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Averaging Procedure (averaging + procedure)

Distribution by Scientific Domains

Chemistry	33%

Selected Abstracts

An asymptotic-induced one-dimensional model to describe fires in tunnels

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 14 2002
Ingenuin Gasser
We derive a simple one-dimensional model for the description of fire events in long vehicle tunnels, which is based on appropriate low-Mach number asymptotics as well as on averaging procedure along the cross-section of a tunnel. Turbulent effects are modelled using a phenomenological model. Numerical simulations based on a standard finite-difference method show the ability of the new model to describe fires in tunnels at least qualitatively. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Time-Domain and Morphological Analysis of the P-Wave.

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2008
Part I: Technical Aspects for Automatic Quantification of P-Wave Features
Introduction: Time-domain and morphological analysis of P-wave from surface electrocardiogram has been extensively used to identify patients prone to atrial arrhythmias, especially atrial fibrillation (AF). However, since no standard procedure exists for P-wave preprocessing, standardization of cut-off values for P-wave duration and morphological features is difficult. This study is a methodological investigation of P-wave preprocessing procedures for automatic time-domain and morphological analysis. Methods: We compared, on simulated and real data, the P-wave template obtained applying three alignment algorithms with that obtained without alignment, in terms of template error, shift error, P-wave duration, and morphological parameters. We also proposed automatic algorithms for estimation of P-wave duration. Results: We found that alignment is necessary for a reliable extraction of P-wave template by the averaging procedure, in order to perform time-domain and morphological analysis. On simulated and real data, the error on P-wave duration can be as high as 30 ms on a template obtained without alignment; if alignment procedure is performed, the error on P-wave duration is negligible. Analogously, morphological features are correctly estimated only on a P-wave template obtained with P-waves alignment. We also found that the proposed algorithm for the automatic estimation of the P-wave duration gave reliable results. [source]

Particle Size Distributions from Static Light Scattering with Regularized Non-Negative Least Squares Constraints

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2006
Alejandro R. Roig
Abstract Simulated data from static light scattering produced by several particle size distributions (PSD) of spherical particles in dilute solution is analyzed with a regularized non-negative least squares method (r-NNLS). Strong fluctuations in broad PSD's obtained from direct application of NNLS are supressed through an averaging procedure, as introduced long ago in the inversion problem in dynamic light scattering. A positive correlation between the best PSD obtained from several averaging schemes and the condition number of the respective data transfer matrices was obtained. The performance of the method is found to be similar to that of constrained regularization (CONTIN), which uses also NNLS as a starting solution, but incorporates another regularizing strategy. [source]

New approach to the theory of lattice vibrations of random alloys

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004
V. S. VinogradovArticle first published online: 16 NOV 200
Abstract The theory of vibrational excitations of random alloys is presented, which takes into account the scattering of excitations on n -impurity complexes (clusters) and is capable to describe complex structure of their spectra. The essential feature of the theory consists in two-stage disorder averaging procedure. First, theory equations are averaged and Fourier transformed over the coordinate characterizing the cluster position as a whole. Then they are averaged over inter-impurity distances in the cluster. The derivation of the Green function equations is carried out both in the version similar to average-t-matrix approximation (ATA) and in that similar to coherent potential approximation (CPA). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Internal Noise Coherent Resonance for Mesoscopic Chemical Oscillations: A Fundamental Study

CHEMPHYSCHEM, Issue 7 2006
Zhonghuai Hou
Abstract The effect of internal noise for a mesoscopic chemical oscillator is studied analytically in a parameter region outside, but close to, the supercritical Hopf bifurcation. By normal form calculation and a stochastic averaging procedure, we obtain stochastic differential equations for the oscillation amplitude r and phase , that is solvable. Noise-induced oscillation and internal noise coherent resonance, which has been observed in many numerical experiments, are reproduced well by the theory. [source]

Retrieving low- and medium-resolution structural features of macromolecules directly from the diffraction intensities , a real-space approach to the X-ray phase problem

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2008
Wu-Pei Su
A simple mathematical algorithm is proposed to generate electron-density functions whose Fourier amplitudes match the diffraction intensities. The function is by construction everywhere positive. Using appropriate averaging procedures, the high-density regions of such functions could yield important structural information about macromolecular crystals. Trial calculations on protein crystals show that the protein envelope plus other structural motifs such as barrels and secondary structures could be recognized in the density maps. As such, the algorithm could provide a basis for new phasing methods or supplement existing phasing methods. [source]