7,853 research outputs found
Performance comparison of clustered and replicated information retrieval systems
The amount of information available over the Internet is increasing daily as well as the importance and magnitude of Web search engines. Systems based on a single centralised index present several problems (such as lack of scalability), which lead to the use of distributed information retrieval systems to effectively search for and locate the required information. A distributed retrieval system can be clustered and/or replicated. In this paper, using simulations, we present a detailed performance analysis, both in terms of throughput and response time, of a clustered system compared to a replicated system. In addition, we consider the effect of changes in the query topics over time. We show that the performance obtained for a clustered system does not improve the performance obtained by the best replicated system. Indeed, the main advantage of a clustered system is the reduction of network traffic. However, the use of a switched network eliminates the bottleneck in the network, markedly improving the performance of the replicated systems. Moreover, we illustrate the negative performance effect of the changes over time in the query topics when a distributed clustered system is used. On the contrary, the performance of a distributed replicated system is query independent
Variations of the Energy of Free Particles in the pp-Wave Spacetimes
We consider the action of exact plane gravitational waves, or pp-waves, on
free particles. The analysis is carried out by investigating the variations of
the geodesic trajectories of the particles, before and after the passage of the
wave. The initial velocities of the particles are non-vanishing. We evaluate
numerically the Kinetic energy per unit mass of the free particles, and obtain
interesting, quasi-periodic behaviour of the variations of the Kinetic energy
with respect to the width of the gaussian that represents the wave.
The variation of the energy of the free particle is expected to be exactly
minus the variation of the energy of the gravitational field, and therefore
provides an estimation of the local variation of the gravitational energy. The
investigation is carried out in the context of short bursts of gravitational
waves, and of waves described by normalised gaussians, that yield impulsive
waves in a certain limit.Comment: 20 pages, 18 figures, further arguments supporting the localizability
of the gravitational energy are presented, published in Univers
Neutrino interactions on nuclei at MINERvA
Here we present analysis results from the MINERvA experiment
for scattering of neutrinos on nucleus in an energy region of few GeV. These results cover a plethora of processes important for high precision neutrino oscillation measurements in which recent results have suggested that the currently used models are insufficient
Bandlimited approximations to the truncated Gaussian and applications
In this paper we extend the theory of optimal approximations of functions in the -metric by entire functions of prescribed
exponential type (bandlimited functions). We solve this problem for the
truncated and the odd Gaussians using explicit integral representations and
fine properties of truncated theta functions obtained via the maximum principle
for the heat operator. As applications, we recover most of the previously known
examples in the literature and further extend the class of truncated and odd
functions for which this extremal problem can be solved, by integration on the
free parameter and the use of tempered distribution arguments. This is the
counterpart of the work \cite{CLV}, where the case of even functions is
treated.Comment: to appear in Const. Appro
Criação de peixes pode ser uma boa alternativa de negócio para o produtor rural brasileiro.
Há mais de 20 anos, a criação de peixes vem se apresentando como uma promissora oportunidade econômica para o empresário rural brasileiro. No início, estimulada pela expansão dos ?pesque-pagues?, a atividade mostrou-se muito lucrativa, permitindo à piscicultura experimentar um crescimento até então inédito no País. Os brasileiros começavam a perceber que os peixes poderiam ser produzidos em cativeiro, sob condições controladas e planejadas, diferentemente da tradicional pesca extrativista. A perspectiva de aumentar o consumo de um alimento nobre passou a fazer parte do dia a dia da população e o setor produtivo percebeu uma excelente alternativa de negócio.bitstream/item/123119/1/Criacao-de-peixes.pd
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