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Single and two-phase flows on chemical and biomedical engineering

Dias, Ricardo; Lima, R.; Martins, Antonio; Mata, Teresa
Fonte: Bentham Publicador: Bentham
Tipo: Livro
ENG
Relevância na Pesquisa
46.13%
Single or two-phase flows are ubiquitous in most natural process and engineering systems. Examples of systems or process include packed bed reactors, either single phase or multiphase, absorber and adsorber separation columns, filter beds, plate heat exchangers, flow of viscoelastic fluids in polymer systems, or the enhanced recovery of oil, among others. In each case the flow plays a central role in determining the system or process behaviour and performance. A better understanding of the underlying physical phenomena and the ability to describe is crucial to design, operate and control processes involving the flow of fluids, ensuring that they will be more efficient and cost effective. Growing areas such as microfluidics, nanomedicine and the modelling and simulation of complex flow in living systems such as the blood flow in microvascular networks rely upon a good description of the flow. One way of studying the blood flow behavior is in the context of blood flow in large arteries, and another is in small vessels. In the former case, blood may be treated as a homogenous fluid and Newtonian constitutive equations are generally accepted as a good approximation to express the rheological property of blood. In small vessels...

Numerical solution of the eXtended Pom-Pom model for viscoelastic free surface flows

OISHI, C. M.; MARTINS, F. P.; TOME, M. F.; CUMINATO, J. A.; MCKEE, S.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.97%
In this paper we present a finite difference method for solving two-dimensional viscoelastic unsteady free surface flows governed by the single equation version of the eXtended Pom-Pom (XPP) model. The momentum equations are solved by a projection method which uncouples the velocity and pressure fields. We are interested in low Reynolds number flows and, to enhance the stability of the numerical method, an implicit technique for computing the pressure condition on the free surface is employed. This strategy is invoked to solve the governing equations within a Marker-and-Cell type approach while simultaneously calculating the correct normal stress condition on the free surface. The numerical code is validated by performing mesh refinement on a two-dimensional channel flow. Numerical results include an investigation of the influence of the parameters of the XPP equation on the extrudate swelling ratio and the simulation of the Barus effect for XPP fluids. (C) 2010 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP - Fundacao de Amparo a pesquisa do Estado de Sao Paulo[04/16064-9]; FAPESP - Fundacao de Amparo a pesquisa do Estado de Sao Paulo[2009/15892-9]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico[304422/2007-0]; CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico[470764/2007-4]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico[477858/2009-0]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Royal Society of Edinburgh; Royal Society of Edinburgh

Sistemas de análises químicas em fluxo explorando multi-impulsão, interface única ou quimiometria; Flow systems exploiting multi-pumping, single interface or chemometry

Alves, Evandro Roberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/10/2009 PT
Relevância na Pesquisa
35.76%
Os sistemas de análises em fluxo com multi-impulsão (MPFS) têm como característica principal o emprego de bombas solenóide como unidade propulsora de fluidos, as quais proporcionam fluxo pulsado. Este regime de fluxo foi avaliado em função das condições de mistura entre as soluções envolvidas, transferência de calor e difusão gasosa. A associação dos métodos quimiométricos de análises e dos sistemas MPFS foi demonstrada em relação à determinação espectrofotométrica de glicose, frutose e glicerol em vinhos fermentiscíveis e caldos de cana-de-açúcar. O método se fundamentou na reação dos carboidratos com metaperiodato de sódio e posterior oxidação de iodeto pelo metaperiodato remanescente com monitoramento de [I3 -] produzido. O tratamento dos dados envolveu calibração multivariada, empregando o algoritmo PLS e os resultados são concordantes com aqueles obtidos por cromatografia líquida de troca aniônica com detecção por amperometria pulsada. O sistema proposto é simples e robusto, capaz de analisar 120 amostras por hora. O fluxo pulsado proporcionou melhoria no desenvolvimento reacional no que diz respeito à transferência de calor e difusão gasosa. Esse aspecto se deve principalmente ao aumento do transporte de massas no sentido radial. Estes fatos foram constatados na determinação espectrofotométrica de açúcares redutores totais (ART) e etanol. O sistema MPFS proposto para a determinação de ART envolveu hidrólise ácida da sacarose e degradação alcalina dos carboidratos. A natureza do fluxo pulsado possibilitou o uso de menores temperaturas de um banho termostatizado durante as etapas de hidrólise e degradação...

