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Avaliação do ciclo de vida de produtos têxteis: implicações da alocação; Life cycle assessment of textile products: implications from allocation

Arduin, Rachel Horta
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/10/2013 PT
Relevância na Pesquisa
36.71%
Os estudos de Avaliação do Ciclo de Vida (ACV) aplicados ao setor têxtil tiveram inicio na década de 1990, sendo realizados principalmente nos Estados Unidos e na Europa. No Brasil, os estudos de ACV aplicados a produtos têxteis utilizando dados nacionais iniciaram nos últimos dois anos. As normas ISO 14040 e 14044 fornecem a estrutura indispensável para a ACV, no entanto, ainda que balizadas por recomendações, certas escolhas metodológicas são realizadas pelo executor do estudo. Na maioria dos ciclos de vida do produto, há pelo menos um processo que tem mais de um produto como saída, e para o qual não é possível coletar dados em separado, sendo necessário aplicar um procedimento de alocação. O presente trabalho teve como objetivo avaliar a influência da aplicação de diferentes procedimentos de alocação no resultado final de um estudo de ACV aplicado à produção de fibras têxteis, através da análise de estudos publicados e da realização de estudo de caso. A revisão dos estudos publicados na literatura baseou-se no método de revisão bibliográfica sistemática. Dentre as publicações que apresentaram o procedimento de alocação selecionado, o que representa apenas 34% dos estudos, a alocação econômica foi realizada em sete estudos...

Alocação dinâmica de tarefas periódicas em NoCs malha com redução do consumo de energia; Energy-aware dynamic allocation of periodic tasks on mesh NoCs

Wronski, Fabio
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.71%
O objetivo deste trabalho é propor técnicas de alocação dinâmica de tarefas periódicas em MPSoCs homogêneos, com processadores interligados por uma rede emchip do tipo malha, visando redução do consumo de energia do sistema. O foco principal é a definição de uma heurística de alocação, não se considerando protocolos de escalonamento distribuído, uma vez que este ainda é um primeiro estudo para o desenvolvimento de um alocador dinâmico. Na arquitetura alvo utilizada, cada nodo do sistema é dado como autônomo, possuindo seu próprio escalonador EDF. Além disso, são aplicadas técnicas de voltage scaling e power managmenent para redução do consumo de energia durante o escalonamento. Durante a pesquisa do estado da arte, não foram encontradas técnicas de alocação dinâmica em NoCs com restrições temporais e minimização do consumo de energia. Por isso, esse trabalho se concentra em avaliar técnicas de alocação convencionais, como bin-packing e técnicas baseadas em teoria de grafos, no contexto de sistemas embarcados. Dessa forma, o modelo de estimativas do consumo de energia de alocações é baseado no escalonamento de grafos de tarefas, e foi utilizado para implementar a ferramenta Serpens com este propósito. Os grafos de tarefas utilizados nos experimentos são tirados do benchmark E3S – Embedded System Synthesis Benchmark Suite...

Project management : multiple resources allocation

Tereso, Anabela Pereira; Araújo, Maria Madalena Teixeira de; Moutinho, Rui; Elmaghraby, Salah
Fonte: International Conference on Engineering Optimization Publicador: International Conference on Engineering Optimization
Tipo: Conferência ou Objeto de Conferência
Publicado em /06/2008 ENG
Relevância na Pesquisa
36.71%
Given a project network under stochastic conditions, the goal is to determine the optimal resource allocation to the activities in order to minimize the total project cost. This cost includes the resource cost and the tardiness cost. In this work we consider the multiple resources case, which is an extension of the models previously developed by the rst author and other researchers, considering a single resource. We assume that all the resources are independent and abundant. The work consists mainly of two parts: formalization of the new models, and their implementation in Java. In order to formalize the models, it was necessary to establish an allocation strategy for the multiple resources. This is required to ensure the desired equality of expected durations yielded by each resource in the same activity. We study four di erent allocation strategies: two of them are derived from the stochastic nature of the work content by equalizing the expected durations, thus determining the allocation vectors; and the other two go down to the level of all possible values to devise an allocation method (among all the allocation vectors, selects those leading to equal expected durations). Then the probability distributions of the variables required for analysis and evaluation were determined. Although the research has covered four strategies...

