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1
Ozhan, Gurkan. "Transforming Mission Space Models To Executable Simulation Models." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613826/index.pdf.
Texte intégralRésumé :
This thesis presents a two step automatic transformation of Field Artillery Mission Space Conceptual Models (ACMs) into High Level Architecture (HLA) Federation Architecture
Models (FAMs) into executable distributed simulation code. The approach followed in the course of this thesis adheres to the Model-Driven Engineering (MDE) philosophy. Both
ACMs and FAMs are formally defined conforming to their metamodels, ACMM and FAMM, respectively. ACMM is comprised of a behavioral component, based on Live
Sequence Charts (LSCs), and a data component based on UML class diagrams. Using ACMM, the Adjustment Followed by Fire For Effect (AdjFFE) mission, which serves as the source model for the model transformation case study, is constructed. The ACM to FAM transformation, which is defined over metamodel-level graph patterns, is carried out
with the Graph Rewriting and Transformation (GReAT) tool. Code generation from a FAM is accomplished by employing a model interpreter that produces Java/AspectJ code. The
resulting code can then be executed on an HLA Run-Time Infrastructure (RTI). Bringing a fully fledged transformation approach to conceptual modeling is a distinguishing feature of
this thesis. This thesis also aims to bring the chart notations to the attention of the mission space modeling community regarding the description of military tasks, particularly their
communication aspect. With the experience gained, a set of guidelines for a domainindependent transformer from any metamodel-based conceptual model to FAM is offered.
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Hauth, Michael. "Visual simulation of deformable models." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97232125X.
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Kreula, Juha. "Quantum simulation of fermionic models." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:1de91b0b-1cd7-4a95-ac56-312529b51357.
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This work is a theoretical study of fermionic models. We focus on problems where highly controllable quantum simulators of these models have an important role, and we utilise both the analogue and the digital paradigm of quantum simulation. In the part on analogue quantum simulation, we focus on the proposed 'spin-asymmetric' Josephson effect where Cooper-paired spins display frequency synchronized Josephson oscillations with spin-dependent amplitudes. We consider different scenarios where the phenomenon could manifest in ultracold atomic Fermi gases. We study a Fermi gas Josephson junction in the recently realized Josephson plasma oscillation regime with an additional spin-dependent potential and show that the asymmetry in the resulting spin-dependent plasma oscillation amplitudes is on the order of a couple of per cent. We also demonstrate numerically that spin-asymmetric Josephson-like currents occur in a one-dimensional spin-dependent optical superlattice, with amplitude asymmetries up to 39%. Finally, we show that at zero temperature the tunable critical current in ferromagnetic Josephson junctions can be explained by the spin-asymmetric Josephson effect. In the part where digital quantum simulation is used, we propose a hybrid quantum-classical approach to studying strongly correlated fermion models. In this approach, a digital quantum simulator works in conjunction with a classical feedback loop to solve the infinite-dimensional Hubbard model directly in the thermodynamic limit. The scheme implements the well-established dynamical mean-field theory (DMFT) method, such that the digital quantum simulator solves the classically hard DMFT impurity problem and self-consistency is taken care of in a classical computer. We first present a few-qubit proof-of-principle setup for equilibrium systems that implements the simplified 'two-site' DMFT. This few-qubit setup is used for a qualitative description of the Mott transition in the half-filled infinite-dimensional Hubbard model. We then describe a scalable setup for simulating non-equilibrium many-body quantum dynamics by proposing the implementation of the non-equilibrium extension of DMFT with the hybrid device.
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Pohl, Thomas. "Design of adaptable simulation models." Thesis, Sheffield Hallam University, 2006. http://shura.shu.ac.uk/20240/.
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In today's world, with ever increasing competition, modelling and simulation proves to be a very helpful tool. Many methodologies exist to help build a simulation model from scratch. In terms of adaptability, most current attempts focus on either the operational side, ie the automated integration of data into a model, or the creation of new software. However, very few attempts are being made to improve the adaptability of shelved models built in existing simulation software. As a result, there is a certain reluctance, in some areas, to use simulation to its full potential. Based on these facts, it is obvious that anything, which makes reuse of simulation models easier, can help improve the use and spread of simulation as a valuable tool to maintain a company's competitiveness. In order to find such a solution, the following issues are looked at in this thesis: The changes to a simulation model that constitute the biggest problem, ways to minimise those changes, and possibilities to simplify the implementation of those changes. Those factors are evaluated, first by investigating current practices of building adaptable simulation models via a literature review, then the most difficult changes to implement in a simulation model, and the most frequent types of simulation software, are identified by means of interviews and questionnaire surveys. Next, parameters describing the adaptability of a simulation model are defined. In a further step, two of the most widely used simulation packages are benchmarked against a variety of tasks, reflecting the changes most frequent to models. The benchmarking study also serves to define and test certain elements regarding their suitability for adaptable models. Based on all those steps, model building guidelines for the creation of adaptable simulation models are developed and then validated by means of interviews and a framed field experiment. The interviews and questionnaire reveal that deleting is the easiest task and modifying the most complicated, while handling devices are the most difficult element to modify. The results also show that simulators (eg Arena) are the most widespread type of simulation software. The benchmarking showed that Arena is overall more adaptable than Simul8, and confirms the findings from the user survey. Also, it shows that sequencing is very helpful for modifying models, while the use of sub-models decrease the adaptability. Finally, the validation proves that the model building guidelines substantially increase the adaptability of models.
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Bezuidenhoudt, Cecile Margaret. "Optimisation of complex simulation models." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/6572.
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Computer simulation models are widely and frequently used to model real systems to predict output responses under specified input conditions. Choosing optimal simulation parameters leads to improved operation of the model but it is still a challenge as to how to go about optimally selecting these parameter values. The aim of this thesis was to see if a method could be found to optimise a simulation model provided by a client. This thesis provides a review of the literature of various simulation optimisation techniques that exist. Five of these simulation optimisation techniques - Simulated Annealing, Genetic Algorithms, Nested Partitions, Ordinal Optimisation and the Nelson-Matejcik Method - were selected and applied to a test case stochastic simulation model to gain an understanding into the techniques for their use in optimising the test model. These techniques were then used and applied to optimise a real life simulation model provided by a client. A technique combining the Ordinal Optimisation and Simulated Annealing optimisation methods provided the best results. This technique was provided to the client as a strategy to implement into their simulation model.
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O'Keefe, R. M. "Developing simulation models : an interpreter for visual active simulation." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236359.
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Bertelrud, P. Anders I. "An object-oriented simulator for the visual simulation environment." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-08142009-040521/.
