An Inventory Model with Two Classes of Customers in On-line Rental Service: Consumer Model Approach

This short version of the paper offers a model and analysis of the rental process at a subscription-based business like Netflix. We analyze a priority scheduling scheme, currently in use, that gives priority to light renters over heavy renters and show that, in some situations, it may be more profitable for the firm to give priority to heavy renters which is opposite to the Netflix’s current practice. The conditions determining the optimal initial inventory are proved analytically. Extensions are briefly discussed

Two dimensional diffusional model for leakage of macromolecules in the interstitial space

Two dimensional diffusion of macromolecules through the interstitial in the hamster cheek pouch was studied with intravital fluorescence microscopy. After topical application of Bradykinin, the movement of Fluorescein isothiocyanate (FITC)-labeled dextrans of average molecular weight 150,000 daltons (Dextran 150) was recorded on videotape which latter was played back frame-by-frame for analysis by digital image processing. Leakage of macromolecules in response to topical application of Bradykinin occurs at discrete leakage site in post caplillary venules of 15-25 um diameter, rather than in the capillary themselves. A mathematical model of two dimensional convection plus diffusion was used to simulate the macromolecule transport. The model simulations were compared with the experimental data to estimate interstitial diffusion coefficients and velocities. The model which best fit the experimental data consisted of four discrete leakage points at the origin. The additional of a small interstitial convective component in both the x and y directions gave a better fit of data than did a pure diffusion model. The apparent diffusion coefficient of FITC-dextran 150 was estimated to be 1.0x10-7 cm2/sec. The interstitial velocities on the X- and Y- axes were both the same and estimetal as 1.0x10-4 cm/sec for the best fit in the interstitial diffusion space of the hamster cheek pouch

An Analysis of Personality Traits and Learning Styles as Predictors of Academic Performance

The present study examined the influence of Big Five personality traits and learning styles on cognitive and affective academic performance, and gender differences in learning styles. A survey research was employed to collect the data from the target population of students. Participants (N = 1,529) were students who enrolled in Business Administration and Communication Arts at Assumption University of Thailand.Overall, the results indicated that personality traits found to be better predictors of cognitive and affective academic performance than did learning styles. Conscientiousness was a significant contributor of academic performance. Among five personality traits, Conscientiousness, Openness, Agreeableness significantly predicted cognitive academic performance, whereas Conscientiousness, Openness, Agreeableness, and Emotional Stability significantly predicted affective academic performance. Learning styles were also related to cognitive academic performance. Moreover, students in Business Administration reported higher scores in Conscientiousness, Agreeableness, and Emotional Stability than those in Communication Arts. The results showed no significant differences in learning styles between genders

Competition and Coordination in a Two-Channel Supply Chain

We study competition and coordination in a supply chain in which a single supplier both operates a direct channel and sells its product through multiple differentiated retailers. We study analytically the supply chain with symmetric retailers and find that the supplier prefers to have as many retailers as possible in the market, even if the retailers' equilibrium retail price is lower than that of the supplier, and even if the number of retailers and their cost or market advantage prevent sales through the direct channel. We find that the two-channel supply chain may be subject to inefficiencies not present in the single-channel supply chain. We show that several contracts known to coordinate a single-channel supply chain do not coordinate the two-channel supply chain; thus we propose a linear quantity discount contract and demonstrate its ability to perfectly coordinate the two-channel supply chain with symmetric retailers. We provide some analytical results for the supply chain with asymmetric retailers and propose an efficient solution approach for finding the equilibrium. We find numerically that the supplier still benefits from having more retailers in the market and that linear quantity discount contracts can mitigate supply chain inefficiency, though they no longer achieve perfect coordination

MULTI-PERIOD SUPPLY CHAIN COORDINATION USING TRADE PROMOTION: COMPLEMENTARY SLACKNESS APPROACH

In this paper, a two-level supply chain network with a single manufacturer supplying a single product to a single retailer is studied. This research uses a trade promotion strategy to coordinate the supply chain by finding the optimal pre-announced multi-period wholesale prices that can induce the retailer’s decentralized decisions to be the same as the retailer’s centralized decisions with the minimum total cost for the supply chain. The manufacturer makes production, inventory, and wholesale price decisions. The retailer makes ordering and inventory decisions. A procedure is proposed to determine optimal wholesale prices to pre-announce in each period to the retailer, coordinating the supply chain using complementary slackness conditions. The results show the coordination benefits for a supply chain when the setup or reorder cost is high but the average demand is low. Finally, the performance of the proposed method is compared with the performance of the “Every Day Low Price” wholesale price policy

Time-partitioning heuristic algorithm for optimal production, inventory, and transportation planning with direct shipment

We developed a mixed integer linear programming model for an integrated decision problem of production, inventory, and transportation planning. Our model combines the direct shipment into the production, inventory, and distribution planning. The objective was to minimize the total operation cost which is comprised of production setup cost, inventory holding cost, transportation cost, and reorder cost. The model is solved to optimality using the leading optimization software, IBM ILOG CPLEX (CPLEX), but the software shows a limited capability to solve large size problems. A time-partitioning heuristic algorithm is proposed to efficiently solve the problem. Numerical experiments are extensively conducted to test the proposed algorithm. In our numerical experiments, the proposed algorithm can solve many large size problems, whereas CPLEX fails to solve them. The numerical experiment shows that a company can gain a significant saving by optimally incorporating the direct shipment. The proposed heuristic algorithm performs well in most cases in terms of a total cost and the computation time

Nurse scheduling in a hospital emergency department: A case study at a Thai university hospital

Common problems of Thai nurses are low quality of life, working long hours, and a high turnover rate. The workload imbalance among nurses also worsens the turnover rate. With careful schedule planning, nurses do not have to work in consecutive shifts and can rest more. We interviewed and collected data from an emergency department at a hospital administered by a Thai university, related to objectives and constraints of monthly nurse scheduling, and actual monthly schedules. A multi-objective mathematical model was developed using the open source “OpenSolver” software in MS-Excel for nurse schedulers to freely use. We tested the model using actual data collected from the department and found that the schedules created by the model tended to provide more balanced workloads and more days off compared to the schedules created manually by a real scheduler. The model also suggested an easy policy to increase the number of nurses for future expansion

HEURISTIC PROCEDURE FOR MULTI-WORKDAY VEHICLE ROUTING PROBLEM WITH PRE-ASSIGNED WORKERS AND MANUAL UNLOADING

This paper deals with the multi-workday vehicle routing problem (MW-VRP) where delivery workers are pre-assigned to vehicles. At customer locations, workers must manually unload goods from vehicles. For each worker, the daily accumulated physical workload depends on the number of customers served by the vehicle and load demands at those customers. The MW-VRP is intended to determine daily delivery routes for a given set of vehicles over the multi-workday delivery period such that the maximum average percent residual energy (PRE) among all workers is minimized. A heuristic procedure is developed to firstly determine delivery routes for vehicles. Next, a greedy exchange algorithm is used to decrease the maximum average PRE among workers and total travel distance of vehicles. The results from the given numerical example show that the heuristic procedure is able to generate the routing solution with the same maximum average PRE as that from the optimal solution, but with a slightly greater total travel distance (11.57%)