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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.
121

Traitement d’eaux usées industrielles par congélation sur paroi froide / Treatment of industrial wastewaters by freezing on cold surface

Htira, Thouaiba 23 September 2016 (has links)
Ce travail vise à étudier un procédé de traitement d'eaux usées industrielles par cristallisation en milieu fondu sur paroi froide. Deux effluents modèles sont choisis : un mélange eau/acétone et un mélange eau/acide propanoïque. Dans un premier temps, l'équilibre solide-liquide du mélange est étudié pour connaitre les limites de l'étude en température et en concentration. Le procédé de traitement de l'eau est alors conduit, selon un mode opératoire précis. Deux modes de fonctionnement sont mis en œuvre, un mode statique et un mode dynamique avec une circulation en boucle de la solution. La concentration en impuretés dans la glace est analysée après chaque cycle de congélation. L'étude paramétrique, conduite suivant un plan d'expériences, a mis en avant les effets importants de la concentration initiale de la solution et de la rampe de refroidissement. La microstructure de la glace est également analysée par microscopie en chambre froide pour interpréter les mécanismes d'incorporation d'impuretés au sein de la glace. Les inclusions de liquide sont sous la forme de poches de solution à faible vitesse de croissance et sont localisées dans les joints de grain à plus forte vitesse. Enfin, la modélisation du procédé fonctionnant en mode statique, par les éléments finis et en 2D axisymétrique avec frontière mobile, montre la présence de mouvements de convection. En mode dynamique, l'hydrodynamique de l'écoulement dans l'espace annulaire est décrite par une modélisation 3D prenant en compte la position de l'entrée et de la sortie. Les résultats démontrent la faisabilité du procédé et permettent des avancées significatives dans la compréhension des phénomènes mis en jeu / This work aims to study a process of industrial wastewater treatment by melt crystallization on a cold wall. Two effluent model solutions are chosen: water/acetone and water/propionic acid binary mixtures. First, the solid liquid phase diagrams are determined experimentally in order to delimit the operating range of temperature and concentration. Then, a parametric study of the wastewater treatment process by freezing is performed, by means of an experimental design, for two working modes, static mode and dynamic mode by adding a recirculation loop, respectively. The impurity concentration in the ice is analyzed after each freezing cycle. The process requires applying very precise conditions and the ice concentration mainly depends on the initial solution concentration and on the applied cooling rate. The ice microstructure is also characterized by optical microscopy in a cold chamber and gives insights into the mechanism of impurity incorporation: the liquid inclusions are localized under the form of solution pockets at low growth rate or between the polycrystals at higher growth rate. Lastly, 2D axisymmetric modelling of the process in static mode, based on finite elements and taking into account the moving boundary, shows the presence of buoyancy loops in relation with the density dependence of the solution with temperature. In dynamic mode, the hydrodynamics in the annular space is described by a 3D model to account for the positions of the inlet and outlet pipes. All the results demonstrate the process feasibility and allow better understanding of the occurring phenomena
122

Modélisation tridimensionnelle multibandes du transport quantique dans les transistors à nanofil

Pons, Nicolas 08 June 2011 (has links)
L’amélioration des performances du transistor MOS passe par la réduction de ses dimensions. Dans quelques années, la longueur de grille des dispositifs va descendre en dessous de 10 nm. A cette échelle, les effets quantiques deviennent prépondérants et dégradent considérablement les performances électriques des transistors à simple grille. Le transistor à nanofil avec grille enrobante est une architecture alternative intéressante pour augmenter le contrôle électrostatique du canal de conduction. Malgré les améliorations apportées par cette architecture, le courant à l’état bloqué reste perturbé par l’effet tunnel dans la direction source-drain. Afin de réduire ce courant sans réduire celui à l’état passant, nous avons étudié l’impact d’un rétrécissement local de la section transverse du canal coté drain (architecture notch-MOSFET). Pour cela, nous avons développé un simulateur 3D basé sur le formalisme des fonctions de Green hors équilibre couplé de façon auto-cohérente avec l’équation de Poisson. Ces calculs sont effectués dans l’approximation de la masse effective. Nous avons ensuite étudié le transport des trous dans les transistors à nanofil de type p, ainsi que l’influence d’une impureté ionisée dans le canal de ces dispositifs. La complexité de la bande de valence a nécessité la mise en œuvre d’un modèle k∙p à 6 bandes inclus dans le simulateur 3D évoqué précédemment. / Performances improvement of MOS transistors involves reduction of its dimensions. In a few years, the gate length of devices will reach sub-10 nm regime. At this scale, quantum effects become preponderant and considerably degrade electric performances of simple-gate transistors. The Gate-all-around nanowire transistor is an interesting alternative architecture to improve electrostatic control of the conduction channel. Despite the improvements made thanks to this architecture, the OFF-current remains disturbed by tunneling effect in source-drain direction. In order to decrease this current without decreasing the ON-current, we have studied the impact of local narrowing of transverse cross-section in drain side of the channel (notch-MOSFET architecture). To this purpose, we have developed a 3D simulator based on Non-equilibrium Green function formalism coupled self-consistently with Poisson equation. These simulations are performed in the effective mass approximation. Then we have studied holes transport in p-type nanowire transistors and the influence of an ionized impurity in the channel of these devices. The valence band complexity required six-band k∙p model development include into previously mentioned 3D simulator.
123

