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Wilhelmij, Gerrit Paul. "Symbolic simulation of dynamic systems." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305630.
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Gupta, Amit. "Model reduction and simulation of complex dynamic systems /." Online version of thesis, 1990. http://hdl.handle.net/1850/11265.
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Wiegand, Mark Eric. "Constructive qualitative simulation of continuous dynamic systems." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/868.
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Ramírez, Muñoz Patricio D. (Patricio Dario). "Dynamic simulation of nuclear hydrogen production systems." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62733.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2011."September 2010." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 261-265).
Nuclear hydrogen production processes have been proposed as a solution to rising CO 2 emissions and low fuel yields in the production of liquid transportation fuels. In these processes, the heat of a nuclear reactor is used to run the chemical reactions in a hydrogen plant. The resulting system is tightly interconnected and operates at very high temperature and pressure, which can lead to operational disruptions and accidents. For this reason, computational studies validating the safe operation of the system are required by regulatory authorities. In the past, safety studies have been conducted by using legacy codes, such as RELAP and MELCOR, and their focus has been the operation of nuclear power plants. However, traditional legacy codes are not appropriate to simulate nuclear hydrogen production. The simulation of a nuclear reactor itself is already complex because it involves simulating reactor kinetics and transport phenomena. To that complexity, nuclear hydrogen production adds the need to simulate chemical reactions in the hydrogen plant. These chemical reactions cannot be represented easily in legacy codes because these codes lack the flexibility, speed and accuracy required to simulate them. Therefore, only a limited number of studies on the safety of these systems exist. Instead of using legacy codes, this thesis proposes using equation-based simulators developed by the chemical engineering community to model and study the safety of a nuclear hydrogen production plant. Equation-based simulators were designed to be flexible, extensible and fast because they have to simulate a vast range of processes from the chemical industry. Thus, they provide a good platform for the simulation of nuclear hydrogen production systems. This thesis explains the models used for the different parts in the nuclear hydrogen production plant, and then presents the response of this plant model to different accident scenarios. The first contribution of this thesis is a novel equation-based model for the heat transfer loop connecting a nuclear reactor and a hydrogen production plant. This heat transfer loop uses helium as the heat transfer fluid, which makes simulating its behavior difficult because of the need to model gas dynamics. To resolve this, three models for gas dynamics and two set of coupling conditions for boundary variables were tested in JACOBIAN, an equation-based simulator. The three models for gas dynamics in combination with a novel approach to set coupling conditions for boundary variables were able to represent the interesting time scales accurately in transient scenarios. The accuracy and computational speed of these simulations outperformed those produced by a reference model created in RELAP, a legacy code. The second contribution is a model of a nuclear hydrogen production plant using high-temperature steam electrolysis to produce hydrogen. This model was created to study the effect of potential accidents on the nuclear reactor. It included detailed models of the nuclear reactor and heat transfer loop, and a partial model of the electrolysis plant. The nuclear reactor was modeled as a pebble bed modular reactor, which is one of the safest designs available. The reactor was connected to the hydrogen production plant using the heat transfer loop model already developed in this thesis. The hydrogen production plant was partially represented as a steam superheater in the heat transfer loop. The third contribution is the demonstration of the safety characteristics of the nuclear hydrogen production plant by subjecting the plant model to three accident scenarios. The scenarios involved disruptions in the hydrogen plant or in the heat transfer loop, and all of them-directly or indirectly-lead to a loss of heat sink capacity for the nuclear reactor. This resulted in an increase of the nuclear reactor core temperature, which was quickly moderated by the fission power reduction at the fuel pebbles and by the safe design of the nuclear reactor. As a consequence, the maximum temperature reached in the core was always less than the fuel melting point and the reactor was always in a safe condition. The heat transfer loop could suffer the rupture of a pipe in one of the scenarios, and design modifications to address this were suggested. This thesis' results partially prove that nuclear hydrogen production plants could be safe, and simultaneously, that equation-based simulators are good platforms to demonstrate the safety of these plants. Developing these models and tests further will help guarantee the safety of the plant and obtain regulatory and public approval for this new nuclear application.
by Patricio D. Ramírez Muñoz.
Ph.D.
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McCoy, Timothy J. (Timothy John). "Dynamic simulation of shipboard electric power systems." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12495.
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Swanson, Davin Karl. "Dynamic simulation of an improved passive haptic display." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17292.
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Siu, Daniel. "Stochastic Hybrid Dynamic Systems: Modeling, Estimation and Simulation." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4405.
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Stochastic hybrid dynamic systems that incorporate both continuous and discrete dynamics have been an area of great interest over the recent years. In view of applications, stochastic hybrid dynamic systems have been employed to diverse fields of studies, such as communication networks, air traffic management, and insurance risk models. The aim of the present study is to investigate properties of some classes of stochastic hybrid dynamic systems.
The class of stochastic hybrid dynamic systems investigated has random jumps driven by a non-homogeneous Poisson process and deterministic jumps triggered by hitting the boundary. Its real-valued continuous dynamic between jumps is described by stochastic differential equations of the It\^o-Doob type. Existing results of piecewise deterministic models are extended to obtain the infinitesimal generator of the stochastic hybrid dynamic systems through a martingale approach. Based on results of the infinitesimal generator, some stochastic stability results are derived. The infinitesimal generator and stochastic stability results can be used to compute the higher moments of the solution process and find a bound of the solution.
Next, the study focuses on a class of multidimensional stochastic hybrid dynamic systems. The continuous dynamic of the systems under investigation is described by a linear non-homogeneous systems of It\^o-Doob type of stochastic differential equations with switching coefficients. The switching takes place at random jump times which are governed by a non-homogeneous Poisson process. Closed form solutions of the stochastic hybrid dynamic systems are obtained. Two important special cases for the above systems are the geometric Brownian motion process with jumps and the Ornstein-Uhlenbeck process with jumps. Based on the closed form solutions, the probability distributions of the solution processes for these two special cases are derived. The derivation employs the use of the modal matrix and transformations.
In addition, the parameter estimation problem for the one-dimensional cases of the geometric Brownian motion and Ornstein-Uhlenbeck processes with jumps are investigated. Through some existing and modified methods, the estimation procedure is presented by first estimating the parameters of the discrete dynamic and subsequently examining the continuous dynamic piecewisely.
Finally, some simulated stochastic hybrid dynamic processes are presented to illustrate the aforementioned parameter-estimation methods. One simulated insurance example is given to demonstrate the use of the estimation and simulation techniques to obtain some desired quantities.
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Lilly, Kathryn Weed. "Efficient dynamic simulation of multiple chain robotic systems /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487670346873809.
