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Analyse et quantification de l'endurance de contact électrique sous sollicitations de fretting / Analyse and quantification of electrical contacts endurance under fretting loadingsJedrzejczyk, Pawel 19 July 2010 (has links)
La sollicitation de fretting apparait comme un processus de dégradation très pénalisant dans les multiples systèmes industriels (aéronautique, industrie automobile, industriels du nucléaire, transports ferroviaires etc. …). Ce processus d’usure engendre dans la plupart des cas soit une réparation (rechargement) des surfaces soit le remplacement des composants (situation la plus souvent observée). La sollicitation de fretting est associée à des micro-déplacements alternés entre deux surfaces en contact. On observe généralement ce type de sollicitation dans tous les contacts soumis à des vibrations ou à des cycles thermiques. La sollicitation de fretting usure dans les contacts électriques est particulièrement pénalisante. Outre l’endommagement des surfaces, ce processus induit une augmentation significative de la résistance électrique des contacts et une perte de fonctionnalité du connecteur en particulier dans les connecteurs basses tensions très sensibles aux fluctuations de la résistance électrique. Pour palier ce problème les industriels de la connectique et leurs clients (industriels de l’automobile) cherchent à mettre en place de nouveaux dépôts palliatifs pour résoudre ces problèmes tout en limitant les surcouts liés à l’utilisation de dépôts nobles tels que l’or.Le sujet de cette thèse porte sur cette problématique avec pour objectif de mettre en place une méthodologie de choix des dépôts pour optimiser la durée de vie des connecteurs. L’étude aborde essentiellement l’influence des conditions de chargements mécaniques et plus particulièrement l’amplitude de débattement / The degradation by fretting appears as a very troublesome process in many industrial systems (spatial, automotive, nuclear industry, railway systems etc. …). This wear process makes it necessary to repair or to replace the destroyed component. The process of degradation by fretting is associated with the micro-displacement between two surfaces in contact. This type of degradation is observed in all types of contacts subjected to the vibrations or thermal variations. The degradation by fretting in electrical contact is particularly dangerous. The wear of the contacting surfaces causes a significant increase of the electrical resistance of the contact and the decay of the functional properties of the connector. This situation concerns especially the low tension connectors very sensible to the fluctuations of the electrical resistance. In order to avoid this situation the automotive industry and its suppliers, the manufacturers of the electrical connectors, are looking for new materials and coatings.The objective of this thesis consists to develop the methodology of choice of the coating materials in order to optimise the lifetime of the electrical contact. The study focuses mainly on the influence of the mechanical conditions, the displacement amplitude in particular, on the performance of the electrical connector.
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Análise de valor percebido em relações entre empresas : um enfoque no segmento metal mecânico / Analysis of perceived value in relationships between companies : a focus on mechanical sectorRibeiro Júnior, Roque, 1974- 26 August 2018 (has links)
Orientador: Oswaldo Luiz Agostinho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T10:45:59Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Resumo: A cada dia que passa torna-se mais importante ter o conhecimento das melhores estratégias de parceria com o cliente e fornecedores. Estas devem ser baseadas na confiança e total envolvimento no negócio que visa atender às necessidades e expectativas de um mercado consumidor. Deve-se também considerar, neste contexto, a velocidade, o volume e o valor da informação que é compartilhada, que, se bem utilizada torna-se uma ferramenta eficaz para alavancar negócios. Dentro desta perspectiva, a identificação correta daquilo que o mercado percebe como valor no produto e serviço oferecido pode ser um diferencial, uma vez que permite à empresa ter seu foco totalmente concentrado no que realmente importa para seu cliente. Este trabalho tem como objetivo analisar os diversos métodos para mensurar o Valor Percebido, selecionar e desenvolver um dado modelo, num ambiente de negócios entre empresas, partindo dos resultados do modelo desenvolvido, verificar as relações entre cliente e fornecedor em âmbito corporativo. Uma revisão do conhecimento a respeito de valor percebido e de seus antecedentes se fez necessária. A qualidade percebida e o sacrifício percebido (esforços e riscos) foram estudados. Efetuou se um estudo da evolução dos modelos de valor percebido apresentados ao longo dos anos. A pesquisa tem enfoque em clientes do segmento metal mecânico, que avaliaram o produto e o serviço de alguns fornecedores de ferramentas de corte. A partir dos resultados obtidos na mensuração, é feita uma análise das reais expectativas e percepções do cliente em relação aos quesitos entregues pelos fornecedores. Os resultados de campo são confrontados com as visões de relacionamento entre cliente e fornecedor de determinados autores, num contexto de negócios corporativos. O procedimento e técnica de abordagem de estudo foram: entrevistas semiestruturadas com gerentes, supervisores, técnicos das indústrias clientes dos fornecedores de ferramentas de corte. Enfim, este trabalho visa contribuir como material adicional de estudo em gestão de