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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.
271

Contribuição à química supramolecular de 3,4-tetra(piridil) porfirazinas tetrarutenadas / Contribution to supramolecular chemistry of tetramerized 3,4-tetra (pyridyl) porphyrazines

Marcos Makoto Toyama 22 August 2003 (has links)
Neste trabalho, descreve-se a síntese, caracterização e propriedades dos complexos derivados da tetra(3,4-piridil)porfirazina com os grupos [Ru(bipy)2Cl]1+. A conjugação eletrônica entre o resíduo piridínico e o anel da porfirazina promovem uma eficiente comunicação entre os grupos periféricos e o central, que é refletido no espectro de emissão e seu correspondente perfil de excitação. Esse tipo de comportamento revela um efeito antena no sistema H2TPyPzTRu, contrastante com as propriedades fotofisicas das porfirinas análogas TPyPRu, onde os grupos piridínicos exibem baixa interação eletrônica ao anel porfirínico. Apesar do forte acoplamento eletrônico entre os grupos perféricos e o central, as propriedades eletrônicas dos complexos de rutênio foram preservadas, exibindo potenciais redox muito próximos dos complexos livres e comportamento espectroeletroquímico típicos de complexos metálicos N-heterocíclicos. Esses aspectos levam a novas perspectivas relacionadas à estrutura dos compostos, pois são potencialmente interessantes para o estudo referente à formação de oxigênio singlete e para PDT. Outro direcionamento desta tese, foi o de explorar a geração de novas interfaces baseadas na formação de pares iônicos constituídos pelas espécies H2TPyPzTRu/CuTSPc em comparação com o filme da espécie catiônica H2TPyPzTRu. Através de medidas de espectroscopia de impedância eletroquímica, foram constatados mecanismos distintos de condução nos filmes formados, que pode ser ou um mecanismo misto envolvendo os complexos periféricos e o anel central da porfirazina, ou um mecanismo de condução eletrônica envolvendo somente o sistema de empilhamento π do anel central da porfirazina. / In this work, we describe the synthesis, characterization and properties of derived tetra(3,4-pyridil)porphyrazine complex containing four [Ru(bipy)2Cl]1+ groups. The electronic conjugation between the pyridinium moiety and the porphyrazine ring promote an efficient communication between the peripherical groups and central ring, which is reflected in the emission spectrum and related excitation profile. The observed behavior reveals an efficient antenna effect in the H2TPyPzTRu system. ln spite of the strong electronic coupling between the central and peripherical groups, the electronic properties of ruthenium complex were preserved, exhibiting redox potencials very close to those of free complexes. These aspects provided new perspectives of exploiting the compound strutures, particularly the oxygen singlet formation and PDT application. Another aspect focused in this investigation was the generation of new interfaces based on ion-pair formation of H2TPyPzTRu/CuTSPc, in comparison with its cationic species H2TPyPzTRu alone. By means of electrochemical impedance spectrocopy, it was shown that the conduction mecanisms in these films involve either the peripherical complex and the central porphyrazine ring.
272

Studie standardizace určené komodity pro činnosti nákupu / The Study of Standardization for the Business of Buying Commodities

Vlašic, Petr January 2016 (has links)
Master’s thesis deal with commodities of metallurgical and connecting material in engineering firm. For these commodities is concocted an analysis of current statement, based on it will be designed its material standard. Purpose of this dissertation should be reaching of potential savings of money, time and increasing of productivity.
273

Theoretical and experimental studies of surface and interfacial phenomena involving steel surfaces

