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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.
31

Contribution à l'étude du comportement dynamique d'un système d'engrenage en présence d'incertitudes / Contribution to the study of the dynamic behavior of a gear system in the presence of uncertainties

Guerine, Ahmed 19 September 2016 (has links)
Dans le cadre de la présente thèse, on a procédé à l’étude du comportement dynamique d’un système d’engrenage comportant des paramètres incertains. Une des principales hypothèses faite dans l’utilisation des méthodes de prise en compte des incertitudes, est que le modèle est déterministe, c’est-à-dire que les paramètres utilisés dans le modèle ont une valeur définie et invariante. Par ailleurs, la connaissance du domaine de variation de la réponse dynamique du système dues aux incertitudes qui découle des coefficients d’amortissement, des raideurs d’engrènement, la présence de frottement entre les pièces, les défauts de montage et de fabrication ou l’inertie des pales dans le cas d’éolienne est essentielle. Pour cela, dans la première partie, on s’applique à décrire la réponse dynamique d’une transmission par engrenage comportant des paramètres modélisés par des variables aléatoires. Pour ce faire, nous utilisons la simulation de Monte Carlo, la méthode de perturbation et la méthode de projection sur un chaos polynomial. Dans la seconde partie,deux approches sont utilisées pour analyser le comportement dynamique d’un système d’engrenage d’éolienne : l’approche probabiliste et l’approche ensembliste basée sur la méthode d’analyse par intervalles. L'objectif consiste à comparer les deux approches pour connaitre leurs avantages et inconvénients en termes de précision et temps de calcul. / In the present work, the dynamic behavior of a gear system with uncertain parameters is studied. One of the principal hypotheses in the use of methods for taking into account uncertainties is that the model is deterministic, that is to say that parameters used in the model have a defined and fixed value. Furthermore, the knowledge of variation response of a gear system involving damping coefficients, mesh stiffness, friction coefficient, assembly defect, manufacturing defect or the input blades in the case of wind turbine is essential. In the first part, we investigate the dynamic response of a gear system with uncertain parameters modeled as random variables. A Monte Carlo simulation, a perturbation method and a polynomial chaos method are carried out. In the second part, two approaches are used to analyze the dynamic behavior of a wind turbine gear system : the probabilistic approach and the interval analysis method. The objective is to compare the two approaches to define their advantages and disadvantages in terms of precision and computation time.
32

Síntese, caracterização e estudo térmico dos complexos de picratos de lantanídeos hidratados com glicina / Synthesis, characterization, and thermal study complexes of lanthanide picrates hydrated with glycine

