Simple and green synthesis of calcium alginate/hydroxyapatite hybrid material without high temperature treatment and its flame retardancy

Cellulose - Aiming to improve the thermal stability and flame retardant properties of calcium alginate, calcium alginate (CaAlg)/hydroxyapatite (HAP) hybrid material was synthesized in situ by the...     

Study on Deformation of Polycrystalline Aluminum Alloy Using Moiré Interferometry

Polycrystalline aluminum alloy is manufactured by annealing, compared to the width of the specimen, the size of the grains can not be omitted, which makes the specimen anisotropic. Under uniaxial tension, the deformation field is inhomogeneous. In this study, moiré interferometry is successfully applied to measure the deformation of the polycrystalline specimen. The experimental results presented the stress versus strain responses of the marked grains in different orientations and different shapes. By using fringe centering method, the strain distributions under certain load in the centers and on the boundaries of the grains are analyzed.     

A variational solution of 2-D sound-structure interaction problems

Based on the fluid-structure coupling theory, a localized variational principle for analyzing the sound radiation from elastic structure submerged in water due to harmonic excitations is presented. It will be a powerful tool to formulate various numerical methods for steady response of structural-acoustic systems. By means of this variational principle a hybrid element method, in which an analytical solution valid in most of the surrounding water is incorporated with finite elements distributed in the structure and its neighboring water, is devised. Computational examples are then given to demonstrate its high accuracy and time saving. The project supported by the National Natural Science Foundation of China (10172038) and the Doctoral Program Foundation of Institution of Higher Education of China (20040487013). The English text was polished by Yunming Chen.     

Simultaneous stress separation,smoothing of measured thermoelastic isopachic information and enhanced boundary data

A new thermoelastic hybrid method of stress analysis is demonstrated experimentally which simultaneously smooths the measured isopachic data, enhances the boundary information, and separates the stresses at nonboundary locations using only the isopachics. The technique is illustrated by application to a tensile plate containing a hole.     

Transient response of a finite crack in an orthotropic strip under the in-plane shear impact

The transient response of a central crack in an orthotropic strip under the in-plane shear impact loading is studied by using the dual integral equation method proposed by Copson and Sih. The general formula for the shear stress intensity factor near the crack tip is derived. Numerical results of with in various cases are obtained by solving the second kind Fredholm integral equation and by performing the inverse Laplace transform.     

Hydraulic fracturing of a saturated porous medium-II: Special cases

This investigation deals with the problem of steady state hydraulic fracture in an infinite isotropic fluid-saturated elastic porous medium induced by a uniform pressure applied to the crack surfaces. A quasi-static approach is employed in the study. A boundary value problem is formulated and then analyzed by means of the Fourier transform associated with the Wiener-Hopf technique. Stress intensity factor and potential energy release rate are found by asymptotic analysis and the superposition principle as functions of the speed of crack propagation. The material breakdown process at the crack tip is discussed based on Dugdale's model. Finally, a brief discussion of the effect of pressure drop on the hydraulic fracture process and the decrease in crack speed during crack extension is included.     

Application of quasilinearization technique to the vertical channel flow and heat convection

The quasilinearization technique, also known as the generalized Newton-Raphson method, is employed to solve the problem of fluid injection through one side of a long vertical channel. With very approximate starting values, only a few iterations are needed to obtain a result with high accuracy. The results are compared with those obtained by the perturbation technique. Although the perturbation technique is perhaps the simplest and the most straight-forward method to achieve solutions to non-linear boundary value problems, the limitation on the magnitude of perturbed parameters hinders its applicability.     

Finite amplitude vibrations of a circular plate

The problem of finite-amplitude, axisymmetric free and forced vibration of a circular plate is examined with various boundary conditions. The non-linear boundary-value problem is converted into the corresponding eigenvalue problem by elimination of the time variable. Then by a Newton-Raphson iteration scheme, and the concept of analytical continuation, the solution to the non-linear eigenvalue problem for the vibrations is obtained in a discrete form. It is seen that the removal of radial restraint causes drastic changes in the plate responses and the patterns of membrane stresses. Comparison with solutions based on the Berger assumption reveals the unsuitability of the assumption when the plate is not radially restrained.     

板结构功率流的参数研究

板以及肋板结构在工程中有着广泛的应用，其振动嗓声问题一直受到理论和工程领域的关注。本文在板结构功率流理论的基础上￣［１］，对板的损耗因子和不同加肋形式对其功率流的影响进行了分析和测量。     

On the boundary value problem of elastostatics in terms of stresses

The boundary value problem of elastostatics in terms of six components of the stress consists of nine equations and three boundary conditions. In this paper, we distinguished between the possible cases and impossible cases, i.e., the problem is or is not equivalent to a boundary value problem of six equations and six boundary conditions.