A novel distributed power allocation scheme for coordinated multicell systems

Silva, Adão; Holakouei, Reza; Castanheira, Daniel; Gameiro, Atílio; Dinis, Rui
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.74%
Coordination between base stations (BSs) is a promising solution for cellular wireless systems to mitigate intercell interference, improving system fairness, and increasing capacity in the years to come. The aim of this manuscript is to propose a new distributed power allocation scheme for the downlink of distributed precoded multicell MISO-OFDM systems. By treating the multicell system as a superposition of single cell systems we define the average virtual bit error rate (BER) of one single-cell system, allowing us to compute the power allocation in a distributed manner at each BS. The precoders are designed in two phases: first the precoder vectors are computed in a distributed manner at each BS considering two criteria, distributed zero-forcing and virtual signal-to-interference noise ratio; then the system is optimized through distributed power allocation with per-BS power constraint. The proposed power allocation scheme minimizes the average virtual BER over all user terminals and the available subcarriers. Both the precoder vectors and the power allocation are computed by assuming that the BSs have only knowledge of local channel state information. The performance of the proposed scheme is compared against other power allocation schemes that have recently been proposed for precoded multicell systems based on LTE specifications. The results also show that although our power allocation scheme is based on the minimization of the virtual uncoded BER...

Adaptively Parallel Processor Allocation for Cilk Jobs

Sen, Siddhartha; Agrawal, Kunal
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 16407 bytes; application/pdf
EN_US
Relevância na Pesquisa
36.82%
The problem of allocating processor resources fairly and efficiently to parallel jobs has been studied extensively in the past. Most of this work, however, assumes that the instantaneous parallelism of the jobs is known and used by the job scheduler to make its decisions. In this project, we consider different ways of estimating the parallelism of jobs during runtime, as well as different ways of using this information to allocate processors in a fair and efficient manner. The goal of our project is to design and implement a dynamic processor-allocation system for adaptively parallel jobs. Adaptively parallel jobs are jobs for which the number of processors which can be used without waste—in other words, the parallelism of each job—varies during execution. We call the problem of allocating processors to adaptively parallel jobs the adaptively parallel processor-allocation problem. We propose to investigate the adaptively parallel processor-allocation problem for jobs running on a shared-memory multiprocessor (SMP) system. We focus on the specific case of parallel jobs that are scheduled with the randomized work-stealing algorithm, as is used in the Cilk multithreaded language (later, we will expand the scope of our research to include other kinds of parallel jobs). Our problem can be defined as follows: Consider an SMP system with P processors and J jobs. At any given time...

Using Cyclic Memory Allocation to Eliminate Memory Leaks

Nguyen, Huu Hai; Rinard, Martin C.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 112069 bytes; application/pdf
EN
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36.71%
We present and evaluate a new memory management technique for eliminating memory leaks in programs with dynamic memory allocation. This technique observes the execution of the program on a sequence of training inputs to find m-bounded allocation sites, which have the property that at any time during the execution of the program, the program only accesses the last m objects allocated at that site. The technique then transforms the program to use cyclic memory allocation at that site: it preallocates a buffer containing m objects of the type allocated at that site, with each allocation returning the next object in the buffer. At the end of the buffer the allocations wrap back around to the first object. Cyclic allocation eliminates any memory leak at the allocation site - the total amount of memory required to hold all of the objects ever allocated at the site is simply m times the object size. We evaluate our technique by applying it to several widely-used open source programs. Our results show that it is able to successfully eliminate important memory leaks in these programs. A potential concern is that the estimated bounds m may be too small, causing the program to overlay live objects in memory. Our results indicate that our bounds estimation technique is quite accurate in practice...

Do glucocorticoids mediate resource allocation in breeding tree swallows (Tachycineta bicolor)?

Dobson, Emily
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
36.71%
All individuals allocate limited resources towards self-maintenance (meeting energy requirements for growth and development) and reproduction (producing and rearing offspring). Different physiological systems of the body attempt to balance these processes in order to maximize lifetime reproductive success. The precise mechanisms underlying adaptive allocation towards competing life history traits are unknown. One possible mechanism of mediating resource allocation is through the release of glucocorticoid (GC) hormones. Corticosterone (cort) is the primary GC found in birds, reptiles and amphibians and a good candidate for mediating shifts in resource allocation because (1) challenges that result in reduced energy availability, such as food limitation or disease, induce increased secretion of baseline cort, and (2) cort secretion can result in mobilization of energy stores. To investigate the effects of cort on resource allocation, we conducted two complementary studies in tree swallows (Tachycineta bicolor). First, we compared birds that received cort-implants with birds that received control-implants and un-implanted controls to identify causal effects of increased cort on resource allocation. We found no significant effect of implant type on measures of reproductive effort...

