El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In general, lean strategies in the textile sector are applied in production to improve productivity, reduce production time, and reduce errors, among other aspects. However, there are also documented studies, which are not common in the literature that uses these strategies to improve storage operations. This study shows the implementation of the Lean 5S Hybrid tool in the warehouse of a textile company based in Lima. The objective of the implementation was to improve productivity in the warehouse, as there were high response times when searching for materials, which reduced production time, warehouse redistribution, better using available space, and being able to strategically locate main materials. The results revealed an increase in warehouse productivity 3.95 times the initial one, an Inventory Record Accuracy of 98.17%, a decrease in the requirement search time by 66.12% (from 25 to 8 min), and stock rotation of 6.22 times.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / One of the most important problems affecting companies that assemble and market vehicles is stock depletion of finished products. Therefore, many small and medium-sized enterprises (SMEs) have attempted to manage this situation by using tools such as the Q mode, which continuously reviews inventories but does not indicate when and in what quantity a company must supply its sales outlets but requires a more complex level of supplier development and supply chain management efficiency than SMEs can achieve. Likewise, with our proposal we achieved a 50% decrease in stock depletion, based on an analysis of model results, with a confidence level of 95% and a certainty level of 75.30%, projecting a profit of 59000 soles with a return cost of 1.41 and a recovery period of 2 years and 4 months, ensuring both the sustainability and profitability of the proposal.

A game theoretic approach is used to analyze an inventory problem with two products, random demand, and random supply. The supply chain analyzed includes two retailers that sell two substitutable products and two suppliers. Each retailer faces a stochastic demand for the product she sells and replenishes her inventory from her supplier. The supplier provides a random fraction of the quantity requested. A given percentage of customers with unmet demand will substitute the product sold by the other retailer. We assume that the two retailers who make ordering decisions are rational players. Since each retailer's decision affects the single period expected profit of the other retailer, game theory is used to find the order quantities when the retailers use a Nash strategy.

Estoques são comuns a qualquer empresa, visto que são necessários para amortecer impactos de demandas não programadas e evitar rupturas entre processos, adicionando segurança entre diferentes elos de uma cadeia. Problemas de gerenciamento de estoques são corriqueiros, dado que as suas causas podem ser múltiplas, estando presentes em diferentes nós de uma cadeia e sendo originados por questões vinculadas ao fornecimento, à demanda, à informação, além de outros fatores possíveis. Devido à importância dos estoques para uma empresa, seja financeira, como concentração de ativos, ou seja por mitigar riscos no processo de suprimento, problemas de gerenciamento de estoques são periodicamente tratados na literatura. Entretanto, não existe consenso sobre o que são os problemas de gerenciamento e um método difundido para sua identificação e análise. Esta pesquisa concentra-se nesta lacuna, propondo um método de identificação e análise dos problemas de gerenciamento de estoques. Este método está ancorado em seis distintas etapas que foram aplicadas, na forma de um estudo de caso, em uma empresa da serra gaúcha. As etapas compreendem a identificação dos causadores do problema de gerenciamento de estoques, a modelagem e simulação do ambiente proposto e análises das iterações sob a perspectiva de três variáveis chave: saldo de estoques, escassez e uma função custo. Entre os resultados desta pesquisa encontram-se uma classificação de causadores de problemas de gerenciamento de estoques e o método proposto. Foi possível observar no estudo de caso que, entre as variáveis de entrada utilizada, quando manipulada a média aritmética da distribuição destas variáveis estocásticas, elas causaram maior variação sistemática ao resultado do modelo quando comparada a variação sistemática causada pela alteração da variância da distribuição desta mesma variável estocástica. / Inventories are common to any businesses, as they are needed to cushion impacts from unscheduled demands and avoid ruptures between processes, adding security between different tiers in a supply chain. Inventory management problems are common, as their causes can be multiple, and being present on different nodes of a chain, which can be caused by issues related to supply, demand, information, and other possible factors. Due to the importance of inventories for a business, whether financial - as assets - or its role in mitigating risks in the supply process, inventory management problems are frequently approached in the literature. However, there is no consensus on what are inventory management problems and there is no widespread method for identification and analysis of inventory management problems. This research focus on this gap by proposing a method of identification and analysis of inventory management problems. This method is anchored in six distinct steps that have been applied in the form of a case study on a company in south of Brazil. The steps include the identification of the causes of the inventory management problem, the modeling and simulation of the proposed environment and analysis of iterations from the perspective of three key variables: inventory balance, inventory shortages and a cost function. Among the results of this research are a classification of inventory management problems originators and the proposed method. It was observed in the case study that among the input variables, when manipulated the arithmetic mean of the stochastic distribution of these variables, they increased the systematic variation output of the model more than when were manipulated the variance of the stochastic distribution of the same variable.

