Testing or fault-finding for reliability growth: A missile destructive-test example

A new piece of equipment has been purchased in a lot of size m. Some of the items can be used in destructive testing before the item is put into use. Testing uncovers faults which can be removed from the remaining pieces of equipment in the lot. If t < m pieces of equipment are tested, then those that remain, m₁ = m − t, have reduced fault incidence and are more reliable than initially, but m₁ may be too small to be useful, or than is desirable. In this paper models are studied to address this question: given the lot size m, how to optimize by choice of t the effectiveness of the pieces of equipment remaining after the test. The models used are simplistic and illustrative; they can be straightforwardly improved. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 623–637, 1997     

Keeping David From Bathsheba: The Four-Star General’s Staff as Nathan

Readers of reports on ethical failures by four-star general officers must wonder, “Don’t they have staffs to ensure that the general follows ethics rules?” The Department of Defense publishes robust ethics guidance in several documents; however, a staff’s best efforts to implement this guidance may fail to make an impression on a senior leader who is susceptible to the “Bathsheba syndrome,” an allusion to the biblical account where the prophet Nathan rebuked King David for his moral failings. This paper proposes a methodology to enable senior headquarters staffs to play the role of Nathan in supporting ethical behaviors by high-level officers. It examines the mechanisms that embed ethical behavior within members of those staffs in carrying out their three principal roles of advising, scheduling, and transporting the four-star officer. The authors offer a framework based on an ethical infrastructure of organizational climate that focuses the staff’s daily efforts to mitigate risk across seven ethical “danger areas” that threaten ethical failures by senior officers.     

An extreme-point approach for obtaining weighted ratings in qualitative multicriteria decision making

Many attempts have been made in the past to obtain estimates for the weights and ratings values of a multicriteria linear utility function. In particular, the problem arises when both criteria importance and alternatives' ratings are expressed in a qualitative ordinal manner. This article proposes an extreme-point approach for obtaining the overall ratings in the presence of ordinal preferences both for the criteria importance and the alternatives' rankings. In particular it is shown that Borda's method of scores is obtained as a special case. © 1996 John Wiley & Sons, Inc.     

On the orbit characteristics of the M/G/ 1 retrial queue

In teletraffic applications of retrial queues only the service zone is observable. Another part of a retrial queue, the orbit, which represents the delay before repeated attempts to get service, cannot be observed. Thus, it is very important to get general results about behavior of the orbit. We investigate two characteristics of the orbit, namely, the orbit busy period and the orbit idle period, which seem to be very useful from this point of view. © 1996 John Wiley & Sons, Inc.     

A robust regression technique using compound estimation

Least squares fitting of regression models is a widely used technique. The presence of outliers in the data can have an adverse effect on the method of least squares, resulting in a model that does not adequately fit to the bulk of the data. For this situation, robust regression techniques have been proposed as an improvement to the method of least squares. We propose a robust regression procedure that performs well relative to the current robust methods against a variety of dataset types. Evaluations are performed using datasets without outliers (testing efficiency), with a large percentage of outliers (testing breakdown), and with high leverage outliers (testing bounded influence). The datasets are based on 2-level factorial designs that include axial points to evaluate leverage effects. A Monte Carlo simulation approach is used to evaluate the estimating capability of the proposed procedure relative to several competing methods. We also provide an application to estimating costs for government satellites. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 125–139, 1998     

A robust policy for serial agile production systems

One of the major problems in modeling production systems is how to treat the job arrival process. Restrictive assumptions such as Markovian arrivals do not represent real world systems, especially if the arrival process is generated by job departures from upstream workstations. Under these circumstances, cost‐effective policies that are robust with respect to the nature of the arrival process become of interest. In this paper, we focus on minimizing the expected total holding and setup costs in a two‐stage produce‐to‐order production system operated by a cross‐trained worker. We will show that if setup times are insignificant in comparison with processing times, then near‐optimal policies can be generated with very robust performances with respect to the arrival process. We also present conditions under which these near‐optimal policies can be obtained by using only the arrival and service rates. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005.