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

Ovládání generátoru sítového provozu z prostředí OPNET Modeler / Control of network operation generator from OPNET Modeler environment

Bartl, Milan January 2011 (has links)
In this work an interface between network simulator OPNET Modeler and network operations generator IxChariot is described. The goal is to control the generator by data from an OPNET modeler simulation. More accurately the generator is supposed to produce a data flow with desired settings of DSCP field, which is used to support quality of service mechanism. The goal can be achieved by two possible approaches: using IxChariot TCL API or IxChariot C API. Both of these approaches are described and conclusions are made at the end.
22

Co-Simulation Development for Improved Cavitation Predictions in Oil-Hydraulics Systems : An investigation into the cavitating flow behavior of repetitive water hammers.

Sugathapala, Thisal Mandula, Bakker, Twan, Gudur Suresh, Rahul, Delir, Aryan January 2022 (has links)
Numerical modeling of cavitation using computational software is a highly pursued topic of research due to its impact in different industrial sectors. While some industrial applications such as wastewater treatment and mineral processing are known to advantageously use this phenomena, it remains an unwanted process in others where it is known to induce vibration, reduce performance and cause structural damage. The main objective of the current research study is to investigate the accuracy to which cavitating flow behavior inside oil-hydraulic systems can be computationally modeled, what limitations exist and how to improve numerical predictions. An experimental test-rig has been built in the preceding years with plexiglass tube to observed the vapor formations during cavitation and the pressure readings at three points have been recorded. The current study uses a computational model with the same geometry as the experimental test-rig, and uses the experimentally recorded pressure values for validating numerical results. Two main software are used to setup the simulation framework. The first is Hopsan, one open source simulation software for hydraulic systems developed by Link\"oping University and the second is ANSYS Fluent, a commercial software for modeling complex fluid flow applications. Four different orifices are used to create different outlet pressures. For orifices of diameter 2 mm, 3 mm, and 5 mm, good correlation between numerical and experimental results were observed. Further investigations into complex cavitating flow behavior of repetitive water hammers were also carried out. Different valve profile movements were used to investigate what the impact of having and not having vapor bubbles in the plexiglass tube would have on the pressure distribution when oil starts to re-circulate in the system. Furthermore, repetitive water hammer flow behavior for oscillations of 2, 3, and 4 water hammers were investigated. This investigation revealed several important findings.  The first is that if valve opens to the point that the flow starts to re-circulate in the system while vapor bubbles already exist in the plexiglass tube, massive pressure peaks, as high as 350 bar, will be created in the plexiglass pipe. The strength of this pressure surge will be dependent on the amount of vapor in the pipe when flow is re-introduced. The second is that if the valve starts to re-open (move backwards) while no vapor exists in the plexiglass tube, this movement will result in the formation of vapor. However, this vapor only lasts for a small duration and disappears before the valve reaches a point that allows flow move again. The third and final finding for repetitive water hammers was that the strength of the pressure surges will reduce with each sequential water hammer.
23

A Game Theoretic-based Transactive Energy Framework for Distributed Energy Resources

