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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.
801

Indonesian L2 Speakers of English Talking about their ESL Experiences: An Overview

January 2015 (has links)
abstract: This thesis examines the narratives and meta-commentary of Indonesian users of English about their English as a Second Language (ESL) experiences. It approaches interview data with ten Indonesian second language (L2) speakers of English from a narrative analysis/inquiry perspective. Each interview was transcribed according to a modified set of discourse analysis (DA) transcription conventions, then coded by the researcher. The first research question addressed what linguistic devices members of this population used to achieve cohesion and coherence in their narratives, and the second research question examined how members of this population portrayed their L2 selves in their narratives. The data yielded 21 linguistic devices that fell into three levels of frequency. Connectives, discourse markers, and repetition were by far the most common linguistic devices, followed by adverbials, embedded clauses, intensifiers, and the word like (non-comparison uses), which were somewhat frequent linguistic devices. The data also showed that participants constructed their L2 selves using three main categories: agency, identity, and perceptions of English and the U.S.. In regard to identity, participants invoked membership categorization, where they portrayed their identities in relation to other individuals. The study concludes with suggestions for future research, especially relating to Indonesian L2 users of English. / Dissertation/Thesis / Masters Thesis English 2015
802

Hållfasthetssimulering av hydrauliska högtryckskopplingar / Solidmechanical simulation of high pressure hydraulic couplings

von Dewall, Johannes, Johansson-Näslund, Markus January 2018 (has links)
Hydrauliska högtryckskopplingar av typen FEM ½” studeras med avsikten att fastställa en effektiv beräkningsmetodik som kan användas till att prediktera kopplingarnas hållfasthet. Metodiken utgörs av finita element analyser (FEA), och valideras av experimentella trycktester utförda på kopplingstypen FEM ½”. Genom FEA kan kopplingarnas hållfasthetsbeteende och maximala belastningskapacitet studeras virtuellt, vilket minskar behovet av experimentella tester och medför potential för optimering av produkterna. Arbetet utförs på Parker Hannifin AB i Skövde. Experimentella tester utförs på 20 stycken kopplingspar av typen FEM ½” för att utöka förståelsen av kopplingarnas beteende under brottsförloppet och för att prediktera trycket som medför haveri. Testernas genomförande och struktur baseras på metodiken Design of Experiments (DOE). Kritiska komponenter identifieras utifrån experimentets resultat, vilka sedan studeras närmare via FEA. Analyserna valideras utifrån standarder som kopplingarna ska efterfölja, och mätdata insamlad under de experimentella testerna. Från de experimentella testerna är det komponenterna: kulhållaren, styrningen och nippelhuset som upptar belastning i störst utsträckning. Vid haveri framgår två brottmoder som vanliga, att kulhållaren slits isär samt att styrningen brister, båda fallen uppkommer vid approximativt samma tryck. FE-analyserna för styrningen och kulhållaren visar god överensstämmelse med experimentella resultat. Deformationerna skiljer sig dock mellan analyserna och de experimentella testerna, var nippelhusets analyser uppvisar störst avvikelser. FE-modellerna uppvisar god potential för att prediktera samt utvärdera kopplingarnas mekaniska beteende under tryckbelastning. Analyserna är dock helt beroende av ingående data, var saknaden av en verklig materialmodell medför avvikelser från experimentella resultat. Förhållandet framgår tydligt av nippelhuset, vars relaterade härdningsegenskaper saknas. / Hydraulic FEM ½" high pressure couplings are studied with the purpose of establishing an effective methodology that can be used to predict the strength of the couplings. The methodology consists of finite element analyzes (FEA) and is validated by experimental pressure tests, performed on the FEM ½” couplings pairs.  Using FEA, the couplings solid mechanical behavior and maximum load ability can be viewed virtual, reducing the need for experimental tests and gives the potential for optimized products. The work is performed at Parker Hannifin AB in Skovde. Experimental tests are performed on 20 FEM ½” couplings pairs, to understand the solid mechanical behavior of the couplings until failure occurs, and to predict the maximum pressure that can be applied. The experimental structure and performance is based on the method Design of Experiments (DOE). Critical components are identified based on the results from the experimental tests, which are then studied more closely through FEA. The analysis are validated based on the applied material model, and data collected during the experimental tests. From the experimental tests it is shown that the components: ball cage, guide and plug housing are the components in which failure occur. In case of failure, two failure modes appear as common, that the ball cage is worn apart and that the guide burst, both types of failure modes occur at a similar pressure. The analysis for the guide and ball cage corresponds with the experimental outcomes. Differences occurs however when looked at the deformations, in which the plug housing shows the largest deviation when compared to the experimental results. The usage of FE-models appears to be appropriate for predicting and evaluating the mechanical strengths of the couplings during pressure loads. The analysis are however entirely dependent on the input data, where an incorrect material model generates incorrect results. The relationship is shown for the plug housing, which lack the mechanical properties related to curing processes.
803

