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Benchmarking plays a central role in the regulatory scene. Regulators set tariffs according to a performance standard and, if the companies can outperform such a standard, they can retain the gains observed by such outperformance. Efficiency performance is usually assessed by comparison (or a benchmark) against either other companies or the company's own historical performance. This paper discusses the impact of environmental variables on the efficiency performance of electricity distribution companies. Indeed, such variables, which are argued to be unmanageable, may affect the electricity utilities' performance. Thus, this paper proposes a simulation methodology based on design of experiment philosophy for statistically testing environmental variables and the interactions among them, enabling regulators to build the best suited semi-parametric two-stage model of electricity utility benchmarking analysis. To demonstrate the power of the proposed approach, experimental simulations are carried out using real data published by Brazil's regulator. The results show that environmental variables may impact efficiency performance linearly and nonlinearly.

A alta reprovacao em disciplina introdutoria de programacao para estudantes nao ligados a area de computacao levou um grupo de professores a adotar uma metodologia hibrida de ensino. Ela mesclava aulas presenciais com atividades baseadas em um juiz online desenvolvido por um dos autores. A ferramenta possibilitou que os estudantes praticassem mais exercicios de programacao, com feedback imediato, proporcionando um aumento na taxa de aprovacao. A percepcao dos alunos, de forma geral positiva, tambem foi analisada, por meio do Metodo de Explicitacao do Discurso Subjacente.

This paper presents the friendship and selfishness forwarding (FSF) algorithm for Delay Tolerant Networks. This novel solution is based on two social characteristics of nodes: friendship and selfishness. When a contact opportunity arises, FSF analyzes two aspects to make message forwarding decisions: first, FSF assesses the friendship strength among the pair of nodes, then it determines the individual selfishness of the relay node. Unlike other algorithms proposed in the DTN literature, we use a machine learning algorithm to quantify the friendship strength among pairs of nodes in the network. The individual selfishness of the relay node is determined by using a model based on the current level of its resources. The primary goal is to take into account the case where, despite a strong friendship with the message destination, the relay node does not accept processing the message to save its resources. By using trace-driven simulations we show that the FSF algorithm achieves better results in terms of delivery rate, average cost and efficiency.

This paper discusses, in terms of Brazil's situation, the use of a nonlinear pricing approach in the application of a two-part tariff to electricity distribution networks. The principles that uphold charging access and usage are to optimize energy systems that are based on a generation technology mix. Such a pricing approach is used in Brazil, where the generation mix is mainly hydro-generation. This study shows that, in a case like Brazil's, a two-part tariff may be used as a tool for network optimization. The paper presents a design for a two-part tariff for a distribution system with varying consumer behavior. To validate the discussion, we offer a numerical example. Finally, remarks are given concerning pricing access and usage for low voltage level consumers.

Certain kinds of delay and disruption tolerant networks need the human support to send data between users without a contemporaneous end-to-end path between them. However, humans are socially selfish and tend to cooperate with whom they have a social relationship, fact that affects the overall performance. Memory space is a critical resource on mobile devices, and since the intermediate nodes have to store the messages, buffer management strategy becomes a crucial factor to achieve a satisfactory network performance. Very little attention has been directed towards applying the social characteristics of the users to mitigate the congestion in DTN. This paper presents a buffer management strategy for DTNs that takes into account a value associated with the social relationship strength among the users. We evaluated this policy in conjunction with the Epidemic and PRoPHET routing algorithms. By means of a thoroughly planned set of steady-state simulation experiments, we found that the proposed scheme can increase the delivery rate besides decreasing the average delay.

A aceitabilidade das aplicações Web por seus usuários depende diretamente da usabilidade da aplicação, que pode ser melhorada através da realização de avaliações. Neste artigo, relatamos um caso prático de teste de usabilidade, no qual um serviço de sincronização de dados de navegação entre múltiplos dispositivos, chamado Browserver, é comparado com um serviço de finalidade semelhante. Os resultados desta experiência mostram a possibilidade de realizar testes de usabilidade eficazes com baixo custo.

Header compression techniques can improve the speech quality of VoIP applications. However, its deployment over wireless mesh environments may not offer much improvement, since the wireless and multi-hop characteristics of such a network impose a high packet loss rate. In this work, we propose a new approach for header compression, using packet aggregation to cooperate with the header compression scheme. Simulation results show that the new cooperative approach can decrease significantly the packet loss, impacting positively on the speech quality.

In this paper we evaluate the influence of radio propagation modeling on VoIP quality in wireless network simulations. How propagation modeling can influence classification of strategies concerned in improving VoIP quality? We analyze reactive AODV and proactive OLSR approaches in a simulated 802.11 mesh backbone and calculate the VoIP quality by means of a reviewed version of ITU-TE-Model. Results showed that: a) irrespective of routing strategy, different propagation model configurations can influence speech quality in such a way that it switches from "acceptable" to "unacceptable", b) the classification of such strategies can be highly influenced by propagation models as well as its configurations.

In this paper we propose a VoIP study case to evaluate the impact of different radio propagation models on performance parameters of application layer in simulation studies of Wireless Mesh Backbones. For each presented model, we carried out experiments taking into account the credibility aspects suggested by simulation theory of stochastic processes. Results showed that, for the same scenario, using different propagation models, voice speech quality can switch from acceptable to unacceptable.

In this paper we focus on the following question: how routing protocols, working under different channel conditions, can influence the human perceived quality of VoIP calls in a wireless mesh backbone? In order to respond this question, we propose a study case where we analyze two routing approaches in a 802.11 wireless mesh backbone, namely, reactive AODV and proactive OLSR. We calculated the voice speech quality by making use of a reviewed version of ITU-T E-model proposed in previous work. Results obtained from highly credible stochastic simulation environment, also described in this paper, showed that AODV performs better in very hostile mediums while OLSR presents better results when more friendly mediums take place.