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Buchta, Christian, and Sara Dolnicar. "Learning by simulation. Computer simulations for strategic marketing decision support in tourism." SFB Adaptive Information Systems and Modelling in Economics and Management Science, WU Vienna University of Economics and Business, 2003. http://epub.wu.ac.at/1718/1/document.pdf.
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This paper describes the use of corporate decision and strategy simulations as a decision-support instrument under varying market conditions in the tourism industry. It goes on to illustrate this use of simulations with an experiment which investigates how successful different market segmentation approaches are in destination management. The experiment assumes a competitive environment and various cycle-length conditions with regard to budget and strategic planning. Computer simulations prove to be a useful management tool, allowing customized experiments which provide insight into the functioning of the market and therefore represent an interesting tool for managerial decision support. The main drawback is the initial setup of a customized computer simulation, which is time-consuming and involves defining parameters with great care in order to represent the actual market environment and to avoid excessive complexity in testing cause-effect-relationships. (author's abstract)<br>Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
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Kajero, Olumayowa T. "Meta-model assisted calibration of computational fluid dynamics simulation models." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/813857/.
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Computational fluid dynamics (CFD) is a computer-based analysis of the dynamics of fluid flow, and it is widely used in chemical and process engineering applications. However, computation usually becomes a herculean task when calibration of the CFD models with experimental data or sensitivity analysis of the output relative to the inputs is required. This is due to the simulation process being highly computationally intensive, often requiring a large number of simulation runs, with a single simulation run taking hours or days to be completed. Hence, in this research project, the kriging meta-modelling method was coupled with expected improvement (EI) global optimisation approach to address the CFD model calibration challenge. In addition, a kriging meta-model based sensitivity analysis technique was implemented to study the model parameter input-output relationship. A novel EI measure was developed for the sum of squared errors (SSE) which conforms to a generalised chi-square distribution, where existing normal distribution-based EI measures are not applicable. This novel EI measure suggested the values of CFD model parameters to simulate with, hence minimising SSE and improving the match between simulation and experiments. To test the proposed methodology, a non-CFD numerical simulation case of the semi-batch reactor was considered as a case study which confirmed a saving in computational time, and an improvement of the simulation model with the actual plant data. The usefulness of the developed method has been subsequently demonstrated through a CFD case study of a single-phase flow in both a straight type and convergent-divergent type annular jet pump, where both a single turbulent model parameter, C_μ and two turbulent model parameters, C_μ and C_2ε where considered for calibration. Sensitivity analysis was subsequently based on C_μ as the input parameter. In calibration using both single and two model parameters, a significant improvement in the agreement with experimental data was obtained. The novel method gave a significant reduction in simulation computational time as compared to traditional CFD. A new correlation was proposed relating C_μ to the flow ratio, which could serve as a guide for future simulations. The meta-model based calibration aids exploration of different parameter combinations which would have been computationally challenging using CFD. In addition, computational time was significantly reduced with kriging-assisted sensitivity analysis studies which explored effect of different C_μ values on the output, the pressure coefficient. The numerical simulation case of the semi-batch reactor was also used as a basis of comparison between the previous EI measure and the newly proposed EI measure, which overall revealed that the latter gave a significant improvement at fewer number of simulation runs as compared to the former. The research studies carried out has hence been able to propose and successfully demonstrate the use of a novel methodology for faster calibration and sensitivity analysis studies of computational fluid dynamics simulations. This is essential in the design, analysis and optimisation of chemical and process engineering systems.
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Cumin, David. "Simulation in anaesthesia: standards and models." Thesis, University of Auckland, 2010. http://hdl.handle.net/2292/7163.
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Harm from medical errors costs tens of billions of dollars and causes tens of thousands of deaths each year in the United States alone. This is not so surprising considering the lack of opportunity for medical students and consultants alike to practice rare events, to be systematically exposed to common scenarios, or to be objectively assessed. Similarly, there are limited opportunities to test new medical devices or procedures without putting patients at harm. Simulation has provided the airline industry, in particular, with such opportunities and is a contributing factor to the safety of air travel. Simulation in medicine has the same potential but there are few, if any, concrete standards to adhere to. My objectives were to provide a structure for such standards to be set, to develop methods for evaluating the modelled physiology of simulators, and to further the mathematical modelling needed for autonomous, realistic, and extendable simulators. To these ends, I have analysed the key components of simulation and reviewed existing simulators and the modelling which underpins their responses to interventions. A framework for standards was developed with a focus on the physiological modelling of anaesthetic simulators. Methods for evaluating the repeatability and concordance of simulators were explored using simple interventions. I created an extendable database of accurate, complete physiological and interventional time series data from anaesthetic cases. Some of these cases were used to confirm the repeatability and concordance results, and then used to develop more advanced methods for evaluating fidelity. Finally, I used a novel modelling approach to create an integrated model of the human cardio respiratory system encompassing cellular through to systemic physiological processes which produced promising results. It is my hope that the work in this thesis may pave the way for more realistic simulators and a more standardised approach to simulation so that medical errors are reduced.
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Björk, Martin, and Erik Deng. "Discrete simulation models of surface growth." Thesis, KTH, Teoretisk fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146052.
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In this thesis the time evolution and scaling properties of different discrete models of surface growth using computer simulation is studied. The models are mainly using random deposition at a perpendicular angle to the substrates to model the adsorption process, and both one dimensional and two dimensional surfaces are considered. The Edwards-Wilkinson, Kardar-Parisi-Zhang and Mullins equations are also studied as analytical methods to describe the growth of surfaces. The scaling exponents derived from these equations are used as reference when analysing the exponents calculated from the simulation models studied in this thesis. We have found that the simulation models do not correspond perfectly with the analytical models for surface growth, suggesting possible flaws in our models or definitions. Despite the possible flaws, the models prove to be powerful tools for analysing the time evolution of surface growth. Furthermore, we have shown that most of the simulation models exhibit the expected scaling properties, which indicates that the surfaces do have the self-affine structure they are presumed to have.<br>I denna avhandling har tidsutvecklingen och skalningsegenskaperna hos olika diskreta modeller för yttillväxt studerats med hjälp av datorsimuleringar. De flesta modellerna använder slumpmässig deposition vinkelrätt mot substraten för att modellera adsorption, och både en och tvådimensionella modeller har studerats. Edward-Wilkingson-, Kardar-Parisi-Zhang och Mullinsekvationen har även studerats som analytiska modeller för att beskriva yttillväxt. Skalningsexponenterna som har erhållits från dessa ekvationer har använts som referenser vid analysen av exponenterna som har räknats ut från de simuleringsmodeller som har studerats i denna avhandling. Vi har kommit fram till att simuleringsmodellerna inte stämmer överrens perfekt med de analytiska modellerna, vilket tyder på möjliga brister i våra modeller eller definitioner. Trots de möjliga bristerna har modellerna visat sig vara kraftfulla verktyg vid analys av tidsutvecklingen av yttillväxt. Vidare har vi visat att de flesta av simuleringsmodellerna uppvisar de förväntade skalningsegenskaperna, vilket är ett tecken på att ytorna har den självaffina struktur de antas ha.