valor para o cliente, sendo esta uma ferramenta eficaz para estabelecimento de estratégias para que as empresas em ambientes altamente competitivos obtenham vantagem e ofereçam valor superior aos clientes / Abstract: With each passing day it becomes more important to have knowledge of the best strategies in partnership with the client and suppliers. These should be based on trust and full involvement in the deal that aims to meet the needs and expectations of a consumer market. One should also consider, in this context, speed, volume and the amount of information that is shared, which, if used becomes an effective tool for business leverage. Within this perspective, the correct identification of what the market perceives as value in the product and service offered can be a differentiator, as it allows the company to have its focus totally focused on what really matters to your customer. This study aims to analyze the different methods to measure the Perceived Value, select and develop a data model, a business between undertakings, based on the results of the model developed to examine relationships between customer and supplier at the corporate level. A review of knowledge about perceived value and his background was necessary. The perceived quality and perceived sacrifice (efforts and risks) were studied. We conducted a study of the changing patterns of perceived value presented over the years. The research is focused on clients mechanic metal segment, which reviewed the product and the service of some suppliers of cutting tools. From the results obtained in the measurement, an analysis of actual customer perceptions and expectations in regard to the questions provided by suppliers is taken. Field results are confronted with visions of relationship between customer and supplier of certain authors, in the context of corporate business. The procedure and technique study approach were: semi-structured interviews with managers, supervisors, technicians from customer industries suppliers of cutting tools. Anyway, this work aims to contribute as additional study material in managing customer value, which is an effective tool for establishing strategies for companies in highly competitive environments gain advantage and deliver superior customer value / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica
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Exploring negative brand experiences at the Bottom of PyramidThupae, Keneilwe 17 July 2011 (has links)
The purpose of the research study was to build a deeper understanding of negative brand experiences for consumers at the Bottom of the pyramid segment. The research took an approach of looking at a negative brand experience from end to end, by focusing on elements such as brand contacts, triggers and customer response across different experience dimensions. The literature asserts that for companies to succeed at the Bottom of the Pyramid they need to forego existing assumptions, companies must realise that low income consumers are brand conscious in order to build successful brands. Building successful brands at this market involves offering more than just a functional offering but creating an emotional bond through positive experiences. Such experiences are created each time one is in contact with one of the brand touch-points. The qualitative study showed that consumers value being treated with respect in addition to the provision of a product or service. It also shows that negative brand experiences can happen at various points for both products and services irrespective of whether a product is regarded as hedonic or utilitarian. The nature of negative word of mouth within this segment needs to be explored further as the study showed that there are other factors that influence one to spread negative word of mouth. The research study also shows that consumers are sensitive to brands that demonstrate not to care or those that break trust as such experiences lead to strong negative emotions. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted
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Bulharský román Vítězslava Nezvala, aneb V. Nezval a Dora Gabe v česko-bulharských literárních souvislostech / Bulgarian connection оf Vítězslav Nezval, or V. Nezval and Dora Dabe in Czech - Bulgarian literary relationsGeorgieva Ivanova, Sylvia January 2019 (has links)
- English Vítězslav Nezval's Bulgarian Romance, or Dora Gabe and V. Nezval in Czech-Bulgarian Literary Connections I first heard about the personal encounters and relationship between the poets Dora Gabe and Vítězslav Nezval in the 90s at the Bulgarian Embassy in Prague. And the information was indeed proven to be true - not only had the poets known each other, they even collaborated on translations and inspired one another. The epistolary correspondence between Nezval and Gabe still bears witness to this. Their real- life romance eventually transitioned to their literary work. A substantial and more important fact is that the romance inspired several works by both - Nezval and Gabe. Perhaps the most interesting footprint comes in form of their joint translation of Gabe's auto- biographical prose work Dávno (Once upon a time), which she had primarily written in 1932, and Nezval's novel Jak vejce vejci (Cut from the same cloth) from 1933, although this is merely an indirect illustration of the work and the creative personality of Dora Gabe, a reflection of sorts. Dora Gabe met Nezval in the Autumn of 1931 at a memorial evening held for the passing of Thomas Alva Edison at the Vinohrady Theatre in Prague, during which Nezval's poem Edison was recited. The poet left a direct written testimony about...
