306,053 research outputs found
Adaptive Analysis of On-line Algorithms
On-line algorithms are usually analyzed using competitive analysis, in which the performance
of on-line algorithm on a sequence is normalized by the performance of the optimal on-line
algorithm on that sequence. In this paper we introduce adaptive/cooperative analysis as an
alternative general framework for the analysis of on-line algorithms. This model gives promising
results when applied to two well known on-line problems, paging and list update. The idea is
to normalize the performance of an on-line algorithm by a measure other than the performance
of the on-line optimal algorithm OPT. We show that in many instances the perform of OPT
on a sequence is a coarse approximation of the difficulty or complexity of a given input. Using
a finer, more natural measure we can separate paging and list update algorithms which were
otherwise undistinguishable under the classical model. This createas a performance hierarchy of
algorithms which better reflects the intuitive relative strengths between them. Lastly, we show
that, surprisingly, certain randomized algorithms which are superior to MTF in the classical
model are not so in the adaptive case. This confirms that the ability of the on-line adaptive
algorithm to ignore pathological worst cases can lead to algorithms that are more efficient in
practice
Optimization via Chebyshev Polynomials
This paper presents for the first time a robust exact line-search method
based on a full pseudospectral (PS) numerical scheme employing orthogonal
polynomials. The proposed method takes on an adaptive search procedure and
combines the superior accuracy of Chebyshev PS approximations with the
high-order approximations obtained through Chebyshev PS differentiation
matrices (CPSDMs). In addition, the method exhibits quadratic convergence rate
by enforcing an adaptive Newton search iterative scheme. A rigorous error
analysis of the proposed method is presented along with a detailed set of
pseudocodes for the established computational algorithms. Several numerical
experiments are conducted on one- and multi-dimensional optimization test
problems to illustrate the advantages of the proposed strategy.Comment: 26 pages, 6 figures, 2 table
Event Recognition Using Signal Spectrograms in Long Pulse Experiments
As discharge duration increases, real-time complex analysis of the signal becomes more important. In this context, data acquisition and processing systems must provide models for designing experiments which use event oriented plasma control. One example of advanced data analysis is signal classification. The off-line statistical analysis of a large number of discharges provides information to develop algorithms for the determination of the plasma parameters from measurements of magnetohydrodinamic waves, for example, to detect density fluctuations induced by the Alfvén cascades using morphological patterns. The need to apply different algorithms to the signals and to address different processing algorithms using the previous results necessitates the use of an event-based experiment. The Intelligent Test and Measurement System platform is an example of architecture designed to implement distributed data acquisition and real-time processing systems. The processing algorithm sequence is modeled using an event-based paradigm. The adaptive capacity of this model is based on the logic defined by the use of state machines in SCXML. The Intelligent Test and Measurement System platform mixes a local multiprocessing model with a distributed deployment of services based on Jini
Parameterized Analysis of Online Steiner Tree Problems
Steiner tree problems occupy a central place in both areas of approximation and on-line algorithms. Many variants have been studied from the point of view of competitive analysis, and for several of these variants tight bounds are known. However, in several cases, worst-case analysis is overly pessimistic, which fails to explain the relative performance of algorithms. We show how adaptive analysis can help resolve this problem. As case studies, we consider the Steiner tree problem in directed graphs, and the Priority Steiner tree problem
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Evaluation of impedance parameters in transmission lines
textA more accurate and flexible grid analysis is achieved through an adaptive and
dynamic calculation of line parameters. This is needed for future smart grid
implementation. The primary objective of this thesis is to analyze the calculation of
transmission line parameters. The impact certain assumptions have on the accuracy of
line parameters and fault location algorithms are evaluated. In particular, the impact of
the grounded shield wire assumption on the accuracy of fault location algorithms is
analyzed. This implies that the impedance of towers be taken into consideration, rather
than the simplification of a direct connection of the earth wire to ground. Secondly, the
phenomenon of skin-effect is analyzed and evaluated in regards to a more accurate
representation of line parameters and a minimization of parameter inaccuracy.Electrical and Computer Engineerin
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