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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.
71

Eletrodeposição de filmes finos e materiais nanoestruturados das ligas magnéticas cobalto-níquel e cobalto-níquel-molibdênio / Electrodeposition of CoNi and CoNiMo magnetic alloys thin films and nanowires

Esteves, Marcos Cramer 08 May 2009 (has links)
Este trabalho trata do estudo da eletrodeposição de filmes finos e nanofios magnéticos compostos de cobalto, níquel e molibdênio. Foi avaliada a influência da composição química das soluções utilizadas nas propriedades do material obtido. O uso de uma célula de Hull com eletrodo cilíndrico rotativo permitiu também que fosse estudado com mais detalhe o mecanismo de eletrodeposição da liga CoNiMo. Os filmes finos magnéticos de CoNi e CoNiMo foram eletrodepositados galvanostaticamente utilizando soluções contento citrato ou glicina como aditivo. Composição, microestrutura, morfologia e propriedades magnéticas dos depósitos foram analisados e a influência da composição das soluções e das densidades de corrente aplicadas foi avaliada. Soluções contendo citrato e/ou baixo pH não resultaram em filmes com boas propriedades. O uso de glicina e pH 7 resultou em filmes amorfos e com melhores propriedades magnéticas: magnetização de saturação de 1,2 T e coercividade de 50 Oe. Com o uso da célula de Hull rotativa foi possível avaliar como variava a composição da liga e as densidades de corrente parciais de cada um dos elementos. Notou-se que a deposição de Ni era menor quanto maior a concentração de Co+2 na solução e que o aumento na concentração de glicina favorece a deposição de Co e Mo e prejudica a deposição de Ni. Além disso, a deposição de Mo foi mais influenciada pela concentração de Co+2 do que pela de Ni+2. Tais observações podem ser analisadas com base nos mecanismos já propostos para deposição de Co, Ni e Mo. Nanofios das ligas CoNi e CoNiMo foram preparados através de eletrodeposição potenciostática utilizando membranas comerciais de alumina como molde. Glicina foi utilizada como agente complexante nos eletrólitos. Fios amorfos com diâmetro médio de 200 nm e até 50 µm de comprimento foram obtidos. Em comparação com os filmes finos estudados previamente, os nanofios apresentaram maiores coercividade e cristalinidade. A coercividade medida foi de 220 Oe com o campo magnético aplicado em paralelo aos fios e de 350 Oe com o campo aplicado perpendicularmente. A presença do molibdênio não afetou as características magnéticas dos nanofios. / This work focuses on the electrodeposition of CoNi and CoNiMo thin films and nanowires. The influence of the chemical composition of several tested solutions over the properties of the material were evaluated. A rotating cylinder Hull cell allowed a more detailed study of the deposition mechanism. The thin films were galvanostatic electrodeposited from solutions containing either citrate or glycine as additives. The composition, microstructure, morphology and magnetic properties of the deposits were analyzed and related with the different bath compositions used and the applied current densities. Baths containing citrate and/or at low pH are not suitable conditions to produce magnetic films with reasonable good properties to be used in magnetic devices. Generally, use of glycine in the bath and pH 7 yielded better films. Magnetic saturation values around 1.2 T and coercivities as low as 50 Oe were obtained for films prepared using baths containing glycine. Films electrodeposited with the citrate containing baths showed higher coercivity: 125 Oe. The investigation of a wide variation of parameters the electrodeposition of the CoNiMo alloys was performed using a rotating cylinder Hull cell. Alloy composition, current efficiency and partial currents of each metal were analyzed. The nickel deposition rate decreased by increasing Co ions and glycine in the electrolyte. The latter also resulted in na augmented concentration of Ni-Gly complexed species. Molybdenum induced codeposition was verified for both excess Ni and excess Co electrolytes. The results indicate that Mo reduction was affected by the Co/Ni ratio in the electrolyte. With an excess Ni in solution, Mo wt. % increased with an increase in cobalt ion electrolyte concentration. On the other hand, with an excess of cobalt in solution, Mo wt. % was not significantly affected by nickel ion concentration. These results were analysed based on the current proposed mechanisms for Co, Ni and Mo deposition. CoNi and CoNiMo nanowires were electrodeposited using commercial alumina templates and a pH 7 glycine-ammonia electrolyte. The resulting magnetic properties and composition were compared with thin film counterparts. The nanowires had larger coercivity (220 Oe) and more crystallinity than the thin. The presence of molybdenum had no significant influence over the coercivity and remanence in the nanowires, unlike thin films.
72

