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Perturbation Technique (perturbation + technique)

Distribution by Scientific Domains
Engineering55%
Mathematics and Statistics22%

Selected Abstracts

On generalized stochastic perturbation-based finite element method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2006
Marcin Kami
Abstract Generalized nth order stochastic perturbation technique, that can be applied to solve some boundary value or boundary initial problems in computational physics and/or engineering with random parameters is proposed here. This technique is demonstrated in conjunction with the finite element method (FEM) to model 1D linear elastostatics problem with a single random variable. The symbolic computer program is employed to perform computational studies on convergence of the first two probabilistic moments for simple unidirectional tension of a bar. These numerical studies verify the influence of coefficient of variation of the random input and, at the same time, of the perturbation parameter on the first two probabilistic moments of the final solution vector. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Phase Transformation and Densification Behavior of Microwave-Sintered Si3N4,Y2O3,MgO,ZrO2 System

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009
Sreekumar Chockalingam
A 2.45 GHz microwave-sintered Si3N4,Y2O3,MgO system containing various amounts of ZrO2 secondary additives have been studied with respect to phase transformation and densification behavior. The temperature dependent dielectric properties were measured from 25°C to 1400°C using a conventional cavity perturbation technique. Phase transformation behavior was studied using X-ray diffractometry. Microwave sintered results were compared with those of conventional sintered results. It has been found that , to , phase transformation was completed at a lower temperature in microwave-sintered samples than those of the conventionally sintered samples. Density of the microwave-sintered samples increased up to 2.5 wt% of ZrO2 addition and thereafter it showed a tendency to decrease or remain constant. The decrease in density is attributed to the pore generation caused by decomposition due to the localized over heating. [source]

A novel method of detecting HIV/AIDS using microwaves

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2008
Anil Lonappan
Abstract HIV/AIDS is one of the most destructive epidemics in ever recorded history claims an estimated 2.4,3.3 million lives every year. Even though there is no treatment for this pandemic Elisa and Western Blot tests are the only tests currently available for detecting HIV/AIDS. This article proposes a new method of detecting HIV/AIDS based on the measurement of the dielectric properties of blood at the microwave frequencies. The measurements were made at the S-band of microwave frequency using rectangular cavity perturbation technique with the samples of blood from healthy donors as well as from HIV/AIDS patients. An appreciable change is observed in the dielectric properties of patient samples than with the normal healthy samples and these measurements were in good agreement with clinical results. This measurement is an alternative in vitro method of diagnosing HIV/AIDS using microwaves. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 557,561, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23143 [source]

Analysis of female human breast tissues at microwave frequencies

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2008
G. Bindu
Abstract Complex permittivities of in vitro female human breast tissues have been measured at the ISM band using rectangular resonant cavity perturbation technique. Ranges of dielectric properties and water contents of these tissues are presented. The results show that benign and malignant breast tumors can be characterized based on the variation of the dielectric properties with respect to the dielectric parameters of the normal breast tissues. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 614,616, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23160 [source]

Synovial fluid at microwave frequencies

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2007
Anil Lonappan
Abstract Arthritis is one of the most pervasive diseases that causes of disability. For most people arthritis pain and inflammation cannot be avoided as the body ages. The present communication reports the study on the synovial fluid has the main lubricant in joints collected from normal persons and those ailing from arthritis are subjected to the microwave study and the variations of the dielectric parameters are investigated. The in vitro measurements of synovial fluid samples are done using cavity perturbation technique in the frequency range of 2,3 GHz. It is observed that in this band, the dielectric constant of normal samples are higher than those of arthritis affected ones and conductivity of is higher in normal samples, which finds application in detecting arthritis using microwaves. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1700,1702, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22552 [source]

Stochastic perturbation approach to the wavelet-based analysis

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 4 2004
M. Kami
Abstract The wavelet-based decomposition of random variables and fields is proposed here in the context of application of the stochastic second order perturbation technique. A general methodology is employed for the first two probabilistic moments of a linear algebraic equations system solution, which are obtained instead of a single solution projection in the deterministic case. The perturbation approach application allows determination of the closed formulas for a wavelet decomposition of random fields. Next, these formulas are tested by symbolic projection of some elementary random field. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Application of variational iteration method for modified Camassa-Holm and Degasperis-Procesi equations

NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 5 2010
H. Jafari
Abstract In this article, the variational iteration method (VIM) is used to obtain approximate analytical solutions of the modified Camassa-Holm and Degasperis-Procesi equations. The method is capable of reducing the size of calculation and easily overcomes the difficulty of the perturbation technique or Adomian polynomials. The results reveal that the VIM is very effective. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010 [source]

Asymptotic evaluation of effective complex moduli of fibre-reinforced viscoelastic composite materials

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
I. Andrianov Prof. Dr. Sc.
We propose an asymptotic approach for the evaluation of effective complex moduli of viscoelastic fibre-reinforced composite materials. Our method is based on the homogenization technique. We start with a non-trivial expansion of the input plane-strain boundary value problem by ratios of visco-elastic constants. This allows to simplify the governing equations to forms analogous to the complex transport problem. Then we apply the asymptotic homogenization method, coming from the original problem on multi-connected domain to the cell problem, defined on a unit cell of the periodic structure. For the analytical solution of the cell problem we apply the boundary perturbation technique, the asymptotic expansion by a distance between two neighbouring fibres and the method of two-point Padé approximants. As results we derive uniform analytical representations for effective complex moduli, valid for all values of the components volume fractions and properties. [source]

Theoretical Study of Catalytic Efficiency of a Diels,Alderase Catalytic Antibody: An Indirect Effect Produced During the Maturation Process

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2008
Sergio Martí Dr.
Abstract The Diels,Alder reaction is one of the most important and versatile transformations available to organic chemists for the construction of complex natural products, therapeutics agents, and synthetic materials. Given the lack of efficient enzymes capable of catalyzing this kind of reaction, it is of interest to ask whether a biological catalyst could be designed from an antibody-combining site. In the present work, a theoretical study of the different behavior of a germline catalytic antibody (CA) and its matured form, 39,A-11, that catalyze a Diels,Alder reaction has been carried out. A free-energy perturbation technique based on a hybrid quantum-mechanics/molecular-mechanics scheme, together with internal energy minimizations, has allowed free-energy profiles to be obtained for both CAs. The profiles show a smaller barrier for the matured form, which is in agreement with the experimental observation. Free-energy profiles were obtained with this methodology, thereby avoiding the much more demanding two-dimensional calculations of the energy surfaces that are normally required to study this kind of reaction. Structural analysis and energy evaluations of substrate,protein interactions have been performed from averaged structures, which allows understanding of how the single mutations carried out during the maturation process can be responsible for the observed fourfold enhancement of the catalytic rate constant. The conclusion is that the mutation effect in this studied germline CA produces a complex indirect effect through coupled movements of the backbone of the protein and the substrate. [source]