Optimal trade credit and lot size policies in economic production quantity models with learning curve production costs

[[abstract]]In reality, a seller (e.g., a supplier or a manufacturer) frequently offers his/her buyers trade credit (e.g., permissible delay in payment). Trade credit reduces the buyer's holding cost of inventory and hence attracts new buyers who consider it to be a type of price reduction. On the other hand, granting trade credit also increases the seller's opportunity cost (i.e., the loss of capital opportunity during the credit period) and default risk (i.e., the event in which the buyer will be unable to make the required payments on his/her debt obligation). In addition, it is a well-known fact of learning-by-doing that production cost of a new product declines by a factor of from 10 to 50 percent each time the accumulated production volume doubles. Therefore, we propose an economic production quantity model from the seller's prospective to determine his/her optimal trade credit period and production lot size simultaneously in which (i) trade credit increases not only sales but also opportunity cost and default risk, and (ii) production cost declines and obeys a learning curve phenomenon. Then the necessary and sufficient conditions to obtain the seller's optimal trade credit and order quantity are derived. Finally, we use some numerical examples to illustrate the theoretical results and to provide some managerial insights.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

Inventory Management and Supply Chain Coordination Mechanisms

This dissertation is on inventory management and supply chain coordination mechanisms within an economic order quantity framework. Specifically, this research focuses on modeling optimal order policies and coordination mechanisms for a supply chain involving items which experience probabilistic failure during storage. These items are common types of manufactured items which, nonetheless, require specialized order policy considerations due to their unique characteristics. We first develop the solution for the buyer’s problem through the use of an economic order quantity (EOQ) model incorporating item failure. We then proceed to model the manufacturer’s problem through the use of an economic production quantity (EPQ) model. Finally, we consider mechanisms to promote mutually-beneficial cooperation between the supplier and n buyers in service of coordinating the entire supply chain. While prior research has focused on items which can be repaired or sold at a discount upon failure, such models are inappropriate for systems where repair costs exceed or are equivalent to item costs and imperfect items are unacceptable. Examples of industries featuring these inventory conditions include the medical, defense, and electronics industries where defective items are largely useless. First, our EOQ model considers a buyer-supplier relationship featuring delivery and stocking of items which experience probabilistic failure in storage. Thereafter, our EPQ model considers in-house production of such items. Collectively, our EOQ and EPQ models provide methods for developing optimal order policies necessary to achieve practicable supply chain coordination. In order to validate the necessity of the developed models, we include an empirical analysis of item reliability for some common mechanical components used in the defense industry, thereby identifying items which fail in the manner modeled in this dissertation. Having considered optimal order policies for both buyers and suppliers, we next develop an optimal solution for a coordinated supply chain. The proposed solution allows the manufacturer to coordinate a supply chain consisting of n buyers in order to achieve a common replenishment time. Through this optimization framework, we minimize total system-wide costs and derive the cost savings associated with our coordinated solution. Numerical examples are then used to demonstrate the magnitude of cost savings achievable through our coordination framework. We conclude by proposing several mechanisms for leveraging the resulting cost savings to induce mutually-beneficial cooperation between the supplier and multiple buyers. Given the lack of buyer-supplier cooperation noted in empirical research related to supply chain coordination, our identification of specific mechanisms useful for inducing mutually-beneficial cooperation between buyers and suppliers represents an important practical contribution to the supply chain coordination literature. These models are accompanied by a thorough overview and discussion of economic order quantity theory, optimal order policies, and supply chain coordination mechanisms.Ph.D., Business Administration -- Drexel University, 201

Sustainable Inventory Management Model for High-Volume Material with Limited Storage Space under Stochastic Demand and Supply

Inventory management and control has become an important management function, which is vital in ensuring the efficiency and profitability of a company’s operations. Hence, several research studies attempted to develop models to be used to minimise the quantities of excess inventory, in order to reduce their associated costs without compromising both operational efficiency and customers’ needs. The Economic Order Quantity (EOQ) model is one of the most used of these models; however, this model has a number of limiting assumptions, which led to the development of a number of extensions for this model to increase its applicability to the modern-day business environment. Therefore, in this research study, a sustainable inventory management model is developed based on the EOQ concept to optimise the ordering and storage of large-volume inventory, which deteriorates over time, with limited storage space, such as steel, under stochastic demand, supply and backorders. Two control systems were developed and tested in this research study in order to select the most robust system: an open-loop system, based on direct control through which five different time series for each stochastic variable were generated, before an attempt to optimise the average profit was conducted; and a closed-loop system, which uses a neural network, depicting the different business and economic conditions associated with the steel manufacturing industry, to generate the optimal control parameters for each week across the entire planning horizon. A sensitivity analysis proved that the closed-loop neural network control system was more accurate in depicting real-life business conditions, and more robust in optimising the inventory management process for a large-volume, deteriorating item. Moreover, due to its advantages over other techniques, a meta-heuristic Particle Swarm Optimisation (PSO) algorithm was used to solve this model. This model is implemented throughout the research in the case of a steel manufacturing factory under different operational and extreme economic scenarios. As a result of the case study, the developed model proved its robustness and accuracy in managing the inventory of such a unique industry

