O setor varejista de móveis e eletrodomésticos encontra-se em expansão e é diretamente afetado pela competividade do mercado. As empresas do setor buscam constantemente a redução dos preços e dos prazos de entrega dos produtos, para manterem a sua posição perante os concorrentes. Um dos fatores que influenciam diretamente a competitividade dessas organizações são os elevados custos do sistema de distribuição. A fim de reduzir os impactos no sistema de distribuição, o presente estudo teve por objetivo propor um modelo de apoio à tomada de decisão para a localização de centros de distribuição no setor varejista de móveis e eletrodomésticos. O trabalho foi dividido em três etapas para a sua concepção. Na primeira etapa utilizou-se um modelo por programação não-linear para definir um ponto ótimo na região abordada no estudo e posteriormente foram identificadas cinco cidades em torno desse ponto ótimo. A segunda etapa foi composta pela definição dos critérios e subcritérios influentes na decisão, e pela aplicação do método AHP para a seleção da melhor cidade para a instalação do centro de distribuição. Na terceira etapa buscou-se identificar o melhor terreno entre três alternativas, que foram avaliadas pelo método AHP a partir da definição dos critérios e subcritérios voltados a esse contexto de decisão. Os resultados apresentados mostram que o fator transporte e mercado são os principais responsáveis para a escolha da cidade, e a instalação e acessibilidade para a localização do terreno. O estudo identificou a alternativa Arapongas como a melhor cidade e o terreno três como o melhor local para a instalação do centro de distribuição. / The retail sector of furniture and appliances is in expansion and is directly affected by market competitiveness. The Companies in this sector are constantly seeking reduction of prices and delivery times of products, to maintain their position before competitors. One of the factors that directly influence the competitiveness of these organizations are the high costs of the distribution system. In order to reduce the impacts on the distribution system, the present study aimed to propose a model to support decision making for the location of distribution centers in the retail sector of furniture and appliances. The work divided into three stages for its conception. In the first stage was used a non-linear programming model to define an optimal point in the region covered in the study and subsequently been identified five cities around that optimal point. The second stage was composed by defining criteria and sub-criteria that influence the decision, and the application of AHP method for selecting the best city for installing the distribution center. In the third stage is sought to identify the best ground among three alternatives, that been evaluated by AHP method from the definition of criteria and sub-criteria directed this decision context. The result show that the factor transport and market are mainly responsible for choosing the city, and the installation and accessibility to the location of the ground. The study identified the alternative Arapongas as the best city and the ground 3 as the best place to install the distribution center.

O setor varejista de móveis e eletrodomésticos encontra-se em expansão e é diretamente afetado pela competividade do mercado. As empresas do setor buscam constantemente a redução dos preços e dos prazos de entrega dos produtos, para manterem a sua posição perante os concorrentes. Um dos fatores que influenciam diretamente a competitividade dessas organizações são os elevados custos do sistema de distribuição. A fim de reduzir os impactos no sistema de distribuição, o presente estudo teve por objetivo propor um modelo de apoio à tomada de decisão para a localização de centros de distribuição no setor varejista de móveis e eletrodomésticos. O trabalho foi dividido em três etapas para a sua concepção. Na primeira etapa utilizou-se um modelo por programação não-linear para definir um ponto ótimo na região abordada no estudo e posteriormente foram identificadas cinco cidades em torno desse ponto ótimo. A segunda etapa foi composta pela definição dos critérios e subcritérios influentes na decisão, e pela aplicação do método AHP para a seleção da melhor cidade para a instalação do centro de distribuição. Na terceira etapa buscou-se identificar o melhor terreno entre três alternativas, que foram avaliadas pelo método AHP a partir da definição dos critérios e subcritérios voltados a esse contexto de decisão. Os resultados apresentados mostram que o fator transporte e mercado são os principais responsáveis para a escolha da cidade, e a instalação e acessibilidade para a localização do terreno. O estudo identificou a alternativa Arapongas como a melhor cidade e o terreno três como o melhor local para a instalação do centro de distribuição. / The retail sector of furniture and appliances is in expansion and is directly affected by market competitiveness. The Companies in this sector are constantly seeking reduction of prices and delivery times of products, to maintain their position before competitors. One of the factors that directly influence the competitiveness of these organizations are the high costs of the distribution system. In order to reduce the impacts on the distribution system, the present study aimed to propose a model to support decision making for the location of distribution centers in the retail sector of furniture and appliances. The work divided into three stages for its conception. In the first stage was used a non-linear programming model to define an optimal point in the region covered in the study and subsequently been identified five cities around that optimal point. The second stage was composed by defining criteria and sub-criteria that influence the decision, and the application of AHP method for selecting the best city for installing the distribution center. In the third stage is sought to identify the best ground among three alternatives, that been evaluated by AHP method from the definition of criteria and sub-criteria directed this decision context. The result show that the factor transport and market are mainly responsible for choosing the city, and the installation and accessibility to the location of the ground. The study identified the alternative Arapongas as the best city and the ground 3 as the best place to install the distribution center.

