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1
Nabeel, Muhammad. "Diffusion of Elemental Additives during Sintering." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100702.
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The mechanical properties of components made by PM steels are normally inferior to those made by alternative processes. One of the main reasons is that a large amount of pores are present in sintered components. The other main reason is that the alloying elements, particularly Ni, are not uniformly distributed after conventional sintering procedures. This work is aimed at a better understanding of the influence of alloying additions on mechanical properties and homogeneity of the microstructure. The experimental work has been carried out in two trials. Trial 1 was performed to investigate mechanical properties of Distaloy powders (commercial grades) and second trial to examine influence of alloying additions on homogeneity of microstructure. For trial 1, as-sintered and heat treated specimens were produced by mixing commercial powders with two different carbon levels. Whereas, alloying elements were admixed to base iron powder for producing sintered specimens for trial 2. Mechanical properties including dimensional changes, micro-hardness, tensile strength and impact resistance were measured. Distribution of alloying elements was studied using LOM and SEM-EDS analysis. The results obtained show that additions of alloying elements enhance the mechanical properties. Moreover, interaction of C with Cu and Ni as well as interaction between Cu and Ni have a deceive role in determining final properties of the components. The metallographic investigation indicated that major reasons of heterogeneous microstructure are slow diffusion of Ni in Fe matrix and interaction of other alloying elements with Ni. The results of trial 2 showed that addition of Mo and Cu to Ni-containing PM steels improves the distribution of Ni in Fe matrix. Mo results in improved uniformity of microstructure by lowering the chemical potential of carbon. In Ni and Cu containing alloys, the interaction between Ni and Cu is responsible for enhanced distribution of Ni. However, the improved Ni distribution is achieved at the expense of non-uniform distribution of Cu. In Ni-containing PM steels, improved microstructure homogenization can be attained by increasing Ni-Cu interaction, lowering the surface energy of Ni-Cu liquid and decreasing the chemical potential of carbon.
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Clinning, Nicholas. "Thermomechanical processing of blended elemental powder Ti-6Al-4V alloy." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/4968.
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Includes abstract.Includes bibliographical references.
This research investigates the feasibility of producing Ti-6Al-4V products by creating low cost BE sintered preforms and then subjecting these preforms to thermomechanical processing (TMP) in an attempt to both improve the relative density and refine the microstructure. The powders used were direct reduction titanium powder and elemental aluminium and vanadium powders.
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Karimzadeh, F., M. T. Asnaashari, M. H. Enayati, and M. Salehi. "Formation of Nanostructured Al-Mg-Si Alloys and Evaluation Its Properties." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34869.
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In this study, nanostructured Al-Mg-Si (Al6061) alloy was prepared from elemental powders by mechanical alloying and heat treatment. 98.4% aluminum, 1% magnesium, 0.6% silicon powders were mixed
and mechanically alloyed under argon atmosphere. The rotation speed of 500rpm and ball to powder ratio
of 10:1 was employed. The mechanical alloyed powder was isothermally heat treated at 400 degrees Celsius for 2 h under argon atmosphere.
The results showed that after 10h of milling, a solid solution of Al-Mg-Si with a grain size of ~ 40 nm
was produced. The as milled and annealed powder was characterized by scanning electron microscopy
(SEM) and X-ray diffraction (XRD). The microhardness values of alloy increase by increasing MA time.
Mg2Si particles precipitate from solid solution during subsequent annealing. The as milled powder
appeared to have good thermal stability against grain growth so that the grain size after annealing
remained constant (~ 40 nm).
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34869
4
Hoffman, Tricia Marie. "The Use of Elemental Databases in Forensic Science: Studies on Vehicle Glass Interpretation and Milk Powder Provenancing." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3812.
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The first study focuses on the development of a laser based method for the elemental analysis of solid milk powder. Milk powder samples originating from five different countries were analyzed to determine any geographic differences. A LA-ICP-MS method was developed and compared to k0-INAA for several milk samples as well as a reference sample. Precision of 10% RSD or better and a bias of 10% was achieved for both techniques for most elements with LA-ICP-MS producing lower limits of detection (~ 1 ppm) for Sr. The comparison of LA-ICP-MS to k0-INAA showed overlap of the 95% confidence intervals for all comparison samples. The data for 68 authentic milk powder samples representing 5 different countries (Argentina, Russia, Singapore, Slovenia, and the United States) was collected and used as a preliminary database. Principle component analysis (PCA) shows different groupings for the United States, Argentina, Singapore, and Slovenia. However the large number and geographic distribution of samples from Russia were not able to be distinguished from the samples from the United States and Slovenia.
The second study focuses on the use of trace element databases for the objective interpretation of forensic glass evidence. Ten laboratories conducting analysis of glass participated in three inter-laboratory exercises. The aims of these exercises were to evaluate the use of a standard method for the analysis and comparison of glass evidence and to investigate different statistical approaches for interpreting results. Elemental analysis was performed on 420 vehicle windshield samples collected from 210 different vehicles representing manufacturing dates between 2004-2017 and 26 vehicle manufacturers. Using a variation of a previously reported comparison criterion for comparing samples to a database, the false exclusion rate and false inclusion rate for the new vehicle database were calculated to be 1.9% and 0.1 % respectively. This criterion was used to calculate the frequency of an elemental profile for the case scenarios distributed as part of the inter-laboratory exercises. Similarities were observed between labs that calibrated their data the same way, thus showing it is possible for labs to use a central database.
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Naicker, Hiranya. "Parametric study on the compactibility of Ti-6Al-4V during direct powder rolling." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31009.
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The widespread use of titanium and its alloys in structural applications has been limited to few highend applications. The dominant reason for this being cost implications. These high costs arise from extracting titanium from its mineral form as well as that of the manufacturing processes to develop a final product. Since producing titanium products includes expensive starting stock, high machinability costs and high wastage, a need for a process that may minimize one or more of these factors is necessary. One such technology that exists is a branch of powder metallurgy (PM), direct powder rolling (DPR) which allows for a continuous approach to produce strip or sheet metal. Products developed by this process are however known to possess inferior properties to its wrought counterpart. The present study comprises of a parametric study observing how two different blends of powder differ in the development of Ti-6Al-4V strip by employing the blended elemental (BE) approach to direct powder rolling. The objectives of this work include predicting the compaction behavior of the two respective blends during powder rolling to inform the production of high density green strip and to compare the outcomes of the prediction method to experimentally determined results using a gravity-fed laboratory-scale rolling mill with roll diameter of 265 mm and roll width of 150 mm. Johanson’s rolling theory was applied to predict rolling outcomes and a fixed set of rolling parameters were implemented for the simulation and experimental segment of this dissertation. The two blends being investigated include blending titanium powder with an elemental blend consisting of aluminium and vanadium powders (B1) and a master alloy blend of a 60Al-40V master alloy (B2). These two blends were used to validate the Johanson simulated rolling data. Fixed parameters applied to the rolling mill included using a roll speed of 14 rpm, roll face width of 65 mm and gravity-fed hopper outlet diameter of 25 mm. Variable roll gaps of 0.5, 1 and 1.5 mm were studied. Average relative green densities of B1 and B2 strips achieved at a roll gap of 1 mm were 77% and 73% respectively. Rolling performance of the B1 powder blend were higher than that of B2, reaching higher green densities and showing superior formability, as rolling at smaller roll gaps was achievable for B1 and not B2. Green strength of B1 and B2 strips at a roll gap of 1 mm reflected similar outcomes where B1 strips required a greater breaking load to fracture samples when compared to B2 indicating a stronger self-supporting compact. Furthermore, the Johanson rolling model proved to overestimate reasonable roll pressure values, although, the general trend of compactibility between B1 and B2 powder blends was reasonably predicted showing B1 to be more compressible than B2 during powder rolling. iv Subsequent sintering at 1200 °C for 3 hours in a vacuum environment was applied to green strips to further densify and homogenize strips. Average relative sintered densities achieved for B1 and B2 strips rolled at a roll gap of 1 mm were 78% and 87% respectively. While green densities of B1 strips were higher than that of B2 strips, it was evident that the addition of the 60Al-40V master alloy to blend B2 resulted in superior sinterability as final sintered densities surpassed that of B1, even when starting at a lower green density after rolling. SEM/EDX was used to evaluate what effect sintering had on homogenization. A standard wrought Ti-6Al-4V specimen was used as the benchmark to compare homogenization results. B2 strips homogenized more than B1 strips when comparing to the baseline wrought sample. It was concluded that both B1 and B2 powders used to create Ti-6Al-4V strip by direct powder rolling (DPR) exhibited high levels of porosity and a subsequent step is necessary to fully densify the material. While B1 strips exhibit superior rollability with higher green densities and green strength; after applying a sintering practice to both B1 and B2 strips, B2 sintered densities surpassed those of B1 and prove to homogenize to a greater degree than B1 strips. The superior roll compaction ability and inferior sinterability for B1 powders was attributed to the elemental powder, aluminium. While the addition of ductile aluminium to B1 aids roll compaction, its low melting point results in large pores evolving at sintering temperatures almost twice its melting point.
