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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.
331

Engenharia de sistemas baseada em modelos: modelagem orientada a objetos de sistemas logísticos de armazenamento e recuperação. / Model based systems engineering (MBSE): object oriented modeling of warehouse storage solutions.

Glogowsky, Pedro Spada 10 November 2017 (has links)
Este trabalho desenvolve um método para a comparação de soluções logísticas de armazenamento e recuperação, com aplicações em centros de distribuição, depósitos, armazéns e demais estruturas equivalentes. Tais soluções podem implicar desde o uso de paleteiras manuais e empilhadeiras contra-balanceadas, até em arranjos mais complexos, envolvendo trans-elevadores operando em corredores de prateleiras com vários metros de altura. A literatura existente para o design e a escolha de tais soluções ressalta o prevalecimento de métodos proprietários e ad-hoc, auxiliados por ferramentas de software demasiadamente genéricas. Assim, o método aqui proposto é elaborado seguindo os princípios da Engenharia de Sistemas Baseada em Modelos (MBSE), sendo expresso através da linguagem OMG SysMLTM, e montado com o auxílio de ferramenta de software CASE (computer aided systems engineering) disponível comercialmente. Utilizando-se das técnicas mencionadas, este trabalho demonstra o passo-apasso da construção do método proposto, incluindo a formulação de um template de requisitos e de um modelo de referência, orientado a objetos, para sistemas logísticos de armazenamento e recuperação. Concluída a apresentação do método, o mesmo é aplicado em dois exemplos de estudos de viabilidade (trade-studies) que determinam soluções ótimas para um dado conjunto de requisitos de negócio. No primeiro exemplo tem-se como fator limitante o no de endereços de armazenamento, e no segundo a área disponível para construção do armazém. O principal resultado obtido com esse trabalho é capacidade de simular, em um único ambiente, escolhas de soluções logísticas de armazenamento que consideram parâmetros do sistema como um todo, e não apenas de seus sub-sistemas isoladamente. Isto tornou possível mensurar como alterações nas especificações de um dado ponto de vista, como o estrutural, impactam na satisfação dos requisitos de outros pontos de vista, como o dinâmico ou financeiro. A MBSE, entretanto, ainda não pode ser considerada uma disciplina madura. As ferramentas de software que a ela dão suporte, bem como as listas de melhores práticas de suas aplicações estão em constante evolução e aprimoramento. Dessa forma, a aplicação dos princípios da MBSE no design e seleção de soluções logísticas de armazenamento, com adoção da orientação a objetos, pode ser tida como uma ideia inovadora. / This work presents a method for warehouse storage solutions comparison. The existing research regarding the design and selection of such logistic solutions highlights the predominance of ad-hoc procedures, as well as the use of generic software tools. Therefore, the method herein presented shall be developed according to the model-based systems engineering (MBSE) principles, being describe through the system modeling language (SysML), and built inside a computer-aided system engineering (CASE) software tool, commercially available. The method\'s steps shall be thoroughly detailed, including the creation of a reference model for warehouse storage systems, and its further use in trade studies execution. Once the method is properly described, its validation is demonstrated through two case studies designed to compare storage solutions according to the number of pallet-positions oered, and its dimensional footprint. This work\'s main achievement is the possibility to simulate, in a single environment, warehouse storage solution\'s options that take into account parameters of the system as a whole, and not only its sub-systems separately. With that, it is possible to measure how changes in the specifications of a given view point, such as structural, impact the requirement\'s satisfaction of other view points, such as dynamic or financial. The MBSE, however, still can not be considered a mature discipline. The software tools that support it, as well as the lists of best practices of its applications are constantly evolving and improving. Thus, the application of MBSE\'s principles in the design, and comparison, of warehouse storage solutions, with the adoption of object orientation, can be considered an innovative idea.
332

A simulation-driven model-based approach for designing software-intensive systems-of-systems architectures / Uma abordagem digirida por simulação e baseada em modelos para projeto de arquiteturas de sistemas de sistemas intensivos em software

Graciano Neto, Valdemar Vicente 27 March 2018 (has links)
Context: Software-intensive systems have been increasingly interoperated forming alliances termed as Systems-of-Systems (SoS). SoS comprises a collection of systems joined to achieve a set of missions that none of the systems can accomplish on its own. Each constituent system keeps its own management, goals, and resources while coordinating within the SoS and adapting to meet SoS goals. Applications of SoS range from traffic control to emergency response and crisis management. As SoS often support critical domains, such systems must be correct by dealing with malfunction or defects and avoiding failures that could cause extensive damage and losses to the users. Problem: Correct SoS operations depend on a precise specification and a rigorous attestation of its operational consistency. However, besides limitations on languages to jointly capture SoS structure and behavior, predictions on the SoS operational consistency rely on constituent systems not totally known at design-time. Therefore, SoS have been developed and deployed without evaluating their operations, since current languages do not support such precision in evaluation. Objectives: This thesis provides solutions founded on a formal architectural description language to support an early evaluation of SoS operation regarding SoS structure and behavior by means of simulations. Contribution: The main contributions of this project comprise (i) a model transformation approach for automatically producing simulation models from SoS software architecture descriptions, combining SoS structure and behavior description in a same solution, (ii) a SoS software architecture evaluation method for SoS operation prediction considering the inherent changes that can occur, (iii) environment modelling and automatic generation of stimuli generators to sustain the SoS simulation, delivering data to feed such simulation, and (iv) a method for the automatic synchronization between the runtime descriptive architecture (changed at runtime due to dynamic architecture) and its original prescriptive architecture based on model discovery and recovery mechanisms and a backward model transformation. Evaluation: We conducted case studies to assess our solutions using Flood Monitoring SoS and Space SoS. Results: Our solutions support a high accuracy to (i) produce fault-free and fully operational simulations for SoS software architectures, (ii) support evaluation and prediction of SoS operation at design-time, (iii) automatically generate stimuli generators to sustain and feed the simulation execution, and (iv) maintain the synchronization between the runtime architecture and the intended version of the SoS architecture. Conclusions: We concluded that the proposed solutions advance the state of the art in SoS software architecture evaluation by offering solutions to predict the SoS operations effectiveness to maintain a continuous operation despite architectural changes, providing more trust for users that futurely shall rely on SoS services. / Contexto: Sistemas intensivos em software tem sido interoperados para formar alianças conhecidas como Sistemas-de-Sistemas (SoS). Domínios de aplicação de SoS variam do controle de tráfego ao gerenciamento de situações de crises e emergência. Devido à criticidade destes domínios, tais sistemas precisam ser confiáveis e robustos, lidando com potenciais defeitos e mal funcionamento, e evitando falhas que poderiam causar ameaças à integridade dos usuários. Problema: O funcionamento correto de um SoS depende da especificação precisa e da garantia rigorosa da consistência de suas operações. Entretanto, além das limitações nas linguagens quanto à especificação de ambos estrutura e comportamento do SoS, prever seu comportamento depende da especificação de constituintes que não são totalmente conhecidos em tempo de projeto e de seu comportamento emergente. Neste sentido, SoS têm sido desenvolvidos e implantados sem a devida avaliação de seus comportamentos, uma vez que as linguagens disponíveis atualmente não dão suporte a uma especificação precisa destes comportamentos. Objetivos: Este projeto de doutorado relata avanços teóricos e práticos fundamentados em uma linguagem de descrição arquitetural formal para permitir a predição e avaliação do comportamento e estrutura dos SoS com base em simulações. Contribuições: As principais contribuições deste projeto envolvem (i) uma transformação de modelos para produzir automaticamente modelos de simulação para descrições de arquitetura de software de SoS, combinando estrutura e comportamento em uma mesma solução, (ii) um método de avaliação de arquitetura de software de SoS para prever o comportamento do SoS considerando sua dinâmica inerente, (iii) modelagem do ambiente e derivação automática de geradores de estímulos entregando dados continuamente e sustentando a execução de simulações de SoS, e (iv) um método para promover a sincronização automática entre modelos descritivos e prescritivos de arquitetura de software de SoS baseados em mecanismos de descoberta e recuperação de modelos, e transformação de modelos reversa. Avaliação: Estudos de caso foram conduzidos para avaliar as soluções nos domínios de Monitoramento de Enchentes e Espacial. Resultados: As abordagens propostas exibem alta acurácia no que tange (i) a produzir simulações operacionais e sem falhas para arquiteturas de software de SoS, (ii) ao suporte á avaliação, ainda em tempo de projeto, do comportamento que emerge da operação do SoS, (iii) à derivação automática de geradores de estímulos para entrega contínua de dados e manutenção da execução das simulações geradas, e (iv) à manutenção do alinhamento entre os modelos descritivos e prescritivos da arquitetura do SoS avaliado. Conclusões: Conclui-se que as abordagens propostas avançam o estado da arte no projeto de arquiteturas de Software de SoS ao permitir prever, em tempo de projeto, como o SoS vai operar em tempo de execução, permitindo estabelecer estratégias para manter a simulação rodando, e sua operação contínua, mesmo com as mudanças arquiteturais inerentes ao seu funcionamento, provendo mais confiabilidade para os usuários futuramente dependerão de seus serviços.
333