Bhatti, Bilal Ahmad 07 January 2021 (has links)
Power systems have evolved significantly during the last two decades with the advent of Distributed Energy Resources (DERs) like solar PV. Traditionally, large power plants were considered as the sole source of energy in the power systems. However, DERs connected to the transmission and the distribution systems are creating a paradigm shift from a centralized generation to a distributed one. Though the variable power output from these DERs poses challenges to the reliable operation of the grid, it also presents opportunities to design control and coordination approaches to improve system efficiency and operational reliability. Moreover, building new transmission lines to meet ever-increasing load demand is not always viable. Thus, the industry is leaning towards developing non-wires alternatives. Considering the existing limitations of the transmission system, line congestions, and logistic/economic constraints associated with its capacity expansion, leveraging DERs to supply distribution system loads is attractive and thus capturing the attention of researchers and the electric power industry. The primary objective of this dissertation is to develop a framework that enables DERs to supply local area load by co-simulating the power system and transactive system representations of the network. To realize this objective, a novel distributed optimization and game theory-based network representation is developed that optimally computes the power output of the Home Microgrids/DER aggregators. Moreover, the optimum operational schedules of the DERs within these Home Microgrids/DER aggregators are also computed. The novel electrical-transactive co-simulation ensures that the solution is optimum in the context of power systems i.e. power flow constraints are not violated while the payoffs are maximized for the Home Microgrids/DER aggregators. The transactive mechanism involves two-way iterative signaling. The signaling is modeled as an infinite strategy, multiplayer, non-cooperative game, and a novel theory is developed for the game model. The dissertation also introduces a novel concept of ranking the Home Microgrids/DER aggregators according to their historic performance, thus leading to fairness, higher participation, and transparency. Significant advantages offered by the framework include consumption of local generation, transmission upgrade deferral, mitigation of line congestions in peak periods, and reduced transmission systems losses. / Doctor of Philosophy / In past, electricity was primarily produced by the large fossil fuel-based and nuclear power plants, usually located farther away from the populated areas where the bulk of the electricity consumption occurs. The electricity from the power plants is carried by the transmission lines to the populated areas where it is distributed to end-users via a distribution network. However, during the last two decades, issues like global warming and depleting fossil fuels have led to the development and increased adoption of renewable energy resources like solar photovoltaics (PV), wind turbines, etc. These resources are commonly known as Distributed Energy Resources (DERs), and they are connected to both the transmission and the distribution systems. Initially, they were mainly used to supply the load within the facility in which they are installed. However, the electric load (demand) continues to grow while adding new fossil fuel-based plants and transmission lines are becoming logistically/economically challenging. Thus, researchers are working on developing techniques that can enable DERs to supply the loads in the distribution system to which they are connected. This dissertation develops a method to use DERs for load support in the distribution systems. Specifically, the buildings that house the DERs can use the energy generated by the DERs to supply the local load (building load), and once the total generation exceeds the load demand, the building can inject the power into the distribution system to support the local area load. The proposed framework considers the electric network constraints like limits of lines supplying the power and limits of the transformers. The proposed work also develops a new method to maximize the benefit (in terms of profit) for the DER owners. A ranking system is introduced for the DER owners that enhances the transparency and fairness of the process. The key benefits offered by the proposed work include reduced losses in the transmission system, more energy consumed closer to the point of generation, and avoidance of transmission line and large central generation additions.
24

Surrogate Analysis and Calibration of Safety-Related Driver Behavior Modeling in Microscopic Traffic Simulation and Driving Simulator for Aggressive Driving

