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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.
51

Développement de méthodologies d'Eco-conception pour le secteur microélectronique / Eco-design methodology for microelectronic products

Villard, Aurélie 21 December 2012 (has links)
L'éco-conception est un processus permettant aux entreprises industrielles d'assumer leur responsabilité relative aux impacts générés par leurs produits. Les contraintes liées aux impacts environnementaux sont intégrées dans les stades avancés de la conception. Du fait de ses spécificités, tant au niveau de la structure du produit que de la complexité des processus de conception, l'industrie microélectronique s'est trouvée jusqu'alors en marge de considérations avancées sur l'impact de ses produits. L'objectif du travail de recherche est de définir une méthodologie d'éco-conception dédiée à la microélectronique permettant d'identifier les méthodes, outils et indicateurs susceptibles d'être déployés dans les départements de R&D. La stratégie associée vise à accroître la sensibilité environnementale des concepteurs et à les conduire à trouver des alternatives influant positivement sur l'environnement. Notre méthodologie repose sur une plateforme méthodologique intégrant plusieurs outils, chacun dédié à une activité indépendante de la conception de produits microélectroniques. L'évaluation environnementale est basée sur l'analyse de cycle de vie (ACV). Dans les phases préliminaires de conception, la connaissance du produit (structure, propriétés et performances) est limitée, alors la modélisation de son cycle de vie est réalisée à l'aide « d'ACV-simplifiée » : cela consiste à prédire l'impact d'un produit en développement grâce à des mécanismes d'adaptation par analogie basés sur l'étude des générations précédentes. En plus de solutions techniques appropriées, l'intégration de l'éco-conception dans une entreprise nécessite certains changements organisationnels : une modification du processus de conception a été proposée ainsi que des recommandations pour l'intégration d'un système de gestion de l'environnement orienté sur les produits. / Eco-design represents a natural process for industries wishing to fulfil their role in safeguarding environment and resources. The constraint linked to impacts becomes a decisive factor which can be systematically integrated in the early stages of products development. Because of chips specificities, both in structure and complexity of design process, microelectronic industry has been up to now out of advanced considerations related to chips environnemental performances. Our target was to define an eco-design methodology dedicated to microelectronic sector including the identification of methods, tools and indicators which have the highest chance to be deployed in R&D departments. The strategy aims to increase designers' environmental consciousness and drive them to explore innovative opportunities that can positively impact the environment during design phase. Our methodology relies on a platform integrating three tools, each one of them dedicated to a part of chip design. Environmental analysis is based on Life Cycle Assessment (LCA). In the preliminary stages of design, knowledge on product (structure, properties and performances) is limited so the evaluation is assessed using “Quick LCA”: it consists in predicting the environmental footprint of an under-development product thanks to adaptive mechanism based on the evaluation of previous generations. In addition to technical solutions, an optimized integration of an innovative process such as eco-design requires organizational changes into the company: a proposal for internal design process modification was done including recommendations for integration of a product-oriented management system.
52

Evolution of Choral Sound: In Professional Choirs from the 1970s to the Twenty-First Century

January 2013 (has links)
abstract: Imitation is the genesis of change. One basic principle of human nature is that people imitate what they see and hear. In the professional choral arena, musicians extend the high art of imitation through fine-tuning, and creative reinterpretation. Stimulated by this cycle, the color of the twenty-first-century professional choir shifted compared to that of professional choirs from the 1950s through 1970s, causing an evolution in choral sound. In a series of interviews with iconic composers and conductors of professional choirs, the subjects involved in the study conveyed comprehensive and personal accounts outlining how professional choirs have refined the standard of choral sound. The paper is organized into three sections: (1) where have we been, (2) where are we now and (3) where are we going? It explores various conductors' perceptions of how and why choirs are unique when compared to earlier generations and what they believe caused the shift in choral tone. Paired with this perspective is the role of modern composers, whose progressive compositional techniques helped shape the modern choral sound. The subjects involved in the study further theorize how current inclinations may potentially shape the future of professional choral music. Although the subjects expressed differing opinions about the quality of the twenty-first-century choral tone, many agree that there have been specific transformations since the 1970s. The shift in choral tone occurred due to developments in vocal technique, exploration of contemporary compositional extended techniques, an adherence to historically informed performance practice, imitation of vocal colors from numerous cultures, incorporation of technology and emulation of sound perceived on recordings. Additionally, choral music subtly became prominent in film scores, and innovative conductors created progressive concert programming, and developed novel approaches to entertain audiences. Samplings of contributors involved in this study include: John Rutter, Harry Christophers, Charles Bruffy, Nigel Short, Craig Hella Johnson, Alice Parker, Michael McGlynn, Phillip Brunelle, Craig Jessop, Libby Larsen, Ola Gjeilo, Cecilia McDowall, Jaakko Mäntyjärvi and Stephen Paulus. / Dissertation/Thesis / D.M.A. Music 2013
53