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Farias, Iria Luiza Gomes. "COMPRIMIDOS MASTIGÁVEIS DE FERRO CARBONILA PARA TRATAMENTO DA ANEMIA FERROPRIVA DE CRIANÇAS MENORES DE SEIS ANOS." Universidade Federal de Santa Maria, 2006. http://repositorio.ufsm.br/handle/1/5907.
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The objective this study is verify the efficiency and occurrence of collateral effects with the use of carbonyl iron powder, in the form of chewable tablets, in order to enable the use of an alternative to the conventional treatment of iron deficiency anemia with ferrous sulfate, for children under 6 years of age. The intervention proposed for the treatment of iron deficiency anemia in children almost always consists of ferrous sulfate drops that do not have the desired effectiveness. Several studies have proven the low adherence to the treatment due to collateral effects of the medication (gastrointestinal intolerance, alterations in color and consistency of stools, impregnation of iron in diapers and teeth), to the prolonged daily administration in the form of drops, to the metallic taste, as well as to socio-cultural aspects. In choosing the preparation, the content of the iron ion, tolerance, absorption, effectiveness and cost must all be considered. Carbonyl iron powder is obtained by decomposition of Fe pentacarbonyl at high temperatures, resulting in extremely pure elemental Fe (Fe0), in the
form of non-toxic micro-spheres of 4-7/μm, with bioavailability in relation to 58-70% ferrous sulfate and it does not confer a metallic taste to the preparation. An open randomized clinical assay was carried out. The group studied (CA) received Carbonyl Iron and the control group (SF) received a solution of Ferrous Sulfate, both at a dose of 5mg/Kg/day, for 90 days. Seventy-three children from Family Health Units (FHU) of Santa Maria, Brazil, participated in the study. Blood was collected at 0, 30 and 90 days of treatment. The hemograms were carried out in STKS (Coulter, USA), serum iron and TIBC, by colorimetric assay and ferritin by immunometric assay. The data was analyzed with the EpiInfo program, version 3.3.2, from CDC/USA. The increase in Hb after 30 days of treatment was of 1.3g/dl (SD 0.92) for group CA and of 1.2g/dl (SD 1.13) for group SF (p>0.05). After 90 days of treatment, CA had favorable results for Ht, MCV, MCH, TIBC and ferritin (p<0.05). None of the children from group CA presented side effects, in group SF, 62% of the children presented diarrhea and/or experienced vomiting. The number of children from the control group who continued to present a level of Hb lower than 11g/dl was two-fold that of the group that received carbonyl iron. Based on the results demonstrating the same effectiveness at 30 days as for the standard ferrous sulfate and the superior results at 90 days of treatment, together with the safety (low toxicity) and excellent acceptance, carbonyl iron should be considered an important option for the therapeutic treatment of iron deficiency anemia in children under the age of six.O objetivo deste estudo é verificar a eficácia, ocorrência de efeitos colaterais e aceitação de ferro carbonila em pó, na forma de comprimidos mastigáveis, para possibilitar uma alternativa ao tratamento convencional da anemia ferropriva com sulfato ferroso, para crianças menores de seis anos. A intervenção proposta para tratamento da anemia ferropriva de crianças, quase na totalidade das vezes, consiste em gotas de sulfato ferroso que não tem tido efetividade desejada. Vários estudos comprovam a baixa adesão ao tratamento em virtude dos efeitos colaterais do medicamento (intolerância gastrintestinal, alterações na cor e consistência das fezes, impregnação de ferro nas fraldas e dentes), do esquema de administração em dose diária por tempo prolongado, do sabor metálico do medicamento, além de aspectos socioculturais. Na escolha do preparado, deve ser considerado o conteúdo do íon ferro, tolerância, absorção intestinal, eficácia e custo. O ferro carbonila em pó é obtido pela decomposição a altas temperaturas do ferro pentacarbonil, resultando em ferro elementar (Fe0) extremamente puro, em forma de micro-esferas de 4-7/μm, com boa biodisponibilidade, não tóxico e sem conferir sabor metálico às preparações. O desenho do estudo foi um ensaio clínico, randomizado, aberto. O grupo estudo (CA) recebeu comprimidos mastigáveis de Ferro Carbonila; o grupo controle (SF) recebeu solução de Sulfato Ferroso, na dose de 5mg/Kg/dia, por 90 dias. Participaram do estudo 73 crianças com diagnóstico comprovado de anemia ferropriva, atendidas em USFs de Santa Maria, RS. Foram realizadas coletas de sangue nos tempos 0, 30 e 90 dias de tratamento. Os hemogramas foram realizados em STKS Coulter, Ferro sérico e Capacidade Total de Ligação do Ferro, por química úmida (colorimetria) e Ferritina por quimioluminescência, todos por automação. Os dados analisados com programa EpiInfo, versão 3.3.2, do CDC/USA. O incremento de Hb após 30 dias de tratamento foi de 1,3g/dl (dp 0,92) no grupo CA e 1,2g/dl (dp 1,13) no grupo SF (p>0,05). Após 90 dias de tratamento, as médias do Ht, VCM, HCM, CTLF e ferritina são significativamente melhores no grupo CA (p<0,005). Nenhuma criança do grupo CA apresentou efeitos colaterais. No grupo SF, 62% tiveram diarréia e/ou vômito. O número de crianças que permanecia com Hb < 11g/dl, no grupo controle, era o dobro do que no grupo recebendo ferro carbonila. Pelos resultados de eficácia em 30 dias similares ao padrão sulfato ferroso e a superioridade em 90 dias de tratamento, aliados a segurança (baixa toxicidade) e ótima aceitação, o ferro carbonila deve ser considerado como uma importante opção terapêutica para tratamento da anemia ferropriva, de crianças menores de seis anos de idade.
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Belsito, Danielle L. "Application of Computational Thermodynamic and Solidification Kinetics to Cold Sprayable Powder Alloy Design." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/28.
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Military aircraft that require high maneuverability, durability, ballistic protection, reparability, and energy efficiency require structural alloys with low density, high toughness, and high strength. Also, repairs to these aircraft demand a production process that has the flexibility to be relatively in-situ with the same high-performance output. Materials produced by the cold spray process, a thermo-mechanical powder consolidation technique, meet many of the requirements. In accordance with President Obama’s 2011 Materials Genome Initiative, the focus of this effort is to design customized aluminum alloy powders which exploit the unique behavior and properties of the materials created by the cold spray process. Analytical and computational models are used to customize microchemistry, thermal conditioning, and solidification behavior of the powders by predicting equilibrium and non-equilibrium microstructure and resulting materials properties and performance. Thermodynamic, kinetic, and solidification models are used, including commercial software packages Thermo-Calc, Pandat™, and JMatPro®, and TC-PRISMA. Predicted powder properties can be used as input into a cold spray process impact model to determine the consolidated materials’ properties. Mechanical properties of powder particles are predicted as a function of powder particle diameter and are compared to experimental results.
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Ezenwa, Emmanuel. "N,N-diethyl-N'-naphthoylacylchalcogourea to metal (II)complexes as precursors for ternary metal chalcogenide thin films via AACVD." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/nndiethylnnaphthoylacylchalcogoureatometal-iicomplexes-as-precursors-for-ternary-metal-chalcogenide-thin-films-via-aacvd(85420a4c-89d4-4465-9734-ca40a75ba924).html.