Relação entre investimento em saúde e desenvolvimento dos estados brasileiros / Relationship between investment in health asset and brazilians states development

Anjos, Rafael Madureira dos 30 August 2010 (has links)
Este trabalho se propõe analisar a relação entre o investimento em saúde e desenvolvimento dos estados brasileiros - medido pelo Índice de Desenvolvimento Humano- (IDH) mediante a utilização da tecnologia de produção denominada FDH (Free Disposal Hull - Fronteira com livre descarte de recursos). Para os estados não eficientes, serão identificados os percentuais de alteração dos insumos necessários para que estados sejam eficientes. Na seqüência, são selecionados os estados eficientes e com baixo índice de desenvolvimento, para serem utilizados pelos governos estadual e federal como prioridade em uma política de desenvolvimento para o Estado brasileiro, uma vez que, esses estados, por serem eficientes, com o aumento de investimento em ativos de saúde, aumentarão seu índice de desenvolvimento. Em suma, tem-se que os resultados permitirão algumas considerações sobre a eficiência em alocação de recursos nos diferentes ativos de saúde, possibilitando auxiliar a tomada de decisão do gestor público, no que diz respeito à alocação dos recursos disponíveis para área da saúde. / In this work it has attempted to appraise, quantitatively, the efficiency levels of the brazilians states. It is analyzed the relationship between output (development) and inputs (Health Assets) by constructing nonparametric efficiency frontiers. The technique of efficiency analysis were used to determine this frontier is the FDH approach. For the not efficient states, the percentages of alteration of inputs will be identified (Health Assets) necessary so that states are efficient. In the sequence, the efficient states and with low index of development will be selected, to be used for the state and federal governments as priority in one politics of Brazil development, a time that, these states, for being efficient, with the increase of investment in health asset, will increase its index of development. The results will be provided useful insights into the assessment of the administrative efficiency Health Assets.
73

Síntese de cascos de embarcações através de métodos de otimização aplicados a curvas B-Spline. / Hull form design with optimization methods applied to parametric B-Spline curves.