Assessing Fiscal Implication of the Recent Changes in Poverty Lines and Revision of Allocation Norms of Capital Expenditures and Resources for Targeted Programs

World Bank
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
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There have been important changes in the budgeting process in Vietnam since 2006 when the government of Vietnam instituted a revolutionary reform in the management and allocation of the state budget. For the period of 2007-2010, the norms include ethnic minority population data, and poverty rates. The purpose of this research assignment is to describe the evolution of budgeting mechanisms in recent years, in association with capital expenditure transferred from central to provincial budgets. This report focuses on changes in the budgeting process and allocation norms. It is also assesses whether these recent changes are pro-poor, and how they would affect availability of resources for the national targeted programs.

Capital allocation in insurance: Economic capital and the allocation of the default option value

Sherris, Michael; van der Hoek, John
Fonte: Society of Actuaries Publicador: Society of Actuaries
Tipo: Conference paper
Publicado em //2004 EN
Relevância na Pesquisa
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The determination and allocation of economic capital is important for pricing, risk management and related insurer financial decision making. This paper considers the allocation of economic capital to lines of business in insurance. We show how to derive closed form results for the complete markets, arbitrage-free allocation of the insurer default option value, also referred to as the insolvency exchange option, to lines of business. We assume that individual lines of business and the surplus ratio are joint log-normal although the method we adopt allows other assumptions. The allocation of the default option value is required for fair pricing in the multi-line insurer. We illustrate some other methods of capital allocation and give numerical examples for the capital allocation of the default option value based on explicit payoffs by line.; http://www.soa.org/Library/Journals/NAAJ/2006/april/naaj0602_3.aspx; Michael Sherris and John van der Hoek

Coevolving a computer player for resource allocation games : using the game of Tempo as a test space.

Avery, Phillipa Melanie
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
46.81%
Decision-making in resource allocation can be a complex and daunting task. Often there exist circumstances where there is no clear optimal path to choose, and instead the decision maker must predict future need and allocate accordingly. The application of resource allocation can be seen in many organizations, from military, to high end commercial and political, and even individuals living their daily life. We define resource allocation as follows: the allocation of owner’s assets to further the particular cause of the owner. We propose two ways that computers can assist with the task of resource allocation. Firstly they can provide decision support mechanisms, with alternate strategies for the allocations that might not have been previously considered. Secondly, they can provide training mechanisms to challenge human decision makers in learning better resource allocation strategies. In this research we focus on the latter, and provide the following general hypothesis: Coevolutionary algorithms are an effective mechanism for the creation of a computer player for strategic decision-making games. To address this hypothesis, we present a system that uses coevolution to learn new strategies for the resource allocation game of TEMPO. The game of TEMPO provides a perfect test bed for this research...

Case studies that illustrate disinvestment and resource allocation decision-making processes in health care: A systematic review

Polisena, Julie; Clifford, Tammy; Elshaug, Adam Grant; Mitton, Craig; Russell, Erin; Skidmore, Becky
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
36.71%
OBJECTIVE: Technological change accounts for approximately 25 percent of health expenditure growth. To date, limited research has been published on case studies of disinvestment and resource allocation decision making in clinical practice. Our research objective is to systematically review and catalogue the application of frameworks and tools for disinvestment and resource allocation decision making in health care. METHODS: An electronic literature search was executed for studies on disinvestment, obsolete and ineffective technologies, and priority healthcare setting, published from January 1990 until January 2012. Databases searched were MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, Embase, The Cochrane Library, PubMed, and HEED. RESULTS: Fourteen case studies on the application of frameworks and tools for disinvestment and resource allocation decisions were included. Most studies described the application of program budgeting and marginal analysis (PBMA), and two reports used health technology assessment (HTA) methods for coverage decisions in a national fee-for-service structure. Numerous healthcare technologies and services were covered across the studies. We describe the multiple criteria considered for decision making...

Science in the cloud: Allocation and execution of data-intensive scientific workflows

Szabo, C.; Sheng, Q.; Kroeger, T.; Zhang, Y.; Yu, J.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
36.74%
An important challenge for the adoption of cloud computing in the scientific community remains the efficient allocation and execution of data-intensive scientific workflows to reduce execution time and the size of transferred data. The transferred data overhead is becoming significant with emerging scientific workflows that have input/output files and intermediate data products ranging in the hundreds of gigabytes. The allocation of scientific workflows on public clouds can be described through a variety of perspectives and parameters, and has been proved to be NP-complete. This paper proposes an evolutionary approach for task allocation on public clouds considering data transfer and execution time. In our framework, a solution is represented using an allocation chromosome that encodes the allocation of tasks to nodes, and an ordering chromosome that defines the execution order according to the scientific workflow representation. We propose a multi-objective optimization that relies on a cloud cost model and employs tailored evolution operators. Starting from a population of possible solutions, we employ crossover and mutation operators on both chromosomes aiming at optimizing the data transferred between nodes as well as the total workflow runtime. The crossover operators combine parts of solutions to reduce data overhead...

