Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 90-91).

Thesis (doctoral)--Katholieke Universiteit te Nijmegen, 1987. / Text in Dutch, with summaries in English and German. Vita. Includes bibliographical references (p. 185-193).

Orientador: José Roberto Nunhez / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-21T00:15:32Z (GMT). No. of bitstreams: 1 MorenoCardenas_Sebastian_M.pdf: 3545307 bytes, checksum: 797cf7a13df284eafac584f66c5d0826 (MD5) Previous issue date: 2012 / Resumo: Processos comerciais de hidrotratamento (HDT) normalmente operam em regime de leito gotejante "Trickle bed" em concorrente com fluxos descendentes de gás e de líquido, sobre um leito de partículas de catalisador onde ocorrem as reações. É bem conhecido que a remoção de enxofre é fortemente inibida pelo efeito de adsorção competitiva de H2S nos sítios ativos do catalisador. Como consequência disso, é importante manter a concentração de H2S tão baixa quanto possível nestes processos durante a reação para obter um produto com baixo teor de enxofre na saída do reator. De acordo com Ancheyta et al.(2007), um perfil mais conveniente de concentração seria obtido com um reator operando em contracorrente,. Por exemplo, poderia se introduzir a carga na parte superior e o H2 na parte inferior do reator. Assim, na parte inferior do reator, a concentração de H2S é menor e a concentração do H2 é maior, promovendo taxas mais elevadas de reação. Os principais problemas da operação em contracorrente são uma menor eficiência de contato líquido-gás e dificuldade de prevenção de inundação do reator. Com o objetivo de estudar estes processos com mais detalhes, um estudo fluidodinâmico tridimensional do reator em regime de gotejamento "trickle bed" em contracorrente foi realizado com o uso de técnicas de CFD (Fluidodinâmica Computacional), com ênfase na determinação da perda de carga e da distribuição do hold-up de líquido no leito. Um modelo com o uso de CFD tridimensional baseado na abordagem Euleriana - Euleriana foi utilizado para modelar a hidrodinâmica do leito do reator de leito gotejante operando em contracorrente. Os termos de fechamento interfases foram estimados pelo modelo de balanço de forças apresentado por Attou, A et al. (1999), o qual foi usado e validado por Gunjal e Ranade (2007). O perfil de distribuição radial da porosidade foi estimado com o uso da distribuição de Klerk (2003). O modelo foi resolvido com o uso do software comercial ANSYS-CFX 13. Neste documento pode-se encontrar uma revisão bibliográfica do CFD aplicado a reatores de leito gotejante. Posteriormente são mostrados o desenvolvimento matemático e método numérico empregado, e finalmente os resultados dos casos de estudo, os quais forneceram informação de distribuição do líquido, perfis de velocidades, queda de pressão e hold-up do líquido para reatores isotérmicos de leito fixo em escala laboratório (0,0254 m de diâmetro e 0,3 m de comprimento) escoando concorrente e contracorrente / Abstract: Commercial HDT processes usually operate in a trickle-bed regime, with co-current downward flow of gas and liquid over a randomly fixed bed of catalyst particles while reactions take place. It is well known that sulfur removal is strongly inhibited by the competitive adsorption effect of H2S at the sulfided active sites of the catalyst. As a consequence, it is important in these process to maintain the concentration of H2S as low as possible during the reaction to achieve a low sulfur content product at the outlet of reactor. According to Ancheyta et al. (2007), a more convenient profile of H2S concentration can be provided by operating the reactor in countercurrent mode, for instance, introducing the feed at the top and H2 at the bottom of the reactor. Thus, in the lower reactor, the H2S concentration is lower and H2 is greater, promoting higher reaction rates. The main problems of the operation counter are a lower efficiency of gas-liquid contact and difficulty in preventing flooding conditions. In order to investigate the above processes in more detail, a three-dimensional fluid-dynamic study of a countercurrent trickle bed reactor was carried out using CFD (Computational Fluid Dynamics) techniques with emphasis on determining the pressure drop and the distribution of liquid hold-up in the bed. A computational fluid dynamics (CFD) tridimensional model based on an Eulerian - Eulerian multiphase approach was used to model the hydrodynamics of the pseudo two-phase flow in a trickle bed reactor (TBR) in counter-current operation. The closure terms for phase interactions have been addressed by adopting the fluid-fluid interfacial force balance concept (Attou et al. 1999), which was used and validated to simulate co-current HDT reactors by Gunjal e Ranade (2007). Radial variation of porosity was estimated using the Klerk (2003) distribution. Above set of model equations were implemented in commercial software ANSYS-CFX Release 13. In this document it could be found a literature review of CFD models applied to trickle bed reactors, later a mathematical modeling and numerical method to solve the transport equations and finally the results of study cases, which provided information about phase distribution, velocity profiles, pressure drop liquid hold up for a isothermal trickle bed reactor at laboratory scale (0.0254 m diameter and 0.3 length) in co-current and counter-current operation / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Let f be a point-to-set mapping from a topological X space X into the family 2(X) of nonempty closed subsets of X . K. Fan [13] proved that if X is a Hausdorff locally convex linear topological space and K is a nonempty compact convex subset of X , then an upper semicontinuous mapping (abbreviated by u.s.c.) f from K into k(K), the family of nonempty closed convex subsets of K, has a fixed point in K . Our main object in this work is to weaken "compactness" of K to "weak compactness" and prove a fixed point theorem for a mapping f on K into certain subfamily of 2(K). The definition of convex function has been extended to point-to-set mappings in Chapter I. Let I denote the identity mapping on a Banach space X. Assume that I-f is a convex mapping on a weakly compact closed convex subset K of X. Then any of the following conditions implies the existence of the fixed point of f on K: (1) f : K → 2(K) is u.s.c. and [formula omitted] d(x,f(x)) = 0. (2) f : K → 2(K) is u.s.c. and is asymptotically regular (see definition 1.3) at some point in K . (3) f : K → cc(K) is nonexpansive and the Banach space X has a strictly convex norm. Moreover, it has been shown that if f : K → cpt(K) (see definition 0.3) is nonexpansive and I-f is strictly convex (see definition 1.5) on K, then K has a fixed point on K . Finally, an effort has been made to investigate the properties of the set of fixed points of a point-to-set mappings. In Chapter II, we have confined ourselves to a reflexive Banach space X which has a weakly continuous duality map J (see definition 2.3) and X has a strictly convex norm. On such a special space we are able to prove that a nonexpansive mapping f : X → cc(X) such that f(x)ʗ K, for any x in a closed convex bounded subset K of X , has a fixed point. As an application of this result we prove a fixed point theorem for semicontractive mappings (see definition 2.7). F : X → cc(X) such that F(x)ʗK for any x ε K , where K and X are the same as above. . In the last Chapter, we have proved that if f is strictly nonexpansive on a.Banach space X into cpt(X) and if there is x(o) ε X such that [formula omitted] has a subsequence convergent to a set A ε cpt(X) under the Hausdorff metric D on cpt(X), then f has a fixed point in A . Furthermore we prove that a nonexpansive mapping f : K → cpt(K), where K is a weakly compact convex subset of a metrizable locally convex linear topological space X, has a fixed point in K, provided that a constant k > 0 exists such that the set E(x) = {y ε K ; d(x,y) ≥ kd(y,f(y))} is nonempty and convex and the mapping E : K → k(K), with E(x) defined above, is weakly locally closed (see definition 3.1). Finally the comparisons of the continuities of a point-to-set mapping have been made. / Science, Faculty of / Mathematics, Department of / Graduate