Cao, Weimin January 2010 (has links)
The present work was initiated to investigate the surface- and interfacial phenomena for iron and slag/iron systems. The aim was to understand the mechanism of the effect of surface active elements on surface and interfacial properties. In the present work, the adsorption of oxygen and sulfur on iron surface as well as adatom surface movements were studied based on the ab initio method. BCC iron melting phenomena and sulfur diffusion in molten iron were investigated by Monte Carlo simulations. The impact of oxygen potential on interfacial mass transfer was carried out by X-ray sessile drop method. Firstly, the structural, electronic and magnetic properties as well as thermodynamic stability were studied by Density functional theory (DFT). The hollow site was found to be the most stable adsorption site both for oxygen and sulfur adsorbed on iron (100) surface, which is in agreement with the experiment. The relaxation geometries and difference charge density of the different adsorption systems were calculated to analyze the interaction and bonding properties between Fe and O/S. It can be found that the charge redistribution was related to the geometry relaxation. In addition, the sulfur coverage is considered from a quarter of one monolayer (1ML) to a full monolayer. It was found that the work function and its change Δφ increased with S coverage, in very good agreement with experiment. Due to a recent discussion regarding the influence of charge transfer on Δφ, it is shown in the present work that the increase in Δφ can be explained by the increasing surface dipole moment as a function of S coverage. S strongly interacts with the surface Fe layer and decreases the surface magnetic moment as the S coverage increases. Secondly, a two dimensional (2D) gas model based on density functional calculations combined with thermodynamics and statistical physics, was proposed to simulate the movement of the surface active elements, viz. oxygen and sulfur atoms on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and energy barrier in the final expression developed. The calculated results were based on the density function and thermodynamics & statistical physics theories. In addition, this 2D gas model can be used to simulate and give an atomic view of the complex interfacial phenomena in the steelmaking refining process. A distance dependent atomistic Monte Carlo model was developed for studying the iron melting phenomenon as well as effect of sulfur on molten iron surface. The effect of boundary conditions on the melting process of an ensemble of bcc iron atoms has been investigated using a Lennard-Jones distance dependent pair potential. The stability of melting process was energetically and spatially analyzed under fixed wall and free surface conditions and the effects of short and long-range interactions were discussed. The role of boundary conditions was significantly reduced when long-range interactions were used in the simulation. This model was further developed for investigating the effect of sulfur on molten iron surface. A combination of fixed wall and free surface boundary condition was found to well-represent the molten bath configuration while considering the second nearest neighbor interactions. Calculations concerning the diffusion of sulfur on molten surface were carried out as a function of temperature and sulfur concentration. Our results show that sulfur atoms tended to diffuse away from the surface into the liquid bulk and the diffusion rate increased by increasing temperature. Finally, impact of oxygen potential on sulfur mass transfer at slag/metal interface, was carried out by X-ray sessile drop method. The movement of sulfur at the slag/metal interface was monitored in dynamic mode at temperature 1873 K under non-equilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. As the partial pressure of oxygen increased, it was found that interfacial velocity as well as the oscillation amplitude increased. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity. / QC 20101123
274

3D-Simulation und Planung von Anlagen der Hütten- und Walzwerkstechnik

Oppermann, Ingo 11 May 2009 (has links) (PDF)
In der Präsentation werden typische Engineeringaufgaben präsentiert, die mit modernen IT-Werkzeugen erledigt werden. Es wird auf die Einführung und die Durchgängigkeit eines 3D-CAD-Systems eingegangen und gezeigt, wie mit diesem System Simulations- und Prozesskettenthemen in der Praxis bei der SMS Siemag AG behandelt werden. Ebenfalls anhand von Beispielen wird die Thematik der großen Baugruppen und der Anlagenplanung im 3D-Engineering dargestellt.
275

Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys

Wang, Haijuan January 2010 (has links)
With the progress of high alloy steelmaking processes, it is essential to minimize the loss of valuable metals, like chromium and vanadium during the decarburization process, from both economic as well as environmental view points. One unique technique to realize this aim, used in the present work, is the decarburization of high alloy steel grades using oxygen with CO2 in order to reduce the partial pressure of oxygen. In the present work, the investigation on the oxidation of iron-chromium and iron-vanadium molten alloys under CO2-O2 mixtures was carried out and presented in this dissertation. For oxidation study on Fe-Cr molten alloy with CO2-O2 mixtures, on the basis of thermodynamic analysis, energy balance calculation and modeling results, experimental validation in laboratory was carried out, and later on, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts under controlled partial pressure of oxygen was investigated. Thermodynamics calculation and energy balance estimation demonstrated that, it is possible to use CO2 or CO2-O2 mixtures as decarburizers during EAF process and high initial carbon contents in the steel can be adopted at the beginning in order to reduce the cost. A generic model has been developed to describe the overall process kinetics prevailing in metallurgical reactors containing liquid metal and gas bubbles. This model is general and can be extended further to consider any gas liquid reactions in any chemical engineering reactor, and especially the metallurgical ones, like AOD. In the present dissertation, the model is applied in predicting the evolution of Cr and C contents in a Fe-C-Cr melt during injection of different O2-CO2 mixtures. The related simulation results illustrated that CO2 is efficient in Cr retention. In order to verify the modeling results, 1kg induction furnace experiments were carried out in the present laboratory. The results indicated that the predictions of the model are in good agreement with the experimental results. Meanwhile, the experimental results indicated that the Cr-losses can be significantly lowered by replacing the oxygen with CO2 in the injected gas, specifically for Fe-Cr-C melts with carbon levels higher than about 0.8 mass%. Subsequently, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts was investigated under different CO2-O2 mixtures. It is indicated that, the oxidation rate is controlled by the chemical reaction at the initial stage and the reaction rate can be expressed as  at the Cr range of 11-21 mass% in the Fe-Cr melt. For oxidation study on Fe-V liquid alloy, the investigation of the oxidation kinetics was carried out under CO2-O2 mixtures, which is followed by the study on thermodynamic properties of vanadium containing slags. During oxidation of Fe-V melt, in the case of alloys with vanadium contents exceeding 10 mass%, there exists an incubation period before the chemical reactions prevail the process. In addition, the ‘incubation time’ increased with the increase of temperature and the vanadium content, whereas it decreased with the increase of oxygen partial pressure in the oxidant gas. High-temperature mass spectrometric method was used to determine the activity of the vanadium oxide in CaO-MgO-Al2O3-SiO2-V2O3 slags, whereas, the oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOxslag system was studied by XANES method. The results indicated that, higher basicities stabilize higher vanadium oxidation state, whereas, higher temperature stabilizes lower vanadium oxidation state. The present work, which was carried out within the ECO-STEELMAKING project funded by MISTRA via Jernkontoret is expected to lead to implementation of some modifications in high alloy steel production based on fundamental concepts towards more environment-friendly steel processing. / <p>QC20100628</p>
276

Logistika a řízení výroby ve vybraném podniku / Logistics and production management in the selected company

ČIHÁKOVÁ, Pavlína January 2012 (has links)
The main topic of the thesis is the area of logistics and production with emphasis on saving time and place in the processing of order, the layout of machines, workplaces and warehouses in the production hall. The advantages and disadvantages were analyzed in the selected company, critical points were determined and solutions were designed, comparison and evaluation were carried out with the original condition. The work is based on the theoretical foundations of the subject, collected data from its own investigations and observations of the analyzed processes.
277

Caracterização do aço SAE 8630 modificado, amanteigado com INCONEL 625 pelo processo de soldagem MIG

Costa, Esdras Carvalho da 27 March 2013 (has links)
Made available in DSpace on 2015-05-08T14:59:48Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3074686 bytes, checksum: ed7a06179e3d3259d7c106457864da4c (MD5) Previous issue date: 2013-03-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / With the recent discovery of the existence of oil deposits in Brazil. Those responsible for the exploitation are becoming increasingly aware of the development of technologies for the extraction of oil and natural gas in deep waters. In this scholarly work, one of these developed technologies, the base metal steel SAE 8630 modified by the addition of metal buttery INCONEL 625 (AWS ER NiCrMo 3) through the MIG welding process, was investigated. To minimize the formation of martensite thermal cycles of annealing 873oC in a period of one hour and two thermal cycles strain relief (before and after buttering), both at temperatures of 677oC in a range of two hours. After these processes it was possible to verify the presence of diffusion processes of chemical elements and formation of possible precipitates. These trials were conducted by optical microscopy and scanning electron microscopy coupled with EDS while changes in hardness and toughness were observed before and after heat treatment for stress relief of the metal. These are the metallurgical and mechanical results from analysis of the areas close to regions of the MB, HAZ, ZL and MB. / Com as recentes revelações da existência de jazidas de petróleo no território brasileiro. Fez se que os responsáveis pela exploração destas regiões, se demonstrem apreensivos quanto ao desenvolvimento de tecnologias para a extração de petróleo e de gás natural em águas profundas. Neste trabalho acadêmico, com o uso de uma dessas tecnologias em desenvolvimento, foi abordado o uso do metal de base o aço SAE 8630 modificado, amanteigado pelo metal de adição INCONEL 625 (AWS E NiCrMo 3) através do processo de soldagem MIG. Para minimizar a constituição da martensita, foram aplicados ciclos térmicos de têmpera de 873oC em um intervalo de uma hora e mais dois ciclos térmicos de alívio de tensões (antes e após o amanteigamento), ambos em temperaturas de 677oC em um intervalo de duas horas. Verificou se a presença de processos de difusão de elementos químicos e formação de possíveis precipitados. Estes foram caracterizados pelos ensaios de microscopia ótica e microscopia eletrônica de varredura juntamente com o EDS e alterações quanto a microdureza e dureza foram observadas antes e após o tratamento térmico de alívio de tensões. Sendo estes resultados metalúrgicos e mecânicos analisados em áreas próximas das regiões do MB, ZTA, ZL e MB.
278

