Contact resistance is the most important and universal characteristic of all types of electrical and thermal contacts. Accurate measurement of contact resistance is important, because it serves as a measure for judging the performance and operational life span of contacts. Rise in contact temperature is one of the major factors that pose a big threat to the stability of electrical contacts. Dissipation of heat by solid conduction through a contact interface is governed by its thermal contact conductance (TCC). This emphasizes the need to study the TCC of an electrical contact along with its electrical contact resistance (ECR). Simultaneous measurement of ECR and TCC is important for understanding the interconnection between these two quantities and the possible influence of one over another. Real time experimental data and analytical correlations can be extremely helpful in developing electrical contacts with improved thermal management capabilities. As a part of the experimental investigation, a test facility has been developed for making simultaneous measurement of ECR and TCC across flat contacts. The facility has the capability of measuring ECR and TCC over a wide range of operating parameters, such as contact pressure, contact temperature, interstitial gaseous media, ambient pressure, etc. It is also capable of determining the electrical resistivity and thermal conductivity of materials as a function of temperature, which is very helpful in analyzing the generated contact resistance data. Using this facility, simultaneous ECR and TCC measurements are made across bare and gold plated contacts of OFHC Cu (oxygen free high conductivity copper) and brass. Simultaneous ECR and TCC measurements are made on nominally flat contacts in the contact pressure range of 0 – 1 MPa and the interface temperature range of 20 – 120 °C. Effect of contact pressure and interface temperature on ECR and TCC is studied on bare and gold coated contacts in vacuum, N2, Ar, and SF6 environments. TCC strongly depends on the thermophysical properties of the interstitial media and shows a significant enhancement in gaseous media, because of the increased interfacial gap conductance compared to vacuum. The gas pressure is varied in the range of 1 – 2.6 bar to study its effect on the gap conductance at different contact pressures and interface temperatures. Minor increase in the ECR observed in gaseous media is found to be independent of the properties of the media. Experimental results indicated that ECR depends on the gas pressure as well as on the applied contact load. Effect of gold coating and its thickness on the ECR and TCC across OFHC Cu and brass contacts is studied. Measurements on electroplated gold specimens having different gold layer thicknesses (0.1, 0.3, and 0.5 µm) indicated that ECR decreases and TCC increases with increasing gold coating thickness. Effect of gold coating on the substrate properties, contact surface tomography, and microhardness is analyzed and correlated to the observed behavior of ECR and thermal gap conductance. An attempt is made to understand and quantify the changes in the contact surface characteristics due to contact loading and heating, by measuring various surface topography parameters before and after the experimentation. Effect of thermal stresses (generated due to temperature variations) on ECR and TCC is studied and inclusion of an experimentally measured temperature dependent load correction factor is suggested in the theoretical models to take into account the effect of thermal stresses in contact assemblies.

Electrical contact resistance (ECR) measurements are needed for judging the performance of electrical appliances. Understanding the behaviour of ECR at low temperature gives a unique opportunity for understanding the contact mechanism itself and controlling the contact resistance for its applications in various areas at these temperatures. In many high-end applications, sophisticated electronic devices are being operated below ambient temperature to improve their performance. The availability of cryogens, improvement in Thermo-Electrical (TE) based Peltier coolers, accelerated the development of these devices. In designing such systems, an accurate measurement of electrical contact resistance below room temperature is important. A detailed experimental investigation has been conducted on electrical contact resistance across bare and coated metal contacts at low temperatures. As a part of the experimental investigation, a test facility capable of varying the contact force, surrounding pressure and temperature, is developed. The design, construction, testing and use of this facility are described. Electrical contact resistance at different contact pressures across copper, OFHC copper and brass with and without gold coatings is measured using 4-wire technique with high accuracy. The test specimen preparation, instrumentation and data acquisition are explained in detail. The setup is standardized by comparing the experimental results obtained across copper-copper contacts in vacuum with the theoretical model. The electrical contact resistance is measured as a function of contact force at different temperatures. The effect of loading and unloading, and the existence of hysteresis are experimentally studied. The electrical properties of conductors improve at low temperature but this is not true for contact resistance. At low temperature the contact resistance increases and it depends on applied contact force, hardness and roughness of the contacting surfaces. Gold-coated contacts exhibited an increase in contact resistance at low temperatures.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Univ., Diss.--Tübingen, 2000.