Développement clinique de l'EP217609 et de son antidote l'avidine / Clinical studies of a new anticoagulant with unprecedented pharmacological profile

Guéret, Pierre 12 December 2017 (has links)
Les pentasaccharides sont des inhibiteurs indirects du facteur Xa ayant des profils pharmacocinétiques très prédictibles. En raison de la liaison de forte affinité des pentasaccharides à l'antithrombine, cette pharmacocinétique peut être prédite mais aussi transférée à d'autres molécules qui leur sont liées de manière covalente. L'EP42675 combine dans une seule molécule, une antithrombine directe réversible peptidomimétique (analogue de l'α-NAPAP), et un pentasaccharide inhibiteur indirect du facteur Xa antithrombine dépendant (analogue du fondaparinux). L'EP217609 est le dérivé biotinylé de l'EP42675. Son action anticoagulante peut être neutralisée par l'avidine qui se lie avec une grande affinité et spécificité à la fraction biotine de l'EP217609. La première indication cible de l'EP217609 et de son antidote l'avidine est la chirurgie cardiaque nécessitant une circulation extracorporelle. La deuxième indication cible est le traitement des syndromes coronariens aigus nécessitant ou non une intervention coronarienne percutanée. Les études précliniques et cliniques de phase I et phase IIa résumées ici démontrent l'intérêt d'un tel concept de couplage avec un pentasaccharide : absence de dissociation entre les deux entités, faible variabilité intra et interindividuelle des paramètres pharmacocinétiques et pharmacodynamiques, et une neutralisation de l'activité anticoagulante de l'EP21609 quasi complète et sans effet rebond. / Pentasaccharides are indirect inhibitors of factor Xa with highly predictable pharmacokinetic profiles. Because of the high affinity binding of pentasaccharides to antithrombin, this pharmacokinetics can be predicted but also transferred to other molecules covalently bound to them. EP42675 combines in a single molecule, a reversible direct antithrombin (α-NAPAP peptidomimetic analog), and a pentasaccharide similar to fondaparinux with an indirect anti-factor Xa activity. EP217609 is the biotinylated derivative of EP42675 whose anticoagulant activity can be neutralized by avidin which binds with high affinity and specificity to the biotin moiety of EP217609.The first target indication of EP217609 and its antidote avidin is cardiac surgery requiring extracorporeal circulation. The second target indication is the treatment of acute coronary syndromes requiring or not a percutaneous coronary intervention.The preclinical and clinical Phase I and IIa studies summarized here demonstrate the value of such a coupling concept to the pentasaccharide: absence of dissociation between the two entities, low intra- and interindividual variability of the pharmacokinetic and pharmacodynamic parameters, and an almost complete neutralization of the EP217609 anticoagulant activity with no rebound effect.
804

Faça no seu ritmo mas não perca a hora: tomada de decisão sob demandado usuário utilizando dados da Web / Take your time, but don´t be late: on-demand decision-making using web data