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PEREIRA, GUILHERME ARMANDO DE ALMEIDA. "COPULA MODELS FOR STREAMFLOW SCENARIO SIMULATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33720@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>PROGRAMA DE DOUTORADO SANDUÍCHE NO EXTERIOR<br>Muitos dos modelos de simulação de cenários de vazões, necessários para o planejamento e operação de setores elétricos, são construídos sob hipóteses rígidas. Isto pode restringir sua capacidade de representar dependências não-lineares e\ou distribuições não usuais. Cópulas superam estas limitações. Elas possibilitam que o comportamento marginal das variáveis seja modelado separadamente da estrutura de dependência do vetor aleatório. Além do mais, podem representar os mais diversos tipos de associações. Isto posto, esta tese apresenta 3 artigos onde modelos de cópulas são desenvolvidos visando a simulação de cenários de vazões. No primeiro artigo, propomos um modelo periódico de cópulas vine espaciais para simulação multivariada. As principais contribuições são a extensão para o caso periódico dos modelos de cópulas vine espaciais; a drástica redução do número de parâmetros; o desenvolvimento de um modelo não linear multivariado para simulação de cenários de vazões que incorpora a dependência temporal, a dependência espacial, a variação sazonal e o elevado número de usinas (alta dimensão). No segundo artigo, realizamos algumas modificações no modelo periódico espacial proposto que resultam em uma menor complexidade sem perda de performance. No terceiro artigo, propomos uma metodologia baseada em cópulas vine para modelar a dependência temporal de séries periódicas uni variadas de vazões. Dentre as contribuições destaca-se a construção de uma versão não-linear dos modelos periódicos autorregressivos (PAR(p)) onde a dependência temporal de qualquer ordem pode ser considerada; a possibilidade da incorporação de efeitos lineares e não-lineares; um modelo que não simula cenários com valores negativos; a flexibilidade para se modelar as distribuições marginais mensais.<br>Many streamflow scenario simulation models, which are needed for the planning and operation of energy systems, are built on rigid assumptions. This may limit their ability to represent nonlinear dependencies and/or nonstandard distribution functions. Copulas overcome these drawbacks and represent a flexible tool for modeling multivariate distributions. They enable the modeling of the marginal behavior of variables separately from the dependence structure of a random vector. Moreover, they can represent any type of association. This thesis is composed of three working papers, wherein copula-based models are proposed, objectifying the simulation of streamflow scenarios. In the first working paper, a periodic spatial copula
model is proposed to simulate multivariate streamflow scenarios. The main contributions include periodic extension of the spatial vine copulas; a distinct reduction in the number of parameters; and the development of a multivariate nonlinear model for streamflow scenario generation that incorporates time dependence, spatial dependence, and seasonal variation, and accounts for the dimensionality of the problem (high number of hydroelectric power plants). In the second working paper, some modifications are made to the periodic spatial model, resulting in lower complexity without the loss of performance. In the third working paper, a methodology based on the vine copula is proposed to model the temporal dependence structures in a univariate periodic streamflow time series. Among the contributions, the construction of a nonlinear version of the periodic autoregressive model (PAR(p)) is highlighted. The possibility of modeling linear and nonlinear effects and the flexibility of modeling the monthly marginal distributions are highlighted as well. This model does not simulate negative values.
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Ayres, Kelley. "Simulation models of bank risk management." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/18969.
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Master of Agribusiness<br>Department of Agricultural Economics<br>Bryan Schurle<br>Quantifying the impact of various economic events is essential for risk management in community banks. Interest rate shocks of either rapidly increasing or decreasing rates, in magnitudes of at least 200 basis points, is one of the more common risks modeled. Liquidity crises that impact deposits or loan demand can arise from either local or national economic events is another risk factor that regulators are requiring banks to quantify and plan for.
Excel spreadsheets can be used to develop models to measure and quantify these risks. Simulation tools and what-if analysis using data table and scenario manager identify possible outcomes for differing interest rate scenarios, interest rate shocks and liquidity stresses. Data table was used for simulation of a stochastic model to produce a cumulative distribution function of two hundred results each on three different interest rate environments. Scenario manager was used to narrow the simulation to a certain set of expectations affecting the balance sheet of the bank and another set of expectations from an interest rate shock. Changes in the bank’s balance sheet resulting from three different commodity price expectations were modeled. An interest rate shock of four hundred basis points over a two year period was also modeled.
These models are simple and cost effective. Once data are captured, the time required to develop and generate scenarios is manageable. The model can be used for a wide range of what-if alternatives as an individual bank may see fit. These models are adequate to meet present regulatory requirements for a community bank of smaller size that is not complex and does not possess a high risk profile.
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Xie, Xuping. "Large Eddy Simulation Reduced Order Models." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77626.
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This dissertation uses spatial filtering to develop a large eddy simulation reduced order model (LES-ROM) framework for fluid flows. Proper orthogonal decomposition is utilized to extract the dominant spatial structures of the system. Within the general LES-ROM framework, two approaches are proposed to address the celebrated ROM closure problem. No phenomenological arguments (e.g., of eddy viscosity type) are used to develop these new ROM closure models.
The first novel model is the approximate deconvolution ROM (AD-ROM), which uses methods from image processing and inverse problems to solve the ROM closure problem. The AD-ROM is investigated in the numerical simulation of a 3D flow past a circular cylinder at a Reynolds number $Re=1000$. The AD-ROM generates accurate results without any numerical dissipation mechanism. It also decreases the CPU time of the standard ROM by orders of magnitude.
The second new model is the calibrated-filtered ROM (CF-ROM), which is a data-driven ROM. The available full order model results are used offline in an optimization problem to calibrate the ROM subfilter-scale stress tensor. The resulting CF-ROM is tested numerically in the simulation of the 1D Burgers equation with a small diffusion parameter. The numerical results show that the CF-ROM is more efficient than and as accurate as state-of-the-art ROM closure models.<br>Ph. D.
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Spence, Michael A. "Statistical issues in ecological simulation models." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/10517/.