Numerical solution of the eXtended Pom-Pom model for viscoelastic free surface flows

Oishi, C. M.; Martins, F. P.; Tome, M. F.; Cuminato, J. A.; McKee, S.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 165-179
ENG
Relevância na Pesquisa
35.91%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 04/16064-9; Processo FAPESP: 09/15892-9; In this paper we present a finite difference method for solving two-dimensional viscoelastic unsteady free surface flows governed by the single equation version of the eXtended Pom-Pom (XPP) model. The momentum equations are solved by a projection method which uncouples the velocity and pressure fields. We are interested in low Reynolds number flows and, to enhance the stability of the numerical method, an implicit technique for computing the pressure condition on the free surface is employed. This strategy is invoked to solve the governing equations within a Marker-and-Cell type approach while simultaneously calculating the correct normal stress condition on the free surface. The numerical code is validated by performing mesh refinement on a two-dimensional channel flow. Numerical results include an investigation of the influence of the parameters of the XPP equation on the extrudate swelling ratio and the simulation of the Barus effect for XPP fluids. (C) 2010 Elsevier B.V. All rights reserved.

The role of hydrodynamic stress on the phenotypic characteristics of single and binary biofilms of Pseudomonas fluorescens

Simões, M.; Pereira, Maria Olívia; Vieira, M. J.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2006 ENG
Relevância na Pesquisa
35.81%
This study investigates the phenotype of turbulent (Re = 5200) and laminar (Re = 2000) flow-generated P. fluorescens biofilms. Three P. fluorescens strains, the type strain– ATCC 13525 and two strains isolated from an industrial processing plant - D3-348 and D3-350, were used throughout this study. The isolated strains were used to form single and binary biofilms. The biofilm physiology (metabolic activity, cellular density, mass, extracellular polymeric substances, structural characteristics and outer membrane proteins-OMP expression) was compared. The results indicate that, for every situation, turbulent flow-generated biofilms were more active (P < 0.05), had more mass per cm2 (P < 0.05), a higher cellular density (P < 0.05), distinct morphology, similar matrix proteins (P > 0.1) and identical (isolated strains - single and binary biofilms) and higher (type strain) matrix polysaccharides contents (P < 0.05) than laminar flow-generated biofilms. Flow-generated biofilms formed by the type strain revealed a considerable higher cellular density and amount of matrix polysaccharides than single and binary biofilms formed by the isolated strains (P < 0.05). Similar OMP expression was detected for the several single strains and for the binary situation...

The role of hydrodynamic stress on the phenotypic characteristics of single and binary biofilms of Pseudomonas fluorescens

Simões, M.; Pereira, Maria Olívia; Vieira, M. J.
Fonte: IWA Publishing Publicador: IWA Publishing
Tipo: Artigo de Revista Científica
Publicado em //2007 ENG
Relevância na Pesquisa
35.81%
This study investigates the phenotype of turbulent (Re=5,200) and laminar (Re=2,000) flowgenerated Pseudomonas fluorescens biofilms. Three P. fluorescens strains, the type strain ATCC 13525 and two strains isolated from an industrial processing plant, D3-348 and D3-350, were used throughout this study. The isolated strains were used to form single and binary biofilms. The biofilm physiology (metabolic activity, cellular density, mass, extracellular polymeric substances, structural characteristics and outer membrane proteins [OMP] expression) was compared. The results indicate that, for every situation, turbulent flow-generated biofilms were more active ( p <0.05), had more mass per cm2 ( p<0.05), a higher cellular density ( p <0.05), distinct morphology, similar matrix proteins ( p>0.1) and identical (isolated strains – single and binary biofilms) and higher (type strain) matrix polysaccharides contents ( p<0.05) than laminar flow-generated biofilms. Flow-generated biofilms formed by the type strain revealed a considerably higher cellular density and amount of matrix polysaccharides than single and binary biofilms formed by the isolated strains ( p <0.05). Similar OMP expression was detected for the several single strains and for the binary situation...