Hong, Dawei 12 March 2024 (has links)
The increasingly urbanized world needs a solution to solve one of the most difficult problems – traffic congestion and safety. Researchers, consultants, and local officials are all attempting to solve these problems with different methods. However, it is apparent that understanding the driving behaviors on the roadway network and implementing roadway configurations accordingly is one of the great solutions. Therefore, the modeling of driving behavior would be the focus of this two-part thesis. Chapter two of this thesis will elaborate on the modeling of various driving behavior types in the microsimulation software by providing an easier-to-calibrate alternative for the driver behavior model in the microsimulation. The calibration method would leverage VISSIM, its highly customizable External driver model (EDM) API, JMP Pro's experiment design and sensitivity analysis, and SSAM's trajectory analysis. Then a set of driver model parameters are produced through sensitivity analysis, which is effective in producing a set of traffic conflicts that matches a preset target. Chapter three of this thesis focuses on simulating aggressive driving behaviors in a microsimulation and driving simulator co-simulation environment. Two co-simulation platforms are demonstrated, and the data collection are done in the VISSIM-Unity platform to collect microscopic driving data and trajectory data from the aggressive driver. Data analysis are performed on both datasets and determine the aggressive driver's safety impact. / Master of Science / The increasingly urbanized world needs a solution to solve one of the most difficult problems – traffic jams and safety. Researchers, engineers, and local officials are all attempting to solve these problems with different methods. However, it is apparent that understanding people's driving behavior on the road and designing the roads and policies to cater to these driving behaviors is one of the great solutions. Therefore, the modeling of driving behavior would be the focus of this two-part thesis. Chapter two of this thesis will experiment with a traffic simulator (which is a tool used for designing and simulating different road configurations like roundabouts and numbers of lanes) and provide an easier and more accurate way to represent various driving styles in the traffic simulator. The calibration method would leverage a driving simulator called VISSIM, an adjustable driver behavior model, a vehicle route tracker, and a vehicle route conflict analysis tool. Then a set of driving behavior parameters would be produced to match the possible traffic accident count in the traffic simulator. Chapter three of this thesis focuses on simulating aggressive driving behaviors in a traffic simulator and driving simulator (like that of those with a steering). Two driving simulator platforms are tested, and the data collection are done in one of the platforms to collect driving data and vehicle route tracker data from the aggressive driver. Data analysis are performed on both types of data and determine the aggressive driver's safety impact.
25

Multi-Physics Co-Simulation of Engine Combustion and Exhaust Aftertreatment system: Development of a Multi-Physics Co-Simulation Framework of Engine Combustion and Exhaust Aftertreatment for Model-Based System Optimisation

Themi, Vasos January 2017 (has links)
The incorporation of detailed chemistry models in internal combustion engine simulations is becoming mandatory as new combustion strategies and lower global emissions limits are setting the path towards a more efficient engine cycle simulation tool. In this report, the computational capability of the stochastic-based Kinetics SRM engine suite by CMCL Innovations is evaluated in depth. With the main objectives of this research to create a multi-physics co-simulation framework and improve the traditional engine modelling approach of individual simulation of engine system parts, the Kinetics SRM code was coupled with a GT-SUITE engine model to fill in the gap of accurate emissions predictions from one-dimensional simulation tools. The system was validated against testing points collected from the AJ133 V8 5L GDI engine running on the NEDC. The Kinetics SRM model is further advanced through a sensitivity analysis for the “unknown” internal parameters of the chemistry tool. A set of new parameters’ values has been established that gives the best overall trade-off between prediction accuracy and computational time. However, it still showed high percentage errors in modelling the emissions and it was discovered that the specific software package currently cannot simulate directed injection events. This is the first time a Kinetics SRM/GT-SUITE coupled code is employed to model a full 8-cylinder GDI SI engine. The approach showed some limitations regarding the Kinetics SRM and that in many cases is limited to trend analysis. The coupled engine – combustion emissions model is then linked with an exhaust aftertreatment system model in MATLAB Simulink, creating a multi-physics model-based co-simulation framework of engine performance, combustion characterisation, in-cylinder emissions formation and aftertreatment efficiency.
26

FEM and CFD Co-simulation Study of a Ventilated Disc Brake Heat Transfer

Tang, Jinghan, Qi, Hong Sheng January 2013 (has links)
yes / This paper presents a two-way thermally-coupled FEM-CFD co-simulation method for ventilated brake disc rotor heat transfer analysis. Using a third party coupling interface for data mapping and exchange, the FEM and CFD models run simultaneously under a standard heavy duty braking test condition. By comparison with conventional one-way coupling methods and experimental results, the performance of the co-simulation system has been investigated in terms of prediction of the heat transfer coefficient (HTC) and disc temperatures as well as computing time used. The results illustrate that this co-simulation method has good capacity in providing cooling effect and temperature predictions. It also shows that the data exchange between the FEM and CFD codes at every time increment is highly accurate and efficient throughout 10 brake applications. It can be seen that the cosimulation method is more time efficient, convenient and robust compared to previous oneway coupling methods. To utilize the potential of this method, future works are proposed.
27