Silva, Manoela Camila Barbosa da 07 August 2017 (has links)
Submitted by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-16T17:29:35Z No. of bitstreams: 1 SILVA_Manoela_2017.pdf: 5765067 bytes, checksum: 241f86d72385de30ffe23c0f4d49a868 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-16T17:29:46Z (GMT) No. of bitstreams: 1 SILVA_Manoela_2017.pdf: 5765067 bytes, checksum: 241f86d72385de30ffe23c0f4d49a868 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-16T17:29:57Z (GMT) No. of bitstreams: 1 SILVA_Manoela_2017.pdf: 5765067 bytes, checksum: 241f86d72385de30ffe23c0f4d49a868 (MD5) / Made available in DSpace on 2017-10-16T17:30:06Z (GMT). No. of bitstreams: 1 SILVA_Manoela_2017.pdf: 5765067 bytes, checksum: 241f86d72385de30ffe23c0f4d49a868 (MD5) Previous issue date: 2017-08-07 / Não recebi financiamento / In the current knowledge age, with the continuous growth of the web data volume and where business decisions must be made quickly, traditional BI mechanisms become increasingly inaccurate in order to help the decision-making process. In response to this scenario rises the BI 2.0 concept, which is a recent one and is mainly based on the Web evolution, having as one of the main characteristics the use of Web sources in decision-making. However, data from Web tend to be volatile to be stored in the DW, making them a good option for situational data. Situational data are useful for decision-making queries at a particular time and situation, and can be discarded after analysis. Many researches have been developed regarding to BI 2.0, but there are still many points to be explored. This work proposes a generic architecture for Decision Support Systems that aims to integrate situational data from Web to user queries at the right time; this is, when the user needs them for decision making. Its main contribution is the proposal of a new OLAP operator, called Drill-Conformed, enabling data integration in an automatic way and using only the domain of values from the situational data.In addition, the operator collaborates with the Semantic Web, by making available the semantics-related discoveries. The case study is a streamings provision system. The results of the experiments are presented and discussed, showing that is possible to make the data integration in a satisfactory manner and with good processing times for the applied scenario. / Na atual era do conhecimento, com o crescimento contínuo do volume de dados da Web e onde decisões de negócio devem ser feitas de maneira rápida, os mecanismos tradicionais de BI se tornam cada vez menos precisos no auxílio à tomada de decisão. Em resposta a este cenário surge o conceito de BI 2.0, que se trata de um conceito recente e se baseia principalmente na evolução da Web, tendo como uma das principais características a utilização de fontes Web na tomada de decisão. Porém, dados provenientes da Web tendem a ser voláteis para serem armazenados no DW, tornando-se uma boa opção para dados transitórios. Os dados transitórios são úteis para consultas de tomada de decisão em um determinado momento e cenário e podem ser descartados após a análise. Muitos trabalhos têm sido desenvolvidos em relação à BI 2.0, mas ainda existem muitos pontos a serem explorados. Este trabalho propõe uma arquitetura genérica para SSDs, que visa integrar dados transitórios, provenientes da Web, às consultas de usuários no momento em que o mesmo necessita deles para a tomada de decisão. Sua principal contribuição é a proposta de um novo operador OLAP , denominado Drill-Conformed, capaz de realizar a integração dos dados de maneira automática e fazendo uso somente do domínio de valores dos dados transitórios. Além disso, o operador tem o intuito de colaborar com a Web semântica, a partir da disponibilização das informações por ele descobertas acerca do domínio de dados utilizado. O estudo de caso é um sistema de disponibilização de streamings . Os resultados dos experimentos são apresentados e discutidos, mostrando que é possível realizar a integração dos dados de maneira satisfatória e com bons tempos de processamento para o cenário aplicado.
805

Desenvolvimento de indicadores da manufatura enxuta utilizando ferramentas de business intelligence : uma aplicação na manufatura de calçados