No description available.

D.Econ. / Uncertainty is an element that pervades the very existence of man. As one moves through time, almost every decision that one takes is associated with some degree of uncertainty. As one departs from one moment in time to another, one's journey comprises choices and expectations relating to all matters of life. A choice is made when one decides to adopt one or more courses of action from a set of available alternatives. The uncertainty associated with each decision is not merely whether or not the correct choice was made, but more in terms of whether or not the expected outcome will be realised. The time between the moment a decision is made and the future moment in which the outcome is expected to be realised, is permeated with the essence of uncertainty.

In the study of differential equations there are two fundamental questions: is there a solution? and what is it? One of the most elegant ways to prove that an equation has a solution is to pose it as a fixed point problem, that is, to find a function f such that x is a solution if and only if f (x) = x. Results from fixed point theory can then be employed to show that f has a fixed point. However, the results of fixed point theory are often nonconstructive: they guarantee that a fixed point exists but do not help in finding the fixed point. Thus these methods tend to answer the first question, but not the second. One such result is Schauder’s fixed point theorem. This theorem is broadly applicable in proving the existence of solutions to differential equations, including the Navier-Stokes equations under certain conditions. Recently a semi-constructive proof of Schauder’s theorem was developed in Rizzolo and Su (2007). In this thesis we go through the construction in detail and show how it can be used to search for multiple solutions. We then apply the method to a selection of differential equations.

In the study, we choose the companys that had conducted IPOs or SEOs between 2005 and February 2006 as studying samples. The purpose of the study is to investigate how the issuing firms choose among different underwriting mechanisms and the factors influencing the choice of underwriting mechanisms. Empirical result shows that issuing factors are the important factors that influence the choice of underwriting mechanisms. The firms that conduct IPOs usually trend to choose bookbuilding method, but the firms that conduct SEOs trend to choose fixed price method instead. On the other hand, we also find that issuing scale is another significant factor influencing the choice of underwriting mechanisms and the effect is more apparent on the firms that conduct SEOs. The firms with bigger issuing scale trend to choose bookbuilding method but the firms with smaller issuing scale trend to choose fixed price rather than bookbuilding method.

In the microprocessor development, the high performance microprocessor applies the x86 complex instruction set is used widely. And the signal-core architecture towards slowly to multi-core one .But the variable-length instruction still creates the difficulties in instruction fetching and affects the whole executive- performance. There has the mechanism which supported the split-line and fetched fleetly the variable-lengths instruction. It has the problem in high time and hardware complexity, because it was accomplished with additional hardware. Accordingly, this paper proposed a fixed-length instruction set with design in compatible and extended x86 instruction set used the fixed-length instruction form to solve the difficulties in fetching the variable-length instructions. We considered the factor an overall arrangement of memory space and decided the length 4 bytes and 8 bytes to formulate the fixed-length instruction set. And we used the following six transitionary rules to complete the formulation for the coded form of the fixed-length instructions.(1)We used the auxiliary registers to save the value to decrease the data dependence between the original registers.(2)If it could use a few instructions to complete the translation with the original registers, we used the original registers to do it.(3)The complex case instructions were coded with eight bytes.(4)It did sign-extension by itself when displacement and immediate were moved to the auxiliary registers.(5)The auxiliary registers with the diacritic prefix were only coded in the r/m field or the index field.(6)One of displacement field and immediate field was moved first when its length was longer. And we considered the hardware complexity of saving memory space and fetching instructions, we analyzed the categories of instruction packages to compress the program space to decrease the space loss which the fixed-lengths of instructions created. In the case of verifiable and experimental framework, the CINT2006 was used to be benchmarks. And the function which translated the fixed-length instructions was succeeded to execute. It was successful to achieve the purpose the program space was compressed efficiently in the instruction package mechanism.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): E. Cory Yoder, David V. Lamm. Includes bibliographical references (p. 97-100). Also available online.