The concept of inventory control has been around since the early 20th century and it’s constantly evolving. The importance of inventory management and supply chain management is clear, and companies are constantly trying to evolve their systems and ways of handling inventory control. By having a proper inventory control system with adequate inventory record audits, a company could potentially have several benefits such as reduced tied-up capital, reduced holding costs, reduced/redistributed work hours, better automation and more. Most organisations and companies have some form of inventory control, however not all have full control of their inventory. This includes automatic inventory balance updates, package traceability, automatic replenishment systems and more. To implement these ideas, a company would need to foremost find what factors are currently hindering them from obtaining this and consequently being able to adjust their factors. Since there are several ways to obtain an automatic inventory record update that is adequate, multiple proposals are discussed in this thesis project. This thesis project assessed what the necessary steps that a company needs to perform are through a case study at Scania CV Engine and a benchmarking at Scania Production Angers. Through a collection of scientific literature and empirical data, an attempt to identify the factors that determine whether a company can implement full inventory control or not was made. As a supplement to this, this thesis project also looked over what type of consequences an implementation of full inventory control could have in a company, both when it comes to purely systemic consequences as well as economic consequences. / Begreppet saldokontroll har cirkulerat sedan början av 1900-talet och teorierna utvecklas ständigt. Betydelsen av lagerstyrning och Supply Chain Management är idag tydlig och företag försöker ständigt utveckla sina system och sätt att hantera saldokontroll på. Genom att ha ordentlig saldokontroll med adekvata lagerregistreringsrevisioner kan ett företag potentiellt få flertalet fördelar som till exempel reducerat bundet kapital, minskade innehavskostnader, reducerade eller omfördelade arbetstimmar, bättre automatisering och mera. De flesta organisationer och företag har någon form av lagerkontroll, men inte alla har 100% kontroll över sina inventeringar. Detta inkluderar automatiska lagerrevisioner, spårbarhet av paket, automatiska påfyllningssystem och mer. För att genomföra dessa idéer måste ett företag framför allt finna vilka faktorer som för närvarande förhindrar dem från att uppnå 100% saldokontroll och följaktligen kunna justera dessa faktorer. Eftersom det finns flera sätt att uppnå automatiska revisioner av inventeringen som är proper så diskuteras flera förslag i denna avhandling. Denna avhandling försöker bedöma vilka nödvändiga steg som ett företag behöver genomföra är genom en utförd fallstudie på Scania CV Engine tillsammans med en benchmarking på Scania Production Angers. Genom en samling av vetenskapliga studier och empiriska data från fallstudien gjordes ett försök att identifiera de faktorer som avgöra om ett företag kan implementera 100% saldokontroll eller inte. Som ett komplement till detta ser denna rapport även över vilken typ av konsekvenser en sådan implementering kan innebära, båda när det gäller rent systematiska förändringar samt ekonomiska förändringar.

This dissertation focuses on topics related to the value of real-time information and/or to supply uncertainties due to uncertain lead-times and yields in supply chains. The first two of these topics address issues associated with freight transportation, while the remaining two topics are concerned with inventory replenishment. We first assess the value of dynamic tour determination for the traveling salesman problem (TSP). Given a network with traffic dynamics that can be modeled as a Markov chain, we present a policy determination procedure that optimally builds a tour dynamically. We then explore the potential for expected total travel cost reduction due to dynamic tour determination, relative to two a priori tour determination procedures. Second, we consider the situation where the decision to continue or abort transporting perishable freight from an origin to a destination can be made at intermediate locations, based on real-time freight status monitoring. We model the problem as a partially observed Markov decision process (POMDP) and develop an efficient procedure for determining an optimal policy. We determine structural characteristics of an optimal policy and upper and lower bounds on the optimal reward function. Third, we analyze a periodic review inventory control problem with lost sales and random yields and present conditions that guarantee the existence of an optimal policy having a so-called staircase structure. We make use of this structure to accelerate both value iteration and policy evaluation. Lastly, we examine a model of inventory replenishment where both lead time and supply qualities are uncertain. We model this problem as an MDP and show that the weighted sum of inventory in transit and inventory at the destination is a sufficient statistic, assuming that random shrinkage can occur from the origin to the supply system or destination, shrinkage is deterministic within the supply system and from the supply system to the destination, and no shrinkage occurs once goods reach the destination.