Geschichte und Ethik der Verteilungsverfahren von Nierentransplantaten durch EUROTRANSPLANT; History and ethics of kidney allocation via EUROTRANSPLANT

Galden, Daniel
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.71%
Seit Ende der Sechziger Jahre werden Nierentransplantate über die niederländische Organaustauschorganisation EUROTRANSPLANT vergeben. Von September 1968 bis Januar 2004 erschienen insgesamt 190 EUROTRANSPLANT-Newsletters, deren Daten die Grundlage der vorliegenden Studie bilden. Innerhalb dieser Zeitspanne nahm die Evolution der Allokationsalgorithmen unter dem Einfluss der politischen und gesellschaftlichen Entwicklungen in Deutschland und in Europa sowie der wissenschaftlichen Fortschritte in den Bereichen Immunsuppression, Gewebeverträglichkeitstestung, Konservierungstechnik und Informationsverarbeitung weniger einen geradlinig-konstruktiven als vielmehr pragmatisch-reaktiven Weg. Wenngleich medizinische Gründe von Anfang an dazu zwangen, die Transplantate entsprechend der Histokompatibilität zu vergeben, wuchs das Spektrum der Auswahlkriterien kontinuierlich an. Entsprechend gewannen die Vergabesysteme zunehmend an Komplexität und ermöglichen heute die multidimensionale Berücksichtigung zahlreicher Subkollektive einer überaus heterogenen Warteliste. Vor dem Hintergrund der traditionsreichen gerechtigkeitsphilosophischen und utilitaristischen Moraltheorien, aber auch der Motive der Dringlichkeit, Zentrumsökonomie und Verbundsstabilität folgte auf eine frühe experimentelle Phase bis Anfang der Achtziger Jahre ein konzeptionell aktives Jahrzehnt...

A transaction-based method for allocation of transmission grid cost and losses

Usaola, Julio
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: application/pdf; text/plain
Publicado em 05/10/2005 ENG
Relevância na Pesquisa
36.76%
The problem of grid cost and losses allocation may be divided into independent subproblems: allocation of branch flow and losses to transactions, definition of these transactions and cost allocation to transactions. From this final allocation, the charges to participants in transactions may be made straightforwardly. A differential, slack-invariant method for the allocation of flow and losses to transactions that makes use of the AC load flow equation is presented here. The definition of transactions must be addressed using a non-discriminatory rule in pool systems. There are many possible options for this definition, and the choice made has great influence on the results. Cost allocation, on the other hand, may be made in different ways, as well. The paper presents an allocation process that addresses all these issues. Results for the IEEE-RTS96 test system are obtained and discussed.

Approximations of stochastic household models for comparing antiviral allocation schemes.

Lydeamore, Michael John
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2015
Relevância na Pesquisa
36.81%
From the first recorded influenza pandemic in 1890, there have been new strains of influenza which have caused pandemics approximately every 30 years including recent events such as the H5N1 Avian 'Flu pandemic and the 2009 H1N1 Swine 'Flu pandemic. Although the 2009 pandemic was mild in nature, if events of the past are any indication then control of future pandemics is of utmost importance. Vaccination is commonly looked at to help control the spread of a pandemic, however, vaccinations are strain-specific. While developing a new vaccine is possible, the World Health Organisation estimates that this process would take four to five months. This means that vaccination cannot be used to help control the spread of influenza early on in a pandemic. An alternative are antivirals which are not strain-specific, meaning that they can potentially be used to help control the spread of influenza early on in a pandemic. Antivirals are, however, not as effective at reducing the spread of disease when compared to vaccination. In the 2009 Swine 'Flu pandemic, many countries worldwide utilised antiviral medication, with the aim to assist in controlling the spread of influenza. The most common method in which these antivirals were utilised we refer to as dynamic allocation. In dynamic allocation...

Transmission resource allocation in multi-antenna wireless communication systems with channel uncertainty

Zhou, Xiangyun
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN_AU
Relevância na Pesquisa
36.76%
In this thesis we investigate the design of transmission resource allocation in current and future wireless communication systems. We focus on systems with multiple antennas and characterize their performance from an information-theoretic viewpoint. The goal of this work is to provide practical transmission and resource allocation strategies taking into account imperfections in estimating the wireless channel, as well as the broadcast nature of the wireless channel. In the first part of the thesis, we consider training-based transmission schemes in which pilot symbols are inserted into data blocks to facilitate channel estimation. We consider one-way training-based systems with and without feedback, as well as two-way training-based systems. Two-way training enables both the transmitter and the receiver to obtain the channel state information (CSI) through reverse training and forward training, respectively. In all considered cases, we derive efficient strategies for transmit time and/or energy allocation among the pilot and data symbols. These strategies usually have analytical closed-form expressions and can achieve near optimal capacity performance evidenced by extensive numerical analysis. In one-way training-based systems without feedback...