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PREMKUMAR, SRIDHAR. "A UNIFIED SIMULATOR FOR MULTI-DOMAIN SIMULATION OF SYSTEMS USING DYNAMIC INTERPRETATION." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1172859432.
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Geitner, Gert-Helge, and Guven Komurgoz. "Power Flow Modelling of Dynamic Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-171305.
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As tools for dynamic system modelling both conventional methods such as transfer function or state space representation and modern power flow based methods are available. The latter methods do not depend on energy domain, are able to preserve physical system structures, visualize power conversion or coupling or split, identify power losses or storage, run on conventional software and emphasize the relevance of energy as basic principle of known physical domains. Nevertheless common control structures as well as analysis and design tools may still be applied. Furthermore the generalization of power flow methods as pseudo-power flow provides with a universal tool for any dynamic modelling. The phenomenon of power flow constitutes an up to date education methodology. Thus the paper summarizes fundamentals of selected power flow oriented modelling methods, presents a Bond Graph block library for teaching power oriented modelling as compact menu-driven freeware, introduces selected examples and discusses special features.
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Posse, Ernesto. "Modelling and simulation of dynamic-structure discrete-event systems." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22006.
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Discrete-event modelling and simulation has become an established approach to the description and study of complex dynamic systems. In recent years there has been an increased interest in modelling complex dynamic-structure systems, i.e., systems whose structure changes over time. Such systems are generally more difficult to understand and analyze than systems with a static structure. These challenges can be met by the development of appropriate modelling formalisms based on a solid foundation and with suitable supporting tools. In this thesis we explore an approach to modelling and simulation of dynamic-structure discrete-event systems based on process algebra. The thesis consists of two parts. We begin by exploring, in the first part, a formalism for static-structure discrete-event modelling and simulation called the Discrete-EVent System Specification formalism (DEVS [Zeigler 76, 2000].) We develop an alternative theoretical foundation for DEVS based on Structural Operational Semantics, focusing on determinism and compositionality properties. In the second part we develop a modelling language for dynamic-structure discrete-event systems named kiltera, based on process algebras and incorporating elements from discrete-event modelling. This language, based on the \pi-calculus [Milner 89], allows us to describe and reason about timed, mobile and distributed discrete-event systems in a single framework. We develop a theoretical foundation based on Structural Operational Semantics and establish fundamental properties concerning time-determinism, continuity, compositionality and legitimacy. We build a simulator for the language which supports both sequential and distributed execution of models, based on a variant of the Time Warp algorithm [Jefferson 85]. Finally we apply this language to the modelling and simulation of traffic.La modélisation et la simulation à événements discrets constituent une approche bien établie pour la description et l'étude des systèmes dynamiques complexes. Ces dernières années, il y a eu un regain d'intérêt pour la modélisation des systèmes complexes à structure dynamique. Ces systèmes sont généralement plus difficiles à comprendre et à analyser que les systèmes ayant une structure statique. Cette analyse et cette compréhension peuvent être développées à l'aide de formalismes de modélisation fondés sur une base solide et des outils appropriés. Dans cette thèse, nous explorons une approche de modélisation et de simulation des systèmes à événements discrets fondée sur l'algèbre de processus. Ce document se compose de deux parties. Dans la première partie, nous étudions ce que l'on appelle le formalisme Discrete-EVent System Specifications (DEVS.) Nous développons un autre fondement théorique pour DEVS fondée sur la sémantique opérationnelle structurelle, en mettant l'accent sur les propriétés de déterminisme et de compositionalité. Dans la deuxième partie, nous développons un langage de modélisation pour systèmes à structure dynamique nommé kiltera, en nous fondant sur les algèbres de processus et en incorporant des éléments de modélisation à événements discrets. Ce langage, en se fondant sur le \pi-calcul, nous permet de décrire et de raisonner sur les systèmes mobiles, distribués et au temps-réel, à événements discrets, dans un cadre conceptuel unique. Nous développons une base théorique fondée sur la sémantique opérationnelle structurelle et nous établissons des propriétés fondamentales concernant le déterminisme-temps, la continuité, la compositionalité et la légitimité. Nous construisons un simulateur pour le langage qui supporte à la fois l'exécution séquentielle et distribuée de modèles, en utilisant une variante de l'algorithme Time Warp. Enfin, nous appliquons ce la
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Gai, Huifa. "Automatic generation of diagonal matrices for dynamic simulation systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq30473.pdf.
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Tariku, Fitsum. "Simulation of dynamic mechanical systems with stick-slip friction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/MQ38415.pdf.
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Roa-Sepulveda, C. A. "Dynamic simulation of voltage instability phenomena in power systems." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390456.
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Störkle, Johannes [Verfasser]. "Dynamic Simulation and Control of Optical Systems / Johannes Störkle." Aachen : Shaker, 2018. http://d-nb.info/1188549391/34.
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Shen, Qiang. "Fuzzy qualitative simulation and diagnosis of continuous dynamic systems." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/829.
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See, Chong Wee Simon. "Numerical methods for the simulation of dynamic discontinuous systems." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358276.
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Demiray, Turhan Hilmi. "Simulation of power system dynamics using dynamic phasor models /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17607.
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Damle, Pushkar Hari. "A system dynamics model of the integration of new technologies for ship systems." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/35216.
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System dynamics has been used to better understand the dynamics within complex natural and social systems. This understanding enables us to make decisions and define strategies that help to resolve the problematic behaviors associated within these systems. For example within an operating environment such as the US Navy, decisions taken today can have long lasting impact on system performance. The Navy has experienced large cost overruns during the new technology implementation process on ship systems that can also have an impact on total life cycle performance. The integration phase of the implementation process represents most of the cost overruns experienced in the overall new technology life cycle (development, integration, and operation/support/disposal). We have observed a general concern that there is a lack of understanding for the dynamic behavior of those processes which comprise the integration phase, among ship-builders and planners. One of the goals of our research effort has been to better understand the dynamic behavior of the new technology integration processes, using a dynamic modeling technique known as System Dynamics.
Our approach has also been to provide a comprehensive knowledge elicitation process in which members from the shipbuilding industry, the US Navy, and the Virginia Tech System Performance Laboratory take part in group model building exercises. The system dynamics model that is developed in this manner is based on data obtained from the experts. An investigation of these dynamics yields a dominant cost behavior that characterizes the technology integration processes. This behavior is S-shaped growth.
The following two dynamic hypotheses relative to lifecycle cost and performance of the inserted new technology were confirmed: (1) For the current structure of the model we observe the more the complexity of the new technology, the less affordable a technology becomes; (2) Integration of immature (less developed) technologies is associated with higher costs. Another interesting insight is that cost is very sensitive to the material procurement.
