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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.
1221

Three essays on the American public's war support calculus: evidence from experiments

Oliver, Alexander James 13 March 2017 (has links)
This dissertation consists of three essays on the American public's war calculus that hang together in two main ways. First, these essays all attempt to quantitatively measure how certain things about a mission abroad--including the positions of domestic and international elites on it, its American and enemy casualties, its chance of success and main objective, its dollar cost and duration, its location on the planet--causally impact the public's support at home. The first essay simultaneously measures the causal impacts of sixty features of a war, obtaining a rough outline of the public's calculus on war as a mathematical function. The second essay measures the causal impacts of accumulating American and insurgent body counts over time during a war, estimating their dynamic rate of change. And the third essay measures the causal impacts of domestic political elites during parallel real and hypothetical wars, discovering a new mechanism by which the public responds to their position-taking at home. But these measurements wouldn't be possible without the second way these three essays hang together: all of them employ the experimental method. These essays involve survey experiments that are atypical and nonstandard in the use of force literature. The first essay uses a conjoint experiment, which can powerfully estimate the causal impact of relatively many treatments with relatively few research subjects because of its efficiency. The second essay uses a panel experiment, which can estimate the cumulative causal impact of a dynamic treatments at many different points in time because of its sequential structure. And the third essay uses both real and hypothetical experiments, which can uncover how different contexts condition the estimates of treatment impacts.
1222

The multidimensionality of well-being : theory, measurement and empirical investigations

Linton, Myles-Jay January 2017 (has links)
Background: Well-being within this thesis is defined as the multidimensional quality of a person’s life, which can be broken down into ‘subjective’ and ‘objective’ forms. Despite persistent study, researchers fail to agree on the meaning of well-being or how it should be studied. Aim: The first half of the thesis aims to examine the meaning, measurement and theory of well-being. The second half of the thesis aims to investigate the factors associated with subjective well-being (SWB), and the influence of attributes of well-being on preferences for the future. Methods: A systematic review was conducted to identify measures of well-being for use in adults (general population). The dimensions within these measures were organised into a framework using thematic analysis. Further, the theories underpinning these measures were identified and described. Fixed-effect regression models were used to study the factors important for SWB using data from a longitudinal (1996 – 2013) cohort of middle aged-older adults in the United States (n = 2049). Finally, preferences for life in the future were estimated in a sample of young ‘emergent adults’ (n =140) in the United Kingdom, using discrete choice experiments (DCEs). Results: The systematic review identified 99 measures of well-being, which included 196 distinct dimensions. These measures were influenced by a diverse range of theories (n = 98). Mental health, social integration and satisfaction with work had a significant impact on each of the SWB outcome variables (life satisfaction, positive affect and negative affect) in the fixed-effects analysis. The DCE indicated that stated preferences for life in the future among emergent adults were particularly driven by the prospect of social support from family and an aversion to experiencing mental health difficulties. Conclusion: This thesis has investigated inconsistencies in how well-being is understood, measured and studied. In response to this, a framework has been developed which organises the many measures available around key themes. Following on from the fixed-effects analysis and the DCE, future empirical research should be undertaken to investigate the interdependence of well-being and mental health.
1223

Photo-biomodulation of human skin fibroblast sub-populations : a systematic approach for the optimization of optical treatment parameters

Mignon, Charles January 2017 (has links)
The thesis presents a rational path for the optimization of the selection of optical treatment parameters in photobiomodulation of human skin fibroblasts. The project begins with an extensive analysis of 90 bibliographic reports in photobiomodulation published between 1985 and 2015, and revealed major inconsistencies in optical parameters selected for clinical applications. Seeking greater clarity for optimal parameter choice, a systematic approach to disentangle the multiple factors underpinning the response of human dermal fibroblasts in vitro to visible and near-infra red (NIR) light was employed. Light-based devices were constructed to specifically and systematically screen the optical parameter window (i.e. wavelength, irradiance and dose) observed in literature. Additionally, critical culture and treatment conditions that have dramatic impact on the outcome of specific light treatment of these human skin dermal cells were identified. In particular, environmental oxygen concentration, cell confluency and serum concentration were all found to have a great effect on the response of dermal fibroblasts to light. In parallel, the induction of reactive oxygen species (ROS) by short visible wavelengths on two dermal fibroblast sub-populations or lineage, reticular and papillary, was monitored by live-cell imaging. The ROS species were found to be created in or close to mitochondria. Lastly, gene expression studies revealed a strong impact of short visible wavelengths, as compared to long and NIR wavelengths on both subpopulations of human dermal fibroblasts. In particular, blue light (450 nm) specifically down-regulated proliferation, metabolism and protein synthesis molecular pathways. At the protein level, 450-nm light inhibited the production of procollagen I in human reticular and papillary fibroblasts in a dose-dependent manner. Gene expression results were in agreement i.e., the same light parameter down-regulated collagen fiber genes, integrins and up-regulated collagenase MMP1. This thesis concludes with a chapter presenting a characterization of the accuracy of a potential translation tool for the prediction of optical photon density inside human skin.
1224

