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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.
41

Aeroacústica de motores aeronáuticos: uma abordagem por meta-modelo / Aeroengine aeroacoustics: a meta-model approach

Rafael Gigena Cuenca 20 June 2017 (has links)
Desde a última década, as autoridades aeronáuticas dos países membros da ICAO vem, gradativamente, aumentando as restrições nos níveis de ruído externo de aeronaves, principalmente nas proximidades dos aeroportos. Por isso os novos motores aeronáuticos precisam ter projetos mais silenciosos, tornando as técnicas de predição de ruído de motores cada vez mais importantes. Diferente das técnicas semi-analíticas, que vêm evoluindo nas últimas décadas, as técnicas semiempíricas possuem suas bases lastreadas em técnicas e dados que remontam à década de 70, como as desenvolvidas no projeto ANOPP. Uma bancada de estudos aeroacústicos para um conjunto rotor/estator foi construída no departamento de Engenharia Aeronáutica da Escola de Engenharia de São Carlos, permitindo desenvolver uma metodologia capaz de gerar uma técnica semi-empírica utilizando métodos e dados novos. Tal bancada é capaz de variar a rotação, o espaçamento rotor/estator e controlar a vazão mássica, resultando em 71 configurações avaliadas. Para isso, uma antena de parede com 14 microfones foi usada. O espectro do ruído de banda larga é modelado como um ruído rosa e o ruído tonal é modelado por um comportamento exponencial, resultando em 5 parâmetros: nível do ruído, decaimento linear e fator de forma da banda larga, nível do primeiro tonal e o decaimento exponencial de seus harmônicos. Uma regressão superficial Kriging é utilizada para aproximar os 5 parâmetros utilizando as variáveis do experimento e o estudo mostrou que Mach Tip e RSS são as principais variáveis que definem o ruído, assim como utilizado pelo projeto ANOPP. Assim, um modelo de previsão é definido para o conjunto rotor/estator estudado na bancada, o que permite prever o espectro em condições não ensaiadas. A análise do modelo resultou em uma ferramenta de interpretação dos resultados. Ao modelo são aplicadas 3 técnicas de validação cruzada: leave one out, monte carlo e repeated k-folds e mostrou que o modelo desenvolvido possui um erro médio, do nível do ruído total do espectro, de 2.35 dBs e desvio padrão de 0.91. / Since the last decade, the countries members of ICAO, via its aeronautical authorities, has been gradually increasing the restrictions on external aircraft noise levels, especially in the vicinity of airports. Because that, the new aero-engines need quieter designs, so noise prediction techniques for aero-engines are getting even more important. Semi-analytical techniques have undergone a major evolution since the 70th until nowadays, but semi-empirical techniques still have their bases pegged in techniques and data defined on the 70th, developed in the ANOPP project. An Aeroacoustics Fan Rig to investigate a Rotor/Stator assembly was developed at Aeronautical Engineering Department of São Carlos School of Engineering, allowing the development of a methodology capable of defining a semi-empirical technique based on new data and methods. Such rig is able to vary the rotation, the rotor/stator spacing and mass flow rate, resulting in a set of 71 configurations tested. To measure the noise, a microphone wall antenna with 14 sensors were used. The broadband noise was modeled by a pink noise and the tonal with exponential behavior, resulting in 5 parameters: broadband noise level, decay and form factor and the level and decay of tonal noise. A superficial kriging regression were used to approach the parameters using the experimental variables and the investigation has shown that Mach Tip and RSS are the most important variables that defines the noise, as well on ANOPP. A prediction model for the rotor/stator noise are defined with the 5 approximation of the parameters, that allow to predict the spectra at operations points not measured. The model analyses of the model resulted on a tool for results interpretation. Tree different cross validation techniques are applied to model: leave ou out, Monte Carlo and repeated k-folds. That analysis shows that the model developed has average error of 2.35 dBs and standard deviation of 0.91 for the spectrum level predicted.
42

