A novel method of producing die compacted powder metallurgy components with fully en-closed internal structures was developed. The physical characteristics of the compacts were evaluated by measuring bulk density, internal density gradients and compressive green strength. Additionally, a finite element simulation was developed to evaluate the compaction process of the internal structure compact. The internal structure compact displayed the anticipated lower bulk densities due to the less dense internal structure than a conventional powder metallurgy compact, however; higher local densities were found within the internal structure compact at all compaction pressures. Compressive green strength characteristics showed unique results where the strength in-creased up to 300 MPa compaction pressure, however; at 400 MPa there was a distinct plat-eau in green strength. This phenomenon was attributed to an increase in differential shear stress around the internal structure with a minimal increase in density from 300 MPa to 400 MPa.

La distribution de la matière dans l'Univers est supposée homogène et isotrope à très grande échelle mais l'observation de la distribution des galaxies lors<br />de grandes campagnes de recensements comme le SDSS nous montre un véritable réseau d'amas et de filaments sur des échelles de plusieurs centaines de<br />mégaparsecs.\\<br /><br />De nombreuses méthodes ont été développées dans le but de caractériser cette distribution et nous nous proposons dans cette thèse de présenter l'adaptation en trois dimensions d'un nouvel outil: le squelette.<br />Cette méthode vise à donner une définition mathématique claire des filaments ainsi qu'un algorithme numérique robuste permettant leur identification ainsi que le calcul de leurs propriétés. \\<br /><br />Afin de pouvoir comparer les résultats obtenus à partir des simulations N-corps de matière noire aux observations, une nouvelle méthode, baptisée MoLUSC, spécialisée dans la création de catalogues virtuels de<br />galaxies a aussi été élaborée. Elle se base sur les modèles semi-analytiques et est particulièrement efficace pour la fabrication de catalogues de grande<br />taille simulant de manière suffisamment réaliste les propriétés galactiques.\\<br /><br />Les utilisations de ces deux outils sont nombreuses et nous montrons par exemple qu'il est possible en mesurant la densité de longueur des filaments à<br />une échelle donnée de contraindre la quantité de matière dans l'univers<br />$\Omega_m$. Ces méthodes peuvent aussi être appliquées avec succès à la mesure statistique des propriétés du flux de matière noire le long des filaments, une mesure inédite. Nous présentons enfin de nombreuses applications possibles dont les résultats préliminaires sont très encourageants.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20346号 / 工博第4283号 / 新制||工||1663(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 清野 純史, 教授 高橋 良和, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Floods are one of the most important natural disasters regarding damages caused by them. Major reasons of huge damages of floods are unplanned urbanization, narrowing of river beds and incorrect operation of water control structures. Geographic Information Systems (GIS) can provide important tools to be used in flood modeling studies. In this study, Lake Mogan, Lake Eymir and Incesu Detention Pond subbasins are studied for flooding events within GIS framework. These subbasins are important catchment areas of city of Ankara with total drainage area of 1070 km2. Soil Conservation Service (SCS) method is used to obtain flood hydrographs for 12 hour duration and 50, 100 and 500 year return periods. Flood routing procedure is applied to obtain discharges at the outlet of the Mogan and Eymir Lakes and Incesu Detention Pond. Operation performance of water control structures are tried to be estimated by using hydrographs which are obtained for different scenarios. Results show that elements of Lake Mogan Water Control Structure do not have capability to discharge 500 year storm safely to the downstream of the lake. However, 100 year storm can be routed without creating problem if necessary small precautions are taken. On the other hand, water control elements of Lake Eymir and Incesu Detention Pond can transmit obtained flood volumes to the downstream parts by assuming that closed conduit at the exit of Incesu Detention Pond can safely convey resultant flood discharges.

