Desempenho de aerogeradores de pequeno porte: simulação do fornecimento de energia elétrica a cargas conectadas à rede pública ou isoladas

The successful in the implementation of wind turbines depends on several factors, including: the wind resource at the installation site, the equipment used, project acquisition and operational costs. In this paper, the production of electricity from two small wind turbines was compared through simulation using the computer software HOMER - a national model of 6kW and an imported one of 5kW. The wind resources in three different cities were considered: Campinas (SP/BR), Cubatão (São Paulo/BR) and Roscoe (Texas/ USA). A wind power system connected to the grid and a wind isolated system - batteries were evaluated. The results showed that the energy cost ($/kWh) is strongly dependent on the windmill characteristics and local wind resource. Regarding the isolated wind system batteries, the full supply guarantee to the simulated electrical load is only achieved with a battery bank with many units and high number of wind turbines, due to the intermittency of wind power.O sucesso na aplicação de aerogeradores depende de vários fatores, dentre os quais: o recurso eólico no local de instalação, os equipamentos utilizados, os custos de aquisição e operacionais do projeto. Neste trabalho, comparou-se a produção de energia elétrica de dois aerogeradores de pequeno porte, sendo um modelo nacional de 6kW e um importado de 5kW, por meio de simulação, utilizando o programa computacional HOMER. O recurso eólico de três cidades diferentes foi considerado: Campinas (SP/BR), Cubatão (SP/BR) e Roscoe (TX/EUA). Um sistema eólico conectado à rede elétrica e um sistema isolado eólico baterias foram avaliados. Os resultados mostraram que o custo da energia ($/kWh) é fortemente dependente das características do aerogerador e do recurso eólico local. Em relação ao sistema isolado eólico - baterias, a garantia de suprimento integral à carga elétrica simulada só é alcançada com um banco de baterias com muitas unidades e alto número de aerogeradores, devido à intermitência da fonte eólica.36228129

Centrality anomalies in complex networks as a result of model over-simplification

Tremendous advances have been made in our understanding of the properties and evolution of complex networks. These advances were initially driven by information-poor empirical networks and theoretical analysis of unweighted and undirected graphs. Recently, information-rich empirical data complex networks supported the development of more sophisticated models that include edge directionality and weight properties, and multiple layers. Many studies still focus on unweighted undirected description of networks, prompting an essential question: how to identify when a model is simpler than it must be? Here, we argue that the presence of centrality anomalies in complex networks is a result of model over-simplification. Specifically, we investigate the well-known anomaly in betweenness centrality for transportation networks, according to which highly connected nodes are not necessarily the most central. Using a broad class of network models with weights and spatial constraints and four large data sets of transportation networks, we show that the unweighted projection of the structure of these networks can exhibit a significant fraction of anomalous nodes compared to a random null model. However, the weighted projection of these networks, compared with an appropriated null model, significantly reduces the fraction of anomalies observed, suggesting that centrality anomalies are a symptom of model over-simplification. Because lack of information-rich data is a common challenge when dealing with complex networks and can cause anomalies that misestimate the role of nodes in the system, we argue that sufficiently sophisticated models be used when anomalies are detected.Comment: 14 pages, including 9 figures. APS style. Accepted for publication in New Journal of Physic

VCube-PS: A Causal Broadcast Topic-based Publish/Subscribe System

In this work we present VCube-PS, a topic-based Publish/Subscribe system built on the top of a virtual hypercube-like topology. Membership information and published messages are broadcast to subscribers (members) of a topic group over dynamically built spanning trees rooted at the publisher. For a given topic, the delivery of published messages respects the causal order. VCube-PS was implemented on the PeerSim simulator, and experiments are reported including a comparison with the traditional Publish/Subscribe approach that employs a single rooted static spanning-tree for message distribution. Results confirm the efficiency of VCube-PS in terms of scalability, latency, number and size of messages.Comment: Improved text and performance evaluation. Added proof for the algorithms (Section 3.4

REFLEXÕES SOBRE O METABOLISMO BIOSSINTÉTICO DAS PIRETRINAS I E II - REVISÃO E SUGESTÕES

Esta revisão de literatura sobre o metabolismo biossintético das piretrinas I e II sugere várias etapas intermediárias desses processos metabólicos com o intuito de facilitar o entendimento dos inúmeros obstáculos bioquímicos ainda por serem elucidados e compreendidos. Apesar do grande desenvolvimento industrial na fabricação de derivados sintéticos das piretrinas, a exemplo dos piretroides, a alta demanda e importância comercial desses inseticidas continuam a estimular sua biossíntese por intermédio da biotecnologia, do uso de biorreatores, da bioconversão de precursores por enzimas isoladas de folhas e flores dos crisântemos ou, ainda, por micro-organismos geneticamente modificados