Locating a target from directional data

Statistical estimation plays an important role in locating a target in space, a task that has important applications in many areas. However, theoretical measures on the quality of various estimators reported in the literature have been difficult to obtain because of mathematical complications. As a result, choice of estimator in practice has been largely arbitrary. In this paper, we present a systematic study on major target estimators reported in the literature. Focus is on comparisons between the traditional angle method, the line method, and a recently developed line-to-point transformation method. Insights gained from the study directly lead to the development of a novel two-stage angle method that not only produces highly accurate target estimation among all known estimators but is also computationally efficient. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 353–364, 1998     

A new appointment rule for a single-server,multiple-customer service system

This paper proposes a new appointment rule for the single-server, multiple-customer service system. Unlike previous appointment rules, which perform well only in specific service environments, the new rule can be parameterized to perform well in different service environments. The new appointment rule is presented as a mathematical function of four environmental parameters, namely, the coefficient of variation of the service time, the percentage of customers' no-shows, the number of appointments per service session, and the cost ratio between the server's idle and customers' waiting cost per unit time. Once the values of these environmental parameters are estimated, the new appointment rule can be parameterized to perform well. The results show that new rule performs either as well as or better than existing appointment rules in a wide range of service environments. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 313–326, 1998