Madiagne Diallo

The Cost Efficiency of the Brazilian Electricity Distribution Utilities: A Comparison of Bayesian SFA and DEA Models

The purpose of this study is to evaluate the efficiency indices for 60 Brazilian electricity distribution utilities. These scores are obtained by DEA (Data Envelopment Analysis) and Bayesian Stochastic Frontier Analysis models, two techniques that can reduce the information asymmetry and improve the regulators skill to compare the performance of the utilities, a fundamental aspect in incentive regulation schemes. In addition, this paper also addresses the problem of identifying outliers and influential observations in deterministic nonparametric DEA models.

Revisiting parametric multi-terminal problems: Maximum flows, minimum cuts and cut-tree computations

Given an undirected network, the multi-terminal network flows analysis consists in determining the all pairs maximum flow values. In this paper, we consider an undirected network in which some edge capacities are allowed to vary and we analyze the impact of such variations on the all pairs maximum flow values. We first provide an efficient algorithm for the single parametric capacity case, and then propose a generalization to the case of multiple parametric capacities. Moreover, we provide a study on Gomory-Hu cut-tree relationships.

Generalized Parametric Multi-terminal Flows Problem

Given an undirected edge-weighted n-nodes network in which a single edge-capacity is allowed to vary, Elmaghraby studied the sensitivity analysis of the multi-terminal network flows. The procedure he proposed requires the computation of as many Gomory-Hu cut trees as the number of critical capacities of the edge, leading to a pseudo-polynomial algorithm.

Impact of a varying capacity on the all pairs 2-route network flows

Given an undirected edge-weighted network in which one edge capacity is allowed to vary, we propose in this paper a polynomial algorithm that needs only two 2-cut-trees computations to provide the all pairs maximum 2-route flow values.

Artificial DMUs and Contingent Weight Restrictions for the Analysis of Brazilian Retail Banks Efficiency

In this paper, we deal with the BCC-I model in Data Envelopment Analysis comparing results of Artificial DMUs and the adjusted Contingent Weight Restrictions approach in the analysis of Brazilian Retail Banks efficiencies. The number of employees, fixed assets, leverage and delinquency rate were considered as inputs, and the financial intermediation results and the equities profitability as outputs. While the Contingent Weight Restrictions method makes only directed weight restrictions, Artificial DMUs method simulates a set of weight restrictions and depends on the use of specialists’ opinions. The compared methods are relevant to increase the precision of the market analysis. The results of both methods are compared in order to distinguish their advantages and inconveniences. A set of efficient banks is obtained together with a market analysis.

COMPUTING MAX FLOWS THROUGH CUT NODES

In this work, the presence of cut nodes in a network is exploited to propose a competitive method for the multi-terminal maximum flow problem. The main idea of the method is based on the relation between cut-trees and cut nodes, which is observed in the context of sensitivity analysis on the variation of edges capacities. Computational experiments were conducted with the proposed algorithm, whose results were compared with the ones of Gusfield, for randomly generated and well-known instances of the literature. The numerical results demonstrate the potential of the method for some classes of instances. Moreover, the proposed method was adapted for the single maximum flow problem, but failed to improve existing running times for the very same classes of instances.

Sensitivity analysis on the all pairs q‐route flows in a network

Given an undirected edge-weighted network in which one edge capacity is allowed to vary, we propose in this paper a polynomial algorithm that needs only two 2-cuttrees computations to provide the all pairs maximum 2-route flow values. Moreover, we provide an extension to the case where k edge capacities may vary, and show that 2^k 2-cut-trees computations are necessary in order to determine the all pairs maximum 2-route-flow values. This makes our algorithm polynomial whenever k = O(polylog n).

Detecting flows congesting a target network link

A disk element for a butterfly valve utilizing a flattened disk-like member which typically has diametrically opposed tubular sleeve insert members mounted therein, one of such insert members being noncylindrical. The disk element is comprised of fiber reinforced thermoplastic polymer. Preferably the polymer is poly(arylene sulfide) and the fiber reinforcement is comprised of carbon or glass.