Martins, Tereza da Silva 17 August 2001 (has links)
Os complexos de picratos de lantanídeos com a glicina foram sintetizados e caracterizados. As análises de carbono, hidrogênio, nitrogênio e dados da análise térmica sugeriram a fórmula geral Ln(pic)3.2Gly.xH2O (Ln = La - Lu, Y; pic = picrato; Gly = glicina; x = 5 para La - Eu e x = 4 para Gd - Lu, Y. Os espectros na região do infravermelho indicam a presença de moléculas de água e sugerem que a glicina está coordenada ao íon lantanídeo através do átomo de nitrogênio do grupo amino. As bandas devidas aos íons picratos também indicam que, pelo menos em parte, eles estão coordenados ao íon lantanídeo de forma bidentada, através de- um oxigênio do grupo fenólico e um oxigênio de um dos grupo orto-nitro. Medidas de condutância eletrolítica em acetona mostram que os complexos comportam-se como não eletrólitos. Os dados obtidos dos difratogramas de raios-X pelo método do pó, mostram a existência de duas séries isomorfas: La - Eu e Gd - Lu e Y. Os parâmetros obtidos no espectro de absorção do composto de Nd no estado sólido para as transições 2G7/2, 4G5/2←4I9/2, indicam que a ligação metal - ligante apresenta pequeno caráter covalente. As bandas devidas às transições 5D0→ 7FJ(J=O, 1, 2, 4) no espectro de emissão do composto de Eu, sugerem a simetria C2v. Os resultados da análise térmica indicam que todos os compostos têm comportamentos similares. Os resíduos obtidos na termogravimetria à 900°C foram identificados e confirmados como sendo óxidos de lantanídeos, através dos resultados da difração de raios-X pelo método do pó. / Complexes of lanthanide picrates with glycine were synthesized and characterized. Analysis of carbon, hydrogen, nitrogen and thermal analysis data suggest a general formula Ln(pic)3.2Gly·xH20 (Ln = La - Lu and Y; pic = picrate; Gly = glycine; x = 5 for La - Eu and x = 4 for Gd - Lu, Y. Infrared spectra indicate the presence of water molecules and suggest that glycine is coordinated to the central ion through the nitrogen ofthe amine group. Bands due to picrate ions also indicate that at least in part they are coordinated as bidentate through the phenoxo group and one oxygen of an ortho-nitro group. Conductance measurements in acetone show that the complexes behave as non-electrolytes. X-ray powder data show the existence of two isomorphous series: La - Eu and Gd - Lu, Y. The parameters obtained from the absorption spectrum of the Nd compound indicated that the metal-ligand bonds present weak covalent character. The bands due to the transitions 5D0→ 7FJ (J=0, 1, 2, 4) in the emission spectra of the Eu compound were interpreted in terms of C2v symmetry. Thermal analyses results indicated that all the compounds present a similar behavior. The residues after thermal decompositon at 900°C were found to be lanthanide oxides, results further confimed by X-ray diffraction powder patterns.
33

Flexibilização do perímetro urbano e suas percussões sobre a expansão urbana : estudo de Lajeado/RS (1984-2016)

Gabe, Mateus Augusto January 2017 (has links)
A ‘flexibilização do perímetro urbano’ é praticada nos municípios, por intermédio do poder público municipal, ao expandirem significativamente suas ‘zonas urbanas’ através de sucessivas ampliações do perímetro urbano. Essa prática, que está em conformidade com o conjunto da legislação vigente, ocorre segundo interesses políticos e econômicos, possivelmente sob demanda do mercado imobiliário e fundiário. O dimensionamento exagerado da zona urbana viabiliza a ocupação de áreas periféricas, distantes de áreas consolidadas, estimulando o processo de expansão urbana dispersa, cujos efeitos negativos repercutem sobre aspectos sociais, econômicos e ambientais dos municípios. A presente pesquisa desenvolve um estudo de caso em Lajeado / RS, no período entre 1984 e 2016, com o objetivo de investigar as ‘origens’ da flexibilização do perímetro urbano e, posteriormente, examinar suas ‘repercussões’ sobre a expansão urbana do município. O estudo das ‘origens’ investiga fatores associados à flexibilização do perímetro no município, considerando o papel da legislação e dos instrumentos de planejamento e analisando a evolução do crescimento urbano do município. O estudo das ‘repercussões’ investiga em que medida a flexibilização influenciou a expansão urbana de Lajeado, examinando de maneira associada, as ampliações ocorridas no perímetro urbano e a evolução da ‘mancha urbana’ (áreas construídas). A metodologia da pesquisa é estruturada por análises multi-temporais de indicadores demográficos, socioeconômicos e espaciais, implementadas com auxílio de técnicas e ferramentas SIG. A metodologia de análise da expansão urbana envolve procedimentos de classificação de imagens de sensoriamento remoto, utilizados na produção de mapas temáticos de cobertura do solo e de ‘áreas construídas’, posteriormente examinados através de métodos de análises ‘pós-classificação’ e ‘métricas da paisagem’. Os resultados obtidos para Lajeado permitiram demonstrar o rápido crescimento urbano do município no período analisado e, evidenciam que as ampliações do perímetro urbano tiveram influências significativas sobre o processo de expansão urbana, que se tornou mais intenso e apresentou características de dispersão espacial das ‘áreas construídas’. / The 'urban growth boundary flexibilization’ is practiced in the municipalities, by the means of the local public administration, to expand significantly its 'urban zone' through successive expansions of the urban growth boundary. This practice, which is in accordance with the existing legislation, occurs in according to political and economic interests, possibly under real estate and land market demands. The exaggerated urban zone sizing enables the occupation of peripheral areas, far from consolidated areas, stimulating the process of dispersed urban expansion, whose negative effects have an impact on social, economic and environmental aspects of the municipalities. This research develops a case study in Lajeado/RS, in the period between 1984 and 2016, with the objective of investigating the 'origins' of the urban growth boundary flexibilization and then, examine their 'repercussions' on the urban expansion. The study of 'origins' investigates factors associated with the boundary flexibilization in the municipality, considering the role of legislation and planning instruments, and analyzing the evolution of the urban growth. The study of ' repercussions ' investigates to what extent the flexibilization influenced the urban expansion of Lajeado, examining the enlargements that occurred in the urban zone, in association with the evolution of the ‘urban footprint’ (built-up areas). The research methodology is based on multi-temporal analysis of demographic, socioeconomic and spatial indicators, implemented with the support of GIS tools and techniques. The methodology of analysis of the urban expansion involves procedures of remote sensing image classification, used for production of thematic maps of land cover and built-up areas, that are afterward examined with methods of 'posclassification' and 'landscape metrics’ analysis. The results obtained for Lajeado allowed to demonstrate rapid urban growth of the municipality in the analysis period, and showed that the enlargement of the urban growth boundary had significant influences on the process of urban expansion, which became more intense and presented characteristics of spatial dispersion of the built-up areas.
34