Revenue Management (RM) has become one of the most successful application areas of Operation Research. What started off as an obscure practice among few airlines in U.S in early seventies, has attained the status of mainstream business practice, thanks to the major success enjoyed by companies applying RM. Over the same period, academic and industrial research on the methodology of RM has also grown rapidly. Despite the vast technical literature on the subject of revenue management, relatively few papers explicitly model the customer’s choice behavior. Such a behavior of customers could have major impact on revenue realized by an organization. Motivated by this, we focus on addressing the problem faced by a seller who serves customers exhibiting buy-down behavior. We address two important problems faced by a seller with few perishable goods. His objective is to obtain maximum revenue possible by sales of his perishable goods. The seller now potentially faces the problem of fixing the price of the products and then control the availability of products so as to maximize his revenue by minimizing the number of customers who buy-down. The first problem is the multi-product pricing problem where we consider a monop- olistic market situation in which a seller has some quantities of perishable goods under his disposal. The seller has the option of adding few additional features to the base product(perishable good) and thereby differentiating the products to cater to different market segments. Adding each additional feature involves certain cost and there are no restrictions on the availability of the features except that a feature can be added to the base product atmost once . The customers are price-sensitive and the seller is aware of the price-demand relationship of the various customer segments. A customer looking for a product buys the product if and only if the price is less than his reservation price. The sellers’ problem is to identify the price and bundling of features for the various customer segments so as to generate maximum possible revenue. We develop a Mixed integer non-linear mathematical programming model for the problem. We then split the problem into pricing problem and bundling problem and solve them sequentially. We finally provide a numeric example to illustrate the solution procedure. Once the prices are fixed, the next problem is to control the availability of products so as to prevent the buy-down behavior of the customers. We deal with the situation of a seller with two substitutable products. The price of both products are fixed over entire selling period. In a traditional control mechanism structure if the sequence of arrival of customers are known, then it becomes trivial to solve the problem of setting control limits which would prevent buy-down behavior. But in reality it never happens that the seller knows the arrival sequence. Hence in this study to isolate the effect of arrival sequence from other complexities like demand variability, we assume a deterministic demand for both the products but the arrival sequence is randomized. We initially analyze the above described problem and develop a static control mech- anism. We show that the static control mechanism is asymptotically equivalent to the traditional selling mechanism. Then we move on to make modification in the static con- trol mechanism and make it a dynamic control mechanism such that it will respond to the buy-down customers. In order to analyze the performance of dynamic control mechanism, we build a simulation model that would compare traditional selling mechanism and dynamic control mechanism. Statistical analysis is then done on the simulation results. It is shown that for all values of buy-down proportion, on an average the dynamic control mechanism outperforms the traditional control mechanism. Further there is a trend in revenues generated depending upon the buy-down proportion which is also explained. The chapter concludes with operating guidelines for better revenue realization. The organization of the thesis is as follows. In chapter 2, we present the literature survey. We start off with the history of RM and proceed to discuss the inventory control problems in RM in detail. Then we discuss literatures dealing with customer choice behavior. In chapter 3, we define and model the multi - product pricing problem. We present a mixed integer non-linear mathematical program to model the pricing problem. The solution to this problem is divided into two sub problems - the pricing problem and the bundling problem. Solution methodologies for both sub - problem are given and the chapter concludes with a numerical illustration for a 3 - product pricing problem. In chapter 4, we define and address the inventory control problem for a two product case when customers exhibit buy-down nature. We develop a static control mechanism and study its properties. Then we move on to the dynamic control mechanism which would suit real - world conditions. Finally we study the quality of developed methodology using statistical testing methods.

Thesis (doctoral)--Universität, Magdeburg. / Includes bibliographical references.

