The elimination of distribution inefficiencies, occurring due to the timing of customers' orders is an important reason for companies to introduce vendor managed inventory programs. By managing their customers' inventories, suppliers may be able to reduce demand variability and therefore distribution costs. We develop technology to measure the effectiveness of distribution strategies. We develop a methodology that allows the computation of tight lower bounds on the total mileage required to satisfy customer demand over a period of time. As a result, companies will be able to gain insight into the effectiveness of their distribution strategy. This technology can also be used to suggest desirable delivery patterns and to analyze tactical and strategic decisions. Secondly, we study the inventory routing problem with continuous moves (IRP-CM). The typical inventory routing problem deals with the repeated distribution of a single product, from a single facility, with an unlimited supply, to a set of customers that can all be reached with out-and-back trips. Unfortunately, this is not always the reality. We introduce the IRP-CM to study two important real-life complexities: limited product availabilities at facilities and customers that cannot be served using out-and-back tours. We need to design delivery tours spanning several days, covering huge geographic areas, and involving product pickups at different facilities. We develop a heuristic and an optimization algorithm to construct distribution plans. The heuristic is an innovative randomized greedy algorithm, which includes linear programming based postprocessing technology. To solve the IRP-CM to optimality, we give a time-discretized integer programming model and develop a branch-and-cut algorithm. As instances of time-discretized models tend to be large we discuss several possibilities for reducing the problem size. We introduce a set of valid inequalities, called delivery cover inequalities, in order to tighten the bounds given by the LP relaxation of the time-discretized model. We also introduce branching schemes exploiting the underlying structure of the IRP-CM. An extensive computational study demonstrates the effectiveness of the optimization algorithm. Finally, we present an integrated approach using heuristics and optimization algorithms providing effective and efficient technology for solving inventory problems with continuous moves.

published_or_final_version / Computer Science and Information Systems / Master / Master of Philosophy

Um dos desafios na operação de uma cadeia de suprimentos é a definição de uma política de controle dos estoques de forma a manter a estabilidade dos estoques, evitando a amplificação da demanda ao longo da cadeia e atendendo adequadamente o cliente. A política de controle do estoque determina o momento (ponto de pedido) e a quantidade (tamanho do lote) adequada de reposição dos estoques nos diferentes elos da cadeia. Esta tese propõe um novo procedimento de atualização do ponto de pedido e do lote de reposição para uma política Order-Up-To-Level (OUTL) de controle dinâmico de estoques em sistemas de revisão contínua. Este procedimento altera a política OUTL clássica ao introduzir o conceito de estoque de absorção, caracterizado pela demanda de mercado e pelo lead time de cada elo da cadeia, que ajusta o ponto de pedido e o tamanho do lote a partir da ocorrência de eventos. Para tanto, uma cadeia de suprimentos mono-produto composta de três níveis produtivos (varejista, distribuidor e manufatura) é simulada por eventos discretos considerando incerteza na demanda. O desempenho da cadeia de suprimentos é avaliado por métricas para o efeito chicote, nível de serviço ao cliente, responsividade, nível e ruptura do estoque, tamanho do lote e ponto de reposição. Os resultados mostram redução do efeito chicote, melhora no nível de serviço, redução da variabilidade dos lotes e melhor estabilidade dos estoques quando comparados com a política OUTL clássica. / The inventory control policy is a challenge in supply chain operation. It has to maintain inventory stability by avoiding amplification of the market demand in the supply chain levels while keeping good custom service. The inventory control policy determines the correct time (reorder point) and quantity (lot size) to fill inventories of the supply chain levels. This thesis proposes a new procedure to update both reorder points and lot sizes for an inventory control policy Order-Up-To-Level (OUTL) in continuous review systems. The new procedure modifies the classical OUTL policy by introducing the concept of absorption inventory characterized by the market demand and lead time in each chain level. This procedure updates order points and lot sizes when particular events have occurred. A mono-product supply chain composed by three levels (retailer, distribution, and manufacturing) is simulated by a discrete event simulation considering uncertainty in demand. The supply chain performance is evaluated by several metrics taking into account the bullwhip effect, customer service level, responsiveness, inventory level and stock out, and lot sizes and reorder points. The results show that the bullwhip effect and lot size variability are reduced, service level is improved, and inventories are stable when compared with the classical OUTL policy.