SUNSHINE: Integrate TOSSIM and P-Sim

Tang, Yi 28 February 2012 (has links)
Simulators are important tools for wireless sensor network (sensornet) design and evaluation. However, existing simulators only support evaluations of protocols and software aspects of sensornet design. Thus they cannot accurately capture the significant impacts of various hardware designs on sensornet performance. To fill in the gap, we proposed SUNSHINE, a scalable hardware-software cross-domain simulator for sensornet applications. SUNSHINE is the first sensornet simulator that effectively supports joint evaluation and design of sensor hardware and software performance in a networked context. SUNSHINE captures the performance of network protocols, software and hardware through the integration of two modules: a network simulator TOSSIM [1] and hardware-software simulator P-Sim composed of an instruction-set simulator SimulAVR [2] and a hardware simulator GEZEL [3]. This thesis focuses on the integration of TOSSIM and P-Sim. It discusses the integration design considerations and explains how to address several integration challenges: time conversion, data conversion, and time synchronization. Some experiments are also given to demonstrate SUNSHINE's cross-domain simulation capability, showing SUNSHINE's strength by integrating simulators from different domains. / Master of Science
28

SUNSHINE: A Multi-Domain Sensor Network Simulator

Zhang, Jingyao 02 November 2010 (has links)
Simulators are important tools for analyzing and evaluating different design options for wireless sensor networks (sensornets) and hence, have been intensively studied in the past decades. However, existing simulators only support evaluations of protocols and software aspects of sensornet design. They cannot accurately capture the significant impacts of various hardware designs on sensornet performance. As a result, the performance/energy benefits of customized hardware designs are difficult to be evaluated in sensornet research. To fill in this technical void, in this thesis, we describe the design and implementation of SUNSHINE, a scalable hardware-software cross-domain simulator for sensornet applications. SUNSHINE is the first sensornet simulator that effectively supports joint evaluation and design of sensor hardware and software performance in a networked context. SUNSHINE captures the performance of network protocols, software and hardware up to cycle-level accuracy through its seamless integration of three existing sensornet simulators: a network simulator TOSSIM, an instruction-set simulator SimulAVR and a hardware simulator GEZEL. SUNSHINE solves challenging design problems, including data exchanges and time synchronizations across different simulation domains and simulation accuracy levels. SUNSHINE also provides hardware specification scheme for simulating flexible and customized hardware designs. Several experiments are given to illustrate SUNSHINE's cross-domain simulation capability, demonstrating that SUNSHINE is an efficient tool for software-hardware codesign in sensornet research. / Master of Science
29

Modélisation de systèmes complexes par composition : une démarche hiérarchique pour la co-simulation de composants hétérogènes / Complex System Modeling by Composition : A hierarchical approach for heterogeneous components co-simulation