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In this thesis complexes of acylchalcogoureas with cadmium (II), lead (II) and nickel (II) have been synthesised and investigated as single source precursors for the formation of metal chalcogenide thin films viaaerosol assisted chemical vapour deposition (AACVD). Routes to binary thin films have been explored using homoleptic complexes of the general structure bis(N,N-diethyl-N'-naphthoylchalcogoureato)metal(II). Analysis of the thin films produced showed the successful deposition of the binary materials from the synthesised complexes when characterised by powder XRD, ICP-OES, SEM and EDX. Routes to ternary thin films with the general structure MExE'1-x, where M represents a metal (Cd, Ni and Pb); and E chalcogen (S or Se) have been investigated using heteroleptic metal complexes of cadmium, nickel or lead including different chalcogen containing N,N-diethyl-N'-naphthoylchalcogoureato ligands and diethyldithiocarbamate. The precursors were fully characterised and novel compounds had their crystal structures determined. The heteroleptic complexes were thermolysed by AACVD forming the MExE'1-x thin films. In the cases of lead, nickel and cadmium the thin films produced showed that the composition of the film tended heavily towards the metal selenide. Ternary films of type MS1-xSex was prepared by mixing their binary precursors of type bis(N,N-diethyl-N'-naphthoylselenoureato)metal(II) and bis(N,N-diethyl-N'-naphthoylthioureato)metal(II) [metal = Cd, Ni and Pb]. In the case of lead and cadmium chalcogenide films variation of the ratio of sulphur and selenium containing precursors allowed for the full transition in composition between metal sulphide and metal selenide. In the case of CdS1-xSexthe band gap of the films was determined from UV-visible spectroscopy to vary from 2.4 eV (CdS) to 1.7 eV(CdSe). In the case of NiS1-xSex the movement from sulphide to selenide was less simple with multiple phases of nickel chalcogenides produced.
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Santana, Sobrinho Antonio. "Elementos da teoria de poder em Michel Foucault." Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/5598.
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The concept of power is necessarily an analysis in historical time and, especially in the currents of thinking which are mentioned by different authors who discuss about this issue. This work constitutes a reflection exercise concerning Michel Foucault s perception about the meaning of power. Nevertheless, it is essential to state that Michel Foucault never discussed about power as a coherent, unique and stable entity, but as power relations . Therefore, the question regarding power is inseparable and it constitutes a theme established in his thought. On the other hand, understanding the mechanism by which the social relations are founded, with emphasis on inequalities of domination and obedience relations that favor authority and the nature of political obligations constitutes a constant work of human thinking. Our analysis seeks to perceive the historiography and the definition of power for Michel Foucault and what are the central points of his idea. Constructing a new way of power by presenting new principles as locality, exteriority, transitoriness and non-ideologization breaking with the traditional view of power and with the sign of abandonment of this theory, he named his position as analytics of power.
O conceito de poder é necessariamente uma análise no tempo histórico e, sobretudo, nas correntes de pensamentos que são abordadas pelos diferentes autores que discutem essa temática. Este trabalho configura-se como um exercício de reflexão a respeito da percepção de Michel Foucault sobre o sentido de poder. Porém, é necessário afirmar que Michel Foucault nunca discutiu o tema poder como uma entidade coerente, única e estável, mas como relações de poder . Portanto, a questão do poder é indissociável e constitui um tema enraizado em seu pensamento. Por sua vez, compreender o mecanismo pelo qual se sustentam as relações sociais, em destaque, as desigualdades de relação de dominação e obediência que dão razão à autoridade e à natureza das obrigações políticas, constitui-se um trabalho constante do pensamento humano. A nossa análise procura perceber a historiografia e definição do poder para Michel Foucault e quais os pontos centrais da sua ideia. Construindo uma nova forma de poder, apresentando novos princípios como localidade, exterioridade, transitoriedade e não ideologização, rompendo com a visão tradicional do poder e com o signo do abandono dessa teoria, ele denominou sua posição de analítica do poder.
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Katrue, Srikanth. "Power reduction techniques for memory elements /." Online version of thesis, 2007. http://hdl.handle.net/1850/5720.
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Ramakrishnan, Ramanath I. "A methodology for the simulation of non-isothermal and canned extrusion of metal powders using finite element method." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182457475.
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Kaushik, Anshul. "Analysis of powder compaction process through equal channel angular extrusion." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2540.
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Protsenko, Z. М. "Technology Features an Electrochemical Obtain Powdered Zirconium." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35512.
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The work is devoted to technology electrochemical obtain powder of zirconium ion fluoride melts (set-ting parameters of the electrolysis method of washing powder Zr impurities from salt mixture components) on different substrates. Phase and element composition and cell size distribution of powdered zirconium was investigated.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35512
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Fernandes, Rodolfo Castanho. "Elementos magnéticos fracamente acoplados para aplicação em transferência indutiva de potência: procedimento e critérios de projeto, análise de sensibilidade e condições de bifurcação." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-28092015-164437/.
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Além da transferência de energia elétrica por meio de condutores sólidos que interligam carga e fonte elétrica, existem formas alternativas que, por não necessitarem de conexão mecânica, permitem maior mobilidade espacial para a carga e trazem inúmeras novas possibilidades de aplicação. Dentre estas formas alternativas está a Transferência Indutiva de Potência, que possui desafios claros no que diz respeito ao projeto do sistema magnético formado pelos indutores emissor e receptor, quando entre eles existe acoplamento magnético muito reduzido. A retirada do núcleo magnético sólido entre emissor e receptor confere a possibilidade de o receptor se mover em relação ao emissor, o que permite a transferência de potência a uma carga móvel. Contudo, o baixo coeficiente de acoplamento magnético torna o sistema fracamente acoplado sensível a variações tanto no circuito ressonante que o alimenta quanto na própria geometria magnética, onde pequenas modificações dimensionais resultam em significativos ganhos de potência no receptor. Esta tese apresenta inicialmente um conjunto de rotinas computacionais que agilizam o projeto de sistemas fracamente acoplados contendo emissores e receptores circulares ou espirais. Estas rotinas agem como pré e pós-processadores do Método dos Elementos Finitos, que por sua vez é solucionado por um aplicativo bidimensional gratuito. Com esta abordagem, é possível desenvolver rapidamente acopladores magnéticos com parâmetros realísticos, cuja montagem experimental demonstra excelente conformidade com os resultados teóricos. Um grupo de onze acopladores magnéticos diferentes é avaliado nesta tese como demonstração de que a otimização de parâmetros geométricos é relevante para a maximização de potência no receptor. Compara-se também o desempenho de acopladores Bipolar, Duplo D e Duplo D Quadratura. Após evidenciar relações geométricas e magnéticas para os diversos acopladores, verifica-se por meio de estudos de sensibilidade paramétrica, que não apenas a geometria do sistema fracamente acoplado influencia em seu desempenho, mas também a escolha dos parâmetros das malhas ressonantes conectadas ao emissor e ao receptor. Disto se conclui sobre a importância da Análise de Sensibilidade em Transferência Indutiva de Potência, pois, como demonstrado, certas malhas ressonantes são naturalmente mais tolerantes a variações do coeficiente de acoplamento magnético do que outras, por exemplo, aquelas em que há compensação do tipo paralelo no emissor. Por fim, o trabalho dedica-se ao estabelecimento de critérios para a ocorrência do fenômeno de bifurcação, segundo o qual múltiplas frequências de ressonância podem ocorrem em um conversor em frequência variável, a depender da carga conectada ao receptor e dos fatores de qualidade dos indutores. O equacionamento, obtido numericamente e que foi generalizado para casos em que existem múltiplos receptores, permite boa previsibilidade a respeito do comportamento dinâmico de sistemas variáveis em frequência.In addition to the transfer of electrical energy by means of solid conductors that interconnect electrical source and load, there are alternative ways that does not require mechanical connection and allow spatial mobility to the load bringing numerous new application possibilities. Among these alternative forms is Inductive Power Transfer, which has clear challenges with respect to the magnetic system design formed by emitter and receiver inductors, since there is very little magnetic coupling between them. The removal of the solid magnetic core between emitter and receiver introduces the possibility of moving receivers. However, the low magnetic coupling coefficient makes the loosely coupled system sensitive to variations in both the resonant circuit parameters and the magnetic geometry, where small dimensional changes result in significant power gains in the receiver. This thesis initially presents a set of computing routines that allows the design of loosely coupled systems containing circular or spiral inductors. These routines act as pre- and post-processors for Finite Element Method, which in turn is solved by a free two-dimensional application. With this approach one can quickly develop magnetic couplers with realistic parameters, which is demonstrated by comparison between experimental and theoretical results. A group of eleven different magnetic couplers is evaluated as a proof that the optimization of geometric parameters is relevant to maximizing the power of the receiver. Moreover, the performance of Bipolar, Double D and Double D Quadrature couplers are studied. Later, it is verified by means of parametric sensitivity analysis that not only the geometry of the loosely coupled system influences its performance, but also the choice of the parameters of the resonant converters connected to emitter and receiver. The sensitivity analysis of Inductive Power Transfer converters was found to be of great importance because, as shown by a numerical example, certain resonant topologies can be naturally more tolerant to variations in the magnetic coupling coefficient than others. Finally, the work is dedicated to the establishment of precise criteria for the occurrence of bifurcation phenomenon whereby multiple resonant frequencies can occur in a converter under variable frequency excitation, depending on the load connected to the receiver and the quality factors of inductors. The equations obtained numerically were generalized for cases where there are multiple receivers and allow good predictability about the dynamic behavior of variable frequency systems.