Vibration transmission through structural connections in beams

Ishak, Saiddi A. F. bin Mohamed January 2018 (has links)
Analysis of vibration transmission and reflection in beam-like engineering structures requires better predictive models to optimise structural behaviour further. Numerous studies have used flexural and longitudinal structural wave motion to model the vibrational response of angled junctions in beam-like structures, to better understand the transmission and reflection properties. This study considers a model of a variable joint angle which joins two semi-infinite rectangular cross-section beams. In a novel approach, the model allows for the joint to expand in size as the angle between the two beams is increased. The material, geometric and dynamics properties were consistently being considered. Thus, making the model a good representation of a wide range of angles. Predicted results are compared to an existing model of a joint between two semi-infinite beams where the joint was modelled as a fixed inertia regardless of the angle between the beams, thus limiting its physical representation, especially at the extremes of angle (two beams lay next to each other at 180 degree joint). Results from experimentation were also compared to the modelling, which is in good agreement for the range of angles investigated. Optimum angles for minimum vibrational power transmission are identified in terms of the frequency of the incoming flexural or longitudinal wave. Extended analysis and effect of adding stiffness and damping (rubber material) at the joint are also reported.
1225

Coopérer à l’école, l’espoir d’une éducation par l’action collective : le cas d’un collège en région parisienne / Cooperative Learning at school : one example of a school in the Paris area

Baillon, Alexis 20 November 2015 (has links)
Cette thèse se propose d’évaluer les possibilités coopératives en classe de collège à partir d’une étude de terrain portant sur un établissement de région parisienne. Partant du constat que l’école française, et plus précisément le collège, ne parvient pas à organiser une action éducative efficace, nous posons l’hypothèse que c’est du fait d’un manque de structures coopératives de base dans la pratique de la classe. Pour répondre à cela, nous soutenons la thèse que la pratique de la classe est déjà imprégnée d’un idéal qui substitue à la forme scolaire traditionnelle, des pratiques polymorphes qui ont pour assises l’interaction et la communication, ce qui permet d’envisager une transformation des pratiques vers plus de coopération. Pour étayer celle-ci, nous avons étudié un établissement de région parisienne pendant plus de deux ans, ce qui nous amené à analyser le point de vue des enseignants par des entretiens semi-directifs, puis nous avons observé la dynamique entre enseignants et groupe d’élèves dans deux ateliers périscolaires se déroulant au sein de l’établissement. Pour pouvoir étudier de manière pertinente des pratiques coopératives nous avons construit le concept de coopération à partir des écrits de John Dewey que nous confrontons à la forme scolaire française tout au long de cette thèse. / This thesis intends to assess the cooperative possibilities in middle school class from a field study on a school in the Paris region. Considering that the French school, specifically middle school, does not manage to organize an effective educational action, we hypothesize that it comes from a lack of basic cooperative structures in classroom practice. To answer this issue, we support the thesis that classroom practice is already impregnated with an ideal that substitutes polymorphic practices to the traditional school form. These practices rely on communication and interaction, this is why it allows us to consider a transformation towards more cooperation. To support this view, we studied a school in the Paris region for over two years, which led us to analyze the teachers’ point of view through semi-directive interviews. We then observed the dynamic between a teacher and a group of students in two extra-curricular workshops being held within the school. To be able to study in a relevant way these cooperative practices, we have built the cooperation concept from the writings of John Dewey which we confront with the French school form throughout this thesis.
1226

