Robustness in operational research and decision aiding: A multi-faceted issue

In Introduction, I explain the meaning I give to the qualifier term ”robust” and justify my preference for the expression robustness concern rather than robustness analysis, which I feel is likely to be interpreted too narrowly. In Section 2, I discuss this concern in more details and I try to clarify the numerous raisons d’être of this concern. As a means of examining the multiple facets of robustness concern more comprehensively, I explore the existing research about robustness, attempting to highlight what I see as the three different territories covered by these studies (Section 3). In Section 4, I refer to these territories to illustrate how responses to robustness concern could be even more varied than they currently are. In this perspective, I propose in Section 5 three new measures of robustness. In the last section, I identify several aspects of the problem that should be examined more closely because they could lead to new avenues of research, which could in turn yield new and innovative responses.     

A flexible approach to ranking with an application to MBA Programs

We develop a model for flexibly ranking multi-dimensional alternatives/units into preference classes via Mixed Integer Programming. We consider a linear aggregation model, but allow the criterion weights to vary within pre-specified ranges. This allows the individual alternatives/units to play to their strengths. We illustrate the use of the model by considering the Financial Times Global MBA Program rankings and discuss the implications. We argue that in many applications neither the data nor the weights or the aggregation model itself is precise enough to warrant a complete ranking, providing an argument for sorting or what we call flexible ranking.     

Multivariate optimisation for procurement of emergency services equipment – Teams of the best or the best of teams?

It is shown that the design of some inventory structures such as critical protective items for local emergency response elements, or selection of some types of sports team (e.g. baseball, cricket), is appropriately formulated as the selection of an optimal set of options over multiple criteria. This paper examines the problem of defining what might constitute optimum sets under such conditions. Noting that options may be characterised with data of various scale types, the paper introduces a number of different policies for optimality appropriate to the different scale types, and derives closed expressions that implement the various policies. It is shown that simply choosing the best individual options to construct a preferred team is likely to be sub-optimal particularly if the policy is hard to meet. This result is shown to be robust over data structures and data scale types. Managerial implications are briefly considered.     

ACUTA: A novel method for eliciting additive value functions on the basis of holistic preference statements

In multiple criteria decision aiding, it is common to use methods that are capable of automatically extracting a decision or evaluation model from partial information provided by the decision maker about a preference structure. In general, there is more than one possible model, leading to an indetermination which is dealt with sometimes arbitrarily in existing methods. This paper aims at filling this theoretical gap: we present a novel method, based on the computation of the analytic center of a polyhedron, for the selection of additive value functions that are compatible with holistic assessments of preferences. We demonstrate the most important characteristics of this technique with an experimental and comparative study of several existing methods belonging to the UTA family.     

闭极大线性子空间正交补的判别及应用

继续前面的工作,证得对于赋范线性空间中固定线性子空间成为迫近子空间的充分必要条件.特别的,对于闭极大线性子空间来说,的迫近性等价于的正交可补性.做为其直接推论,给出Banach空间成为自反空间的5个等价条件,其中4个条件为经典结果,一个条件为已有文献中给出的条件,但给出全新的证明.     

φ-free n-Lie代数的判定

对φ-free n-Lie代数的判别条件作了探讨,得到了由n-Lie代数的幂零根基表示的充要条件,并对φ-free n-Lie代数的性质作了研究.     

线性中立型单延迟系统李代数稳定性判据

研究了线性中立型单延迟微分系统的稳定性.从矩阵李代数可解性角度,推导出新的简单的延迟独立稳定性判据.该新判据的重要意义和优越性在于首次突破了以往大多数相关文献的稳定性判据在应用上受条件‖C‖<1,ρ(|C|)<1或ρ(|N|)<1的限制,从而首次成功确定了在‖C‖≥,ρ(|C|)≥1和ρ(|N|)≥1的情形下中立型延迟微分系统渐近稳定性.最后,通过两个例子显示了新判据的优越性.     

Selection of adequate optimization criteria in chromatographic separations

Computer-assisted optimization of chromatographic separations is still a fruitful activity. In fact, advances in computerized data handling should make the application of systematic optimization strategies much easier. However, in most contemporary applications, the optimization criterion is not considered to be a key issue (Vanbel, J Pharm Biomed, 21:603–610, 1999). In this paper, an update of the importance of selecting adequate criteria in chromatographic separation is presented.     

Dynamic stability of nonlinear barge-towing system

A method for predicting the dynamic stability of a nonlinear barge-towing system is presented in which the equations of motion of the dynamic system are first transformed into a six-dimensional state-space equation. The governing equation is then linearized by using the Taylor series expanding with respect to the equilibrium configurations of the towed barge. It is found that the stability conditions of a towing system are determined by the signs of the real part of some associated eigenvalues: Positive and negative 1's will result in unstable and stable dynamic responses, respectively, and 0 corresponds to the marginally stable condition. The reliability of the foregoing criteria is confirmed by the time histories (simulations) of the nonlinear barge-towing system. The effects of the stabilizing skegs and significantly improve the course stability of the towed barge and that the length and material of the towrope are also key factors affecting the dynamic stability of the barge-towing system.     

A multicriteria DSS for stock evaluation using fundamental analysis

The paper describes a multicriteria decision support system which aims at presenting an evaluation of the Athens Stock Exchange (ASE) stocks, on the basis of fundamental analysis. The system evaluates the stocks based on the method of fundamental analysis ratios, which is the most appropriate evaluation approach regarding investment decisions within a long term horizon. In addition to quantitative data deriving from fundamental analysis, the system uses qualitative data as well, in order to improve the reliability of the evaluation. The system introduced in this paper, utilises multicriteria analysis methodologies in order to rank the stocks by placing the best stock first and the worst last. Stock evaluation considers the specific characteristics of the potential investor, as well as his attitude towards undertaken risk. The final output of the system is four stock rankings which respond to four different criteria groups, depending on the type of accounting plan each listed company belongs to. The system incorporates a large volume of relevant information and operates in ‘real world conditions’ since its data are constantly updated. Finally, the system is intended for both institutional and private investors.