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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.
61

Experimental and computational study of a solar powered hydrogen production system for domestic cooking applications in developing economies

Topriska, Evangelia Vasiliki January 2016 (has links)
In many developing economies, a high percentage of domestic energy demand is for cooking based on fossil and biomass fuels. Their use has serious health consequences affecting almost 3 billion people. Cleaner cooking systems have been promoted in these countries such as solar cooking and smokeless stoves with varying degrees of success. In parallel, solar electrolytic hydrogen systems have been developed and increasingly used during the last 25 years for electricity, heat and automobile fueling applications. This study has developed and tested experimentally in the laboratory a solar hydrogen plant numerical model suitable for small communities, to generate and store cooking fuel. The numerical model was developed in TRNSYS and consists of PV panels supplying a PEM electrolyser of 63.6% measured stack efficiency and hydrogen storage in metal hydride cylinders for household distribution. The model includes novel components for the operation of the PEM electrolyser, its controls and the metal hydride storage, developed based on data of hydrogen generation, stack temperature and energy use from a purpose constructed small-scale experimental rig. The model was validated by a second set of experiments that confirmed the accurate prediction of hydrogen generation and storage rates under direct power supply from PV panels. Based on the validated model, large-scale case studies for communities of 20 houses were developed. The system was sized to generate enough hydrogen to provide for typical domestic cooking demand for three case-studies; Jamaica, Ghana and Indonesia. The daily cooking demands were calculated to be 2.5kWh/day for Ghana, 1.98kWh/day for Jamaica and 2kWh/day for Indonesia using data mining and a specific quantitative survey for Ghana. The suitability of weather data used in the model was evaluated through Finkelstein Schafer statistics based on composite and recent weather data and by comparing simulation results. A difference of 0.9% indicated that the composite data can be confidently used. Simulations results indicate that a direct connection system to the PV plant rather than using a battery is the optimal design option based on increased efficiency and associated costs. They also show that on average 10tonnes of CO2/year/household can be saved by replacing biomass fuel with hydrogen. The potential of total savings in the three case-study countries is shown in the form of novel solar hydrogen potential maps. The results of this study are a contribution towards better understanding the use of hydrogen systems and enhancing their role in renewable energy policy.
62

Simulace idiofonického nástroje / Simulation of Idiofonic System

Múčka, Martin January 2018 (has links)
The thesis deals with dynamic simulation of real bell behavior over time. The model is created according to principles of physical discretization as a spring in the FyDiK3D software. In order for the model to be declared as relevant, it is necessary to prove the behavior of the structures used in the elementary tasks of the mechanics. It shows the correlation between the stiffness of normal and diagonal springs. Describes how to use software import tools to create a model. The resulting model approaches its real bell behavior.
63

Propuesta de mejora del plan de gestión de mantenimiento basado en RCM y Lean Office en el proceso de inyección de polímeros / Proposal to improve the maintenance management plan based on RCM and Lean Office in the polymer injection process

Rodriguez Caceres, Adrian Rigoberto, Valenzuela Fuchs , Marysabel 19 November 2020 (has links)
La propuesta es el diseño de una propuesta para mejorar la implementación del plan de gestión de mantenimiento en el proceso de moldeo por inyección de polímeros basado en la filosofía de las metodologías Lean Office y RCM. La aplicación se lleva a cabo en una empresa peruana de inyección de plástico donde se identificó el uso inadecuado del plan de Gestión de Mantenimiento, causado por la baja disponibilidad de repuestos y personal, el porcentaje de materia prima reprocesada y el deterioro de las Máquinas de moldeo. La importancia de resolver este problema es reducir la baja confiabilidad del equipo, la demora en la entrega de pedidos y la pérdida de producción. Los resultados esperados validado por la simulación de sistemas mostraron que la disponibilidad del personal aumentó a 83.07% y las paradas no planificadas de la máquina de inyección se redujeron en un 30%. / This professional project for the title of Industrial Engineer, design of a proposal to improve the implementation of the maintenance management plan in the polymer injection molding process based on the philosophy of the Lean Office and RCM methodologies. The application is carried out in a Peruvian plastic injection company where the damaged use of the Maintenance Management plan, the risk due to the low availability of spare parts and personnel, the percentage of raw material reprocessed and the treatment of the Machines were identified Molding The importance of solving this problem is to reduce the low reliability of the equipment, the delay in the delivery of orders and the loss of production. The expected results validated by the simulation of controlled systems that the availability of the personnel had an 83.07% and the unplanned stops of the injection machine were reduced by 30%. / Trabajo de investigación
64