Quais as causas e condições que levam à ocorrência de diferentes estruturas de Coordenação Vertical (CV) dentro de uma mesma indústria? Este estudo objetiva identificar, caracterizar e analisar as diferentes formas de coordenação vertical encontradas em onze empresas pertencentes ao setor de pêssegos em conserva no Estado do Rio Grande do Sul (Brasil). A presente pesquisa, caracterizada como um estudo multi-caso, utilizou-se de duas abordagens teóricas da Economia para estruturar seu modelo de análise: a da Economia dos Custos de Transação e a da Visão Baseada em Recursos. Os resultados revelam que os fatores mais relevantes para a escolha da definição das estruturas de coordenação vertical entre empresas e fornecedores (destas indústrias) são transacionais e de recursos. Altos níveis de incerteza e oportunismo (custos de transação) levam as empresas a adotar estruturas hierárquicas de coordenação (produção própria). O estudo da dinâmica evolutiva das estruturas de Coordenação Vertical permitiu relaciona-las às características dos recursos e dos custos das transações. A primeira, relacionando o modelo de Coordenação Vertical adotado pela empresa aos tipos de recursos (tangíveis e intangíveis) disponíveis; e a segunda, à imprevisibilidade e relevância de problemas no fluxo de suprimento de matéria-prima. A disponibilidade de recursos intangíveis mostrou ter um forte impacto sobre a adoção de relações mais integradas com fornecedores, enquanto que uma maior disponibilidade de recursos tangíveis exerce uma pressão maior no sentido da verticalização da produção de suprimentos. E a segunda, relacionando a imprevisibilidade e a relevância dos problemas no suprimento de matéria prima. Quanto maior a imprevisibilidade ou velocidade de ocorrência e relevância de um problema no fluxo de suprimentos maior será a tendência de reação no sentido da verticalização da produção e vice-versa. / What are the causes and conditions that lead to the existence of different vertical co-ordination (VC) structures within the same industry? This study aims to identify, characterize and analyze the varying forms of VC found in eleven firms that comprise the peach conserve industry in Rio Grande do Sul (Brazil). In order to establish its analysis model, the present research, which may be characterized as a multi-case study, was based on two theoretical concepts on economics: the Transactional Costs Economics, and the Resources Based View. The results obtained reveal that the most relevant factors that influence the choice of VC structure among these firms and their suppliers are transactional and resources. High levels of uncertainty and opportunism (transaction factors) lead firms to adopt more hierarchical VC structures (own production). Studying the VC structures evolutive dynamics, it was allowed to relate them to the characteristics of Resources and Transactional Costs. The former one has related the VC model adopted by the firm to the different kinds of available resources (tangible or intangible); and the latter one, to the unforeseeability and relevance of raw material supply flow difficulties. Bigger intangible resources availability is shown to have a strong impact on the adoption of more integrated VC structures; whereas greater capital availability moves firms towards a more hierarchical VC of supplies production. Second, the bigger the unforeseeability and the relevance of raw material supply flow difficulties, accordingly bigger will be the reaction tendency to a production verticalization, and vice-versa.

Quais as causas e condições que levam à ocorrência de diferentes estruturas de Coordenação Vertical (CV) dentro de uma mesma indústria? Este estudo objetiva identificar, caracterizar e analisar as diferentes formas de coordenação vertical encontradas em onze empresas pertencentes ao setor de pêssegos em conserva no Estado do Rio Grande do Sul (Brasil). A presente pesquisa, caracterizada como um estudo multi-caso, utilizou-se de duas abordagens teóricas da Economia para estruturar seu modelo de análise: a da Economia dos Custos de Transação e a da Visão Baseada em Recursos. Os resultados revelam que os fatores mais relevantes para a escolha da definição das estruturas de coordenação vertical entre empresas e fornecedores (destas indústrias) são transacionais e de recursos. Altos níveis de incerteza e oportunismo (custos de transação) levam as empresas a adotar estruturas hierárquicas de coordenação (produção própria). O estudo da dinâmica evolutiva das estruturas de Coordenação Vertical permitiu relaciona-las às características dos recursos e dos custos das transações. A primeira, relacionando o modelo de Coordenação Vertical adotado pela empresa aos tipos de recursos (tangíveis e intangíveis) disponíveis; e a segunda, à imprevisibilidade e relevância de problemas no fluxo de suprimento de matéria-prima. A disponibilidade de recursos intangíveis mostrou ter um forte impacto sobre a adoção de relações mais integradas com fornecedores, enquanto que uma maior disponibilidade de recursos tangíveis exerce uma pressão maior no sentido da verticalização da produção de suprimentos. E a segunda, relacionando a imprevisibilidade e a relevância dos problemas no suprimento de matéria prima. Quanto maior a imprevisibilidade ou velocidade de ocorrência e relevância