Mecanismos de relaxação spin-nuclear-rede em CaF2:U3+. / Nuclear-spin-lattice relaxation mechanics for CaF2:U3+.

José Renato Jurkevicz Delben 20 October 1983 (has links)
Neste trabalho descreve-se a construção de dois equipamentos controladores da temperatura da amostra, que operam entre 77K e 300K e entre 300K e 700K. Apresenta-se os resultados de medidas de T1 e T2, no intervalo de 77K e 700K, realizadas com o campo estático Ho paralelo à direção [111] e uma radiofreqüência de 24MHz. Discutem-se os comportamentos de T1 e T2 neste intervalo de temperaturas e os possíveis mecanismos de relaxação, spin nu clear-rede e spin eletrônico de impureza-rede, atuantes. / In this work we describe the construction of two sample temperature controlled equipments that operate between 77K and 300K and between 300K and 700K. We show the results of T1 and T2 measurements over the temperature range of 77K to 700K with the static field Ho parallel to [111] direction and 24MHz. We discuss the T1 and T2 behavior in this range temperature and the possible relaxation mechanisms of spin nuclear and spin electronic of impurity to lattice that are present.
54

Doping Behavior of Cations in Perovskite-type Oxide Materials for Protonic Ceramic Fuel Cells / プロトン伝導セラミック型燃料電池に用いるペロブスカイト型酸化物材料における陽イオンのドーピング挙動

Han, Donglin 26 September 2011 (has links)
Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16396号 / 工博第3477号 / 新制||工||1525(附属図書館) / 29027 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 乾 晴行, 准教授 宇田 哲也 / 学位規則第4条第1項該当
55

Gas diffusion electrodes for high temperature polymer electrolyte membrane fuel cells membrane electrode assemblies

Barron, Olivia January 2014 (has links)
Philosophiae Doctor - PhD / The need for simplified polymer electrolyte membrane fuel cell (PEMFCs) systems, which do not require extensive fuel processing, has led to increased study in the field of high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) applications. Although these HT-PEMFCs can operate with less complex systems, they are not without their own challenges; challenges which are introduced due to their higher operation temperature. This study aims to address two of the main challenges associated with HT-PEMFCs; the need for alternative catalyst layer (CL) ionomers and the prevention of excess phosphoric acid (PA) leaching into the CL. The first part of the study involves the evaluation of suitable proton conducting materials for use in the CL of high temperature membrane electrode assemblies (HT-MEAs), with the final part of the study focusing on development of a novel MEA architecture comprising an acid controlling region. The feasibility of the materials in HT-MEAs was evaluated by comparison to standard MEA configurations.
56