Modelagem de sistemas de informação na internet como sistemas de workflow sobre documentos estruturados / Internet information systems modelling how workflow systems witch structured documents

Weinfurter, Maristela Regina January 2001 (has links)
A construção de aplicações Web é algo complexo, pois envolve requisitos não previstos na modelagem de sistemas convencionais. O ambiente Web agrega características como: navegabilidade, estruturação de hiperdocumentos, workflow, acessibilidade, escalabilidade, usabilidade, compatibilidade, interoperabilidade, segurança, aspectos culturais, entre outros. O presente trabalho propõe que a modelagem de sistemas de informação na Internet incorpore características existentes na modelagem de sistemas de gerência de workflow manipulando hiperdocumentos. A notação utilizada é uma extensão à notação da UML (Unified Modeling Language). Esta consiste de novos estereótipos que modelem hiperdocumentos e sistemas de gerência de workflow em sistemas de informação na Web. A extensão propõe a utilização de diagrama de atividades estendido para modelar o workflow de atividades, o qual manipula hiperdocumentos envolvidos no domínio de uma aplicação Web. Os hiperdocumentos são modelados através de diagramas de estrutura de documentos, que são derivados do diagrama de classes da UML. A navegabilidade dos documentos é desenhada através dos diagramas de contexto de navegação e restrições de acessos de em casos de uso. Finalizando a modelagem, o diagrama de estrutura de documentos recebe todas as características dinâmicas, estáticas e de ligação que são modeladas através dos diagramas estendidos bem como pelos diagramas comportamentais e estáticos da UML. A modelagem segue a notação da UML, sendo sugerido que numa primeira etapa, modele-se os hiperdocumentos e sua estruturação preliminar. Na seqüência, com auxílio do diagrama de casos de uso, modela-se o fluxo de atividades através do diagrama de atividades estendido. Após este levantamento, tanto de documentos quanto de atividades envolvidas no domínio da aplicação, modela-se o contexto de navegação e restrições em acessos de casos de uso, que evidenciam os componentes de ligação necessários à navegabilidade entre os hiperdocumentos. Através da extensão proposta à notação da UML, que considera aspectos de workflow, estruturação de hiperdocumentos e navegabilidade, as fases de projeto e implementação de software, sofrem menos alterações e interferências de adaptação às características das ferramentas de implementação para este novo ambiente. / Implementation of Web applications is a complex task since it involves requirements not previously accounted for modelling conventional systems. The Web environment possesses characteristics such as ease of navigation, hyperdocument structuring, workflow, access and scale facilities, usability, compatibility and interoperability, safety and cultural aspects amongst others. The present work proposes that modelling of information systems in the Internet incorporate the existing characteristics of modelling workflow management systems to handle structured hyperdocuments. The notation used is an extension to the UML (Unified Modelling Language) notation, which consists in new stereotypes for hyperdocument modelling and incorporated workflow in information systems. The extension proposes use of the extended diagram of activities to model the activity workflow which will handle the hyperdocuments involved in the domain of a Web application. The hyperdocuments will be modelled using diagrams of document structure, which are derived from the UML class diagrams. The navigation of documents is designed using the surfing context diagrams and access restriction associated to the use cases. Modelling is finalised by adding to the document structure all the dynamic, static and link characteristics which are modelled though the extended diagrams, as far as the behaviour and static diagrams of the UML. The modelling procedure follows the UML notation, being suggested that, in a first step, the modelling of a preliminary document structuring. In sequence, using the diagram of use cases, the activity flow is modelled by using the extended diagram of activities. After the research procedures associated to documents and activities related to the application domain, the surfing contexts and access restrictions of the use cases are modelled to evince the link components necessary to the navigation amongst documents. The use of the proposed extension to the UML notation, which accounts for workflow aspects, hyperdocument structuring and its navigation, will lead to less changes of the project development and software implementation to account for the characteristics of the implementation tools for this new environment.
43