Síntese, caracterização e estudo térmico dos complexos de picratos de lantanídeos hidratados com glicina / Synthesis, characterization, and thermal study complexes of lanthanide picrates hydrated with glycine

Tereza da Silva Martins 17 August 2001 (has links)
Os complexos de picratos de lantanídeos com a glicina foram sintetizados e caracterizados. As análises de carbono, hidrogênio, nitrogênio e dados da análise térmica sugeriram a fórmula geral Ln(pic)3.2Gly.xH2O (Ln = La - Lu, Y; pic = picrato; Gly = glicina; x = 5 para La - Eu e x = 4 para Gd - Lu, Y. Os espectros na região do infravermelho indicam a presença de moléculas de água e sugerem que a glicina está coordenada ao íon lantanídeo através do átomo de nitrogênio do grupo amino. As bandas devidas aos íons picratos também indicam que, pelo menos em parte, eles estão coordenados ao íon lantanídeo de forma bidentada, através de- um oxigênio do grupo fenólico e um oxigênio de um dos grupo orto-nitro. Medidas de condutância eletrolítica em acetona mostram que os complexos comportam-se como não eletrólitos. Os dados obtidos dos difratogramas de raios-X pelo método do pó, mostram a existência de duas séries isomorfas: La - Eu e Gd - Lu e Y. Os parâmetros obtidos no espectro de absorção do composto de Nd no estado sólido para as transições 2G7/2, 4G5/2←4I9/2, indicam que a ligação metal - ligante apresenta pequeno caráter covalente. As bandas devidas às transições 5D0→ 7FJ(J=O, 1, 2, 4) no espectro de emissão do composto de Eu, sugerem a simetria C2v. Os resultados da análise térmica indicam que todos os compostos têm comportamentos similares. Os resíduos obtidos na termogravimetria à 900°C foram identificados e confirmados como sendo óxidos de lantanídeos, através dos resultados da difração de raios-X pelo método do pó. / Complexes of lanthanide picrates with glycine were synthesized and characterized. Analysis of carbon, hydrogen, nitrogen and thermal analysis data suggest a general formula Ln(pic)3.2Gly·xH20 (Ln = La - Lu and Y; pic = picrate; Gly = glycine; x = 5 for La - Eu and x = 4 for Gd - Lu, Y. Infrared spectra indicate the presence of water molecules and suggest that glycine is coordinated to the central ion through the nitrogen ofthe amine group. Bands due to picrate ions also indicate that at least in part they are coordinated as bidentate through the phenoxo group and one oxygen of an ortho-nitro group. Conductance measurements in acetone show that the complexes behave as non-electrolytes. X-ray powder data show the existence of two isomorphous series: La - Eu and Gd - Lu, Y. The parameters obtained from the absorption spectrum of the Nd compound indicated that the metal-ligand bonds present weak covalent character. The bands due to the transitions 5D0→ 7FJ (J=0, 1, 2, 4) in the emission spectra of the Eu compound were interpreted in terms of C2v symmetry. Thermal analyses results indicated that all the compounds present a similar behavior. The residues after thermal decompositon at 900°C were found to be lanthanide oxides, results further confimed by X-ray diffraction powder patterns.
35