The implicit assumption in conventional inventory models is that the stored products maintain the same utility forever, i.e., they can be stored for an infinite period of time without losing their value or characteristics. However, generally speaking, almost all products experience some sort of deterioration over time. Some products have very small deterioration rates, and henceforth the effect of such deterioration can be neglected. Some products may be subject to significant rates of deterioration. Fruits, vegetables, drugs, alcohol and radioactive materials are examples that can experience significant deterioration during storage. Therefore the effect of deterioration must be explicitly taken into account in developing inventory models for such products. In most existing deteriorating inventory models, time is treated as a continuous variable, which is not exactly the case in practice. In real-life problems time factor is always measured on a discrete scale only, i.e. in terms of complete units of days, weeks, etc. In this research, we present several discrete-in-time inventory models and identify optimal ordering policies for a single deteriorating product by minimizing the expected overall costs over the planning horizon. The various conditions have been considered, e.g. periodic review, time-varying deterioration rate, waiting-time-dependent partial backlogging, time-dependent demand, stochastic demand etc. The objective of our research is two-fold: (a) To obtain optimal order quantity and useful insights for the inventory control of a single deteriorating product over a discrete time horizon with deterministic demand, variable deterioration rates and waiting-time-dependent partial backlogging ratios; (b) To identify optimal ordering policy for a single deteriorating product over a finite horizon with stochastic demand and partial backlogging. The explicit ordering policy will be developed for some special cases. Through computational experiments and sensitivity analysis, a thorough and insightful understanding of deteriorating inventory management will be achieved.

This dissertation consists of two self-contained studies. The first study, in the domain of stochastic inventory theory, addresses the structure of optimal ordering policies in a periodic review setting. We take multiple sources of a single product to imply an ordering cost function that is nondecreasing, piecewise linear, and convex. Our main contribution is a proof of the optimality of a finite generalized base stock policy under an average cost criterion. Our inventory model is formulated as a Markov decision process with complete observations. Orders are delivered immediately. Excess demand is fully backlogged, and the function describing holding and backlogging costs is convex. All parameters are stationary, and the random demands are independent and identically distributed across periods. The (known) distribution function is subject to mild assumptions along with the holding and backlogging cost function. Our proof uses a vanishing discount approach. We extend our results from a continuous environment to the case where demands and order quantities are integral. The second study is in the area of capacity planning. Our overarching contribution is a relatively simple and fast solution approach for the fleet composition problem faced by a retail distribution firm, focusing on the context of a major beverage distributor. Vehicles to be included in the fleet may be of multiple sizes; we assume that spot transportation capacity will be available to supplement the fleet as needed. We aim to balance the fixed costs of the fleet against exposure to high variable costs due to reliance on spot capacity. We propose a two-stage stochastic linear programming model with fixed recourse. The demand on a particular day in the planning horizon is described by the total quantity to be delivered and the total number of customers to visit. Thus, daily demand throughout the entire planning period is captured by a bivariate probability distribution. We present an algorithm that efficiently generates a "definitive" collection of bases of the recourse program, facilitating rapid computation of the expected cost of a prospective fleet and its gradient. The equivalent convex program may then be solved by a standard gradient projection algorithm.

Univ., Fak. für Wirtschaftswiss., Diss.--Magdeburg, 1999. / Literaturangaben.

