Thesis (M.A.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 46-50).

The ever increasing awareness of the environment and sustainability drives research to find new solutions in every part of society. In the transport sector, this has led to a goal of replacing the internal combustion engine (ICE) with an electrical engine that can be powered by renewable electricity. As a battery for vehicles, the Li-ion chemistries have become dominant due to their superior volumetric and gravimetric energy densities. While promising, electric vehicles require further improvements in terms of capacity and power output before they can truly replace their ICE counterparts. Another aspect is the CO2 emissions over lifetime, since the electric vehicle itself presently outlives its battery, making battery replacement necessary. If the lifetime of the battery could be increased, the life-cycle emissions would be significantly lowered, making the electric vehicle an even more suitable candidate for a sustainable society. In this context, lithium titanium oxide (LTO) has been suggested as a new anode material in heavy electric vehicles applications due to intrinsic properties regarding safety, lifetime and availability. The LTO battery chemistry is, however, not fully understood and fundamental research is necessary for future improvements. The scope of this project is to investigate degradation mechanisms in LTO-based batteries to be able to mitigate these and prolong the device lifetime so that, in the end, a suitable chemistry for large scale applications can be suggested. The work presented in this licentiate thesis is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) was applied to determine whether the usage of LTO would prevent anode-side electrolyte decomposition, as suggested from the intercalation potential being inside the electrochemical stability window of common electrolytes. It has been found that electrolyte decomposition indeed occurs, with mostly hydrocarbons of ethers, carboxylates, and some inorganic lithium fluoride as decomposition products, and that this decomposition to some extent ensued irrespective of electrochemical battery operation activity. Second, an investigation into how crossover of manganese ions from Mn-based cathodes influences this interfacial layer has been conducted. It was found, using a combination of high-energy x-ray photoelectron spectroscopy (HAXPES) and near-edge x-ray absorption fine structure (NEXAFS) that although manganese is present on the LTO anode surface when paired with a common manganese oxide spinel cathode, the manganese does little to alter the surface chemistry of the LTO electrode.

Made available in DSpace on 2014-06-12T17:41:23Z (GMT). No. of bitstreams: 2 arquivo6383_1.pdf: 2779424 bytes, checksum: b7e970a589e304f6b18441971277720a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / Esta dissertação objetiva analisar os impactos produzidos pela implantação do Sistema Estrutural Integrado da Região Metropolitana do Recife - SEI/RMR, utilizando uma abordagem que relacione a produtividade, a eficiência e a qualidade do serviço, e que considere, também, os pontos de vista dos atores envolvidos com Sistema de Transporte Público, ou seja, o operador, os usuários, a sociedade, e o Governo. O estudo empírico foi realizado na área de influência do Terminal Integrado da PE-15 da Região Metropolitana do Recife. A avaliação do desempenho empregada utilizou uma estrutura denominada de seccional do sistema , pois, considera para análise uma parte do sistema, mais especificamente do Sistema de Transporte Público de Passageiros por Ônibus. Essa análise foi realizada utilizando a técnica antes e depois que compara uma seccional desse Sistema antes e depois da implantação do SEI, ou seja, o Sistema de Transporte Convencional por Ônibus e o Sistema de Transporte Integrado por Ônibus, respectivamente. A avaliação do desempenho conta com um conjunto de indicadores que enfocam os aspectos de produtividade, eficiência e qualidade, sob os pontos de vista dos atores envolvidos com esta parte do sistema. A metodologia construída para esta análise, utilizou como plataforma o trabalho de Anthony R. Tomazinis Productivity, Efficiency, and Quality in Urban Transportation System (1975). Foram utilizados, ainda, os trabalhos de Vuchic (1981), de Lima (1996), de Pereira (1983), de Santana Filho (1992), Molinero e Arellano (1996), e outros. Os resultados desta dissertação apontam para uma avaliação geral positiva quanto à melhoria de produtividade, eficiência e qualidade do serviço, tanto para os usuários e operadores quanto para o Governo, beneficiando a sociedade como um todo. A implantação do SEI minimizou os custos para a produção dos serviços, como também melhorou a sua oferta. Essa dissertação também aponta para a importância de aprofundar os estudos sobre sistemas integrados de transporte contribuindo para o entendimento da mobilidade urbana nas grandes cidades

Inaug.-Diss.--Bonn. / Vita. Bibliography: p. 63.