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Chan, Sui Yan. "Resonance-enhanced laser-induced plasma spectroscopy for elemental analysis." HKBU Institutional Repository, 1999. http://repository.hkbu.edu.hk/etd_ra/184.
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Anpalahan, Peethamparam. "Design of transverse flux machines using analytical calculations&finite element Analysis." Licentiate thesis, KTH, Electrical Systems, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1227.
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Burrow, Stephen George. "Low power, high efficiency Class D amplifiers." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271779.
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Hoi, Loison. "Cosmological inflation and the primordial power spectrum." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92301.
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Ceccacci, Margaret. "Power strategies used by elementary school principals as perceived by elementary school teachers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0012/MQ52450.pdf.
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Golubev, Alexey. "Elemental materialism : objectifying power and selfhood in the late USSR, 1961–1991." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57465.
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This dissertation explores the link between materiality and individual and collective selves in late Soviet society. Focusing on material objects ranging from space rockets to heritage buildings to weightlifting equipment to TV sets, it argues that material objects in late socialism were key elements in the organization of the Soviet historical and spatial imagination. They embodied various, often contrasting social techniques and understandings of time and space, and acted as material coordinates of the Soviet self.
The central concept of this dissertation is elemental materialism, by which I mean a culturally rooted recognition of the power of matter and things to shape human bodies and selves, a prominent feature in the Soviet system of signification which regulated the production of meanings on daily basis. Soviet elemental materialism was a social reaction to pre-ideological experiences of daily life, including entangled assemblages of bodies, objects and physical space which exercised a social agency that did not originate from the dominant Soviet ideology. It was a set of spontaneous and situational cultural forms which gave Soviet people ways of making sense of the social agency of things. At the same time, my research historicizes Soviet things and material space in their spontaneity and affectivity as actual agents of historical change in the late USSR on a par with people, social institutions, and ideologies. By tracing the biographies of Soviet things and spatial constructions, I demonstrate how the material world of late Soviet period determined people’s habitual choices, social trajectories, and imaginary aspirations.
This research contributes to several key debates in Soviet history including how the Soviet state fashioned its citizens into subjects, and how Soviet people embraced and questioned the dominant paradigms of selfhood. My study of social reactions to the recognition of the power of things over people – that is, elemental materialism of Soviet society – contributes to a better understanding of cultural logic of late socialism. In a broader context, my research contributes to the debates on how we as historians should conceptualize the role of objects in history.Arts, Faculty of
History, Department of
Graduate
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Warke, Virendra S. "Predicting the response of powder metallurgy steel components to heat treatment." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-072808-100705/.
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Simonavičienė, Laura. "Vertinamieji elementai ir jų raiška interneto žiniasklaidoje: IAE uždarymo atvejo analizė." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100615_155442-03831.
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Naujausi tyrimai rodo, o ir kiekvienas informacijos gavėjas pastebi, kad informacijos teikėjas labai dažnai nesugeba atsiriboti nuo subjektyvumo. Taip atsitinka todėl, kad kiekvienas informacijos koduotojas turi skirtingus patyrimus, interesus, įvairias nuomones apie įvykius, jį supantį pasaulį, požiūrį į vieną ar kitą situaciją, dalyką ir pan.
Tyrimo tikslas – atpažinti žiniasklaidos tekste vartojamus vertinamuosius elementus, suklasifikuoti juos ir aprašyti, kaip, pasitelkus vertinamuosius elementus, atspindima autoriaus pozicija, požiūris, nuomonė apie žinomą įvykį, realų faktą ar įvykusią situaciją. Šio mokslinio darbo objektas – vertinamieji elementai, vartojami Lietuvos interneto žiniasklaidos tekstuose. Siekiant užsibrėžto tikslo buvo numatyti 6 uždaviniai, apibendrintai jie yra tokie: apžvelgti atliktus mokslinius tyrimus ir jų rezultatus bei metodus pritaikyti lietuvių kalbos interneto žiniasklaidos tekstuose vartojamiems vertinamiesiems elementams tyrinėti; pagal sudarytą pagrindinių ir šalutinių vertinamųjų parametrų schemą atpažinti, suklasifikuoti vertinamuosius elementus, juos išanalizuoti ir aprašyti; pristatyti darbo metu kilusias problemas ir sunkumus, ypač susijusius su vertinamųjų elementų atpažinimu; atlikti apklausą-eksperimentą ir aptarti rezultatus.
Atlikus vertinamųjų elementų, vartojamų interneto žiniasklaidos tekstuose, tyrimą, patvirtinta kelta hipotezė, kad pasitelkęs vertinamuosius elementus teksto autorius gali perteikti asmeninę poziciją... [toliau žr. visą tekstą]Both the latest studies and the opinion of information receivers show that information providers are often unable to distance themselves from subjectivity. This happens because every information addresser has particular experiences and interests, various opinions about the events and environment, different view to one or another situation, and etc. The aim of the thesis is to identify the evaluative elements used in media discourse, to classify them and, with the help of evaluative elements, to describe how author’s position on the event, actual fact or situation is reflected. The object of this work is the evaluative elements, used in the texts of Lithuanian media websites. In order to achieve the object, six tasks were set: to overview the carried out scientific researches and their results and to adapt the methods to the exploration of evaluative elements used in the texts of Lithuanian media websites; to identify, classify, then analyze and describe evaluative parameters, according to the main and secondary evaluative parameters scheme; to present problems and challenges arisen, particularly those related to evaluative elements recognition; to carry out an experiment-survey and to discuss the results. After a study of evaluative elements used the discourses of media websites, the following the hypothesis was confirmed: with the help of evaluative elements, the author of the text can convey a personal attitude and shape reader’s opinion. There are various categories to... [to full text]
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Bier, Wolfgang. "A constitutive model for metal powder and its numerical treatment using finite elements." Kassel Kassel Univ. Press, 2007. http://d-nb.info/988736829/04.
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Kamps, Timothy James. "The biblical forms and elements of power encounter." Theological Research Exchange Network (TREN), 1986. http://www.tren.com.
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Mazer, Thiago Tazinazzo [UNESP]. "Cálculo em elementos finitos das frequências naturais dos modos de flexão de uma linha de eixo de unidade geradora hidráulica em escala." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/136448.