Future research can be addressed to a more detailed level of abstraction for various activities included in the technology integration phase, such as testing and evaluation, cost of rework and risks associated with inadequate testing etc. This will add to our evolving understanding of the behavior of individual activities in the technology integration process.Master of Science
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Dehlin, Jonas, and Joakim Löf. "Dynamic Infrared Simulation : A Feasibility Study of a Physically Based Infrared Simulation Model." Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7993.
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The increased usage of infrared sensors by pilots has created a growing demand for simulated environments based on infrared radiation. This has led to an increased need for Saab to refine their existing model for simulating real-time infrared imagery, resulting in the carrying through of this thesis. Saab develops the Gripen aircraft, and they provide training simulators where pilots can train in a realistic environment. The new model is required to be based on the real-world behavior of infrared radiation, and furthermore, unlike Saab's existing model, have dynamically changeable attributes.
This thesis seeks to develop a simulation model compliant with the requirements presented by Saab, and to develop the implementation of a test environment demonstrating the features and capabilities of the proposed model. All through the development of the model, the pilot training value has been kept in mind.
The first part of the thesis consists of a literature study to build a theoretical base for the rest of the work. This is followed by the development of the simulation model itself and a subsequent implementation thereof. The simulation model and the test implementation are evaluated as the final step conducted within the framework of this thesis.
The main conclusions of this thesis first of all includes that the proposed simulation model does in fact have its foundation in physics. It is further concluded that certain attributes of the model, such as time of day, are dynamically changeable as requested. Furthermore, the test implementation is considered to have been feasibly integrated with the current simulation environment.
A plan concluding how to proceed has also been developed. The plan suggests future work with the proposed simulation model, since the evaluation shows that it performs well in comparison to the existing model as well as other products on the market.
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Eatock, Julie. "Dynamic integrated modelling of information systems and business process simulation." Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/5248.
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Business processes and information technology are two areas that are very closely related to the sustained competitive advantage in organisations. However, investment in information technology often leads to disappointment, which may in part be due to the non-alignment of the information system domain with the business process domain. Simulation modelling is an established technique often used in business process change projects, as it allows a comparison of different possible scenarios without the expense of physically implementing the system. However business process simulation fails to effectively capture the information systems perspective in the model. This thesis contends that by combining information systems modelling techniques with business process simulation the model will be able to capture all the four perspectives (functional, behavioural, organisational and informational) of an organisation, and the design of the business processes and the information system will be better aligned. Initially, attempts were made to integrate business process simulation with computer network simulation in a simple two- or three-layered simulation model, but this gave rise to significant problems the most significant being the underlying assumptions of the original hypothesis. This led to a refined hypothesis in which the layered models were discarded along with the network domain. The revised hypothesis aimed to capture the informational changes that occur in the information system and therefore combines prototyping with business process simulation. This overcomes the unsafe assumptions of the initial hypothesis about whether the system is 'correct' and provides a method of validating the design of the information system within the context of the business processes. The integrated model allows concurrent design of the information system domain and the business process domain and therefore ensures that the domains are better aligned. The framework is tested on a case study and the results indicate that it is an effective tool in the combined design of business processes and information systems.
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Ramli, Rahizar. "Dynamic simulation of semi-active suspension systems for durability analysis." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/314/.
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The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly for improvement in ride and handling, over the passive system. However, the durability of the suspension components resulting from this implementation received very little attention. Therefore, this research aims to examine the effect of employing a selection of semi-active control strategies on the components' durability. To achieve this early in the design cycle, accurate representations of the load histories must be generated as these histories are the prerequisite in predicting fatigue life. This requires an alternative modelling and simulation approach capable of combining the complexity of vehicle suspensions with semi-active controller models, and at the same time capable of maintaining accurate dynamic responses. In realizing this objective, a multi-body cosimulation approach has been proposed to predict these loads. Initially, efforts are centred on verifying the proposed method against conventional modelling and simulation techniques. This is followed by the evaluating the responses of vehicle suspension models of different complexities fitted with a selection of semi-active control strategies when subjected to transient and random road inputs. In an attempt to demonstrate the flexibility of MBS cosimulation, a magnetorheological damper model derived from experimental data is introduced,in which its dynamic characteristics and dynamic response are examined. It is concluded that the proposed method is capable of producing reasonably accurate load histories but at the expense of increasing solution time. Evaluation of the durability of a lower suspension arm of a multi-purpose passenger vehicle suggested that the two state semi-active strategies with skyhook damping control produced shorter fatigue life than from the conventional passives suspension systems.
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Jeihani, Koohbanani Mansoureh. "Enhancements to Transportation Analysis and Simulation Systems." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/30092.
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Urban travel demand forecasting and traffic assignment models are important tools in developing transportation plans for a metropolitan area. These tools provide forecasts of urban travel patterns under various transportation supply conditions. The predicted travel patterns then provide useful information in planning the transportation system. Traffic assignment is the assignment of origin-destination flows to transportation routes, based on factors that affect route choice.
The urban travel demand models, developed in the mid 1950s, provided accurate and precise answers to the planning and policy issues being addressed at that time, which mainly revolved around expansion of the highway system to meet the rapidly growing travel demand. However, the urban transportation planning and analysis have undergone changes over the years, while the structure of the travel demand models has remained largely unchanged except for the introduction of disaggregate choice models beginning in the mid-1970s. Legislative and analytical requirements that exceed the capabilities of these models and methodologies have driven new technical approaches such as TRANSIMS.
The Transportation Analysis and Simulation System, or TRANSIMS, is an integrated system of travel forecasting models designed to give transportation planners accurate, and complete information on traffic impacts, congestion, and pollution. It was developed by the Los Alamos National Laboratory to address new transportation and air quality forecasting procedures required by the Clean Air Act, the Intermodal Surface Transportation Efficiency Act, and other regulations.
TRANSIMS includes six different modules: Population Synthesizer, Activity Generator, Route Planner, Microsimulator, Emissions Estimator, and Feedback. This package has been under development since 1994 and needs significant improvements within some of its modules. This dissertation enhances the interaction between the Route Planner and the Microsimulator modules to improve the dynamic traffic assignment process in TRANSIMS, and the Emissions Estimator module.