Social Preferences and Voting on Reform: An Experimental Study

Paetzel, Fabian, Sausgruber, Rupert, Traub, Stefan 05 April 2014 (has links) (PDF)
Debating over efficiency-enhancing but inequality-increasing reforms accounts for the routine business of democratic institutions. Fernandez and Rodrik (1991) hold that anti-reform bias can be attributed to individual-specific uncertainty regarding the distribution of gains and losses resulting from a reform. In this paper, we experimentally demonstrate that anti-reform bias arising from uncertainty is mitigated by social preferences. We show that, paradoxically, many who stand to lose from reforms vote in favor because they value efficiency, while many who will potentially gain from reforms oppose them due to inequality aversion.
1227

Estudo de transistores a base de óxido de zinco visando aplicações em sensor de radiação ultravioleta / Investigation of zinc oxide transistors for applications in ultraviolet sensors

Gomes, Tiago Carneiro 27 March 2018 (has links)
Submitted by Tiago Carneiro Gomes (tiagogomes.prof@gmail.com) on 2018-06-30T16:46:33Z No. of bitstreams: 1 Gomes_T_C_tese_de_Doutorado.pdf: 5694002 bytes, checksum: 22bc5318ec502694cd7a4a087cec549f (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-07-02T19:06:37Z (GMT) No. of bitstreams: 1 gomes_tc_dr_bauru.pdf: 5485212 bytes, checksum: 22c574afd417cd26b3380c78e8274909 (MD5) / Made available in DSpace on 2018-07-02T19:06:37Z (GMT). No. of bitstreams: 1 gomes_tc_dr_bauru.pdf: 5485212 bytes, checksum: 22c574afd417cd26b3380c78e8274909 (MD5) Previous issue date: 2018-03-27 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Transistores de filme fino de ZnO, cujo desempenho depende das condições de preparação da camada de ZnO e do dielétrico de gate, tem sido aplicados como sensores de radiação ultravioleta (UV), visando prevenir danos à saúde da pele. Este trabalho tem como objetivo a fabricação de transistores de ZnO/Al2O3, mediante o estudo simultâneo dos parâmetros relacionados à preparação das camadas de ZnO e Al2O3, bem como, o de transistores com dielétrico padrão (ZnO/SiO2) submetidos a diferentes condições de funcionamento. Estes estudos visam encontrar quais condições viabilizam as aplicações dos transistores como sensor UV. Os experimentos englobam a deposição de filmes de ZnO tanto por sputtering de um alvo de ZnO, quanto por spray pirolise de uma solução de acetato de zinco. O dielétrico SiO2 foi obtido comercialmente, enquanto que o Al2O3 foi crescido por anodização. Os transistores foram fabricados em diversas condições, as quais foram estabelecidas pelos métodos de planejamento experimental Taguchi e Plackett-Burman. As respostas das caracterizações foram interpretadas por técnicas de estatística (ANOVA). Os resultados demonstram que Al2O3 otimizado exibe correntes de fuga de até 10E-10 A e constante dielétrica de ~13. A identificação dos parâmetros mais importantes na preparação de filmes de ZnO por spray pirólise, permitiram produzir transistores de ZnO/Al2O3 com mobilidades de ~4,5 cm2/Vs. Os sensores UV, usando transistores de ZnO/SiO2 apresentaram mobilidades de 0,1 a 12 cm2/Vs, e indicaram que a sensibilidade do sensor UV depende de parâmetros relacionados as condições de operação do dispositivo. Portanto, mostra-se que é fundamental a compreensão dos parâmetros envolvidos na produção dos dispositivos, pois isto permite refinar o processo na busca pela alta performance de dispositivos de baixo custo, bem como, otimizar os dispositivos para aplicações como sensor de radiação UV. / ZnO thin film transistors have been applied as ultraviolet (UV) radiation sensors in order to prevent damage to skin's health. However, the performance of ZnO transistor depends on the preparation conditions of both ZnO layer and gate dielectric. This work aims to produce and evaluate ZnO/Al2O3 transistors by studying simultaneously the parameters regarding the preparation of ZnO and Al2O3 layers, as well as the fabrication of ZnO transistors with a standard dielectric (ZnO/SiO2), under different conditions of working. It is intended to investigate the conditions to apply ZnO transistors as UV sensor. The experiments involve the deposition of ZnO films by sputter coating and spray pyrolysis of a solution of zinc acetate. SiO2 dielectric was commercially purchased, while Al2O3 was grown by anodization. The transistors were fabricated under different conditions, which were established by both experimental design Taguchi and Plackett-Burman methods. The responses from the characterization were interpreted by statistical techniques (ANOVA). The results showed that optimized Al2O3 films exhibit leakage current until 10E-10 A and dielectric constant of ~13. It was essential to identify the most important parameters regarding to preparation of ZnO films by pyrolysis spray in order to fabricate ZnO/Al2O3 transistors with mobilities of ~4,5 cm2/Vs. UV sensors based on ZnO/SiO2 transistors showed mobilities from 0,1 to 12 cm2/Vs and demonstrated that the sensitivity of the UV sensor depends on parameters related to working conditions. Therefore, it is of great importance the understanding of the parameters involved in the production of the devices, as it allows to refine the process in the search for the high performance of low cost materials as well as optimize the device for application as UV sensor. / FAPESP: 2014/13904-8
1228