de um problema no fluxo de suprimentos maior será a tendência de reação no sentido da verticalização da produção e vice-versa. / What are the causes and conditions that lead to the existence of different vertical co-ordination (VC) structures within the same industry? This study aims to identify, characterize and analyze the varying forms of VC found in eleven firms that comprise the peach conserve industry in Rio Grande do Sul (Brazil). In order to establish its analysis model, the present research, which may be characterized as a multi-case study, was based on two theoretical concepts on economics: the Transactional Costs Economics, and the Resources Based View. The results obtained reveal that the most relevant factors that influence the choice of VC structure among these firms and their suppliers are transactional and resources. High levels of uncertainty and opportunism (transaction factors) lead firms to adopt more hierarchical VC structures (own production). Studying the VC structures evolutive dynamics, it was allowed to relate them to the characteristics of Resources and Transactional Costs. The former one has related the VC model adopted by the firm to the different kinds of available resources (tangible or intangible); and the latter one, to the unforeseeability and relevance of raw material supply flow difficulties. Bigger intangible resources availability is shown to have a strong impact on the adoption of more integrated VC structures; whereas greater capital availability moves firms towards a more hierarchical VC of supplies production. Second, the bigger the unforeseeability and the relevance of raw material supply flow difficulties, accordingly bigger will be the reaction tendency to a production verticalization, and vice-versa.

Quais as causas e condições que levam à ocorrência de diferentes estruturas de Coordenação Vertical (CV) dentro de uma mesma indústria? Este estudo objetiva identificar, caracterizar e analisar as diferentes formas de coordenação vertical encontradas em onze empresas pertencentes ao setor de pêssegos em conserva no Estado do Rio Grande do Sul (Brasil). A presente pesquisa, caracterizada como um estudo multi-caso, utilizou-se de duas abordagens teóricas da Economia para estruturar seu modelo de análise: a da Economia dos Custos de Transação e a da Visão Baseada em Recursos. Os resultados revelam que os fatores mais relevantes para a escolha da definição das estruturas de coordenação vertical entre empresas e fornecedores (destas indústrias) são transacionais e de recursos. Altos níveis de incerteza e oportunismo (custos de transação) levam as empresas a adotar estruturas hierárquicas de coordenação (produção própria). O estudo da dinâmica evolutiva das estruturas de Coordenação Vertical permitiu relaciona-las às características dos recursos e dos custos das transações. A primeira, relacionando o modelo de Coordenação Vertical adotado pela empresa aos tipos de recursos (tangíveis e intangíveis) disponíveis; e a segunda, à imprevisibilidade e relevância de problemas no fluxo de suprimento de matéria-prima. A disponibilidade de recursos intangíveis mostrou ter um forte impacto sobre a adoção de relações mais integradas com fornecedores, enquanto que uma maior disponibilidade de recursos tangíveis exerce uma pressão maior no sentido da verticalização da produção de suprimentos. E a segunda, relacionando a imprevisibilidade e a relevância dos problemas no suprimento de matéria prima. Quanto maior a imprevisibilidade ou velocidade de ocorrência e relevância de um problema no fluxo de suprimentos maior será a tendência de reação no sentido da verticalização da produção e vice-versa. / What are the causes and conditions that lead to the existence of different vertical co-ordination (VC) structures within the same industry? This study aims to identify, characterize and analyze the varying forms of VC found in eleven firms that comprise the peach conserve industry in Rio Grande do Sul (Brazil). In order to establish its analysis model, the present research, which may be characterized as a multi-case study, was based on two theoretical concepts on economics: the Transactional Costs Economics, and the Resources Based View. The results obtained reveal that the most relevant factors that influence the choice of VC structure among these firms and their suppliers are transactional and resources. High levels of uncertainty and opportunism (transaction factors) lead firms to adopt more hierarchical VC structures (own production). Studying the VC structures evolutive dynamics, it was allowed to relate them to the characteristics of Resources and Transactional Costs. The former one has related the VC model adopted by the firm to the different kinds of available resources (tangible or intangible); and the latter one, to the unforeseeability and relevance of raw material supply flow difficulties. Bigger intangible resources availability is shown to have a strong impact on the adoption of more integrated VC structures; whereas greater capital availability moves firms towards a more hierarchical VC of supplies production. Second, the bigger the unforeseeability and the relevance of raw material supply flow difficulties, accordingly bigger will be the reaction tendency to a production verticalization, and vice-versa.