Uma abordagem MDD para prover integridade topológica e de rede em projeto conceitual de banco de dados espaciais

SARMENTO, Jones Cavalcanti 28 August 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-01T11:58:46Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_Jones_final.pdf: 3458864 bytes, checksum: 62e534b2f1fc2266364c4ce46ccf020a (MD5) / Made available in DSpace on 2016-07-01T11:58:46Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_Jones_final.pdf: 3458864 bytes, checksum: 62e534b2f1fc2266364c4ce46ccf020a (MD5) Previous issue date: 2015-08-28 / FACEPE / Model-Driven Development (MDD) é um paradigma que usa modelos como o principal artefato no processo de desenvolvimento de sistemas. Isto é, neste paradigma, modelos não são apenas artefatos de documentação, pois devem corresponder a códigos executáveis. Em projetos de Banco de Dados Espaciais (BDE), existem várias linguagens de modelagens (e.g., OMT-G, MADS, GeoProfile e UML-GeoFrame), as quais permitem representar características espaciais (e.g., Múltiplas Representações e Relacionamento Espacial) por meio de uma ferramenta do tipo Computer-Aided Software Engineering (CASE). Embora essas linguagens sejam bem exploradas e difundidas na literatura, constatou-se que estas têm deficiências para modelar e implementar integridade espacial a partir de entidades com múltiplas representações. Assim, de modo a avançar o estado da arte sobre projeto de BDE, este trabalho faz uma análise dos principais trabalhos relacionados, e, de modo a contribuir para superar as deficiências encontradas, propõe uma extensão espacial para a linguagem de modelagem Enhanced Entity Relationship (EER). Essa extensão é implementada na ferramenta EERCASE e avalidada por meio de uma análise comparativa com os principais trabalhos relacionados, evidenciando seus pontos fortes e fracos. / Model-Driven Development (MDD) is a paradigm that uses models as the primary artifact in the systems development process. That is, in this paradigm, models are not only documentation artifacts, since these should be the executable code. In Spatial Databases projects (SDB), there are several modeling languages (e.g., OMT-G, MADS, GeoProfile and UML-GeoFrame), which allow to represent spatial characteristics (e.g., Multiple Representations and Spatial Relationship) by means of a tool type Computer-Aided Software Engineering (CASE). Although these languages are better exploited and widespread in the literature, it was found that they have deficiencies in modeling and implement spatial integrity from entities with multiple representations. Thus, in order to advance the state of the art in SDB project, this paper analyzes the main works related and, in order to contribute to overcome the deficiencies, proposes a spatial extension for modeling language Enhanced Entity Relationship (EER). This extension is implemented in tool EERCASE and evaluated through a comparison with the main work related, highlighting their strengths and weaknesses.
44

A methodology for situated and effective design of haptic devices

Sun, Xuan January 2017 (has links)
The realism of virtual surgery through a surgical simulator depends largely on the precision and reliability of the haptic device. The quality of perception depends on the design of the haptic device, which presents a complex design task due to the multi-criteria and conflicting character of the functional and performance requirements. In the model-based evaluation of the performance criteria of a haptic device, the required computational resources increase with the complexity of the device structure as well as with the increased level of detail that is created in the detail design phases. Due to uncertain requirements and a significant knowledge gap, the design task is fuzzy and more complex in the early design phases. The goal of this thesis is to propose a situated, i.e., flexible, scalable and efficient, methodology for multi-objective and multi-disciplinary design optimization of high-performing 6-DOF haptic devices. The main contributions of this thesis are: 1. A model-based and simulation-driven engineering design methodology and a flexible pilot framework are proposed for design optimization of high-performing haptic devices. The multi-disciplinary design optimization method was utilized to balance the conflicting criteria/requirements of a multi-domain design case and to solve the design optimization problems concurrently. 2. A multi-tool framework is proposed. The framework integrates metamodel-based design optimization with complementary engineering tools from different software vendors, which was shown to significantly reduce the total computationally effort. 3. The metamodeling methods and sampling sizes for specific performance indices found from case studies were shown to be applicable and usable for several kinds of 6-degrees-of-freedom haptic devices. 4. The multi-tool framework and the assisting methodology were further developed to enable computationally efficient and situated design multi-objective optimization of high-performing haptic devices. The design-of-experiment (DOE) and metamodeling techniques are integrated with the optimization process in the framework as an option to solve the design optimization case with a process that depends on the present system complexity. / <p>QC 20171108</p>
45