An electronic solution for the direct connection of a three-phase induction generator to a single-phase feeder

Machado,Ricardo Q.; Gonçalves,Amílcar F. Q.; Buso,Simone; Pomilio,José A.
Fonte: Sociedade Brasileira de Automática Publicador: Sociedade Brasileira de Automática
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2009 EN
Relevância na Pesquisa
35.79%
This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The power flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results.

The phase distribution of upward co-current bubbly flows in a vertical square channel

Matos,A. de; Rosa,E. S.; Franca,F. A.
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2004 EN
Relevância na Pesquisa
35.86%
In this work one shows experimental data and numerical results of the void fraction distribution in vertical upward air-water bubbly flows in a square cross-section channel. To measure the void fraction distribution one used a single wire conductive probe. The averaged void fraction ranged from 3.3% to 15%; the liquid and the gas superficial velocities varied from 0.9 m/s to 3.0 m/s and 0.04 m/s to 0.5 m/s, respectively. The experimental results for the void fraction distribution were compared with numerical calculation performed by an Eulerian-Eulerian implementation of the Two-Fluid Model. In this work one performs the turbulence modeling with three approaches: using an algebraic model, the k-epsilon two-phase model and the k-epsilon two-phase two-layer model. Comparisons between the experimental and numerical data revealed, in general, good agreement.

On the thermal and hydrodynamic characteristics of liquid-liquid Taylor flows

Mac Giolla, Eain Marc
Fonte: University of Limerick Publicador: University of Limerick
Tipo: info:eu-repo/semantics/doctoralThesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations
ENG
Relevância na Pesquisa
36.03%
peer-reviewed; Two phase liquid-liquid flows offer significant heat and mass transfer enhancements over single phase flows and, as a result, have found use in numerous emerging technologies employing microfluidics. Such technologies include lab-on-chip devices for chemical and biological diagnostics, and biosensors. Liquid-liquid flows have also shown potential for use in high-heat flux removal systems. Although these flows are found in numerous applications, little is known about the complex fluid mechanics that govern them. Consequently, there is a need for a greater knowledge base to serve as a foundation for future system design and characterisation. This thesis presents a fundamental investigation of the hydrodynamic and thermal characteristics of liquid-liquid slug or Taylor flows confined to minichannel geometries. There were three principal aspects to this thesis, which encompassed the measurement of film thickness, pressure drop and heat transfer in liquid-liquid Taylor flows. Experiments were carried out using a number of different carrier fluids – while maintaining water as the dispersed phase throughout. Dimensionless slug length, Capillary and Reynolds numbers were varied over several orders of magnitude. High speed imaging was used in conjunction with microscopy to measure the mean slug velocity and liquid film thickness. Images of the dispersed slugs revealed that the thickness of the liquid film was not constant along the length of the slug. However...

The Evolution of Agricultural Trade Flows

Aksoy, M. Ataman; Ng, Francis
Fonte: Banco Mundial Publicador: Banco Mundial
Relevância na Pesquisa
35.95%
Earlier research showed that during the 1980s and 1990s most of the global agricultural trade expansion took place among the industrial countries and among countries within trade blocs. These were also periods of declining agricultural prices. These prices increased during the 2000s, there were continuous trade reforms, and many developing countries started to support their agricultural sectors. This paper analyzes trade flows during the past two decades, and tries to measure whether all these developments have changed the trade balances and the share of different groups within the global trade flows. In addition, it looks at the trade balances on food to see the impact of these changes on net food importing countries. In conclusion, unlike the case with manufacturing, developing countries have not been able to increase their export shares in agriculture as significantly. They have maintained their trade shares by primarily expanding exports to other developing countries.

