Research Articles
In this issue we bring you two great articles from the pages of INFORMS journals on a theme: optimization of the handling of liquids in a medical environment. The purpose of this section is to highlight research that is both accessible and interesting, and these papers certainly fulfill those criteria.
Routing test drops like buses
In the first article we reprint from the Journal on Computing, Optimal Testing of Digital Microfluidic Biochips, Bogdan Pasaniuc, Robert Garfinkel, Ion Mandoiu, and Alex Zelikovsky determine the best way to test specialized medical equipment. Digital microfluidic biochips are rectangular arrays of electrodes that are used to precisely manipulate nanoliter volumes of biological fluids and chemical reagents. These biochips are typically used in applications with a safety-critical nature, which makes their frequent testing essential. For testing, test droplets are routed across the chip, and their arrivals are recorded. The testers have flexibility with the route they use across the chip: they can use voltages to choose the path along a grid dynamically. Using a single drop is the easiest way to route, but testing an entire chip this way can take three days. Using multiple drops can make the testing go faster, but route selection becomes more difficult because of possible interference among drops. Acknowledging similarities with vehicle routing and bus routing in particular (cities don’t want two bus routes too close together either), the authors model the chips as a grid network and formulate their optimal testing as a routing problem with an objective of minimization of completion time. Their formulation differs from the standard vehicle routing models in the sense that they model number of vehicles as a variable and include constraints for interference of multiple droplets according to their relative locations on the grid network. Upon proving computational complexity, authors develop optimal and approximation algorithms for efficient solution of the problem.
Reprinted by permission, Bogdan Pasaniuc, Robert Garfinkel, Ion Mandoiu, and Alex Zelikovsky, "Optimal Testing of Digital Microfluidic Biochips", INFORMS Journal On Computing, Volume (23), Issue 4, Fall 2011, Copyright (2012), the Institute for Operations Research and the Management Sciences, 7240 Parkway Drive, Suite 300, Hanover, Maryland 21076 USA
Perfect policies for perishable platelets
Deming Zhou, Lawrence Leung, and William Pierskalla determine best replenishment policies for blood products in Inventory Management of Platelets in Hospitals: Optimal Inventory Policy for Perishable Products with Regular and Optional Expedited Replenishments, reprinted from Manufacturing & Service Operations Management. Platelets are needed by the body to help with clotting, and are used in hospitals for treating patients with recent surgeries, transplants, and leukemia. They essentially have a shelf life of three days, making the choice of an inventory policy critically important. Here, the authors investigate a basestock policy with a twist: the inventory manager can make an additional basestock order within the main cycle at an expedited cost, but he might receive older blood for this expedited shipment. In this fixed-lifetime perishable problem with dual modes of replenishments, the authors characterize the problem, prove the uniqueness and existence of an optimal policy, and – using real data – provide numerical results and a sensitivity analysis.
Reprinted by permission, Deming Zhou, Lawrence C. Leung, and William P. Pierskalla, "Inventory Management of Platelets in Hospitals: Optimal Inventory Policy for Perishable Products with Regular and Optional Expedited Replenishments", Manufacturing & Service Operations Management, Volume (13), Issue 4, Fall 2011, Copyright (2012), the Institute for Operations Research and the Management Sciences, 7240 Parkway Drive, Suite 300, Hanover, Maryland 21076 USA