L'influence de l'électrolyte dans le phénomène d'emballement thermique des batteries Li-ion a été étudiée à travers le rôle des additifs et du sel de lithium. L'analyse du comportement thermique de l'interface graphite lithié/électrolyte a été effectuée grâce à l'utilisation combinée de la DSC et de techniques analytiques (IR, GC/MS…). Parmi les différents additifs commerciaux "Renforceurs de la SEI" testés (VC, FEC, VEC, 1,3-PS, SA), ceux menant à la formation d'un polymère (VC, FEC) se sont avérés être les plus efficaces tant d'un point de vue de la stabilité thermique du graphite lithié que des performances électrochimiques à 45°C. Une nouvelle famille d'additifs, les dicyanokétènes, a également été étudiée et s'est montrée bénéfique sur la sécurité et la cyclabilité. Le sel LiFSI, introduit dans un électrolyte à base de LiPF6 à hauteur de 33% permet, d'une part, une utilisation jusqu'à 4,2 V et d'autre part, une amélioration du comportement thermique du graphite lithié en présence de VC. Des tests de stabilité thermique de prototypes NMC/graphite de faible capacité (~600 mAh) ont permis de confirmer les effets observés à l'échelle de l'électrode négative. De plus, la forte contribution de l'électrode positive dans le phénomène d'emballement thermique a été mise en évidence ainsi que le rôle clé exercé par la contre pression / The electrolyte influence on the Li-ion batteries thermal runaway was studied through the role of additives and lithium salt. The thermal behavior analysis of lithiated graphite/electrolyte interface was performed using DSC along with other analytical techniques (IR, GC/MS…). Among tested commercial "SEI forming improver" additives (VC, FEC, VEC, 1,3-PS, SA), those leading to the formation of polymers (VC, FEC) were found to be the most efficient on both lithiated graphite thermal stability and electrochemical performances at 45°C. A new additives family, named dicyanoketene, was also investigated and showed beneficial effect on the safety and cyclability. The 0.33 M LiFSI and 0.66 M LiPF6 salt ratio can be used until 4.2 V without facing aluminum corrosion and it was found to improve the thermal behavior of lithiated graphite/electrolyte in presence of VC. Thermal stability tests on low capacity (~600 mAh) NMC/graphite prototypes allowed to confirm the effects observed at the negative electrode scale. Moreover, the strong contribution of the positive electrode in the thermal runaway phenomenon was highlighted as well as the key role of back pressure

This single case study explores education of multilingual learners (MLs) from Hispanic backgrounds in an urban inner city school. Using a single case study to answer the research questions was ideal because it allowed the researcher to investigate the school through an objective lens (Gomm, Hammersley, Martyn, & Foster, 2000). The main purpose of the study is to investigate the systems in place in a public school that prevent those students to reach their potential. Several factors have influenced this enlarging academic and achievement gap. Even though, Hispanic community making-up to 16.7% of the entire U.S. population and being the largest and fastest-growing minority group, reported by the U.S. Bureau of Labor Statistics (2011). Educating Hispanic children continues being a challenge. (Liu, C.-Y. A., & Liu, W.-H, 2012). However, with a growing number of Hispanic students in the US schools, it is imperative to improve their education and minimize those barriers. Using a single case study, this qualitative research focused on a single school in Boston where students Hispanic MLs students represents more than 50% of the schools’ population. The researcher visited classrooms and interviewed teachers to collect qualitative data. This information was later coded in themes to find trends and patterns affecting education of MLs. The researcher found that despite existence of several positive systems in place in the classrooms, such as knowledgeable teachers delivering sounds lessons, and strong systems to address family engagement, other factors are preventing students’ success. In effect, the results concluded existence of several opportunities to improve MLs education including changing language programs models and adding resources to be intentional in addressing MLs linguistic and academic needs.

No description available.

Les batteries Li-ion (LIB) sont utilisées comme dispositifs de stockage d'énergie dans les applications automobiles, mobiles ou stationnaire. Cependant, leur vieillissement conduisant à une dégradation de leur performance reste un problème majeur. Les LIB présentent un comportement non uniforme qui entraîne une utilisation incomplète et un vieillissement non uniforme. L'objectif de ce travail est donc d'identifier les facteurs influençant le comportement inhomogène et d'étudier leur effet sur le vieillissement. Une approche combinée modèle/expérimentation est adoptée. Un dispositif expérimental a été développé pour simuler les dispersions thermiques et de potentiels dans les batteries Li-ion commerciales. Ce dispositif est utilisé pour effectuer des tests en cyclage et le vieillissement inhomogène est évalué par des tests de caractérisation effectués pendant et après le cyclage. Des modèles multi-physiques décrivant le comportement des LIB ont été développés pour représenter le comportement du système expérimental. Deux phénomènes de vieillissement identifiés expérimentalement sont pris en compte, à savoir la formation d'une couche de SEI (Solid Electrolyte Interface) et la perte de matière active d'électrode positive. Le premier est fortement dépendant de la température et le second est plus uniforme. Cette approche combinée a permis de montrer que la dispersion thermique avait plus d'impact que les différences de potentiel sur l'homogénéité du vieillissement / Li-ion batteries (LIB) are used as energy storage devices in automobile, mobile and stationary applications. However their lifetime issue is a primary concern resulting in a decreased performance. Li-ion batteries exhibit non-uniform behavior that results in incomplete utilization of the cell energy and non-uniform aging. Thus the objective of this work is to identify the factors influencing the inhomogeneous behavior and to study their effect on aging. A combined modeling and experimental approach is adopted in this work. In the experimental work, a setup is developed that surrogates the thermal and potential gradients occurring in commercial LIB. This setup is used to perform long-term accelerated cycling tests and inhomogeneous aging behavior is assessed. Several characterization tests are performed during and after the completion of the cycling. In the modeling part, multiphysics models describing the electrochemical, electrical and thermal behavior of LIB are developed. These models are appropriately coupled integrated with an aging component to represent the experimental setup behavior. Two main degradation phenomena, namely SEI (Solid Electrolyte Interface) formation and positive electrode active material have been identified experimentally and modelled. The latter is uniform whereas the former is influenced by temperature. Based on this, thermal dispersion impact on the inhomogeneity is greater than potential dispersion

