Analyzing the make-to-stock queue in the supply chain and eBusiness settings

Thesis (Ph.D.)--Massachusetts Institute of Technology, Sloan School of Management, 2001.Includes bibliographical references (p. 149-154).This thesis presents two applications of the prototypical make-to-stock queue model that are mainly motivated by supply chain management and e-commerce issues. In the first part, we consider the decentralized version of the make-to-stock model. Two different agents that we call the supplier and the retailer control production and finish goods inventory level independently. The retailer carries finished goods inventory to service an exogenous demand and specifies a policy for replenishing his/her inventory from the upstream supplier. The supplier, on the other hand, chooses the capacity of his manufacturing facility. Demand is backlogged and both agents share the backorder cost. In addition, a linear inventory holding cost is charged to the retailer, and a linear cost for building production capacity is incurred by the supplier. The inventory level, demand rate and cost parameters are common knowledge to both agents. Under the continuous state approximation that the M/M/1 queue has an exponential rather than geometric steady-state distribution, we characterize the optimal centralized and Nash solutions, and show that a contract with linear transfer payments based on backorder, inventory and capacity levels coordinates the system in the absence of participation constraints.(cont.) We also derive explicit formulas to assess the inefficiency of the Nash equilibrium, compare the agents' decision variables and the customer service level of the centralized versus Nash solutions, and identify conditions under which a coordinating contract is desirable for both agents. In the second part, we return to the centralized version of the make-to-stock model and analyze the situation where the price that the end customers are willing to pay for the good changes dynamically and stochastically over time. We also as- sume that demand is fully backlogged and that holding and backordering costs are linearly incurred by the manufacturer. In this setting, we formulate the stochastic control problem faced by the manager. That is, at each moment of time and based on the current inventory position, the manager decides (i) whether or not to accept an incoming order and (ii) whether or not to idle the machine. We use the expected long-term average criteria to compute profits. Under heavy traffic conditions, we approximate the problem by a dynamic diffusion control problem and derive optimality (Bellman) conditions. Given the mathematical complexity of the Bellman equations, numerical and approximated solutions are presented as well as a set of computational experiments showing the quality of the proposed policies.by René Caldentey.Ph.D

Operational Research: Methods and Applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes

Operational Research: Methods and Applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order

Collaborative Procurement and Due Date Management in Supply Chains

In this thesis we analyze the procurement process of buyers and supply decisions of manufacturers. Companies are looking for ways to decrease their procurement costs, which account for a large percentage of the supply chain costs. We study the effects of demand aggregation and collaborative procurement on buyers' profitability. First, we make a high-level analysis and consider a market with multiple buyers and suppliers where multi-unit transactions for multiple items take place. The procurement costs are effected by economies of scale in the suppliers' production costs and by economies of scope in transportation. We design buyer strategies that model different collaboration levels and assess the role of collaboration under varying market conditions. Next, we analyze the procurement process at a lower level and identify benefits of inter-firm collaboration among buyers who are potential competitors in the end market. We adopt a game-theoretic approach to explore the economics of the basic mechanism underlying collaborative procurement, and determine the conditions that makes it beneficial for the participants. Besides low procurement costs, important considerations in supplier selection are responsiveness and the reliability of the suppliers in meeting demand. Hence, manufacturers face the pressure for quoting short and reliable lead times. We cover several aspects of the manufacturer's problem, such as quoting reliable due-dates based on current workload in the system, maximizing profit considering the lateness cost incurred due to late deliveries, and deciding on the level of inventory to increase responsiveness. We employ a model where demand arrival and manufacturing processes are stochastic, and obtain insights on the optimal due-date quotation policy and on the optimal inventory level.Ph.D.Committee Chair: Keskinocak, Pinar; Committee Co-Chair: Griffin, Paul M.; Committee Member: Ammons, Jane C.; Committee Member: Ayhan, Hayriye; Committee Member: Chang, Yih-Lon

Solving Multi-objective Integer Programs using Convex Preference Cones

Esta encuesta tiene dos objetivos: en primer lugar, identificar a los individuos que fueron víctimas de algún tipo de delito y la manera en que ocurrió el mismo. En segundo lugar, medir la eficacia de las distintas autoridades competentes una vez que los individuos denunciaron el delito que sufrieron. Adicionalmente la ENVEI busca indagar las percepciones que los ciudadanos tienen sobre las instituciones de justicia y el estado de derecho en Méxic