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T13:37:34Z No. of bitstreams: 1 COTOMACIO_Andre_2017.pdf: 38758195 bytes, checksum: aab77ac02b3eb518fa373423e880c0f0 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T13:37:42Z (GMT) No. of bitstreams: 1 COTOMACIO_Andre_2017.pdf: 38758195 bytes, checksum: aab77ac02b3eb518fa373423e880c0f0 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T13:37:47Z (GMT) No. of bitstreams: 1 COTOMACIO_Andre_2017.pdf: 38758195 bytes, checksum: aab77ac02b3eb518fa373423e880c0f0 (MD5) / Made available in DSpace on 2017-08-16T13:37:52Z (GMT). No. of bitstreams: 1 COTOMACIO_Andre_2017.pdf: 38758195 bytes, checksum: aab77ac02b3eb518fa373423e880c0f0 (MD5) Previous issue date: 2017-03-24 / Não recebi financiamento / There are many studies in the literature that have shown the relationship between stock levels and financial performance, through profitability indicators, mostly to US manufacturing firms. However, the influence of the stock and its discrete components (raw material, inventory, production and finished product) in shareholder wealth has not been determined, particularly in the case of companies in Brazilian industrial sector. The present study aims to assess how the maintenance of inventory levels may affect profitability, returns and share performance in order to maximize shareholder wealth. For this purpose, panel data regressions were applied for fixed and random effects, based on financial data from companies which represents Brazilian manufacturing sector, listed in the BM&FBOVESPA Industrials Index (INDX). From the concept that a correct inventory and working capital management are directly linked to a better financial performance, the results show that this hypothesis confirmation or refutation vary according to the financial and inventory management metrics used, respectively, as dependent or independent variables. Another conclusion is that shareholder value creation has greater influence or is better able to isolate the effect of a correct inventory management, when compared to profitability and return metrics, only if linked to raw material or finished products indicators. Although the divergences regarding the influence of inventory and working capital management on financial performance still persist, this is one of the first studies that discuss this issue for Brazilian companies, and more specifically, for manufacturing sector, which represent an important stock portfolio index in the country. / Muitos são os trabalhos na literatura que mostraram a relação entre os níveis de estoque e o desempenho financeiro, por meio de indicadores de lucratividade, em sua grande maioria para empresas de manufatura dos EUA. Entretanto, a influência do estoque e de seus componentes discretos (matéria prima, estoque em produção e produto acabado) na riqueza do acionista ainda não foi determinada, principalmente em se tratando de empresas do setor industrial brasileiro. O presente estudo avaliou como a manutenção dos níveis de estoque podem afetar a lucratividade, rentabilidade e o desempenho das ações na maximização da riqueza do acionista. Para tanto, foram feitas regressões de dados em painel, testando-se para efeitos fixos e aleatórios, a partir de dados financeiros de empresas que representam o setor de manufatura brasileiro, listadas no Índice do Setor Industrial (INDX) da BM&FBOVESPA. Partindo da premissa de que uma correta gestão do estoque e do capital de giro estará diretamente ligada a um melhor desempenho financeiro, as conclusões apontam que a confirmação ou refutação dessa hipótese variam conforme a métrica financeira e de gestão de estoque utilizadas, respectivamente, como variáveis dependentes e independentes. Outra conclusão observada é que a criação de valor ao acionista sofre maior influência ou é capaz de isolar melhor o efeito de uma correta gestão de estoques, se comparada a métricas de lucratividade e de rentabilidade, somente quando atrelada aos indicadores de estoques de matéria prima e de produtos acabados. Apesar de as divergências quanto à relação da influência do desempenho do estoque e do capital de giro no desempenho financeiro ainda persistirem, este é um dos primeiros trabalhos a trazer esta discussão para análises em empresas brasileiras e, mais especificamente, para empresas do setor de manufatura, que representam um importante índice de carteira de ações no país.

Nous considérons des problèmes de gestion des stocks multi-échelon à temps périodique avec des demandes non stationnaires. Ces hypothèses sur la demande apparaissent notamment lorsque des prévisions sur la demande sont utilisées dynamiquement (de nouvelles prévisions sont fournies à chaque période). La structure des coûts comprend des coûts fixes et variables d’approvisionnement, des coûts de stockage et des coûts de mise en attente des demandes. Le délai d’approvisionnement est supposé constant. Le problème consistant à déterminer la politique optimale qui minimise les coûts sur un horizon fini peut être formulé grâce à un programme dynamique. Dans le cadre déterministe, les problèmes auxquels nous nous intéressons sont le plus souvent NP-difficiles, ce qui fait rapidement exploser l’espace d’état. Il devient alors nécessaire de recourir à des heuristiques. Nous nous orientons vers la recherche d'algorithmes d'approximation combinatoires pour le problème One Warehouse Multi Retailers et plus généralement pour des systèmes de distribution divergents. Nous nous intéresserons dans un premier temps à des systèmes de distribution à deux étages avec un entrepôt central et des entrepôts secondaires qui voient la demande finale. Dans un deuxième temps, des structures logistiques plus complexes pourront être considérées. L’objectif sera de proposer des heuristiques originales, basées sur des techniques de répartition des coûts, de les comparer numériquement à la politique optimale sur de petites instances et, si possible, d’établir des garanties de performance. / Inventory management has always been a major component of the field of operations research and numerous models derived from the industry aroused the interest of both the researchers and the practitioners. Within this framework, our work focuses on several classical inventory problems, for which no tractable method is known to compute an optimal solution. Specifically, we study deterministic models, in which the demands of the customers are known in advance, and we propose approximation techniques for each of the corresponding problems that build feasible approximate solutions while remaining computationally tractable. We first consider continuous-time models with a single facility when demand and holding costs are time-dependent. We present a simple technique that balances the different costs incurred by the system and we use this concept to build approximation methods for a large class of such problems. The second part of our work focuses on a discrete time model, in which a central warehouse supplies several retailers facing the final customers demands. This problem is known to be NP-hard, thus finding an optimal solution in polynomial time is unrealistic unless P=NP. We introduce a new decomposition of the system into simple subproblems and a method to recombine the solutions to these subproblems into a feasible solution to the original problem. The resulting algorithm has a constant performance guarantee and can be extended to several generalizations of the system, including more general cost structures and problems with backlogging or lost-sales.

