1,721,111 research outputs found
Shear and normal strain effects of core layers in vibration of square sandwich plates under clamped boundary conditions
No full textThe authors previously investigated the effects of both shear and normal strains in the viscoelastic core layer on modal properties of sandwich plates under hinged boundary conditions. For such boundary conditions, analytic formulation of characteristic equations was possible. Agreeing that most real boundary conditions must lie somewhere between hinged and clamped, it is naturally worthwhile to solve for the clamped boundary conditions, for which, however, analytic formulation of the characteristic equations is not possible. In this study, hence, the finite difference method is utilized as a tool for numerical analysis. The effects of neglecting the extensional or compressional strain in the core material for the clamped boundary conditions are studied and compared with the case of simply supported boundary conditions. (C) 1999 Academic Press
Effects of normal strain in core material on modal property of sandwich plates
No full textin vibration analysis of sandwich beam/plates it is often assumed that there is shear deformation only, without extension or compression in the viscoelastic layer. Certainly, this assumption may have limitations, for example, with increase of the core thickness or frequency range of vibration. The purpose of this paper is to consider the normal, as well as shear strain of the core material for modal parameter estimation of the sandwich plates and to investigate how much error will be caused by neglecting the extension or compression in the core material. Natural frequencies and modal loss factors are estimated for a simply supported square plate by taking the normal as well as shear deformation into account for dynamic modeling. Nondimensional characteristic equations are formulated and solved numerically for various ratios of the base layer thickness to plate length, core layer thickness to base layer constraining layer thickness to base layer, and shear modulus of core material to elastic modulus of base layer The effects of the various parameters on the modal properties are shown to be intercorrelated to each other and hence difficult to summarize in one phrase. Normal deformation of be core material plays an important role when the thickness ratio of constraining layer to base layer is 0.5 and its Poisson's ratio is smaller than 0.49, and hence need to be included in the dynamic modeling especially for estimation of modal damping when one of the following conditions are met; 1) the ratio of base layer thickness to plate length is greater than 0.02, 2) the thickness ratio of core layer to base layer is greater than 0.01, 3) the wavelength of a mode is less than one third of the plate length, 4) the ratio of shear modulus of core material to elastic modulus of base material is less than 10(-5)
Effect of the addition of Ag on the strengthening of Al3Li phase in Al-Li single crystals
No full textThe variation of the critical resolved shear stress as a function of aging condition has been measured in ternary Al- similar to (1.9-2.0) wt% Li- similar to 0.4 wt% Ag single crystals and has been analyzed using the same version of order-hardening theory as in our previous work in binary single crystals. The result showed that the antiphase boundary energy of the Al3Li lattice on {111} definitively increases from about 0.118 J/m(2) in binary crystals to 0.125 +/- 0.012 J/m(2) in ternary crystals, in good agreement with the analysis of the transition behavior from shearing to looping and of the dislocation pair spacings. A strong segregation tendency of Ag into the Al3Li lattice is believed to be responsible for this increment. Our previous result of gamma(apb) (0.118 +/- 0.006 J/m(2)) in binary crystals is, although unlikely from the recent suggestion of Nembach, the best value one can obtain from the recent knowledge of order-hardening theory. This is slightly larger than that (about 0.100 J/m(2)) obtained from the analysis of the transition from shearing to looping and somewhat larger than the result (about 0.085 J/m(2)) of the first-principles calculation. Three factors are discussed as principal causes of a possibility of an overestimation of gamma(apb) on applying order-hardening theory. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved
Prediction of protein secondary structure content using amino acid composition an evolutionary information
No full textKnowing protein structure and inferring its function from the structure are one of the main issues of computational structural biology, and often the first step is studying protein secondary structure. There have been many attempts to predict protein secondary structure contents. Previous attempts assumed that the content of protein secondary structure can be predicted successfully using the information on the amino acid composition of a protein. Recent methods achieved remarkable prediction accuracy by using the expanded composition information. The overall average error of the most successful method is 3.4%. Here, we demonstrate that even if we only use the simple amino acid composition information alone, it is possible to improve the prediction accuracy significantly if the evolutionary information is included. The idea is motivated by the observation that evolutionarily related proteins share the similar structure. After calculating the homolog-averaged amino acid composition of a protein, which can be easily obtained from the multiple sequence alignment by running PSI-BLAST, those 20 numbers are learned by a multiple linear regression, an artificial neural network and a support vector regression. The overall average error of method by a support vector regression is 3.3%. It is remarkable that we obtain the comparable accuracy without utilizing the expanded composition information such as pair-coupled amino acid composition. This work again demonstrates that the amino acid composition is a fundamental characteristic of a protein. It is anticipated that our novel idea can be applied to many areas of protein bioinformatics where the amino acid composition information is utilized, such as subcellular localization prediction, enzyme subclass prediction, domain boundary prediction, signal sequence prediction, and prediction of unfolded segment in a protein sequence, to name a few
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Adaptive mesh generation by bubble packing method
No full textThe bubble packing method is implemented for adaptive mesh generation in two and three dimensions. Bubbles on the boundary of a three-dimensional domain are controlled independently of the interior bubbles in the domain, and a modified octree technique is employed to place initial bubbles in the three-dimensional zone. Numerical comparisons are made with other in mesh generation techniques to demonstrate the effectiveness of the present bubble packing scheme for two- and three-dimensional domains. It is shown that this bubble packing method provides a high quality of mesh and affordable control Of mesh density as well.The authors would like to thank the Ministry of Science and Technology, Korea, for the financial support by a grant from the Critical Technology 21 Project
Exercise training delays cardiac dysfunction, inhibits autophagy and improves the fatty acid uptake on post-infarction left ventricular remodeling in the rabbit.
No full textExercise training improves cardiac function through increase in autophagosome degradation and fatty acid uptake
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