Translation of on object role model schema into the formal language Z

Ravalli, Gilbert, gravalli@swin.edu.au January 2005 (has links)
In the development of information systems for business, structured approaches are widely used in practice. Structured approaches provide a prescription and guidelines for how to go about the process of developing an information system, are relatively easy to learn and provide tools which are well suited to their task. However, the products of structured approaches are sometimes seen to be vague and imprecise since requirements are written using natural language or represented in the form of models which do not have a formal foundation. This vagueness or ambiguity can be the source of problems later in development of the information system. A possible solution to this is to represent requirements using formal methods since these are seen as precise and unambiguous. However, formal methods are typically only a mathematical language for representing requirements. They are often regarded as difficult to learn and use. Even though formal methods of one sort or another have been in existence for many years they are not popular and appear unlikely to become popular in the future. One possible approach to providing the advantages of structured approaches and formal methods is to provide translation procedures from the products of structured approaches to a formal description in a suitable formal language. The work in this thesis follows this theme and is aimed at the creation of a translation procedure from an Object Role Model (ORM) schema to a Z specification. An object role model schema is the end product of a process called the Natural Language Information Analysis Method (NIAM) which is used to produce an information model for an information system. NIAM is a method which has been used successfully in industry since the mid 1970s and continues to be used today. This thesis provides a translation procedure from ORM to Z which is less arbitrary and more comprehensive than previous conversion procedures in the literature. It establishes a systematic method for (i) choosing suitable types and variables for a Z specification and (ii) predicates that express all the standard constraints available in ORM modelling. The style of representation in Z preserves ORM�s concepts in a way that aids traceability and validation. The natural language basis of ORM, namely the use of elementary facts, is preserved. Furthermore, an ORM schema differentiates between abstract concepts and the means by which these concepts are represented symbolically and this thesis provides a representation in Z that maintains the distinction between conceptual objects and their symbolic representation. Identification schemes of entity types are also translated into the Z specification but it is left as an option in the translation procedure. Guiding and evaluating the work conducted here are a published set of criteria for the evaluation of a conceptual schema. These have helped in making decisions regarding the translation procedure and for assessing my work and that of others.
36

A study of the integration of complementary analysis methods : Analysing qualitative data for distributed tactical operations

Lindström, Maria, Ljungwald, Lena January 2005 (has links)
<p>Complex socio-technical systems, like command and control work in military operations and rescue operations, are becoming more and more common in the society, and there is a growing urge for more useful and effective systems. Qualitative data from complex socio-technical systems can be challenging to analyse. This thesis probes one way of enhancing existing analysis methods to better suit this task.</p><p>Our case study is carried out at FOI (the Swedish Defence Research Agency). One of FOI’s tasks is to analyse complex situations, for example military operations, and they have developed an approach called the Reconstruction – exploration approach (R&E) for analysing distributed tactical operations (DTOs). The R&E approach has a rich contextual approach, but lacks a systematic analytic methodology.</p><p>The assignment of this thesis is to investigate how the R&E approach could be enhanced and possibly merged with other existing cognitive analysis methods to better suit the analysis of DTOs. We identified that the R&E approach’s main weaknesses were the lack of structure and insufficient way of handling subjective data, which contributed to difficulties when performing a deeper analysis. The approach also needed a well-defined analysis method for increasing the validity of the identified results.</p><p>One way of improvement was to integrate the R&E approach with several cognitive analysis methods based on their respective individual strengths. We started by analysing the R&E approach and then identified qualities in other methods that complemented the weaknesses in the R&E approach. Finally we developed an integrated method.</p><p>The Critical Decision Method (CDM) appeared to be the most suitable method for integration with the R&E approach. Nevertheless, the CDM did not have all the qualities asked for so we chose to use functions from other methods included in our initial analysis as well; ETA and Grounded theory.</p><p>The integration resulted in a method with a well-defined method for analysis and the possibility to handle subjective data. This can contribute to a deeper analysis of DTOs.</p>
37