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Complex simulation models are being increasingly used in ecological modelling as a way of trying to understand a system by examining the processes that make up that system. Complex simulation models generally model behaviour of a system through a series of rules or algorithms, rather than describing it in a formal mathematical way and this can be a good way of capturing an ecologist's expertise and intuition. When interpreting outputs from such a model, it is important to allow for uncertainty due to parameter values which may not be known precisely and structural or implementation aspects. This thesis develops and applies a number of new statistical methods for handling uncertainty in such models. For stochastic simulation models with intractable likelihoods, parameter estimation can be done using Approximate Bayesian Computation with Markov Chain Monte Carlo (ABC-MCMC). This method does not mix well in the tails of the distribution. In this thesis we develop a version of ABC-MCMC that treats the random inputs as unknown as well as the unknown model parameters and we show empirically that this improves the efficiency of the ABC-MCMC algorithm on a queuing model and an individual-based model (IBM) of the group-living bird, the woodhoopoe. For models that are expensive to run, inference may be challenging even if the likelihood can be evaluated. We consider a deterministic multi-species size-based marine ecosystem model, with unknown initial states and parameters, and carry out Bayesian inference using a combination of MCMC and optimisation algorithms. Stochastic simulation models, especially IBMs, often have model uncertainty that is down to some seemingly arbitrary choices, for example spatial or temporal scales, the timing of different events or the spatial configuration. Ideally the outputs of the model should be insensitive to these choices. We develop methods for variance-based sensitivity analysis for stochastic models, allowing us to assess the sensitivity of the model outputs to stochasticity of the inputs and to partition out the variance between submodels. This enables us to test the arbitrary choices made by the modeller and thus test the robustness of the model. We demonstrate these methods on two IBMs: the woodhoopoe model and a bird breeding synchrony model.
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Coskun, Sarp Arda. "PATHCASE-SB MODEL SIMULATION AND MODEL COMPOSITION TOOLS FOR SYSTEMS BIOLOGY MODELS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1328556115.
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Köhn, Elvira. "Benefits of Simulation Models in Product Data Management System : A pilot study with cooling system simulation models." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-45199.
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The product development today handles increasingly complex products and to be able to compete on the current market companies need an effective PLM/PDM system to manage the lifecycle, models, and data connected to their products. Three of the factors for success in product development are time, cost, and quality. Which need to be supported by the processes and tool used in a project. Product development often uses both physical and analytical prototypes. The analytical method of simulation is an important element in product development that has started to shift from being a validation and verification tool at the last stages in the development process to be more included in the early stages. Simulation models often generate a big amount of data and because of this, the storing and management of them can be troublesome. Therefore, there is a need to have closer integration between design and simulation. The purpose of the thesis is to do an inquiry about what a PLM system contributes to in a company regarding their product development and why and how simulation models can be connected to the company’s PDM system.The methods used during the study were literature reviews, interviews, workshops, and a survey. The results show that in the literature the benefits of using a PLM and PDM system are connected to the factors for a successful product development which are time, quality and cost. While the employees think traceability, reuse of data and storing is the most important benefits. Simulation models are beneficial to the product development process and should, therefore, be stored in a way that there is a connection between the simulation model and the design model. For the employees, the highest-ranking benefits with adding simulation models to the system are traceability, reuse of simulation models and control over simulation models. A manual for how the simulation engineer can utilize the system and add simulation models to it are presented.
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Kucukyavuz, Fatih. "Transforming Conceptual Models Of The Mission Space Into Simulation Space Models." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613158/index.pdf.
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Helping to abstract a valid model from real system, conceptual modeling is an essential phase in simulation development lifecycle. With the development of the KAMA framework, a new methodology was presented to develop mission space conceptual model for simulation systems. It provides metamodel elements represented by graphical diagrams to develop conceptual models of mission space. BOM (Base Object Model), developed by SISO (Simulation Interoperability Standards Organization), is another conceptual modeling concept serving for simulation space.
KAMA models are very close to problem domain and intend to model real world concepts in requirement analysis and development phase. Whereas, being vital inputs for the simulation design phase, BOM models are closer to solution domain. Hence there is no defined way of using the captured mission space knowledge in simulation space, problem arises when moving from requirement analysis to design phase. In this study, to solve this problem, we propose a method for transforming mission space conceptual models in simulation space. Our solution approach will be mapping the KAMA mission space models to BOM simulation space models for automatically transport real world analysis results to simulation designers.
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Wikström, Jonas. "3D Model of Fuel Tank for System Simulation : A methodology for combining CAD models with simulation tools." Thesis, Linköpings universitet, Maskinkonstruktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-71370.
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Engineering aircraft systems is a complex task. Therefore models and computer simulations are needed to test functions and behaviors of non existing systems, reduce testing time and cost, reduce the risk involved and to detect problems early which reduce the amount of implementation errors. At the section Vehicle Simulation and Thermal Analysis at Saab Aeronautics in Linköping every basic aircraft system is designed and simulated, for example the fuel system. Currently 2-dimensional rectangular blocks are used in the simulation model to represent the fuel tanks. However, this is too simplistic to allow a more detailed analysis. The model needs to be extended with a more complex description of the tank geometry in order to get a more accurate model. This report explains the different steps in the developed methodology for combining 3-dimensional geometry models of any fuel tank created in CATIA with dynamic simulation of the fuel system in Dymola. The new 3-dimensional representation of the tank in Dymola should be able to calculate fuel surface location during simulation of a maneuvering aircraft. The first step of the methodology is to create a solid model of the fuel contents in the tank. Then the area of validity for the model has to be specified, in this step all possible orientations of the fuel acceleration vector within the area of validity is generated. All these orientations are used in the automated volume analysis in CATIA. For each orientation CATIA splits the fuel body in a specified number of volumes and records the volume, the location of the fuel surface and the location of the center of gravity. This recorded data is then approximated with the use of radial basis functions implemented in MATLAB. In MATLAB a surrogate model is created which are then implemented in Dymola. In this way any fuel surface location and center of gravity can be calculated in an efficient way based on the orientation of the fuel acceleration vector and the amount of fuel. The new 3-dimensional tank model is simulated in Dymola and the results are compared with measures from the model in CATIA and with the results from the simulation of the old 2-dimensional tank model. The results shows that the 3-dimensional tank gives a better approximation of reality and that there is a big improvement compared with the 2-dimensional tank model. The downside is that it takes approximately 24 hours to develop this model.<br>Att utveckla ett nytt flygplanssystem är en väldigt komplicerad arbetsuppgift. Därför används modeller och simuleringar för att testa icke befintliga system, minska utvecklingstiden och kostnaderna, begränsa riskerna samt upptäcka problem tidigt och på så sätt minska andelen implementerade fel. Vid sektionen Vehicle Simulation and Thermal Analysis på Saab Aeronautics i Linköping designas och simuleras varje grundflygplanssystem, ett av dessa system är bränslesystemet. För närvarande används 2-dimensionella rätblock i simuleringsmodellen för att representera bränsletankarna, vilket är en väldigt grov approximation. För att kunna utföra mer detaljerade analyser behöver modellerna utökas med en bättre geometrisk beskrivning av bränsletankarna. Denna rapport går igenom de olika stegen i den framtagna metodiken för att kombinera 3- dimensionella tankmodeller skapade i CATIA med dynamisk simulering av bränslesystemet i Dymola. Den nya 3-dimensionella representationen av en tank i Dymola bör kunna beräkna bränsleytans läge under en simulering av ett manövrerande flygplan. Första steget i metodiken är att skapa en solid modell av bränslet som finns i tanken. Därefter specificeras modellens giltighetsområde och alla tänkbara riktningar hos accelerationsvektorn som påverkar bränslet genereras, dessa används sedan i den automatiserade volymanalysen i CATIA. För varje riktning delar CATIA upp bränslemodellen i ett bestämt antal delar och registrerar volymen, bränsleytans läge samt tyngdpunktens position för varje del. Med hjälp av radiala basfunktioner som har implementerats i MATLAB approximeras dessa data och en surrogatmodell tas fram, denna implementeras sedan i Dymola. På så sätt kan bränsleytans och tyngdpunktens läge beräknas på ett effektivt sätt, baserat på riktningen hos bränslets accelerationsvektor samt mängden bränsle i tanken. Den nya 3-dimensionella tankmodellen simuleras i Dymola och resultaten jämförs med mätningar utförda i CATIA samt med resultaten från den gamla simuleringsmodellen. Resultaten visar att den 3-dimensionella tankmodellen ger en mycket bättre representation av verkligheten och att det är en stor förbättring jämfört med den 2-dimensionella representationen. Nackdelen är att det tar ungefär 24 timmar att få fram denna 3-dimensionella representation.