Design Simplification by Analogical Reasoning

Balazs, Marton E. 09 February 2000 (has links)
Ever since artifacts have been produced, improving them has been a common human activity. Improving an artifact refers to modifying it such that it will be either easier to produce, or easier to use, or easier to fix, or easier to maintain, and so on. In all of these cases, "easier" means fewer resources are required for those processes. While 'resources' is a general measure, which can ultimately be expressed by some measure of cost (such as time or money), we believe that at the core of many improvements is the notion of reduction of complexity, or in other words, simplification. This talk presents our research on performing design simplification using analogical reasoning. We first define the simplification problem as the problem of reducing the complexity of an artefact from a given point of view. We propose that a point of view from which the complexity of an artefact can be measured consists of a context, an aspect and a measure. Next, we describe an approach to solving simplification problems by goal-directed analogical reasoning, as our implementation of this approach. Finally, we present some experimental results obtained with the system. The research presented in this dissertation is significant as it focuses on the intersection of a number of important, active research areas - analogical reasoning, functional representation, functional reasoning, simplification, and the general area of AI in Design.
334

3D Reconstruction of the Magnetic Vector Potential of Magnetic Nanoparticles Using Model Based Vector Field Electron Tomography

KC, Prabhat 01 June 2017 (has links)
Lorentz TEM observations of magnetic nanoparticles contain information on the magnetic and electrostatic potentials of the sample. These potentials can be extracted from the electron wave phase shift by separating electrostatic and magnetic phase shifts, followed by 3D tomographic reconstructions. In past, Vector Field Electron Tomography (VFET) was utilized to perform the reconstruction. However, VFET is based on a conventional tomography method called filtered back-projection (FBP). Consequently, the VFET approach tends to produce inconsistencies that are prominent along the edges of the sample. We propose a model-based iterative reconstruction (MBIR) approach to improve the reconstruction of magnetic vector potential, A(r). In the case of scalar tomography, the MBIR method is known to yield better reconstructions than the conventional FBP approach, due to the fact that MBIR can incorporate prior knowledge about the system to be reconstructed. For the same reason, we seek to use the MBIR approach to optimize vector field tomographic reconstructions via incorporation of prior knowledge. We combine a forward model for image formation in TEM experiments with a prior model to formulate the tomographic problem as a maximum a posteriori probability estimation problem (MAP). The MAP cost function is minimized iteratively to deduce the vector potential. A detailed study of reconstructions from simulated as well as experimental data sets is provided to establish the superiority of the MBIR approach over the VFET approach.
335

Engenharia de sistemas baseada em modelos: modelagem orientada a objetos de sistemas logísticos de armazenamento e recuperação. / Model based systems engineering (MBSE): object oriented modeling of warehouse storage solutions.