Thesis (Ph. D.)--Technische Universität, Berlin. / Includes bibliographical references (p. [217]-240).

Cette thèse porte sur l'étude expérimentale de la production d’ions négatifs (H-) par des sources multi-dipolaires microondes (2.45 GHz) fonctionnant à la Résonance Cyclotron des Electrons (RCE). Les sources H- sont nécessaires aux accélérateurs de haute énergie et surtout pour les systèmes d’injection de neutres à haute énergie pour le chauffage des plasmas de fusion. Pour cette étude, deux sources (Prometheus I et ROSAE III) ont été conçues, fabriquées et étudiées. Ces deux sources sont munies de réseaux 2D des sources multi-dipolaires. Il est prouvé que la formation des ions négatifs dans ces sources d'ions, est dû à un mécanisme de production en volume : l'attachement dissociatif des électrons de faible énergie sur des molécules ro-vibrationallement excitées. Contrairement aux sources impliquant des réactions de surface, la production en volume a l’avantage de fonctionner sans césium. Une étude détaillée des principes fondamentaux de la production de H- est réalisée, et les voies possibles pour d'optimisation sont explorées au moyen de : sondes électrostatiques, photodetachment laser, spectroscopie d'émission optique dans la région spectrale du visible et de l'ultraviolet du vide et finalement par spectroscopie d'absorption et de fluorescence induite dans la région spectral de l'ultraviolet du vide en utilisant radiation synchrotron dans un montage expérimental spécial (SCHEME). Analytiquement:La source "Prometheus I" est d'abord étudiée en détails, dans une large gamme de conditions expérimentales (par exemple, pression, puissance, position des zones RCE). Cette étude souligne l’efficacité de production des ions H- en volume, et dévoile une fenêtre de fonctionnement optimal et des voies d'optimisation pour atteindre de plus fortes densités d'ions H-. La contribution du processus d'attachement dissociatif et de l'ionisation résonnante des neutres, à la production H- pour cette source ont été évaluée et la prépondérance de la première finalement confirmée par un modèle rendant compte du bilan des créations et pertes d’espèces.En raison de l'importance des molécules ro-vibrationnallement excitées lors du processus d'attachement dissociatif, l'étude se concentre sur leurs réactions de formation. Deux réactions de formation sont étudiées par des expériences dédiées : la désorption recombinative des atomes d'hydrogène à la surface de divers matériaux ("ROSAE III" et "SCHEME") et l'excitation par impact d'électrons à travers les états singulets temporaires ("Prometheus I"). L'étude de la désorption recombinative a été appréhendée de deux façons différentes. Avec la source ROSAE III, l'impact indirect du processus pour la production d'ions négatifs, à travers la formation de molécules ro-vibrationnellement excitées, a été évaluée dans les plasmas RCE. Dans la deuxième approche, la source "SCHEME" a été conçue pour l'étude de la désorption recombinative des atomes en utilisant le rayonnement synchrotron. La formation des états vibrationnels suite à l’excitation des états singulets, dans la source "Prometheus I" a été étudiée par des mesures d'émission de l'ultraviolet du vide.Une étude qui combine la spectroscopie d'émission de l'ultraviolet du vide, le photodétachement et la caractérisation de la cinétique des électrons par sondes électrostatiques, a permis l'identification des facteurs qui limitent la production d'ions négatifs dans le plasma RCE de "Prometheus I". Des perspectives pour surmonter ces limitations sont finalement proposées. / The present PhD thesis is devoted to the experimental study of hydrogen negative ion (H-) production in microwave-driven (2.45 GHz) multi-dipolar Electron Cyclotron Resonance (ECR) plasma sources. H- sources are required in high-energy accelerators and more importantly in neutral beam injection systems for fusion plasma heating. Towards this directions, two sources (namely, "Prometheus I" and "ROSAE III") are designed, fabricated and studied. Both sources are driven by 2D networks of dipolar ECR elementary sources. It is proven that, negative ion formation in these ion sources is governed by the volume production mechanism, which mostly refers to the dissociative attachment of low