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Ahmad, Shamshad. "Numerical simulation of flames using flamelet models." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405993.
Texte intégralRésumé :
The thesis topic is located in the domain of numerical simulation of laminar flames. The principal aim of the presented research is the study of numerical techniques for the multidimensional simulation of flames with low computational costs. Present work is divided into three parts: First part is related to the development of a C++ simulation code for 1D laminar premixed flames. In the second part, a new technique to account for differential diffusion effects is proposed, which is based on tabulated chemistry methods. The third part focuses on the analysis of partially premixed flames.
A dedicated one-dimensional flame code is discussed for the simulation of complex/detailed chemistry and diffusion processes in premixed laminar flames. This code is written in C++ and is able to use different diffusion models (Fickian, Hirschfelder and Curtiss). The code yields accurate solutions of the major parameters as well as pollutant formation, both in the flame zone as well as downstream in the post-flame region. Results prove the accuracy of the code when compared to experimental data.
Following, a new technique is proposed to include differential diffusion effects into flamelet models. This approach is developed in the context of tabulated chemistry methods.The technique is based on correcting the progress-variable of flamelet models. The main feature of the proposed technique is the use of only one progress variable equation (1D manifold) without requiring a second parameter. This correction technique allows including detailed chemistry effects at low-cost in numerical simulation of multidimensional flames. A series of simulations are carried out for various flames. The results are excellently matched with full model solutions/detailed chemistry solutions.
The flamelet solutions databases, namely premixed and non-premixed, are further tested for partially premixed flames. This study is based on the investigation of partially premixed flame using single mode flamelet database solutions. For the verification of database solutions, finite rate chemistry simulations are also carried out to solve partially premixed flames. 3D jet coflow simulations are performed for three different level of premixing and results are compared with experimental data. The results show good agreement along with capabilities and limitations of flamelet databases solutions.<br>El tema de la tesi es troba en el domini de la simulació numèrica de les flames laminars. L'objectiu principal de la investigació presentada és l'estudi de tècniques numèriques per a la simulació multidimensional de flames amb baixos costos computacionals. El treball actual es divideix en tres parts: La primera part es relaciona amb el desenvolupament d'un codi 1D de simulació C ++ per flames laminars premesclades. A la segona part, es proposa una nova tècnica per explicar els efectes de difusió diferencial, que es basa en mètodes de química tabulada. La tercera part se centra en l'anàlisi de flames parcialment premesclades. Es discuteix un codi de flama unidimensional dedicat per a la simulació de processos complexos i detallats de química i difusió en flames laminars premesclades. Aquest codi està escrit en C ++ i és capaç d'utilitzar diferents models de difusió (Fickian, Hirschfelder i Curtiss). El codi proporciona solucions precises dels paràmetres principals, així com la formació de contaminants, tant a la zona de la flama com a la regió posterior a la flama. Els resultats demostren l'exactitud del codi en comparació amb les dades experimentals. A continuació, es proposa una nova tècnica per a incloure efectes de difusió diferencial en models de flamelet. Aquest enfocament es desenvolupa en el context dels mètodes tabulats de química. La tècnica es basa en la correcció de la variable de progrés dels models de flamelet. La característica principal de la tècnica proposada és l'ús d'una única equació de variable de progrés (espai 1D) sense necessitat d'un segon paràmetre. Aquesta tècnica de correcció permet incloure efectes químics detallats a baix cost en la simulació numèrica de flames multidimensionals. Una sèrie de simulacions es realitzen per diverses flames. Els resultats mostren una concordància excel·lentment amb solucions completes/detallades de la química. Les bases de dades de solucions de flamelet, a saber premesclades i no premesclades, es sotmeten a proves addicionals per flames parcialment premesclades. Aquest estudi es basa en la investigació de flames parcialment prebarrejades utilitzant solucions de base de dades monomode. Per a la verificació d'aquestes bases de dades, es realitzen simulacions de química de velocitat finita per resoldre flames parcialment premesclades. Es realitzen simulacions de flux d'aire en 3D per a tres nivells diferents de premescla i els resultats es comparen amb dades experimentals. Els resultats mostren un bon acord juntament amb les capacitats i limitacions de les solucions de bases de dades de flamelet.
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Axling, Erik. "Automatic Generation of Simulation Models from Designs." Thesis, Linköping University, Department of Computer and Information Science, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10409.