Software de simulación edición y análisis de afluencia de personas, en edificaciones de alto tránsito, para mejorar la calidad de aprendizaje de los estudiantes de arquitectura / Simulation, edition and analysis software of people in high traffic buildings to improve the quality of learning of architecture students

Bueno Carrasco, Ricardo Andre, Mori Yzaguirre, Daniel Enrique 17 November 2021 (has links)
En la actualidad, los entornos virtuales son una tecnología en constante evolución. Dicha evolución se relacionada en diferentes áreas de estudio, explayándose desde el área medica hasta el área de la arquitectura, siendo esta última, conformada por usualmente sistemas de simulación respecto a evacuaciones, flujos o mediciones de entornos.  No obstante, los sistemas existentes presentan cierto grado de complejidad en la interacción con el usuario, puesto que, la mayoría de estos cuenta con una interfaz de programación, en donde el usuario es el encargado de programar tanto los entornos, como el comportamiento del flujo de agentes simulados. Generando un nivel de complejidad en estos, pues desvía el conocimiento nato de los estudiantes de arquitectura, al nivel de aprender diferentes lenguajes de programación con el fin de poder simular sus entornos y el comportamiento de personas en estos.     Por otro lado, estos sistemas, a su vez, se centran en movimientos ya establecidos, en donde el usuario no aprecia o no tiene idea de cómo el recorrido realizado por el agente es el óptimo respecto otros existentes. Siendo este definido por el sistema y no por el usuario.   En consecuencia, como resultado de investigación, se propone un software de simulación, edición y análisis de afluencia de personas en edificaciones de alto tránsito para mejorar la calidad de aprendizaje de los estudiantes de arquitectura. Desarrollando el presente trabajo, en etapas. En donde, la primera etapa, consiste en definir el alcance del proyecto, necesidades y objetivos, así como oportunidades de negocio. En la segunda etapa, se listarán los framework necesarios, de la cuales se explicarán sus ventajas y desventajas correspondientes a las demandas de nuestra simulación. Y, en tercer lugar, tras haber seleccionado alguno, se procederá con la propuesta de investigación, así como su comparativo técnico con otras soluciones.  Finalmente, se tratará como problemática: “La necesidad de una herramienta de simulación de fácil uso, bajo costo, mantenimiento y libre de lenguajes de programación; respecto la afluencia de personas.” / Today the simulation of real environments is a process of constant evolution. This extends from research fields in medicine to architecture being in the latter a simulation system regarding evacuations flows or measurements of environments. However, the existing systems have given much to talk about in this context since most of them have a programming interface where the user oversees programming both the environments and the flow behavior of simulated agents. Generating a level of complexity in these as it diverts the natural knowledge of architecture students at the level of learning different programming languages ​​to be able to simulate their environments and the behavior of people in them. On the other hand, these systems in turn focus on already established movements where the user does not appreciate or has no idea of ​​how the route made by the agent is optimal compared to other existing ones. Being this defined by the system and not by the user. Consequently, because of research a software for the simulation editing and analysis of the influx of people in high-traffic buildings is proposed to improve the quality of learning of architecture students. Developing this work in stages. Where the first stage consists of defining the scope of the project needs and objectives as well as business opportunities. In the second stage the necessary frameworks will be listed of which their advantages and disadvantages corresponding to the demands of our simulation will be explained and thirdly after having selected one we will proceed with the research proposal as well as its technical comparison with other solutions. Finally, the following will be treated as problematic: “The need for a simulation tool that is easy to use low in cost, maintenance and free of programming languages regarding the influx of people. / Tesis
65

Modeling of a Retrodirective Channel With Active Antenna Arrays for Cross-Eye Jamming