Understanding charge transport through molecular junctions and factors affecting the conductivity at the single molecule level is the first step in designing functional electronic devices using individual molecules. A variety of methods have been developed to fabricate metal-molecule-metal junctions in order to evaluate Single Molecule Conductance (SMC). Single molecule junctions usually are formed by wiring a molecule between two metal electrodes via anchoring groups that provide efficient electronic coupling and bind the organic molecular backbone to the metal electrodes. We demonstrated a novel strategy to fabricate single molecule junctions by employing the stabilization provided by the long range ordered structure of the molecules on the surface. The templates formed by the ordered molecular adlayer immobilize the molecule on the electrode surface and facilitate conductance measurements of single molecule junctions with controlled molecular orientation. This strategy enables the construction of orientation-controlled single molecule junctions, with molecules lacking proper anchoring groups that cannot be formed via conventional SMC methods. Utilizing Scanning Tunneling Microscopy (STM) imaging and STM break junction (STM-BJ) techniques combined, we employed the molecular assembly of mesitylene to create highly conductive molecular junctions with controlled orientation of benzene ring perpendicular to the STM tip as the electrode. The long range ordered structure of mesitylene molecules imaged using STM, supports the hypothesis that mesitylene is initially adsorbed on the Au(111) with the benzene ring lying flat on the surface and perpendicular to the Au tip. Thus, long range ordered structure of mesitylene facilitates formation of Au-π-Au junctions. Mesitylene molecules do not have standard anchoring groups providing enough contact to the gold electrode and the only assumable geometry for the molecules in the junction is via direct contact between Au and the π system of the benzene ring in mesitylene. SMC measurements for Au/mesitylene/Au junctions results in a molecular conductance value around 0.125Go, two orders of magnitude higher than the measured conductance of a benzene ring connected via anchoring groups. We attributed this conductance peak to charge transport perpendicular to the benzene ring due to direct coupling between the π system and the gold electrode that happens in planar orientation. The conductance we measured for planar orientation of benzene ring is two order of magnitude larger than conductance of junctions formed with benzene derivatives with conventional linkers. Thus, altering the orientation of a single benzene-containing molecule between the two electrodes from planar orientation to the upright attached via the linkers, results in altering the conductivity in a large order. Based on these findings, by utilizing STM imaging and STM-BJ in an electrochemical environment including potential induced self-assembly formation of terephthalic acid, we designed an electrochemical single molecule switch. Terephthalic acid forms large domains of ordered structure on negatively charged Au(111) surface under negative electrochemical surface potentials with the benzene ring lying flat on the surface due to hydrogen bonding between carboxylic acid groups of neighboring molecules. Formation of long range ordered structure facilitates direct contact between the π system of the benzene ring and the gold electrodes resulting in the conductance peak. On positively charged Au(111), deprotonation of carboxylic acid groups leads to absence of long range ordered structure of molecules with planar orientation and absence of the conductance peak. In this case alternating the surface (electrode) potential from negative to positive charge densities induces a transition in the adlayer structure on the surface and switches conductance value. Hence, electrochemical surface potential can, in principle, be employed as an external stimulus to switch single molecule arrangement on the surface and the conductance in the junction. The observation of conductance switching due to molecule’s arrangement in the junction lead to the hypothesis that for any benzene derivative, an orientation-dependent conductance in the junction due to the contact geometry (i.e. electrode-anchoring groups versus direct electrode-π contact) should be expected. Conventional techniques in fabricating single