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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.
1

Particulate Phosphorus Input and Burial Efficiency in the Gaoping Coastal Sea

Yeh, Yu-ching 30 August 2009 (has links)
The purposes of this study are to investigate the sources, distributions, fluxes and phosphorus burial efficiency (PBE) of particulate phosphorus in the Gaoping (GP) coastal sea. The GP River carried about 3.14 ¡Ñ 104 ton yr-1 (1.03 ¡Ñ 109 mol yr-1) particulate P into the GP coastal sea. The total P flux was primarily determined by the river runoff during the May-yu (monsoon) and typhoon seasons. The river P was approximately consisted of 90.8% particulate inorganic-P (PIP), 7.4% particulate organic-P (POP), 1.5% dissolved inorganic-P (DIP) and 0.3% dissolved organic-P (DOP). The particulate-P existed mainly in 10-63 £gm particles. In the GP costal sea, particulate P in surface sediments was found to be 80-90% as PIP and 10-20% as POP. The highest distribution of PIP was located on the flanks of GP Canyon at the upper slope (200-600 m) region. This distribution may be caused by plumes of river sediments or turbidity currents overflowing the canyon. The sedimentation rates of sediments ranged from 0.032 to 1.62 g cm-2 yr-1 in the GP coastal sea and the highest rates were also located on both sides of the GP Canyon. The burial fluxes of total phosphorus (TP) ranged from 0.02 to 0.84 g cm-2 yr-1, consisted approximately by 88% PIP and 12% POP. The burial fluxes of this study area were generally similar to those in other continental margins (Bohai Sea, Yellow Sea, Mississippi Delta). The total depositions of sediment and TP were approximately 6.6 ¡Ñ 106 ton yr-1 and 4227 ton yr-1, respectively, in the study area. The burial TP was equivalent to 0.06% of deposited sediments. The buried TP can be proportionate approximately into 15% in the continental shelf (< 200 m), 69% in the continental slope (200-1000 m), and 16% in the slope basin (> 1000 m). The continental shelf (<200 m) region was apparently influenced by wave and tidal processes and prevented from sediment accumulation. The burial efficiency of TP (PBE) in the GP costal sea is estimated accordingly to PBE (%) = 100 ¡Ñ PBF / (PBF+JP), where PBF is the burial flux of TP and JP is the diffusion flux of TP from porewater. The PBE decreases with the depth of sampling location and the maximum PBE locates on the station of southern canyon (779-1), the station of northern canyon (791-L18) and the station within the canyon (732-38). The PBE(s) are similar to those found in the Nazar&#x00E9; Canyon, showing a high PBE in coastal and/or canyon regions. The budget model shows that the major sources of particulate-P are derived from the GP River and the net ecosystem production (NEP) from the euphotic zone of study area. The annual river load and NEP input to the study area are 1.03 ¡Ñ 109 mol P yr-1 and 1.5 ¡Ñ 108 mol P yr-1, respectively. However, annual TP accumulation in the GP costal sea is just 1.48 ¡Ñ 108 mol P yr-1, corresponding to 12.5% of river load and NEP input. In addition, about 80% of GP River loads do not deposit into GP sediments and may be exported out of the study area.
2

Hybrid functional calculations of a Te antisite in bulk CdTe

Árdal, Kristinn Björgvin January 2013 (has links)
The detection of gamma-rays is an important issue in a cast array ofindustries. CdTe is a semiconductor used for gamma-ray detectors whichcan operate at high temperatures. Density functional theory calculationsof the electronic structure within the Perdew-Burke-Ernzerhof exchange-correlation functional underestimate the bandgap of CdTe: the calculatedbandgap within PBE is less than half the experimental value. The useof a hybrid functional approach to exchange and correlation describes thebandgap correctly. The goal of this project was to nd out if PBE calcu-lations give an adequate description of defects in CdTe by comparing it tohybrid functional calculations. We show that PBE is adequate in describ-ing Te antisite defects in CdTe if a correction to the bandgap is applied.The defect level for both PBE and hybrid functional was calculated to be0.24 eV above the valance band.
3