Pedro Spada Glogowsky 10 November 2017 (has links)
Este trabalho desenvolve um método para a comparação de soluções logísticas de armazenamento e recuperação, com aplicações em centros de distribuição, depósitos, armazéns e demais estruturas equivalentes. Tais soluções podem implicar desde o uso de paleteiras manuais e empilhadeiras contra-balanceadas, até em arranjos mais complexos, envolvendo trans-elevadores operando em corredores de prateleiras com vários metros de altura. A literatura existente para o design e a escolha de tais soluções ressalta o prevalecimento de métodos proprietários e ad-hoc, auxiliados por ferramentas de software demasiadamente genéricas. Assim, o método aqui proposto é elaborado seguindo os princípios da Engenharia de Sistemas Baseada em Modelos (MBSE), sendo expresso através da linguagem OMG SysMLTM, e montado com o auxílio de ferramenta de software CASE (computer aided systems engineering) disponível comercialmente. Utilizando-se das técnicas mencionadas, este trabalho demonstra o passo-apasso da construção do método proposto, incluindo a formulação de um template de requisitos e de um modelo de referência, orientado a objetos, para sistemas logísticos de armazenamento e recuperação. Concluída a apresentação do método, o mesmo é aplicado em dois exemplos de estudos de viabilidade (trade-studies) que determinam soluções ótimas para um dado conjunto de requisitos de negócio. No primeiro exemplo tem-se como fator limitante o no de endereços de armazenamento, e no segundo a área disponível para construção do armazém. O principal resultado obtido com esse trabalho é capacidade de simular, em um único ambiente, escolhas de soluções logísticas de armazenamento que consideram parâmetros do sistema como um todo, e não apenas de seus sub-sistemas isoladamente. Isto tornou possível mensurar como alterações nas especificações de um dado ponto de vista, como o estrutural, impactam na satisfação dos requisitos de outros pontos de vista, como o dinâmico ou financeiro. A MBSE, entretanto, ainda não pode ser considerada uma disciplina madura. As ferramentas de software que a ela dão suporte, bem como as listas de melhores práticas de suas aplicações estão em constante evolução e aprimoramento. Dessa forma, a aplicação dos princípios da MBSE no design e seleção de soluções logísticas de armazenamento, com adoção da orientação a objetos, pode ser tida como uma ideia inovadora. / This work presents a method for warehouse storage solutions comparison. The existing research regarding the design and selection of such logistic solutions highlights the predominance of ad-hoc procedures, as well as the use of generic software tools. Therefore, the method herein presented shall be developed according to the model-based systems engineering (MBSE) principles, being describe through the system modeling language (SysML), and built inside a computer-aided system engineering (CASE) software tool, commercially available. The method\'s steps shall be thoroughly detailed, including the creation of a reference model for warehouse storage systems, and its further use in trade studies execution. Once the method is properly described, its validation is demonstrated through two case studies designed to compare storage solutions according to the number of pallet-positions oered, and its dimensional footprint. This work\'s main achievement is the possibility to simulate, in a single environment, warehouse storage solution\'s options that take into account parameters of the system as a whole, and not only its sub-systems separately. With that, it is possible to measure how changes in the specifications of a given view point, such as structural, impact the requirement\'s satisfaction of other view points, such as dynamic or financial. The MBSE, however, still can not be considered a mature discipline. The software tools that support it, as well as the lists of best practices of its applications are constantly evolving and improving. Thus, the application of MBSE\'s principles in the design, and comparison, of warehouse storage solutions, with the adoption of object orientation, can be considered an innovative idea.
336

Geração automática e assistida de interfaces de usuário / Automatic and aided generation of user interfaces

