An empirical excursion into the quicksand of vehicle replacement

The rapid increase of physical distribution costs relative to other categories has resulted in a renewed interest in the analysis of transport operations. One of the most common problems is that of vehicle replacement, and in this paper we present an analysis of real data. The methodology is developed paying due regard to the role of quantitative analysis in the decision-making process, and the sort of data which is readily available in most transport departments. A traditional discounted cost model is presented and this is followed by a productivity-based analysis, which is shown to be an improvement. The latter generates optimal solutions and is flexible enough to carry out considerable sensitivity analysis.     

Record values and the geometric distribution

Suppose {X_n, n≥1} is a sequence of independent and identically distributed discrete random variables having the common distribution function F(x). The exact distribution of the n-th record value is given under the assumption that F(x) has the geometric distribution. Various properties of the record values and some new characterizations of the geometric distribution are presented.     

Foundations as investment managers part II: The performance

Foundations divide roughly into two groups in their investment behavior. Most follow an inactive, risk-averse style, focusing on income maximization rather than total return. Another, smaller group of foundations are more activist and aggressive, focusing on total return. This article analyzes the investment performance associated with these different approaches, showing that while a significant number of foundations are performing well, many others lag in their investment returns.     

Bayesian break-point forecasting in parallel time series,with application to university admissions

A regular supply of applicants to Queen's University in Kingston, Ontario is provided by 65 high schools. Each high school can be characterized by a series of grading standards which change from year to year. To aid admissions decisions, it is desirable to forecast the current year's grading standards for all 65 high schools using grading standards estimated from past year's data. We develop and apply a Bayesian break-point time-series model that generates forecasts which involve smoothing across time for each school and smoothing across schools. “Break point” refers to a point in time which divides the past into the “old past” and the “recent past” where the yearly observations in the recent past are exchangeable with the observations in the year to be forecast. We show that this model works fairly well when applied to 11 years of Queen's University data. The model can be applied to other data sets with the parallel time-series structure and short history, and can be extended in several ways to more complicated structures.     

Performance models for unreliable flexible manufacturing systems

This paper deals with the analysis and application of queueing models for single and multi stage flexible manufacturing systems that are subject to resource failure. Exact results are derived for the single stage queueing system. Two approximations are presneted for the multi stage queueing system as a closed network. We validate the approximations by comparing their performance estimates against the exact global balance solution.     

Symbiotic mothers and infantilized only children: A subtype of single-parent family

One single-parent family pattern is the enmeshed mother/onlychild dyad. Women marry to have children, and then divorce, while mother and child live out the reciprocally gratifying symbiotic period. When these mothers hamper offspring moves toward separation-individuation, post-divorce difficulties bring them to treatment. These difficulties are distinct from those found in other single-parent families. Intervention can move mother and child from the prolonged symbiosis. Treatment stresses modification of low maternal selfesteem, and correction of pathogenic maternal behavior. Re-introduction of the father to the system can also free both mother and child for further growth.