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<p>When working with embedded systems, secure and fast applications are desired. To achieve this the applications needs to be analyzed and optimized so that they will not be deadlocked or communicate inefficiently. For this purpose an analysis program that can track communications, deadlocks and response times is needed. Operating System Embedded, OSE, is a wide spread real-time operating system that is used in embedded systems. OSE-applications are excellent candidates for analysis and there exists such a tool, VirtualTime, for that purpose. To analyze an OSE-application a model needs to be written that VirtualTime can analyze. This takes up time and effort as the models can require a lot of work to write.</p><p>In this thesis we have investigated and implemented a prototype that translates OSE-application code into VirtualTime simulation model code. We used the transformation tool TXL to translate communication and timing behaviors. In the translation one needs to preserve the communication and timing behavior and throw away other unnecessary code in the OSE-application. This complicates the translation and sophisticated methods like backward slicing might be necessary. A proposed method in this thesis could help with the problem.</p>
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Oprea, Alexandra. "3D Fuel Tank Models for System Simulation." Thesis, KTH, Aerodynamik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102084.
Texte intégralRésumé :
The purpose of the present master thesis is to optimize the current fuel tank simulations procedure for the next generation of JAS 39 Gripen ghters developed by SAAB AB. The current simulation process involves three dierent steps performed in three dierent computer environments. While the procedure works reasonably well on the fuel tank models of the previous version of the aircraft, it is too slow for the new Gripen tank models and their high level of detail. An optimized version of the procedure is put forward, which allows for tank analysis and fuel system simulation within reasonable time frames. Suggestions are made for future improvements.
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Bhargava, Rajat. "Simulation models for variable speed electric drives." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22571.pdf.
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Yngve, Gary. "Visualization for biological models, simulation, and ontologies /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/6912.
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Huynh, Quoc T. "Dynamic system simulation using graphically defined models." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637363.
Texte intégralRésumé :
This thesis describes an approach to the digital simulation of dynamic systems in which the behaviour occurs continuously in time. Dynamic systems are modelled and synthesised in graphical forms, such as block diagrams and signal flow graph. The emphasis in this thesis has been on the block diagram form. A block diagram representation of a system model is graphically defined in the Control Engineering workStation (CES). Blocks in the block diagram can have realistic graphical symbols and meanings. Block operations can be defined in mathematical form, parameter-based form or text-based form. The graphically defined model in the form of a block diagram can be simulated using existing commercial simulation packages. For this purpose interfaces have been developed to allow CES to be integrated with two commercial simulation packages, ACSL and SIMNON, and can be extended to other packages if required. The user interaction with a simulation package has been carried out by graphical means, with the generation of simulation codes and the driving of the package being done automatically. Simulation results can be inspected in the graphical environment of CES. To exploit the topological and dynamic structures of system models represented in the form of block diagrams, for the purpose of parallel simulation, a graphical approach has been developed. This approach allows a concurrent simulation model to be expressed in a relatively simple manner, similar to that used with analog computers. Blocks and connections in the block diagram are considered to be separate communicating processes and communicative channels. Furthermore, these processes are considered as basic units to be allocated to processors. Based on this approach, a parallel transputer-based simulator has been developed. The transputer-based simulator has been linked to CES, using a mechanism similar to that used for linkage to commercial simulation packages.
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Shah, Sandeep R. "Perfect simulation of conditional and weighted models." Thesis, University of Warwick, 2004. http://wrap.warwick.ac.uk/59406/.
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This thesis is about probabilistic simulation techniques. Specifically we consider the exact or perfect sampling of spatial point process models via the dominated CFTP protocol. Fundamental among point process models is the Poisson process, which formalises the notion of complete spatial randomness; synonymous with the Poisson process is the Boolean model. The models treated here are the conditional Boolean model and the area-interaction process. The latter is obtained by weighting a Poisson process according to the area of its associated Boolean model. A fundamental tool employed in the perfect simulation of point processes are spatial birth-death processes. Perfect sampling algorithms for the conditional Boolean and area-interaction models are described. Birth-death processes are also employed in order to develop an exact omnithermal algorithm for the area-interaction process. This enables the simultaneous sampling of the process for a whole range of parameter values using a single realization. A variant of Rejection sampling, namely 2-Stage Rejection, and exact Gibbs samplers for the conditional Boolean and area-interaction processes are also developed here. A quantitative comparison of the methods employing 2-Stage Rejection, spatial birth-death processes and Gibbs samplers is carried, the performance measured by actual run times of the algorithms. Validation of the perfect simulation algorithms is carried out via x2 tests.
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Serras, Joan. "Multidimensional multilevel representation for traffic simulation models." Thesis, Open University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446273.
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Xu, Weiran 1968. "New turbulence models for indoor airflow simulation." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9933.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.<br>Includes bibliographical references (p. 157-165).<br>It is important to predict indoor environment in order to design thermally comfortable and healthy indoor spaces. Heating, Ventilating and Air Conditioning (HVAC) design engineers and architects widely use the Computational Fluid Dynamics (CFD) technique for indoor environment predictions. The CFD technique requires a turbulence model to correctly calculate indoor air distribution. However, the currently available turbulence models in the literature are either inaccurate or inefficient for the indoor environment predictions. To solve the problem, this thesis proposes two two-layer turbulence models and a zero-equation turbulence model. The two-layer models use a one-equation (k) model for the near wall region and the "standard" k -£ model in the outer region. The zero-equation model calculates turbulent viscosity based on local velocity and a length-scale. The near wall models have been developed with the aid of the data of natural and forced convection flows by Direct Numerical Simulation (DNS), while the zero-equation model has been proposed empirically. One of the two-layer turbulence models is used for predicting natural convection in rooms. The other two-layer model and the zero-equation model can be used to predict forced, natural, and mixed convection in rooms. These three new models have been applied to predict different types of indoor airflows. The corresponding DNS or experimental data were used to validate the models. This study concludes that the two-layer models can predict airflows most accurately, better than many k -E models. The computing cost is significantly lower than that of the low Reynolds number k-E models and is only slightly higher than that of the "standard" k-E models. The zero-equation model is at least ten times faster than the "standard" k-E model and it is numerically stable and can predict indoor airflow with acceptable accuracy.<br>by Weiran Xu.<br>Ph.D.
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Mahanti, Bhanu Prasad 1981. "Aggregate calibration of microscopic traffic simulation models." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28636.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.<br>Includes bibliographical references (p. 97-101).<br>The problem of calibration of microscopic simulation models with aggregate data has received significant attention in recent years. But day-to-day variability in inputs such as travel demand has not been considered. In this thesis, a general formulation has been proposed for the problem in the presence of multiple days of data. The formulation considers the day-to-day variability in all the inputs to the simulation model. It has then been formulated using Generalized least squares (GLS) approach. The solution methodology for this problem has been proposed and the feasibility of this methodology has been shown with the help of two case studies. One of them is with an experimental network and the other is with network from Southampton, UK. The results indicate that estimation of day-to-day OD flows is feasible. They also reinforce the importance of having good apriori information on the OD flows and locating the sensors so as to obtain maximum information.<br>by Bhanu Prasad Mahanti.<br>S.M.