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-05-03T18:50:04Z No. of bitstreams: 1 CARDOSO_Fabio_2016.pdf: 71020829 bytes, checksum: e1413b4896bf3ed023f3e1c2ca8eb956 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-05-03T18:50:11Z (GMT) No. of bitstreams: 1 CARDOSO_Fabio_2016.pdf: 71020829 bytes, checksum: e1413b4896bf3ed023f3e1c2ca8eb956 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-05-03T18:50:17Z (GMT) No. of bitstreams: 1 CARDOSO_Fabio_2016.pdf: 71020829 bytes, checksum: e1413b4896bf3ed023f3e1c2ca8eb956 (MD5) / Made available in DSpace on 2017-05-03T18:50:22Z (GMT). No. of bitstreams: 1 CARDOSO_Fabio_2016.pdf: 71020829 bytes, checksum: e1413b4896bf3ed023f3e1c2ca8eb956 (MD5) Previous issue date: 2016-09-12 / Não recebi financiamento / Logistics has been a differentiator more and more important among automakers, since quality, price and technical characteristics have been moving towards a common ground. In order to seek for additional differentiation, companies focus on strategies of stock allocation that allow them to either increase revenue or reduce costs. Stock allocation strategies within the companies requires the decision between centralizing and decentralizing stocks. Present research aims at investigating the decision process about stock allocation for auto parts in aftersales Market, and analyzing what the important criteria for such a decision are. It was conducted a descriptive research with that purpose. It was investigated relevant criteria within literature and validated through questionnaires performed with dealership. Because dealers are the ultimate responsible for the brand image to the customer, they also participated in criteria and alternatives ponderations. Then, it was possible to suggest a final decision for stock allocation, through the organization of all criteria and alternatives in a decision tree together with their weights. Research results seems to suggest the necessity that automakers focus the aftersales resources in increasing their service level to dealership through stock decentralization, as a method to increase their revenue in long-term. Present research contributes to management because it investigates which are the relevant criteria and their weight for centralization decision. In addition, the use of multi-criteria decision making aid to suggest a postponement decision in auto parts distribution chain also represent a contribution. / A logística é um diferenciador cada vez maior entre empresas automobilísticas concorrentes, dada a equiparação da qualidade, dos preços e características notada nos veículos. Ao buscar essa diferenciação, as empresas privilegiam estratégias de alocação de estoques que permitam o aumento de sua receita e/ou a redução de seus custos. As estratégias de alocação de estoques de uma empresa privilegiam a centralização ou descentralização dos estoques. O objetivo geral desta pesquisa é investigar o processo de decisão acerca da alocação de estoques de peças de reposição para o mercado de pós-vendas, ao analisar quais critérios são relevantes para essa decisão. Com esse objetivo, foi realizada uma pesquisa descritiva. Os critérios relevantes para a decisão foram investigados na literatura e validados através de questionários realizados com concessionárias. Sendo a concessionária uma grande responsável pela imagem final da marca diante do cliente, elas participaram ainda na ponderação desses critérios e também das alternativas. Foi possível então sugerir uma decisão para alocação de estoques, através da organização dos critérios e alternativas ponderados em uma árvore de decisão. Os resultados da pesquisa apontam para a necessidade de as montadoras descentralizarem suas distribuições de autopeças, elevando assim o nível de serviço para as concessionárias, como meio de elevarem suas receitas no longo-prazo. Esta pesquisa possui contribuições gerenciais de curto e de longo prazos. Em adição, o uso de técnicas de apoio à decisão multicritério para decisões sobre o uso de postergação para cadeias de distribuição também representa uma contribuição em si.