[en] DIAGRAM EDITOR DRIVEN BY METAMODELS / [pt] EDITOR DE DIAGRAMAS DIRIGIDO POR METAMODELOS

ANDRE LUIZ CASTRO DE ALMEIDA REIS 07 November 2011 (has links)
[pt] O uso de editores de diagramas tem se mostrado muito útil para a elaboração de soluções de design na área de Interação Humano-Computador. Eles facilitam o uso da linguagem e o controle sobre os seus elementos, evitando que o usuário utilize itens lexicais que não pertençam ao vocabulário da linguagem. Esses elementos estão definidos em um metamodelo, que basicamente consiste em um conjunto de conceitos dentro de um determinado domínio. Com isso, o usuário ganha agilidade e confiabilidade no processo de criação. Porém, muitos editores não garantem que a solução concebida obedeça à sintaxe da linguagem. Para isso, torna-se necessário um editor que, além de ter controle sobre os símbolos da linguagem, forneça também apoio gramatical para o uso de modelos, de forma não apenas gráfica, mas também fazendo uso das regras de sintaxe de cada metamodelo. Com esse conjunto de regras que define as combinações válidas dos elementos da linguagem, o usuário pode ser alertado sobre possíveis infrações que estejam acontecendo durante a elaboração da solução. As regras descrevem a sintaxe da linguagem através de uma gramática. Analisar sintaticamente diagramas significa tentar encontrar uma sequência de aplicações de regras que derivam de uma gramática ou de alguma representação dela. Levando em consideração essa abordagem, este trabalho apresenta um estudo sobre editores de diagramas dirigidos por metamodelos e uma ferramenta que possibilita ao usuário, a partir da definição de um metamodelo, acoplá-lo a um editor de diagramas genérico para linguagens visuais, em que se possa controlar tanto o vocabulário quanto a gramática dos diagramas criados. Desta forma, o objetivo da atual pesquisa é propor uma ferramenta que englobe estas soluções e que seja focada nas linguagens visuais comuns na área de Interação Humano-Computador como MoLIC, CTT e Statecharts. / [en] The use of diagram editors has been very useful for creating design solutions in the area of Human-Computer Interaction. They facilitate the use of modeling languages and provide control over the elements of the solution space, preventing the user from using an invalid lexical item of the chosen language. These elements are defined in a metamodel, which basically consists of a set of concepts with-in a given domain. As a result, users gain speed and reliability in the process of creation. However, many editors do not guarantee that designed solution meets the language syntax. For this, we need an editor that, in addition to having control over the language symbols, also provides support for the use of models, going beyond graphical editing and also making use of the syntax rules defined in each metamodel. With this set of rules that define the form of language, the user may be warned of possible rule violations while building the solution. The rules describe the syntax of the language through its grammar. To parse a diagram means to try to find a sequence of applications of rules that derive from a grammar or some representation of it. Considering this approach, this dissertation presents a study on diagram editors, and a metamodel-driven tool that allows the user to, by defining a metamodel, make use of a generic diagram editor for visual languages that can control the vocabulary and grammar of the created diagrams. Thus, the goal of current research is to propose a tool that encompasses these solutions and is focused on visual languages common in the area of Human- Computer Interaction, such as MoLIC, CTT and Statecharts.
46