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Coe, Paul. "Simulation models of shared-memory multiprocessor systems." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/13437.
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Multiprocessors have often been thought of as the solution to today's every increasing computing needs; but they are expensive, complex and difficult to design. This thesis focusses on the development of multiprocessor simulations that would aid the design and evaluation of such systems. The thesis starts by outlining the various possibilities for multiprocessor design and discusses some of the more common problems that must be addressed. A selection of simulation environments and models that have been developed to study complex computer systems are then described. The major problem with these simulation systems is that they generally focus on a small area of multiprocessor systems design in order to produce fast simulations that generate results quickly; consequently they provide very little flexibility and room for exploration. The aim of this project was to design and implement a flexible multiprocessor model within the HASE simulation environment, enabling the designer to explore a large design space with a minimum of effort, focussing more on flexibility and less on simulation speed. A parameterised simulation model has been developed that presents the designer with many design options with which to experiment. The parameters allow simple alternatives to be explored, for example, different component speeds or bus widths, as well as more complicated features, for example, coherence protocols, synchronisation primitives and architecture configurations. The model was designed in a modular manner that allows new parameter values to be incorporated, as well as new implementations of the various entities. To support this new model, the HASE system was extended to provide better support for multiprocessor modelling.
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Kuljis, Jasminka. "User interfaces and discrete event simulation models." Thesis, London School of Economics and Political Science (University of London), 1995. http://etheses.lse.ac.uk/1380/.
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A user interface is critical to the success of any computer-based system. Numerous studies have shown that interface design has a significant influence on factors such as learning time, performance speed, error rates, and user satisfaction. Computer-based simulation modelling is one of the domains that is particularly demanding in terms of user interfaces. It is also an area that often pioneers new technologies that are not necessarily previously researched in terms of human-computer interaction. The dissertation describes research into user interfaces for discrete event simulation. Issues that influence the 'usability' of such systems are examined. Several representative systems were investigated in order to generate some general assumptions with respect to those characteristics of user interfaces employed in simulation systems. A case study was carried out to gain practical experience and to identify possible problems that can be encountered in user interface development. There is a need for simulation systems that can support the developments of simulation models in many domains, which are not supported by contemporary simulation software. Many user interface deficiencies are discovered and reported. On the basis of findings in this research, proposals are made on how user interfaces for simulation systems can be enhanced to match better the needs specific to the domain of simulation modelling, and on how better to support users in simulation model developments. Such improvements in user interfaces that better support users in simulation model developments could achieve a reduction in the amount of time needed to learn simulation systems, support retention of learned concepts over time, reduce the number of errors during interaction, reduce the amount of time and effort needed for model development, and provide greater user satisfaction.
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Caruso, Elise M. "A Simulation Analysis of Bivariate Availability Models." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34153.
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Equipment behavior is often discussed in terms of age and use. For example, an automobile is frequently referred to 3 years old with 30,000 miles. Bivariate failure modeling provides a framework for studying system behavior as a function of two variables. This is meaningful when studying the reliability/availability of systems and equipment.
This thesis extends work done in the area of bivariate failure modeling. Four bivariate failure models are selected for analysis. The study includes exploration of bivariate random number generation. The random data is utilized in estimating the bivariate renewal function and bivariate availability function. The two measures provide insight on system behavior characterized by multiple variables.
A method for generating bivariate failure and repair data is developed for each model. Of the four models, two represent correlated random variables; the other two, stochastic functionally dependent variables. Also, methods of estimating the bivariate renewals function and bivariate availability function are constructed. The bivariate failure and repair data from the four failure models is incorporated into the estimation processes to study various failure scenarios.<br>Master of Science
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Alt, Aaron J. "Profile Driven Partitioning Of Parallel Simulation Models." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1407406955.
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Fazal, Md Abul. "MANAGING GROUNDWATER AQUIFERS WITH SIMULATION/OPTIMIZATION MODELS." Kyoto University, 1999. http://hdl.handle.net/2433/181889.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第7880号<br>農博第1038号<br>新制||農||777(附属図書館)<br>学位論文||H11||N3243(農学部図書室)<br>UT51-99-G474<br>京都大学大学院農学研究科地域環境科学専攻<br>(主査)教授 河地 利彦, 教授 青山 咸康, 教授 三野 徹<br>学位規則第4条第1項該当
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Brauen, H. Glenn (Howard Glenn) Carleton University Dissertation Computer Science. "Graphically defining simulation models of concurrent systems." Ottawa, 1988.
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Chadha, Vikrampal. "Simulation of large-scale system-level models." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12162009-020334/.
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Butler, John Christopher. "Simulation analysis of multi-criteria decision models /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Reggiani, Barbara <1976>. "Simulation models in biomechanics and experimental mechanics." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/542/1/reggiani_barbara_tesi.pdf.
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Reggiani, Barbara <1976>. "Simulation models in biomechanics and experimental mechanics." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/542/.
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Srivrunyoo, Inthira. "A contextualized Web-based learning environment for DEVS models." unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-11222007-132933/.
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Thesis (M.S.)--Georgia State University, 2007.<br>Title from file title page. Xiaolin Hu, committee chair; Rajshekhar Sunderraman, Ying Zhu, committee members. Electronic text (71 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Jan. 29, 2008. Includes bibliographical references (p. 70-71).
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Song, Ziqi, and 宋子麒. "A simulation based dynamic taxi model." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38574652.
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Chen, Quan, and 陈全. "Efficient high-frequency electromagnetic simulation in VLSI: rough surface effects and electromagnetic-semiconductor coupled simulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44904940.
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Huat, Bujang bin Kim. "Simulation of field trial structures." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294076.
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Madramootoo, Chandra Alastair 1954. "An agricultural land drainage simulation model /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72017.
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A deterministic computer model was developed to continuously simulate the runoff from surface and subsurface-drained fields in the St. Lawrence lowlands. The model simulates all of the major hydrologic and hydraulic processes occurring both above and below the ground. Input data requirements include hourly rainfall, daily potential evapotranspiration, soil physical properties, field dimensions, open channel geometry and drainage system specifications.<br>Events for the years 1978 to 1982 were simulated, to compare the runoff characteristics between 20 ha, clay loam, surface-drained and subsurface-drained fields. Further simulations were conducted to examine the hydrologic effects of wide-spaced, deep, parallel field ditches.<br>Hydrographs for the one-in-200-year storm were also simulated. All of the simulations confirmed that the peak flow rate on the subsurface-drained field was less than that of the surface-drained field. Longer times to peak and lag times occurred on the subsurface-drained field.