energy electrons to vibrationally excited molecules. Contrary to the so called surface sources, volume production sources have the advantage of cesium-free operation. Extended experimental study on fundamental principles of H- production is realized, and possible ways for potential source optimization are tested by means of: electrostatic probes, laser photodetachment, optical emission spectroscopy, both in the visible and vacuum ultra-violet spectral range and finally, vacuum-ultraviolet absorption and induced fluorescence spectroscopy using synchrotron radiation in a specially designed setup ("SCHEME"). Analytically:The source "Prometheus I" is initially studied in detail (EEDF, H- density, optical emission spectra etc), under a wide range of experimental conditions (e.g., pressure, power, ECR-zone location), proving its efficiency for H- volume production, and unveiling optimum operational window and paths for obtaining higher H- densities. The contribution of the dissociative attachment process and neutral resonant ionization to H- production in this source, is evaluated, and the dominance of the former is finally confirmed by an equilibrium model.Due to the importance of the ro-vibrationally excited molecules to the dissociative attachment process, the study is focused on their formation reactions. Two formation reactions are considered by adequately adapted experiments: the recombinative desorption of hydrogen atoms on the surface of various materials (ROSAE III and SCHEME) and the electron impact excitation through temporary singlet states (Prometheus I). The study of recombinative desorption is approached in two different ways. With the source ROSAE III, the indirect impact of the process to the production of negative ions, through the formation of ro-vibrationally excited molecules, is evaluated in ECR plasmas. In the second approach, the source SCHEME is designed for the independent investigation of the recombinative desorption of unexcited atoms using synchrotron radiation based diagnostics. The formation of vibrational states through singlet excitation in the source "Prometheus I" is studied by vacuum-ultraviolet emission measurements.A study that combined vacuum-ultraviolet emission spectroscopy, photodetachment and the characterization of electron kinetics with electrostatic probes, allowed the identification of the factors that limit negative ion production in the ECR plasma of "Prometheus I". Perspectives for overcoming these limitations are finally proposed.

Made available in DSpace on 2010-04-20T20:20:21Z (GMT). No. of bitstreams: 1 149589.pdf: 869774 bytes, checksum: 023fcf29b898c6ba60398c8425dff3bb (MD5) Previous issue date: 2006-04-11T00:00:00Z / This paper studies, through the Glabalscorecard tool, the relationship between the Efficient Consumer Response (ECR) and the Brazilian cut to size paper industry based on the analysis of a distribution chain composed of one industry and two cut to size paper distributors in Brazil. The case is structured on data and information collected from articles, papers, interviews and the interaction with targeted studied companies. The selected methodology for this study is the case analysis. Also analyzed, in light of the ECR, are the issues of collaboration and the efficiency of the distribution chain. By the end, comments are made and considerations around the reached results, including recommendations for the analyzed companies and the suggestion of future academic studies in this field. / Esta dissertação estuda, por meio do uso da ferramenta Globalscorecard, a relação entre o movimento resposta eficiente ao consumidor (ECR) e a indústria brasileira de papéis cut to size, tendo como base o caso da cadeia de distribuição composta por uma indústria e dois distribuidores de papéis cut to size no Brasil. O caso está estruturado com base em dados e informações coletadas em pesquisas, artigos, publicações e nas empresas, objeto do estudo. A metodologia utilizada é a análise de casos. Também está analisada, à luz do ECR, a questão da colaboração e da eficiência na cadeia de distribuição. Ao final, são feitos comentários e considerações acerca dos resultados obtidos, recomendações para as empresas envolvidas e sugestões para futuros estudos acadêmicos nessa área.