Développement d’une nouvelle méthode de réduction de modèle basée sur les hypersurfaces NURBS (Non-Uniform Rational B-Splines) / Development of a new metamodelling method based on NURBS (Non-Uniform Rational B-Splines) hypersurfaces

Audoux, Yohann 14 June 2019 (has links)
Malgré des décennies d’incontestables progrès dans le domaine des sciences informatiques, un certain nombre de problèmes restent difficiles à traiter en raison, soit de leur complexité numérique (problème d’optimisation, …), soit de contraintes spécifiques telle que la nécessité de traitement en temps réel (réalité virtuelle, augmentée, …). Dans ce contexte, il existe des méthodes de réduction de modèle qui permettent de réduire les temps de calcul de simulations multi-champs et/ou multi-échelles complexes. Le processus de réduction de modèle consiste à paramétrer un métamodèle qui requiert moins de ressources pour être évalué que le modèle complexe duquel il a été obtenu, tout en garantissant une certaine précision. Les méthodes actuelles nécessitent, en général, soit une expertise de l’utilisateur, soit un grand nombre de choix arbitraires de sa part. De plus, elles sont bien souvent adaptées à une application spécifique mais difficilement transposable à d’autres domaines. L’objectif de notre approche est donc d’obtenir, s'il n'est pas le meilleur, un bon métamodèle quel que soit le problème considéré. La stratégie développée s’appuie sur l’utilisation des hypersurfaces NURBS et se démarque des approches existantes par l’absence d’hypothèses simplificatrices sur les paramètres de celles-ci. Pour ce faire, une méta heuristique (de type algorithme génétique), capable de traiter des problèmes d’optimisation dont le nombre de variables n’est pas constant, permet de déterminer automatiquement l’ensemble des paramètres de l’hypersurface sans transférer la complexité des choix à l’utilisateur. / Despite undeniable progress achieved in computer sciences over the last decades, some problems remain intractable either by their numerical complexity (optimisation problems, …) or because they are subject to specific constraints such as real-time processing (virtual and augmented reality, …). In this context, metamodeling techniques can minimise the computational effort to realize complex multi-field and/or multi-scale simulations. The metamodeling process consists of setting up a metamodel that needs less resources to be evaluated than the complex one that is extracted from by guaranteeing, meanwhile, a minimal accuracy. Current methods generally require either the user’s expertise or arbitrary choices. Moreover, they are often tailored for a specific application, but they can be hardly transposed to other fields. Thus, even if it is not the best, our approach aims at obtaining a metamodel that remains a good one for whatever problem at hand. The developed strategy relies on NURBS hypersurfaces and stands out from existing ones by avoiding the use of empiric criteria to set its parameters. To do so, a metaheuristic (a genetic algorithm) able to deal with optimisation problems defined over a variable number of optimisation variables sets automatically all the hypersurface parameters so that the complexity is not transferred to the user.
47

Optimalizace tvaru mazací mezery hydrodynamického ložiska s využitím umělých neuronových sítí / Lubricant gap shape optimization of the hydrodynamic thrust bearing using artificial neural networks

Kukla, Lukáš January 2020 (has links)
The thesis deals with the description of the main parts of the turbocharger and explains the concept of optimization. Furthermore, the work deals with the description of the flow of real fluids and lubrication of the hydrodynamic bearing. The work deals with the creation of a computational model, metamodel and subsequent search for a global extreme. In particular, the neural network metamodel technique is used in metamodel formation.
48

