爆轰波在楔面上反射数值分析

应用基元反应模型和频散可控耗散格式(DCD)对氢氧爆轰波在楔面反射进行了数值模拟.计算中氢氧混合物的化学反应采用了8种组分20个反应方程式.在处理化学反应引起的刚性问题时采用了时间算子分裂的方法.模拟了爆轰波在楔面反射由马赫反射向规则反射转变的过程,得到了反射转变临界角,同时考虑了初始压力和组分的影响,并和实验及理论分析结果进行了比较,结果是令人满意的.

Size-Dependent Elastic Properties Of Ni Nanofilms By Molecular Dynamics Simulation

Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics ( MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.

液桥中不同Prandtl数流体的热毛细对流

本文研究从上面加热的液桥中不同 pr 数流体的热表面张力驱动对流。在 Ma 数相同的条件下,不同 pr 数流体液桥中的温度分布和流场结构定性相似,但定量结果不同。小pr数(pr<<1)流体液桥中的粘性边界层远小于热边界层,最大流函数所在位置向冷端偏移,有较大的流动速度。结果表明,Ma 数是描述这种流动的敏感参数。

论旋转液体星的稳定

本文应用文献[1]中的方法,证明了旋转液体星(作为自吸引、不可压粘性液体处理)由所有振动本征模决定的稳定临界和长期稳定临界是一致的.同时,以Columbus问题作为这个结论的实验依据.这是Thomson和Tait在1883年预见而没有证明的重要结论,由此可以重新肯定旋转液体星准稳态演化过程必须按长期稳定临界判断;而对于近三十年来被否定的Jeans-Darwin双星分裂理论,必须重新进行评价.

Higher-order analysis of crack tip fields in elastic power-law hardening materials

A HIGHER-ORDER asymptotic analysis of a stationary crack in an elastic power-law hardening material has been carried out for plane strain, Mode 1. The extent to which elasticity affects the near-tip fields is determined by the strain hardening exponent n. Five terms in the asymptotic series for the stresses have been derived for n = 3. However, only three amplitudes can be independently prescribed. These are K1, K2 and K5 corresponding to amplitudes of the first-, second- and fifth-order terms. Four terms in the asymptotic series have been obtained for n = 5, 7 and 10; in these cases, the independent amplitudes are K1, K2 and K4. It is found that appropriate choices of K2 and K4 can reproduce near-tip fields representative of a broad range of crack tip constraints in moderate and low hardening materials. Indeed, fields characterized by distinctly different stress triaxiality levels (established by finite element analysis) have been matched by the asymptotic series. The zone of dominance of the asymptotic series extends over distances of about 10 crack openings ahead of the crack tip encompassing length scales that are microstructurally significant. Furthermore, the higher-order terms collectively describe a spatially uniform hydrostatic stress field (of adjustable magnitude) ahead of the crack. Our results lend support to a suggestion that J and a measure of near-tip stress triaxiality can describe the full range of near-tip states.

Size-dependent elastic properties of Ni nanofilms by molecular dynamics simulation

Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics ( MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.

重力对锥形血管中血流压力的影响——基于考虑体位改变的三维流固耦合数学模型

重力是体位改变过程中最基本的生物力学刺激因素．血流压力是表征心血管功能状态的一个基本指标．目前，体位改 变影响心血管系统的确切内部机制尚不清楚．为此，采用在流体和固体方程中分别引入体力项的方法，建立一个基于血流动 力学概念的三维流固耦合数学模型，用以研究体位改变，确切量化重力对血流压力的影响．通过数值计算，得到以下结果． 水平卧位条件下：a．单一血管中血流压力由无重力影响的轴对称二维分布变为重力影响下的三维不对称分布；b．随着进出 口压差由小变大，重力对压力分布和极值的影响由大变小，当压差值分别达到10 665.6 Pa(80 mmHg)和2 666.4 Pa(20 mmHg) 时，重力的影响就不再随进出口压差增大而变化；对三维单一流体，重力影响的总体趋势类似．对正、倒直立位，压力均为 二维轴对称分布，其重力影响强度约为水平卧位的2 倍以上．结果表明：基于血流动力学概念，引入体力项，建立三维流固 耦合模型为研究体位改变提供了一种新思路，重力对单一血管中血流压力分布和大小的影响因体位不同而不同，并与进出口 压差密切相关，提示，若血管进出口压差较小，忽略重力影响，不考虑体位改变，以二维轴对称模型来研究血管中血流状 态，须谨慎解释所得结果．