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A evolução das unidades geradoras hidráulicas é constante, sempre visando a redução de custos, mantendo ou melhorando os fatores de desempenho já alcançados. Em consequência disso têm-se em geral máquinas menores, com velocidade de rotação mais elevada e maiores solicitações mecânicas, além de estruturas com massa otimizada e consequentemente mais flexíveis. Nesse contexto, conhecer o comportamento dinâmico dos rotores das turbinas hidráulicas e ter a capacidade de simulá-los com precisão passa a ser fundamental. No presente estudo é desenvolvido um modelo em escala representativo de uma linha de eixo rotativo de turbina hidráulica de grande porte com o objetivo de avaliar o seu comportamento dinâmico, permitindo que os resultados teóricos possam ser comparados com resultados experimentais, este último não faz parte do escopo do presente trabalho. Em uma primeira etapa as dimensões do modelo em escala são determinadas por uma análise dimensional, que permite elaborar os desenhos tanto do rotor quanto de seus suportes. Os parâmetros de rigidez dos suportes são então determinados por meio de análise estrutural estática em elementos finitos (EF). Esses parâmetros são utilizados então na análise dinâmica do rotor, também em EF, permitindo obter o diagrama de Campbell (frequências naturais e seus respectivos modos em função da rotação do eixo) e a resposta harmônica ao desbalanceamento. Diferentes valores de amortecimento e desbalanceamento são assumidos nessa análise, e suas influências no comportamento dinâmico do rotor são avaliadas e discutidas. Também são avaliados os efeitos da estrutura base que suporta os mancais (fundação) na dinâmica da máquina rotativa como um todo. Por fim uma bancada experimental foi construída, sendo que a análise experimental fica como proposta para trabalhos futuros.
The evolution of hydro power units is constant, always aiming to reduce costs while maintaining or improving performance already achieved. Consequently the sizes of the components have being reduced, while rotational speed and mechanical stresses have being increased. Also, supporting structures have being optimized in weight, becoming more flexible. In this context, it is crucial to know the dynamic behavior of the rotors of hydro power units and to have the ability to simulate them accurately. In this study a representative model of a large hydro power rotor is developed in order to evaluate its dynamic behavior, allowing the comparison between theoretical results with experimental results, the latter is not part of scope of this work. In a first stage the scale model geometry is determined by a dimensional analysis, which allows elaborate the designs of the scaled rotor and its supports. The supports stiffness parameters are then determined by static structural finite element analysis (FEA). These parameters are used in rotor dynamic analysis, also in FEA, enabling the construction of Campbell diagram (natural frequencies and their respective modes shaft rotation function) and the harmonic response to unbalance. Different values of damping and unbalance are assumed in these analyses, and their influence on the rotor dynamic behavior are evaluated and discussed. The effects of the base structure supporting the bearings (also known as foundation) on the dynamics of the rotating machine as a whole are also evaluated. Finally an experimental bench was built, however the experimental analysis is proposed for future work.
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Bier, Wolfgang. "A constitutive model for metal powder and its numerical treatment using finite elements." Kassel : Kassel Univ. Press, 2008. http://d-nb.info/989607917/34.
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Skrinjar, Olle. "Cold compaction of composite powders." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-417.
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Xin, Mei. "Interaction of atmospheric elemental mercury with natural, synthetic, and anthropogenically derived substrates." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3289450.
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Majule, Amos Enock. "The effects of organic residues and elemental sulphur additions to soils of southern Tanzania." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287642.
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Tang, Yousin. "Power system stability in the presence of FACTS elements." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/13432.
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Karadag, Rukiye. "Temperature Distribution In Power Transformers." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615162/index.pdf.
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As in all other electrical equipments it is essential to estimate the temperature distribution in transformer components in the design stage and during the operation since temperatures above thermal limits of these components might seriously damage them. Thermal models are used to predict this vital information prior to actual operations. In this study, a three dimensional model based on the Finite Element Method (FEM) is proposed to estimate the temperature distribution in the three phase, SF6 gas insulated-cooled power transformer. This model can predict the temperature distribution at the specific discredited locations in the transformer successfully.
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Calil, Wílerson Venceslau. "Determinação do fator de correção para cálculo de perdas magnéticas em núcleos de transformadores de potência pelo método de elementos finitos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-14082009-164110/.
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Este trabalho apresenta uma proposta para cálculo da correção do fator de construção de núcleos de transformadores de potência, devido à influência das perdas na região das juntas magnéticas. Esse fator permite corrigir o valor de perdas em vazio no núcleo, obtido das curvas do fabricante das chapas de aço-silício, e sua determinação, até o momento, tem sido baseada, sobretudo, em estimativas empíricas e estatísticas. A correção proposta para esse fator é baseada no cálculo das perdas magnéticas na região das juntas, cálculo esse obtido a partir de uma simulação computacional do transformador pelo Método de Elementos Finitos. Com esse fator de correção, foi possível melhorar a precisão do cálculo de perdas em vazio, aproximando-o mais dos valores experimentais. Foram estudados dois tipos de juntas magnéticas, com e sem step-lap, e três dimensões de entreferro; em seguida, foi analisada a influência desses parâmetros no fator de construção. As simulações foram realizadas por um programa comercial que utiliza o Método de Elementos Finitos em duas dimensões.This work presents a suggestion to calculate a correction factor of building factor in a core of power transformers, due to influence of losses in the magnetic junctions. This factor allows correcting the value of no load loss in the core, obtained from steel manufacturers, and their determination, up to now, it has been based, especially, in empirical and statistics estimates. The correction suggested to this factor is based in magnetic losses calculations in junction region, calculation which was obtained from a computer simulation of the transformer by Finite Element Method. Having this correction factor, could the accuracy of the calculation of no load loss, be improved, setting of the experimental value closer. Two types of magnetic joints, with and without step-lap, and three of gap were studied; then, it was examined the influence of these parameters in the building factor. The simulations were run by commercial software which uses finite element method in two dimensions.
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Hoopes, Marva L. "The power of story in the spiritual development of children." Thesis, Biola University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3589727.
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In a child's life, the church has minimal time to make a maximum impact. The time children are in church must not be wasted, but should be spent in valuable and life changing ways. Stories have long been included in Christian education, but is the practice of telling stories something that is continued merely because "we've always done it this way," or is there merit in continuing their use? Story is a wildly popular theme in Christian education today and children love stories, but there is more to a story than mere amusement? Parents and Christian educators wrestle with questions such as "How do stories have lasting meaning and life changing influence on children's lives?" "How can stories be used to affect children's spiritual growth?" "What kinds of stories should be included?" These are important questions to consider as Christian educators set pedagogical goals and specific methodology is followed.
This research attempts to address these questions by investigating empirical, theoretical, and theological literature related to two domains: (a) what characterizes the spiritual life and development of children, and (b) how story can be used by Christian educators and parents to benefit the instruction and spiritual growth of children. Beginning with an analysis of the spiritual life of children, it will then be shown how story affects the whole person, rendering it a very powerful medium. Using Luke 10:27 as an organizing principle, story is analyzed as to how it affects the heart, the affective realm; the soul, the spiritual realm; strength, the behavioral realm; the mind, the cognitive realm; and loving neighbor as oneself, the social realm. These realms, together, comprise a faith that involves a totality of commitment. Recommendations are then made as to how parents and Christian educators can use the power of story to benefit the instruction and spiritual growth of children. The use of story can be a spark for children's spiritual growth and holds great potential benefit for the church and for the children who are a part of the community of faith.
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Fuentes-Rosado, J. "Test characteristics and operation of surge arrester elements." Thesis, Cardiff University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283894.