Paris, Thomas 28 May 2019 (has links)
Le contexte de ce travail est la Modélisation et Simulation (M&S) de systèmes complexes. Leur étude nécessite de combiner plusieurs points de vue (échelles temporelles et spatiales, domaines scientifiques et formalismes, niveaux de résolution...). Le challenge est l'intégration rigoureuse de ces différentes perspectives sur un système au sein d'une démarche de M&S. La multi-modélisation et la co-simulation sont deux approches prometteuses pour cela. La difficulté sous-jacente est de fournir une démarche modulaire, hiérarchique, dotée d'une approche d'intégration de composants hétérogènes rigoureuse et associée à un environnement logiciel supportant l'ensemble du cycle de M&S pour la mettre en pratique. MECSYCO (Multi-agent Environment for Complex System CO-simulation) est un intergiciel de co-simulation se focalisant sur la réutilisation de modèles issus d'autres logiciels. Il se base sur une stratégie d'encapsulation logicielle et formelle fondée sur DEVS, fournit des mécanismes de gestion des hétérogénéités, et assure une co-simulation décentralisée et modulaire. MECSYCO répond au besoin d'intégration de composants hétérogènes au sein d'une co-simulation, mais ne propose pas de démarche complète comprenant l'ensemble des propriétés énoncées précédemment comme la possibilité de hiérarchiser. Pour pallier à ce manque, dans la continuité des travaux sur MECSYCO nous proposons une démarche de multi-modélisation et co-simulation descriptive autorisant la construction incrémentale de multi-modèles à partir de modèles issus d'autres logiciels. Notre démarche est décomposée en 3 étapes : l'intégration, la multi-modélisation et enfin l'expérimentation. Chaque élément produit lors de ces étapes est associé à une description permettant de le manipuler. L'utilisation de descriptions complète le processus d'intégration, permet la construction incrémentale et modulaire des multi-modèles, et isole l'expérimentation. Nous mettons ensuite en place un environnement de développement basé sur des langages dédiés aux descriptions, et nous automatisons le passage d'une description d'expérience à sa co-simulation effective. C'est une démarche d'Ingénierie Dirigée par les Modèles qui nous permet de mettre en pratique notre approche en facilitant le travail des modélisateurs et en évitant les erreurs d'implémentation. Nos contributions sont évaluées sur plusieurs expériences dont la reprise d’un multi-modèle d’autoroute hybride et un exemple de thermique des bâtiments. / This work deals with complex system Modeling and Simulation (M&S). The particularity of such systems is the numerous heterogeneous entities in interaction involved inside them. This particularity leads to several organization layers and scientific domains. As a consequence, their study requests many perspectives (different temporal and spatial scales, different domains and formalisms, different granularities...). The challenge is the rigorous integration of these various system perspectives inside an M&S process. Multi-modeling and co-simulation are promising approaches to do so. The underlying problem is to define a modular and hierarchical process fitted with a rigorous way to integrate heterogeneous components and which is supported by a software environment that covers the whole M&S cycle. MECSYCO (Multi-agent Environment for Complex SYstem CO-simulation) is a co-simulation middleware focusing on the reuse of existing models from other software. It relies on a software and formal DEVS-based wrapping, provides heterogeneity handling mechanisms and ensures a decentralized and modular co-simulation. MECSYCO deals with the heterogeneous component integration need but its M&S process does not have all the properties above-mentioned. Notably, the hierarchical modeling ability is missing. To overcome this, we propose to fit MECSYCO with a descriptive multi-modeling and co-simulation process that allows the hierarchical design of multi-models using models from other software. Our process is split into three steps: integration, multi-modeling and finally the experimentation. We adopt a descriptive approach where a description file is linked to each product of these steps, these documents enable to manipulate them. The use of description files completes the integration steps, allows a hierarchical and modular multi-model design and isolates the experiments. Then we set up a development environment based on Domain Specific Languages to support the description work, and we automate the transition from an experiment description to its effective co-simulation. This is a Model-Driven Engineering approach which allows us to put into practice our contribution by facilitating the work of modelers and by avoiding implementation mistakes. Our contributions are evaluated on several experiments including a hybrid highway model and a thermal regulation example.
30

Mehrkörpersimulation eines ebenen Koppelgetriebes mittels Matlab / ADAMS -Co-Simulation / Multibody simulation of a planar 5 Bar mechanism with Matlab/ADAMS-Co- Simulation

Gollee, Christian, Troll, Clemens 06 June 2017 (has links) (PDF)
Mit Hilfe der Matlab/ADAMS-Co-Simulation wird ein ebenes Koppelgetriebe (5- Gelenk) untersucht und anschließend die Wirkpaarung mit einem Stückgut betrachtet. Dabei werden verschiedene Modellierungsstufen angewendet und die Simulationsergebnisse Messergebnissen vom Versuchsstand gegenübergestellt. Daneben wird die grundlegende Herangehensweise beim Einsatz dieser Simulationswerkzeuge erläutert.

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