Barbarini, Luiz Henrique Maiorino 09 February 2007 (has links)
Este trabalho apresenta uma ferramenta flexível e eficiente para o campo de projeto e desenho preliminar de cascos de embarcações. O estado da arte de projeto de cascos de embarcações consiste em um processo iterativo onde, primeiramente, definem-se parâmetros geométricos, de estabilidade, e hidrodinâmicos. Em seguida, o casco é modelado através de curvas paramétricas. submetido a uma análise de desempenho, e, após isso, é feita a tomada de decisão para otimizar os parâmetros iniciais. O ciclo se repete até que se atinja o resultado desejado. O que será apresentado cumpre com a parte de modelagem paramétrica, e é capaz de gerar de forma automática e otimizada curvas que compõem o projeto de uma embarcação de recreio. A ferramenta recebe parâmetros de alto nível, como razões adimensionais, coeficientes de forma e restrições, e desenha tridimensionalmente um casco intrinsecamente suave, de forma que todos os parâmetros especificados sejam atendidos. Uma metodologia de projeto de cascos de veleiros é utilizada em conjunto com curvas B-Splines, submetidas a um algoritmo de otimização, em cuja função objetivo se empregam critérios de suavidade (\"fairness criteria\"). O problema de otimização de curvas B-Splines é não linear, pela própria formulação da função objetivo e suas restrições. Para tal, utiliza-se um método de Programação Quadrática Seqüencial. Para a otimização dos parâmetros principais do casco, utiliza-se uma metodologia de baixo custo, baseada na técnica de Superfície de Resposta, que otimiza uma função de mérito, no caso, a resistência residual, variando-se dois parâmetros do casco. A interface com softwares CAD é desenvolvida com o objetivo de se realizar outras análises, como de curvatura da superfície, além do projeto do restante da embarcação. Neste também pode ser gerado o bloco sólido para integração com softwares de CAM para a usinagem e fabricação do mesmo. / This article presents a flexible and efficient tool to the field of ship project and preliminary design by using an approach of parametric modeling of hull forms. The state of the art of design of hulls consists in an iterative process where, first, geometric, stability and hydrodynamic parameters are defined. After that, the hull is modeled through parametric curves, simulated in a performance analysis software, and, after that, it is taken the decision to optimize the initial parameters. The cycle repeats until it reaches the desired result. This work deals with the part of parametric modeling, and is capable to generate, in an automatic way, optimized curves that compose the design of the hull of a yacht. The tool receives high level parameters, such as non-dimensional ratios, coefficients and restrictions, and draws a three-dimensional hull, intrinsically fair, fulfilling all the specified parameters. A methodology for the design of sail-boats is presented together with B-Splines curves, submitted to an optimization algorithm, using fairness criteria as the objective function. The optimization problem of B-Splines curves is not linear, because of its mathematical formulation, the objective function and constraints adopted. Therefore, a method of Sequential Quadratic Programming is used. For the optimization of the main parameters of the hull, a cost-effective methodology, based on the Surface Response Method, is proposed, optimizing a merit criterion, such as, the residuary resistance, changing two parameters of the hull. The interface with CAD software is implemented in order to allow other analyses, such as surface curvature, and the design of the other parts of the boat. The drawing also can be transformed into a solid model, and integrated with a CAM software to be ready for itsmanufacturing.
74

Convexities convexities of paths and geometric / Convexidades de caminhos e convexidades geomÃtricas

Rafael Teixeira de AraÃjo 14 February 2014 (has links)
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / In this dissertation we present complexity results related to the hull number and the convexity number for P3 convexity. We show that the hull number and the convexity number are NP-hard even for bipartite graphs. Inspired by our research in convexity based on paths, we introduce a new convexity, where we defined as convexity of induced paths of order three or P∗ 3 . We show a relation between the geodetic convexity and the P∗ 3 convexity when the graph is a join of a Km with a non-complete graph. We did research in geometric convexity and from that we characterized graph classes under some convexities such as the star florest in P3 convexity, chordal cographs in P∗ 3 convexity, and the florests in TP convexity. We also demonstrated convexities that are geometric only in specific graph classes such as cographs in P4+-free convexity, F free graphs in F-free convexity and others. Finally, we demonstrated some results of geodesic convexity and P∗ 3 in graphs with few P4âs. / In this dissertation we present complexity results related to the hull number and the convexity number for P3 convexity. We show that the hull number and the convexity number are NP-hard even for bipartite graphs. Inspired by our research in convexity based on paths, we introduce a new convexity, where we defined as convexity of induced paths of order three or P∗ 3 . We show a relation between the geodetic convexity and the P∗ 3 convexity when the graph is a join of a Km with a non-complete graph. We did research in geometric convexity and from that we characterized graph classes under some convexities such as the star florest in P3 convexity, chordal cographs in P∗ 3 convexity, and the florests in TP convexity. We also demonstrated convexities that are geometric only in specific graph classes such as cographs in P4+-free convexity, F free graphs in F-free convexity and others. Finally, we demonstrated some results of geodesic convexity and P∗ 3 in graphs with few P4âs.
75