Handling modifiability as an integrated part of development

Hervik, John Inge January 2004 (has links)
<p>It is not unusual that software systems are redeveloped when the systems environment changes or new requirements to functionality are found. The reason for this is that system evolution is usually not considered during the initial development of a system.</p><p>In this report we propose a development process focusing on modifiability in security-safety critical systems. The process is based on the standard IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems and the CORAS framework for model-based risk assessment. We focus on integrating modifiability as a non-functionality and extend the development process with an architecture and design phase. Modifiability is addressed using Architecture Tradeoff Analysis Method (ATAM) and Attribute Driven Design (ADD). An evaluation of this process is given by redeveloping a prototype for an already existing security-critical system using the approaches given by the process. The main result from the evaluation showed that we where able to obtain a higher level of modifiability than the original prototype, without compromising the functionality and safety level required.</p>
38

The Concept of ’Selling/Buying’ in the Russian Linguistic Picture of the World : from standard to sub-standard

Osipova, Anna January 2003 (has links)
The thesis belongs to the field of lexical semantics studies, associated with describing the Russian linguistic world-image. The research focuses on the universal situation of purchase and sale as reflected in the Russian lexical standard and sub-standard. The work deals also with subjects related to the sphere of social linguistics: the social stratification of the language, the structure of sub-standard, etc. The thesis is a contribution to the description of the Russian linguistic world-image as well as to the further elaboration of the conceptional analysis method. The results are applicable in teaching Russian as a foreign language, particularly in lexis and Russian culture and mentality studies.
39

Handling modifiability as an integrated part of development

Hervik, John Inge January 2004 (has links)
It is not unusual that software systems are redeveloped when the systems environment changes or new requirements to functionality are found. The reason for this is that system evolution is usually not considered during the initial development of a system. In this report we propose a development process focusing on modifiability in security-safety critical systems. The process is based on the standard IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems and the CORAS framework for model-based risk assessment. We focus on integrating modifiability as a non-functionality and extend the development process with an architecture and design phase. Modifiability is addressed using Architecture Tradeoff Analysis Method (ATAM) and Attribute Driven Design (ADD). An evaluation of this process is given by redeveloping a prototype for an already existing security-critical system using the approaches given by the process. The main result from the evaluation showed that we where able to obtain a higher level of modifiability than the original prototype, without compromising the functionality and safety level required.
40

A Comparative Study On Direct Analysis Method And Effective Length Method In One-story Semi-rigid Frames

Demirtas, Afsin Emrah 01 September 2012 (has links) (PDF)
For steel structures, stability is a very important concept since many steel structures are governed by stability limit states. Therefore, stability of a structure should be assessed carefully considering all parameters that affect the stability of the structure. The most important of these parameters can be listed as geometric imperfections, member inelasticity and connection rigidity. Geometric imperfections and member inelasticity are taken into account with the stability method used in the design. At this point, the stability methods gain importance. The Direct Analysis Method, the default stability method in 2010 AISC Specification, is a new, more transparent and more straightforward method, which captures the real structure behavior better than Effective Length Method. In this thesis, a study has been conducted on the semi-rigid steel frames to compare Direct Analysis Method and Effective Length Method and to investigate the effect of flexible connections to stability. Four frames are designed for different connection rigidities with stability methods existing in the 2010 AISC Specification: Direct Analysis Method and Effective Length Method. At the end,conclusions are drawn about the comparison of these two stability methods and the effect of semi-rigid connections to stability.

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