Structural Graph-based Metamodel Matching

Voigt, Konrad 02 November 2011 (has links)
Data integration has been, and still is, a challenge for applications processing multiple heterogeneous data sources. Across the domains of schemas, ontologies, and metamodels, this imposes the need for mapping specifications, i.e. the task of discovering semantic correspondences between elements. Support for the development of such mappings has been researched, producing matching systems that automatically propose mapping suggestions. However, especially in the context of metamodel matching the result quality of state of the art matching techniques leaves room for improvement. Although the traditional approach of pair-wise element comparison works on smaller data sets, its quadratic complexity leads to poor runtime and memory performance and eventually to the inability to match, when applied on real-world data. The work presented in this thesis seeks to address these shortcomings. Thereby, we take advantage of the graph structure of metamodels. Consequently, we derive a planar graph edit distance as metamodel similarity metric and mining-based matching to make use of redundant information. We also propose a planar graph-based partitioning to cope with large-scale matching. These techniques are then evaluated using real-world mappings from SAP business integration scenarios and the MDA community. The results demonstrate improvement in quality and managed runtime and memory consumption for large-scale metamodel matching.
49

A TAXONOMY AND METAMODEL FOR GAMIFIED AGILE DEVELOPMENT

Zoric, Andjela, Knezevic, Tamara January 2021 (has links)
Gamification is applied in several aspects of software engineering. There are several concrete examples of theapplication of gamification to modern development approaches, such as Agile. Nevertheless, a classification ofcore elements that gamified Agile development should entail, to be used as a reference for systematically andconsistently design gamified Agile development processes, is missing. The goal of this thesis is to, starting fromconcrete instances of gamified Agile development, generalize the common aspects and propose a classificationof core elements as a reference taxonomy. We designed a research method based on the following four coreactivities: (i) analysis of the state of the art in Gamification applied to Agile development processes, (ii)definition of a taxonomy for Gamified Agile Development, (iii) formalization of the taxonomy in a metamodel,(iv) validation of the metamodel by instantiation of existing concrete examples of gamified Agile development.The contributions of this thesis are a structured taxonomy for gamified Agile development and its formalizationin an instantiable metamodel. The metamodel was validated by instantiating it and comparing it to the existingexamples from literature.
50

Design Parameter Identification and Verification for Thermoplastic Inserts

Ozarkar, Malhar January 2020 (has links)
Inserts are a crucial part of household and industrial furniture. These small plastic parts which often go unnoticed to the naked eye perform crucial functions like providing a base for the furniture, leveling the furniture, safeguarding the user from edges of the tubes used and providing an aesthetic finish. The inserts have a wing like structure on the exterior which enables them to be inserted and securely held in the tubes. The inserts are assembled into the pipes manually or through machines. The force required to install these inserts in the tube is called a push-in force whereas a pull-out force is the force required for removal of the is called a pull-out force. These forces are experienced by someone who assembles the furniture together. Thus, these forces directly define the ease with which the furniture can be assembled. In the first part of the present thesis, these push-in and pull-out forces are predicted using finite element simulations. These finite element simulations were validated by performing physical assembly and disassembly experiments on these inserts. It was found that the finite element simulations of the insert are useful tool in predicting the push-in forces with a high accuracy.   These push-in and pull-out forces for a single insert vary by 2-5 times when the dimensional variations in the tube are considered. The dimensional variations can be a result of the manufacturing processes from which these tubes are produced. The maximum and minimum dimensions that the tube can have are defined by the maximum material condition (MMC) and the least material condition (LMC). To reduce the variation in push-in and pull out forces, a stricter tolerance control can be applied to the manufacturing process. To avoid this cost while having a lower variation in the push-in and pull out forces, the design of the insert was modified. To achieve this enhanced design of the insert, a metamodel based optimization technique was used in the second part of the thesis. For this optimization, the geometrical parameters - wing height, wing diameter and stem thickness the of the insert were identified as the crucial factors which govern the assembly/disassembly forces. The identification of these parameters was done through a design of experiments. These parameters were then varied simultaneously in a metamodel based optimization which had an objective to minimize the variation in forces observed for an insert when the maximum material condition and the least material conditions are considered. The result for the enhanced design of the insert was then stated in terms of the ratio of these identified parameters. The modified design of the insert not only enables the manufacturer to have better performance, but also reduces the amount of plastic material required for manufacturing of the insert.

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