Ethylene-vinyl acetate emulsion is the copolymer of vinyl acetate and ethylene, which has been developed as a powerful adhesive base. It effectively bonds substrates such as wood, cotton cloth, hardboard and paperboard. After modifying by adhesives producers, EVA emulsion can bond a great variety of surfaces, particularly effective in bonding polyvinyl chloride films and narrow-pore materials. Adhesives producers provides customized products according to different end users¡¦ needs and consequently have to keep raw materials in stock until orders are placed. The ordering of EVA emulsion is an important issue for adhesives producers because of the seasonal demand pattern and price fluctuation of raw materials. Furthermore, under certain transporting and order restrictions, the ordering quantity is fixed and delivery time has to be made in advance. The multi-period inventory models, including EOQ and ROP, are not suitable for analyzing the ordering of EVA emulsion due to the presupposition of unlimited period. This research is based on the case study for NP chemical, using modified ROP model to explore how the selection of service level and delivery time can effect safety stock, probability of shortage, and inventory cost under the conditions of limited period, seasonal demand, given order quantity, and pre-selecting delivery points. The study also constructs a liquid raw material inventory model with fluctuating price and given order quantity in order to determine the optimal combination of delivery points. The conclusion of this study are presented as follows: 1.Service level doesn¡¦t directly effects the probability of shortage and inventory cost in limited period. 2.The combination of delivery points is the key decision factor because of its causal relationship with the probability of shortage and inventory cost. 3.The optimal combination which leads to the lowest inventory cost can be determined by using the inventory model introduced in this study.

We consider the optimization problem of safety stock placement in a supply chain, as formulated in [1]. We prove that this problem is NP-Hard for supply chains modeled as general acyclic networks. Thus, we do not expect to find a polynomial-time algorithm for safety stock placement for a general-network supply chain. / Singapore-MIT Alliance (SMA)

In the paper, we minimize the holding cost of the safety stock held in a supply chain modeled as a general network. By our assumption, the demand is bounded by a concave function. This fact allows us to formulate the problem as a deterministic optimization. We minimize a concave function over a discrete polyhedron. The main goal of the paper is to describe an algorithm to solve the problem without assuming any particular structure of the underlying supply chain. The algorithm is a branch and bound algorithm. / Singapore-MIT Alliance (SMA)

In this thesis, we focus on integration issue of manufacturing and sales functions from the perspective of aggregate production planning. The manufacturing function and sales function are performed by separate affiliated companies of the same business group, which operate as an integrated supplier-buyer system. In particular, this study provides theoretical and practical insight into the use of forecast volatility measure to better match supply with demand so as to reduce the costs of inventory and stock-outs in the manufacturer-buyer relationship under described master production-scheduling environment. Nature of forecast modifications provided by the buyer lays the foundation for the study. We modify the existing aggregate production planning model to accommodate a measure of historical forecast evolution. The overall objective of the thesis is to provide management with aforecast evolution-modeling framework to examine performance characteristics of the manufacturer-buyer interaction.

[pt] Nesta dissertação são apresentados dois modelos de estoque aplicados ao sistema de controle de estoques (Q, R), que envolve a definição do tamanho de lote a ser encomendado a cada vez e a ocasião de encomendar. Esses modelos têm como objetivo a minimização do custo total anual formado pelo custo de encomendar, de manter e de falta de estoque. Os modelos são testados na sua forma completa e com aproximações sugeridas por diversos autores e, em seguida, os resultados são comparados. Além disso, é desenvolvida uma formulação que busca simplificar a identificação dos casos reais que podem utilizar as aproximações sugeridas para estes modelos. Um dos modelos é utilizado para definir níveis ótimos de estoque de derivados de petróleo em uma refinaria da Petrobras e os resultados são comparados com níveis de estoque praticados hoje pela empresa. / [en] This dissertation presents two inventory models applied to the continuous review, order-point, order-quantity (Q, R), that define a fixed quantity to be ordered and the occasion to order. The objective is to minimize the total annual cost comprised by setup, backorder/stockout and holding costs. First, these models are tested with their complete formulation and compared with approximations proposed by many authors. Second, it is developed a formulation to facilitate the identification of real cases where approximation is recommended. Finally one of these models is applied to define optimum inventory levels of oil products in a Petrobras` refinery and results are compared with the level of inventory the company now holds.

A high level of delivery precision from a focal firm to their customers has the potential to provide competitive advantage amongst competing businesses. This report will detail the subject of inventory management and utilize theories on the subject in order to provide recommendations to a multinational company that wishes to increase their delivery precision. The results of the work conducted are presented and recommendations given in the form of firstly analyzing inventory and segregating the product range where applicable. This should be treated as the first priority to gain an insight into where potential problem areas lie and to determine the products that are the biggest contributors to the overall value of goods sold. As a secondary measure, managing supplier relations carefully and the strategic sourcing of materials are strategies that will help to effectively reduce problems through increased visibility of information in communication channels. An accurate demand forecasting model will predict demand ahead of time, ensuring that the correct products are being held as inventory for no longer than is strictly needed, with a safety stock system being used as a safety net for those products that are suitable. A theoretical implementation of exponential II smoothing based forecasting coupled with standard deviation based safety stock calculations, yields results that effectively raises delivery precision. By forecasting demand for individual months and using calculated safety stock levels, the model is able to adjust for the shortfall between forecasted demand and actual demand.