Mrack, Marcelo January 2009 (has links)
A geração automatizada de Interfaces de Usuário (IU) é objeto de estudo há muitos anos. Desde a década de 80, dezenas de projetos foram desenvolvidos e várias soluções apresentadas ao mercado. Entretanto, mesmo com os avanços obtidos neste cenário, inúmeras dificuldades ainda continuam presentes no dia-a-dia dos desenvolvedores de sistemas. A necessidade de processos, sintaxes e linguagens proprietárias associado ao elevado esforço de configuração e à baixa reutilização de tecnologias são os principais problemas nessa área. Objetivando sanar essas dificuldades, este trabalho propõe uma solução diferenciada para o problema, a qual reutiliza e integra-se à maioria das tecnologias comumente presentes nos ambientes de desenvolvimento e que conta com um exclusivo sistema de configuração, capaz de minimizar o trabalho de geração das IU. Sendo um típico gerador baseado em modelos, o software proposto é chamado MERLIN, e objetiva automatizar completamente a geracão de interfaces CRUD, as quais estão presentes em até 30% dos sistemas que operam sobre banco de dados. Para alcançar este objetivo, o software aposta no uso intensivo de heurísticas e na formação de uma estrutura auto-contida e realimentada de configurações, a qual reside unicamente nas classes compiladas da aplicação. Completando a sua arquitetura, um processo de geração em tempo de execução inibe a produção de qualquer linha de código-fonte, o que evita a necessidade de refatoração ao longo da evolução dos sistemas. Com esses elementos em evidência e focando inicialmente a plataforma Java, sinaliza-se uma solução diferenciada, apta para ser utilizada em ambientes profissionais de desenvolvimento. / The automated generation of User Interfaces (UI) has been the object of study for many years. Since the 1980s, dozens of projects have been developed and various solutions presented to the market. However, even with the advances obtained under this scenario, innumerable difficulties still continue to present themselves in the daily routine of system developers. The demands of proprietary methodologies, syntaxes and languages, the high level of effort needed for configuration and low reuse of technologies are the main problems in the area. With the object of rectifying these difficulties, this work proposes a solution specific to the problem, which reuses and combines the majority of the technologies already existing in development environments and relies on an exclusive configuration system, capable to minimize the work of generating the UI. Being a typical model based generator, the software under consideration is called MERLIN, and has as its objective to completely automate the generation of CRUD interfaces, which are present in up to 30% of the systems that interact with data bases. To achieve this objective, the software relies on the intensive use of heuristics and the creation of a self contained configuration feedback structure, which exists solely in the compiled classes of the application. Completing this architecture, a process of execution time generation eliminates the need for any source code, which significantly reduces the costs of refactoring the code throughout the evolution of the systems. With these elements in evidence and focusing initially on the Java platform, indicates that this distinguished solution is ready for use in professional development environments.
337

Depuração automática de programas baseada em modelos: uma abordagem hierárquica para auxílio ao aprendizado de programação / Automated model based software debugging: a hierarchical approach to help programming learning

Pinheiro, Wellington Ricardo 07 May 2010 (has links)
Diagnóstico baseado em modelos (Model Based Diagnosis - MBD) é uma técnica de Inteligência Artificial usada para encontrar componentes falhos em dispositivos físicos. MBD também tem sido utilizado para auxiliar programadores experientes a encontrarem falhas em seus programas, sendo essa técnica chamada de Depuração de Programas baseada em Modelos (Model Based Software Debugging - MBSD). Embora o MBSD possa auxiliar programadores experientes a entenderem e corrigirem suas falhas, essa abordagem precisa ser aprimorada para ser usada por aprendizes de programação. Esse trabalho propõe o uso da técnica de depuração hierárquica de programas, uma extensão da técnica MBSD, para que aprendizes de programação sejam capazes de depurar seus programas raciocinando sobre componentes abstratos, tais como: padrões elementares, funções e procedimentos. O depurador hierárquico de programas proposto foi integrado ao Dr. Java e avaliado com um grupo de alunos de uma disciplina de Introdução à Programação. Os resultados mostram que a maioria dos alunos foi capaz de compreender as hipóteses de falha geradas pelo depurador automático e usar essas informações para corrigirem seus programas. / Model Based Diagnosis (MBD) in Artificial Intelligence is a technique that has been used to detect faulty components in physical devices. MBD has also been used to help senior programmers to locate faults in software with a technique known as Model Based Software Debugging (MBSD). Although this approach can help experienced programmers to detect and correct faults in their programs, this approach must be improved to be used with novice programmers. This work proposes a hierarchical program diagnosis, a MBSD extension, to help novice programmers to debug programs by exploring the idea of abstract components, such as: elementary patterns, functions and procedures. The hierarchical program debugger proposed was integrated to the Dr. Java tool and evaluated with students of an introductory programming course. The results showed that most of the students were able to understand the hypotheses of failure presented by the automated debugger and use this information to provide a correction for their programs
338

Automated state model extraction, testing and change detection through graphical user interface

