Jun-Yeon Lee

California State University, Northridge | CSUN · Department of Systems and Operations Management

Seaborne trade plays a vital role in global trade by facilitating the movement of cargo across the globe. However, maritime transactions are characterized by inherent complexity and frequently exhibit deficiencies in transparency and operational efficiency. This is due to primary factors such as substantial amount of paperwork, ineffective data sha...

The globalisation of the food industry increases the complexity and the difficulty in enhancing efficiency and solving issues in food supply chains. Blockchain is a promising decentralised information technology that could benefit food supply chains by reducing transaction cost and time, increasing process transparency, security, and efficiency, as...

We consider a supply chain consisting of a supplier and a buyer whose efforts jointly influence carbon emissions per unit of the product. The product demand is affected by the effort levels. The carbon footprint is allocated to the supply chain members by a social planner, and they pay carbon penalties for their allocated emissions. We first examin...

Investment in carbon emissions reduction is an important decision for many firms due to climate change and growing pressures from various stakeholders. In this paper, we examine the problem of jointly determining optimal order quantity and investment in carbon emissions reduction in the EOQ model with a cap-and-price regulation policy, in which the...

We examine vendor-managed inventory contracts in a (Q, r) inventory system between a supplier and a retailer, in which a stockout penalty is charged to the supplier based on the length of the time period during which stockouts occur at the retailer. Linear and quadratic forms of the time-dependent stockout penalty are considered. For the determinis...

We examine (z, Z)-type contracts for vendor-managed inventory (VMI) between a supplier and a retailer from the retailer's perspective. A (z, Z) VMI contract specifies minimum and maximum inventory levels and their corresponding under- and over-stocking penalties. The retailer chooses the contract parameter values and the supplier decides whether to...

We examine vendor-managed inventory (VMI) systems with stockout-cost sharing between a supplier and a customer using an EOQ model with shortages allowed under limited storage capacity, in which a stockout penalty is charged to the supplier when stockouts occur at the customer. In the VMI systems the customer and the supplier minimize their own cost...

We examine a periodic-review stochastic inventory model in which the buyer places orders to meet stochastic demands under an incremental quantity discount schedule with a single price-break point. With a general demand distribution, we prove the optimality of a state-dependent base-stock policy for the single-period problem and provide simple bound...

Vendor-managed inventory (VMI) is a business practice in which the supplier manages the inventory at the customer's premises and makes replenishment decisions. VMI has been extensively studied over a short period of time since it was successfully implemented in the industry in the late 1980s. In this paper, we classify and review theoretical and em...

We examine the problem of designing a vendor-managed inventory (VMI) contract with consignment stock and stockout-cost sharing in a (Q, r) inventory system between a supplier and a retailer. In particular, the contract specifies fixed and proportional penalties charged to the supplier when stockouts occur at the retailer. The retailer chooses the p...

Vendor-managed inventory (VMI) is a well-known industry practice for supply chain collaboration. In this paper we consider a periodic-review stochastic inventory model to examine the benefits of VMI in a global environment, in which the supplier and the retailer face exchange rate uncertainty and incur different fixed ordering costs. Our study sugg...

We examine a single-item, periodic-review inventory system with stochastic leadtimes, in which a replenishment order is delivered immediately or one period later, depending probabilistically on costly effort. The objective is to determine a joint inventory policy and effort-choice strategy that minimizes the expected total costs. Our analytical and...

We consider a single-item, infinite-horizon, continuous-review (S-1,S) inventory system with Poisson demand and stochastic leadtimes. In the business scenario examined, the supplier exerts a one-time effort that reduces the mean and/or variance of replenishment leadtimes, and the inventory manager of the system makes periodic payments to the suppli...

We examine quantity discount contracts between a manufacturer and a retailer in a stochastic, two-period inventory model. The retailer places an order in each of the two periods to meet stochastic demands. The manufacturer gives the retailer a price discount on purchases in the second period in excess of the first-period order quantity (incremental...

We examine the problem of designing and implementing a continuous-review (Q,r) inventory system from an agency perspective, in which the agent's effort influences the item's replenishment leadtime. Our results are as follows: if the agent is risk-neutral, a linear or quadratic contract achieves first-best. For a risk-averse agent with an exponentia...

In this thesis we examine several business scenarios in which the owner (principal) of an inventory system, who is risk-neutral, delegates its design and/or implementation to an agent (internal manager, external supplier, or consultant) whose hidden effort influences the duration of the item's replenishment leadtimes. In the (Q, r) agency model, we...

Most of the descent methods developed so far suffer from the computational burden due to a sequence of constrained quadratic subproblems which are needed to obtain a descent direction. In this paper we present a class of proximal-type descent methods with a new direction-finding subproblem. Especially, two of them have a linear programming subprobl...