Considerações sobre os aspectos cinemáticos e dinâmicos do movimento /

Cunha, Ailson Vasconcelos da. January 2008 (has links)
Orientador: Lizete Maria Orquiza de Carvalho / Banca: Roberto Nardi / Banca: João Zanetic / Resumo: É corrente entre os pesquisadores a necessidade de inserção de História. Filosofia e Sociologia da Ciência no ensino de ciências, assim como esta inserção é recorrentemente apontada como uma solução para a suposta crise que invadiu o ensino nesta modalidade. Insatisfeitos com o rumo que estas pesquisas estão tomando, delineamos nosso problema de pesquisa. Explicitamos nossa concepção de educação embasada principalmente pela obra do educador Paulo Freire, ou seja, apresentamos nossa concepção de educação dialógica-problematizadora na vertente emancipadora. Fazemos uma aproximação entre a concepção freiriana de educação e o ensino de ciências, a fim de estabelecer uma concepção de ensino de ciências, bem como do ensino de física do qual compartilhamos. Nessa concepção de ensino de ciências apresentamos a finalidade pela qual pretendemos resgatar a História, Filosofia e Sociologia da Ciência, HFSC, argumentando em favor de sua inseparabilidade com a Ciência no ensino de ciências. Apresentamos a Experiência do Balde de Newton e a finalidade que a mesma teria nessa concepção. Concluímos que a construção de enunciados sobre a experiência dp Balde de Newton, através de seus consequentes pronunciamentos e sua volta problematizada ao sujeito, proporcionou aos alunos uma transformação da realidade / Abstract: It is a common practi ce among researches the need of entering into History, Philosophy and Sociology of Science in science teaching, and this integration is repeatedly cited as a solution to the supposed crisis that broke into the school championship. Unhappy with the way these survey are taking, we delicated our research problem. We explicited our conception of education based mainly on the work of eductor Paulo Freire, that is, we present our vision of dialogic-problematizing education in the shed for liberation. We make a connection between the desing Freirien education and science education in order to establish a conception of science teaching and the teaching of physics which we share. In this conception of science education we present the purpose we intend redeem the History, Philosophy and Sociology of Science, HFSC, arguing for the inseparability of Science in science education. We present the experience of Newton's bucket and the the purpose that it would have this view. We conclude that the construction of statements about the experience of Newton's bucket through this consequent pronouncements and his return problematized to the subject gave the pupils a changing reality / Mestre
1229

Analysis of Ni and Fe-based Alloys for Turbine Seal Ring Applications

She, Dawei 20 March 2018 (has links)
Metal sealing rings have been used widely in compressors, turbines and hydraulic devices. Such rings can extend out due to elasticity, and keep close contact with the valve wall, resulting in the formation of a functional seal under pressure. In this project, the failure of metal sealing rings is considered. Sealing component failure due to stress relaxation can threaten the safety of the whole steam turbine. The object of this study was to examine the stress relaxation response and corresponding changes in microstructure of metal sealing rings used in nuclear steam turbine under high temperature and applied stress. The two kinds of sealing ring samples were selected for GH4145 and GH2132. In this paper, all samples were tested by accelerated simulation experiment. The test temperature was controlled at 400℃, 600℃, and 800℃. The 400℃ experiments lasted for 10, 20, 30 and 40 hours, while the 600℃ and 800℃ experiments lasted for 5, 10, 15 and 20 hours. The surface morphology was observed by metallographic analysis. It was found that the two kinds of sealing ring samples presented with a continuous development of grain coarsening and a decrease of the twins when time and test temperature were increased. The prolongation of time and increase of test temperature will drive the grain coarsening and reduce the twins faster. Many precipitates and inclusions were observed on the surface. The composition of precipitation was examined by scanning electron microscopy (SEM). It was further studied by testing samples with applied stress. The differences between the two tests and their influence on mechanical properties are discussed. The grain coarsening and twinning in the alloy will reduce the stress relaxation resistance of the material. Additionally, the precipitates and inclusions in the alloy may adversely affect the stress relaxation performance. Sealing rings using the nickel-based superalloys have stronger anti-stress relaxation performance than sealing rings made of iron-based superalloys.
1230