Eletrodeposição de filmes finos e materiais nanoestruturados das ligas magnéticas cobalto-níquel e cobalto-níquel-molibdênio / Electrodeposition of CoNi and CoNiMo magnetic alloys thin films and nanowires

Marcos Cramer Esteves 08 May 2009 (has links)
Este trabalho trata do estudo da eletrodeposição de filmes finos e nanofios magnéticos compostos de cobalto, níquel e molibdênio. Foi avaliada a influência da composição química das soluções utilizadas nas propriedades do material obtido. O uso de uma célula de Hull com eletrodo cilíndrico rotativo permitiu também que fosse estudado com mais detalhe o mecanismo de eletrodeposição da liga CoNiMo. Os filmes finos magnéticos de CoNi e CoNiMo foram eletrodepositados galvanostaticamente utilizando soluções contento citrato ou glicina como aditivo. Composição, microestrutura, morfologia e propriedades magnéticas dos depósitos foram analisados e a influência da composição das soluções e das densidades de corrente aplicadas foi avaliada. Soluções contendo citrato e/ou baixo pH não resultaram em filmes com boas propriedades. O uso de glicina e pH 7 resultou em filmes amorfos e com melhores propriedades magnéticas: magnetização de saturação de 1,2 T e coercividade de 50 Oe. Com o uso da célula de Hull rotativa foi possível avaliar como variava a composição da liga e as densidades de corrente parciais de cada um dos elementos. Notou-se que a deposição de Ni era menor quanto maior a concentração de Co+2 na solução e que o aumento na concentração de glicina favorece a deposição de Co e Mo e prejudica a deposição de Ni. Além disso, a deposição de Mo foi mais influenciada pela concentração de Co+2 do que pela de Ni+2. Tais observações podem ser analisadas com base nos mecanismos já propostos para deposição de Co, Ni e Mo. Nanofios das ligas CoNi e CoNiMo foram preparados através de eletrodeposição potenciostática utilizando membranas comerciais de alumina como molde. Glicina foi utilizada como agente complexante nos eletrólitos. Fios amorfos com diâmetro médio de 200 nm e até 50 µm de comprimento foram obtidos. Em comparação com os filmes finos estudados previamente, os nanofios apresentaram maiores coercividade e cristalinidade. A coercividade medida foi de 220 Oe com o campo magnético aplicado em paralelo aos fios e de 350 Oe com o campo aplicado perpendicularmente. A presença do molibdênio não afetou as características magnéticas dos nanofios. / This work focuses on the electrodeposition of CoNi and CoNiMo thin films and nanowires. The influence of the chemical composition of several tested solutions over the properties of the material were evaluated. A rotating cylinder Hull cell allowed a more detailed study of the deposition mechanism. The thin films were galvanostatic electrodeposited from solutions containing either citrate or glycine as additives. The composition, microstructure, morphology and magnetic properties of the deposits were analyzed and related with the different bath compositions used and the applied current densities. Baths containing citrate and/or at low pH are not suitable conditions to produce magnetic films with reasonable good properties to be used in magnetic devices. Generally, use of glycine in the bath and pH 7 yielded better films. Magnetic saturation values around 1.2 T and coercivities as low as 50 Oe were obtained for films prepared using baths containing glycine. Films electrodeposited with the citrate containing baths showed higher coercivity: 125 Oe. The investigation of a wide variation of parameters the electrodeposition of the CoNiMo alloys was performed using a rotating cylinder Hull cell. Alloy composition, current efficiency and partial currents of each metal were analyzed. The nickel deposition rate decreased by increasing Co ions and glycine in the electrolyte. The latter also resulted in na augmented concentration of Ni-Gly complexed species. Molybdenum induced codeposition was verified for both excess Ni and excess Co electrolytes. The results indicate that Mo reduction was affected by the Co/Ni ratio in the electrolyte. With an excess Ni in solution, Mo wt. % increased with an increase in cobalt ion electrolyte concentration. On the other hand, with an excess of cobalt in solution, Mo wt. % was not significantly affected by nickel ion concentration. These results were analysed based on the current proposed mechanisms for Co, Ni and Mo deposition. CoNi and CoNiMo nanowires were electrodeposited using commercial alumina templates and a pH 7 glycine-ammonia electrolyte. The resulting magnetic properties and composition were compared with thin film counterparts. The nanowires had larger coercivity (220 Oe) and more crystallinity than the thin. The presence of molybdenum had no significant influence over the coercivity and remanence in the nanowires, unlike thin films.
76