The traditional trip assignment is static in nature. Static assignment models assume that traffic is in a steady-state, link volumes are time invariant, the time to traverse a link depends only on the number of vehicles on that link, and that the vehicle queues are stacked vertically and do not traverse to the upstream links in the network. Thus, a matrix of steady-state origin-destination (O-D) trip rates is assigned simultaneously to shortest paths from each origin to a destination. To address the static traffic assignment problems, dynamic traffic assignment models are proposed. In dynamic traffic assignment models, the demand is allowed to be time varying so that the number of vehicles passing through a link and the corresponding link travel times become time-dependent. In contrast with the static case, the dynamic traffic assignment problem is still relatively unexplored and a precise formulation is not clearly established. Most models in the literature do not present a solution algorithm and among the presented methods, most of them are not suitable for large-scale networks. Among the suggested solution methodologies that claim to be applicable to large-scale networks, very few methods have been actually tested on such large-scale networks. Furthermore, most of these models have stability and convergence problem.
A solution methodology for computing dynamic user equilibria in large-scale transportation networks is presented in this dissertation. This method, which stems from the convex simplex method, routes one traveler at a time on the network and updates the link volumes and link travel times after each routing. Therefore, this method is dynamic in two aspects: it is time-dependent, and it routes travelers based on the most updated link travel times. To guarantee finite termination, an additional stopping criterion is adopted.
The proposed model is implemented within TRANSIMS, the Transportation Analysis and Simulation System, and is applied to a large-scale network. The current user equilibrium computation in TRANSIMS involves simply an iterative process between the Route Planner and the MicroSimulator modules. In the first run, the Route Planner uses free-flow speeds on each link to estimate the travel time to find the shortest paths, which is not accurate because there exist other vehicles on the link and so, the speed is not simply equal to the free-flow speed. Therefore, some paths might not be the shortest paths due to congestion. The Microsimulator produces the new travel times based on accurate vehicle speeds. These travel times are fed back to the Route Planner, and the new routes are determined as the shortest paths for selected travelers. This procedure does not necessarily lead to a user equilibrium solution. The existing problems in this procedure are addressed in our proposed algorithm as follows.
TRANSIMS routes one person at a time but does not update link travel times. Therefore, each traveler is routed regardless of other travelers on the network. The current stopping criterion is based only on visualization and the procedure might oscillate. Also, the current traffic assignment spends a huge amount of time by iterating frequently between the Route Planner and the Microsimulator. For example in the Portland study, 21 iterations between the Route Planner and the Microsimulator were performed that took 33:29 hours using three 500-MHZ CPUs (parallel processing). These difficulties are addressed by distributing travelers on the network in a better manner from the beginning in the Route Planner to avoid the frequent iterations between the Route Planner and the Microsimulator that are required to redistribute them. By updating the link travel times using a link performance function, a near-equilibrium is obtained only in one iteration. Travelers are distributed in the network with regard to other travelers in the first iteration; therefore, there is no need to redistribute them using the time-consuming iterative process. To avoid problems caused by link performance function usage, an iterative procedure between the current Route Planner and the Microsimulator is performed and a user equilibrium is found after a few iterations. Using an appropriate descent-based stopping criterion, the finite termination of the procedure is guaranteed. An illustration using real-data pertaining to the transportation network of Portland, Oregon, is presented along with comparative analyses.
TRANSIMS framework contains a vehicle emissions module that estimates tailpipe emissions for light and heavy duty vehicles and evaporative emissions for light duty vehicles. It uses as inputs the emissions arrays obtained the Comprehensive Modal Emissions Model (CMEM). This dissertation describes and validates the framework of TRANSIMS for modeling vehicle emissions. Specifically, it identifies an error in the model calculations and enhances the emission modeling formulation. Furthermore, the dissertation compares the TRANSIMS emission estimates to on-road emission-measurements and other state-of-the-art emission models including the VT-Micro and CMEM models.Ph. D.
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Chapman, D. A. "Theory for three dimensional dynamic simulation of towed cable-body systems." Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378147.
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Jones, Daniel. "High speed simulation of microprocessor systems using LTU dynamic binary translation." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4609.
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This thesis presents new simulation techniques designed to speed up the simulation of microprocessor systems. The advanced simulation techniques may be applied to the simulator class which employs dynamic binary translation as its underlying technology. This research supports the hypothesis that faster simulation speeds can be realized by translating larger sections of the target program at runtime. The primary motivation for this research was to help facilitate comprehensive design-space exploration and hardware/software co-design of novel processor architectures by reducing the time required to run simulations. Instruction set simulators are used to design and to verify new system architectures, and to develop software in parallel with hardware. However, compromises must often be made when performing these tasks due to time constraints. This is particularly true in the embedded systems domain where there is a short time-to-market. The processing demands placed on simulation platforms are exacerbated further by the need to simulate the increasingly complex, multi-core processors of tomorrow. High speed simulators are therefore essential to reducing the time required to design and test advanced microprocessors, enabling new systems to be released ahead of the competition. Dynamic binary translation based simulators typically translate small sections of the target program at runtime. This research considers the translation of larger units of code in order to increase simulation speed. The new simulation techniques identify large sections of program code suitable for translation after analyzing a profile of the target program’s execution path built-up during simulation. The average instruction level simulation speed for the EEMBC benchmark suite is shown to be at least 63% faster for the new simulation techniques than for basic block dynamic binary translation based simulation and 14.8 times faster than interpretive simulation. The average cycle-approximate simulation speed is shown to be at least 32% faster for the new simulation techniques than for basic block dynamic binary translation based simulation and 8.37 times faster than cycle-accurate interpretive simulation.
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Wu, Hongyu. "Parallel methods for static and dynamic simulation of flexible pavement systems /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/10158.
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El-Hadad, Kamel Abdelsalam Mahmoud. "Expert systems and simulation : an investigation of an expert system to facilitate the development and use of system dynamic simulation models." Thesis, University of Kent, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279602.
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Bousnane, Kafiha. "Real-time power system dynamic simulation." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6623/.