molecule junctions enable accessing charge transport along only one direction, i.e., between two anchoring groups. However, molecules such as benzene derivatives are anisotropic objects and we are able to measure an orientation-dependent conductance. In order to systematically study anisotropic conductivity at single molecule level, we need to measure the conductance in different and well-controlled orientations of single molecules in the junction. We employed the same EC-STM-BJ set up for SMC measurements and utilize electrochemical potential of the substrate (electrode) as the tuning source to variate the orientation of the single molecule in the junction. We investigated single molecule conductance of the benzene rings with carboxylic acid functional groups in two orientations: one with the benzene ring bridging between two electrodes using carboxylic acids as anchoring groups (upright); and one with the molecule lying flat on the substrate perpendicular to the STM tip (planar). Physisorption of these species on the Au (111) single crystal electrode surface at negative electrochemical potentials results in an ordered structure with the benzene ring in a planar orientation. Positive electrochemical potentials cause formation of the ordered structure with molecules standing upright due to coordination of a deprotonated carboxyl groups to the electrode surface. Thus, formation of the single molecule junction and consequently conductivity measurements is facilitated in two directions for the same molecule and anisotropic conductivity can be studied. In engineering well-ordered two-dimensional (2-D) molecular structures with controlled assembly of molecular species, pH can be employed as another tuning source for the molecular structures and adsorption in experiments conducted in aqueous solutions. Based on simple chemical principles, amine (NH2) groups are hydrogen bond acceptors and donors. Amines are soluble in water and protonation results in protonated (NH3+) and unprotonated (NH2) amine groups in acidic and moderately acidic/neutral solutions, respectively. Thus, amines are suitable molecular building blocks for fabricating 2-D supramolecular structures where pH is employed as a knob to manipulate intermolecular hydrogen bonding leading to phase transitions. We investigated pH induced structural changes in the 1,3,5–triaminobenzene (TAB) monolayer and the formation/disruption of hydrogen bonds between neighboring molecules. Our STM images indicate that in the concentrated acidic solution, the protonated amine groups of TAB are not able to form H-bonds and long range ordered structure of TAB does not form on the Au(111) surface. However, in moderately acidic solution (pH ~ 5.5) at room temperature, protonation on the ring carbon atom generates species capable of forming H-bonds leading to the formation of the long range ordered structures of TAB molecules. Utilizing EC-STM set up, we investigated the controllable fabrication of a TAB 2-D supramolecular structure based on amine-amine hydrogen bonding and effect of pH in formation of ordered/disordered TAB network. / Chemistry

Title: Structure analysis of some transition metal silicides using X-ray diffraction and dynamical refinement against electron diffraction data Author: Cinthia Antunes Corrˆea Department: Physics of Materials Supervisor: prof. RNDr. Miloš Janeček, CSc., Department of Physics of Materials Abstract: This thesis presents the crystal structure analysis of several transition metal silicides. The crystal structures were studied primarily by precession electron diffraction tomography (PEDT) employing the dynamical refinement, a method recently developed for accurate crystal structure refinement of electron diffraction data. The optimal values of the parameters of the method were proposed based on the comparison between the dynamical refinement of PEDT data and a high- quality reference structure. We present the results of the comparison using a Ni2Si nanowire with the diameter of 15 nm. The average atomic distance between the model obtained by the dynamical refinement on PEDT data and the one by single crystal X-ray diffraction was 0.006 ˚A. Knowing the accuracy and limitations of the method, the crystal structure of Ni3Si2 was redetermined on a nanowire with 35 nm of diameter. The model obtained had an average error in the atomic posi- tions of 0.006 ˚A. These results show that the accuracy achieved by the dynamical...