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This Thesis presents the development of an empirical and simple computer model for a voltage response of a ZnO element The derived model consists of a linear capacitor and atime-varying resistance. The data necessary for the derivation of the model is collected from testing on three ZnO elements with three different linear circuits. The front times of the voltage responses of the ZnO elements range from nanoseconds to submicroseconds. The front times of the current impulses being used to produce the voltage impulses varies from nanoseconds to microseconds. The voltages having nanosecond front times are measured with attenuators and the voltages with sub-microsecond-front time with a capacitor divider. Currents associated with the nanosecond-front-time voltages are measured with a technique founded on transmission line concepts. Currents associated with the submicrosecond-front-time voltages are obtained with a current shunt The response time of the capacitor divider and of the current shunt fall outside the ranges of the ratios of front time to response times specified in the IEC standard. Distortion introduced by the measuring devices into the measured signals is investigated with computer simulation. Conical transmission lines were constructed to test the voltage response of a toroidal ZnO element to the nanosecond-front-time current impulses. Analysis of the voltage response to the current impulses with sub-and-microsecond-front times indicates that at the beginning of the response, of a ZnO element it behaves as an approximately linear capacitor and subsequently as a capacitor in parallel with a timevarying resistance. The turn-on of the resistive behaviour occurs at approximately the first current peak The discrete voltage relating to the first current peak is named here the threshold voltage. This discrete voltage also denotes the tum-off of the resistive behaviour on the wave tail. The values of the apparent capacitances and permittivities of the ZnO elements are obtained. The apparent permittivities of the three ZnO elements are similar. The computed and measured variations of the resistance show good agreement The simulated and computed voltage responses of a ZnO element also show good agreement Atoroidal ZnO element is tested with the nanosecond-front-time current impulses. Analysis of the voltage response and the current-impulse shape by q-v curves and comparison of the measured responses to those of lumped linear capacitors show that a)the response of the ZnO element is capacitive and b) the capacitor characteristic is quasilinear. The simulated and computed voltage responses show good agreement The deviation from linearity originates from both the limited response of the attenuators and mismatches between the conical transmission lines and the section of the coaxial cable of the used current generator. The voltage response of miniature ZnO elements (also tested with the nanosecond-front time current impulses) show resistive behaviour. This Thesis also presents the design, construction and operation of a measuring system based on Rogowski coils. The model used for the analysis of the measuring system is an extended version of an existing model of a Rogowski coil. The model being introduced here can account for the interaction of the Rogowski coil with the remainder of the measuring system. This is applied successfully to the measurement of an impulse current flowing through a ZnO element
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Wen, Guoping. "Finite element modeling and machine design for powder compaction in a cylindrical mold /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901298.
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Husband, Rachel Jane. "Structural studies of mid-Z lanthanide elements at high pressure." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/28703.
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The majority of the metallic elements adopt simple, high-symmetry structures at ambient pressure. These consist of a highly-ordered arrangement of atoms, which can be described by a crystal lattice that is periodic in three dimensions. It may be expected that close-packed structures, such as face-centred cubic (fcc) and hexagonal close-packed (hcp), would be favoured at high pressures due to the increase in density. However, many of these elements transform to lowsymmetry, complex structures on compression. In particular, a number have been observed to adopt incommensurately-modulated structures at high pressure. In these structures, atoms are displaced from their average positions by a modulation wave, the wavelength of which is an irrational multiple of the lattice periodicity. Diamond-anvil cells (DACs) can be used to compress materials to over a million times atmospheric pressure. In these devices, a small sample is compressed between the tips of two diamond anvils. The atomic arrangement of materials at extreme pressures can then be probed using the intense x-ray beams provided by synchrotron sources. In this work, the high-pressure crystal structures of the lanthanide elements europium (Eu) and samarium (Sm) have been investigated using angle-dispersive x-ray powder dffraction techniques. The high-pressure structural behaviour of Eu has been found to be remarkably different from that of the other lanthanide elements. Two new high-pressure phases of Eu are reported, both of which have an incommensurately-modulated crystal structure.
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Cavedon, Carolina Christmann. "The Power of Reflective Professional Development in Changing Elementary School Teachers' Instructional Practices." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/2075.
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With the new goal of K-12 education being to prepare students to be college and career ready at the end of high school, education needs to start changing at the elementary school level. The literature suggests that teachers need reflective professional development (PD) to effectively teach to the new standards and to demonstrate change to their current instructional practices. This mixed-method multiple-case study investigated the impacts of a reflective professional development (PD) in changing elementary school teachers' instructional practices.
Teachers Instructional Portfolios (TIPs) were scored with a TIP rubric based on best practices in teaching mathematics problem-solving and science inquiry. The TIPs were also analyzed with a qualitative coding scheme. Case descriptions were written and all the collected data were used to explain the impacts of the reflective PD on changes in teachers' instructional practices.
While we found no predictive patterns in relation to teachers changing their classroom practices based on the reflective PD, we claim that teachers' desire to change might contribute to improvements in instruction. We also observed that teachers' self-assessment scores tend to be higher than the actual TIP scores corroborating with the literature on the usage of self-assessment to evaluate teachers' instructional practices.
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Salton, Grant. "The power spectrum of cosmic microwave background polarization from cosmic string wakes." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121559.
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We compute the integrated Sachs--Wolfe type contribution to the CMB polarization power spectrum from cosmic string wakes. An introduction to topological defects, cosmic strings, CMB polarization, and spin-s fields is given. We then use these tools to compute the angular power spectrum of E- and B-mode polarization due to cosmic string wakes, in the flat sky limit. We find that cross-correlation terms (i.e., EB, ET, BT) vanish, while the EE and BB power spectra are equal in shape and magnitude. This result is in stark contrast with B-mode polarization from Gaussian fluctuations, which vanishes identically. However, we find that the shape of the power spectrum from cosmic string wakes is very similar to the predicted B-mode power spectrum from gravitational lensing, but with a small overall amplitude. As such, the cosmic string wake signal is too small to be picked out from lensing, and background subtraction techniques would be very difficult. We find that the peak amplitude in the dimensionless power spectrum (sqrt(l(l+1)C_l/2pi)) is about 10^(-4) at a peak value of l~400.We briefly study the asymptotic version of the power spectrum and find that C_l is approximately constant until a turn around point set by the angular size of the dominant wakes. We then determine which cosmic string wakes give rise to the dominant contribution to the full, integrated power spectrum and find that the dominant wakes are those which were formed at the time of equal matter and radiation, and which intersect our past light cone at recombination. We conclude that the Fourier space signal (power spectrum) is too weak to detect cosmic string wakes in existing data, and future searches should focus on distinct position space features.Nous calculons la contribution intégrée au spectre de puissance de la polarisation du fond diffus cosmique (CMB) grâce aux sillages des cordes cosmiques. Une introduction aux défauts topologique, cordes cosmiques, de polarisation du CMB, et aux champs spin–s est donnée. Nous utilisons ensuite ces outils pour calculer le spectre de puissance angulaire de la polarisation des modes E et B grâce aux des sillages des cordes cosmiques, dans la limite du ciel plat. Nous trouvons que les termes de corrélation croisée (EB, ET, BT) sont zero, tandis que les spectres de puissance pour EE et BB ont la même forme et grandeur. Ce résultat contraste le polarisation du mode B causée par les fluctuations Gaussiennes, qui disparaîssent. Cependant, nous trouvons que la forme du spectre de puissance causée par les sillages de cordes cosmiques est très similaire au spectre en mode B prédite par lentille gravitationnelle, mais avec une amplitude globale trés faible. Donc, le signal du sillage de corde cosmique est trop faible pour être measuré au-dessus l'indicatif du lentille. Aussi, les méthodes de soustraction du fond serait très difficile. Nous trouvons que l'amplitude maximum dans le spectre de puissance sqrt(l(l+1)C_l/2pi) est d'environ 10^(-4) pour l~400.Nous étudions brièvement le forme asymptotique du spectre de puissance, et nous trouvons que Cl est quasi–constant en l jusqu'à un tournant correspondant à la taille angulaire du sillage le plus important. Nous déterminons alors quel sillage donne la contribution dominante au spectre de puissance complet. Nous trouvons que les sillages dominants sont ceux qui ont été formés à l'epoque de l'égalité de matière et de rayonnement, et qui croisent notre cône de lumière passé à l'époque de recombinaison. Nous concluons que l'indicatif dans l'espace Fourier est trop faible pour être détecté. Donc, les recherches futures devraient se concentrer sur les caractéristiques l'espace spatial.
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Canto, Rodrigo Bresciani. "Projeto e fabricação de moldes para prensagem isostática utilizando tecnologias CAD/CAE e prototipagem rápida." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-17032003-134931/.