Ageing of overhead conductors

Enegela, Odagboyi January 2013 (has links)
Overhead conductors used in the transmission of power in grids around the world are generally subjected to ageing, which is the time-based change of their properties. Important properties such as corona discharge, audible noise, hydrophobicity and corrosion are usually considered and investigated. On some conductors such as the aluminium conductor steel reinforced (ACSR), a reduction in audible noise over exposure time to the service environment has been noted to occur. However, the converse has been observed for the gap-type thermal resistant aluminium conductor steel reinforced (GTACSR or “Matthew” conductor), although this conductor is preferred due to its high ampacity. The relationship between conductor hydrophobicity, audible noise, surface contamination and roughness, wettability and corrosion were investigated using All Aluminium Alloy Conductor (AAAC), Aluminium Conductor Composite Core (ACCC) and GTACSR samples. Findings from Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectric Spectroscopy (XPS) and contact angle measurements revealed that carbon, hydrocarbon and silicone contamination was responsible for the hydrophobic nature of the surface. Furthermore, electrochemical investigations and electron microscopy showed that pitting or/and crevice corrosion were the predominant corrosion mechanisms on these conductors. Exposure to simulated industrial and marine environments further confirmed this finding and also showed that general corrosion also occurs on relatively uncontaminated conductors, thereby changing their surface roughness, as seen from the White Light Interferometry results. Corrosion was observed to be accelerated by the presence of surface contaminants such as oils and carbon, as these facilitated water (droplet) retention by reducing the conductor’s surface energy. Reduction/elimination of surface contamination/hydrophobicity were the desired solutions to the problem, and this was achieved by grit blasting. Partial/complete oxidation of the silicones resulted in the reduction/elimination of sample hydrophobicity – this was seen from more contact angles measurements and XPS data. Grit blasting also restored conductor cleanliness and roughened the surface sufficiently to produce surface run-off.
57

Estudo por Ressonância Magnética Nuclear do Condutor Protônico HPb2Nb3O10. nH2O. / Nuclear magnetic resonance study of proton conductor HPb2Nb3O10. nH2O.

Caio Eduardo de Campos Tambelli 18 September 1998 (has links)
Neste trabalho foi estudado o condutor protônico HPb2Nb3O10. nH2O , por Ressonância Magnética Nuclear pulsada do próton \'ANTPOT.1H\'. Tanto o estudo da forma de linha como a relaxação spin-rede, em função da temperatura, refletem a mobilidade das espécies protônicas neste material. O início dos movimentos iônicos e moleculares produzem um forte estreitamento da largura de linha acima de 130 K. Os dados da taxa de relaxação spin-rede (1/T1) mostra um máximo entre 253 K e 273 K que depende da hidratação (n). As energias de ativação obtidas dos resultados de relaxação e largura de linha variam entre 0,14eV e 0,4eV, dependendo da hidratação. Os resultados de condutividade e RMN são consistente com um mecanismo de condução do tipo Grotthus, que consiste numa sucessão de movimentos reorientacionais e saltos de prótons. O coeficiente de difusão protônica foi estimado dos parâmetros obtidos de RMN sendo da ordem de 10-8 cm2/s. Este valor leva a uma condutividade da ordem de 10-3 S/ cm. / The protonic conductor HPb2Nb3O10. nH2O , was studied by pulsed Nuclear Magnetic Resonance (NMR) of \'ANTPOT.1H\'. The temperature dependence of the spin-lattice relaxation rate (1/\'T IND.1\') and line width, reflect the mobility of the protonic species present in this material. The onset of ionic and molecular motions produces a strong narrowing of the line at temperatures above 130 K. The spin-lattice relaxation data, obtained above 200 K, shows a maximum in 1/\'T IND.1\', peaking in the range 253 K to 273 K, depending on the value of n. Activation energies of protonic motions, measured from line width and relaxation data, are n dependent and lies in the range of 0,14 eV to 0,4 eV. Results of NMR and conductivity are consistent with the Grotthus conduction mechanism, consisting of a succession of molecular re-orientations and proton jumps. The protonic diffusion coefficient was estimated from the parameters obtained from NMR relaxation and found to be of the order of 10-8 cm2/s, leading to a conductivity of about 10-3 S/ cm.
58

A Three-Dimensional Anatomically Accurate Finite Element Model for Nerve Fiber Activation Simulation Coupling