What Explains the Low Survival Rate of Developing Country Export Flows?

Brenton, Paul; Saborowski, Christian; von Uexkull, Erik
Fonte: Banco Mundial Publicador: Banco Mundial
Relevância na Pesquisa
35.95%
Successful export growth and diversification require not only entry into new export products and markets, but also the survival and growth of export flows. This paper uses a detailed, cross-country dataset of product level bilateral export flows to illustrate that exporting is an extremely perilous activity and especially so in low-income countries. The authors find that unobserved individual heterogeneity in product-level export flow data prevails despite controlling for a wide range of observed country and product characteristics. This questions previous studies that have used the Cox proportional hazards model to model export survival. The authors estimate a Prentice-Gloeckler model, amended with a gamma mixture distribution summarizing unobserved individual heterogeneity. The empirical results confirm the significance of a range of products as well as country-specific factors in determining the survival of export flows. From a policy perspective, an interesting finding is the importance of learning-by-doing for export survival: experience with exporting the same product to other markets or different products to the same market are found to strongly increase the chance of export survival. A better understanding of such learning effects could substantially improve the effectiveness of export promotion strategies.

The Impacts of Trade Facilitation Measures on International Trade Flows

de Sá Porto, Paulo C.; Canuto, Otaviano; Morini, Cristiano
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Trabalho em Andamento
EN_US
Relevância na Pesquisa
35.95%
This paper analyzes the impacts of selected trade facilitation measures on international trade flows. A gravity model is used to estimate four equations: a pooled cross-section model; a fixed-effects model; a random effects model; and a Poisson maximum likelihood estimator. The contribution of the paper is twofold. First, the analysis uses a recent data set, a panel that includes trade data from 2011 and 2012 for 72 countries. Second, to measure the impacts of trade facilitation measures, the analysis includes dummy variables for the presence of an authorized economic operator program, the existence of a single-window program in the countries in the sample, and the existence of a mutual recognition arrangement between pairs of countries in the sample. The results show that the presence of an authorized economic operator program and the existence of a single-window program will improve countries’ trade performance. By contrast, the existence of a mutual recognition arrangement will not necessarily improve countries’ trade performance. These results suggest that...

A high-flux solar simulator system for investigating the influence of concentrated solar radiation on turbulent reacting flows

Dong, X.; Ashman, P.; Nathan, G.
Fonte: Australian Solar Council; online Publicador: Australian Solar Council; online
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
35.86%
Simulations of the output from a high flux solar simulator are presented for a low cost system, designed to assess the influence of Concentrated Solar Radiation (CSR) on turblent flows. This radiant heat source comprises 30 X 6 kW Metal Halide lamsp, each positioned at the focus of an ellipsoidal reflector (3m focal length) and arrayed to provide 54 kW of radiative power (180 kWe). The simulator will be used in combination with a water-cooled heat sink to avoid background radiation from walls. In contrast to previous simulator designs that focus only on a single point, these lamps can be configured to focus along a line to provide a nominally homogeneous radiant flux within the targeted volume. A model, programmed in Matlab, is used to assess and optimize the radiant heat flux profile for different arrangements of the lamp array. A comparison of costs with previous simulator designs is also presented.; http://solar.org.au/solar2012/conference-papers/; X. Dong, P.J. Ashman and G.J. Nathan