Orientador: Francisco A. M. Gomes Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-16T18:35:34Z (GMT). No. of bitstreams: 1 LopesJr._RicardodeOliveira_M.pdf: 1018281 bytes, checksum: aa6f5adb041720d76a549b50e09fdcb2 (MD5) Previous issue date: 2010 / Resumo: Este trabalho apresenta um sistema remoto de resolução de problemas de otimização através da internet. O usuário visita a página do sistema, escolhe o programa de otimização que deseja utilizar, submete o seu problema e recebe a solução na tela ou por correio eletrônico. O objetivo do sistema é popularizar as bibliotecas computacionais desenvolvidas no país, assim como atender à demanda de pesquisadores e empresas por programas de otimização. No momento, estão disponíveis os pacotes GENCAN e ALGENCAN. O sistema permite que se use derivadas automáticas, geradas pelo pacote Adol-C, caso o programa exija o uso de derivadas e o usuário não possa fornecê-las. Uma fila de compilação e uma fila de processamento controlam o fluxo de submissões de problemas. O usuário pode visualizar essas filas e cancelar um trabalho submetido / Abstract: This work presents a remote system for solving optimization problems over the internet. The user visits the system website, chooses the optimization solver and submits a problem. The solution may be visualized in the browser window or by email. The objective of the system is to popularize the solvers developed by Brazilian researchers, as well as to meet the demand of researchers and companies for optimization programs. So far, the packages GENCAN and ALGENCAN are available. If the solver needs the derivatives of the functions and the user is not able to supply them, the system permits the use of automatic differentiation, generated by the Adol-C package. A compilation queue and an execution queue control the server submission flow. The user may visualize these queues and cancel a submitted job / Mestrado / Matematica Aplicada / Mestre em Matemática

The choice of active-constraint logic for screening inequalities has a major impact on the performance of gradient-projection method. It has been found that least-constrained strategies, which keep the number of constraints in the active set as small as possible, are computationally most efficient. However, these strategies are often prone to cycling of constraints between active and inactive status. This occurs mainly due to the violation of some of the constraints, taken as inactive, by the resulting step. This research develops methods for choosing an active set such that constraints in the active set satisfy the Kuhn-Tucker conditions and the resulting step does not violate the linear approximations to any of the constraints satisfied as equalities but considered inactive. Some of the existing active-constraint logics, specifically the dual-violator rule, yield the desired active set when two constraints are satisfied as equalities. However, when three or more constraints are satisfied as equalities, none of the existing logics give the desired active set. A number of general results, which help in the selection of the active set, have been developed in this research. An active-constraint logic has been developed for the case of three constraints. This logic gives the desired active-set. For the general case, when more than three constraints are satisfied as equalities, a separate active-set logic is suggested. This guarantees the nonviolation of the linear approximations to any of the constraints, taken as inactive, by the resulting step. The resulting active-set may not, however, satisfy the Kuhn-Tucker conditions. The efficiency of the proposed logic was tested computationally using quadratic programming problems. Three existing active-set strategies were used for comparision. The proposed logic almost always performed as well or better than the best among the three existing active-set strategies. / Ph. D.

The solution to the problem of a satellite with a small constant thrust and under the influence of a central force field presents difficulties due to equations non-linearity. An investigation was made to determine what range of values of the thrust parameter could be utilized to obtain a valid approximate solution for the case of tangential thrusting. The investigation was accomplished by developing programs for the 1620 High Speed Digital Computer, since the solution to the exact and approximate equations would otherwise be exceedingly laborious. Under the assumption of no atmosphere, and neglecting the earth's oblateness, the study showed that the validity of the Kryloff and Bogoliuboff method was dependent on both the specific thrust aud the vehicle speed. For a Speed corresponding to an orbit of smaller eccentricity it was determined that the method of Kryloff and Bogoliuboff remained valid for larger values of W than when V was a velocity corresponding to an orbit with a greater eccentricity. The method of Kryloff and Bogoliuboff represents a practical approach to the solution of satellite motion both from the aspect of ease of application and reasonable calculation times. / Master of Science