Bad Blood: Impurity and Danger in the Early Modern Spanish Mentality

Pyle, Rhonda 08 1900 (has links)
The current work is an intellectual history of how blood permeated early modern Spaniards' conceptions of morality and purity. This paper examines Spanish intellectuals' references to blood in their medical, theological, demonological, and historical works. Through these excerpts, this thesis demonstrates how this language of blood played a role in buttressing the church's conception of good morals. This, in turn, will show that blood was used as a way to persecute Jews and Muslims, and ultimately define the early modern Spanish identity.
124

Mechanical behavior of alternative multicrystalline silicon for solar cells

Orellana Pérez, Teresa 22 May 2013 (has links)
The usage of more inexpensive silicon feedstock for the crystallization of multicrystalline silicon blocks promises cost reduction for the photovoltaic industry. Less expensive substrates made out of metallurgical silicon (MG-Si) are used as a mechanical support for the epitaxial solar cell. Moreover, conventional inert solar cells can be produced from up-graded metallurgical silicon (UMG-Si). This feedstock has higher content of impurities which influences cell performance and mechanical strength of the wafers. Thus, it is of importance to know these effects in order to know which impurities should be preferentially removed or prevented during the crystallization process. Solar cell processing steps can also exert a change in the values of mechanical strength of processed multicrystalline silicon wafers until the fabrication of a solar cell. Bending tests, fracture toughness and dynamic elastic modulus measurements are performed in this work in order to research the mechanical behavior of multicrystalline silicon crystallized with different qualities of silicon feedstock. Bending tests and residual stress measurements allows the quantification of the mechanical strength of the wafers after every solar cell processing step. The experimental results are compared with theoretical models found in the classical literature about the mechanical properties of ceramics. The influence of second phase particles and thermal processes on the mechanical strength of silicon wafers can be predicted and analyzed with the theoretical models. Metals like Al and Cu can decrease the mechanical strength due to micro-cracking of the silicon matrix and introduction of high values of thermal residual stress. Additionally, amorphous silicon oxide particles (SiOx) lower the mechanical strength of multicrystalline silicon due to thermal residual stresses and elastic mismatch with silicon. Silicon nitride particles (Si3N4) reduce fracture toughness and cause failure by radial cracking in its surroundings due to its thermal mismatch with silicon. Finally, silicon carbide (SiC) and crystalline silicon oxide (SiOx) introduce thermal residual stresses but can have a toughening effect on the silicon matrix and hence, increase the mechanical strength of silicon wafers if the particles are smaller than a certain size. The surface of as-cut wafers after multi-wire sawing presents sharp micro-cracks that control their mechanical behavior. Subsequent removal of these micro-cracks by texture or damage etching approximately doubles the mechanical strength of silicon wafers. The mechanical behavior of the wafers is then governed by defects like cracks and particles formed during the crystallization of multicrystalline silicon blocks. Further thermal processing steps have a minor impact on the mechanical strength of the wafers compared to as-cut wafers. Finally, the mechanical strength of final solar cells is comparable to the mechanical strength of as-cut wafers due to the high residual thermal stress introduced after the formation of the metallic contacts which makes silicon prone to crack.
125

Electronic structure of strongly correlated low-dimensional spin ½ systems: cuprates and vanadates

