A PRODUCTIVITY AND EFFICIENCY ANALYSIS OF THE SECURITY AND DEFENCE TECHNOLOGICAL AND INDUSTRIAL BASE IN SPAIN

This study analyses the performance of the productivity of the main industrial subsectors composing the security and defence technological and industrial base (SDTIB) in Spain from 1996 to 2009. Accordingly, we have used the non-parametric data envelopment analysis and bootstrapping techniques to compute Malmquist productivity indexes that allow us to split productivity growth into efficiency change and technical progress. The results obtained show productivity improvement in the SDTIB as a whole due mainly to advances in technology and to a lesser extent to the contribution of technical efficiency. The bootstrap approach yields further evidence, as for many cases, productivity growth or decline, is not statistically significant. This is the first time a study of this kind has been carried out on the production process of this sector in Spain.     

Rent‐seeking models of international competition: An experimental investigation*

This paper experimentally tests a number of hypotheses that follow from models of international competition that are based on Tullock style rent‐seeking models. Specifically, we designed and performed experiments to see how variations in the degree of publicness in the prize as well as changes in the values assigned to the prize affect alliances in terms of individual nation contributions, total contributions, burden sharing, and the likelihood of winning the prize. While there was substantial variation in individual behavior, the results of the experiments generally conform to the theoretical predictions of the rent‐seeking model of international competition and alliances.     

基于点云配准的室内移动机器人6自由度位姿估计

针对移动机器人在室内环境下难以获取GPS定位信息,仅靠自身惯导不能得到精确位姿的问题,提出了一种基于RGB-D传感器获取三维环境点云,对连续点云提取特征并进行配准的移动机器人6自由度位姿估计方法.首先通过RGB-D传感器获取环境深度图像,根据特征提取算法提取点云特征;然后以特征点为配准点,运用随机一致性采样(RANdom SAmple Consensus,RANSAC)算法对点云进行初配准,剔除部分错误匹配点,获得初始变换矩阵;最后采用改进的迭代最近点(Iterative Closet Point,ICP)算法进行精配准,获得点云间的最终变换矩阵,实现位姿估计.实验结果表明:该方法有效地提高了大规模点云配准效率,得到了较精确的位姿估计信息.     

Improved bounds for batch scheduling with nonidentical job sizes

Here, we revisit the bounded batch scheduling problem with nonidentical job sizes on single and parallel identical machines, with the objective of minimizing the makespan. For the single machine case, we present an algorithm which calls an online algorithm (chosen arbitrarily) for the one‐dimensional bin‐packing problem as a sub‐procedure, and prove that its worst‐case ratio is the same as the absolute performance ratio of . Hence, there exists an algorithm with worst‐case ratio , which is better than any known upper bound on this problem. For the parallel machines case, we prove that there does not exist any polynomial‐time algorithm with worst‐case ratio smaller than 2 unless P = NP, even if all jobs have unit processing time. Then we present an algorithm with worst‐case ratio arbitrarily close to 2. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 351–358, 2014     

End effects in capacity expansion models with finite horizons

Capacity expansion models are typically formulated in the context of some finite horizon. Because the firm lasts longer than the horizon, a bias can enter into the optimal solution from the model horizon chosen. Recently, Grinold [8] has proposed a “dual-equilibrium method” for ameliorating possible distortions. Although the dual-equilibrium method has superior analytical properties to other methods, it is conceptually more complex. In this paper it is shown that there are situations where the “primal-equilibrium” approach of Manne [15] provides equivalent results and that the use of annualized capital costs in the objective function, although somewhat less efficient, results in a similar model.     

Quality control and the sales process

Product quality is emerging as a major strategic instrument for competition. The purpose of this article is to assess the effects of quality control on sales, and, vice versa, the effects of the sales process on quality control. A model relating quality control and the sales process (advertising, repeat purchase, and word-of-mouth effects) is developed to evaluate the above relationships. Two special cases, with degenerate and beta distribution for defect items in the production lot, are analyzed in detail. In the former case, analytical results for the optimal quality control schemes are obtained, whereas in the latter, efficient bounds are derived to search for the optimal scheme. It is shown, analytically and numerically, that the sales parameters have significant impact on whether more “stringent” or “tighter” quality control is warranted. Future research directions are also discussed.