The dynamic stress intensity factor analysis of adhesively bonded material interface crack with damage under shear loading

This paper studies the dynamic stress intensity factor (DSIF) at the interface in an adhesive joint under shear loading. Material damage is considered. By introducing the dislocation density function and using the integral transform, the problem is reduced to algebraic equations and can be solved with the collocation dots method in the Laplace domain. Time response of DSIF is calculated with the inverse Laplace integral transform. The results show that the mode Ⅱ DSIF increases with the shear relaxation parameter, shear module and Poisson ratio, while decreases with the swell relaxation parameter. Damage shielding only occurs at the initial stage of crack propagation. The singular index of crack tip is -0.5 and independent on the material parameters, damage conditions of materials, and time. The oscillatory index is controlled by viscoelastic material parameters.     

Electronic Structure Research on Lattice Stability of V,Nb, and Ta by Density Functional Theory

The difference of energy and electronic structure of V, Nb, and Ta in different crystalline structures were investigated by different methods in density functional theory (DFT). Latticeconstants, total energies, and densities of states of these metals were calculated using the plane-wave pseudopotential method in DFT. Results were compared with those of projector augmented wave method, CALPHAD method, and experiments. Total energy and electronic structure analyses showed that valence electrons mostly transferred from s to p or d state, changing obviously with both the crystal structure and the elemental period number from V to Ta and leading to stronger cohesion, higher cohesive energy and more stable lattice of heavier metals.     

用于高能轻粒子探测的延迟线PPAC(英文)

气体探测器有成本低廉、制备简单、性能可靠和方便使用等特点。研制了一种5层板结构的延迟线平行板雪崩电离室（PPAC）,用于兰州放射性束流线（RIBLL）上开展的实验。在57.6 MeV/u的6He束流条件下测试了这种探测器对高能轻粒子的适用性,得到了位置分辨为1.8 mm (FWHM), 时间分辨为2.6 ns, 以及可靠的探测效率。The gas detectors have the characteristics of low cost, easy preparation, reliable capability and convenient for use etc. A delay line parallel plate avalanche counter(PPAC) with five plates has been developed for the experiments at Radioactive Ion Beam Line in Lanzhou(RIBLL). The applicability of counter for high energy light ion has been tested with 57.6 MeV/u 6He beam. A position resolution of ~1.8 mm(FWHM) and a timing resolution of ~2.6 ns are achieved. The detection efficiency is reasonable.     

A generalized Collins formula derived by virtue of the displacement-squeezing related squeezed coherent state representation

Based on the displacement-squeezing related squeezed coherent state representation ≤ft\vert z\right\rangle _{g} and using the technique of integration within an ordered product of operators, this paper finds a generalized Fresnel operator, whose matrix element in the coordinate representation leads to a generalized Collins formula (Huygens--Fresnel integration transformation describing optical diffraction). The generalized Fresnel operator is derived by a quantum mechanical mapping from z to sz-rz^{\ast } in the % ≤ft\vert z\right\rangle _{g} representation, while ≤ft\vert z\right\rangle _{g} in phase space is graphically denoted by an ellipse.     

动静组合加载下花岗岩的力学性能

在霍普金森试验系统上进行了花岗岩动静组合加载试验,获得了花岗岩在动静组合加载下的力学性能.试验结果表明:当动载不变,改变静栽大小,在弹性范围内,花岗岩强度随着静载增大而增大;当静载超过弹性极限时,花岗岩强度迅速降低;在其破坏过程中对冲击能量的吸收随静载增大而减小;变形模量呈现明显的两段特征.当静载不变,改变动载大小,花岗岩的强度随动载增大而增大;变形模量先随动载增大而增大,而后又突然变小,并不出现两段特征;在其破坏过程中对冲击能量的吸收随动载应变率的增大而逐渐增大.所得结果为岩爆、深部破岩等研究提供实验依据.     

一种不完备测试数据下的结构损伤识别方法

在单元刚度损伤系数和振型扩阶的基础上,建立了单元的损伤控制方程,提出了一种不完备测试自由度下的损伤识别方法。该方法以单元刚度损伤系数作为识别量,通过计算结构损伤前后频率和振型的改变,然后利用控制方程反解出损伤系数,从而确定出结构损伤位置和大小。悬臂梁桁架结构的数值模拟表明,在一定的噪声水平下可以同时成功地识别出的损伤位置和程度,而且对噪声有较强的鲁棒性。     

A Ferroelectric Frequency-Doubling Material-Potassium Lithium Niobate

The potassium lithium niobate crystals have been grown up. The shapes of solid-melt interfaces which maintaining the steady growth of the potassium lithium niobate crystals have been described. The optical transmission spectrum of the crystal has been surveyed. The perfected crystals showed good Second Harmonic Generation properties.     

ADAPTIVE NONLINEAR FEEDBACK CONTROL OF CHAOTIC SYSTEMS BASED ON REDUCED PARAMETER QUADRATIC PREDICTORS

An adaptive nonlinear feedback-control method is proposed to control continuous-time chaotic dynamical systems, where the adaptive nonlinear controller acts on only one-dimensional error signal between the desired state and the observed chaotic state of a system. The reduced parameter adaptive quadratic predictor used in adaptive feedback cancellation of the nonlinear terms can control the system to any desired state. Computer simulation results on the Lorenz system are shown to demonstrate the effectiveness of this feedback-control method.     

化学研究中的扫描探针显微学

20世纪 80年代初期 ,扫描隧道显微技术 (ＳｃａｎｎｉｎｇＴｕｎｎｅｌｉｎｇＭｉｃｒｏｓｃｏｐｙ,以下略称为ＳＴＭ)问世[1] 。以后仅十余年 ,以ＳＴＭ为代表的扫描探针显微技术 (ＳｃａｎｎｉｎｇＰｒｏｂｅＭｉｃｒｏｓｃｏｐｙ,ＳＰＭ)迅速发展 ,应用也已经拓展到了包括物理、化学、生物、材料等众多领域。可以预言 ,随着科学技术的不断进步 ,ＳＰＭ技术将不断显示出其优越性 ,尤其在纳米科技异军突起的今天 ,越发离不开这一集观察、分析及操作原子分子等功能于一体的技术。本文我们将着重介绍ＳＰＭ技术 ,特别是电化学ＳＴＭ技术在化…     

稳定自由基存在下苯乙烯聚合的加速剂

研究了稳定自由基存在下苯乙烯的活性聚合,发现在β－酮酸酯－乙酰乙酸乙酯,乙二酸二乙酯,1,3－二酮－乙酰丙酮的少量存在下,苯乙烯聚合速率显著增加,分子量可控,分子量在布较窄。而乙酰丙酮较大量存在下,聚苯乙烯分散性稍微变宽。