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The present day digital computing resources are overburdened by the amount of calculation necessary for power system dynamic simulation. Although the hardware has improved significantly, the expansion of the interconnected systems, and the requirement for more detailed models with frequent solutions have increased the need for simulating these systems in real time. To achieve this, more effort has been devoted to developing and improving the application of numerical methods and computational techniques such as sparsity-directed approaches and network decomposition to power system dynamic studies. This project is a modest contribution towards solving this problem. It consists of applying a very efficient sparsity technique to the power system dynamic simulator under a wide range of events. The method used was first developed by Zollenkopf (^117) Following the structure of the linear equations related to power system dynamic simulator models, the original algorithm which was conceived for scalar calculation has been modified to use sets of 2 * 2 sub-matrices for both the dynamic and algebraic equations. The realisation of real-time simulators also requires the simplification of the power system models and the adoption of a few assumptions such as neglecting short time constants. Most of the network components are simulated. The generating units include synchronous generators and their local controllers, and the simulated network is composed of transmission lines and transformers with tap-changing and phase-shifting, non-linear static loads, shunt compensators and simplified protection. The simulator is capable of handling some of the severe events which occur in power systems such as islanding, island re-synchronisation and generator start-up and shut-down. To avoid the stiffness problem and ensure the numerical stability of the system at long time steps at a reasonable accuracy, the implicit trapezoidal rule is used for discretising the dynamic equations. The algebraisation of differential equations requires an iterative process. Also the non-linear network models are generally better solved by the Newton-Raphson iterative method which has an efficient quadratic rate of convergence. This has favoured the adoption of the simultaneous technique over the classical partitioned method. In this case the algebraised differential equations and the non-linear static equations are solved as one set of algebraic equations. Another way of speeding-up centralised simulators is the adoption of distributed techniques. In this case the simulated networks are subdivided into areas which are computed by a multi-task machine (Perkin Elmer PE3230). A coordinating subprogram is necessary to synchronise and control the computation of the different areas, and perform the overall solution of the system. In addition to this decomposed algorithm the developed technique is also implemented in the parallel simulator running on the Array Processor FPS 5205 attached to a Perkin Elmer PE 3230 minicomputer, and a centralised version run on the host computer. Testing these simulators on three networks under a range of events would allow for the assessment of the algorithm and the selection of the best candidate hardware structure to be used as a dedicated machine to support the dynamic simulator. The results obtained from this dynamic simulator are very impressive. Great speed-up is realised, stable solutions under very severe events are obtained showing the robustness of the system, and accurate long-term results are obtained. Therefore, the present simulator provides a realistic test bed to the Energy Management System. It can also be used for other purposes such as operator training.
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Beard, Gregory Stuart. "Adaptive control of energy efficient hydraulic systems." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266978.
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Luo, Robert Keqi. "Fatigue life evaluation of railway vehicle bogies using an integrated dynamic simulation." Thesis, London South Bank University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358233.
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Butler, Brian Jeffrey. "Dynamic Model Creation and Scripting Support in the Horizon Simulation Framework." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/697.
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Dynamic model creation and support for the Lua scripting language was added to the Horizon Simulation Framework used for the verification and validation of system-level requirements. The addition of scripting support allows for subsystem models and their algorithms to be defined using a simpler scripting language, rather than C++. The Luabind library by Rasterbind software is used to expose the C++ algorithms and classes to Lua that are already defined in the framework. Interoperability between Lua and C++ code allows for the ease of use of a scripting language while utilizing the utility classes and functions already created. The dynamic model creation algorithm developed allows for the structure and logic of the simulated system to be defined completely using XML and text files as input to the framework. Dynamic model creation prevents the need to re-compile the framework every time small changes are made and greatly simplifies the changes required to simulate a different model. A runtime analysis shows that using a scripting language does not decrease the performance significantly, while increasing usability and decreasing the time required to set up simulations. Tests where the scripted code uses only classes and function exposed by luabind show that there is virtually no performance decrease when compared to the same algorithms in C++. Performance decreases as more of the algorithm implemented is executed in Lua. An example test scenario that represents the typical use of the framework showed only a minor decrease in performance. The multi-threaded scheduler developed works with the scripting support and allows for modern multi-core or multi-processor computers to be used most efficiently for simulations. This thesis describes the algorithms of dynamic model creation and scripting support, as well as the methodology used to expose C++ code to Lua. This thesis also presents the architecture changes required to support dynamic model creation, scripting support, and multi-threaded scheduling. Finally, runtime results of the added scripting support are presented.
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Rupp, Matthew Y. "Passive dynamic steering system model for use in vehicle dynamics simulation." Connect to resource, 1994. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1157568618.
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Maree, Charl. "Diagnostic monitoring of dynamic systems using artificial immune systems." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/1780.
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Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006.The natural immune system is an exceptional pattern recognition system based on memory and learning that is capable of detecting both known and unknown pathogens. Artificial immune systems (AIS) employ some of the functionalities of the natural immune system in detecting change in dynamic process systems. The emerging field of artificial immune systems has enormous potential in the application of fault detection systems in process engineering. This thesis aims to firstly familiarise the reader with the various current methods in the field of fault detection and identification. Secondly, the notion of artificial immune systems is to be introduced and explained. Finally, this thesis aims to investigate the performance of AIS on data gathered from simulated case studies both with and without noise. Three different methods of generating detectors are used to monitor various different processes for anomalous events. These are: (1) Random Generation of detectors, (2) Convex Hulls, (3) The Hypercube Vertex Approach. It is found that random generation provides a reasonable rate of detection, while convex hulls fail to achieve the required objectives. The hypercube vertex method achieved the highest detection rate and lowest false alarm rate in all case studies. The hypercube vertex method originates from this project and is the recommended method for use with all real valued systems, with a small number of variables at least. It is found that, in some cases AIS are capable of perfect classification, where 100% of anomalous events are identified and no false alarms are generated. Noise has, expectedly so, some effect on the detection capability on all case studies. The computational cost of the various methods is compared, which concluded that the hypercube vertex method had a higher cost than other methods researched. This increased computational cost is however not exceeding reasonable confines therefore the hypercube vertex method nonetheless remains the chosen method. The thesis concludes with considering AIS’s performance in the comparative criteria for diagnostic methods. It is found that AIS compare well to current methods and that some of their limitations are indeed solved and their abilities surpassed in certain cases. Recommendations are made to future study in the field of AIS. Further the use of the Hypercube Vertex method is highly recommended in real valued scenarios such as Process Engineering.
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De, Queiroz Lima Roberta. "Modeling and simulation in nonlinear stochastic dynamic of coupled systems and impact." Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1049/document.