Made available in DSpace on 2016-06-02T19:52:11Z (GMT). No. of bitstreams: 1 6803.pdf: 4377604 bytes, checksum: b46cca1821ce323769b3573f295615d3 (MD5) Previous issue date: 2015-02-24 / Universidade Federal de Sao Carlos / The growing interest in supply chain management is due to perception that closer relationship between partners lead to performance improvement of the supply chain as a whole. This is possible, for example, due to the increase of demand visibility provided by information exchange between its members. Better supply and demand synchronization is a consequence of collaborative supply chain management and the adoption of collaborative initiatives helps to build these new collaborative relationships between companies that are seeking to remain competitive in dynamic markets, with more demand from customers. Within this theme, this master thesis analysed five collaborative initiatives through systematic literature review, including Quick Response (QR), Efficient Consumer Response (ECR), Continuous Replenishment Program (CRP), Vendor Managed Inventory (VMI) and Collaborative Planning, Forecasting and Replenishment (CPFR), aiming to develop a theoretical framework to guide the decision making process of adopting and implementing these collaborative initiatives, based on the characteristics, expected benefits, reasons for adopting and possible barriers found in each of them. The analysis of benefits cited in literature showed primary and secondary benefits that are reached by these initiatives. Primary benefits, like better inventory management, should be reached before secondary benefits, like cost reduction, appear. The barriers found in literature were grouped in cultural, behavioral and physical. With technology development, a physical barrier, cultural and behavioral barriers influence more negatively on the relationship than do the physical ones. The reasons for adopting found in literature can be related to economic or market changes in the environment that the supply chain operates, or the form of business organization. Analysing the context of creation and development of these initiatives and their characteristics, it was possible to propose a framework for characterizing the initiatives. It is made of several dimensions for differentiating one initiative from another and can be used as a guide for companies that are planning to implement these initiatives, or help the ones that have already adopted to review its current state and to design a future one. Finally, the theoretical framework to guide the decision making process of adopting a collaborative initiative was proposed, linking the main results of this work, showing to the decision maker the main aspects of concern when adopting a collaborative initiative and highlighting the need to monitor the initiative s performance constantly. / O crescente interesse pela gestão da cadeia de suprimentos deve-se à percepção de que relacionamentos mais próximos promovem a melhoria do desempenho da cadeia como um todo. Isso é possível graças a, por exemplo, o aumento da visibilidade da demanda, proporcionado pela troca de informação entre os membros. A melhor sincronização entre a oferta e a demanda é uma das consequências da gestão colaborativa da cadeia de suprimentos, e as diferentes iniciativas de colaboração permitem a construção destas novas formas de relacionamento entre empresas que buscam a sua permanência em mercados cada vez mais dinâmicos e com clientes cada vez mais exigentes. Dentro desta temática, este trabalho analisou cinco iniciativas de colaboração por meio de revisão sistemática da literatura: Quick Response (QR), Efficient Consumer Response (ECR), Continuous Replenishment Program (CRP), Vendor Managed Inventory (VMI) e Collaborative Planning, Forecasting and Replenishment (CPFR), com o objetivo de propor uma estrutura teórica para orientar o processo decisório de adoção e implementação dessas iniciativas colaborativas, com base nas características, nos benefícios esperados, nos motivadores à adoção e nas possíveis barreiras encontradas em cada uma delas. Após análise dos benefícios mencionados na literatura, estes foram classificados em primários e secundários, sendo que os benefícios primários devem ser alcançados para que os benefícios secundários apareçam. As barreiras encontradas na literatura foram divididas em culturais, comportamentais e físicas. Com o desenvolvimento da tecnologia, uma barreira física, os aspectos culturais e comportamentais passam a ter uma influencia negativa maior no relacionamento. Os motivadores à adoção da iniciativa podem estar relacionados às mudanças econômicas ou de mercado, ou à forma de organização das empresas. Analisando o contexto de criação e desenvolvimento dessas iniciativas, bem como suas características, foi possível propor um framework para caracterização das mesmas que pode servir como um guia para as empresas que desejam implementá-las ou auxiliar as que já adotam a analisarem seu estado atual e projetar seu futuro. Finalmente, foi proposta uma estrutura teórica para auxiliar o processo decisório de adoção de iniciativas colaborativas, unindo os principais resultados deste estudo, mostrando ao tomador de decisão os principais aspectos que devem ser analisados para a adoção de uma iniciativa de colaboração e evidenciando a necessidade de monitoramento constante do desempenho da iniciativa.