Grupos geracionais e o comprometimento organizacional : um estudo em uma empresa metalúrgica de Caxias do Sul

Batista, Francisco Honório Araújo 30 September 2011 (has links)
A proposta deste trabalho é de analisar o comprometimento organizacional dos funcionários de uma empresa metalúrgica de Caxias do sul. Esta empresa em análise é a Cemar Legrand empresa pertencente ao Grupo Legrand (Grupo Multinacional Francês). Foi utilizado para a análise um instrumento de pesquisa com reconhecimento pela comunidade científica chamado de modelo dos três componentes de Allen e Meyer (1997) , modelo que caracteriza o comprometimento organizacional em suas dimensões afetivo, instrumental e normativo, e foi aplicado o questionário em uma amostra de 311 funcionários da empresa. A análise deste trabalho também foi ampliada no sentido analisar este comprometimento organizacional por grupo de funcionários pertencentes às gerações (Geração Veteranos, Geração Baby boomers, Geração X e Geração Y), esta teoria das gerações, tem seu nascedouro na teoria geracional de Strauss e Howe (1991) onde os autores definem que em cada século há quatro gerações distintas e que cada uma das gerações comportam-se conforme as características de cada período geracional, bem como pelos acontecimentos de sua época. O resultado deste trabalho demonstra que há um bom comprometimento dos funcionários para com a empresa e não foi encontrado diferenças entre as dimensões do comprometimento para as gerações pesquisadas. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-03T17:14:25Z No. of bitstreams: 1 Dissertacao Francisco H A Batista.pdf: 1507649 bytes, checksum: 9b3ef22087ae3901c216ccc051c879d9 (MD5) / Made available in DSpace on 2014-06-03T17:14:25Z (GMT). No. of bitstreams: 1 Dissertacao Francisco H A Batista.pdf: 1507649 bytes, checksum: 9b3ef22087ae3901c216ccc051c879d9 (MD5) / The purpose of this study is to examine organizational commitment of employees at a metallurgical company in Caxias do Sul. This company in question is Cemar Legrand company belonging to Legrand Group. Was used to analyze a research tool to recognize the scientific community called "model of the three components of Allen and Meyer (1997)," model that characterizes the organizational commitment in their affective, instrumental and normative dimensions, and the questionnaire was applied in a sample of 311 employees. This analysis has also been expanded in order to analyze organizational commitment by this group of employees through the theory of generations (Generation Veterans, Generation Baby Boomers, Generation X and Generation Y), this theory of generations, has its origin in the theory of generational Strauss and Howe (1991) where the authors define it in every century there are four different generations and each generation behaves according to the characteristics of each generational period, as well as by the events of his time. This investigation demonstrates that there is a good employee commitment to the company and was not found differences between the dimensions of commitment for the four generations surveyed.
279

Grupos geracionais e o comprometimento organizacional : um estudo em uma empresa metalúrgica de Caxias do Sul

