151,909 research outputs found
Multi-objective resource selection in distributed information retrieval
In a Distributed Information Retrieval system, a user submits a query to a broker, which determines how to yield a given number of documents from all possible resource servers. In this paper, we propose a multi-objective model for this resource selection task. In this model, four aspects are considered simultaneously in the choice of the resource: document's relevance to the given query, time, monetary cost, and similarity between resources. An optimized solution is achieved by comparing the performances of all possible candidates. Some variations of the basic model are also given, which improve the basic model's efficiency
Experiments with document archive size detection
The size of a document archive is a very important parameter for resource selection in distributed information retrieval systems. In this paper, we present a method for automatically detecting the size (ie the number of documents) of a document archive, in case the archive itself does not provide such information. In addition, a method for detecting incremental change of the archive size is also presented, which can be useful for deciding if a resource description has become obsolete and needs to be regenerated. An experimental evaluation of these methods shows that they provide quite acurate information
Subthreshold rho contribution in J/psi decay to omega pion pion and Kaon anti-Kaon pion
We carry out a theoretical and Monte Carlo study on the decays into
and through intermediate subthreshold meson
by using SU(3)-symmetric Lagrangian approach. It is found that the subthreshold
contribution is not negligible and may have significant influence on
partial wave analysis of resonances in these channels, especially near the
and thresholds.Comment: 12 pages, 5 figure
Optimal realizations of floating-point implemented digital controllers with finite word length considerations.
The closed-loop stability issue of finite word length (FWL) realizations is
investigated for digital controllers implemented in floating-point arithmetic.
Unlike the existing methods which only address the effect of the mantissa bits
in floating-point implementation to the sensitivity of closed-loop stability,
the sensitivity of closed-loop stability is analysed with respect to both the
mantissa and exponent bits of floating-point implementation. A computationally
tractable FWL closed-loop stability measure is then defined, and the method of
computing the value of this measure is given. The optimal controller realization
problem is posed as searching for a floating-point realization that maximizes
the proposed FWL closed-loop stability measure, and a numerical optimization
technique is adopted to solve for the resulting optimization problem. Simulation
results show that the proposed design procedure yields computationally efficient
controller realizations with enhanced FWL closed-loop stability performance
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