傅立叶分解法荧光层析成像

本文提出一种基于结构光照明和傅立叶分解方法的荧光层析成像技术，该技术首先将激发光的强度沿着光轴方向调制成余弦函数，然后用此激发光对样品作传统的二维扫描，在每一个扫描位置余弦函数的频率在一定的范围内扫描，同时一一对应地记录下所发出的荧光强度。只要对所纪录的荧光序列做一个简单的傅立叶变换，即可以得到此位置样品沿着光轴方向的荧光团分布。这样通过一个传统的二维扫描，就可以得到一个三维的阳样品分布。

国产掺镱双包层光纤的激光特性

采用MCVD方法研发了掺镱双包层光纤，并对其结构特性、荧光特性和激光特性进行了测试和研究。其D形内包层尺寸为400／450μm，数值孔径为0．36，纤芯直径约为16μm，数值孔径约为0．18。荧光谱线的范围为1000-1140nm，1030nm处的峰宽大于50nm。采用大功率激光二极管单端泵浦6m长的双包层光纤，在泵浦人纤功率为61W时，获得了32W的激光输出，斜率效率为64％。该光纤在高功率处未发现饱和现象，通过优化光纤参数与泵浦方式还可以提高转化效率和输出功率。实验表明该光纤可以取代进口光纤用作高功率

Intense infrared luminescence in transparent glass-ceramics containing beta-Ga2O3 : Ni2+ nanocrystals

Transparent glass-ceramics containing beta-Ga2O3:Ni2+ nanocrystals were synthesized and characterized by X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy. Intense broad-band luminescence centering at 1200 nm was observed when the sample was excited by a diode laser at 980 nm. The room-temperature fluorescent lifetime was 665 mu s, which is longer than the Ni2+-doped ZnAl2O4 and LiGa5O8 glass-ceramics and is also comparable to the Ni2+-doped LiGa5O8 single crystal. The intense infrared luminescence with long fluorescent lifetime may be ascribed to the high crystal field hold by Ni2+ and the moderate lattice phonon energy of beta-Ga2O3. The excellent optical properties of this novel material indicate that it might be a promising candidate for broad-band amplifiers and room-temperature tunable lasers.

退火对Si（111）衬底上ZnO薄膜的结构和发光特性的影响

采用磁控溅射法在硅（111）衬底上制备了C轴高度取向的ZnO薄膜，并研究了退火温度和氧气气氛对ZnO薄膜晶体质量、晶粒度大小和光致发光谱的影响。X射线衍射表明，所有薄膜均为高度C轴择优取向，当退火温度低于900℃时，随着退火温度的升高，薄膜的取向性和结晶度都明显提高。室温下对ZnO薄膜进行了光谱分析，退火后的样品均可观测到明显的紫光发射。在一定的退火温度范围内，还可以观测到明显的紫外双峰。空气中退火的样品，当退火温度达到或高于600℃还可观测到绿光发射。实验结果表明，发光峰强度随退火温度和氧气气氛不同而不

飞秒激光相干场诱导材料功能微结构

飞秒激光在整个脉冲宽度内具有极好的相干性，因而当从同一光束分出的两束或两束以上的光束时间与空间上实现相互叠加时将会形成强度周期性调制的电磁场．这种周期调制的电磁场与材料产生相互作用，能诱导出相应的周期微结构．最近通过两束或两束以上飞秒激光干涉诱导功能微结构得到了广泛研究．文章综合了国内外飞秒激光研究小组在干涉诱导微结构方面的一些最新成果以及作者在这方面开展的工作，对飞秒激光干涉技术的原理及其在诱导微结构方面的应用进行了介绍．