Orthotropic semi-infinite medium with a crack under thermal shock

A cracked orthotropic semi-infinite plate under thermal shock is investigated. The thermal stresses are generated due to sudden cooling of the boundary by ramp function temperature change. The superposition technique is used to solve the problem. The crack problem is formulated by applying the thermal stresses obtained from the uncracked plate with opposite sign to be the only external loads on the crack surfaces as the crack surface tractions. The Fourier transform technique is used to solve the problem leading to a singular equation of the Cauchy type. The singular integral equation is solved numerically using the expansion method. The influence of the material orthotropy on the stress intensity factors is shown by comparing the results obtained for different orthotropic materials and isotropic materials in the case of plane stress. The numerical results of the stress intensity factors are demonstrated as a function of time, crack length, location of the crack and the duration of the cooling rate.     

研究岩石破裂等弱化行为的力－位移组合控制方法

本文介绍了一种用力和位移的线性组合控制岩石试验的新方法。该方法已在一台自制的伺服实验系统上和一台MTS实验系统上得到了实现。用这种方法能够简便地求出通常难以求出的具有Ⅱ类特性岩石的全应力-应变曲线,而且能够变化出如广义应力松驰等其它实验类型,从而能够对时间依赖性进行深入的研究。由于其易于采用的特点,它在研究岩石破裂乃至摩擦等弱化过程方面有着广泛的应用前景。     

园柱壳中环裂纹对弹性波的散射

本文在经典弹性薄壳运动方程基础上,分析了圆柱壳中环向穿透裂纹对扭转波和膨胀波的散射,求得了反射系数及相应的动态应力强度因子。通过检查能量平衡关系验证了所用方法的正确性。     

Determination of the dynamic stress intensity factorsK I d andK II d,for a mixed-mode propagating crack

In this paper, the dynamic propagation problem of a mixed-mode crack was studied by means of the experimental method of caustics. The initial curve and caustic equations were derived under the mixed-mode dynamic condition. A multi-point measurement method for determining the dynamic stress intensity factors,K _I ^d , andK _II ^d , and the position of the crack tip was developed. Several other methods were adopted to check this method, and showed that it has a good precision. Finally, the dynamic propagating process of a mixed-mode crack in the three-point bending beam specimen was investigated with our method.     

高掺杂Ce,Gd(Y_(3-x-y)Ce_xGd_y)Al_5O_(12)荧光粉的发光下降及温度猝灭特性

采用高温固相法分别合成了不同Ce浓度掺杂的和固定Ce浓度为0.06不同Gd浓度掺杂的Y3Al5O12(YAG)系列荧光粉,通过测量其激发、发射光谱、漫反射光谱、荧光寿命和变温发射光谱,研究了掺杂元素的浓度对荧光粉发光性能的影响以及荧光粉发光的温度猝灭性质。研究结果表明:荧光粉发光强度随着Ce3+掺杂浓度和Gd3+掺杂浓度的提高均呈下降趋势。分析发现,荧光粉发光强度下降并非主要由浓度猝灭所引起,而是由于高浓度掺杂下发生YAG基质与Ce3+对激发光的竞争吸收,导致Ce3+对激发光的吸收量减少,从而影响发光强度。温度实验表明,随着温度的升高,荧光粉发光强度下降。Ce含量的改变对YAG:Ce荧光粉的热猝灭性质影响较小,Gd的掺杂使荧光粉的发射波长向长波方向移动,同时热猝灭现象严重。     

Spectroscopic diagnostics of laser-induced plasmas

An overview of spectroscopic diagnostics techniques for low temperature plasmas is presented with an emphasis to electron number density — N_e measurement. Stark broadening of non-hydrogenic atom and positive ion spectral lines is given. The attention is drawn to experimental techniques used for line intensity and line profile measurement. Self-absorption test, importance of Abel inversion, deconvolution of experimental line profiles and measurement of line asymmetry are treated in some detail in order to improve N_e measurements. Finally the sources of theoretical and experimental Stark broadening data are reviewed and some details discussed.     

Donor–acceptor nonradiative energy transfer mediated by surface plasmons on ultrathin metallic films

Selected properties of donor–acceptor energy transfer in the presence of surface plasmon coupled emission (SPCE) on metallic nanofilms are demonstrated. These properties of surface plasmon mediated energy transfer (SPMET) are for the first time compared to those of traditional energy transfer (ET) based on the same donor–acceptor system. The presence of plasmons significantly accelerates energy transfer as revealed by the results of fluorescence intensity decay. In particular, the rise time of acceptor fluorescence intensity upon donor excitation is 10 times shorter in the presence of SPCE. It is also observed that contrary to ET the sensibilized acceptor emission in SPMET is totally linearly polarized.     

三相交流电弧吹样法光谱分析初探

介绍了三相交流电弧吹样法的理论、装置和性能。证明三相电弧对提高吹样法光谱分析的性能很有帮助。     

不等缝宽多缝的夫琅禾费衍射及计算机模拟

基于复数法、积分法和矢量法研究不等间距多缝的夫琅禾费衍射的振幅和光强分布.应用Matlab软件进行数值模拟得到衍射图样,分析衍射图样.衍射振幅的推导方法和计算机模拟方法对于研究干涉、衍射等有一定的实际意义和指导意义.