Étude de l’ionisation et de la fragmentation de bases de l’ADN-ARN par la théorie de la fonctionnelle de la densité / Ionization and fragmentation of DNA-RNA bases : a density functional theory study

Sadr-Arani, Leila 13 May 2014 (has links)
Les rayonnements ionisants (RI) traversent les tissus humains, y déposent de l'énergie et la dissipent en fragmentant des molécules. Les fragments obtenus peuvent être mis en évidence par spectrométrie de masse. Malgré la quantité d'informations obtenue expérimentalement à partir du spectre de masse, l'expérience seule ne peut pas répondre à toutes les questions concernant les mécanismes de fragmentation des bases de l'ADN/ARN, et l'étude issue des méthodes quantiques est un complément précieux à ces informations. L'étude théorique permet de connaître les liaisons moléculaires rendues faibles dans chaque base par ionisation et ainsi de prévoir les mécanismes de fragmentation et les fragments produits. Le but de ce travail est d'étudier l'ionisation et les mécanismes de fragmentation de bases de l'ADN/ARN (Uracile, Cytosine, Adénine et Guanine) et d'identifier les cations correspondants à chaque pic des spectres de masse. Nous avons effectué nos calculs en utilisant la DFT avec la fonctionnelle PBE. Dans cette thèse, pour toutes les bases d'ARN, la réaction de rétro Diels-Alder est une des voies principales de dissociation (élimination de HNCO ou de NCO•) à l'exception de l'adénine qui n'a pas d'atome d'oxygène. La perte d'une molécule NH3 (NH2•) est aussi un chemin commun à toutes les bases contenant un ou plusieurs groupes amine. Egalement, la possibilité de la perte d'un hydrogène à partir des cations est également envisagée, ainsi que la dissociation de ces cations déshydrogénés et des bases protonées, en se limitant à l'uracile. Ce travail montre tout l'intérêt de l'apport de calcul (DFT) à l'interprétation des spectres de masse de bases de l'ADN / Ionizing radiation (IR) cross human tissue, deposit energy and dissipate fragmenting molecules. The resulting fragments may be highlighted by mass spectrometry. Despite the amount of information obtained experimentally by the interpretation of the mass spectrum, experience alone cannot answer all the questions of the mechanism of fragmentation of DNA/RNA bases and a theoretical study is a complement to this information. A theoretical study allows us to know the weakest bonds in the molecule during ionization and thus may help to provide mechanisms of dissociation and produced fragments. The purpose of this work, using the DFT with the PBE functional, is to study the ionization and fragmentation mechanisms of DNA/RNA bases (Uracil, Cytosine, Adenine and Guanine) and to identify the cations corresponding to each peak in mass spectra. For all RNA bases, the retro Diels-Alder reaction (elimination of HNCO or NCO•) is a major route for dissociating, with the exception of adenine for which there is no atom oxygen in its structure. Loss of NH3 (NH2•) molecule is another common way to all bases that contain amine group. The possibility of the loss of hydrogen from the cations is also investigated, as well as the dissociation of dehydrogenated cations and protonated uracil. This work shows the interest of providing DFT calculation in the interpretation of mass spectra of DNA bases
4

Scale-up of Emulsion Polymerization Process : impact of changing characteristic times / Scale-up de la polymérisation en émulsion : l’influence du changement de temps caractéristiques

