and business strategies is extremely important and necessary. However, within the dynamic and extreme environment it is very difficult for decision-makers to make correct decisions since the likely impact of changes in markets and policies is difficult to quantify. The general objective of this dissertation is to identify and construct a type of farm-level model that will have the ability to quantify the likely impact of change in markets and policies on the financial viability of a representative farm. The specific objective is to construct a model of a representative grain and livestock farm in the Reitz district, Free State province, South Africa. The approach to farm-level modelling that is followed is a positivistic approach since questions of “what is the likely impact” is asked, and not “what ought to be” questions. Apart from behavioural equations, this farm-level simulation model also consists of accounting identities. The model is of a deterministic type since explanatory and descriptive types of questions need to be answered. The development of this farm-level model contributes to research in the field of farm-level modelling in South Africa due to the fact that it has the ability to simulate the impact of changes in markets and policies on a representative farm’s financial position. This is done by linking the farm-level model to a sector-level model developed by Meyer (2002) as well as outputs from several other institutions in terms of macro-economic variables and social variables. There are, however, several issues that became clear in this study. Firstly, positivistic simulation models have the disadvantage that validation and verification are difficult and time consuming due to lack of accurate and detailed data. Secondly, due to the positivistic nature of the model, the assumption is made that very little adjustment in terms of the farm structure takes place during the simulation process. One possible solution to this problem of not being able to simulate adaptation to changing conditions is to develop a model following a normative approach. The third problem with specifically the deterministic type of model is the fact that the model and simulation process assumes no risk. Lastly, in following the positivistic approach, the modeller needs theoretical as well as practical knowledge and understanding of the system modelled and simulated, in order to simulate reality as closely as possible. / Dissertation (MSc Agric)--University of Pretoria, 2006. / Agricultural Economics, Extension and Rural Development / unrestricted

Empirical techniques are developed to adjust dynamic model forecasts on the seasonal time scale for southern African summer rainfall. The techniques, called perfect prognosis and model output statistics (MOS), are utilized to statistically "recalibrate" general circulation model (GCM) large-scale fields to three equi-probable rainfall categories for December to February. The recalibration is applied to a GCM experiment where simultaneously observed sea-surface temperature (SST) fields serve as the lower boundary forcing, referred to as the simulation mode experiment. Cross-validation sensitivity tests are first performed over a 28-year climate period to design an optimal canonical correlation analysis (CCA) model for each of the two recalibration methods. After considering several potential predictor fields, the 700 hPa geopotential height field is selected as the single predictor field in the two sets of statistical equations that are subsequently used to produce recalibrated rainfall simulations over a 1 a-year independent test period. Patterns analysis of the predictor and predictand fields suggests that anomalously low (high) 700 hPa geopotential heights over the subcontinent are associated with wet (dry) conditions over land, an association that is supported by observational evidence of rain (drought) producing systems. Additionally, the dominant mode of the recalibration equations is associated with the EI Nino/Southern Oscillation (ENSO) phenomenon. Somewhat higher retro-active skill levels are found using the MOS technique, but the computationally less intensive perfect prognosis technique should also be able to produce usable seasonal rainfall forecasts over southern Africa in an operational forecast environment hampered by the lack of computing resources. / Dissertation (MSc)--University of Pretoria, 2006. / Geography, Geoinformatics and Meteorology / Unrestricted

This diploma thesis deals with an optimization of Rankine-Clausius steam cycle. The theoretical information about the Optimization and the Rankine-Clausius cycle are described at the beginning of the thesis. These theoretical findings are later used to create simulation models in MATLAB. Individual simulation models are variants of the ideal R-C cycle. Simulation models include the basic cycle model, the supercritical cycle and the cycle with reheat. For these models the optimal configurations are found and their t-s diagrams are plotted.