An integrated simulation, learning, and game-theoretic framework is proposed to address the dynamics of supply chain competition. The proposed framework is composed of 1) simulation-based game platform, 2) game solving and analysis module, and 3) multi-agent reinforcement learning module. The simulation-based game platform supports multi-paradigm modeling, such as agent-based modeling, discrete-event simulation, and system dynamics modeling. The game solving and analysis module is designed to include various parts including strategy refinement, data sampling, game solving, equilibrium conditions, solution evaluation, as well as comparative statistics under varying parameter values. The learning module facilitates the decision making of each supply chain competitor under the stochastic and uncertain environments considering different learning strategies. The proposed integrated framework is illustrated for a supply chain system under the newsvendor problem setting in several phases. At phase 1, an extended newsvendor competition considering both the product sale price and service level under an uncertain demand is studied. Assuming that each retailer has the full knowledge of the other retailer's decision space and profit function, we derived the existence and uniqueness conditions of a pure strategy Nash equilibrium with respect to the price and service dominance under additive and multiplicative demand forms. Furthermore, we compared the bounds and obtained various managerial insights. At phase 2, to extend the number of decision variables and enrich the payoff function of the problem considered at phase 1, a hybrid simulation-based framework involving systems dynamics and agent-based modeling is presented, followed by a novel game solving procedure, where the procedural components include strategy refinement, data sampling, gaming solving, and performance evaluation. Various numerical analyses based on the proposed procedure are presented, such as equilibrium accuracy, quality, and asymptotic/marginal stability. At phase 3, multi-agent reinforcement learning technique is employed for the competition scenarios under a partial/incomplete information setting, where each retailer can only observe the opponent' behaviors and adapt to them. Under such a setting, we studied different learning policies and learning rates with different decay patterns between the two competitors. Furthermore, the convergence issues are discussed as well. Finally, the best learning strategies under different problem scenarios are devised.

Today, the competition between companies are very strong and fighted. In particular, small-medium size companies (SMEs) need to upgrade continuously in order to be in line with new technologies and new strategies that tends to develop companies in terms of productivity and quality. SMEs need, indeed, to be always competitive in a changeable market and to achieve competitive advantage through implementation of new technologies and theoretical methods or techniques. The implementation of those methods leads the company to increase its level of productivity and quality in order to achieve a competitive place within the market. The Gunasekaran framework is a tool which is useful in order to achieve a higher level of productivity and quality within a SME. This framework was studied and analyzed in order to be applied in a real life situation. This research focuses on the application of the same framework in a Mexican small company with the aim to develop and increase the level of productivity and quality of one department. Within the application of this framework, were applied the main concepts explained by the same Gunasekaran and they were analyzed in order to understand if a possible application could be useful to achieve success within the department.

No description available.

No abstract available. / Thesis (Ph.D.)-University of Durban-Westville, 1991.