Inventory management is today seen as more competitive oriented, process oriented and better integrated into the companies than before. But still do several companies run their inventories according a traditional approach. There is therefore a need for some companies to evaluate their inventory management and adapt the new view. There is also a need to adjust for increased focus on sustainability, previous research calls for strategies and tools that include sustainable parameters without lowering the profitability. The purpose with this study is to assess inventory management principles and purchasing routines related to the acquisition of packaging material in a process industry. The study aims to develop a framework for decision makers in inventory management. This framework will be the basis for a support tool incorporating a relatively simple and easy-to-use user interface. This master thesis is performed as a case study research and uses several data collection methods, such as a literature review, observations, and interviews. The findings from the data collection is used to evaluate which impact inventory management has on a company’s profitability, and which basic parameters that could be included in the support tool. The empirical findings show that Barilla Sweden’s current inventory management match the traditional approach, but also that they strive to become more competitive and process oriented in their management of inventories. There is however some constraints in their working strategy that prevents them from taking the next step. Comparison between Barilla Sweden’s current order size and an economical order quantity (EOQ) and just-in-time (JIT) approach is made. The comparison shows that Barilla Sweden has money to save and warehouse space to release with changed order quantities. Adapting a new inventory management approach require review of uncertainties, such as delivery accuracy and forecast changes. It is also necessary to evaluate supplier relations and internal working strategies. The effect of these parameters on inventory management can be noticed in the support tool. The tool compares total costs, average stock, tied capital, and environmental and social consequences between the EOQ model and JIT. The support tool visualizes drawbacks and benefits with different order sizes and has an easy-to-use interface.

Estoques são comuns a qualquer empresa, visto que são necessários para amortecer impactos de demandas não programadas e evitar rupturas entre processos, adicionando segurança entre diferentes elos de uma cadeia. Problemas de gerenciamento de estoques são corriqueiros, dado que as suas causas podem ser múltiplas, estando presentes em diferentes nós de uma cadeia e sendo originados por questões vinculadas ao fornecimento, à demanda, à informação, além de outros fatores possíveis. Devido à importância dos estoques para uma empresa, seja financeira, como concentração de ativos, ou seja por mitigar riscos no processo de suprimento, problemas de gerenciamento de estoques são periodicamente tratados na literatura. Entretanto, não existe consenso sobre o que são os problemas de gerenciamento e um método difundido para sua identificação e análise. Esta pesquisa concentra-se nesta lacuna, propondo um método de identificação e análise dos problemas de gerenciamento de estoques. Este método está ancorado em seis distintas etapas que foram aplicadas, na forma de um estudo de caso, em uma empresa da serra gaúcha. As etapas compreendem a identificação dos causadores do problema de gerenciamento de estoques, a modelagem e simulação do ambiente proposto e análises das iterações sob a perspectiva de três variáveis chave: saldo de estoques, escassez e uma função custo. Entre os resultados desta pesquisa encontram-se uma classificação de causadores de problemas de gerenciamento de estoques e o método proposto. Foi possível observar no estudo de caso que, entre as variáveis de entrada utilizada, quando manipulada a média aritmética da distribuição destas variáveis estocásticas, elas causaram maior variação sistemática ao resultado do modelo quando comparada a variação sistemática causada pela alteração da variância da distribuição desta mesma variável estocástica. / Inventories are common to any businesses, as they are needed to cushion impacts from unscheduled demands and avoid ruptures between processes, adding security between different tiers in a supply chain. Inventory management problems are common, as their causes can be multiple, and being present on different nodes of a chain, which can be caused by issues related to supply, demand, information, and other possible factors. Due to the importance of inventories for a business, whether financial - as assets - or its role in mitigating risks in the supply process, inventory management problems are frequently approached in the literature. However, there is no consensus on what are inventory management problems and there is no widespread method for identification and analysis of inventory management problems. This research focus on this gap by proposing a method of identification and analysis of inventory management problems. This method is anchored in six distinct steps that have been applied in the form of a case study on a company in south of Brazil. The steps include the identification of the causes of the inventory management problem, the modeling and simulation of the proposed environment and analysis of iterations from the perspective of three key variables: inventory balance, inventory shortages and a cost function. Among the results of this research are a classification of inventory management problems originators and the proposed method. It was observed in the case study that among the input variables, when manipulated the arithmetic mean of the stochastic distribution of these variables, they increased the systematic variation output of the model more than when were manipulated the variance of the stochastic distribution of the same variable.

