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Various Orders (various + order)

Distribution by Scientific Domains
Engineering60%

Selected Abstracts

Non-local dispersive model for wave propagation in heterogeneous media: one-dimensional case

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002
Jacob Fish
Abstract Non-local dispersive model for wave propagation in heterogeneous media is derived from the higher-order mathematical homogenization theory with multiple spatial and temporal scales. In addition to the usual space,time co-ordinates, a fast spatial scale and a slow temporal scale are introduced to account for rapid spatial fluctuations of material properties as well as to capture the long-term behaviour of the homogenized solution. By combining various order homogenized equations of motion the slow time dependence is eliminated giving rise to the fourth-order differential equation, also known as a ,bad' Boussinesq problem. Regularization procedures are then introduced to construct the so-called ,good' Boussinesq problem, where the need for C1 continuity is eliminated. Numerical examples are presented to validate the present formulation. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A new variable-order singular boundary element for two-dimensional stress analysis

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002
K. M. Lim
Abstract A new variable-order singular boundary element for two-dimensional stress analysis is developed. This element is an extension of the basic three-node quadratic boundary element with the shape functions enriched with variable-order singular displacement and traction fields which are obtained from an asymptotic singularity analysis. Both the variable order of the singularity and the polar profile of the singular fields are incorporated into the singular element to enhance its accuracy. The enriched shape functions are also formulated such that the stress intensity factors appear as nodal unknowns at the singular node thereby enabling direct calculation instead of through indirect extrapolation or contour-integral methods. Numerical examples involving crack, notch and corner problems in homogeneous materials and bimaterial systems show the singular element's great versatility and accuracy in solving a wide range of problems with various orders of singularities. The stress intensity factors which are obtained agree very well with those reported in the literature. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Reinforcement of a thin plate by a thin layer

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2008
Leila Rahmani
Abstract We study the bending of a thin plate, stiffened with a thin elastic layer, of thickness ,. We describe the complete construction of an asymptotic expansion with respect to , of the solution of the Kirchhoff,Love model and give optimal estimates for the remainder. We identify approximate boundary conditions, which take into account the effect of the stiffener at various orders. Thanks to the tools of multi-scale analysis, we give optimal estimates for the error between the approximate problems and the original one. We deal with a layer of constant stiffness, as well as with a stiffness in ,,1. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Design of novel microstrip low-pass filter using defected ground structure

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2008
Petr Vágner
Abstract A novel microstrip low-pass filter utilizing defected ground structure (DGS) units is presented in this article. A DGS unit is simulated with different physical dimensions in order to show variation of attenuation pole and cut-off frequency. Next, a low-pass filter using proposed DGS unit is designed. A method for determining dimensions of microstrip structure and DGS units is proposed. Influence of dimensions of the microstrip structure on filter characteristics is investigated and simulated. Filters of various orders are simulated as well. Selected filter is simulated and experimentally verified. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 10,13, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22982 [source]

Pattern-recognition-based detection of planar objects in three-dimensional electron-density maps

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2008
Johan Hattne
A pattern-recognition-based method for the detection of planar objects in protein or DNA/RNA crystal structure determination is described. The procedure derives a set of rotation-invariant numeric features from local regions in the asymmetric unit of a crystallographic electron-density map. These features, primarily moments of various orders, capture different aspects of the local shape of objects in the electron density. Feature classification is achieved using a linear discriminant that is trained to optimize the contrast between planar and nonplanar objects. In five selected test cases with X-ray data spanning 2.0,3.0,Å resolution, the procedure identified the correct location and orientation for almost all of the double-ring and a majority of the single-ring planar groups. The accuracy of the location of the plane centres is of the order of 0.5,Å, even in moderately noisy density maps. [source]