Responsible Inventory Models for Operation and Logistics Management

The industrialization and the subsequent economic development occurred in the last century have led industrialized societies to pursue increasingly higher economic and financial goals, laying temporarily aside the safeguard of the environment and the defense of human health. However, over the last decade, modern societies have begun to reconsider the importance of social and environmental issues nearby the economic and financial goals. In the real industrial environment as well as in today research activities, new concepts have been introduced, such as sustainable development (SD), green supply chain and ergonomics of the workplace. The notion of “triple bottom line” (3BL) accounting has become increasingly important in industrial management over the last few years (Norman and MacDonald, 2004). The main idea behind the 3BL paradigm is that companies’ ultimate success should not be measured only by the traditional financial results, but also by their ethical and environmental performances. Social and environmental responsibility is essential because a healthy society cannot be achieved and maintained if the population is in poor health. The increasing interest in sustainable development spurs companies and researchers to treat operations management and logistics decisions as a whole by integrating economic, environmental, and social goals (Bouchery et al., 2012). Because of the wideness of the field under consideration, this Ph.D. thesis focuses on a restricted selection of topics, that is Inventory Management and in particular the Lot Sizing problem. The lot sizing problem is undoubtedly one of the most traditional operations management interests, so much so that the first research about lot sizing has been faced more than one century ago (Harris, 1913). The main objectives of this thesis are listed below: 1) The study and the detailed analysis of the existing literature concerning Inventory Management and Lot Sizing, supporting the management of production and logistics activities. In particular, this thesis aims to highlight the different factors and decision-making approaches behind the existing models in the literature. Moreover, it develops a conceptual framework identifying the associated sub-problems, the decision variables and the sources of sustainable achievement in the logistics decisions. The last part of the literature analysis outlines the requirements for future researches. 2) The development of new computational models supporting the Inventory Management and Sustainable Lot Sizing. As a result, an integrated methodological procedure has been developed by making a complete mathematical modeling of the Sustainable Lot Sizing problem. Such a method has been properly validated with data derived from real cases. 3) Understanding and applying the multi-objective optimization techniques, in order to analyze the economic, environmental and social impacts derived from choices concerning the supply, transport and management of incoming materials to a production system. 4) The analysis of the feasibility and convenience of governmental systems of incentives to promote the reduction of emissions owing to the procurement and storage of purchasing materials. A new method based on the multi-objective theory is presented by applying the models developed and by conducting a sensitivity analysis. This method is able to quantify the effectiveness of carbon reduction incentives on varying the input parameters of the problem. 5) Extending the method developed in the first part of the research for the “Single-buyer” case in a "multi-buyer" optics, by introducing the possibility of Horizontal Cooperation. A kind of cooperation among companies in different stages of the purchasing and transportation of raw materials and components on a global scale is the Haulage Sharing approach which is here taken into consideration in depth. This research was supported by a fruitful collaboration with Prof. Robert W. Grubbström (University of Linkoping, Sweden) and its aim has been from the beginning to make a breakthrough both in the theoretical basis concerning sustainable Lot Sizing, and in the subsequent practical application in today industrial contexts