Petersson, Björn January 2017 (has links)
Cross-Eye (CE) jamming is a technique aimed at inducing false target angles in radar measurements. The potential to deceive monopulse radar, a radar type commonly used due to its angular accuracy and resilience against jamming, has captured the interest of Electronic Warfare (EW) system manufacturers. CE jamming may increase the capability of self-defense against radar guided missiles. In this thesis, a CE jammer, based on the retrodirective channel design, for use in an EW systems is modeled and analyzed. The focus of the analysis is on the non-reciprocal Active Electronically Scanned Arrays (AESA). An electrical model of the jammer system and the AESA, including variations in the electrical properties, together with three different system correction methods are used. A simulation procedure, using single frequency (CW) signals, is defined and used for estimating total level of reciprocity, which is a primary contributor to jammer performance. Reciprocity error sensitivity for variations in model parameters is simulated to indicate which AESA aspects are essential for performance. Further, the influence of characterization and calibration noise is investigated. The usability of the model is demonstrated in different types of simulations, which highlights the differences between the system correction methods. Simulations show that a relatively high level of reciprocity can be achieved when using system correction, if measurement noise and model limitations are disregarded. The expected degradation in reciprocity from differences in electrical properties between the reception and transmission branch of the AESA has been confirmed. The effect of characterization and calibration noise, for realistic levels of noise, seems to be a dominating factor in the total reciprocity error. A significant increase in reciprocity error can likely be expected when non-CW signals are used and when realistic levels of noise and non-linear effects are added. / Cross-eye (CE) är en störprincip som har potential att inducera vinkelmätfel i radar. Dess möjlighet att störa monopulsradar, en vanligt förekommande typ av radar som är motståndskraftig mot många störformer, har skapat ett intresse för metoden hos tillverkare av system för elektronisk krigföring (EW-system). Användning av CE störning i ett EW-system skulle kunna öka möjligheten till självskydd vid attack från en monopulsradarstyrd robot. Avhandlingen analyserar en modell av en retrodirektiv CE störare som är avsedd för integration i ett multifunktionellt EW-system. Fokus i analysen är på de aktiva gruppantennerna (AESA) som används i systemet. En elektrisk modell av systemet används, vilken inkluderar variationer i parametrar hos AESA samt tre olika systemkorrektionsmetoder. En simuleringsprocedur som ger möjlighet att uppskatta reciprocitetsfel och känslighet för parametervariationer i AESA är definierad. Vidare undersöks inverkan av karaktäriserings och kalibreringsbrus. Modellens användningsområden visas i olika typer av prestandasimulering där effekter av de olika systemkorrektionsmetoderna tydliggörs. Simuleringsresultat för enkelfrekvens (CW) signaler visar en relativt hög nivå av reciprocitet om brus och olinjäriteter ignoreras. Det förväntade resultatet, att elektriska skillnader mellan mottagar- och sändargrenarna orsakar en försämring i reciprocitet, bekräftas. Inverkan av karaktäriserings och kalibreringsbrus verkar vara en dominerande faktor i det totala reciprocitetsfelet då rimliga brusnivåer används. En signifikant höjning av reciprocitetsfelet kan sannolikt förväntas då signaler med en viss bandbredd används och då rimliga nivåer av brus samt olinjäriteter inkluderas. / <p>QC 20171102</p>
66

Hybrid Parallel Computing Strategies for Scientific Computing Applications

Lee, Joo Hong 10 October 2012 (has links)
Multi-core, multi-processor, and Graphics Processing Unit (GPU) computer architectures pose significant challenges with respect to the efficient exploitation of parallelism for large-scale, scientific computing simulations. For example, a simulation of the human tonsil at the cellular level involves the computation of the motion and interaction of millions of cells over extended periods of time. Also, the simulation of Radiative Heat Transfer (RHT) effects by the Photon Monte Carlo (PMC) method is an extremely computationally demanding problem. The PMC method is example of the Monte Carlo simulation method—an approach extensively used in wide of application areas. Although the basic algorithmic framework of these Monte Carlo methods is simple, they can be extremely computationally intensive. Therefore, an efficient parallel realization of these simulations depends on a careful analysis of the nature these problems and the development of an appropriate software framework. The overarching goal of this dissertation is develop and understand what the appropriate parallel programming model should be to exploit these disparate architectures, both from the metric of efficiency, as well as from a software engineering perspective. In this dissertation we examine these issues through a performance study of PathSim2, a software framework for the simulation of large-scale biological systems, using two different parallel architectures’ distributed and shared memory. First, a message-passing implementation of a multiple germinal center simulation by PathSim2 is developed and analyzed for distributed memory architectures. Second, a germinal center simulation is implemented on shared memory architecture with two parallelization strategies based on Pthreads and OpenMP. Finally, we present work targeting a complete hybrid, parallel computing architecture. With this work we develop and analyze a software framework for generic Monte Carlo simulations implemented on multiple, distributed memory nodes consisting of a multi-core architecture with attached GPUs. This simulation framework is divided into two asynchronous parts: (a) a threaded, GPU-accelerated pseudo-random number generator (or producer), and (b) a multi-threaded Monte Carlo application (or consumer). The advantage of this approach is that this software framework can be directly used within any Monte Carlo application code, without requiring application-specific programming of the GPU. We examine this approach through a performance study of the simulation of RHT effects by the PMC method on a hybrid computing architecture. We present a theoretical analysis of our proposed approach, discuss methods to optimize performance based on this analysis, and compare this analysis to experimental results obtained from simulations run on two different hybrid, parallel computing architectures. / Ph. D.
67

