Boray Huang

A Make-to-Stock System with Multiple Customer Classes and Batch Ordering

The present invention provides: a hydrolysis stabilizer for ester group-containing resin, comprising, as the main component, a carbodiimide which is derived from tetramethylxylylene diisocyanate, and which has remaining isocyanate groups in an amount of 3% by weight or less or has the terminal isocyanate groups blocked with a monoisocyanate(s); and a method for hydrolysis stabilization of ester group-containing resin, which comprises mixing an ester group-containing resin with a carbodiimide which is derived from tetramethylxylylene diisocyanate represented by the above formula and which has remaining isocyanate groups in an amount of 3% by weight or less or has the terminal isocyanate groups blocked with a monoisocyanate(s).

Optimal production and rationing decisions in supply chains with information sharing

This paper considers a two-echelon capacitated supply chain with two non-identical retailers and information sharing. We characterize the optimal inventory policies. We also study the benefits of the optimal stock rationing policy over the first come first served (FCFS) and the modified echelon-stock rationing (MESR) policies.

The effects of lumpy demand and shipment size constraint: A response to Revisit the note on supply chain integration in vendor-managed inventory

This paper responds to a comment by Wang et al. [3] regarding the disagreement between Yao et al. [4] and van der Vlist et al. [2] on the impact of vender-managed-inventory (VMI). We explore the factors which affect the shipment size from the vendor to the buyer and identify the conditions where the shipment size will increase/decrease under VMI. A numerical example also shows when and how the inventory shifts between the supplier and the buyer.

The Impacts of Carbon Tariff on Green Supply Chain Design

With the growing awareness of global warming, many companies worldwide are improving their supply chain sustainability, under pressure from the government or their own shareholders. However, not all countries around the world equally emphasize the threat. For example, some countries still have not implemented any carbon dioxide emission regulations to address this problem. Carbon regulations in only subglobal areas may result in even higher global emissions because of carbon leakage. One possible approach to cope with the carbon leakage problem is to impose carbon tariffs on the goods from unregulated countries. In this paper, a mathematical model is built to explore the impacts of carbon tariff imposition on the supply chain network design, where the carbon tariff is imposed when the goods flow from unregulated countries to regulated countries. Moreover, our paper provides a complete experimental study by applying this model in a real case study, Company G, a major Taiwan-based multinational company in the electronic products industry. The outcomes demonstrate the conditions where the introduction of carbon tariffs forces firms from unregulated countries to take actions to reduce carbon emissions.

On a multi-product lot scheduling problem subject to an imperfect process with standby modules

An Economic Lot Scheduling Problem is considered under the condition that the production process may shift from an in-control state to an out-of-control state due to the deterioration of the facility’s key module. We adopt the Common Cycle policy in two mathematical models depending on whether the key module is repairable or not. Several standby modules are available during a production run. For the model with non-repairable key modules, the active key module, once deteriorated, is disposed of and replaced by a new standby. For the model with repairable key modules, the active one is replaced by a standby as soon as it is deteriorated. The failing module will be restored in a repair shop and rejoin the standbys. The objective is to determine an optimal production cycle time and the economic number of standby modules in order to minimise the long-term average cost including set-up, inventory carrying, standby and defective costs. The convexity of the cost functions is revealed so that efficient algorithms can be developed accordingly to achieve optimal production-inventory policies. It is shown that these policies can be used to significantly improve the system performance.

Portfolio optimization with transaction costs: a two-period mean-variance model

In this paper, we study a multiperiod mean-variance portfolio optimization problem in the presence of proportional transaction costs. Many existing studies have shown that transaction costs can significantly affect investors’ behavior. However, even under simple assumptions, closed-form solutions are not easy to obtain when transaction costs are considered. As a result, they are often ignored in multiperiod portfolio analysis, which leads to suboptimal solutions. To provide better insight for this complex problem, this paper studies a two-period problem that considers one risk-free and one risky asset. Whenever there is a trade after the initial asset allocation, the investor incurs a linear transaction cost. Through a mean-variance model, we derive the closed-form expressions of the optimal thresholds for investors to re-allocate their resources. These thresholds divide the action space into three regions. Some important properties of the analytical solution are identified, which shed light on solving multiperiod problems.

Supporting small suppliers through buyer-backed purchase order financing

Supporting small and medium enterprises (SMEs) to access finance has received rapidly-rising attention in recent years. In some countries, large buyers in supply chains are considering credit guarantee schemes (CGS) through which the credit coverage can be extended to assist their SME suppliers. While such support is beneficial to the suppliers, an issue arises regarding the motivation of the large buyers to join and support the SME suppliers. In practice, SMEs are often attractive but riskier sources of supply. Supporting SME suppliers through the financial guarantee may bring even more risk concern to buyers. To study the buyers’ sourcing and guarantee strategy, we analyze a simplified model where a core enterprise procures components from only two sources: an SME supplier with a lower price and the spot market with a higher price. A novel Buyer-Backed Purchase Order Financing (BPOF) scheme is studied in supporting the supplier’s financing. We analyze the effect of the market interest and identify the properties of the buyer’s optimal joint sourcing and credit-guarantee decisions. Through numerical experiments, BPOF is shown to significantly improve the core enterprise‘s profitability.

Determining the conditions for reverse triage in emergency medical services using queuing theory

In emergency health care, there are situations where the less wounded are treated in preference to the more severely wounded, so called reverse triage. This may arise in situations such as war where soldiers are required to return to the battlefield as quickly as possible, or disaster situations where medical resources are limited in order to conserve resources for those likely to survive without requiring advanced medical care. This article is to study the reverse triage in time-critical systems, where conditions of patients may deteriorate while waiting for treatment. A queueing model with transfers and abandonments is developed to study the health care system. Using smoothed rate truncation method, sufficient conditions of reverse triage are derived, under which non-critical patients are treated with priority. For other conditions, the optimal policy is very complicated. We suggest a dynamic control policy according to the system state rather than any static priority policies.

Jointly Consider Acquisition Price, Trade in Rebate and Selling Price in Remanufacturing

In remanufacturing business of durable products, a special feature is the correlation between supply and demand. This is because customers who return their end-of-life products usually need to do replacement purchase. At the same time, pricing strategies have been widely adopted by remanufacturing companies to balance the supply and demand. In this study, we consider the pricing strategies with the presence of replacement purchase. We argue that despite the acquisition price for return products and the selling price to new customers, remanufacturing company should offer a trade in program to the replacement customer segment. We study the optimal pricing policies when return yield rate is uncertain. We also compare the profitability of different pricing schemes under different yield variations.

Reduce shortage with self-reservation policy for a manufacturer paying both fixed and variable stockout expenditure

This study considers a single item make-to-stock system with continuous-time production and inventory controls to meet bulk demand with an exponential inter-arrival time. A key issue in this system is the non-convex shortage cost consisting of fixed and variable expenditures when the demand is not fully satisfied. We propose a self-reservation policy by building a Markov Decision Process to minimize the overall cost. We find that the optimal production control is still a base stock policy, but the structure of the optimal self-reservation policy is very complicated. However, if the effective outstanding variable shortage cost is sufficiently large, the optimal self-reservation policy has an easy form of “Reserve All or Nothing.” Our numerical examples indicate the optimal policy may reduce the total average cost by 47% on average.