Tchaplyguine, Igor 17 April 2003 (has links)
In the first two chapters we presented the basics of density functional theory and semiempirical LSD+U approximation, which was implemented in the full-potential local-orbital (FPLO) minimal-basis calculation scheme. In the third chapter we tested the implemented version of LSDA+U on 3d transitional metal monoxides. Essential improvement of the spectroscopic properties was obtained. A simple model describing the value and direction of the magnetic moment of a transition metal ion was presented. The model visualizes the interplay of the spin-orbit coupling and crystal field splitting. In the fourth chapter we calculated the electronic spectrum of the single Zn impurity in CuO2 plane considered as a vacancy in Cu 3d states. The analytic solution for the states of different symmetry was obtained. Depending on the strength of perturbation induced by the impurity on the neighboring Cu ions, the states are either resonant or localized. The critical values of the perturbation were computed. In the fifth chapter we presented the calculations for three novel vanadates: MgVO3, Sb2O2VO3 and VOMoO4. The tight-binding parameters and the exchange integrals were computed. The magnesium and antimony vanadates appeared to be spin-½ one-dimensional systems, the latter having much stronger one-dimensional character and being probably the best realization of inorganic spin-Peierls system. The molybdenum vanadate was found to be two-dimensional spin-½ system. The Mo 4d orbitals play an important role in the electronic transfer.
126

La vie intime en Grèce ancienne : entre pureté et impureté

Nicholls, Dorothée 12 1900 (has links)
Ce mémoire porte sur l’impureté dans la religion grecque et plus particulièrement sur le miasme causé par des évènements relevant de la vie intime. L’objectif de cette étude est de dresser un portrait complet de la vie intime par l’analyse des inscriptions religieuses et des documents littéraires. L’analyse de ces sources permet de dégager les modalités d’accès au temple et les processus purificatoires nécessaires pour recouvrer son état de pureté. De cet objectif en découle un second : formuler une théorie explicative sur l’origine de l’impureté en Grèce ancienne qui s’éloigne des théories interprétatives traditionnelles en misant davantage sur l’apport des sciences cognitives et la psychologie sociale à cette question. Divisée en quatre chapitres, la recherche porte d’abord sur l’impureté liée aux menstruations, un évènement profondément intime et peu étudié en raison de tabous modernes persistants. Le deuxième chapitre s’attarde quant à lui à l’impureté des relations sexuelles. Plus spécifiquement, cette deuxième section analyse les différences entre le miasme causé par des relations entre époux et par des relations extraconjugales. Le troisième chapitre du mémoire porte sur les évènements liés à la maternité, soit l’accouchement, l’avortement, la fausse-couche et l’allaitement. La mise en juxtaposition de plusieurs cas d’impureté permet de relever certaines tendances ou similarités. Finalement, le quatrième chapitre de cette étude consiste en l’exploration des théories biologiques et cognitives pouvant expliquer l’origine de l’impureté en Grèce ancienne. Cet ultime chapitre permet de conclure que l’impureté relève en partie de processus cognitifs et de réflexes qui ont été socialement renforcés par la religion grecque. / This master’s thesis concern impurity in Greek religion and more specifically the miasma related to the intimate life. The aim of this study is to provide a comprehensive portrait of intimate life through the analysis of religious inscriptions and literary documents. The examination of these sources allow the identification of the modalities for entering the temple and the processes necessary to regain its state of purity. This first objective leads to a second: I aim to formulate an explanatory theory on the origin of impurity in ancient Greece that departs from the traditional and interpretative theories by taking into account the contribution of cognitive science and social psychology to this question. Divided into four chapters, the research first focuses on the impurity of menstruation, a deeply intimate event and little studied due to persistent modern taboos. The second chapter dwells on the impurity of sexual relations. More specifically, this second section analyzes the differences between the miasma caused by relationships between spouses and by extramarital relationships. The third chapter deals with events related to motherhood, namely childbirth, abortion, miscarriage and breastfeeding. The juxtaposition of several types of impurity allow the identification of certain trends or similarities. Finally, the fourth chapter consists of the exploration of the biological and cognitive theories that could explain the origin of impurity in Ancient Greece. This final chapter seek to conclude that impurity is partly due to cognitive processes and reflexes which have been socially reinforced by the Greek religion.
127

Scanning Tunneling Microscopy Studies of Defects in Semiconductors: Inter-Defect and Host Interactions of Zn, Er, Mn, V, and Co Single-Atom Defects in GaAs(110)

Benjamin, Anne Laura 25 October 2018 (has links)
No description available.
128

SO4 in Cadmium Chalcogenides

Herklotz, Frank, Lavrov, Eduard V., Melnikov, Vladlen V. 11 June 2024 (has links)
A study combining infrared (IR) absorption spectroscopy and first-principles theory is presented for a sulfur–oxygen complex in CdSe characterized by IR absorption lines located at 1094, 1107, and 1126 cm-1 (10 K). The properties of the center are compared to a similar species occurring in CdTe that gives rise to two absorption lines at 1097 and 1108 cm-1 (10 K). Temperature- and polarization-sensitive measurements performed on 18O-enriched samples reveal that for both materials the IR absorption lines are due to split ν3 stretch vibrations of a distorted sulfate (SO4) tetrahedron, whereby the local point group of the SO4 complex is reduced to Cs and C3v in hexagonal CdSe and cubic CdTe, respectively. Measurements on the vibrational spectrum of the sulfate species in the spectral range of symmetric stretch (ν1), bend (ν4), and combinationmodes (ν1 þ ν3) are presented. The cation vacancy VCd is discussed as a likely site occupied by SO4 in CdSe.
129