Decentralized and centralized supply chains with trade credit option

The notion of a trade credit period is a common business practice, where a supplier allows a buyer a specified period to make a payment in full for a purchase made. The objective of this thesis is to explore the role of such a credit payment option in supply chain management. Towards this end, a two-echelon supply chain, consisting of a single supplier (e.g. manufacturer) and the cases of both a single and multiple buyers (e.g. retailers) is examined under decentralized (independent) and centralized (coordinated) decision making scenarios. The major emphasis of this research is limited to the case of a single product with price-sensitive deterministic, as well as stochastic market demand.The conditions under which a trade credit period should be offered and its appropriate length are determined from the supplier’s perspective under the decentralized case. Under the centralized decision scenario, the efficacy of a trade credit policy as a supply chain coordination mechanism is thoroughly analyzed and guidelines for pricing, production and delivery decisions are developed. The concepts developed in this study are illustrated via a number of numerical examples, in conjunction with thorough sensitivity analyses involving some selected problem parameters.The major contribution of this thesis is that we incorporate the pricing and inventory issues in supply chains with an endogenous credit payment period. This is the first study that examines the efficacy of trade credit option as a coordination mechanism. We propose a coordination mechanism that coordinates the supply chain, when a trade credit by itself is not sufficient to serve such a purpose, while preserving the benefits of a trade credit option. Also, this study is the first to examine the issues concerning trade credit under price sensitive stochastic demand. Another first for this work is the exploration of the implications of a trade credit policy in supply chains consisting of multiple competing retailers. The effects of the extent of competition and the market size on trade credit policy are evaluated. Our analyses lead to some important practical implications, to serve as managerial guidelines.Ph.D., Decision Sciences -- Drexel University, 201

Supply chain operation strategies and risk management with working capital consideration: a case study of the supply chain of lightning protection products in China

JEL: G32; D21With the advent of economic globalization, competition is increasingly hinged on supply chain. Meanwhile, working capital becomes a key element of a successful supply chain. This thesis researches the supply chain of a typical lightning protection products manufacturer in China, i.e. Company Z. The thesis starts with the working capital issues in the supply chain of Company Z; then, with the help of questionnaires and a sensible indicator system and weight assignments; analyzes and summarizes the status quo of the working capital and related key issues in the supply chain consisting of Company Z and its suppliers and customers. Building on such analysis, a two-dimensional classification matrix is created to divide suppliers and customers into four groups (namely, strategic-type, partner-type, general-type, and bottleneck-type) and supply chain operation strategies are devised for each group. Furthermore, based on such supply chain operations strategies of Company Z, a working capital risk management mechanism with an early warning system is developed, and a supply chain-based financing platform is designed to help the supply chain participants seek financing and share the risks with working capital.Com o advento da era da globalização económica, a cadeia de suprimentos tornou-se cada vez mais importante para a concorrência empresarial, e ao mesmo tempo, o fundo de maneio tornou-se num elemento chave para o sucesso da gestão da cadeia de suprimentos. Neste trabalho, a cadeia de suprimentos de uma empresa chinesa de fabricação de produtos típicos de proteção contra relâmpagos, a empresa Z, é o objeto de estudo. Tomando como ponto de partida os problemas de fundo de maneio existentes na cadeia de suprimentos da empresa Z, por meio de questionários combinados com o estabelecimento de um sistema de indexação e de ponderação, foram realizadas análises precisas sobre problemas-chaves existentes e da situação atual da gestão do fundo de maneio da cadeia de suprimentos a montante e a jusante da empresa Z. Estabeleceram-se matrizes bidimensionais de classificação para respectivamente subdividir os fornecedores e clientes em quatro categorias, a saber, categoria de fornecedores/clientes estratégicos, categoria de fornecedores/clientes parceiros, categoria de fornecedores/clientes comuns e categoria de fornecedores/clientes críticos (“engarrafamentos”) e propor estratégias diferentes na cadeia de suprimentos para diferentes categorias. Por fim, o nosso estudo indica que segundo a estratégia de operação da cadeia de suprimentos da empresa Z, deve ser estabelecido um mecanismo de controle e gestão de risco de fundo de maneio, um sistema de alerta de risco e, ainda, projetar uma plataforma de financiamento a fim de prover o financiamento emergente da cadeia de suprimentos da empresa Z e a partilha dos riscos de gestão do fundo de maneio

The Option Element in Contracting

Most contractual arrangements are either structured as options or include options as important elements. As a result, many of the major doctrines of contract law effectively operate to create or to set the terms of such options. For instance, it has long been recognized that a contract that is enforceable only through monetary liability operates in practice as an option, because as a legal matter the promisor retains the power either to perform or to breach and pay damages. Similarly, the doctrine of promissory estoppel, which attaches liability to precontractual statements in cases where they are reasonably relied upon, effectively grants an option to the relying party to enforce the promise or not as she finds convenient. Similar options arise where contracts are voidable – but not void – for reasons of mistake, lack of capacity, or fraud