Aho, P. (Pekka) 01 November 2019 (has links)
Abstract Testing is an important part of quality assurance, and the use of agile processes, continuous integration and DevOps is increasing the pressure for automating all aspects of testing. Testing through graphical user interfaces (GUIs) is commonly automated by scripts that are captured or manually created with a script editor, automating the execution of test cases. A major challenge with script-based GUI test automation is the manual effort required for maintaining the scripts when the GUI changes. Model-based testing (MBT) is an approach for automating also the design of test cases. Traditionally, models for MBT are designed manually with a modelling tool, and an MBT tool is used for generating abstract test cases from the model. Then, an adapter is implemented to translate the abstract test cases into concrete test cases that can be executed on system under test (SUT). When the GUI changes, the model has to be updated and the test cases can be generated from the updated model, reducing the maintenance effort. However, designing models and implementing adapters requires effort and specialized expertise. The main research questions of this thesis are 1) how to automatically extract state-based models of software systems with GUI, and 2) how to use the extracted models to automate testing. Our focus is on using dynamic analysis through the GUI during automated exploration of the system, and we concentrate on desktop applications. Our results show that extracting state models through GUI is possible and the models can be used to generate regression test cases, but a more promising approach is to use model comparison on extracted models of consequent system versions to automatically detect changes between the versions. / Tiivistelmä Testaaminen on tärkeä osa laadun varmistusta. Ketterät kehitysprosessit ja jatkuva integrointi lisäävät tarvetta automatisoida kaikki testauksen osa-alueet. Testaus graafisten käyttöliittymien kautta automatisoidaan yleensä skripteinä, jotka luodaan joko tallentamalla manuaalista testausta tai kirjoittamalla käyttäen skriptieditoria. Tällöin scriptit automatisoivat testitapausten suorittamista. Muutokset graafisessa käyttöliittymässä vaativat scriptien päivittämistä ja scriptien ylläpitoon kuluva työmäärä on iso ongelma. Mallipohjaisessa testauksessa automatisoidaan testien suorittamisen lisäksi myös testitapausten suunnittelu. Perinteisesti mallipohjaisessa testauksessa mallit suunnitellaan manuaalisesti käyttämällä mallinnustyökalua, ja mallista luodaan abstrakteja testitapauksia automaattisesti mallipohjaisen testauksen työkalun avulla. Sen jälkeen implementoidaan adapteri, joka muuttaa abstraktit testitapaukset konkreettisiksi, jotta ne voidaan suorittaa testattavassa järjestelmässä. Kun testattava graafinen käyttöliittymä muuttuu, vain mallia täytyy päivittää ja testitapaukset voidaan luoda automaattisesti uudelleen, vähentäen ylläpitoon käytettävää työmäärää. Mallien suunnittelu ja adapterien implementointi vaatii kuitenkin huomattavan työmäärän ja erikoisosaamista. Tämä väitöskirja tutkii 1) voidaanko tilamalleja luoda automaattisesti järjestelmistä, joissa on graafinen käyttöliittymä, ja 2) voidaanko automaattisesti luotuja tilamalleja käyttää testauksen automatisointiin. Tutkimus keskittyy työpöytäsovelluksiin ja dynaamisen analyysin käyttämiseen graafisen käyttöliittymän kautta järjestelmän automatisoidun läpikäynnin aikana. Tutkimustulokset osoittavat, että tilamallien automaattinen luominen graafisen käyttöliittymän kautta on mahdollista, ja malleja voidaan käyttää testitapausten generointiin regressiotestauksessa. Lupaavampi lähestymistapa on kuitenkin vertailla malleja, jotka on luotu järjestelmän peräkkäisistä versioista, ja havaita versioiden väliset muutokset automaattisesti.
339

An anisotropic Matern spatial covariance model: REML estimation and properties.