Escodeiro, José Roberto 27 February 2009 (has links)
Made available in DSpace on 2016-06-02T19:51:39Z (GMT). No. of bitstreams: 1 2385.pdf: 3560559 bytes, checksum: 71e6c5c7aca71d06463f1bc0bc063005 (MD5) Previous issue date: 2009-02-27 / In the past decades companies around the world have implemented their concepts of Lean Manufacture (LM) with their main focus on business. Together with LM s implementation comes the need of continuous improvement as several sources and historical data volume originate from its processing. Whenever those historical data are, for any reason, discarded without generating indicators the oportunity of transforming data into strategic information is missed. Such situation brings about the need of an adequate performance measurement system of LM. Having this constant monitoring need of LM s performance in mind as a strategic mean for a company to achieve competitivity in the market, this paper aims to develop through Information Technology (IT) and the tools of Business Intelligence (BI) a proposal of managing performance indicators of LM present in shoe production, as an alternative to improve decision making. In order to develop this research, an overview of the literature of LM, BI, Information Systems (IS), performance indicators and shoe manufacturing from the basic concept of LM is offered that, on the other hand, has to do with cost reduction and total cut of waste. This study leads to the seven waste groups of LM, which, together with other published works, can guide and focus so as to reach indicators. By setting indicators and pointing strategy, and also collecting data, the next step is modelling and developing data load in dimentional format prepared to use BI s tools as On-line Analytical Processing (OLAP). Finally, the application is tested in a shoe industry with the load of waste indicator for over production. The final result of the research is a series of analyses of waste information for over production as well as the contribution of the proposed method in terms of easiness, flexibility and practical availability in companies. / Nas últimas décadas, empresas do mundo inteiro têm implementado os conceitos da Manufatura Enxuta (ME) com objetivo estratégico para os negócios. Conforme a manufatura enxuta é implementada, surge também a necessidade de melhoria contínua, e conseqüentemente aparecem várias fontes e volume de dados histórico advindos do seu processamento. Quando esses dados históricos por qualquer motivo são descartados sem gerar indicadores, é desperdiçada a oportunidade de transformar os dados em informação estratégica. Esta situação expõe a necessidade de um adequado sistema de medição de desempenho da manufatura enxuta. Entendendo esta necessidade de monitoramento constante do desempenho da Manufatura Enxuta (ME) como um fator estratégico para as empresas obterem competitividade no mercado; este trabalho busca desenvolver através da Tecnologia da Informação (TI) e das ferramentas de Business Intelligence (BI) uma proposta de gerenciamento de indicadores de desempenho da Manufatura Enxuta (ME) presentes na produção de calçados, como uma alternativa para melhorar a tomada de decisão. Para o desenvolvimento do trabalho foi feita uma revisão da literatura de Manufatura Enxuta (ME), Sistemas de Informação (SI), Business Intelligence (BI), indicadores de desempenho e manufatura de calçados com base no conceito da Manufatura Enxuta (ME), que é a redução de custo pela total eliminação de desperdícios. Isto leva aos sete grupos de desperdício da Manufatura Enxuta (ME), que por sua vez, em conjunto com outros trabalhos publicados, servem de guia e foco para encontrar os indicadores. Com a definição dos indicadores e a estratégia de apontamento e carga dos dados, o próximo passo é uma modelagem e desenvolvimento da carga dos dados em formato dimensional, preparado para utilização de ferramentas de Business Intelligence (BI) como On-line Analytical Processing (OLAP). Por último a aplicação é testada numa indústria de calçados com a carga do indicador de perda por super produção. O resultado final do trabalho é uma série de análises das informações de perda por superprodução, assim como a contribuição do método proposto em termos de facilidade, flexibilidade e viabilidade para uso prático nas empresas.
806

Átomos próximos à superfície: interação de van der Waals. E diodo laser acoplado à transição atômica: realimentação incoerente