Orientador: Ioshiaki Doi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T12:57:52Z (GMT). No. of bitstreams: 1 Pereira_MarcusAnibal_M.pdf: 4318576 bytes, checksum: 61cdc38456d21cf10bf9ccfef5d0bff4 (MD5) Previous issue date: 2005 / Resumo: Isolantes de nitreto de silício (SiNx) para aplicação na tecnologia de isolação LOCOS foram depositados por ECR-CVD a temperatura ambiente e RP/RTCVD, a baixa pressão (5mTorr), com fluxos de gás de N2 de 2.5, 5, 10 e 20sccm, com fluxos de gases de SiH4/Ar fixos de 200sccm/20sccm, e potência de microondas de 1000W em substratos de SiO2-Pad/Si e Si. As estruturas de SiNx/SiO2-Pad/Si e SiNx/Si obtidas foram utilizadas para analisar as características físicas do nitreto de silício. Análises de espectroscopia de infravermelho (FTIR) revelaram a presença de trocas de posição do pico principal das ligações Si-N, das ligações N-H e das ligações Si-N (modo de vibração stretching) nos filmes de nitreto de silício, que está relacionado aos fluxos de N2 na mistura de gases. Os índices de refração entre 1.88 e 2.48 e as espessuras entre 120nm e 139nm foram determinados através de elipsometria. Com estes valores de espessura e com os tempos de ataque em Buffer de HF, foram determinadas as taxas de deposição de 9,6 a 11,1nm/min e taxas de corrosão de 2 a 86nm/min. O processo LOCOS, com etapas seqüenciais de fotolitografia e oxidação térmica, foi executado nas estruturas de SiNx/SiO2-Pad/Si e também de SiNx/Si (sem a presença de óxido "almofada"), com a espessura de cada tipo de nitreto entre 110nm a 215nm e espessura do óxido ?almofada? de 0 a 124nm. Análises de microscópio óptico e de microscopia eletrônica de varredura (SEM) foram utilizadas respectivamente para investigar a resistência dos nitretos de silício à oxidação térmica, executada sob altas temperaturas (1000ºC) e o efeito ?bico de pássaro? formado nas estruturas LOCOS. O nitreto depositado com fluxo de N2 de 10sccm (N10) foi o que apresentou a menor invasão lateral por parte do óxido de campo dentre os nitretos estudados, tanto com quanto sem a camada de óxido de ?almofada? sob o nitreto. O efeito "bico de pássaro" formado nas estruturas LOCOS teve comprimento de avanço lateral variando de 330nm a 2160nm tomando como base a oxidação local executada em temperatura de 1000ºC durante 180 minutos / Abstract: Silicon nitride (SiNx) insulators for LOCOS applications have been deposited by RP/RTCVD and ECR-CVD at room temperature, at low pressure (5mTorr), with N2 flows of 2.5, 5, 10 and 20sccm with fixed SiH4/Ar flows of 200/20sccm with a microwave power of 1000W on SiO2-Pad/Si and Si substrates. SiNx/Si structures were obtained to analyze the physical characteristics of silicon nitride. Fourier transform infrared (FTIR) spectrometry analyses revealed the main peak position shifts of Si-N, N-H and Si-N (stretching mode) bonds for each silicon nitride films, which is related to N2 flows in gas mixture. The refractive indexes between 1.88 and 2.48 and the thickness between 120nm and 139nm were determined by ellipsometry. With these thickness values and with buffered HF etching times, it was also determined the deposition rates of 9,6 - 11,1nm/min and etch rates of 2 -86nm/min. On the SiNx(110 -215nm)/SiO2-Pad(0 - 124nm)/Si and SiNx/Si (without pad oxide) structures, the LOCOS process, with sequential photolithography and thermal wet oxidation steps, was performed. Optical and scanning electron microscopy (SEM) analysis were used to investigate the silicon nitride to thermal oxidation accomplishement at high temperature of 1000 ºC, and bird's beak in the obtained LOCOS structures. On both structures (with and without pad oxide), the smallest lateral extension of the field oxide (bird's beak) was observed for the nitride films obtained with N2 flows of 10sccm (N10). The lengths of the bird's beak, in the obtained LOCOS structure, have resulted between 330nm and 2160nm / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Individuella skillnader i val av copingstrategier är en viktig del av stresshantering och i förlängningen sannolikheten att drabbas av stressrelaterad ohälsa. Syftet med studien var att predicera copingstrategier utifrån personlighet och vuxen anknytning och att undersöka korrelationer mellan personlighet och vuxen anknytning. 