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Apresenta uma metodologia para o projeto e fabricação de moldes para prensagem isostática de pó cerâmico (alumina) utilizando ferramentas computacionais CAD/CAE associadas à tecnologia de Prototipagem Rápida. O processo de prensagem isostática é simulado utilizando o método dos elementos finitos. Para a representação da compactação do pó cerâmico é utilizado o modelo de Drucker-Prager/cap e para a representação do comportamento do material elastomérico é utilizado o modelo hiperelástico de Mooney-Rivlin, ambos disponíveis no programa ABAQUS. Tal simulação visa obter o projeto do molde de forma mais rápida e precisa, ajustando-o até que se alcance um molde adequado para produzir um compacto com uma quantidade de sobrematerial ideal para o processo de usinagem a verde. Para isso utilizou-se como estudo de caso uma esfera cerâmica para implante de quadril. Um protótipo virtual do molde adequado obtido das simulações é então modelado e reproduzido em plástico ABS (Acrylonitrile Butadiene Styrene) pela tecnologia de Prototipagem Rápida FDM (Fused Deposition Modeling). Esse protótipo físico é a base para o desenvolvimento de matrizes rígidas e em silicone, que são utilizadas para a confecção da parte flexível do molde (matriz elastomérica) e de partes rígidas como a gaiola suporte obtidas por vazamento dos polímeros. Constatou-se a viabilidade da utilização da metodologia de projeto e fabricação do molde para prensagem isostática, considerando que as simulações mostraram-se bastante coerentes com os resultados experimentais obtidos de componentes prensados.This work presents a methodology for the design and fabrication of ceramic powder isostatic pressing moulds using CAD and CAE tools and Rapid Prototyping. The isostatic pressing process was simulated using the finite element method. The compaction behavior of ceramic powder is described by the Drucker-Prager/cap constitutive model and the behavior of elastomeric material is described by the Mooney-Rivlin constitutive model within the commercial finite element software ABAQUS®. These simulations are required to adjust the mould design in order to suit the geometry of the compact and green machining allowance. For this study, it is used a case study consisting of pressing a ceramic sphere for hip implant stem. A virtual prototype was designed from the geometry obtained from the simulations and reproduced in Acrylonitrile Butadiene Styrene (ABS) polymer, using the Rapid Prototyping technology - Fused Deposition Modeling (FDM). Silicone moulds were obtained from the polymer prototype and used to aid in the making of the elastomeric bag and mould support cage. The methodology used in this investigation was validate considering that the simulations yield to a good agreement with measured manufactured components.
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Camm, Melody Luretha. "The power of African American parent perceptions on student achievement." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539618818.
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With the implementation of No Child Left Behind, schools have been challenged to maintain Annual Yearly Progress (AYP) for low achieving subpopulations. Current research supported by historical data suggests that African American parent involvement could possibly be the missing link to African American student achievement. This study explores the possible connection between African American parent perceptions of their school involvement and student achievement. It surveyed 738 fourth grade parents from five Title I and five Non-Title I schools to see if there was a significant difference between the parent involvement perceptions of African American Parents and Non-African American Parents, as well as investigated the possible relationship of these perceptions to student achievement. Although a correlation was not found between African American parent perceptions and student achievement, other comparative analyses done indicates that there are interesting similarities and differences between Title I and Non-Title I parent populations. These findings may contribute to existing research concerning school factors that can be enhanced in order to encourage parent involvement. Implications for practice and future research are also discussed.
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vaissie, laurent. "MONOLITHIC INTEGRATION OF DUAL OPTICAL ELEMENTS ON HIGH POWER SEMICOND." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3885.
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This dissertation investigates the monolithic integration of dual optical elements on high power semiconductor lasers for emission around 980nm wavelength. In the proposed configuration, light is coupled out of the AlGaAs/GaAs waveguide by a low reflectivity grating coupler towards the substrate where a second monolithic optical element is integrated to improve the device performance or functionality. A fabrication process based on electron beam lithography and plasma etching was developed to control the grating coupler duty cycle and shape. The near-field intensity profile outcoupled by the grating is modeled using a combination of finite-difference time domain (FDTD) analysis of the nonuniform grating and a self-consistent model of the broad area active region. Improvement of the near-field intensity profile in good agreement with the FDTD model is demonstrated by varying the duty cycle from 20% to 55% and including the aspect ratio dependent etching (ARDE) for sub-micron features. The grating diffraction efficiency is estimated to be higher than 95% using a detailed analysis of the losses mechanisms of the device. The grating reflectivity is estimated to be as low as 2.10-4. The low reflectivity of the light extraction process is shown to increase the device efficiency and efficiently suppress lasing oscillations if both cleaved facets are replaced by grating couplers to produce 1.5W QCW with 11nm bandwidth into a single spot a few mm above the device. Peak power in excess of 30W without visible COMD is achieved in this case. Having optimized, the light extraction process, we demonstrate the integration of three different optical functions on the substrate of the surface-emitting laser. First, a 40 level refractive microlens milled using focused ion beam shows a twofold reduction of the full-width half maximum 1mm above the device, showing potential for monolithic integration of coupling optics on the wafer. We then show that differential quantum efficiency of 65%, the highest reported for a grating-coupled device, can be achieved by lowering the substrate reflectivity using a 200nm period tapered subwavelength grating that has a grating wavevector oriented parallel to the electric field polarization. The low reflectivity structure shows trapezoidal sidewall profiles obtained using a soft mask erosion technique in a single etching step. Finally, we demonstrate that, unlike typical methods reported so far for in-plane beam-shaping of laser diodes, the integration of a beam-splitting element on the device substrate does not affect the device efficiency. The proposed device configuration can be tailored to satisfy a wide range of applications including high power pump lasers, superluminescent diodes, or optical amplifiers applications.Ph.D.
Other
Optics and Photonics
Optics
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Jain, Apurva. "Applications of Volume Holographic Elements in High Power Fiber Lasers." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5318.
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The main objective of this thesis is to explore the use of volume holographic elements recorded in photo-thermo-refractive (PTR) glass for power scaling of narrow linewidth diffraction-limited fiber lasers to harness high average power and high brightness beams. Single fiber lasers enable kW level output powers limited by optical damage, thermal effects and non-linear effects. Output powers can be further scaled using large mode area fibers, however, at the cost of beam quality and instabilities due to the presence of higher order modes. The mechanisms limiting the performance of narrow-linewidth large mode area fiber lasers are investigated and solutions using intra-cavity volume Bragg gratings (VBG) proposed. Self-pulsations-free, completely continuous-wave operation of a VBG-stabilized unidirectional fiber ring laser is demonstrated with quasi single-frequency (< 7.5 MHz) output. A method for transverse mode selection in multimode fiber lasers to reduce higher order mode content and stabilize the output beam profile is developed using angular selectivity of reflecting VBGs. By placing the VBG output coupler in a convergent beam, stabilization of the far-field beam profile of a 20 ?m core large mode area fiber laser is demonstrated. Beam combining techniques are essential to power scale beyond the limitations of single laser sources. Several beam combining techniques relevant to fiber lasers were compared in this study and found to be lacking in one or more of the following aspects: the coherence of the individual sources is compromised, the far-field beam quality is highly degraded with significant power in side lobes, spectrally broad and unstable, and uncertainty over scaling to larger arrays and higher power. Keeping in mind the key requirements of coherence, good far-field beam quality, narrow and stable spectra, and scalability in both array size and power, a new passive coherent beam combining technique using multiplexed volume Bragg gratings (M-VBGs) is proposed. In order to understand the mechanism of radiation exchange between multiple beams via these complex holographic optical elements, the spectral and beam splitting properties a 2nd order reflecting M-VBG recorded in PTR glass is experimentally investigated using a tunable single frequency seed laser. Two single-mode Yb-doped fiber lasers are then coherently combined using reflecting M-VBGs in both linear and unidirectional-ring resonators with >90% combining efficiency and diffraction-limited beam quality. It is demonstrated that the combining bandwidth can be controlled in the range of 100s of pm to a few pm by angular detuning of the M-VBG. Very narrow-linewidth (< 210 MHz) operation in a linear cavity and possibility of single-frequency operation in a unidirectional ring cavity of the coherently combined system is demonstrated using this technique. It is theoretically derived and experimentally demonstrated that high combining efficiency can be achieved even by multiplexing low-efficiency VBGs, with the required diffraction efficiency of individual VBGs decreasing as array size increases. Scaling of passive coherent beam combining to four fiber lasers is demonstrated using a 4th order transmitting M-VBG. Power scaling of this technique to 10 W level combined powers with 88% combining efficiency is demonstrated by passively combining two large mode area fiber lasers using a 2nd order reflecting M-VBG in a unidirectional ring resonator. High energy compact single-frequency sources are highly desired for several applications – one of which is as a seed for high power fiber amplifiers. Towards achieving the goal of a monolithic solid-state laser, a new gain medium having both photosensitive and luminescence properties is investigated – rare-earth doped PTR glass. First lasing is demonstrated in this new gain element in a VBG-stabilized external cavity.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Yang, Sheng. "Error resilient techniques for storage elements of low power design." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355203/.
