Browsing by Author "Russell King, Committee Member"

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    Development and Experimental Evaluation of a Novel Annuloplasty Ring with a Shape Memory Alloy Core
    (2009-04-27) Purser, Molly Ferris; Dr. Denis Cormier, Committee Co-Chair; Dr. Gregory Buckner, Committee Co-Chair; Dr. Ola Harrysson, Committee Member; Russell King, Committee Member
    A novel annuloplasty ring with a shape memory alloy core has been developed to facilitate minimally invasive mitral valve repair. In its activated (Austenitic) phase, this prototype ring provides comparable mechanical properties as commercial semi-rigid rings. In its pre-activated (Martensitic) phase, this ring is flexible enough to be introduced through an 8 mm trocar and easily manipulated with robotic instruments within the confines of a left atrial model. The core is constructed of 0.508 mm diameter NiTi, which is maintained below its Ms temperature (24 °C) during deployment and suturing. After suturing, the stiffener is heated above its Af temperature (37 °C, slightly below normal human body temperature) enabling the NiTi to retain its optimal geometry and stiffness characteristics indefinitely. The NiTi core is shape set in a furnace to the appropriate size and optimal geometry during fabrication. The ring is cooled in a saline bath prior to surgery, making it compliant and easy to manipulate. Evaluation of the ring included mechanical testing, robotic evaluation, static pressure testing, dynamic flow testing and fatigue testing. Experimental results suggest that the NiTi core ring could be a viable alternative to flexible bands in robot-assisted mitral valve repair.
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    Pack Optimization Problem: Models and Solution Methods.
    (2010-10-29) Wang, Pu; Shu Fang, Committee Chair; Salah Elmaghraby, Committee Member; Russell King, Committee Member; Matthias Stallmann, Committee Member; Douglas Irving, Committee Member
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    Performance Model for a Public Logistics Network
    (2009-01-07) Xiang, Ling; Michael Kay, Committee Chair; Tao Pang, Committee Member; James Wilson, Committee Member; Russell King, Committee Member
    A public logistics network (PLN) has been proposed as an alternative to private networks for the ground transport of parcels. In this dissertation, a heuristic approach to approximate the package average waiting time in a PLN is presented; and then based on this waiting time approximation, a PLN design procedure is developed. A PLN can be viewed as a priority queuing network with bulk arrivals and bulk service. It is difficult to obtain a closed-form solution for package average waiting time in a PLN. The problem is reformulated so that trucks transport loads instead of individual packages, thereby relaxing the bulk arrivals and bulk service feature. The package average waiting time is approximated fairly accurately by Kingman’s equation when the server utilization is high. A simulation model is created to determine the parameters needed in Kingman’s equation (the coefficient of variation for package interarrival times and for truck interarrival times). A regression analysis of the results shows that the headway ratio is around 5.5. The package average waiting time is approximated by the product of the truck headway (truck average interarrival time) and the headway ratio. The PLN simulation with protocols and the package bidding process is discussed as an extension to the basic simulation model. Packages bid for their trips along the way. The highest bidder gets the highest priority for truck transport services. Results from a simulation model incorporating a series of protocols developed by Kay show that a PLN with these protocols performs better than a FIFO system. For the PLN design problem, the goal is to design a PLN that results in the minimal package average waiting time for the entire network. Potential locations (search space) for the distribution centers (DCs) are found using the U.S. network of interstate and highways. A genetic algorithm (GA) was applied to search for the optimal number of DCs, their locations, and direct arc connections between each pair of DCs.
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    The Simulation Start-up Problem: Performance Comparison of N-Skart and MSER-5
    (2010-06-18) Mokashi, Anup; James Wilson, Committee Chair; Peter Bloomfield, Committee Member; Russell King, Committee Member
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    A Two-Agent Stochastic Alert Threshold Model for Identifying a Potential Disease Outbreak: A Case Study for H1N1.
    (2010-11-03) Yaylali, Emine; Julie Ivy, Committee Chair; Reha Uzsoy, Committee Member; Russell King, Committee Member
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    Two-person Investment Game.
    (2010-04-29) Li, Lan; Shu Fang, Committee Chair; Russell King, Committee Member; Ivan Kandilov, Committee Member; Yahya Fathi, Committee Member; Simon Hsiang, Committee Member