Purpose: The aim of the study is to investigate how the material flow, of a high-frequent component family, to an assembly line with volume and product mix variations, can be streamlined. In order to examine this, the aim has been divided into two defined queries. Which factors affect the efficiency of the material flow, for a high-frequent component family, to an assembly line?    How can an effective material flow, for a high-frequent component family, be designed? Methodology: Both a case study and a literature study has been performed, in order to answer the queries. Literature in the areas of material and inventory control, transportation and material handling has been studied. The case study, which was carried out at a company, was based on process mapping combined with interviews and observations. Collected data from the case study have been analysed with support of literature. Findings: Different factors that are restricting the efficiency of the material flow for an assembly line has been identified. Unnecessary operations and inefficient material handling resulted in high cycle times for the material flow. Furthermore, the layout and control of the inventory resulted in long lead time and unnecessary inefficient transportations. Inadequate design and integration of the logistic subsystems has shown to be a significant cause, resulting in limited effectiveness of the studied material flow. On this basis, a new design of the material flow has been proposed, where the holistic perspective and integration are central. A new inventory design and a tugger-train transportation solution along a timed route, reduce the material handling and the number of deliveries. In addition, a pull flow system where consumption controls material replenishment, reduces both inventory levels and the number of inventory buffers. Implications: The purpose of the study has been achieved by solving the defined queries. By identifying factors that reduce the effectiveness of the material flow, a more efficient solution can be designed. The study shows that there are several possible improvement opportunities for the studied material flow. However, only one case study was performed, therefore its ability to create scientific value, can be regarded as limited. Recommendations: For further studies, it may be of interest to study several companies with similar problems to be able to draw general conclusions with scientific depth. / Syfte: Studiens syfte är att undersöka hur materialflödet för en högfrekvent komponentfamilj till en volym- och produktmässigt varierad monteringslina kan effektiviseras. För att kunna besvara denna frågeställning har syftet delats in i två problemfrågor: Vilka faktorer påverkar materialflödets effektivitet för en högfrekvent komponentfamilj fram till monteringslina? Hur kan ett effektivt materialflöde för en högfrekvent komponentfamilj utformas? Metod och genomförande: För att kunna besvara studiens syfte har en fallstudie genomförts parallellt med en litteraturstudie. Litteratur inom områdena material- och lagerstyrning, transporter och materialhantering har studerats. Fallstudien, som har genomförts på ett fallföretag, baseras på en processkartläggning i kombination med intervjuer och observationer. Insamlad data från fallstudien har analyserats med stöd från studerad litteratur. Studiens resultat: Faktorer som begränsar ett materialflödes effektivitet fram till monteringslina har identifierats. En stor andel av materialflödets totala cykeltid kunde kopplas till onödiga arbetsmoment och ineffektiv materialhantering. Ytterligare bidrog lagrets utformning och styrning till långa ledtider samt onödiga och ineffektiva transporter. Bristande utformning och integration av materialflödets delar visade sig vara en betydande orsak till begränsningen av dess effektivitet. Med detta som utgångspunkt har en ny utformning föreslagits där helhetsperspektiv och integrering har varit centralt. En ny lagerutformning, i form av materialtorg, samt en transportlösning med trucktåg utefter tidsbestämd rutt, reducerar materialhantering och antalet transporter. Tillämpningen av ett dragande flöde där monteringslinornas efterfrågan styr materialpåfyllnad, reducerar lagernivåer samt antalet buffertlager i materialflödet. Implikationer: Studiens syfte har uppnåtts genom att båda problemfrågorna har besvarats. Genom att identifiera negativa påverkansfaktorer kan förutsättningar skapas för utformningen av ett effektivt materialflöde. Studien visar att det på fallföretaget finns förbättringsmöjligheter för effektivisering av materialflödet fram till monteringslina. Då enbart ett företag studerats kan resultatet av studien och dess förmåga att skapa vetenskapligt värde, ur ett större perspektiv, anses begränsad. Rekommendationer: För vidare studier kan det vara av intresse att studera flera företag med liknande problematik för att öka studiens generaliserbarhet och förmåga att kunna presentera slutsatser med vetenskapligt djup.