Nedskärningar, effektiviseringar och omstruktureringar är idag nödvändigt för organisationers överlevnad. Detta har medfört förändringar i arbetslivet där individer allt oftare utsätts för situationer som framkallar upplevelser av anställningsotrygghet. Syftet med denna studie är att undersöka om det finns en skillnad i upplevd anställningsotrygghet relaterat till individers yrkesstatus och yrkesgrupp samt att studera om anställningsbarhet och anställningsform kan predicera den upplevda anställningsotryggheten. Data samlades in för Arbetslivskohorten 2004 respektive 2005 efter ett slumpmässigt urval från Sveriges totalbefolkning. Analyserna baseras på enkätsvar från 1548 individer. Resultaten visar att det inte föreligger någon skillnad i upplevd anställningsotrygghet varken vad gäller yrkesstatus eller yrkesgrupper. Däremot hade både anställningsbarhet och anställningsform inverkan på den upplevda otryggheten, i enlighet med tidigare forskning. Istället för yrkesstatus kanske anställningsotrygghet snarare kan skilja sig åt beroende på vilken bransch individen verkar i, något som bör undersökas närmare i framtida studier.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Economia, Administração e Contabilidade, Programa de Pós-Graduação em Economia, Mestrado Profissional em Economia, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-11-06T15:09:20Z No. of bitstreams: 1 2017_PauloRobertodaSilvaNascimento.pdf: 2222315 bytes, checksum: ee985454ca9cc3f842f66fd8ce3522b2 (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2017-12-01T16:26:28Z (GMT) No. of bitstreams: 1 2017_PauloRobertodaSilvaNascimento.pdf: 2222315 bytes, checksum: ee985454ca9cc3f842f66fd8ce3522b2 (MD5) / Made available in DSpace on 2017-12-01T16:26:28Z (GMT). No. of bitstreams: 1 2017_PauloRobertodaSilvaNascimento.pdf: 2222315 bytes, checksum: ee985454ca9cc3f842f66fd8ce3522b2 (MD5) Previous issue date: 2017-12-01 / Esta pesquisa analisa a implantação de um sistema informatizado no âmbito da Universidade de Brasília (UnB), conduzido pelo seguinte questionamento: qual o impacto da implantação do Sistema Eletrônico de Informações (SEI) em substituição ao antigo sistema UnBDoc, suas vantagens e desvantagens. Foram comparados os sistemas UnBDoc e SEI, tendo como objetivo identificar os ganhos e perdas da transição de sistemas informatizados voltados para a gestão de documentos. A metodologia utilizada foi de estudo de caso, com coleta de dados por meio de entrevistas semiestruturada realizadas com os servidores docentes e técnicos administrativos do quadro efetivo da UnB. Entre os resultados obtidos estão às impressões das pessoas depois de transcorrido um ano da implantação do sistema SEI/UnB. Foram destacados aspectos positivos e negativos das funcionalidades do sistema, além de sugestões de melhorias quanto à capacitação dos servidores e a gestão documental. / This research analyzes the implementation of a computerized system in the field of the Universidade de Brasília (UNB), driven by the following question: what is the impact of the implementation of the Sistema Eletrônico de Informações (SEI) to replace the old UnBDoc system, its advantages and disadvantages. The UnBDoc and SEI systems were compared in order to identify the gains and losses of the transition from computerized systems to document management. The methodology used was a case study, with data collection through semistructured interviews conducted with the teaching staff and administrative technicians of the actual staff of the UnB. Among the results obtained are the impressions of people after one year after the implementation of the SEI / UnB system. Positive and negative aspects of the system's features were highlighted, as well as suggestions for improvements in the training of employees and document management.