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  <title><![CDATA[PhD Defense by Chenxi Zeng]]></title>
  <body><![CDATA[<p>Student: <strong>Chenxi Zeng</strong></p><p>&nbsp;</p><p>&nbsp;</p><p>Advisor/Chairperson: Prof. Chelsea C. White III</p><p>&nbsp;</p><p>Committee Members: Prof. Turgay Ayer (ISYE), Prof. Alan Erera (ISYE), Prof. Julie Swann (ISYE) and Prof. David A. Bader (CSE)</p><p>&nbsp;</p><p>Thesis Title:<strong> A MINIMUM COST AND RISK MITIGATION APPROACH FOR BLOOD COLLECTION</strong></p><p>&nbsp;</p><p>Date/Time/Location: July 14 2015, 11am-2pm, Groseclose Building, Rm 402</p><p>&nbsp;</p><p>Abstract:</p><p>fac&nbsp; Due to the limited supply and perishable nature of blood products, effective man-<br /> agement of blood collection is critical for high quality healthcare delivery. Whole<br /> blood is typically collected over a 6 to 8 hour collection window from volunteer donors<br /> at sites, e.g., schools, universities, churches, companies, that are a significant distance<br /> from the blood products processing facility and then transported from collection site<br /> to processing facility by a blood mobile.<br /> <br /> The length of time between collecting whole blood and processing it into cryo-<br /> precipitate ("cryo"), a critical blood product for controlling massive hemorrhaging,<br /> cannot take longer than 8 hours (the 8 hour collection to completion constraint),<br /> while the collection to completion constraint for other blood products is 24 hours. In<br /> order to meet the collection to completion constraint for cryo, it is often necessary<br /> to have a "mid-drive collection"; i.e., for a vehicle other than the blood mobile to<br /> pickup and transport, at extra cost, whole blood units collected during early in the<br /> collection window to the processing facility.<br /> <br /> In this dissertation, we develop Markov decision process (MDP) models to: (1)<br /> analyze which collection sites should be designated as cryo collection sites to mini-<br /> mize total collection costs while satisfying the collection to completion constraint and<br /> meeting the weekly production target (the non-split case), (2) analyze the impact of<br /> changing the current process to allow collection windows to be split into two intervals<br /> and then determining which intervals should be designated as cryo collection intervals<br /> (the split case), (3) use several methods to insure that the weekly production target<br /> is met, and then build a decision support tool to provide operational decision support<br /> to plan collection schedules.<br /> <br /> These problems lead to MDP models with large state and action spaces and con-<br /> straints to guarantee that the weekly production target is met with high probability.<br /> These models are computationally intractable for problems having state and action<br /> spaces of realistic cardinality.<br /> <br /> We consider two approaches to guarantee that the weekly production target is met<br /> with high probability: (1) a penalty function approach and (2) a chance constraint<br /> approach. For the MDP with penalty function approach, we ?rst relax a constraint<br /> that signi?cantly reduces the cardinality of the state space and provides a lower bound<br /> on the optimal expected weekly cost of collecting whole blood for cryo while satisfying<br /> the collection to completion constraint. We then present an action elimination proce-<br /> dure that coupled with the constraint relaxation leads to a computationally tractable<br /> lower bound. We then develop several heuristics that generate sub-optimal policies<br /> and provide an analytical description of the difference between the upper and lower<br /> bounds in order to determine the quality of the heuristics.<br /> <br /> For the multiple decision epoch MDP model with chance constraint approach, we<br /> first note by example that a straightforward application of dynamic programming can<br /> lead to a sub-optimal policy. We then restrict the model to a single decision epoch.<br /> We then use a computationally tractable rolling horizon procedure for policy deter-<br /> mination. We also present a simple greedy heuristic (another rolling horizon decision<br /> making procedure) based on ranking the collection intervals by mid-drive pickup cost<br /> per unit of expected cryo collected, which results in a competitive sub-optimal solu-<br /> tion and leads to the development of a practical decision support tool (DST). Using<br /> real data from the American Red Cross (ARC), we estimate that this DST reduces<br /> total cost by about 30% for the non-split case and 70% for the split case, compared<br /> to the current practice. Initial implementation of the DST at the ARC Southern<br /> regional manufacturing and service center supports our estimates and indicates the<br /> potential for significant improvement in current practice.</p><p>&nbsp;</p>]]></body>
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