Este trabalho tem por objetivo propor um método eficiente para avaliar gestão de estoque, aplicando conjuntamente a Teoria de Controle Ótimo (OCT), para obter funções de estocagem dinamicamente ótimas, e Análise Envoltória de Dados (DEA), para calcular as eficiências relativas. Tendo em vista esse objetivo foi desenvolvido um modelo integrado DEA-OCT para calcular a eficiência de custo otimizada ao longo do tempo, quando o sistema possui variáveis relacionadas entre si, como no caso de sistemas de controle de estoque, e para analisar produção e demanda (assim como a variável estoque, oriunda dessa relação), estendendo o modelo variacional. Este trabalho aplica o modelo proposto a 647 empresas das Américas do Sul e do Norte, depois faz uma comparação entre Brasil e Chile (países emergentes economicamente), posteriormente focando no setor de comércio, considerando seus sistemas produção-estoque com dados de variáveis contábeis. Os modelos minimizam os custos de produção e de estoque para calcular a eficiência de custo ao longo do tempo. O output (produto, ou variável de saída) é a demanda; o input (insumo, ou variável de entrada) é a produção, e o intermediate (variável intermediária) é o estoque. Seus custos são considerados na função objetivo. É acrescentada uma restrição variacional da OCT para descrever a relação entre demanda, produção e estoque. Em resumo, o modelo é relevante por calcular eficiência prevenindo a possibilidade de obter uma projeção que ignora a relação entre as variáveis, uma vez que essa relação sempre ocorre, na prática, em sistemas de controle de estoque. As principais contribuições são: possibilitar o uso de OCT como a ferramenta de benchmarking DEA no contexto de eficiência dinâmica, estender o modelo DEA variacional de Sengupta (1995), incluindo restrições de modelos mais recentes e possibilitar o cálculo de eficiência quando há relação entre as variáveis. / This work aims to propose an efficient method to evaluate inventory management, jointly applying optimal control theory (OCT), obtaining dynamically optimal production and inventory functions, and data envelopment analysis (DEA), calculating the relative efficiencies. With this objective in mind, it was developed a DEA-OCT integrated model to calculate allocative efficiency optimized over time, when systems have variable with relationship among themselves, like in the case of inventory control systems, and for analyzing production and demand (as the inventory variable obtained from this relationship), extending the variational model. This paper applies the proposed model to 647 companies from South and North America, after that it was made a comparison between Brazil and Chile (economically emerging countries), then focusing on the commercial sector, considering its production-inventory systems and data from accounting variables. The model minimizes the inventory and production costs to calculate the allocative efficiency over time. The output is demand; the input is production, and the intermediate variable is inventory. Their costs are considered in the objective function. A variational constraint OCT is added to describe the relationship among demand, production, and inventory. In summary, the model is relevant to calculate efficiency by preventing the possibility of finding a projection that ignores the relationship among variables, since this relationship always occur in practice in inventory control systems. The main contributions are: using OCT as the benchmarking tool DEA in the context of dynamic efficiency, extending the Sengupta (1995) variational DEA model, including constraints from recent model and making it possible to calculate efficiency when there is a relationship among variables.

Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-10-16T18:00:48Z No. of bitstreams: 2 Dissertação - Wilder Francisco Soares Costa - 2014.pdf: 2068928 bytes, checksum: 053e3f6ebe769a97bc3032d2a3af31b9 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Rejected by Luciana Ferreira (lucgeral@gmail.com), reason: Na citação 0 nome do mestrado é Mestrado Profissional em Matemática em Rede Nacional. No final da citação coloque ponto final. on 2015-10-19T13:51:53Z (GMT) / Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-10-20T14:51:37Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Wilder Francisco Soares Costa - 2014.pdf: 2068928 bytes, checksum: 053e3f6ebe769a97bc3032d2a3af31b9 (MD5) / Approved for entry into archive by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-10-20T15:15:33Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Wilder Francisco Soares Costa - 2014.pdf: 2068928 bytes, checksum: 053e3f6ebe769a97bc3032d2a3af31b9 (MD5) / Made available in DSpace on 2015-10-20T15:15:33Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Wilder Francisco Soares Costa - 2014.pdf: 2068928 bytes, checksum: 053e3f6ebe769a97bc3032d2a3af31b9 (MD5) Previous issue date: 2014-10-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Inventory control plays an important role in business because they help the financial structure and understanding of it. Due to this fact is of great value that high school students seize their definitions and applications as they are or will be included in the labor market. The purpose of this work was to unite the inventory control with stochastic process, which in this case was the Markov process, through mathematical modeling. To this end, a brief explanation of inventory control and stock was addressed, as stochastic processes and examples, arriving on the Markov Chain that was addressed in a very simple way geared more for matrix multiplication and how to get these matrices. Then took these theories and applied, through modeling, at a small supermarket in inventory control of tomato sauce using Markov chains, allowing a prediction of future orders with the supplier. The work is the result of the Professional Masters and was written with the intention that teachers and high school students can understand the resolutions of the examples presented. / O controle de estoque exerce um papel importante nas empresas, pois auxiliam na estrutura financeira e compreensão da mesma. Devido esse fato é de grande valor que estudantes do ensino médio apreendam suas definições e aplicações pois estão ou serão inseridos no mercado de trabalho. O proposito deste trabalho foi unir o controle de estoque com o processo estocástico, que nesse caso foi o processo Markoviano, através da modelagem matemática. Para tanto, uma breve explanação de controle de estoque e estoque foi abordada, bem como processos estocásticos e exemplificações, chegando nas Cadeias de Markov que foi abordada de uma forma bem simples voltada mais para multiplicação de matrizes e como chegar nessas matrizes. Depois pegou essas teorias e foi aplicada, através da modelagem, em um supermercado de pequeno porte no controle de estoque de molho de tomate usando as cadeias de Markov, possibilitando a previsão de pedidos futuros junto ao fornecedor. O trabalho é fruto do Mestrado Profissional e foi escrito com intenção de que docentes e estudantes do ensino médio possam compreender as resoluções dos exemplos apresentados.