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2016-10-14T14:09:45Z No. of bitstreams: 1 PERRESSIM_William_2016.pdf: 51818946 bytes, checksum: cfcb0792fcd322943e503d5c66ef56d0 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2016-10-14T14:12:17Z (GMT) No. of bitstreams: 1 PERRESSIM_William_2016.pdf: 51818946 bytes, checksum: cfcb0792fcd322943e503d5c66ef56d0 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2016-10-14T14:12:33Z (GMT) No. of bitstreams: 1 PERRESSIM_William_2016.pdf: 51818946 bytes, checksum: cfcb0792fcd322943e503d5c66ef56d0 (MD5) / Made available in DSpace on 2016-10-14T14:12:49Z (GMT). No. of bitstreams: 1 PERRESSIM_William_2016.pdf: 51818946 bytes, checksum: cfcb0792fcd322943e503d5c66ef56d0 (MD5) Previous issue date: 2016-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The efficiency of a production system is characterized by its ability to produce more with fewer resources. In this sense new strategies for inventory management emerge, to minimize the impact of this factor in the results of the organizations. Literature in operations management deals with a long time to study and analyze the relationship between the stock of the economic and financial performance. But even in the face of decades of research, some issues show up unanswered. In this sense this work is to analyze the influence of the stock's performance on the economic and financial results, making use of indicators based on Gross Profit, Operating Income and Net Income, analyzing the relationship between the composition of these indicators and their effectiveness in isolating the effect of stock on economic and financial performance. For such a set of 56 industries with publicly traded and listed on the BM&FBovespa, were analyzed their data financial performance and operational arranged in the form of panel, with the start in the 1st quarter of 2004 and finish in the 4th quarter 2014 total so 11 years and 2376 observations. Regression analysis with panel data using the model of generalized least squares indicated that the economic and financial performance is positively impacted by stock, that is, reductions in inventory levels should impact in better profits for the organization. also indicated the ROABruto (Gross Profit) and BEP (Operating Income) show to be more influenced by the stock compared to indicators based on net income. / A eficiência de um sistema de produção é caracterizada por sua capacidade de produzir mais com menos recursos. Neste sentido, novas estratégias para a gestão de estoque emergem, visando minimizar o impacto deste fator nos resultados das organizações. A literatura em gestão de operações ocupa-se a muito tempo em estudar e analisar a relação entre o estoque o desempenho financeiro. Mas mesmo diante de décadas de pesquisa, algumas questões mostramse não respondidas. Neste sentido, este trabalho tem como objetivo analisar a influência do desempenho do estoque sobre o resultado financeiro, fazendo uso de indicadores baseados em Lucro Bruto, Lucro Operacional e Lucro Líquido, analisando a relação entre a composição destes indicadores e sua eficiência em isolar o efeito do estoque sobre o desempenho financeiro. Para tal, um conjunto com 56 empresas industriais com ações negociadas na BM&FBovespa foram analisadas, com seus dados de desempenho financeiro e operacionais dispostos na forma de painel, com o início no 1º trimestre de 2004 e término no 4º trimestre de 2014, totalizando, assim 11 anos e 2376 observações. A análise de regressão com dados em painel, utilizando o modelo dos mínimos quadrados generalizados, indicou que o desempenho financeiro é positivamente influenciado pelo estoque, ou seja, reduções nos níveis de estoque devem impactar em melhores lucros para a organização. Indicou também que o estoque influencia em maior intensidade o ROABruto (Lucro Bruto/Ativo) e o BEP (Lucro Operacional/Ativo), em comparação a indicadores baseados em lucro líquido.