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Dans cette Thèse, la conception robuste avec un modèle incertain d'un système électromécanique avec vibro-impact est fait. Le système électromécanique est constitué d'un chariot, dont le mouvement est excité par un moteur à courant continu et un marteau embarqué dans ce chariot. Le marteau est relié au chariot par un ressort non linéaire et par un amortisseur linéaire, de façon qu'un mouvement relatif existe entre eux. Une barrière flexible linéaire, placé à l'extérieur du chariot limite les mouvements de marteau. En raison du mouvement relatif entre le marteau et la barrière, impacts peuvent se produire entre ces deux éléments. Le modèle du système développé prend en compte l'influence du courant continu moteur dans le comportement dynamique du système. Certains paramètres du système sont incertains, tels comme les coefficients de rigidité et d'amortissement de la barrière flexible. L'objectif de la Thèse est de réaliser une optimisation de ce système électromécanique par rapport aux paramètres de conception afin de maximiser l'impact puissance sous la contrainte que la puissance électrique consommée par le moteur à courant continu est inférieure à une valeur maximale. Pour choisir les paramètres de conception dans le problème d'optimisation, une analyse de sensibilité a été réalisée afin de définir les paramètres du système les plus sensibles. L'optimisation est formulée dans le cadre de la conception robuste en raison de la présence d'incertitudes dans le modèle. Les lois de probabilités liées aux variables aléatoires du problème sont construites en utilisant le Principe du Maximum l'Entropie et les statistiques de la réponse stochastique du système sont calculées en utilisant la méthode de Monte Carlo. L'ensemble d'équations non linéaires sont présentés, et un solveur temporel adapté est développé. Le problème d'optimisation non linéaire stochastique est résolu pour différents niveaux d'incertitudes, et aussi pour le cas déterministe. Les résultats sont différents, ce qui montre l'importance de la modélisation stochastiqueIn this Thesis, the robust design with an uncertain model of a vibro-impact electromechanical system is done. The electromechanical system is composed of a cart, whose motion is excited by a DC motor (motor with continuous current), and an embarked hammer into this cart. The hammer is connected to the cart by a nonlinear spring component and by a linear damper, so that a relative motion exists between them. A linear flexible barrier, placed outside of the cart, constrains the hammer movements. Due to the relative movement between the hammer and the barrier, impacts can occur between these two elements. The developed model of the system takes into account the influence of the DC motor in the dynamic behavior of the system. Some system parameters are uncertain, such as the stiffness and the damping coefficients of the flexible barrier. The objective of the Thesis is to perform an optimization of this electromechanical system with respect to design parameters in order to maximize the impact power under the constraint that the electric power consumed by the DC motor is lower than a maximum value. To chose the design parameters in the optimization problem, an sensitivity analysis was performed in order to define the most sensitive system parameters. The optimization is formulated in the framework of robust design due to the presence of uncertainties in the model. The probability distributions of random variables are constructed using the Maximum Entropy Principle and statistics of the stochastic response of the system are computed using the Monte Carlo method. The set of nonlinear equations are presented, and an adapted time domain solver is developed. The stochastic nonlinear constrained design optimization problem is solved for different levels of uncertainties, and also for the deterministic case. The results are different and this show the importance of the stochastic modeling
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Hu, Yunwei. "A guided simulation methodology for dynamic probabilistic risk assessment of complex systems." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2472.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Cho, Hee Jin. "DYNAMIC SIMULATION AND OPTIMAL REAL-TIME OPERATION OF CHP SYSTEMS FOR BUILDINGS." MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-03312009-144452/.
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Combined Cooling, Heating, and Power (CHP) systems have been widely recognized as a key alternative for electric and thermal energy generation because of their outstanding energy efficiency, reduced environmental emissions, and relative independence from centralized power grids. The systems provide simultaneous onsite or near-site electric and thermal energy generation in a single, integrated package. As CHP becomes increasingly popular worldwide and its total capacity increases rapidly, the research on the topics of CHP performance assessment, design, and operational strategy become increasingly important. Following this trend of research activities to improve energy efficiency, environmental emissions, and operational cost, this dissertation focuses on the following aspects: (a) performance evaluation of a CHP system using a transient simulation model; (b) development of a dynamic simulation model of a power generation unit that can be effectively used in transient simulations of CHP systems; (c) investigation of real-time operation of CHP systems based on optimization with respect to operational cost, primary energy consumption, and carbon dioxide emissions; and (d) development of optimal supervisory feed-forward control that can provide realistic real-time operation of CHP systems with electric and thermal energy storages using short-term weather forecasting. The results from a transient simulation of a CHP system show that technical and economical performance can be readily evaluated using the transient model and that the design, component selection, and control of a CHP system can be improved using this model. The results from the case studies using optimal real-time operation strategies demonstrate that CHP systems with an energy dispatch algorithm have the potential to yield savings in operational cost, primary energy consumption, and carbon dioxide emissions with respect to a conventional HVAC system. Finally, the results from the case study using a supervisory feed-forward control system illustrate that optimal realistic real-time operation of CHP systems with electric and thermal energy storages can be managed by this optimal control using weather forecasting information.
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Störkle, Johannes [Verfasser], and Peter [Akademischer Betreuer] Eberhard. "Dynamic simulation and control of optical systems / Johannes Störkle ; Betreuer: Peter Eberhard." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/1177041014/34.
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Bouwer, Werner. "Designing a dynamic thermal and energy system simulation scheme for cross industry applications / W. Bouwer." Thesis, North-West University, 2004. http://hdl.handle.net/10394/592.
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The South African economy, which is largely based on heavy industry such as minerals
extraction and processing, is by nature very energy intensive. Based on the abundance of coal
resources, electricity in South Africa remains amongst the cheapest in the world. Whilst the
low electricity price has contributed towards a competitive position, it has also meant that our
existing electricity supply is often taken for granted. The economic and environmental
benefits of energy efficiency have been well documented. Worldwide, nations are beginning
to face up to the challenge of sustainable energy - in other words to alter the way that energy
is utilised so that social, environmental and economic aims of sustainable development are
supported.
South Africa as a developing nation recognises the need for energy efficiency, as it is the most
cost effective way of meeting the demands of sustainable development. South Africa, with its
unique economic, environmental and social challenges, stands to benefit the most from
implementing energy efficiency practices. The Energy Efficiency Strategy for South Africa
takes its mandate from the South African White Paper on Energy Policy. It is the first
consolidated governmental effort geared towards energy efficiency practices throughout
South Africa. The strategy allows for the immediate implementation of low-cost and no-cost
interventions, as well as those higher-cost measures with short payback periods. An initial
target has been set for an across sector energy efficiency improvement of 12% by 2014.
Thermal and energy system simulation is globally recognised as one of the most effective and
powerful tools to improve overall energy efficiency. However, because of the usual extreme
mathematical nature of most simulation algorithms, coupled with the historically academic
environment in which most simulation software is developed, valid perceptions exist that
system simulation is too time consuming and cumbersome. It is also commonly known that
system simulation is only effective in the hands of highly skilled operators, which are
specialists in their prospective fields. Through previous work done in the field, and the design
of a dynamic thermal and energy system simulation scheme for cross industry applications, it
was shown that system simulation has evolved to such an extent that these perceptions are not
valid any more.
The South African mining and commercial building industries are two of the major
consumers of electricity within South Africa. By improving energy efficiency practices within
the building and mining industry, large savings can be realised. An extensive investigation of
the literature showed that no general suitable computer simulation software for cross industry
mining and building thermal and energy system simulation could be found. Because the
heating, ventilation and air conditioning (HVAC) of buildings, closely relate to the ventilation
and cooling systems of mines, valuable knowledge from this field was used to identify the
requirements and specifications for the design of a new single cross industry dynamic
integrated thermal and energy system simulation tool.