Viscous-inviscid interaction analysis of incompressible cascade flows

Krainer, Andreas
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Relatório
EN_US
Relevância na Pesquisa
35.95%
The aerodynamic performance of turbomachines is limited by flutter, choking, and stall, the last of which being a topic of this report. Viscous flow considerations are not only essential in determining loss coefficients, but also in ascertaining loadings and in providing a fundamental understanding of the flow. However, because of the complexity' of flows in turbomachines flow problems of model character only are accessible to uumerical treatment. The focus of this report is on steady, incompressible, viscous. 2-d flows through a single infinite row of equidistant blades. In order to compute these cascade flows Prandtl's boundary layer concept enhanced by a strong interaction model is applied to the Navier-Stokes equations. Since this approach enables the integration of boundary layer equations in the presence of backflow. it is an attractive alternative to much more expensive Navier-Stokes solvers...; performed for the Naval Postgraduate School by Mr. A Krainer under contract number N62271-85-M-0437; http://archive.org/details/viscousinviscidi00krai

Should Capital Flows Be Regulated? A Look at the Issues and Policies

Islam, Roumeen
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Policy Research Working Paper; Publications & Research
ENGLISH; EN_US
Relevância na Pesquisa
35.95%
The author argues that externalities in financial markets, implicit and explicit guarantees on financial transactions, and information asymmetries in financial markets that may exacerbate contagion provide a rationale for a government role in managing the risk associated with cross-border capital flows. Governments can complement private sector risk management with measures that help deal with the volatility of capital flows. These measures include those that control the type and volume of capital flows and those that help investors make better investment decisions, and that may reduce herding behavior, such as better information provision. The main instruments that have been tried or recommended since the onset of the recent financial crises can be grouped in several categories. 1) Debt management: The composition, maturity structure, and level of external debt have played an important role in financial crises. High short-term debt relative to liquid assets has been found to be consistently correlated with financial crises in recent times. Governments can affect the level of debt (including private debt) and its composition...

Análise numérica detalhada de escoamentos multifásicos bidimensionais; Detailed two-dimensional numerical analysis of multiphase flows

Villar, Millena Martins
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
35.97%
A modelagem matemática de escoamentos multifásicos envolve a interação de geometrias móveis e deformáveis com o meio fluido que as envolve. Este tipo de interação faz parte de uma extensa lista de aplicações. Uma linha proposta para o tratamento num érico deste tipo de problema são os métodos híbridos Front-Tracking/Front-Capturing. Esta abordagem leva à separação do problema em dois domínios distintos (líquido/gás e líquido/líquido), um domínio fixo, euleriano, utilizado para discretizar as equações de ambas as fases, e outro móvel, lagrangiano, usado para as interfaces. Para o presente trabalho, na metologia utilizada, ambos os domínios são geometricamente independentes e não apresentam restrição quanto ao movimento e à deformação da fase dispersa. Seguindo esta linha, no presente trabalho propõe-se capturar detalhes deste de tipo escoamento, resolvendo adequadamente as escalas físicas do tempo e do espaço, utilizando malhas bloco estruturada refinadas localmente, as quais se adaptam dinamicamente para recobrir as regiões de interesse do escoamento (como, por exemplo, ao redor da interface fluido-fluido). Para se obter a resolução necessária no tempo, é usada uma discretização semi-implícita de segunda ordem para solucionar as equações de Navier-Stokes. A modelagem da turbulência é introduzida no presente trabalho via Simulação de Grandes Escalas. A eficiência e a robustez da metodologia implementada são verificadas via análise de convergência do método...

Análise do modelo de mistura aplicado em escoamentos isotérmicos gás-líquido; Analysis of mixture model applied in gas-liquid isothermals flows