Purpose - The purpose of this thesis is to identify factors that have an impact on supermarket inventory levels that supply a manufacturing line and investigate how the impact of these factors can be controlled. In order to fulfill the purpose it was broken down into two research questions.   What factors have an impact on supermarket inventory levels supplying a manufacturing line? 2.      How can the impact of these factors be controlled? Method - To answer the research questions a literature study and a case study were conducted. The empirical findings from the case study and the literature study were used to find the answer to the first research question. The identified factors in the first research question were then analysed with the theoretical framework in order to answer the second research question. Different techniques have been used in order to collect necessary data including documentation studies, interviews, observations and basic training in the case company’s procurement system (GILM).   Findings - Total safety lead time, firm time and shortage impact were discovered during the case study. These factors were not to found during the literature study because they were specific parameters that are predetermined in the case company’s procurement system. Internal material handling and supermarket order quantity were factors also found during the case study. The identified factors are divided after which tool or method that can be used to gain control over the factor. Four different tools have been identified as solutions to gain control over the internal material handling. The factors that only have one identified tool as a solution are either case specific or not attentive in the theoretical framework as the other tools.   Implications - The identified factors from the literature study are considered as common factors that can be applied for companies that have a supermarket inventory. If manufacturing companies are facing problems with their supermarket inventory levels they can increase control by investigating the tools and methods presented in this thesis. Contributions - The factors that were identified during the case study have contributed with new discoveries in the field of study, since there is limited research done in this subject regarding supermarket systems.   Research limitations - More case studies could have been performed at similar companies, in order to investigate how generalizable the answers to both research questions are.

Many real-world supply chains can be characterised as large and complex multi-echelon systems since they consist of several stages incorporating assembly and distribution processes. A challenge facing such systems is the efficient management of inventory when demand is uncertain, operating costs and customer service requirements are high. This requires specifying the inventory levels at different stages that minimise the total cost and meet target customer service levels. In order to address this problem, researchers proposed the Stochastic-Service Model and the Guaranteed-Service Model (GSM) approaches. These two approaches differ in terms of assumptions with regard to how to address demand variations and service times. This thesis develops several contributions to the GSM based multi-echelon inventory optimisation problem. First of all, we conduct a comprehensive literature review which gives a synthesis of the various GSM work developed so far. Then, we study the impact of some specific assumptions of the GSM such as bounded demand, guaranteed-service times and common review periods. Our numerical analysis shows that the bounded demand assumption may cause a deviation on customer service levels while the guaranteed-service times and common review periods assumptions may result in an increase on the total cost. In real-world supply chains the impact of these assumptions might be significant. Based on the findings presented while investigating the impact of the common review periods assumption, we develop an extension of the GSM that enables to simultaneously optimise the review periods (reorder intervals) and safety stock levels (order-up-to levels) in general acyclic multi-echelon systems. We formulate this problem as a nonlinear integer programming model. Then, we propose a sequential optimisation procedure that enables to obtain near optimal solutions with reasonable computational time. Finally, we focus on the issue of customer service level deviation in the GSM and propose two approaches in order to mitigate this deviation. The numerical study shows that the first approach outperforms the second one in terms of computational time while the second approach provides more accurate solutions in terms of cost. We also present some related issues in decentralised supply chain settings.

We study an inventory system with two potential supply modes: regular order placement opportunities happen at a fixed frequency, which defines regular review cycles, while emergency orders can be placed on every period within a regular review cycle. Regular and emergency orders incur a per-unit cost while the latest incurs an additional setup cost For a regular order lead-time equal to two periods, we show that the optimal policy with respect to the expected total discounted cost, is of (s; S) type for emergency orders while the size of a regular order depends on the inventory position following a potential emergency order. Although we could not establish the optimality for regular order lead-times exceeding two periods, substantial experimental evidence supports the conjecture that the optimal policy retains the same structure. Since the optimal policy algorithm requires significant computational effort, we develop and evaluate two heuristic policies whose operational parameters can be computed with relatively small computational effort and compare them against the optimal policy in terms of implementation difficulty, speed and accuracy for an experimental design of 3888 cases. The evaluation of the proposed optimal policy and the two heuristics requires a simulation suite flexible enough to capture the specific problem dynamics. This motivates the development of the Inventory Simulator Workbench (ISW). This inventory system simulator, written in Java, provides the user with a graphical interface and the ability to model a large range of supply chain structures and inventory ordering and distribution policies.

Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2008. / Committee Co-Chair: Alan L Erera; Committee Co-Chair: Chelsea C, White III; Committee Member: Julie Swann; Committee Member: Paul Griffin; Committee Member: Soumen Ghosh.

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 76-78).