Haskard, Kathryn Anne January 2007 (has links)
This thesis concerns the development, estimation and investigation of a general anisotropic spatial correlation function, within model-based geostatistics, expressed as a Gaussian linear mixed model, and estimated using residual maximum likelihood (REML). The Matern correlation function is attractive because of its parameter which controls smoothness of the spatial process, and which can be estimated from the data. This function is combined with geometric anisotropy, with an extension permitting different distance metrics, forming a flexible spatial covariance model which incorporates as special cases many infinite- range spatial covariance functions in common use. Derivatives of the residual log-likelihood with respect to the four correlation-model parameters are derived, and the REML algorithm coded in Splus for testing and refinement as a precursor to its implementation into the software ASReml, with additional generality of linear mixed models. Suggestions are given regarding initial values for the estimation. A residual likelihood ratio test for anisotropy is also developed and investigated. Application to three soil-based examples reveals that anisotropy does occur in practice, and that this technique is able to fit covariance models previously unavailable or inaccessible. Simulations of isotropic and anisotropic data with and without a nugget effect reveal the following principal points. Inclusion of some closely-spaced locations greatly improves estimation, particularly of the Matern smoothness parameter, and of the nugget variance when present. The presence of geometric anisotropy does not adversely affect parameter estimation. Presence of a nugget effect introduces greater uncertainty into the parameter estimates, most dramatically for the smoothness parameter, and also increases the chance of non-convergence and decreases the power of the test for anisotropy. Estimation is more difficult with very “unsmooth" processes (Matern smoothness parameter 0.1 or 0.25) | non- convergence is more likely and estimates are less precise and/or more biased. However it is still often possible to fit the full model including both anisotropy and nugget effect using REML with as few as 100 observations. Additional simulations involving model misspecification reveal that ignoring anisotropy when it is present can substantially increase the mean squared error of prediction, but overfitting by attempting to model anisotropy when it is absent is less damaging. Further, plug-in estimates of prediction error variance are reasonable estimates of the actual mean squared error of prediction, regardless of the model fitted, weakening the argument requiring Bayesian approaches to properly allow for uncertainty in the parameter estimates when estimating prediction error variance. The most valuable outcome of this research is the implementation of an anisotropic Matern correlation function in ASReml, including the full generality of Gaussian linear mixed models which permits additional fixed and random effects, making publicly available the facility to fit, via REML estimation, a much wider range of variance models than has previously been readily accessible. This greatly increases the probability and ease with which a well-fitting covariance model can be found for a spatial data set, thus contributing to improved geostatistical spatial analysis. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297562 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007
340

Model-based Diagnosis of a Satellite Electrical Power System with RODON

Isaksson, Olle January 2009 (has links)
<p>As space exploration vehicles travel deeper into space, their distance to earth increases.The increased communication delays and ground personnel costs motivatea migration of the vehicle health management into space. A way to achieve thisis to use a diagnosis system. A diagnosis system uses sensor readings to automaticallydetect faults and possibly locate the cause of it. The diagnosis system usedin this thesis is a model-based reasoning tool called RODON developed by UptimeSolutions AB. RODON uses information of both nominal and faulty behavior ofthe target system mathematically formulated in a model.The advanced diagnostics and prognostics testbed (ADAPT) developed at theNASA Ames Research Center provides a stepping stone between pure researchand deployment of diagnosis and prognosis systems in aerospace systems. Thehardware of the testbed is an electrical power system (EPS) that represents theEPS of a space exploration vehicle. ADAPT consists of a controlled and monitoredenvironment where faults can be injected into a system in a controlled manner andthe performance of the diagnosis system carefully monitored. The main goal of thethesis project was to build a model of the ADAPT EPS that was used to diagnosethe testbed and to generate decision trees (or trouble-shooting trees).The results from the diagnostic analysis were good and all injected faults thataffected the actual function of the EPS were detected. All sensor faults weredetected except faults in temperature sensors. A less detailed model would haveisolated the correct faulty component(s) in the experiments. However, the goal wasto create a detailed model that can detect more than the faults currently injectedinto ADAPT. The created model is stationary but a dynamic model would havebeen able to detect faults in temperature sensors.Based on the presented results, RODON is very well suited for stationary analysisof large systems with a mixture of continuous and discrete signals. It is possibleto get very good results using RODON but in turn it requires an equally goodmodel. A full analysis of the dynamic capabilities of RODON was never conductedin the thesis which is why no conclusions can be drawn for that case.</p><p> </p>

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