With the rise of online retailer giants like Amazon, and enhancements in internet and mobile technologies, online shopping is becoming increasingly popular. This has lead to new opportunities in online price optimization. The overarching motivation and theme of this thesis is to review these opportunities and provide methods and models in the context of retailers' online pricing decisions. In Chapter 2 a multi-period revenue maximization and pricing optimization problem in the presence of reference prices is formulated as a mixed integer nonlinear program. Two algorithms are developed to solve the optimization problem: a generalized Benders' decomposition algorithm and a myopic heuristic. This is followed by numerical computations to illustrate the effciency of the solution approaches as well as some managerial pricing insights. In Chapter 3 a data-driven quadratic programming optimization model for online pricing in the presence of customer ratings is proposed. A new demand function is developed for a multi-product, nite horizon, online retail environment. To solve the optimization problem, a myopic pricing heuristic as well as exact solution approaches are introduced. Using customer reviews ratings data from Amazon.com, a new customer rating forecasting model is validated. This is followed by several analytical and numerical insights. In Chapter 4 a multinomial choice model is used for customer purchase decision to find optimal personalized price discounts for an online retailer that incorporates customer locations and feedback from their reviews. Closed form solutions are derived for two special cases of this problem. To gain some analytical insights extensive numerical experiments are carried followed by several analytical and numerical insights. / Thesis / Doctor of Philosophy (PhD) / The increase in online retail and the improvements in mobile technologies has lead to advantages and opportunities for both customers and retailers. One of these advantages is the ability to keep and efficiently access records of historical orders for both customers and retailers. In addition, online retailing has dramatically decreased the cost of price adjustments and discounts compared to the brick and mortar environment. At the same time, with the increase in online retailing we are witnessing proliferations of online reviews in e-commerce platforms. Given this availability of data and the new capabilities in an online retail environment, there is a need to develop pricing optimization models that integrate all these new features. The overarching motivation and theme of this thesis is to review these opportunities and provide methods and models in the context of retailers' online pricing decisions.

Muitos problemas de otimização envolvem tanto variáveis inteiras quanto contínuas e podem ser modelados como problemas de programação não-linear inteira mista. Problemas dessa natureza aparecem com freqüência em engenharia química e incluem, por exemplo, síntese de processos, projeto de colunas de destilação, síntese de rede de trocadores de calor e produção de óleo e gás. Neste trabalho, apresentamos algoritmos baseados em Lagrangianos Aumentados e branch and bound para resolver problemas de programação não-linear inteira mista. Duas abordagens são consideradas. Na primeira delas, um algoritmo do tipo Lagrangianos Aumentados é usado como método para resolver os problemas de programação não-linear que aparecem em cada um dos nós do método branch and bound. Na segunda abordagem, usamos o branch and bound para resolver os problemas de minimização em caixas com variáveis inteiras que aparecem como subproblemas do método de Lagrangianos Aumentados. Ambos os algoritmos garantem encontrar a solução ótima de problemas convexos e oferecem recursos apropriados para serem usados na resolução de problemas não convexos, apesar de não haver garantia de otimalidade nesse caso. Apresentamos um problema de empacotamento de retângulos em regiões convexas arbitrárias e propomos modelos para esse problema que resultam em programas não-lineares com variáveis inteiras e contínuas. Realizamos alguns experimentos numéricos e comparamos os resultados obtidos pelo método descrito neste trabalho com os resultados alcançados por outros métodos. Também realizamos experimentos com problemas de programação não-linear inteira mista encontrados na literatura e comparamos o desempenho do nosso método ao de outro disponível publicamente. / Many optimization problems contain both integer and continuous variables and can be modeled as mixed-integer nonlinear programming problems. Problems of this nature appear frequently in chemical engineering and include, for instance, process synthesis, design of distillation columns, heat exchanger network synthesis and oil and gas production. In this work, we present algorithms based on Augmented Lagrangians and branch and bound for solving mixed-integer nonlinear programming problems. Two approaches are considered. In the first one, an Augmented Lagrangian algorithm is used for solving nonlinear programming problems that appear at each node in the branch and bound method. In the second approach, we use a branch and bound method for solving box-constrained problems with integer variables that appear as subproblems of the Augmented Lagrangian algorithm. Both algorithms guarantee to find an optimal solution for convex problems and have appropriate strategies to deal with non-convex problems, although there is no guarantee of optimality in this case. We present a problem of packing rectangles within an arbitrary convex region and propose models for this problem that result in nonlinear programs with integer and continuous variables. We have performed some numerical experiments and compared the results reached by the method described in this work and the results obtained by other methods. We have also performed experiments with mixed-integer nonlinear programming problems found in the literature and compared the performance of our method to that of other method publicly available.