Luiz Eduardo Melo Lima
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/07/2011 PT
Relevância na Pesquisa
35.91%
Escoamentos gás-líquido são frequentemente encontrados na natureza, bem como em diversas aplicações industriais. Na área de produção de petróleo, por exemplo, em sistemas de elevação natural ou artificial (gas-lift contínuo ou intermitente), gás e óleo escoam simultaneamente em tubulações. A previsão de escoamentos gás-líquido torna-se necessária à viabilidade técnica-econômica de muitos processos industriais, por exemplo, na indústria de petróleo devido ao aumento do consumo mundial de combustíveis e a descoberta de novos campos petrolíferos. Em escoamentos gáslíquido, as fases se distribuem espacialmente e temporalmente ao longo da tubulação dependendo das vazões, propriedades físicas das fases e das características da tubulação, entre outros parâmetros. A combinação destes fatores gera diversos padrões de escoamento gás-líquido que podem ser agrupados em três classes principais: disperso, separado e intermitente. Os principais objetivos deste trabalho são o desenvolvimento e a análise de uma modelagem unidimensional em regime permanente, baseada no modelo de mistura, que permita a simulação de escoamentos isotérmicos gás-líquido em tubulações com seção transversal circular constante...

El decaimiento libre de flujos turbulentos rotantes; The decay of rotating turbulent flows

Teitelbaum, Tomás
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2012 SPA
Relevância na Pesquisa
35.91%
En esta tesis se presenta un estudio detallado del decaimiento libre de flujos turbulentos rotantes tridimensionales (3D), y de flujos rotantes y estratificados en la aproximación cuasi-geostrófica de superficie, sometidos a distintas condiciones iniciales. En el caso de la turbulencia rotante 3D se usa la conocida cuasi- bidimensionalización para predecir los distintos decaimientos, proponiendo un método original que consiste en estudiar la energía presente en modos bidimensionales (2D) y 3D de manera independiente. Con el mismo fin, se introduce el uso de dos nuevas magnitudes conservadas anisótropas, relacionadas con el momento lineal y angular en la dirección paralela al eje de rotación. Los resultados indican que las leyes del decaimiento de la energía no son universales, dependiendo de la forma en que los flujos son excitados inicialmente. Las leyes de potencia observadas para el decaimiento son afectadas por las correlaciones en las escalas grandes, por la cantidad neta de helicidad presente inicialmente, por el grado inicial de anisotropía, y por la formación de estructuras coherentes. Para todos los casos estudiados se logra predecir las leyes de potencia observadas en las simulaciones mediante modelos fenomenológicos...

Shear flow and viscosity in single-layer hydraulics

Hogg, Andrew; Hughes, Graham
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.87%
We calculate solutions for one-layer hydraulically controlled flows with viscosity. Viscosity and bottom drag produce two key modifications to inviscid hydraulic theory: the position of the hydraulic control point is altered, and the solution requires kno

A heuristic approach for multi-product capacitated single-allocation hub location problems

Fernandes, Eliana Fabíola Correia
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2015 ENG
Relevância na Pesquisa
35.84%
Tese de mestrado, Estatística e Investigação Operacional, Universidade de Lisboa, Faculdade de Ciências, 2015; Em redes onde o fluxo entre nodos é muito elevado (como pode ser o caso do transporte de pessoas e mercadorias ou até mesmo fluxo de dados numa rede), torna-se menos dispendioso criar pontos onde se concentram os fluxos provenientes das diferentes origens para depois serem consolidados e redistribuídos até aos destinos. A esses pontos dá-se o nome de hubs. O problema de localização de hubs consiste na localização de hubs numa rede e na alocação de todos os nodos da rede a esses hubs, de modo a que se possa encaminhar os fluxos entre os pares origem-destino a menos que sejam hubs. A rede constituída pelos hubs é normalmente definida como completa e não se permitem ligações diretas entre os pares origem-destino. Para além disso, assume-se que existe um factor de desconto para o fluxo que circula entre hubs. Neste tipo de redes (hub-and-spoke networks) podem aparecer duas variantes, no que diz respeito à alocação dos nodos aos hubs: single-allocation e multiple-allocation. No primeiro caso, permite-se apenas uma ligação de cada nodo não hub a um hub de modo a que todo o fluxo com origem e destino a cada nodo saia e chegue a esse nodo através de apenas um hub. No caso em que se tem multiple-allocation...