174 vuxna deltagare (män = 40) i åldrarna mellan 19 och 83 år svarade på enkäten som bestod av Big Five Inventory (BFI), Erfarenheter av Nära Relationer (ENR) och Brief COPE. BFI mäter personlighetsdragen enligt femfaktormodellen, ENR mäter anknytningsstil enligt de två dimensionerna undvikande respektive ångestladdad anknytning. Brief COPE mäter coping enligt 14 delskalor som kan delas in i problemfokuserad, känslofokuserad och dysfunktionell (undvikande) coping. Resultat avseende korrelationer visade att det fanns en negativ korrelation mellan undvikande anknytning och vänlighet, extraversion samt samvetsgrannhet. Undvikande anknytning och neuroticism korrelerade positivt. Ångestladdad anknytning var svagt negativt korrelerad med samvetsgrannhet samt positivt korrelerad med neuroticism. Ingen av anknytningsstilarna var signifikant korrelerade med öppenhet. Multipla regressionsanalyser visade att extraversion, öppenhet, samvetsgrannhet och undvikande anknytning predicerade problemfokuserad coping. Känslofokuserad coping predicerades av neuroticism och extraversion. Extraversion och undvikande anknytning predicerade socialt stöd. Självanklagelse predicerades av neuroticism. Neuroticism och ångestladdad anknytning predicerade dysfunktionell coping. Personlighet och anknytning kunde tillsammans predicera problemfokuserad och dysfunktionell coping samt socialt stöd. Anknytning bidrog med unik varians för coping utöver personlighetsdimensionerna. Dock bidrog anknytning med relativt lite förklarad varians även om resultatet var signifikant. / Individual differences in choosing coping strategies are an important part of stress management, thereby affecting the risk of health problems related to stress in the long run. The purpose of this study was the prediction of coping strategies from personality and adult attachment and the examination of correlations between coping and adult attachment. 174 adult participants (men = 40) in the ages between 19 and 83 answered a survey comprised of the Big Five Inventory (BFI), Experiences of Close Relationships (ECR) and Brief COPE. BFI measures personality according to the five-factor model. ECR measures attachment according to the two dimensions of avoidant and anxious attachment. Brief COPE measures coping according to 14 subscales which may be divided into problem-focused, emotion-focused, and dysfunctional (avoidance) coping. Results regarding correlations show that there is a negative correlation between avoidant attachment and agreeableness, extraversion, and conscientiousness. There was a positive correlation between avoidant attachment and neuroticism. No significant correlation between attachment and openness was found. Multiple regression analyses show that extraversion, openness, conscientiousness, and avoidant attachment predicted problem-focused coping. Neuroticism and extraversion predicted emotion-focused coping. Social support was predicted by extraversion and avoidant attachment. Neuroticism predicted self-blame. Dysfunctional coping was predicted by neuroticism and anxious attachment. Together, personality and attachment predicted problem-focused and dysfunctional coping, as well as social support. Attachment added unique variance compared to personality alone. However, even though significant, the unique variance contributed by attachment was relatively small.