Relação entre investimento em saúde e desenvolvimento dos estados brasileiros / Relationship between investment in health asset and brazilians states development

Rafael Madureira dos Anjos 30 August 2010 (has links)
Este trabalho se propõe analisar a relação entre o investimento em saúde e desenvolvimento dos estados brasileiros - medido pelo Índice de Desenvolvimento Humano- (IDH) mediante a utilização da tecnologia de produção denominada FDH (Free Disposal Hull - Fronteira com livre descarte de recursos). Para os estados não eficientes, serão identificados os percentuais de alteração dos insumos necessários para que estados sejam eficientes. Na seqüência, são selecionados os estados eficientes e com baixo índice de desenvolvimento, para serem utilizados pelos governos estadual e federal como prioridade em uma política de desenvolvimento para o Estado brasileiro, uma vez que, esses estados, por serem eficientes, com o aumento de investimento em ativos de saúde, aumentarão seu índice de desenvolvimento. Em suma, tem-se que os resultados permitirão algumas considerações sobre a eficiência em alocação de recursos nos diferentes ativos de saúde, possibilitando auxiliar a tomada de decisão do gestor público, no que diz respeito à alocação dos recursos disponíveis para área da saúde. / In this work it has attempted to appraise, quantitatively, the efficiency levels of the brazilians states. It is analyzed the relationship between output (development) and inputs (Health Assets) by constructing nonparametric efficiency frontiers. The technique of efficiency analysis were used to determine this frontier is the FDH approach. For the not efficient states, the percentages of alteration of inputs will be identified (Health Assets) necessary so that states are efficient. In the sequence, the efficient states and with low index of development will be selected, to be used for the state and federal governments as priority in one politics of Brazil development, a time that, these states, for being efficient, with the increase of investment in health asset, will increase its index of development. The results will be provided useful insights into the assessment of the administrative efficiency Health Assets.
77

Modeling Repair Patches of Ship Hull and Studying the Effect of Their Orientation on Stresses

Enwegy, Halima 01 January 2014 (has links)
The hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or more directions and have nine independent material constants are defined as orthotropic panels, and they achieve high specific strength. This thesis presents the effect of different patch orientations on the resulting strain and stress concentrations at the area of interaction between the panel and the patch. As it is known, the behavior of stiffened plates is affected by several important parameters, e.g., length to width ratio of the panel, stiffener geometry and spacing, aspect ratio for plates between stiffeners, plate slenderness, von Mises stresses, initial distortions, boundary conditions, and type of loading. A finite element model of the ship hull has been developed and run on ABAQUS (commercially available finite element software). The stiffened panel and patch are modeled as equivalent orthotropic plates made of steel. The panel edges are considered to be simply supported, and uniaxial tension was applied to the equivalent stiffened panel in addition to the lateral pressure (from water interaction). The developed model successfully predicted the optimal orientation of the panel for maximum stress concentration reduction. Moreover, in order to minimize the severe conditions caused by the mismatch that occurs if the material properties of the patch and the panel are the same during the patching process, it is necessary to stiffened the patch more than the panel. The developed model also suggested that an isotropic layer be added at the interaction to decrease the severity of arising stresses.
78

回顧型選擇權的評價與分析--間斷時間模型 / An Efficient Procedure for Valuing Lookback Options--Discrete Time Model