Ariafar, Solmaz 10 November 2016 (has links)
Un système consistant d'une simulation de mécanique des fluides numérique (MFN) couplée à un modèle de bilan de population (PBM) est développé afin d'étudier l'effet des paramètres variés sur la performance d'un procédé de polymérisation en émulsion qui conduit à la peoduction des particules de polymère dans un milieu aqueux continu.Comme une grande gamme des produits polymériques, des latexes sont les « produits par processus » (products-by-process), et leurs propriétés sont déterminés pendant la polymérisation. LA distribution de la taille des particules (PSD) est une des plus importants paramètres qui influence la qualité finale de latex. La modélisation d'évolution du PSD est généralement réalisée par l'addition un ensemble des PBEs au modèle cinétique. Le PBE fournit un moyen d'étudier la contribution des différents phénomènes dans l'évolution du PSD, comme la nucléation, la croissance des particules par la polymérisation, et la coagulation des particules à cause du mouvement brownien ou le mouvement du fluide (la coagulation Perikinetic et Orthokinetic, respectivement).Afin d'évaluer l'impact du mélange non homogène et les paramètres physiques du système sur l'évolution du PSD du latex, la simulation transitoire d'écoulement à été réalisé avec l'aide d'un progiciel commercial de MFN (Fluent® 15.0) pour munir dans chaque pas du temps, les concentrations locales des espèces ioniques (pour déterminer le taux de la coagulation Perikinetic modelé par le modèle de DLVO) ainsi que certains paramètres hydrodynamiques comme le taux de dissipation de la turbulence et le taux de cisaillement (afin de déterminer le taux de la coagulation Orthokinetic). Cette information est appliquée simultanément par le module complémentaire de PBM dans Fluent pour calculer le PSD pour le prochain pas du temps ; ainsi, un couplage complet entre le MFN et le PBM est assuré / A framework, consisting of a computational fluid dynamics (CFD) simulation model coupled to a population balance model (PBM) is developed to study the effect of various parameters on the performance of an emulsion polymerization process which leads to the production of a fine dispersion of polymer particles in a continuous aqueous medium.Like most polymer products, latexes are “products-by-process”, whose main properties are determined during polymerization. One of the main parameters influencing the final quality of the latexes is the particle size distribution (PSD). Modeling the evolution of PSD is usually accomplished through the addition of a set of PBEs to the kinetic model. PBE provides a means of considering the contribution of different phenomena in the PSD evolution, being nucleation, growth of polymer particles by polymerization, and coagulation of particles due to brownian or fluid motion (Perikinetic and Orthokinetic coagulation, respectively).To assess the impact of nonhomogeneous mixing and physical parameters of the system on the evolution of the latex PSD, the transient simulation of flow was performed with the aid of a commercial CFD Package (Fluent® 15.0) to provide in each time step, the local concentrations of ionic species (to determine the rate of perikinetic coagulation modeled by DLVO model) and certain hydrodynamic parameters such as turbulence dissipation rate and shear rate (to determine the rate of orthokinetic coagulation). This information is applied simultaneously by the PBE add-on module of Fluent to calculate the PSD for the next time step; thus a complete coupling between CFD and PBM is assured
5

Quantum-mechanical Ab-initio Calculations of the Properties of Wurtzite ZnO and its Native Oxygen Point Defects.

Lamichhane, Aneer 24 July 2018 (has links)
No description available.
6

Étude DFT+U des phases structurales du La2CuO4

Delaval-Lebel, Merlin 08 1900 (has links)
Ce mémoire traite des propriétés du La2CuO4 dopé en trous, le premier supraconducteur à haute température critique ayant été découvert. Les différentes phases électroniques du cristal y seront présentées, ainsi que le diagramme de phases en dopage de ce matériau. Les trois structures dans lesquelles on peut retrouver ce cristal seront décrites en détail, et leurs liens présumés avec les phases électroniques seront présentés. Il s’en suivra une étude utilisant la théorie de la fonctionnelle de la densité combinée au modèle de Hubbard (DFT+U) des différentes phases structurales, en plus des phases antiferromagnétiques et paramagnétiques. L’effet de la corrélation électronique sur la structure cristalline sera également étudié par l’intermédiaire du paramètre de Hubbard. Le but sera de vérifier si la DFT+U reproduit bien le diagramme de phases expérimentales, et sous quelles conditions. Une étude des effets de l’inclinaison des octaèdres d’oxygène sur la structure électronique sera également présentée. / Presented here is a study on the hole doped La2CuO4, the first discovered high-­‐Tc superconductor of the cuprate family. The different electronic phases of this crystal are briefly reviewed. The three crystal structures present in this material are described, and the link between those phases and the electronic structure are discussed. The relationship of those structural phases with the magnetic phases is investigated with the help of calculations based on the density functional theory where an additional Hubbard term has been added (DFT+U). With the help of the Hubbard parameter, the effect of the electronic correlation’s strength on the structural parameters of the crystal is also studied. The idea here is to verify how well the DFT+U is able to reproduce the experimental phase diagram of this material. The effect of the tilting of the oxygen octahedras on the electronic structure is also addressed.
7