VISUALQEC was designed and implemented to comply with the needs and requirements
identified. A new explicit system component model and explicit system simulation engine,
combined with a new improved simulation of mass flow through a system procedure,
suggested a marked improvement on overall simulation stability, efficiency and speed. The
commercial usability of the new simulation tool was verified for building applications by
doing an extensive building energy savings audit. The new simulation tool was further
verified by simulating the ventilation and cooling (VC) and underground pumping system of a
typical South African gold mine. Initial results proved satisfactory but, more case studies to
further verify the accuracy of the implemented cross industry thermal and energy system
simulation tool are needed. Because of the stable nature of the new VISUALQEC simulation
engine, the power of the simulation process can be further extended to the mathematical
optimisation of various system variables.
In conclusion, this study highlighted the need for new simulation procedures and system
designs for the successful implementation and creation of a single dynamic thermal and
energy system simulation tool for cross industry applications. South Africa should take full
advantage of the power of thermal and energy system simulation towards creating a more
energy efficient society.Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2005.
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McDonagh, Kieran D. "Systems Dynamics Simulation To Improve Timber Harvesting System Management." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35184.
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Two computer simulation models were developed to address harvest system - stand assignment and wood flow variability problems in the southeast United States.
The Harvest System Assignment (HSA) model is used to evaluate the impact of a particular stand assignment on harvest system effectiveness and is designed to assist with harvest system assignment decisions. Four general harvesting systems: manual, mechanized, shovel and cut-to-length can be modeled to harvest timber, from standing trees to processed logs loaded on to trucks. Model testing showed that as terrain, tract and system characteristics changed, the effectiveness of each of the four systems varied. The most effective system can be determined for any combination of terrain, tract and system characteristics. The model output shows production potential as well as cost per unit, and identifies the causes and magnitude of inefficiency.
The Machine Allocation (MA) model is used to evaluate the potential of a given machine combination and is designed as a research tool to investigate the cause and impact of machine interactions. This model has a defined system structure and can incorporate up to five machines for each of three phases in the harvesting operation: felling, skidding and processing. Particular system configurations can be evaluated and possible improvements to machine combination determined.
The HSA model is a widely applicable tool that will be available for industry in the southeastern United States. It has utility for training of personnel and for operational use. The MA model is a detailed tool that will be used in a research capacity to advance harvesting system management.Master of Science
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Oyarbide, Zubillaga Aitor. "Manufacturing systems simulation using the principles of system dynamics." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/12141.
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Manufacturing is the largest single contributor to the global economy. The evolution of consumer demands has pressurised companies into producing a larger variety of products, with improved specifications, reduced costs, and shorter lead times. In this context, companies have found simulation techniques useful in their manufacturing systems design processes; simulation based on Discrete Event Simulation (DES) is the preferred technique. The complexity of manufacturing systems, and the mechanisms of DES, means that the simulation task often consumes excessive time and resources, such as data, software, and training. Evidence suggests that an alternative modelling technique, named System Dynamics (SD), is also appropriate for conducting this task. SD has been applied successfully in other fields, where its graphical notation is considered beneficial. However, the lack of an SD tool that is tailored toward manufacturing systems has prevented industry from adopting this technique more extensively. This thesis determines the extent to which SD can provide a credible alternative to DES in the manufacturing system design process. Information concerning DES, SD and practitioners' needs was gathered from published literature and from an interview survey. A functional prototype of a tool based on the SD principles, but tailored to model manufacturing systems was then developed. Three case studies then provided valuable information concerning the requirements of industry and the capabilities of the SD technique. This research programme has found SD to be sufficiently accurate and quicker than DES tools under certain conditions, requiring less data and skills. In addition, the user interface appears to have had a significant impact on the lack of adoption of SD techniques within the manufacturing sector. Simp1ifications made by this technique can reduce both model building and model execution time, and thus, experimentation time. However, evidence suggests that DES is still more prevalent, and that further work is required to develop SD based tools tailored to manufacturing systems. Therefore, this thesis provides a much improved understanding of the capabilities of SD as an aid to manufacturing systems design.
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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.
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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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Han, Yong-Hee. "Dynamic Sequencing of Jobs on Conveyor Systems for Minimizing Changeovers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4877.
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This research investigates the problem of constrained sequencing of a set of jobs on a conveyor system with the objective of minimizing setup cost. A setup cost is associated with extra material, labor, or energy required due to the change of attributes in consecutive jobs at processing stations. A finite set of attributes is considered in this research. Sequencing is constrained by the availability of two elements ??orage buffers and conveyor junctions. The problem is motivated by the paint purge reduction problem at a major U.S. automotive manufacturer. First, a diverging junction with a sequence-independent setup cost and predefined attributes is modeled as an assignment problem and this model is extended by relaxing the initial assumptions in various ways. We also model the constrained sequencing problem with an off-line buffer and develop heuristics for efficiently getting a good quality solution by exploiting the special problem structure. Finally, we conduct sensitivity analysis using numerical experiments, explain the case study, and discuss the use of the simulation model as a supplementary tool for analyzing the constrained sequencing problem.
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Kim, Taewoo. "A 3D XML-based modeling and simulation framework for dynamic models." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1000134.
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Thesis (Ph. D.)--University of Florida, 2002.Title from title page of source document. Document formatted into pages; contains xii, 132 p.; also contains graphics. Includes vita. Includes bibliographical references.
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Ding, Wei. "Molecular dynamics simulation of biomembrane systems." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/36217.
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The fundamental structure of all biological membranes is the lipid bilayer. At- tributed to the multifaceted features of lipids and its dynamical interaction with other membrane-integrated molecules, the lipid bilayer is involved in a variety of physiological phenomena such as transmembrane transportation, cellular signalling transduction, energy storage, etc. Due to the nanoscale but high complexity of the lipid bilayer system, experimental investigation into many important processes at the molecular level is still challenging. Molecular dynamics (MD) simulation has been emerging as a powerful tool to study the lipid membrane at the nanoscale. Utilizing atomistic MD, we have quantitatively investigated the effect of lamellar and nonlamellar lipid composition changes on a series of important bilayer properties, and how membranes behave when exposed to a high-pressure environment. A series of membrane properties such as lateral pressure and dipole potential pro les are quanti ed. Results suggest the hypothesis that compositional changes, involving both lipid heads and tails, modulate crucial mechanical and electrical features of the lipid bilayer, so that a range of biological phenomena, such as the permeation through the membrane and conformational equilibria of membrane proteins, may be regulated. Furthermore, water also plays an essential role in the biomembrane system. To balance accuracy and efficiency in simulations, a coarse-grained ELBA water model was developed. Here, the ELBA water model is stress tested in terms of temperature- and pressure-related properties, as well as hydrating properties. Results show that the accuracy of the ELBA model is almost as good as conventional atomistic water models, while the computational efficiency is increased substantially.