Prédiction de la fracture osseuse du col du fémur : modélisation par éléments finis basée sur la mécanique d’endommagement et validation expérimentale / prediction of proximal femur fracture : finite element modeling based on mechanical damage and experimental validation

Bettamer, Awad 22 November 2013 (has links)
Les fractures causées par l'ostéoporose de l’extrémité supérieure du fémur sont devenues un problème majeur de santé publique. Par conséquent, ce sujet devient un axe de recherche de plus en plus important pour les cliniciens et les chercheurs biomédicaux. Le but de cette étude est de développer une nouvelle approche pour prédire la fracture du col du fémur. Cette étude propose de développer et valider des modèles par éléments finis (EF) en 2D et 3D, basés sur le concept de l’endommagement mécanique des milieux continus, permettant de simuler la fracture de la partie proximale du fémur en tenant compte de l’initiation progressive de fissures et leur progression. Deux configurations ont été utilisées: appui monopodal et chute. L’ensemble des lois de comportements quasi fragile couplées à une loi d’endommagement sont implémentées en langage FORTRAN dans ABAQUS/Standard (sous-programme de type UMAT). La densité minérale osseuse (BMD) a été mesurée par l’absorptiométrie à rayon X en double énergie DXA pour la région d'intérêt. Les modèles ont été développés dans deux variantes (l’une isotrope et l’autre orthotrope) puis validés avec des résultats expérimentaux obtenus sur des essais en appui monopodale réalisés sur des fémurs humain. Durant ces essais, des mesures optiques basées sur la méthode de corrélation d'images numériques (DIC) ont été réalisées afin d’acquérir les différents champs de déplacement et de déformation. Le modèle numérique 3D a réussi à prédire l’ensemble de la courbe force-déplacement ainsi que l'emplacement et l'amorce de la rupture des fémurs. Par ailleurs, Malgré sa robustesse, la variante 3D du modèle numérique reste difficilement exploitable dans l’état pour réaliser un diagnostic préventif dans des délais acceptables pour des cliniciens, car très consommatrice en temps de calcul. Pour pallier à cela, le modèle simplifié en 2D a été préliminairement validé sous les mêmes conditions aux limites et les résultats ont montré une bonne corrélation avec l’expérience. Ces travaux ont souligné le potentiel de la modélisation par éléments finis basée sur l’endommagement quasi-fragile à devenir un outil complémentaire de prédiction du risque de la fracture osseuse. / Femoral fractures caused by the osteoporosis become major problem of public health, and therefore, this subject becomes an increasingly important goal for both clinicians and biomedical researchers. The purpose of this study is to develop a new coupled approach to predict the fracture of neck femoral. The current study proposes a validated 2D and 3D finite element (FE) models based on continuum damage mechanics in order to simulate human proximal femur fracture considering the progressive cracks initiation and propagation. These models are applied and validated under single limb stance and sideways fall configuration. Quasi brittle behavior laws coupled to damage are implemented in FORTRAN and fed into ABAQUS/Standard codes to describe the constitutive behavior (subroutine UMAT). Bone mineral density (BMD) is measured using dual energy X-ray absorptiometry (DXA) for the region of interest. The models have been developed within two variants (one isotropic, the other anisotropic) and validated with experimental results of tests performed on human femur samples under single limb stance configuration. During these tests, optical measurements based on the method of digital image correlation (DIC) were conducted to acquire the various fields of displacement and deformation. To calculate the fracture risk of the femoral head, it is necessary to assign correctly the bone material properties. The 3D FE models were able to predict the overall force-displacement curve, location and initiation of femur fractures. Moreover, despite its robustness, this 3D FE model is still limited to be used, within clinically acceptable time, for diagnostic purposes. To overcome this, the model was simplified into 2D model which has been preliminarily validated under identical boundary conditions and the results showed a good correlation with experiments. These studies have highlighted the potential of the finite element model based on quasi-brittle damage to become a complementary tool for predicting the risk of bone fracture.

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