Global ETD Search

1	Clovis Technology and Settlement in the American Southeast Smallwood, Ashley Michelle 2011 August 1900 (has links) This dissertation presents new data on Clovis site occupation, technological organization, and settlement in the American Southeast. Evidence suggests that traditionally-accepted, western-centric models do not fully explain Clovis technological characteristics and settlement patterns in the region. My second chapter presents the results of a 40 square meter block excavation on the Topper site (SC) hillside where a buried Clovis assemblage has been recovered. I review the site geomorphology and formation processes to evaluate the context of the Clovis component, characterize the Clovis assemblage and the horizontal distribution of artifacts to understand how the Clovis occupants used this portion of the site, and compare these excavation results to the rest of the archaeological record at Topper to discuss the general nature of the Clovis occupation there. My third chapter focuses on the 174 bifaces from Topper to understand biface production. I present the process of manufacture then measure the variation in production characteristics at the site in terms of our current knowledge of Clovis biface technology. I conclude that Topper flintknappers used reduction strategies typical of Clovis-but created a biface assemblage with greater flexibility in design than documented at most other Clovis sites. Clovis groups adapted to local resource conditions and adjusted the organization of their technology accordingly. My fourth chapter analyzes southeastern Clovis point data and biface assemblages from Carson-Conn-Short (TN), Topper, and Williamson (VA) to test the technological implications of Kelly and Todd’s (1988) high-technology-forager model and Anderson’s (1990) staging-area model. Significant subregional variation exists in Clovis biface systems, such as differences in point morphology and the tempo of biface reduction. This variation suggests the subregions represent distinct populations who distinctly altered aspects of their technology but maintained fundamental elements of the Clovis tradition. Ultimately, I demonstrate there was greater variability in Clovis behavior across America. Recognizing regional variation in the archaeological record is key to understanding the complexities of Clovis origins and dispersal. Clovis Paleoindian Lithic technology American Southeast Settlement Site occupation Technological organization biface biface production Pleistocene
2	Development of new embedding techniques for strongly correlated electrons : from in-principle-exact formulations to practical approximations. / Nouvelles techniques d'embedding pour les électrons fortement corrélés : de la formulation exacte au développement d'approximations Senjean, Bruno 24 September 2018 (has links) Cette thèse traite du développement et de l’implémentation de nouvelles méthodes visant à décrire la corrélation électronique forte dans les molécules et les solides. Après avoir introduit l’état de l’art des méthodes utilisées en chimie quantique et en physique de la matière condensée, une nouvelle méthode hybride combinant théorie de la fonction d’onde et théorie de la fonctionnelle de la densité (DFT) est présentée et s’intitule “site-occupation embedding theory” (SOET). Celle-ci est appliquée au modèle de Hubbard à une dimension. Ensuite, le problème du gap fondamental est revisité en DFT pour les ensembles, où la dérivée discontinue est réécrite comme une fonctionnelle de la densité de l'état fondamental. Enfin, une extension à la chimie quantique est proposée, basée sur une fonction d’onde de séniorité zéro complémentée par une fonctionnelle de la matrice densité, et exprimée dans la base des orbitales naturelles. / The thesis deals with the development and implementation of new methods for the description of strong electron correlation effects in molecules and solids. After introducing the state of the art in quantum chemistry and in condensed matter physics, a new hybrid method so-called ``site-occupation embedding theory'' (SOET) is presented and is based on the merging of wavefunction theory and density functional theory (DFT). Different formulations of this theory are described and applied to the one-dimensional Hubbard model. In addition, a novel ensemble density functional theory approach has been derived to extract the fundamental gap exactly. In the latter approach, the infamous derivative discontinuity is reformulated as a derivative of a weight-dependent exchange-correlation functional. Finally, a quantum chemical extension of SOET is proposed and based on a seniority-zero wavefunction, completed by a functional of the density matrix and expressed in the natural orbital basis. Électrons fortement corrélés Théorie de la fonction d’onde Méthode d’embedding Site-occupation embedding theory DFT pour les ensembles Strongly correlated electrons Wavefunction theory Density functional theory Embedding methods Site-occupation embedding theory Hubbard model Ensemble DFT 541.2
3	Untersuchung atomarer Strukturen an geordnetem und nanokristallinem ternären Fe3Al / Studies of atomic scale structures of ordered and nanocrystalline ternary Fe3Al Rademacher, Thomas 13 July 2011 (has links) No description available. 530 Physik Physics 33.60 RD
4	Bestimmung von Platzbesetzung und Bindungsenergien mittels Atomsondentomographie / Site Occupation and Binding Energies by Means of Atom Probe Tomography Boll, Torben 07 May 2010 (has links) No description available. 530 Physik Mathematics and Computer Science Atomsonde Intermetallische Phase Platzbesetzung Bindungsenergie TiAl Cr Ag Nb Cu3Au DFT Spatial Distribution Maps AtomVicinity Simulation Atom Probe Tomography APT TAP 3DAP intermetallic TiAl Cr Nb Ag Cu3Au L10 L12 site occupation binding energy DFT Spatial Distribution Maps AtomVicinity Simulation 51.10 33.61

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