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Blending Phone Contacts and Site Visits to Promote Rural Outreach Services: A Randomized Controlled Trial to Assess UsageCarter, Nakia J., Wallace, Rick L., Qiu, Kefeng (Maylene) 20 May 2009 (has links)
Objective: The East Tennessee State University Quillen College of Medicine Library (ETSUQCOML) wanted to determine if the introduction of phone calls to an existing outreach visit increased the usage of the ETSUQCOML’s services.
Methods: Eight hospitals and sixteen clinics were chosen to participate. Two site visits were made a month to each participating institution. A total of two phone calls and two emails a month were given to multiple contacts in the hospital or clinic. The hospitals and clinics were randomized to determine which received the phone call intervention. Interlibrary loan statistics and reference search statistics were then analyzed to determine if there was a statistically significant difference. The data were also analyzed to determine if the intervention was more successful in hospitals or clinics.
Results: Librarians learned to what degree email and phone calls could be substituted for personal visits in an outreach service as a means of maintaining it and not experiencing a decline in service requests.
Conclusions: In today’s economic times, it is important to maintain services to underserved health care providers but to do it in the most cost effective manner. This study has provided helpful data as to the possibility of substituting less expensive contacts such as emails or phone calls for more expensive ones such as face-to-face visits in order to sustain an outreach service. The authors are looking to extend this project to multiple end-points such as six months, nine months, and one year to determine sustainability.
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Investigating Nonnative Contacts in Protein FoldingChen, Chong 09 June 2009 (has links)
No description available.
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Applications of Multichannel Spectroscopic Ellipsometry for CdTe Photovoltaics: From Window Layers to Back ContactsTan, Xinxuan January 2017 (has links)
No description available.
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EXAMINING POTENTIAL SOCIAL CAPITAL THROUGH THE LENS OF INTERSECTIONALITYGOSSETT, JENNIFER LYNN 30 June 2003 (has links)
No description available.
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Analytical Modelling of Isotype HeterojunctionsGil, Manuel 10 1900 (has links)
<p>An <em>isotype heterojunction</em> is a junction between two layers of dissimilar semiconductors both of which are doped either n-type or p-type. These semiconductor structures are found in a variety of optoelectronic devices, such as solar cells, semiconductor lasers, and detectors. Motivated by the structure of third generation inorganic solar cells, this thesis concentrates on the analytical modelling of isotype heterojunctions and its application to the design optimization of these devices. The main development of this work is the introduction of an analytical expression for the current density across an isotype heterojunction valid for arbitrary doping concentration ratios. This result generalizes the standard expression found in the literature, which is limited by the assumption that the doping concentration ratio between the two sides of the heterojunction is equal to one. The generalization is developed by employing the Lambert W function in the solution of the electrostatic boundary condition associated with the heterojunction interface. As done in the derivation of the standard expression found in the literature, the generalization only considers thermionic emission, but the same method can readily be applied for other transport mechanisms. A key feature of this generalized result is that it mathematically contains the expression for the current density across a metal-semiconductor Schottky contact as a limiting case, thereby unifying the treatment of these two heterointerfaces into a single general analytical description. This latter find is particularly significant from a theoretical perspective, considering that the two heterointerfaces are traditionally described as separate topics in the presentation of semiconductor device theory.</p> / Master of Applied Science (MASc)
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Modeling and Electrical Characterization of Ohmic Contacts on n-type GaNAyyagari, Sai Rama Usha 07 March 2018 (has links)
As the current requirements of power devices are moving towards high frequency, high efficiency and high-power density, Silicon-based devices are reaching its limits which are instigating the need to move towards new materials. Gallium Nitride (GaN) has the potential to meet the growing demands due to the wide band-gap nature which leads to various enhanced material properties like, higher operational temperature, smaller dimensions, faster operation and efficient performance. The metal contacts on semiconductors are essential as the interface properties affect the semiconductor performance and device operation. The low resistance ohmic contacts for n-GaN have been well established while most p-GaN devices have still high contact resistivity. Significant work has not been found that focuses on software-based modeling of the device to analyze the contact resistance and implement methods to reduce the contact resistivity. Understanding the interface physics in n-GaN devices using simulations can help in understanding the contacts on p-GaN and eventually reduce its metal contact resistivity.
In this work, modeling of the metal-semiconductor interface along with the effect of a heavily doped layer under the metal contact is presented. The extent of reduction in contact resistivity due to different doping and thickness of n++ layer is presented with simulations. These results have been verified by the growth of device based on simulation results and reduction in contact resistivity has been observed. The effect of different TLM pattern along with different annealing conditions is presented in the work. / Master of Science
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