Batista, Francisco Honório Araújo 30 September 2011 (has links)
A proposta deste trabalho é de analisar o comprometimento organizacional dos funcionários de uma empresa metalúrgica de Caxias do sul. Esta empresa em análise é a Cemar Legrand empresa pertencente ao Grupo Legrand (Grupo Multinacional Francês). Foi utilizado para a análise um instrumento de pesquisa com reconhecimento pela comunidade científica chamado de modelo dos três componentes de Allen e Meyer (1997) , modelo que caracteriza o comprometimento organizacional em suas dimensões afetivo, instrumental e normativo, e foi aplicado o questionário em uma amostra de 311 funcionários da empresa. A análise deste trabalho também foi ampliada no sentido analisar este comprometimento organizacional por grupo de funcionários pertencentes às gerações (Geração Veteranos, Geração Baby boomers, Geração X e Geração Y), esta teoria das gerações, tem seu nascedouro na teoria geracional de Strauss e Howe (1991) onde os autores definem que em cada século há quatro gerações distintas e que cada uma das gerações comportam-se conforme as características de cada período geracional, bem como pelos acontecimentos de sua época. O resultado deste trabalho demonstra que há um bom comprometimento dos funcionários para com a empresa e não foi encontrado diferenças entre as dimensões do comprometimento para as gerações pesquisadas. / The purpose of this study is to examine organizational commitment of employees at a metallurgical company in Caxias do Sul. This company in question is Cemar Legrand company belonging to Legrand Group. Was used to analyze a research tool to recognize the scientific community called "model of the three components of Allen and Meyer (1997)," model that characterizes the organizational commitment in their affective, instrumental and normative dimensions, and the questionnaire was applied in a sample of 311 employees. This analysis has also been expanded in order to analyze organizational commitment by this group of employees through the theory of generations (Generation Veterans, Generation Baby Boomers, Generation X and Generation Y), this theory of generations, has its origin in the theory of generational Strauss and Howe (1991) where the authors define it in every century there are four different generations and each generation behaves according to the characteristics of each generational period, as well as by the events of his time. This investigation demonstrates that there is a good employee commitment to the company and was not found differences between the dimensions of commitment for the four generations surveyed.
280

Caracterizações microestruturais e avaliações das propriedades mecânicas das juntas em aço inoxidável AISI 301 L soldadas por MIG e submetidas ao reparo pelo processo TIG / Microstructural characterization and evaluation of mechanical properties of joints in steel AISI 301 L welded by MIG and submitted to repair by TIG process

SOUZA, EDVALDO R. de 11 November 2016 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T09:40:30Z No. of bitstreams: 0 / Made available in DSpace on 2016-11-11T09:40:30Z (GMT). No. of bitstreams: 0 / A soldagem tem grande importância no setor metroferroviário, pois é empregada na fabricação de componentes estruturais e no acabamento de vagões de passageiros, que em sua maior parte são de aço inoxidável. As juntas soldadas podem apresentar descontinuidades que são interrupções que afetam as propriedades mecânicas e metalúrgicas da junta soldada. A presença destas descontinuidades, dependendo do seu tamanho, natureza ou efeito combinado, pode ocasionar a reprovação da junta soldada, quer pela redução de propriedades mecânicas ou pela não aceitação, segundo critérios estabelecidos em normas. Uma estrutura que tenha uma solda reprovada durante sua qualificação ou inspeção, pela presença de descontinuidades pode ser recuperada, por meio de um retrabalho a ser realizado nesta junta. A refusão do cordão de solda por meio do processo TIG (Tungsten Inert Gas), sem a utilização do material de adição, é uma técnica de retrabalho que pode ser empregada, em especial pela viabilidade técnica e econômica do processo. Neste estudo analisou-se a influência que o processo de reparo por soldagem TIG exerceu no comportamento mecânico e microestrutural das juntas soldadas pelo processo MIG, por meio de: ensaios mecânicos (tração, fadiga e microdureza Vickers), ensaios não destrutivos (inspeção visual e líquidos penetrantes) e caracterização microestrutural do cordão de solda. Resultados das amostras de ensaio de tração e fadiga indicaram que o reparo dos cordões de solda não alterou o comportamento mecânico das juntas. As juntas submetidas ao reparo nas quais foram retirados os reforços dos cordões apresentaram modificações nas propriedades mecânicas, mas também apresentaram resultados satisfatórios. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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