Souza Segundo, Pedro Chaves de 24 November 2005 (has links)
Made available in DSpace on 2015-05-14T12:14:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2614177 bytes, checksum: 64cd8eee6f69230497da81e691be96a2 (MD5) Previous issue date: 2005-11-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Interactions with surfaces modify internal and external liberty degrees of atoms next to these surfaces. The dominant long range interaction (which extends itselfs to about an atomic transition wavelength is the van der Waals interaction, usually attractive. Firstly, this thesis treats C3 coefficient, which is characteristic of this interaction and depends on the type of surface and temperature. Other theme is determination of this coefficient using a spectroscopic technique (Selective Reflection) in the atomic cesium system (6S1=2 - 8P3=2 transition) on a dielectric surface. This interaction allows the long range excitation transfer (Förster effect) from atom to the dispersive dielectric surface. Considering small distances (atomic dimensions), interaction becomes repulsive because of electronic orbital overlap between the atom and surface components. The sum of these two kinds of interaction (far and close range) results in a potential well, with discrete energy levels. Next, are presented results of simulations on optic transfer from free atoms to atom-surface bounded states. The radiation sources used on the experiments to evidence atom-surface effects described in the first part of this thesis are resonant diode lasers, with spectral characteristics that must be modified on the laboratory to became useful tools to perform high resolution experiments. The Part II treats diode lasers, beginning from stabilization techniques description and going to a new technique developed on the laboratory during doctoral work, where the laser frequency is controlled by an coupled optical orthogonal feedback with atomic transition to diode. Other effects related to this stabilization technique, as the bi-stability phenomena, are described and interpreted on the last chapter. / Interações dos átomos com superfícies modificam os graus de liberdade internos e externos desses átomos quando próximos a elas. A interação dominante de longo alcance (até a ordem do comprimento de onda das transições atômicas) é a interação de van derWaals, geralmente atrativa. Nesta tese é abordado o coeficiente C3, característico dessa interação e dependente da superfície e temperatura, determinado através do uso de uma técnica espectroscópica (Reflexão Seletiva). Trata-se também da transferência de excitação de longo alcance (efeito Förster) do átomo para a superfície. A curtas distâncias (dimensões atômicas), a interação torna-se repulsiva, devido à sobreposição dos orbitais eletrônicos do átomo incidente e dos constituintes da superfície. A soma das contribuições de curto e de longo alcance resulta em um poço de potencial com níveis discretos de energia que são simulados em uma transferência ótica para esses estados ligados. As fontes de radiação utilizadas nas experiências da primeira parte desta tese são lasers de diodo ressonantes, cujas características espectrais precisam ser modificadas no laboratório para eles se tornarem ferramentas adequadas para a realização de tais experiências de espectroscopia de alta resolução. A Parte II da tese trata de diodos lasers, iniciando com a descrição de técnicas de estabilização e chegando a uma nova técnica desenvolvida no laboratório durante este trabalho de doutorado, onde a freqüência do laser é controlada através de um retorno ótico com polarização ortogonal no diodo acoplado à transição atômica. Outros efeitos relacionados a essa técnica de estabilização, como o fenômeno de bi-estabilidade, são descritos e interpretados no último capítulo desta tese.
807

Étude et conception de réseaux transmetteurs reconfigurables en bande Ka / Study and design of reconfigurable transmitarray antennas in Ka-band

