Limitations of weight restrictions in data envelopment analysis for benchmarking Brazilian electricity distribution system operators

The Brazilian regulator has applied weight restrictions to Data Envelopment Analysis (DEA) for estimating the regulatory expenditures of distribution system operators. An ad-hoc procedure is currently being proposed, using a previous model without weight restrictions to estimate upper and lower boundaries using a data-driven approach. Nevertheless, DEA is subject to multiple solutions that may be achieved with a random switch of the dataset rows. In brief, the proposed methodology is extremely sensitive to multiple solutions. Using a simulation study, we see regulatory operational expenditures may vary close to US$ 42 million, thus compromising the financial integrity of companies.     

基于贪婪算法的旅游路线优化问题

针对目前国内旅游线路的设计多偏向于从景区特色出发,而较少从旅行时间和路径入手的问题,利用贪婪算法设计数学模型。在旅行者不多于15天的旅行约束条件下,对国内201个5A风景区进行聚类分块,将201个景区简化为31个省市。算得从西安市出发到各省市的旅行时间并得到21条符合要求的旅行路线。将相关结果以更直观的图像形式展现,为旅行路线的设计研究提供了参考。     

Error-correction Mechanism Tests for Cointegration in a Single-equation Framework

A new test is proposed for cointegration in a single-equation framework where the regressors are weakly exogenous for the parameters of interest. The test is denoted as an error-correction mechanism (ECM) test and is based upon the ordinary least squares coefficient of the lagged dependent variable in an autoregressive distributed lag model augmented with leads of the regressors. The limit distributions of the standardized coeffi cient and t -ratio versions of the ECM tests are obtained and critical values are provided. These limit distributions do not depend upon nuisance parameters but they depend on the number of regressors. Finally, we compare their power properties with those of other cointegration tests available in the literature and find the circumstances under which the ECM tests have a better performance.     

Optimal leader allocation in UAV formation pairs ensuring cooperation

This paper considers the problem of optimally allocating the leader task between pairs of selfish unmanned aerial vehicles (UAVs) flying in formation. The UAV that follows the other achieves a fuel benefit. The noncooperative nature of the agents makes it necessary to arbitrate leader-allocation mechanisms that induce collaboration so that the fuel consumption benefits of flying in formation can be realized. Formulated as a nonlinear program, our problem poses two distinct challenges: on the one hand, given a fixed number of leader switches, determine the optimal leader allocation and, on the other, find the optimal number of leader switches. Even though the first problem is nonconvex, we identify a suitable restriction of its feasible set that makes it convex while maintaining the same optimal value. Regarding the second problem, our analysis of the optimal value of the problem as a function of the number of switches allows us to design a search algorithm which is guaranteed to find the solution in logarithmic time. Several simulations illustrate our results.     

“不＋形1＋不＋形2”的格式限制和语用特征

在现代汉语中,“不……不……”是一个非常活跃的格式,文章主要从句法、语义、语音等多个角度考察它在表达“恰到好处”这一格式义时所受到的制约。同时也对这一格式的语用特征做了简单描写。     

Which bases admit non-trivial shrinkage of formulae?

We show that the shrinkage exponent, under random restrictions, of formulae over a finite complete basis B of Boolean functions, is strictly greater than 1 if and only if all the functions in B are unate, i.e., monotone increasing or decreasing in each of their variables. As a consequence, we get non-linear lower bounds on the formula complexity of the parity function over any basis composed only of unate functions. Received: June 15, 2000.     

A linear differential game with a fixed termination time and restrictions on resources

A linear game with a fixed termination time and integral restrictions on player controls is considered. The pursuer constructs his control with knowledge of the control of the evader, and the evader uses information on all previous actions of his opponent at each instant of time. Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 178–183, July–August, 2000.     

A systematic procedure to obtain a preferable and robust ranking of units

This paper introduces one systematic procedure for the manager of an organization to assess units under its governance using multiple performance indices. The goal of this systematic procedure is to assist the manager in obtaining a preferable and robust ranking result for units. In this procedure, for all units, one common set of weights attached to the performance indices is determined in order to maximize the group's comprehensive score. Then, using the common set of weights, each unit's comprehensive score is evaluated and compared for ranking. In order to obtain the preferable ranking, the manager's subjective preference is considered and formulated by the virtual weights restrictions while determining the common weights in the procedure. The procedure is applied in order to obtain a robust ranking by modifying the boundary of the feasible region of virtual weights restrictions in each assessment. The final statistical ranking of all assessments provides the manager with one robust ranking, which is invariant in different feasible regions of virtual weights restrictions in the numerical example.     

A SIMPLER METHOD FOR FINDING INDEPENDENT REACTIONS

An improved method of matrix transform is provided for finding independent reactions and independent stoichiometric restrictions of a chemical reaction system. This method can deal with various reaction systems without the difficulties that occurred with the usual methods. Two different restrictive conditions among the components are discussed. It has been emphasized that the concept of extent of independent reaction is not necessary for material balance calculation and may confuse an actual reaction system. Some typical examples illustrate the simplicity and versatility of the new method.