Estoques são comuns a qualquer empresa, visto que são necessários para amortecer impactos de demandas não programadas e evitar rupturas entre processos, adicionando segurança entre diferentes elos de uma cadeia. Problemas de gerenciamento de estoques são corriqueiros, dado que as suas causas podem ser múltiplas, estando presentes em diferentes nós de uma cadeia e sendo originados por questões vinculadas ao fornecimento, à demanda, à informação, além de outros fatores possíveis. Devido à importância dos estoques para uma empresa, seja financeira, como concentração de ativos, ou seja por mitigar riscos no processo de suprimento, problemas de gerenciamento de estoques são periodicamente tratados na literatura. Entretanto, não existe consenso sobre o que são os problemas de gerenciamento e um método difundido para sua identificação e análise. Esta pesquisa concentra-se nesta lacuna, propondo um método de identificação e análise dos problemas de gerenciamento de estoques. Este método está ancorado em seis distintas etapas que foram aplicadas, na forma de um estudo de caso, em uma empresa da serra gaúcha. As etapas compreendem a identificação dos causadores do problema de gerenciamento de estoques, a modelagem e simulação do ambiente proposto e análises das iterações sob a perspectiva de três variáveis chave: saldo de estoques, escassez e uma função custo. Entre os resultados desta pesquisa encontram-se uma classificação de causadores de problemas de gerenciamento de estoques e o método proposto. Foi possível observar no estudo de caso que, entre as variáveis de entrada utilizada, quando manipulada a média aritmética da distribuição destas variáveis estocásticas, elas causaram maior variação sistemática ao resultado do modelo quando comparada a variação sistemática causada pela alteração da variância da distribuição desta mesma variável estocástica. / Inventories are common to any businesses, as they are needed to cushion impacts from unscheduled demands and avoid ruptures between processes, adding security between different tiers in a supply chain. Inventory management problems are common, as their causes can be multiple, and being present on different nodes of a chain, which can be caused by issues related to supply, demand, information, and other possible factors. Due to the importance of inventories for a business, whether financial - as assets - or its role in mitigating risks in the supply process, inventory management problems are frequently approached in the literature. However, there is no consensus on what are inventory management problems and there is no widespread method for identification and analysis of inventory management problems. This research focus on this gap by proposing a method of identification and analysis of inventory management problems. This method is anchored in six distinct steps that have been applied in the form of a case study on a company in south of Brazil. The steps include the identification of the causes of the inventory management problem, the modeling and simulation of the proposed environment and analysis of iterations from the perspective of three key variables: inventory balance, inventory shortages and a cost function. Among the results of this research are a classification of inventory management problems originators and the proposed method. It was observed in the case study that among the input variables, when manipulated the arithmetic mean of the stochastic distribution of these variables, they increased the systematic variation output of the model more than when were manipulated the variance of the stochastic distribution of the same variable.

In this paper we first show that the gains achievable by integrating pricing and inventory control are usually small for classical demand functions. We then introduce reference price models and demonstrate that for this class of demand functions the benefits of integration with inventory control are substantially increased due to the price dynamics. We also provide some analytical results for this more complex model. We thus conclude that integrated pricing/inventory models could repeat the success of revenue management in practice if reference price effects are included in the demand model and the properties of this new model are better understood. (authors' abstract)