Pham, Trung-Kien 05 December 2017 (has links)
Dans les systèmes de communication et de détection sans fil, l'antenne est un élément indispensable pour transformer l'énergie électrique en ondes électromagnétiques rayonnée dans l'espace, et vice versa. Les antennes sont utilisées dans de nombreux dispositifs militaires et civils, tels que les radars (SAR, secteur automobile, détection de débris, etc.), les instruments biomédicaux, les systèmes de télécommunication (téléphones mobiles, stations de base) pour les communications point à multi-point ou point à point par exemple. Les antennes jouent aussi un rôle essentiel pour le développement de futurs réseaux connectés reliant plusieurs appareils à des utilisateurs en temps réel, par exemple pour l'Internet des objets (IoT). Les réseaux transmetteurs sont une solution attrayante pour de nombreuses applications telles que les communications par satellite (Satcom) ou les futurs réseaux 5G. L'architecture des antennes à réseau transmetteur les rend extrêmement compétitifs comparés aux réseaux phasés par exemple grâce à leur alimentation par onde d’espace et car ils ne souffrent pas du blocage induit par la source primaire, comme c’est le cas pour les réseaux réflecteurs ou les antennes à réflecteur. Grâce à leur fonctionnement en mode transmission, les réseaux transmetteurs peuvent être également facilement montés sur des plates-formes mobiles.Les applications Satcom en bande Ka constituent le secteur applicatif majeur de cette thèse. Cette bande fournit un débit de données élevé à la fois pour les liaisons descendantes et les liaisons montantes, en remplacement des systèmes actuels en bande Ku. Dans ce contexte, il convient aussi de prêter une attention particulière aux communications avec des plates-formes mobiles, par exemple les trains à grande vitesse, les avions, etc., ce qui nécessite de mettre au point des antennes à balayage de faisceau. De nombreuses propriétés avancées sont exploitées depuis ces dernières années pour accroître les débits et la flexibilité des systèmes de communication sans fil, par exemple la polarisation circulaire, la double polarisation, le fonctionnement multi-fréquence ou large bande, le dépointage électronique de faisceau. Pour réduire les coûts, des preuves de concept de réseaux transmetteurs non diélectriques sont également proposées. Cette thèse s’est déroulée dans le cadre du projet ANR TRANSMIL (Reconfigurable TRANSmitarrays for beam steering and beam forming at MILlimetre wave). Les objectifs de cette thèse sont de proposer de nouvelles architectures de réseaux transmetteurs fonctionnant en bande Ka en liaison descendante (de 17,7 GHz à 21,2 GHz) et en liaison montante (de 27,5 GHz à 31 GHz). Différents prototypes ont été conçus et fabriqués afin de valider les concepts proposés en bande X et en bande Ka. Un bon accord entre les résultats numériques et mesurés a été obtenu systématiquement. En particulier, les réseaux transmetteurs à double polarisation que nous avons conçus en bande X présentent un gain de 25 dBi et une bande passante à 3 dB de 20% à 10 GHz. Ces propriétés sont indépendantes de la polarisation du champ rayonné, ce qui signifie que des faisceaux de polarisation linéaire orthogonale peuvent être rayonnés indépendamment dans des directions différentes. Un réseau transmetteur bi-bande fonctionnant en bande Ka a également été mis au point. Sa bande passante à 3 dB est de 10% autour des fréquences centrales (19,5 GHz et 29 GHz) et son efficacité de rayonnement atteint 60%. D’autres concepts ont également été étudiés (réseaux transmetteurs sans diélectrique, réseau transmetteur reconfigurable). / Transmitarray is an attractive solution for front-end devices in the next generation of communications (5G). The spatial-fed architecture of transmitarray antennas can compete with phase-arrays due to the absence of feeding network and with reflectarrays since they do not suffer from feed blockage. Thanks to their operation in transmission mode, transmitarrays can be easily mounted on platforms for outdoor environment applications. With mature printed-circuit board technology, there are unstoppable experiments in various frequency bands from cm-wave to mm-wave and up to terahertz in upcoming years for potential applications. Many advanced properties are exploited in transmitarrays in recent years to meet high demands of communications facilities, for example, circular-polarization, dual-/multi-polarization or frequencies through many techniques. Some experiments are consid-ered to validate eligibility of this antenna type in commercial services or military missions, namely electronically steering beam, broad bandwidth, etc. In terms of cost reduction and rigidity, non-dielectric prototypes are also proposed. The Ka-band Satcom applications are the main objective of this thesis through trans-mitarray solution. This band provides high data rate for both down-link and up-link in replacement of the current Ku-band systems with miniaturized module in next dec-ades. Hence, it is worth to pay attention to communications for moving platforms, for example, high-speed trains, planes, etc.
808

Numerical and experimental analysis of adhesively bonded T-joints : Using a bi-material interface and cohesive zone modelling