Suitability of cellulose ester derivatives in hot melt extrusion.Thermal, rheological and thermodynamic approaches used in the characterization of cellulose ester derivatives for their suitability in pharmaceutical hot melt extrusion

Karandikar, Hrushikesh M. January 2015 (has links)
Applications of Hot Melt Extrusion (HME) in pharmaceuticals have become increasingly popular over the years but nonetheless a few obstacles still remain before wide scale implementation. In many instances these improvements are related to both processing and product performance. It is observed that HME process optimisation is majorly focused on the active pharmaceutical ingredient's (API) properties. Characterising polymeric properties for their suitability in HME should be equally studied since the impact of excipients on both product and process performance is just as vital. In this work, two well-established cellulose ester derivatives: Hydroxy Propyl Methyl Cellulose Acetate Succinate (HPMCAS) and Hydroxy Propyl Methyl Cellulose Phthalate (HPMCP) are studied for their HME suitability. Their thermal, thermodynamic, rheological, thermo-chemical and degradation kinetic properties were evaluated with model plasticisers and APIs. It was found the thermal properties of HPMCP are severely compromised whereas HPMCAS is more stable in the processing zone of 150 to 200 °C. Thermodynamic properties revealed that both polymers share an important solubility parameter range (20-30 MPa P1/2P) where the majority of plasticisers and BCS class II APIs lie. Thus, greater miscibility/solubility can be expected. Further, the processability of these two polymers investigated by rheometric measurements showed HPMCAS possesses better flow properties than HPMCP because HPMCP forms a weak network of chain interactions at a molecular level. However, adding plasticisers such as PEG and TEC the flow properties of HPMCP can be tailored. The study also showed that plasticisers have a major influence on thermo-chemical and kinetic properties of polymers. For instance, PEG reduced polymer degradation with reversal in kinetic parameters whereas blends of CA produced detrimental effects and increased polymer degradation with reduction in onset degradation temperatures. Further, both polymers are observed to be chemically reactive with the APIs containing free -OH, -SOR2RN- and -NH2 groups. Finally, these properties prove that suitability of HPMCP is highly debated for HME and demands great care in use while that of HPMCAS is relatively better than HPMCP in many instances.
130

The response of African religion to poverty, with specific reference to the Umzimkhulu Municipality

Manci, Thembayona Paulus Emmanuel 28 February 2005 (has links)
"The Response of African Religion to Poverty with specific reference to the Umzimkhulu Municipality" is a particular effort of the wider world that researches the ways and means for combating the scourge of poverty in society aiming at securing a better future for the future generations. In as much as African traditional religion is part of the culture, tradition and custom of its tenants, and as such aims at the wellbeing of its tenants, it is able to offer a response to poverty. It teaches about the importance of the values of community, meaningful and life-affirming relationships and the value of ubuntu. All these clamour for extended sharing and extended participation which are essential if society will continue to exist. African traditional religion maintains an ethic that says: `Real poverty results from the blockage of the vital links'. Celebrating economic achievements in food must be preceded by the celebration of people. `Batho pele': is the contemporary Democratic South Africa's slogan that suggests putting people in the center of life. It does not only call us to serve the poor, but also to allow them to champion the courses of the kind of service they desire. African traditional religion teaches that, together with the other institutions that govern the lives of people, religion and politics should have among other things a concern about production and distribution of the resources, hence the claim: `Food is also politics'. In their dealing with the problem of poverty, religion, politics and other social institutions ought to dedicate a special place to instilling positive attitudes towards the concept of work among their tenants. In this way the slogan `Batho pele' or people first, does not merely mean waiting to be served, but it also means that every body to the best of their ability ought to be doing something towards the production of the items of service. The inclusiveness of African religion in terms of what it calls `community' cautions society about the importance of the other beings in its consideration of poverty alleviation. Our economic wellbeing depends mostly on our attitude towards the other non-personal neighbours, prominent among which is our common abode, the earth, the land. / Religious Studies & Arabic / D.Th. (Religious Studies)

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