Einsatz der Mehrkörper-Simulation zur Entwicklung eines Antriebmoduls für mobile Roboter

Gerlach, Erik, Ettel, Matti, Zentner, Lena 20 June 2024 (has links)
Im Beitrag wird die Nutzung des Mehrkörper-Simulationsprogrammes alaska zur Entwicklung eines Fahrmoduls für mobile Roboter vorgestellt. Das Ziel bei der Entwicklung des Moduls war, mobile Roboter mit höheren Fahrgeschwindigkeiten zu realisieren als vergleichbare Systeme mit omnidirektionalen Rädern. Die Nutzung von Simulationsrechnungen stellte vom ersten Entwurf einen elementaren Bestandteil der Gesamtentwicklung dar. So flossen immer wieder Erkenntnisse aus den Simulationen in die Weiterentwicklung ein. Die Mehrkörpersysteme (MKS) wurden im Programm alaska aufgebaut. Am Beginn des Entwicklungsprozesses bestanden die Simulationsmodelle aus wenigen Elementen, um das grundsätzliche Bewegungsverhalten zu analysieren. Darauf aufbauend wurden komplexere Simulationsmodelle genutzt, die sich zur Bestimmung des Einflusses von Parametern auf das Bewegungsverhalten eignen. / This article presents the use of a multi-body simulation program to develop a driving module for mobile robots. The aim in developing the module was to realize mobile robots with higher driving speeds than comparable systems with omnidirectional wheels. The use of simulation calculations was an elementary component of the overall development from the very first draft. As a result, findings from the simulations were repeatedly incorporated into further development. The multi-body systems (MBS) were set up in the simulation program alaska. At the beginning of the development process, the simulation models consisted of a few elements in order to analyze the basic movement behavior. Building on this, more complex simulation models were used, which are suitable for determining the influence of parameters on the movement behavior.
68

Stochastic Approach To Fusion Dynamics

Yilmaz, Bulent 01 June 2007 (has links) (PDF)
This doctoral study consists of two parts. In the first part, the quantum statistical effects on the formation process of the heavy ion fusion reactions have been investigated by using the c-number quantum Langevin equation approach. It has been shown that the quantum effects enhance the over-passing probability at low temperatures. In the second part, we have developed a simulation technique for the quantum noises which can be approximated by two-term exponential colored noise.
69

Plateforme de conception d'actionneurs : méthodes et outils pour le pré-dimensionnement d'actionneurs / Framework to actuators design : methods and tools to pre-sizing actuators

Martins, Douglas Araujo 07 April 2015 (has links)
Les contacteurs et les relais sont utilisés dans de très nombreux dispositifs pour le contrôleet la commande à distance. La plupart sont équipés d’actionneurs électromagnétiques qu’il est nécessairede produire en quantité importante pour réaliser ces fonctions. Les exigences environnementalessur l’efficacité et la consommation énergétiques sont de plus en plus contraignantes. La conception deces actionneurs est donc un enjeu important. Cette thèse porte sur le développement d’une plateforme deconception dédiée au pré-dimensionnement d’actionneurs électromagnétiques. Cette plateforme reposesur le développement de méthodes de modélisation très rapides et suffisamment précises. La premièrepartie est consacrée à la résolution des équations de la magnétostatique en linéaire et non-linéaire par lecouplage de la méthode des intégrales de frontières avec la méthode de réseaux de réluctances. L’évaluationdes grandeurs globales telles que le flux magnétique traversant une bobine et la force est étudiée.Les résultats sont validés sur un relais bistable en rotation. La seconde partie concerne la simulationmulti-physique du composant dans son environnement système, pour prendre en compte les aspects mécaniqueet électrique. Une étude de faisabilité par optimisation est réalisée pour le composant seul, puispour l’ensemble composant-système. Enfin, une ouverture sur une autre méthode de modélisation plusgénérale est proposée avec la présentation d’un couplage original et performant entre les méthodes deséléments finis et des intégrales de frontière. / Contactors and relays are used in many devices for monitoring and remote controlling. Mostof them are equipped with electromagnetic actuators, which are produced in large quantities. The environmentalrequirements on efficiency and energy consumption have become more and more strict. Thedesign of these actuators is therefore an important issue. This thesis focuses on the development of adesign platform dedicated to the pre-sizing of electromagnetic actuators. This platform is based on theimplementation of very fast and sufficiently accurate modeling methods. The first part is devoted to theresolution of linear and nonlinear magnetostatic equations by the coupling between boundary integralmethod and reluctance network method. The evaluation of global quantities such as the magnetic fluxflowing through a coil and the force is investigated. The results are validated on a rotating bistable relay.The second part concerns the multi-physics simulation of the component in its environment by takinginto account the mechanical and electrical aspects. A feasibility study by optimization is performed bothfor the component alone and for the whole component-system. Finally, a general modeling method isproposed with the presentation of an original and efficient coupling between the finite element methodsand boundary integrals.
70