Étude DFT+U des phases structurales du La2CuO4

Delaval-Lebel, Merlin 08 1900 (has links)
Ce mémoire traite des propriétés du La2CuO4 dopé en trous, le premier supraconducteur à haute température critique ayant été découvert. Les différentes phases électroniques du cristal y seront présentées, ainsi que le diagramme de phases en dopage de ce matériau. Les trois structures dans lesquelles on peut retrouver ce cristal seront décrites en détail, et leurs liens présumés avec les phases électroniques seront présentés. Il s’en suivra une étude utilisant la théorie de la fonctionnelle de la densité combinée au modèle de Hubbard (DFT+U) des différentes phases structurales, en plus des phases antiferromagnétiques et paramagnétiques. L’effet de la corrélation électronique sur la structure cristalline sera également étudié par l’intermédiaire du paramètre de Hubbard. Le but sera de vérifier si la DFT+U reproduit bien le diagramme de phases expérimentales, et sous quelles conditions. Une étude des effets de l’inclinaison des octaèdres d’oxygène sur la structure électronique sera également présentée. / Presented here is a study on the hole doped La2CuO4, the first discovered high-­‐Tc superconductor of the cuprate family. The different electronic phases of this crystal are briefly reviewed. The three crystal structures present in this material are described, and the link between those phases and the electronic structure are discussed. The relationship of those structural phases with the magnetic phases is investigated with the help of calculations based on the density functional theory where an additional Hubbard term has been added (DFT+U). With the help of the Hubbard parameter, the effect of the electronic correlation’s strength on the structural parameters of the crystal is also studied. The idea here is to verify how well the DFT+U is able to reproduce the experimental phase diagram of this material. The effect of the tilting of the oxygen octahedras on the electronic structure is also addressed.
8

Contribuições da prática (in)formada por evidências para a formação do professor de matemática: uma análise das ações dos professores a partir das suas próprias práticas