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Over two decades of research has led to numerous low-power design techniques being reported. Two popular techniques are supply voltage scaling and power gating. This thesis studies the impact of these two design techniques on the reliability of embedded processor registers and memory systems in the presence of transient faults; and with the aim to develop and validate efficient mitigation techniques to improve reliability with small cost of energy consumption, performance and area overhead. This thesis presents three original contributions. The first contribution presents a technique for improving the reliability of embedded processors. A key feature of the technique is low cost, which is achieved through reuse of the scan chain for state monitoring, and it is effective because it can correct single and multiple bit errors through hardware and software respectively. To validate the technique, ARMR Cortex TM -M0 embedded microprocessor is implemented in FPGA and further synthesised using 65-nm technology to quantify the cost in terms of area, latency and energy. It is shown that the presented technique has a small area overhead (8.6%) with less than 4% worst-case increase in critical path. The second contribution demonstrates that state integrity of flip-flops is sensitive to process, voltage and temperature (PVT) variation through measurements from 82 test chips. A PVT-aware state protection technique is presented to ensure state integrity of flip-flops while achieving maximum leakage savings. The technique consists of characterisation algorithm and employs horizontal and vertical parity for error detection and correction. Silicon results show that flip-flops state integrity is preserved while achieving up to 17.6% reduction in retention voltage across 82-dies. Embedded processors memory systems are susceptible to transient errors and blanket protection of every part of memory system through ECC is not cost effective. The final contribution addresses the reliability of embedded processor memory systems and describes an architectural simulation-based framework for joint optimisation of reliability, energy consumption and performance. Accurate estimation of memory reliability with targeted protection is proposed to identify and protect the most vulnerable part of the memory system to minimise protection cost. Furthermore, L1-cache resizing together with voltage and frequency scaling is proposed for further energy savings while maintaining performance and reliability. The contributions presented are supported by detailed analyses using state-of-the-art design automation tools, in-house software tools and validated using FPGA and silicon implementation of commercial low power embedded processors
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DOURADO, BENJAMIN T. "Avaliacao do processo de producao - estudo dimensional de peca sinterizada." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9376.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Tolvanen, Merja. "Mass balance determination for trace elements at coal-, peat- and bark-fired power plants /." Espoo [Finland] : VTT Technical Research Centre of Finland, 2004. http://www.vtt.fi/inf/pdf/publications/2004/P524.pdf.
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Martinho, Lucas Blattner. "Contribuições à modelagem de sistemas de aterramento pelo método dos elementos finitos no regime harmônico." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-02062009-150541/.
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Este trabalho tem como objetivo fornecer contribuições ao estudo de sistemas de aterramento submetidos a correntes elétricas no regime permanente senoidal pelo Método dos Elementos Finitos. Nele se discutem as motivações para a utilização deste procedimento numérico em problemas desta categoria, e mais especificamente para o uso da variante deste método com elementos finitos de aresta. O tratamento completo necessário à construção das funções de forma para a aproximação local de grandezas vetoriais com elementos hexaédricos é nele desenvolvido e detalhado. Com estes resultados, uma aplicação computacional capaz de modelar o comportamento de uma haste de aterramento verticalmente enterrada no solo foi desenvolvida, utilizando-se para a discretização do domínio elementos finitos hexaédricos tri-lineares e quadráticos incompletos. Esta aplicação computacional foi utilizada para o estudo da resposta em freqüência da impedância equivalente a aterramentos desta categoria em diferentes condições de solo e com as duas variedades de elemento hexaédrico anteriormente mencionados. Os resultados obtidos são então discutidos, bem como a validade da modelagem adotada para o problema físico aqui considerado.This work aims to provide contributions to the study of grounding systems subjected to electric currents at the sinusoidal steady state by the Finite Element Method. Motivations for the use of this numerical procedure in problems of this category, and more specifically for the usage of the Edge Finite Element Method variant, are discussed in it. The complete treatment required for building the shape functions for the local approximation of vector physical quantities with hexahedral finite elements is here developed and detailed. With these results a computer application capable of modeling the behavior of vertically buried grounding rods was developed, in which domain discretization is accomplished by the usage of both tri-linear and incomplete quadratic hexahedral finite elements. This computer application was employed in the study of the frequency response of the impedance equivalent to grounding systems of this class at different soil conditions and with both hexahedral element varieties previously mentioned. The results obtained are then discussed, as well as the validity of the modeling adopted for this physical problem.
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Melo, André de Souza. "Identificação de pontos quentes em transformadores de potência por meio de técnicas não invasivas." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-07112017-151817/.
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Esta pesquisa apresenta uma metodologia, baseada em duas técnicas não invasivas para identificação e diagnóstico de pontos quentes em transformadores de potência durante plena operação ou em fase de projeto. A primeira técnica é baseada na medição de radiação infravermelha, emitida pelo equipamento em funcionamento e registrada por meio de análise termográfica. A segunda técnica é possível a partir do conhecimento prévio das características construtivas do transformador, fazendo uso do Método dos Elementos Finitos (MEF). A segunda técnica pode ser validada a partir das medições realizadas utilizando a primeira técnica. A formação de gases no interior dos transformadores de potência, devido à elevação da temperatura do óleo isolante em função dos pontos quentes, é discutida em detalhes com base nas normas técnicas estabelecidas pelo IEEE e IEC. As técnicas e procedimentos abordados ao longo dessa pesquisa foram obtidos a partir de um transformador com potência nominal de 120 MVA e relação de tensão 13,8/230 kV, projetado para integrar uma fazenda eólica ao Sistema Interligado Nacional (SIN).This research presents a methodology based on two noninvasive techniques for identification and diagnostic of hot spots in power transformers during operation or project development. The first is based on measurements of infrared radiation from the equipment during operation and recording by thermography. The second technique is possible from the previous knowing of the constructive characteristics of the power transformer, by using the Finite Element Method (FEM). The second technique can be validated from measurements obtained using the first technique. The gas formation into the power transformers, because of the high temperatures in the insulating oil due to the hot spots, is discussed in details based on normative recommendations well established by the IEEE and IEC. All techniques and procedures to be approached in this research were obtained using a 120-MVA power transformer with voltage relationship of 13.8/230 kV that was projected to interconnect a wind farm to the Interconnected Brazilian System (Sistema Interligado Nacional - SIN).
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Friedman, Iris. "Literatura de Testemunho e a denúncia de uma voz ausente em Primo Levi e Bernardo Kucins." Pontifícia Universidade Católica de São Paulo, 2016. https://tede2.pucsp.br/handle/handle/19450.
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This dissertation proposes a study of the works É isto um homem? (1988), by Primo Levi, and K.- Relato de uma busca (2014), by Bernardo Kucinski, utilizing an approach from the Testimony Literature. Prioritizing this literary category to conduct a Reading – that employs fictional elements to cope with texts of witnessing nature – benefits the understanding of limit-events such as the Shoah and the Brazil´s military dictatorship, which belong to the Era of Catastrophes. The analysis of tensions between the presence and absence in the representations of the trauma highlights the issue of negative power as a way to re-dimension the work according to its narrative possibilities
Esta dissertação propõe um estudo das obras É isto um homem? (1988), de Primo Levi, e K.- Relato de uma busca (2014), de Bernardo Kucinski, a partir de uma abordagem da Literatura de Testemunho. Privilegiar esta modalidade literária na realização de uma leitura – que utiliza elementos ficcionais para dar conta de textos de cunho testemunhais – favorece a compreensão de eventos-limite como a Shoah e a Ditadura Militar Brasileira, inseridos na Era das Catástrofes. A análise das tensões entre presença e ausência nas representações do trauma destaca a questão da potência negativa como forma de redimensionamento da obra em função de suas possibilidades narrativas
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Scruggs, James N. "Power system availability determination through Petri net simulation." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1178910568.
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Bandeen, Heather Mae. "Elusive Practices of Gender, Power, and Silence: Theorizing the Relational Power of Elementary Teachers in the Policy Epidemic." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1248292175.
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