Fischer, Shain Ann 01 March 2015 (has links)
Improved knowledge of human nerve function and recruitment would enable innovation in the Biomedical Engineering field. Better understanding holds the potential for greater integration between devices and the nervous system as well as the ability to develop therapeutic devices to treat conditions affecting the nervous system. This work presents a three-dimensional volume conductor model of the human arm for coupling with code describing nerve membrane characteristics. The model utilizes an inhomogeneous medium composed of bone, muscle, skin, nerve, artery, and vein. Dielectric properties of each tissue were collected from the literature and applied to corresponding material subdomains. Both a fully anatomical version and a simplified version are presented. The computational model for this study was developed in COMSOL and formatted to be coupled with SPICE netlist code. Limitations to this model due to computational power as well as future work are discussed. The final model incorporated both anatomically correct geometries and simplified geometries to enhance computational power. A stationary study was performed implementing a boundary current source through the surface of a conventionally placed electrode. Results from the volume conductor study are presented and validated through previous studies.
59

Paucity of Female College Band Directors as Faculty and Conductors at National Conferences in the United States, 2017–2018

January 2020 (has links)
abstract: Research indicates that women hold far fewer positions as collegiate band directors than do their male counterparts; however, since the 1993–1994 academic year, there have been no updated statistics describing the sex ratio of women who are college band directors. As the wind band profession is putting more effort into diversity initiatives and women are becoming more accepted as conductors, an examination of current sex (female and male) representation of band directors seemed timely and necessary. The purpose of this study was to provide updated data. Using the College Music Society Directory of Music Faculties in Colleges and Universities, U.S. and Canada 2017–2018, the author of the present study looked at the sex of college band directors listed and discovered that only 11.3 percent of all college band director positions in the United States were held by women. Furthermore, only 13.4 percent of bands selected to perform at the Midwest Clinic were led by women in the ten occurrences of the conference between 2009 and 2018, and only 5.3 percent of bands selected to perform at the Collegiate Band Directors National Association at the fourteen national conferences held between 1993 and 2019 had women as their head conductors. Clearly, sex parity does not yet exist among university band directors. With the publication of more current percentages of the representation of women as band directors that this study provides, research investigating why this phenomenon continues and advocacy to change the status quo is highly recommended. / Dissertation/Thesis / Doctoral Dissertation Music 2020
60

Investigating potential proton conductors: Doping BaTiO3 and SrTiO3 with Fe and Al / Undersökning av potentiella protonledare genom dopning av BaTiO3 och SrTiO3 med Fe och Al

Löfstrand, Julia January 2020 (has links)
There are many interesting applications of proton conducting oxides, such as electrolytes in fuel cells, hydrogen sensors and catalytic membranes for hydrogenation or dehydrogenation of organic compounds. Previous work explored doping BaTiO3 with the Rare Earth Element (REE) Sc to introduce oxygen vacancies in the structure, making it a Proton Conductor (PC). PC oxides are often perovskite materials, ABX3, wherethe A- or B-site are doped in such a way that less oxygen can be contained, creating oxygen vacancies. When these materials are then hydrated so that water molecules occupy the vacancies, hydrogen is essentially added to the system in the form of protons. This study expanded on those results, exploring possible dopants that are non-REEs, theoretically improving availability and cost. Fe and Al were chosen as B-site dopants and Sr was included as an alternative to Ba as the A-site cation, compensating for the smaller size of the Fe- and Al atoms compared to Ti. Solid state synthesis was used to manufacture the different compounds and then X-Ray Diffraction (XRD), ThermoGravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) were used inorder to investigate their properties. The main focus was to explore ift he materials could be synthesised using this method, their structures and how they reacted to hydration. All Al doped samples could not be made phase pure with the synthesis parameters used. BaTi0.5Fe0.5Oy was stabilised by the inclusion of Ti, as it did not decompose during hydration, unlike pure BaFeOx. Significant hydration was achieved in a wet nitrogen atmosphere at 185°C, but its structure type was hexagonal, which is known to be unfavourable for proton conduction. SrTi0.5Fe0.5Oy had a cubic structure which is a beneficial structural trait for proton conduction, but negligible hydration was observed by TGA. A small increase in cell volume indicates that it might still have taken up some water, but the methods used for hydration were not optimal for this material. The oxygen content of the materials was not determined in this project and methods such as Mössbauer spectroscopy and iodometric titration should be included in any related future studies.

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