ORiON - latest Issue
Volume 32, Issue 1, 2016
Author Stephan VisagieSource: ORiON 32, pp i –ii (2016)More Less
This first issue of ORiON volume 32 contains three papers. As usual, the papers are from diverse branches in operations research - both in terms of theory and application. In terms of application the papers stems from the military, logistics and finance. I am sure this issue will contain something of interest to most readers.
Source: ORiON 32, pp 1 –22 (2016) http://dx.doi.org/http://dx.doi.org/10.5784/32-1-522More Less
In a military surface-based air defence environment, a fire control officer typically employs a computerised weapon assignment decision support subsystem to aid him in the assignment of available surface-based weapon systems to engage aerial threats in an attempt to protect defended surface assets - a problem known in the military operations research literature as the weapon assignment problem. In this paper, a tri-objective, dynamic weapon assignment model is proposed by modelling the weapon assignment problem as a multi-objective variation of the celebrated vehicle routing problem with time windows. A multi-objective, evolutionary metaheuristic for solving the vehicle routing problem with time windows is used to solve the model. The workability of this modelling approach is illustrated by solving the model in the context of a simulated, surface-based air defence scenario.
Source: ORiON 32, pp 23 –53 (2016) http://dx.doi.org/http://dx.doi.org/10.5784/32-1-528More Less
In this article, a service facility inventory system with server interruptions and a finite number of sources are considered. The inventory is replenished according to (s; S) ordering policy. Using the matrix methods, the stationary distribution of the stock level, server status and waiting area level is obtained in the steady state case. The Laplace-Stieltjes transform of the waiting time of the tagged customer is derived. Many impartment system performance measures are derived and the total expected cost rate is computed under a suitable cost structure. The results are illustrated numerically.
Source: ORiON 32, pp 55 –78 (2016) http://dx.doi.org/http://dx.doi.org/10.5784/32-1-541More Less
Portfolios and indices that have been specifically constructed to have low risk attributes have received increasing interest in the recent international literature. It has been found that portfolios constructed by targeting low risk assets have predominantly outperformed portfolios constructed to have higher risks. This anomaly has led to renewed interest in constructing low volatility portfolios by practitioners. This study analyses a variety of low volatility portfolio construction methodologies using sectors as building blocks in the South African environment. The empirical results from back-testing these portfolios show significant promise in the South African setting when compared with a market capitalization-weighted benchmark. In the empirical analysis in the South African environment two techniques stand out as being superior low volatility construction techniques amongst the seven techniques assessed. Furthermore, the low volatility portfolios are blended with typical general equity portfolios (using the Shareholder-Weighted Index (SWIX) as a proxy). It was found that these blended portfolios have useful features which lead to enhanced performance and therefore can serve as effective portfolio strategies.