El presente proyecto de investigación tiene como finalidad el desarrollo de una propuesta basada en la mejora de la gestión de inventarios en una empresa de la industria de minería y construcción. Por ello se emplearán conceptos básicos de gestión de inventarios y pronósticos. Hoy en día, son muchas las empresas pertenecientes a diferentes industrias las cuales buscan conseguir mejorar en la administración de sus inventarios, entre ella se encuentran empresas mineras y de construcción. Las empresas tienen muy en claro que los inventarios son recursos financieros que en lugar de proporcionar algún beneficio se encuentran inmovilizados. Es por ello que gestionar de una mejor manera los inventarios es un tema de gran índole en la actualidad. La empresa en estudio se dedica a la venta de repuestos para maquinaria pesada dirigida hacia el sector de minería y construcción. A la vez, brinda servicios post venta de reparación y mantenimiento. Posee una gama de miles de productos enfocados en un máximo de 10 proveedores. Al encontrar problemas con el stock, se realizó el diagnóstico a la empresa encontrándose el problema de un nivel excesivamente elevado de inventarios. Para ello se propone mejoras en la gestión de inventarios comenzando con la técnica de priorización ABC para centrarse en aquellos productos que generan mayores ingresos. Luego se hará uso de pronósticos de demanda para determinar la cantidad que se va a ofertar para el siguiente periodo y por último se realiza el cálculo de la cantidad a pedir. Al finalizar la parte cuantitativa del proyecto se desarrolla y define los procesos que van a dar soporte a la gestión de inventarios. Además, también se determinó los costos asociados que se incurrirían al desarrollar el proyecto y su análisis de costo beneficio. Finalmente se presenta las conclusiones y recomendaciones que la empresa debe de tener en cuenta en caso de colocar en práctica el proyecto. / The purpose of this research project is to develop a proposal based on the improvement of inventory management in a company in the mining and construction industry. Therefore, basic concepts of inventory management and forecasts will be used. Today, there are many companies belonging to different industries which seek to improve the management of their inventories, including mining and construction companies. The companies are very clear that inventories are financial resources that instead of providing some benefit are immobilized. That is why managing inventories in a better way is a very important issue at present. The company under study is dedicated to the sale of spare parts for heavy machinery directed towards the mining and construction sector. At the same time, it provides post-sale repair and maintenance services. It has a range of thousands of products focused on a maximum of 10 suppliers. When finding problems with the stock, the diagnosis was made to the company finding the problem of an excessively high level of inventories. To do this, we propose improvements in the management of inventories starting with the ABC prioritization technique to focus on those products that generate the highest income. Then demand forecasts will be used to determine the amount that will be offered for the next period and finally the calculation of the amount to be ordered is made. At the end of the quantitative part of the project, the processes that will support the inventory management are developed and defined. In addition, the associated costs that would be incurred when developing the project and its cost-benefit analysis were also determined. Finally, the conclusions and recommendations that the company should take into account in case of putting the project into practice are presented. / Tesis

Any decentralized retail or wholesale system of competing entities requires a benefit sharing arrangement when competing entities collaborate after their demands are realized. For instance, consider a distribution system similar to the observed behavior of independent car dealerships. If a dealership does not have in stock the car requested by a customer, it might consider acquiring it from a competing dealer. Such behavior raises questions about competitive procurement strategies that achieve system optimal outcomes. This dissertation consists of three main bodies of work contained respectively in chapters 2, 3, and 4. In the first work -- chapter 2, we examine a decentralized system that adopts an ex-post agreed transfer payment approach proposed by Anupindi et al. (Manuf. Serv. Oper.Manag. 4(3):349-368, 2001). In particular, we state a set of conditions on cost parameters and distributions that guarantee uniqueness of pure strategy Nash equilibrium. In the second work -- chapter 3, we introduce a multilevel graph framework that links decentralized inventory distribution models as a network of stochastic programming with recourse problems. This framework depicts independent retailers who maximize their individual expected profits, with each retailer independently procuring inventory in the ex-ante stage in response to forecasted demand and anticipated cooperative recourse action of all retailers in the system. The graph framework clarifies the modeling connection between problems in a taxonomy of decentralized inventory distribution models. This unifying perspective links the past work and shades light on future research directions. In the last work -- chapter 4, we examine and recast the biform games modeling framework as two-stage stochastic programming with recourse. Biform games modeling framework addresses two-stage games with competitive first stage and cooperative second stage without ex-ante agreement on profit sharing scheme. The two-stage stochastic programming view of biform games is demonstrated on examples from all the known examples regarding operational decision problems of competing firms from the literature. It allows an “old” mathematical methodology to showcase its versatility in modeling combined competitive and cooperative game options. In short, this dissertation provides important insights, clarifications, and strategic limitations regarding collaborations in decentralized distribution system.