Estimating Self-Sustainability in Peer-to-Peer Swarming Systems

Peer-to-peer swarming is one of the \emph{de facto} solutions for distributed content dissemination in today's Internet. By leveraging resources provided by clients, swarming systems reduce the load on and costs to publishers. However, there is a limit to how much cost savings can be gained from swarming; for example, for unpopular content peers will always depend on the publisher in order to complete their downloads. In this paper, we investigate this dependence. For this purpose, we propose a new metric, namely \emph{swarm self-sustainability}. A swarm is referred to as self-sustaining if all its blocks are collectively held by peers; the self-sustainability of a swarm is the fraction of time in which the swarm is self-sustaining. We pose the following question: how does the self-sustainability of a swarm vary as a function of content popularity, the service capacity of the users, and the size of the file? We present a model to answer the posed question. We then propose efficient solution methods to compute self-sustainability. The accuracy of our estimates is validated against simulation. Finally, we also provide closed-form expressions for the fraction of time that a given number of blocks is collectively held by peers.Comment: 27 pages, 5 figure

Controle biológico aplicado e natural da lagarta-do-cartucho do milho.

bitstream/item/44201/1/controle-biologico-lagarta.pd

Avaliação da presença de metais pesados em nove méis produzidos e comercializados no Distrito Federal.

Resumo: O mel brasileiro é produzido principalmente por abelhas africanizadas a partir do néctar ou da secreção das plantas e, devido às suas características genéticas dessas espécies de abelhas, dispensa o uso de antibióticos e pesticidas, como acaricidas e fungicidas. A composição das amostras de méis está intimamente relacionada com o tipo de florada utilizada por estas abelhas para a elaboração do produto final. Um dos componentes de grande importância são os minerais presentes no mel que representam de 0,02% a 1%. Dentre estes minerais observamos os chamados metais pesados, que podem indicar tanto a origem geográfica do mel quanto o nível de poluição ambiental por estes metais. Logo, faz-se necessário a pesquisa da presença ou não de metais pesados nas amostras comercializadas. Por isso, o objetivo deste trabalho foi analisar nove amostras provenientes de nove apiários localizados na região do Distrito Federal, quanto à presença de metais de Cádmio, Chumbo, Cobre, Cromo, Níquel e Zinco. As determinações foram realizadas por espectrometria de emissão atômica com plasma acoplado e os resultados demonstraram que as concentrações de Cádmio e Zinco estão em conformidade com a legislação vigente. As concentrações dos demais metais (Chumbo, Cobre, Cromo e Níquel) estão abaixo do limite de detecção. [Evaluation of the presence of heavy metals in nine honeys produced and marketed in the Federal District]. Abstract: The Brazilian honey is mainly produced by Africanized bees that due to their genetic characteristics dispense the use of antibiotics and pesticides, acaricides and fungicides. However, it is necessary to investigate the presence or absence of heavy metals in marketed samples. Therefore, the aim of this study was to analyze nine samples from nine apiaries located in the Federal District, as the presence of metals Cadmium, Lead, Copper, Chromium, Nickel and Zinc. The determinations were performed by atomic emission spectrometry with inductively coupled plasma and the results showed that the concentrations of Cadmium and Zinc are in accordance with current legislation. The concentrations of other metals (Lead, Copper, Chromium and Nickel) are below the detection limit

Controle biológico da broca-da-cana-de-açúcar.

bitstream/item/44196/1/broca-cana.pd

Controlling the operating conditions in an Operating Room

In this paper, we describe the development of a module capable of controlling environmental conditions, personnel movement and management of other important parameters for an operating room (OR) or surgery block. The base of assembly uses a real-life small scale model trying to simulate the systematic functionality of an OR as well as its crucial components. These include the regulation of environmental parameters, logging of entries and exits by the staff, management of pharmaceutical drugs and diseases, and the statistical analysis of several acquired data. The project integrates different types of technologies, such as the microcontroller Arduino, a bidirectional communication interface between this device and a computer, a web based user interface for dynamic interaction, as well as database concepts for data management.N/

Calcium urinary excretion in dairy cows with different levels of glucose tolerance.

O objetivo deste estudo foi avaliar a excreção urinária de Ca durante o periparto em vacas leiteiras com diferentes níveis de tolerância à glicose durante o período de pré-parto