Andersson Lassila, Andreas, Folcke, Marcus January 2018 (has links)
With increasing climate change the automotive industry is facing increasing demands regarding emissions and environmental impact. To lower emissions and environmental impact the automotive industry strives to increase the efficiency of vehicles by for example reducing the weight. This can be achieved by the implementation of lightweight products made of composite materials where different materials must be joined. A key technology when producing lightweight products is adhesive joining. In an effort to expand the implementations of structural adhesives Volvo Buses wants to increase their knowledge about adhesive joining techniques. This thesis is done in collaboration with Volvo Buses and aims to increase the knowledge about numerical simulations of adhesively bonded joints. A numerical model of an adhesively bonded T-joint is presented where the adhesive layer is modelled using the Cohesive Zone Model. The experimental extraction of cohesive laws for adhesives is discussed and implemented as bi-linear traction-separation laws. Experiments of the T-joint for two different load cases are performed and compared to the results of the numerical simulations. The experimental results shows a similar force-displacement response as for the results of the numerical simulations. Although there were deviations in the maximum applied load and for one load case there were deviations in the behavior after the main load drop. The deviations between numerical and experimental results are believed to be due to inaccurate material properties for the adhesive, the use of insufficient bi-linear cohesive laws, the occurrence of a combination of adhesive and cohesive fractures during the experiments and dissimilar effective bonding surface areas in the numerical model and the physical specimens.
809

Arquitetura de sistema inteligente para sensoriamento virtual de oxigênio em veículos bicombustíveis com injeção eletrônica / Intelligent system architecture for virtual sensing of oxygen in bi-fuel vehicle with electronic fuel injection

Thiago Richter 12 August 2009 (has links)
A indústria automobilística é um dos mais importantes setores da economia no Brasil e no mundo. Nos últimos anos viu-se praticamente obrigada a melhorar o desempenho de seus veículos produzidos e reduzir seus custos. Um dos marcos desta transformação foi o desenvolvimento do sensor de oxigênio, sendo este um dos principais elementos dos sistemas gerenciadores de motor. Esta dissertação propõe o estudo de arquiteturas de sistemas inteligentes para sensoriamento virtual de oxigênio em veículos bicombustíveis, utilizando-se redes neurais artificiais supervisionadas, com arquitetura Perceptron multicamadas. As topologias implementadas atingiram resultados com erros relativos médios menores que 1% em centenas de topologias. Verificou-se também que para o sensoriamento virtual de oxigênio em veículos bicombustíveis, a abordagem de se realizar treinamentos com todos os tipos de combustíveis, segmentando conjuntos de todo o universo de dados, mostra-se a mais adequada. / The automotive industry is one of the most important sectors in Brazilians economy and in the world. In recent years, this industry has been forced to improve the performance of their produced vehicles and to reduce their costs. One of the landmarks of this transformation was the development of the oxygen sensor, which is one of the main elements of the engine management systems. This dissertation proposes the use of intelligent systems architectures for virtual oxygen sensing of bi-fuel vehicles, using multilayer Perceptron artificial neural networks. The implemented topologies reach results with mean relative errors less than 1% in hundreds of topologies. It was also noted that the approach to train the neural network with all types of fuels, using subsets of data universe, it is the most appropriate to have a virtual sensing of oxygen in bi-fuel vehicles.
810

Influência dos íons cloreto na cinética de redução eletroquímica dos íons de Bi+3 e CU2+ no eletrodo de mercúrio / Influence of chloride ions on the electrochemical reduction of Bi3+ and Cu2+ ions on mercury electrode