黃育智 Unknown Date (has links)
本篇論文比較了現有評價回顧型選擇權的眾多模型,結果發現Babbs[2000]在評價浮動履約價回顧型選擇權有較佳的效果。然而,在實務上,許多回顧型選擇權契約的訂定都是依照每日、每週、或是每禮拜的收盤價作為回顧的觀察時點,並非連續的觀察時點。因此,我們修正了Babbs[2000]的方法去評價美式與歐式間斷觀察時間點的回顧型選擇權價值。結果發現,回顧型賣權在連續時間下的價值比間斷時間下的價值高出許多。這意謂著,假使我們用連續時間的模型去評價間斷時間條款的回顧型選擇權,將造成相當大的誤差。因此,確實有發展間斷時間下評價回顧型選擇權方法的必要,而本篇論文所提出的方法在評價的結果上也令人滿意。 / This paper presents an efficient procedure for valuing floating strike lookback options in continuous-time. In practice, however, most contracts are based on the extrema of prices sampled at a finite set of fixed dates. We modify the method of Babbs [2000] to value finite sampling European and American lookback options in discrete-time. At the same time, we investigate the difference in option values between continuous and finite sampling. We find that the problem of overvaluing is more serious in valuing finite sampling lookback puts by continuous-time model. In addition, we derive a numerical method to value partial lookback options which incorporate the cost-reduction feature in the premium of lookback options.
79

亞士選擇權的效率評價--Hull&White模型的延伸與應用

張舒宜, shu yi chang Unknown Date (has links)
本文以Hull&White評價亞式選擇權(算數平均式選擇權)的模型為基礎來評價一般式的亞式選擇權。所謂一般性的亞式選擇權指的是一般市場上衍生性商品或結構型商品所常看到的亞式條款。 Hull&White評價亞式選擇權的模型設計路徑函數紀錄所需標的資產價格的方式解決了亞式選擇權的評價困難,並且具有良好的效率(比蒙地卡羅法快20倍以上)。但是Hull&White的評價模型對於評價的條款形式卻有許多的限制,使得具有良好效率的模型無法用於評價市場上一般常見的平均式條款。因此本文的目的就是對Hull&White的模型做擴充,使得其模型可用於一般商品常設計的亞式條款上。 本文對Hull&White模型所做的擴充主要是針對一般常見的平均條款:取特定或固定某些日期平均的亞式選擇權(如四季平均選擇權)、取特定某一段期間內標的資產價格平均的亞式選擇權(如最後一個月平均選擇權)及移動平均選擇權。擴充後的模型的評價效果非常具效率,且與蒙地卡羅法所評價的結果相比可快1000~10000倍以上,也解決了Hull&White一定要納入期出標的資產價格的假設。尤其在評價移動平均選擇權時,由於移動平均的結構與Hull&White所評價的亞式選擇結構有較大的差異,因此在對模型做擴充時所做的修正與調整較多,但其結果仍較其他評價方法更具效率。
80

FINITE DISJUNCTIVE PROGRAMMING METHODS FOR GENERAL MIXED INTEGER LINEAR PROGRAMS

Chen, Binyuan January 2011 (has links)
In this dissertation, a finitely convergent disjunctive programming procedure, the Convex Hull Tree (CHT) algorithm, is proposed to obtain the convex hull of a general mixed–integer linear program with bounded integer variables. The CHT algorithm constructs a linear program that has the same optimal solution as the associated mixed-integer linear program. The standard notion of sequential cutting planes is then combined with ideasunderlying the CHT algorithm to help guide the choice of disjunctions to use within a new cutting plane method, the Cutting Plane Tree (CPT) algorithm. We show that the CPT algorithm converges to an integer optimal solution of the general mixed-integer linear program with bounded integer variables in finitely many steps. We also enhance the CPT algorithm with several techniques including a “round-of-cuts” approach and an iterative method for solving the cut generation linear program (CGLP). Two normalization constraints are discussed in detail for solving the CGLP. For moderately sized instances, our study shows that the CPT algorithm provides significant gap closures with a pure cutting plane method.

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