Stacy D. Hill

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A fixed gain version of the SPSA (simultaneous perturbation stochastic approximation) method for function minimization is developed and the error process is characterized. The new procedure is applicable to optimization problems over Z, the grid of points in R with integer components. Simulation results and a closely related application, a resource(More)
Air traffic delay is a growing and expensive problem. We investigated ways to reduce the cost and magnitude of such delays by trading gate delays against more expensive air delays. Air management and planning at this level can be facilitated by simulation, especially for strategies that alter controls on the system. We used the SIMMOD air traffic simulation(More)
We consider the problem of optimizing a transit network with respect to customer service, when simulation of the network is necessary to accurately characterize performance. In particular, we consider the transfer optimization problem, where the goal is to minimize the total expected waiting time of riders by coordinating transfers in the network. We apply(More)
The in vitro antimicrobial and cytotoxic concentrations of glutaraldehyde and formocresol were determined. Minimal antimicrobial concentrations of these two agents against selected microbial flora reported in carious primary teeth were 3.125% for glutaraldehyde and 0.75% for formocresol. At a doubling of these concentrations, most organisms, except Candida(More)
A stochastic approximation method for optimizing a class of discrete functions is considered. The procedure is a version of the Simultaneous Perturbation Stochastic Approximation (SPSA) method that has been modified to obtain a stochastic optimization method for cost functions defined on a grid of points in Euclidean p-space having integer components. We(More)
This paper establishes a framework for formal comparisons of several leading optimization algorithms, establishing guidance to practitioners for when to use or not use a particular method. The focus in this paper is five general algorithm forms: random search, simultaneous perturbation stochastic approximation, simulated annealing, evolutionary strategies,(More)
The cost of delay is a serious and increasing problem in the airline industry. Air travel is increasing, and already domestic airports incur thousands of hours of delay daily, costing the industry $2 billion a year. One strategy for reducing total delay costs is to hold planes for a short time at the gate in order to reduce costly airborne congestion. In a(More)
Stochastic approximation is a simulation optimization technique that has received much attention recently. Traditional finite difference-based stochastic approximation schemes require a large number of simulations when the number of parameters of interest is large. We apply simultaneous perturbation stochastic approximation (S PSA), which requires only two(More)
We consider the use of a fixed gain version of SPSA (simultaneous perturbation stochastic approximation) for optimizing a class of discrete functions. The procedure has been modified to obtain an optimization method that is applicable to cost functions defined on a grid of points in Euclidean p-space having integer components. We discuss some related(More)