Muitos problemas de otimização envolvem tanto variáveis inteiras quanto contínuas e podem ser modelados como problemas de programação não-linear inteira mista. Problemas dessa natureza aparecem com freqüência em engenharia química e incluem, por exemplo, síntese de processos, projeto de colunas de destilação, síntese de rede de trocadores de calor e produção de óleo e gás. Neste trabalho, apresentamos algoritmos baseados em Lagrangianos Aumentados e branch and bound para resolver problemas de programação não-linear inteira mista. Duas abordagens são consideradas. Na primeira delas, um algoritmo do tipo Lagrangianos Aumentados é usado como método para resolver os problemas de programação não-linear que aparecem em cada um dos nós do método branch and bound. Na segunda abordagem, usamos o branch and bound para resolver os problemas de minimização em caixas com variáveis inteiras que aparecem como subproblemas do método de Lagrangianos Aumentados. Ambos os algoritmos garantem encontrar a solução ótima de problemas convexos e oferecem recursos apropriados para serem usados na resolução de problemas não convexos, apesar de não haver garantia de otimalidade nesse caso. Apresentamos um problema de empacotamento de retângulos em regiões convexas arbitrárias e propomos modelos para esse problema que resultam em programas não-lineares com variáveis inteiras e contínuas. Realizamos alguns experimentos numéricos e comparamos os resultados obtidos pelo método descrito neste trabalho com os resultados alcançados por outros métodos. Também realizamos experimentos com problemas de programação não-linear inteira mista encontrados na literatura e comparamos o desempenho do nosso método ao de outro disponível publicamente. / Many optimization problems contain both integer and continuous variables and can be modeled as mixed-integer nonlinear programming problems. Problems of this nature appear frequently in chemical engineering and include, for instance, process synthesis, design of distillation columns, heat exchanger network synthesis and oil and gas production. In this work, we present algorithms based on Augmented Lagrangians and branch and bound for solving mixed-integer nonlinear programming problems. Two approaches are considered. In the first one, an Augmented Lagrangian algorithm is used for solving nonlinear programming problems that appear at each node in the branch and bound method. In the second approach, we use a branch and bound method for solving box-constrained problems with integer variables that appear as subproblems of the Augmented Lagrangian algorithm. Both algorithms guarantee to find an optimal solution for convex problems and have appropriate strategies to deal with non-convex problems, although there is no guarantee of optimality in this case. We present a problem of packing rectangles within an arbitrary convex region and propose models for this problem that result in nonlinear programs with integer and continuous variables. We have performed some numerical experiments and compared the results reached by the method described in this work and the results obtained by other methods. We have also performed experiments with mixed-integer nonlinear programming problems found in the literature and compared the performance of our method to that of other method publicly available.

Virtual Enterprise (VE) is an organizational collaboration concept which provides a competitive edge in the globalized business environment. The life cycle of a VE consists of four stages i.e. opportunity identification (Pre-Creation), partner selection (Creation), operation and dissolution. The success of VEs depends upon the efficient execution of their VE-lifecycles along with knowledge enhancement for the partner enterprises to facilitate the future formation of efficient VEs. This research aims to study the different issues which occur in the VE lifecycle and provides a platform for the formation of high performance enterprises and VEs. In the pre-creation stage, enterprises look for suitable partners to create their VE and to exploit a market opportunity. This phase requires explicit and implicit information extraction from enterprise data bases (ECOS-ontology) for the identification of suitable partners. A description logic (DL) based query system is developed to extract explicit and implicit information and to identify potential partners for the creation of the VE. In the creation phase, the identified partners are analysed using different risks paradigms and a cooperative game theoretic approach is used to develop a revenue sharing mechanism based on enterprises inputs and risk minimization for optimal partner selection. In the operation phases, interoperability remains a key issue for seamless transfer of knowledge information and data. DL-based ontology mapping is applied in this research to provide interoperability in the VE between enterprises with different domains of expertise. In the dissolution stage, knowledge acquired in the VE lifecycle needs to be disseminated among the enterprises to enhance their competitiveness. A DL-based ontology merging approach is provided to accommodate new knowledge with existing data bases with logical consistency. Finally, the proposed methodologies are validated using the case study. The results obtained in the case study illustrate the applicability and effectiveness of proposed methodologies in each stage of the VE life cycle.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / OFDM has become the preferred modulation format for a wide range of wireless networks including 802.11g, 802.16e (WiMAX) and 4G LTE. For multipath channels which are time-invariant during an OFDM symbol duration, near-optimal demodulation is achieved using the FFT followed by scalar equalization. However, demodulating OFDM on the doubly-spread channel remains a challenging problem, as time-variations within a symbol generate intercarrier interference. Furthermore, demodulation and channel estimation must be effectively combined with decoding of the LDPC code in the 4G-type system considered here. This paper presents a new Turbo Equalization (TEQ) decoder, detector and channel estimator for OFDM on the doubly-spread channel based on nonlinear programming. We combine the Penalty Gradient Projection TEQ with a MMSE-type channel estimator (PGP-TEQ) that is shown to yield a convergent algorithm. Simulation results are presented comparing conventional MMSE TEQ using the Sum Product Algorithm (MMSE-SPA-TEQ) with the new PGP-TEQ for doubly-spread channels.