I-Hsuan Hong

Planning the e-Scrap Reverse Production System Under Uncertainty in the State of Georgia: A Case Study

Due to legislative requirements, environmental concerns, and market image, the disposition of end-of-life e-scrap is attracting tremendous attention in many parts of the world today. Effective management of returned used product flows can have a great impact on the profitability and resulting financial viability of associated e-scrap reverse production systems. However, designing efficient e-scrap reverse production systems is complicated by the high degree of uncertainty surrounding several key factors. Very few examples of this complex design problem are documented in the academic literature. This paper contributes as analysis of a new, large-scale application that designs an infrastructure to process used televisions, monitors, and computer central processing units (CPUs) in the state of Georgia in the U.S. The case study employs a scenario-based robust optimization model for supporting strategic e-scrap reverse production infrastructure design decisions under uncertainty. A mixed integer linear programming (MILP) model is used to maximize the system net profit for specified deterministic parameter values in each scenario, and then a min-max robust optimization methodology finds a robust solution for all of the scenarios

Scenario relaxation algorithm for finite scenario-based min-max regret and min-max relative regret robust optimization

Most practical decision-making problems are compounded in difficulty by the degree of uncertainty and ambiguity surrounding the key model parameters. Decision makers may be confronted with problems in which no sufficient historical information is available to make estimates of the probability distributions for uncertain parameter values. In these situations, decision makers are not able to search for the long-term decision setting with the best long-run average performance. Instead, decision makers are searching for the robust long-term decision setting that performs relatively well across all possible realizations of uncertainty without attempting to assign an assumed probability distribution to any ambiguous parameter. In this paper, we propose an iterative algorithm for solving min-max regret and min-max relative regret robust optimization problems for two-stage decision-making under uncertainty (ambiguity) where the structure of the first-stage problem is a mixed integer (binary) linear programming model and the structure of the second-stage problem is a linear programming model. The algorithm guarantees termination at an optimal robust solution, if one exists. A number of applications of the proposed algorithm are demonstrated. All results illustrate good performance of the proposed algorithm.

A model for batch available-to-promise in order fulfillment processes for TFT-LCD production chains

The main purpose of this study is to explicitly highlight several special production characteristics in a thin-film transistor liquid crystal display (TFT-LCD) manufacturing industry and to present an available-to-promise (ATP) model that supports decision-making in order fulfillment processes for TFT-LCD manufacturing. A TFT-LCD production chain differs from others in its special production characteristics such as alternative bill-of-materials (BOMs), grade transition, etc., which are significant factors driving a success in an ATP implementation. Customers may specify a quality level and the materials to be used in a finished product in inquiry orders. The quality of the working-in-process can be altered using different assembled components. The ATP model enhances the responsiveness of order fulfillment processes. The ATP model directly links available material resources and capacity with inquiries or existing customer orders to improve the overall performance of the production chain. A case study using the model demonstrates the effectiveness and efficiency of the proposed ATP model in a TFT-LCD production chain and investigates the sensitivity of TFT-LCD plant performance to changes in order batching intervals.

The effects of government subsidies on decentralised reverse supply chains

This paper examines the impacts of exogenous government subsidies on recycled material flows in decentralised reverse supply chains where players behave according to their own interests. We present a four-tiered network equilibrium model consisting of the sources of electronic scrap products and the collectors, processors and demand markets. We mathematically transform the players’ optimality conditions governing players’ behaviours into a variational inequality formulation. We investigate the impact of alternate schemes of government subsidies on the equilibrium amount, subsidy effectiveness and subsidy elasticity. The real-world case study shows that subsidising the tier of processors demonstrates the superiority of the investigated performance measures.

The equilibrium contract rent and reward money under incomplete information in reverse supply chains

Product homogeneity affects the unit profit of the recycled products.We propose a decentralized reverse supply chain model with incomplete information.We derive the equilibrium contract rent for the third-party recycler.We investigate the equilibrium reward money for customers returning recycled products. Many electronic end-of-life (EOL) products are becoming obsolete sooner due to advances in technology. Hence, manufacturers hire third-party recyclers as subcontractors to recycle brand-name products. A complicated profile of recycling EOL products adds a significant cost burden to the third-party recyclers, while only the manufacturer has a superior understanding of the profile of recycling EOL products (homogeneity degree of EOL products). This paper describes the decision of the manufacturer and the third-party recycler in reverse supply chains under incomplete information of product homogeneity, which affects the unit profit of recycled products. The supply chain model assumes that customers receive reward money for returning obsolete products, and that the manufacturer as a leader and the third-party recycler as a follower determine the contract rent offered to the third-party recycler and the reward money paid to customers, respectively. Both the manufacturer and third-party recycler want to maximize their profit functions. We propose a game theoretical approach to search for the equilibrium contract rent for the third-party recycler and the equilibrium reward money for customers returning products for recycling. We conclude with a discussion of the impact of the contract rent and reward money on the equilibrium solution.

Examining subsidy impacts on recycled WEEE material flows

Abstract: Government subsidies to recycling systems can play important roles in driving or curtailing the flows of recycled items. This chapter examines the impacts of exogenous subsidies on recycled material flows in a decentralized recycling system where each entity acts according to its own interests. The chapter also discusses the issue of subsidy impact on exporting recycled items. Our findings should be useful to policy makers in creating the most efficient subsidy policy.