Silvia Maria Leite Agostinho 03 November 1975 (has links)
A influência de pequenas concentrações de íons cloreto na cinética de redução eletroquímica dos íons Bi3+ e Cu2+ foi estudada através de medidas independentes de adsorção específica e de cinética eletroquímica. A adsorção específica foi determinada por meio das curvas eletrocapilares obtidas com o método do tempo de gota, para soluções aquosas de misturas de ácido clorídrico xM e de ácido perclórico (1 - x)M. Obeservou-se que, em concentrações de cloreto muito baixas, iguais ou inferiores a 10-2 M, a adsorção específica desses íons segue a isoterma de adsorção de Henry. A cinética da redução eletroquímica dos íons de Bi3+ e Cu2+, na presença de pequenas concentrações de íons cloreto, em meio de ácido perclórico 1 M, foi estudada por polarografia com o eletrodo de mercúrio. Os valores das constantes de velocidade foram calculados, a partir da relação existente entre a corrente, medida em cada potencial, e a corrente de difusão, usando as equações relativas a processos de eletrodos irreversíveis. Estes valores mostraram que, para as concentrações mais baixas de cloreto estudadas, esses íons aceleram as reações Bi3+ + 3e → Bi(Hg) e Cu2+ + 2e → Cu(Hg). O mecanismo de redução, por outro lado, permanece o mesmo já observado por outros autores em soluções de ácido perclórico puro, ou seja, os íons Bi3+ e Cu2+ são reduzidos em etapas de um elétron com velocidades comparáveis. No caso do bismuto, para as concentrações mais altas de cloreto estudadas, o efeito da complexação dos íons Cl- e Bi3+ no meio da solução se torna apreciável e a influência dos íons cloreto na velocidade de redução se deve a uma ação combinada da sua adsorção específica sobre o eletrodo e da sua tendência em formar complexos. No caso do cobre apenas a adsorção específica dos íons cloreto é a responsável pelo seu efeito na cinética do processo, em virtude da não complexação dos íons Cl- e Cu2+ presentes na solução. Tanto no caso do bismuto como o do cobre se observou uma relação linear entre os logaritmos das constantes de velocidade de redução e a carga especificamente adsorvida de íons cloreto, a um potencial constante. Esses resultados estão em concordância com os modelos teóricos de PARSONS e de GUIDELLI e FORESTI, sobre a influência de íons não eletroativos especificamente adsorvidos na cinética de reações de eletrodo. presença de uma carga especificamente adsorvida, dependente do potencial do eletrodo, justifica a variação no coeficiente de transferência à medida que se varia a concentração do íon especificamente adsorvido; no caso do cobre, onde apenas a adsorção específica é a responsável pelo aumento da velocidade de redução eletroquímica, a correção no valor do coeficiente de transferência a partir dos dados de adsorção, coincide com os resultados experimentais obtidos a partir da variação do logaritmo da constante de velocidade com o potencial. / In the present work, the effect of chloride ions in small concentrations on the electrochemical reduction of Bi3+ and Cu2+ ions was studied by means of independent measurements of specific adsorption and electrode kinetics. Specific adsorption was calculated irom electrocapillary curve data, obtained by means of the drop time method for aqueous solutions of xM hydrochloric acid and (1 - x)M perchloric acid mixtures. It was observed that, for low chloride concentrations (less than or equal to 10-2M), specific adsorption of these ions on the mercury electrode obeys the Henrys adsorption isotherm. The kinetics of the electrochemical reduction of Bi3+ and Cu2+ ions, in the presence of emall concentrations of chloride ions in 1M HC104 was studied by dropping mercury electrode polarography. The rate constants was calculated from the ratio between the current, measured at each potential, and the diffusion current, using the equations for irreversible electrode processes. It is shown from these rate constansts, that for the smaller chloride concentrations, the velocity of the reaction Bi3+ + 3e → Bi(Hg) and Cu2+ + 2e Cu(Hg) is increased by the presence of chloride ions. The reduction mechanism remains the same as that observed by other investigators in pure HC104, i.e., the reduction occur in one electron steps and the rates of each step are compa¬rable. In the case of bismuth the effect of complexation of Bi3+ by Cl- ions is appreciable for the higher chloride concentrations; the influence of the chloride ions on the reduction velocity thus results from a combination of its specific adsorption on the electrode and its tendency for complex formation. In the case of copper, only the specific adsorption of chloride ions is responsible for their effect on the electrode process kinetics since there is no complexation of the Cu2+ ion by Cl- in solution. For the reductions of bath bismuth and copper ions, a linear relation between the logarithms of the rate constants and the specifically adsorbed charge of Cl- ions is observed at constant potencial. These results agree with the theoretical models of PARSONS and of GUIDELLI and FORESTI describing the effect of non-electroactive, specifically adsorbed ions on the kinetics of electrode processes. The presence of specifically adsorbed charge, that depends on the electrode potential, explains the observed variation of the transfer coefficient as the concentration of the specifically adsorbed ion is increased. For copper, in which only apecific adsorption is responsible for the increase of the velocity, transfer coefficients corrected using the specific adsorption data are in agreement with the experimental results obtained from the variation of the logarithm of the rate constant with the potential.

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