Existing multi-echelon inventory optimization models and formulas were studied to get an understanding of how safety stock levels are determined. Because of the restrictive distribution assumptions of the existing safety stock formula, which are not necessarily realistic in practice, a method to analyze the performance of this formula in a more realistic setting was desired. A SimPy simulation model was designed and implemented for a simple two-stage supply chain as a way to test the performance of the safety stock formula. This implementation produced results which led to the conclusion that the safety stock formula tends to underestimate the level of safety stock needed to provide a certain service level when predicted standard deviation of demand is underestimated and the assumptions of normally distributed demand and normally distributed lead times are not fulfilled.

[pt] Esta dissertação aborda a evolução da malha ferroviária brasileira e o impacto deste modal de transporte nos estoques de Diesel e Gasolina das Bases de Distribuição localizadas no Sul do Brasil, pertencentes a uma importante distribuidora de derivados de petróleo. A relevância do estudo realizado deve-se à aprovação da Lei 9.478 - Lei do Petróleo - que quebrou o monopólio da Petrobras neste setor, transferindo para as distribuidoras o gerenciamento espacial e volumétrico de seus estoques. Por outro lado, o estudo contribui para o conhecimento da incipiente malha ferroviária brasileira, a partir da privatização ocorrida em 1996, e tornada importante diante da crescente necessidade de se agregar valor, eficiência e segurança ao transporte de combustíveis. O objetivo deste estudo é abordar a evolução da malha ferroviária brasileira e o impacto deste modal de transporte nos estoques de segurança de Diesel e Gasolina de uma grande Distribuidora de derivados de petróleo e o relacionamento dos custos de transporte atrelados aos riscos e impontualidade ainda prevalecentes no sistema ferroviário. / [en] This thesis approaches the evolution of the Brazilian railroad mesh and the impact of this modal of transportation to an important company in the supplies of Diesel and Gasoline to the Bases of Distribution located in the South of Brazil. The relevance of this study is justified due to the approval of Law 9.478 - Law of the Oil - that broke the monopoly of Petrobras in this sector, transferring to oil companies the spatial and volumetric management of their oil inventories. On the other hand, the study contributes for the knowledge of the incipient Brazilian railroad mesh, privatized in 1996, and becoming increasingly important giving the necessity of adding value, efficiency and security to the fuel transportation. The objective of the present study is the evolution of railroad mesh and the impact of this transportation modal on Gasoline and Diesel safety stocks handled by an important oil company and its relationship to the costs of transportation related to the risks and unpunctuality still prevailing in the railroad system.

<p>GNT Group is a Nordic/Baltic wholesaler that distributes products in the IT, entertainment and home electronics sector. GNT is facing problems with inaccurate inventory levels which can lead to unnecessarily high inventory carrying costs or lost sales. Currently the decisions about when and how many to order are made somewhat arbitrarily by the responsible personnel. Their decisions are based only on some brief sales history and on experience. </p><p>GNT wants to develop its ERP system to be able to support the purchaser in these and other related decisions. The purpose of this thesis is to give suggestions to what decisions the ERP system should support and how these decisions can be made. </p><p>The three main tasks in this thesis are to suggest how to calculate the optimal order quantity, how to calculate the optimal ordering point and how to decide whether it can be profitable to store an article in only one of GNT’s warehouses. </p><p>The suggested solution is based on a volume value/demand frequency classification which also takes an item’s life cycle characteristics into consideration. For the different classes suitable calculations and decisions are suggested concerning the three main tasks and issues related to them.</p>

In this paper, we study the stochastic transportation-inventory network design problem involving one supplier and multiple retailers. Each retailer faces some uncertain demand. Due to this uncertainty, some amount of safety stock must be maintained to achieve suitable service levels. However, risk-pooling benefits may be achieved by allowing some retailers to serve as distribution centers (and therefore inventory storage locations) for other retailers. The problem is to determine which retailers should serve as distribution centers and how to allocate the other retailers to the distribution centers. Shen et al. (2000) and Daskin et al. (2001) formulated this problem as a set-covering integer-programming model. The pricing subproblem that arises from the column generation algorithm gives rise to a new class of submodular function minimization problem. They only provided efficient algorithms for two special cases, and assort to ellipsoid method to solve the general pricing problem, which run in O(n⁷ log(n)) time, where n is the number of retailers. In this paper, we show that by exploiting the special structures of the pricing problem, we can solve it in O(n² log n) time. Our approach implicitly utilizes the fact that the set of all lines in 2-D plane has low VC-dimension. Computational results show that moderate size transportation-inventory network design problem can be solved efficiently via this approach. / Singapore-MIT Alliance (SMA)