La presente investigación consiste en Proponer una Solución para Reducir los Reclamos en el Abastecimiento de Repuestos de Productos de Línea Blanca. Para ello, se aplicó principalmente Métodos de Clasificación ABC, Diagramas de Análisis de Actividades, Distribución por Mezcla de Familias, Métodos de Pronósticos de la Demanda, entre otras herramientas de la Ingeniería Industrial. Finalmente, se concluyó que al mejorar la Productividad del “Picking” (Sacado) y del Embalaje, al mejorar la Identificación y Reconocimiento Visual de los Repuestos y de los Espacios y al realizar una mejor Planificación de la Demanda, un adecuado Control del Inventario, una mejor Planificación del Abastecimiento, se reducirán los Reclamos en el Abastecimiento de Repuestos de productos de línea blanca. The present research is to propose a solution to Reduce Claims in supply of spare parts Products Appliances. To do this, we will mainly apply ABC classification methods, diagrams Analysis Activities, Distribution mix of families Methods demand forecast and other tools of industrial engineering. Finally, it was concluded that by improving the productivity of the "Picking" (Taken) and packaging, improving the identification and Visual Recognition of parts and spaces and improving planning Demand with an adequate control of inventory and with a better supply planning, Claims will be reduced in the Supply of white goods´ spare parts.

The purpose of this project was to develop a tool / utility for network administrators to maintain information about all the systems operated by the College of Natural Sciences at California State University, San Bernardino.

This master´s thesis deals with problems of inventory control optimalization in a business company. It contains theory data, company analyses and its market position, an analysis of information systems and inventory control in use, its evaluation and own recommendation leading to the optimalization.

Lagerhantering avser aktiviteter som mottagning av varor, inlagring, lagring, orderplockning, omlagring, sortering och frakt. Enligt tidigare studier, av bland annat Drury (1988), uppstår 55% - 60% av lagrets kostnader i orderplockning och omlagring. Idag finns teorier och modeller om hur lagerhantering kring orderplockning och omlagring kan optimeras. Dock behandlas bulklager sällan i forskning eller litteratur. Detta arbete hade således i syfte att undersöka vedertagen teoris anpassningsförmåga på en verksamhet med bulklager. Studien har uppfyllt syftet genom en fall- och litteraturstudie med både kvalitativa och kvantitativa tillvägagångssätt i form av intervjuer och observationer. Lagerutformning och lagerstyrning kan med fördel ses som grundläggande metoder som förutsätter effektivitetsutveckling inom plockning och omlagring i bulklager. Metoder som MUDA och 5S skapar förutsättningarna att identifiera, upprätthålla och genomföra effektivitetsförbättringar.  De vedertagna metoderna som studerats kunde genom observation och intervju konstateras som implementerbar eller icke implementerbar. Som sammanfattning kunde en övergripande mall av metoderna sammanställas där det gemensamt och separat kunde bidra till effektivisering. Fallföretaget kunde förses med förbättringsförslag som rekommenderas att införas i både mindre etapper och under större, mer omfattande projekt. / Inventory management refers to activities such as receiving goods, storing, in storage, order picking, rearranging, sorting and shipping. According to previous studies, by Drury (1988), 55% - 60% of the warehouse costs incur in order picking and rearrangement. Today there are theories and models on how inventory management around order picking and rearrangement can be optimized. However, bulk stocks are rarely addressed in research or literature. Thus, this work was aimed at examining the adaptive theory of customary methods in a business with bulk storage. The study has fulfilled its purpose through a case and literature study with both qualitative and quantitative approaches in the form of interviews and observations. Inventory design and inventory control can advantageously be seen as basic methods that require efficiency development in picking and rearranging in bulk storages. Methods such as MUDA and 5S create the conditions for identifying, maintaining and implementing efficiency improvements. The customary methods studied could, through observation and interview, be found to be implementable or non-implementable. In summary, an overall template of the methods could be compiled where they could jointly and separately contribute to efficiency improvements. The studied company could be provided with improvement proposals that are recommended to be introduced in both smaller stages and during larger, more extensive projects.