In Vitro Development and Cell Allocation After Aggregation of Syngeneic Wild Type and Fluorescence-Expressing Bovine Cloned Embryos

Vieira, Fabiano Koerich; Forell, Fabiana; da Costa Gerger, Renato Pereira; de Aguiar, Luis Henrique; Feltrin, Cristiano; Gaudencio Neto, Saul; Mendez Calderon, Carlos Enrique; Carneiro, Igor de Sa; Bressan, Fabiana Fernandes; Urio, Monica; da Costa, Ubira
Fonte: UNIV FED RIO GRANDE DO SUL; PORTO ALEGRE RS Publicador: UNIV FED RIO GRANDE DO SUL; PORTO ALEGRE RS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.76%
Background: The in vitro production (IVP) of embryos by in vitro fertilization or cloning procedures has been known to cause epigenetic changes in the conceptus that in turn are associated with abnormalities in pre- and postnatal development. Handmade cloning (HMC) procedures and the culture of zona-free embryos in individual microwells provide excellent tools for studies in developmental biology, since embryo development and cell allocation patterns can be evaluated under a wide range of embryo reconstruction arrangements and in in vitro embryo culture conditions. As disturbances in embryonic cell allocation after in vitro embryo manipulations and unusual in vivo conditions during the first third of pregnancy appear to be associated with large offspring, embryo aggregation procedures may allow a compensation for epigenetic defects between aggregated embryos or even may influence more favorable cell allocation in embryonic lineages, favoring subsequent development. Thus, the aim of this study was to evaluate in vitro embryo developmental potential and the pattern of cell allocation in blastocysts developed after the aggregation of handmade cloned embryos produced using syngeneic wild type and/or transgenic somatic cells. Materials...

IMPROVING FEDERAL ALLOCATION OF EQIP FUNDING

Qin, Jianming; Neal, Ashley; Gilbert, Emily; Liu, Jiemei
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 24/04/2013 EN_US
Relevância na Pesquisa
36.74%
The motivation behind this report is to evaluate and respond to past and current decision pathways employed for determining state allocation of the Environmental Quality Incentives Program [EQIP] funding under the Natural Resource Conservation Service [NRCS]. We work to provide justifiable recommendations for how the allocation of EQIP dollars might be improved, especially as it pertains to improving equity among those states with the highest priority needs. In this project, we worked with our client, a Program Analyst at the North Carolina NRCS office, to tailor our recommendations to the specific concerns of one state. Our client’s specific concern was that North Carolina has historically been positioned lower in the national ranking of EQIP funding that it receives as compared to many other large agricultural states. We reviewed the history of EQIP, examined the past and current decision pathways used to determine federal allocation of conservation dollars to state NRCS offices, conducted interviews among NRCS staff, and quantitatively analyzed the funding allocation process. We provide scenarios for how it might be possible for a state like North Carolina to increase its allocation of EQIP funding and attain better conservation on identified lands of highest priority. In this project...

Improving Federal Allocation of EQIP Funding

Gilbert, Emily; Liu, Jiemei; Qin, Jianming; Neal, Ashley
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 25/04/2013 EN_US
Relevância na Pesquisa
36.79%
The motivation behind this report is to evaluate and respond to past and current decision pathways employed for determining state allocation of the Environmental Quality Incentives Program [EQIP] funding under the Natural Resource Conservation Service [NRCS]. We work to provide justifiable recommendations for how the allocation of EQIP dollars might be improved, especially as it pertains to improving equity among those states with the highest priority needs. The distribution mechanism of federal EQIP funding to each state has received significant criticism in the past. The criticism stems primarily from the usage of a weighted factor formula that has been thought to unfairly favor certain states over others. Beyond questions of equity, there have also been more fundamental concerns over the quality of data inputted into the funding formula. In this project, we worked with our client, a Program Analyst at the North Carolina NRCS office, to tailor our recommendations to the specific concerns of one state. Our client’s specific concern was that North Carolina has historically been positioned lower in the national ranking of EQIP funding that it receives as compared to many other large agricultural states. To better understand the process of federal EQIP allocation...

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
36.76%
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...