Um método de análise de cenários para sequenciamento da produção usando lógica nebulosa. / A Fuzzy classifier model for the production sequencing.

Silva, Allan Rodrigues da 31 May 2005 (has links)
Made available in DSpace on 2016-06-02T19:06:27Z (GMT). No. of bitstreams: 1 DissARS.pdf: 1479466 bytes, checksum: b0e4db694de6cc642354b502d3f9187f (MD5) Previous issue date: 2005-05-31 / Universidade Federal de Sao Carlos / Production planning in automated manufacturing environments is a complex task which comprehends, among other activities, the production sequencing. One of the techniques used to determine the best production sequencing is the simulation. All possible sequences can be simulated and, right after that, the sequences with the best performance are verified, according to some criteria. However, due to the combinatory nature of the sequencing, the simulation of all possible combinations takes long time, becoming quite impracticable in many cases. Besides, events that were not programmed occur frequently in automated manufacturing environments and the decision maker must be fast choosing alternatives. Aiming to contour this problem, this work proposes a fuzzy analyser of sceneries for the production sequencing (ANCSP). The goal is to reduce the quantity of sequences to be simulated by the decision maker when non programmed events occur in the productive system, according to a defined performance criteria. The maximum quantity of generated sequences is calculated based on the time avaliable to realize the simulation. The proposed model intends to support the usage of the simulation technique by the decision makers. The ANCSP was implemented and various tests were performed. A specific model of flexible manufacturing system was considered to perform the tests. The performance of the ANCSP was analyzed comparing its results with those presented by a simulation software, for the same test sets and in accordance to the performance measures established. / O planejamento da produção em ambientes automatizados de manufatura é uma tarefa complexa que compreende, dentre outras atividades, o sequenciamento da produção. Uma das técnicas usadas para determinar qual a melhor sequência de produção é a simulação. Todas as sequências possíveis são simuladas e, logo após, verifica-se qual a sequência que obteve o melhor desempenho, de acordo com algum critério. Entretanto, devido à natureza combinatória do sequenciamento, a simulação de todas as sequências possíveis consome muito tempo, tornando-se inviável em muitos casos. Além disso, eventos não programados ocorrem com frequência nos ambientes automatizados de manufatura e o tomador de decisão precisa ter escolhas rápidas. Visando contornar esses problemas, esse trabalho propõe um analisador nebuloso de cen´arios para o sequenciamento da produção (ANCSP). O objetivo é reduzir a quantidade de sequências a serem simuladas pelo tomador de decis ao no momento da ocorrência de eventos não programados no sistema produtivo, de acordo com alguma medida de desempenho. A quantidade máxima de sequências geradas é calculada com base no tempo que o tomador de decisão possui para realizar a simulação. Dessa maneira, o modelo proposto pretende apoiar o uso da técnica de simulação pelos tomadores de decisão. O ANCSP foi implementado e diversos testes foram realizados. Para a realização dos testes, considerou-se um modelo específico de sistema flexível de manufatura. O desempenho do ANCSP foi analisado mediante comparação dos seus resultados com aqueles apresentados por um software de simulação, para o mesmo conjunto de testes e de acordo com as medidas de desempenho estabelecidas.

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