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Sun, Mingqiu. "Molecular dynamics simulation of fluid systems /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849696964891.
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Daryabak, Mehdi. "Modeling line-commutated converter HVDC transmission systems using dynamic phasors." IEEE, 2013. http://hdl.handle.net/1993/31632.
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This thesis develops the dynamic phasor model of a line-commutated converter (LCC) high-voltage direct current (HVDC) transmission system. The mathematical definition and properties of dynamic phasors are utilized to model both the dc-side and the ac-side of a LCC-HVDC transmission system as well as 6-pulse Graetz bridge, which is the building block of such a system.
The developed model includes low-frequency dynamics of the systems, i.e., fundamental frequency component (50 Hz) at the ac-side and dc component at the dc-side, and removes high-frequency transients. The developed model, however, is capable of accommodating higher harmonics if necessary. The model is also able to simulate the system during abnormal modes of operations such as unbalanced operation and commutation failure. In order to develop the dynamic phasor model of a line-commutated converter, the concept of switching functions is utilized.
The developed model is capable of capturing large-signal transients of the system as well as steady state operating conditions. The model can be used in order to decrease the computational intensity of LCC-HVDC simulations. The developed model in this thesis enables the user to consider each harmonic component individually; this selective view of the components of the system response is not possible to achieve in conventional electromagnetic transient simulations.October 2016
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Chiniforoosh, Sina. "Generalized dynamic average modeling of line-commutated converter systems in transient simulation programs." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/41917.
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Power electronic converters are used in a wide range of applications as well as being the enabling technology for interfacing the alternative energy resources and many loads in modern power systems. The methodology of developing the so-called dynamic average-value models (AVMs) for such converters is based on averaging the variables (currents and voltages) within a switching interval resulting in numerically efficient models that are much more suitable than the detailed switching models for system-level studies as well as numerical linearization and the respective small-signal analysis. However, the AVMs available in the literature for line-commutated converters have several limitations such as neglecting the effects of losses, being only valid in certain operational modes and under balanced excitation, as well as employing a simplified representation of the multi-phase transformer in high-pulse-count converters. Moreover, a unified AVM methodology for high-pulse-count converters has not yet been established.
In this thesis, a generalized AVM methodology is developed for voltage-source- and rotating-machine-fed multi-pulse line-commutated converters for both classes of transient simulation software packages, i.e., state-variable-based and nodal-analysis-based electromagnetic transient program (EMTP) type. The previously-developed AVM approaches, i.e., analytical and parametric, are extended to the EMTP-type programs, and the indirect and direct methods of interfacing the models with external circuit-network are introduced and compared. For the machine-converter systems, the effects of machine and bridge losses are taken into account in the new AVM. Finally, a generalized dynamic AVM methodology is developed for high-pulse-count converters based on the parametric approach. An effective multi-phase transformer model is developed in transformed (qd0) and phase (abc) variables. An efficient transformer model is also developed, which accurately represents the multi-phase transformer using an equivalent three-phase formulation. The proposed generalized AVM remains valid for all operational modes under balanced and unbalanced excitation. This model is employed for AVM implementation in state-variable-based and EMTP-type programs. Extensive simulation and experimental studies are carried out on several example systems in order to compare the developed AVMs against the detailed and previously-developed average models in time- and frequency-domains. The results demonstrate the great accuracy of the proposed AVMs and a significant improvement compared to the previously-developed models.
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Garcia-Valle, Rodrigo Joel. "Dynamic modelling and simulation of electric power systems using the Newton-Raphson method." Thesis, University of Glasgow, 2007. http://theses.gla.ac.uk/435/.
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The research work presented in this thesis is concerned with the development of a dynamic power flow computer algorithm using Newton's method. It addresses both the development of a positive sequence dynamic power flow algorithm for the dynamic study of balanced power systems and a fully-fledged three-phase dynamic power flow algorithm for the dynamic study of power systems exhibiting a significant degree of either structural or operational unbalance. As a prelude to the research work on dynamic power flows, a three-phase Newton-Raphson power flow algorithm in rectangular co-ordinates with conventional HVDC power plant modelling is presented in this thesis, emphasising the representation of converter control modes. The solution approach takes advantage of the strong numerical solutions for combined HVAC-HVDC systems, where power plant and operational imbalances are explicitly taken into account. The dynamic algorithm is particularly suited to carrying out long-term dynamic simulations and voltage stability assessments. Dynamic model representations of the power plants components and the load tap changing transformer are considered, and to widen the study range of dynamic voltage phenomena using this method, extensions have been made to include induction motor and polynomial load modelling features. Besides, reactive power compensators that base their modus operandi on the switching of power electronic valves, such as HVDC-VSC and the STATCOM are taken into account. The dynamic power flow algorithm has primarily been developed making use of the positive sequence and [dq] representations. Extensions are made to developing a three-phase power flows dynamic algorithm. Test cases for the various dynamic elements developed in this research are presented to show the versatility of the models and simulation tool, including a trip cascading event leading up to a wide-area voltage collaps. Comparisons with the output of a conventional transient stability program carried out where appropriate.
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Ip, Kenneth C. W. "Dynamic modular simulation of variable water and air volume flow systems in buildings." Thesis, University of Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251526.
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PLAISANT, ANDRE LUIZ DA ROSA. "DYNAMIC SIMULATION OF HIGH VOLTAGE DIRECT CURRENT TRANSMISSION SYSTEMS IN A PERSONAL COMPUTER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8803@1.
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CENTRO DE PESQUISA DE ENERGIA ELÉTRICAEste trabalho trata do desenvolvimento e implementação de software destinado à simulação dinâmica de sistemas de transmissão 3m corrente contínua em microcomputador digital. A formulação matemática para a solução das equações diferenciais baseia-se nas vaiáveis de estado do sistema, e o método de integração numérica utilizado é o de Eüler Modificado. O modelo dinâmico de máquina síncrona é representado em suas grandezas de fase a, b, c. O programa digital conta, ainda, com telas gráficas para a visualização de resultados.
This work is concerned with the development and implementation of a sofyware for dynamic simulation fo high voltage direct current transmission systems in a personal computer. The mathematical formulation for the solution of the diferential equations is based on the system state variables and the Modified Eüler S numerical integration method is used. The dynamic model of the synchronous machines is represented through its phase variables a, b, c. the program makes use of a compactation scheme for dealing with the sparse nature of the primitive and incidence matrices. The program also provides CTR graphic interfaces to help in the analysis of simulation results.