SILVA, Marcos Guilherme Moura 08 February 2014 (has links)
Submitted by Nathalya Silva (nathyjf033@gmail.com) on 2017-05-22T19:35:24Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ContribuicoesPraticaInformada.pdf: 1309909 bytes, checksum: 89c2131828eefdad140b52d851078e36 (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-05-31T12:30:40Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ContribuicoesPraticaInformada.pdf: 1309909 bytes, checksum: 89c2131828eefdad140b52d851078e36 (MD5) / Made available in DSpace on 2017-05-31T12:30:40Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ContribuicoesPraticaInformada.pdf: 1309909 bytes, checksum: 89c2131828eefdad140b52d851078e36 (MD5) Previous issue date: 2014-02-08 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O movimento rumo à Prática Baseada em Evidências é tão importante quanto polêmico. Sua ampla difusão na área médica e em campos afins figura no cenário educacional como uma discussão contemporânea. Considerando suas limitações e potencialidades, o presente estudo teve como objetivo investigar em que aspectos a Prática Baseada em Evidências (PBE) pode contribuir na formação profissional do professor de Matemática. Para tanto, trilhou-se os caminhos de uma pesquisa qualitativa, com informações constituídas a partir de entrevistas estruturadas, transcrições de áudio e vídeo e relatórios de estudo elaborados pelos nove sujeitos. Nossas análises referentes às contribuições da Prática Baseada em Evidências para a formação profissional do professor de Matemática se pautaram na Teoria da Aprendizagem Transformadora proposta por Jack Mezirow (2013) e nas considerações teóricas de Bosh e Gascon (2001). Os resultados apontam que a experiência formativa desenvolvida se constitui como alicerce de Aprendizagem Informacional e Transformacional, nos termos propostos por Mezirow, assim como oportuniza ao professor uma experiência auto formativa (aprender a aprender), desenvolvimento crítico sobre as questões relacionadas às práticas, aquisição de processos e ferramentas didáticas, inserção do inquérito para aquisição de conhecimentos, estreitamento do professor com a pesquisa sistematizada da Educação Matemática e desenvolvimento do professor pesquisador, desencadeando a construção de novas práticas. / The movement toward Evidence-Based Practice is as important as controversial. Circulated widely in the medical field and in related fields figure in educational setting such as a contemporary discussion. Considering their limitations and potentials, the present study aimed to investigate in what ways the Evidence-Based Practice (EBP) can contribute to the training of mathematics teachers. To this end, walked up the path of a qualitative research, with information recorded from structured interviews, audio transcripts and video reports produced by the nine study subjects. Our analyzes relating to the contributions of Evidence-Based Practice for the training of mathematics teachers were based on Transformative Learning Theory proposed by Jack Mezirow (2013 ) and theoretical considerations Bosh and Gascon (2001 ) .The results show that the developed training experience is constituted as a foundation of Informational and Transformational Learning , as proposed by Mezirow terms , as well as gives opportunity to the teacher a self learning experience ( learning to learn ) , on critical development issues related to practices, acquisition of processes and teaching tools , insertion of inquiry for acquiring knowledge , strengthening of teachers with systematic research and development of mathematics education research professor , triggering the construction of new practices.
9

Stability of monoatomic nanowires : a first-principles study / Ab initio studie av nanotrådars stabilitet

Gerhardsson, Andreas January 2011 (has links)
Monoatomic chain formation for Ag, Au, Pd and Pt has been investigated using a model for the tip structure. First-principles calculations, mostly spin polarized, were performed within the framework of the Density Functional theory. Results are presented and discussed on the basis of the electronic structure. Tendencies for chain formation were noted for Ag, Au and Pt.
10

Étude de l'ionisation et de la fragmentation de bases de l'ADN-ARN par la théorie de la fonctionnelle de la densité

Sadr-Arani, Leila 13 May 2014 (has links) (PDF)
Les rayonnements ionisants (RI) traversent les tissus humains, y déposent de l'énergie et la dissipent en fragmentant des molécules. Les fragments obtenus peuvent être mis en évidence par spectrométrie de masse. Malgré la quantité d'informations obtenue expérimentalement à partir du spectre de masse, l'expérience seule ne peut pas répondre à toutes les questions concernant les mécanismes de fragmentation des bases de l'ADN/ARN, et l'étude issue des méthodes quantiques est un complément précieux à ces informations. L'étude théorique permet de connaître les liaisons moléculaires rendues faibles dans chaque base par ionisation et ainsi de prévoir les mécanismes de fragmentation et les fragments produits. Le but de ce travail est d'étudier l'ionisation et les mécanismes de fragmentation de bases de l'ADN/ARN (Uracile, Cytosine, Adénine et Guanine) et d'identifier les cations correspondants à chaque pic des spectres de masse. Nous avons effectué nos calculs en utilisant la DFT avec la fonctionnelle PBE. Dans cette thèse, pour toutes les bases d'ARN, la réaction de rétro Diels-Alder est une des voies principales de dissociation (élimination de HNCO ou de NCO*) à l'exception de l'adénine qui n'a pas d'atome d'oxygène. La perte d'une molécule NH3 (NH2*) est aussi un chemin commun à toutes les bases contenant un ou plusieurs groupes amine. Egalement, la possibilité de la perte d'un hydrogène à partir des cations est également envisagée, ainsi que la dissociation de ces cations déshydrogénés et des bases protonées, en se limitant à l'uracile. Ce travail montre tout l'intérêt de l'apport de calcul (DFT) à l'interprétation des spectres de masse de bases de l'ADN

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