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Hopkins, Roisin. "System identification for crash victim simulation." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/7053.
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The work presented in this thesis concerns the identification of vehicle occupant models. Mathematical models of the vehicle occupant are used in the preliminary design and development phase of vehicle design. In the design phase, the model is used to guide the decision on restraint system feasibility. In the development phase the model is used to suggest solutions to problems associated with the dummy trajectory or restraint system performance. Current methods used -to determine such models involve independent component testing. The conditions under which the components are tested are often not typical of a crash test, hence iterations of the computer model are needed to successively improve model and test correlation. In order to address these problems which cause inaccurate specification of the mathematical models, an alternative method of data set assembly for crash victim models is suggested. This alternative method is based on the techniques of system identification which allow unknown system parameters to be determined from experimental input/output data. Initially the viability of using system identification techniques to develop a valid mathematical model of the vehicle occupant and restraint system was investigated. This initial study used input and output measurementsfr om computer simulations of the occupant in frontal impact, as source data for the identification. Effects of simulated disturbances (noise corrupted output signals) and the effects of simplified model structure on the identification are also investigated. Several methods for analysing the likely errors in the identified parameters are defined and discussed in this simulation study. Results relating to the identification of seat contact and seat belt characteristics from physical tests are also presented and these are interpreted in light of the simulation results.
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Easom, Gary. "Improved turbulence models for computational wind engineering." Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/10113/.
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The fundamental errors in the numerical modelling of the turbulent component of fluid flow are one of the main reasons why computational fluid dynamics techniques have not yet been fully accepted by the wind engineering community. This thesis is the result of extensive research that was undertaken to assess the various methods available for numerical simulation of turbulent fluid flow. The research was undertaken with a view to developing improved turbulence models for computational wind engineering. Investigations have concentrated on analysing the accuracy and numerical stability of a number of different turbulence models including both the widely available models and state of the art techniques. These investigations suggest that a turbulence model, suitable for wind engineering applications, should be able to model the anisotropy of turbulent flow as in the differential stress model whilst maintaining the ease of use and computational stability of the two equation k-e models. Therefore, non-linear expansions of the Boussinesq hypotheses, the quadratic and cubic non-linear k-e models, have been tested in an attempt to account for anisotropic turbulence and curvature related strain effects. Furthermore, large eddy simulations using the standard Smagorinsky sub-grid scale model have been completed, in order to account for the four dimensional nature of turbulent flow. This technique, which relies less heavily on the need to model turbulence by utilising advances in computer technology and processing power to directly resolve more of the flow field, is now becoming increasingly popular in the engineering community. The author has detailed and tested all of the above mentioned techniques and given recommendations for both the short and longer term future of turbulence modelling in computational wind engineering. Improved turbulence models that will more accurately predict bluff body flow fields and that are numerically stable for complex geometries are of paramount importance if the use of CFD techniques are to gain wide acceptance by the wind engineering community.
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Pinilla, Camilo Ernesto. "Numerical simulation of shear instability in shallow shear flows." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115697.
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The instabilities of shallow shear flows are analyzed to study exchanges processes across shear flows in inland and coastal waters, coastal and ocean currents, and winds across the thermal-and-moisture fronts. These shear flows observed in nature are driven by gravity and governed by the shallow water equations (SWE). A highly accurate, and robust, computational scheme has been developed to solve these SWE. Time integration of the SWE was carried out using the fourth-order Runge-Kutta scheme. A third-order upwind bias finite difference approximation known as QUICK (Quadratic Upstream Interpolation of Convective Kinematics) was employed for the spatial discretization. The numerical oscillations were controlled using flux limiters for Total Variation Diminishing (TVD). Direct numerical simulations (DNS) were conducted for the base flow with the TANH velocity profile, and the base flow in the form of a jet with the SECH velocity profile. The depth across the base flows was selected for the' balance of the driving forces. In the rotating flow simulation, the Coriolis force in the lateral direction was perfectly in balance with the pressure gradient across the shear flow during the simulation. The development of instabilities in the shear flows was considered for a range of convective Froude number, friction number, and Rossby number. The DNS of the SWE has produced linear results that are consistent with classical stability analyses based on the normal mode approach, and new results that had not been determined by the classical method. The formation of eddies, and the generation of shocklets subsequent to the linear instabilities were computed as part of the DNS. Without modelling the small scales, the simulation was able to produce the correct turbulent spreading rate in agreement with the experimental observations. The simulations have identified radiation damping, in addition to friction damping, as a primary factor of influence on the instability of the shear flows admissible to waves. A convective Froude number correlated the energy lost due to radiation damping. The friction number determined the energy lost due to friction. A significant fraction of available energy produced by the shear flow is lost due the radiation of waves at high convective Froude number. This radiation of gravity waves in shallow gravity-stratified shear flow, and its dependence on the convective Froude number, is shown to be analogous to the Mach-number effect in compressible flow. Furthermore, and most significantly, is the discovery from the simulation the crucial role of the radiation damping in the development of shear flows in the rotating earth. Rings and eddies were produced by the rotating-flow simulations in a range of Rossby numbers, as they were observed in the Gulf Stream of the Atlantic, Jet Stream in the atmosphere, and various fronts across currents in coastal waters.
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Michel, René. "Simulation and estimation in multivariate generalized Pareto models." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981745466.
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Östlund, Per. "Simulation of Modelica Models on the CUDA Architecture." Thesis, Linköping University, Department of Computer and Information Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52060.
Texte intégralRésumé :
<p>Simulations are very important for many reasons, and finding ways of accelerating simulations are therefore interesting. In this thesis the feasibility of automatically generating simulation code for a limited set of Modelica models that can be executed on NVIDIAs CUDA architecture is studied. The OpenModelica compiler, an open-source Modelica compiler, was for this purpose extended to generate CUDA code.</p><p>This thesis presents an overview of the CUDA architecture, and looks at the problems that need to be solved to generate efficient simulation code for this architecture. Methods of finding parallelism in models that can be used on the highly parallel CUDA architecture are shown, and methods of efficiently using the available memory spaces on the architecture are also presented.</p><p>This thesis shows that it is possible to generate CUDA simulation code for the set of Modelica models that were chosen. It also shows that for models with a large amount of parallelism it is possible to get significant speedups compared with simulation on a normal processor, and a speedup of 4.6 was reached for one of the models used in the thesis. Several suggestions on how the CUDA architecture can be used even more efficiently for Modelica simulations are also given.</p>
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Poon, Andrew. "Real time simulation of colonoscopy using dynamic models." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/8177.
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