Stability analyses on dynamic control for a moving body levitated magnetically over elastic guideways

Based on the Floquet theory on ordinary differential equations with periodically variable coefficients and the bifurcation approach to nonlinear equations, a numerical approach to determining the stability region of control parameters is established for a dynamic control system composed of a moving body levitated magnetically over flexible guideways. The system is nonlinearly coupled among the elastic deformation of guideways, disturbance the levitation position of the body and electromagnetic control forces. The numerical simulation is given for the system in the case in which the control parameters are taken within and out of the stability region respectively. Results show that this approach is reliable. This project is supported by NSFC(No. 19725207), the Pre-research Project of the Committee of Science and Technology for Defence of China and the Science Foundation of Education Ministry of China for Ph. D. Programmes.     

刚体位移对应变测试的影响

通过运用波前干涉理论,得到了贴片云纹干涉法测圆柱壳的位移与应变公式,分析了刚体位移及曲率对测试结果的影响情况.指出了在对压力容器及管道进行测试时应注意的事项.     

混合新几何体Γ_(-p，i)K的不等式

近来,Lutwak,Yang和Zhang提出了新几何体Γ_(-p)K的概念,获得一些结论.本文引入混合新几何体Γ_(-p,i)K的概念,即新几何体是它的特殊类,得到了混合新几何体的一些性质,并建立了相关的不等式.     

On non-Newtonian p-fluids. The pseudo-plastic case

In the following we study a class of stationary Navier-Stokes equations with shear dependent viscosity, under the non-slip (Dirichlet) boundary condition. We consider pseudo-plastic fluids. A fluid is said pseudo-plastic, or shear thinning, if in Eq. (1.1) below one has p<2. We are interested in global (i.e., up to the boundary) regularity results, in dimension n=3, for the second order derivatives of the velocity and the first order derivatives of the pressure. We consider a cubic domain Ω and impose the non-slip boundary condition only on two opposite faces. On the other faces we assume periodicity, as a device to avoid effective boundary conditions. This choice is made so that we work in a bounded domain Ω and simultaneously with a flat boundary.     

Exact solution of external tangential contact problem for a transversely isotropic elastic half-space

Summary  The following mixed boundary-value problem for a transversely isotropic elastic half-space is considered. Arbitrary tangential displacements are prescribed at the exterior of a circle, while the interior of the circle is free of tangential stress, and the normal stress vanishes all over the boundary. The governing integral equation is solved exactly, in closed form, and in terms of elementary functions. The method of continuation of solutions previously published by the author has been used here. Several examples are considered. No similar results has been reported before, even in the case of an isotropic body. Received 8 May 2000; accepted for publication 20 July 2000     

多用射弹演示装置的设计与使用

采用自制弹簧枪，配用激光瞄准，光电控制，制作了多用射弹演示装置，使用该装置可验证多个规律。     

红外测温新技术

通过介绍红外辐射的一般性质和红外测温新技术说明黑体辐射定律的具体应用     

Numerical simulations of droplet formation in a cross‐junction microchannel by the lattice Boltzmann method

An immiscible liquid–liquid multiphase flow in a cross‐junction microchannel was numerically studied using the lattice Boltzmann method. An improved, immiscible lattice BGK model was proposed by introducing surface tension force based on the continuum surface force (CSF) method. Recoloring step was replaced by the anti‐diffusion scheme in the mixed region to reduce the side‐effect and control the thickness of the interface. The present method was tested by the simulation of a static bubble. Laplace's law and spurious velocities were examined. The results show that our model is more advantageous for simulations of immiscible fluids than the existing immiscible lattice BGK models. Computational results of multiphase flow in a cross‐junction microchannel were obtained and analyzed based on dimensionless numbers. It is found that the flow pattern is decided mostly by the capillary number at a small inlet flux. However, at the same capillary number, a large inlet flux will lead to much smaller droplet generation. For this case, the flow is determined by both the capillary number and the Weber number. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and applications of novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite nanocomposites

Novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd.