Finite element dynamic analysis of practical bladed discs

The dynamic characteristics of one blade, two discs and one shrouded, bladed disc, having 87 blades, are predicted by the application of the finite element method of analysis. The discs are modelled by using both annular and sector elements. The blades are modelled by means of shell elements. The shrouds are represented by both lumped masses and straight beam elements. The predicted frequencies are compared with experimental results.     

Single-mode optical waveguides fabricated in LiNbO3 by multienergy C implantations

Single-mode waveguides in LiNbO₃ are demonstrated by use of prism coupling method. The waveguides are fabricated by three different energies and single energy C²⁺ implantations at the equal total doses, respectively. Dark modes and propagation loss are measured by use of prism coupling and moving fiber methods, respectively. Damages produced by implantation are measured by RBS/channeling technique. The waveguide structures are investigated in two different implantation cases. The results of analysis indicate that the heavy ion-implanted waveguides are still defined by synergetic characteristics from both the raised-index region and the low-index barrier. The broadened barrier from multienergy implantation is demonstrated to play a significant role in reducing propagation loss.     

薄膜后栅型SnO_2场发射显示器的制备及性能研究

利用光刻、阳极氧化和剥离技术在玻璃基底制备薄膜后栅型场发射阵列,采用丝网印刷技术将一维SnO2纳米发射材料转移至后栅结构的阴极电极上,借助光学显微镜和扫描电镜观测薄膜后栅型场发射阴极阵列,利用ANSYS软件模拟了不同条件下阴极电极附近电子运动轨迹.结果表明,一维SnO2纳米线在阴极电极衬底上分布均匀,电子束斑随着阳压的...     

Influence of Concentration of Vanadium in Zinc Oxide on Structural and Optical Properties with Lower Concentration

ZnO films doped with different vanadium concentrations are deposited onto glass substrates by dc reactive magnetron sputtering using a zinc target doped with vanadium. The vanadium concentrations are examined by energy dispersive spectroscopy （EDS） and the charge state of vanadium in ZnO thin films is characterized by x-ray photoelectron spectroscopy. The results of x-ray diffraction （XRD） show that all the films have a wurtzite structure and grow mainly in the c-axis orientation. The grain size and residual stress in the deposited films are estimated by fitting the XRD results. The optical properties of the films are studied by measuring the transmittance. The optical constants （refractive index and extinction coefficient） and the film thickness are obtained by fitting the transmittance. All the results are discussed in relation with the doping of the vanadium.     

Babinet's principle in the Fraunhofer diffraction by a finite thin wire

The scattered waves by a thin finite wire are evaluated by using the Rayleigh-Sommerfeld integral in the Fraunhofer approximation. The scattered fields by the complementary thin wire are also obtained with the aid of the Babinet's principle. The scattering integrals are evaluated directly. It is shown that Babinet's principle holds excellently for this problem. The scattered fields are examined numerically.     

单轴晶光轴干涉图成因的理论分析

借助于数学工具和一种简单的实验装置,用直观的方法,使理论分析和图形相结合,从理论上解释了单轴晶光轴干涉图的成因,并给出了在白光照射下的干涉花样。搭建了实验光路,结果表明:若用单色光照射,干涉图为明暗相间圆环;若用白光照射,则为一个套一个的环状等色曲线。愈向视域边缘,干涉色级数愈高,等色曲线的数目愈多,密度愈大,表示晶体的双折射率愈大。实验结果与理论分析相吻合。     

基于反转光楔和泽尼克多项式的共形光学设计

采用一对反向旋转的累斯莱棱镜可以实现对目标视场的动态扫描,并应用一对内表面为泽尼克边缘矢高表面的透镜对共形光学整流罩引入的主要像差进行校正,剩余像差则由累斯莱棱镜内表面进行补充校正.设计实例中,通过比较光学系统校正前后的成像质量以验证这种校正方法的有效性.     

Electromagnetic radiation from relativistic positrons reflected at small angles by a solid surface

The spectral, angular and polarization characteristics of the electromagnetic radiation generated by relativistic positrons reflected at small angles by a solid surface are obtained in the dipole approximation of classical electrodynamics. The effects investigated are produced by coherent interaction of the reflected positrons with atomic chains on the solid surface. The interference effects accompanying positron multireflection by two parallel solid surfaces are discussed.     

一维矩形光子晶体中电磁波的传输特性

利用一维矩形光子晶体中电磁波横向受限的条件,推导出电磁波在其中各个模式满足的关系式,从而研究了电磁波各模式的特性.通过色散法研究了电磁波的传输特性随模式量子数和矩形边长的变化规律,得出了一些不同于一维非受限光子晶体的新特征,即一维矩形光子晶体的禁带由模式量子数确定,禁带频率中心和频率宽度与模式量子数和边长有关.     

超音速过流串联双空腔流场的DNS研究

本文采用直接模拟方法对超音速气流过流串联双空腔的流场进行研究,并与单空腔模型对照,分析了马赫数分别为1.5和2.5时双空腔之间的相互作用。结果显示空腔剪切层振荡对全场流动的控制作用,上游空腔对下游空腔中剪切层的运动有加强的趋势,它同时还可降低下游空腔壁面上的声压级;而下游空腔对上游空腔的影响则很微弱。串联双空腔产生的噪声辐射具有明显的方向性,其传播方向受马赫数的影响。     

Hydrogenated amorphous silicon nitride deposited by DC magnetron sputtering

Hydrogenated amorphous silicon nitride thin films are deposited by DC magnetron sputtering in argon, and molecular hydrogen and nitrogen mixture. The samples are characterized by electrical measurements and by optical transmission. The physicochemical structure is studied by FTIR spectrum analysis. The results show that both nitrogen and hydrogen are incorporated. The ratio [N]/[Si] increases with increasing hydrogen partial pressure. The deposited films are used in MIS structures. The capacitance–voltage characteristics are carried out. The deposited samples present a large gap and show a nearly chemical stoichiometric composition.     

Laser ultrasound characterization of chemically prepared nano-structured silver

The ultrasonic properties of nano-structured silver (hereafter nm-Ag) are investigated by the laser ultrasonic technique. The nm-Ag superfine particles with a size of 20 to 27 nanometer (nm) are prepared by using a chemical method. Wafers of nm-Ag are fabricated under different pressing pressures and used as samples. The experimental results show that the ultrasonic velocity and attenuation of nm-Ag prepared by the chemical method depends on the pressing pressures and thus on the relative density. The elastic moduli values of nm-Ag prepared by the chemical method are deduced. The values are lower than those of polycrystalline and single-crystalline Ag. The detailed results, discussions, and comparisons with nm-Ag samples prepared by a physical method are presented. Received: 23 November 1998 / Accepted: 13 September 1999 / Published online: 24 March 2000     

氦原子能级的变分微扰计算

用变分微扰论计算了氦原子1S2S态两个能级的能量.先用单参数变分法计算,再进行二级微扰计算,改进了纯微扰论的结果,得到的能量值与实验数据较好相符.     

弹性波在固-固结构矩形声子晶体中的传输特性

利用一维固-固结构矩形声子晶体中弹性波横向受限的条件,推导出弹性波在其中各个模式满足的关系式,利用它研究了弹性波各模式的特性。并用转移矩阵研究了弹性波的传输特性随模式量子数和边长的变化规律。得出了一些不同于一维固-固结构非受限声子晶体的新特征,即一维矩形声子晶体的禁带由模式量子数确定,禁带的频率中心和频率宽度与模式量子数和边长有关。     

基于可调谐激光的CO监测仪的不确定度评定

采用可调谐二极管激光吸收光谱技术(TDLAS)对CO气体的浓度进行测量,应用整体二次谐波最小二乘法对测量信号的实验数据进行反演处理。基于可调谐二极管激光吸收光谱技术, 对CO在线监测仪测量结果的不确定度来源进行了分析, 采用直接评定法对各种因素引起的不确定度分量、标准不确定度和合成不确定度进行了评定。实验结果表明, 仪器示值引入的不确定度、标准气体浓度定值的不确定度以及环境温度变化和电源电压波动引入的不确定度是影响测量不确定度的主要因素。     

Ge-Sb-Se硫系薄膜制备及光学特性研究

介绍了几种常见的硫系薄膜制备方法, 根据现有实验条件采用热蒸发法和磁控溅射法制备出Ge-Sb-Se三元体系硫系薄膜, 通过台阶仪测试薄膜的厚度和表面粗糙度, 计算出两种制备方法的成膜速率, 并通过X射线光电子能谱测试了两种制备方法所得薄膜与块体靶材组分的差别. 利用Z扫描技术和分光光度计测试了热蒸发法制备所得薄膜的三阶非线性性能和透过光谱, 计算出非线性折射率、非线性吸收系数和薄膜厚度等参数. 结果表明热蒸发法制备Ge-Sb-Se薄膜具有良好的物理结构和光学特性, 在集成光学器件方面很高的应用潜力.     

类锂离子(Z=11～20)1s23p-1s2nd(n=6,7)的跃迁能和振子强度

用全实加关联(FCPC)方法计算类锂离予体系(Z=11～20)1s2nd(n=6,7)态的非相对论能量.相对论及质量极化效应对能量的修正用微扰论计算,量子电动力学(QED)修正利用有效核电荷方法估算.在此基础上计算了1s23p-1s2nd(n=6,7)的跃迁能及振子强度,对现有的关于1s2nd(n=6,7)态的精细结构的实验数据的可靠性提出质疑.     

热释光剂量计监测质子注量

 理论计算了采用热释光剂量计(TLD)监测不同能量(14~32MeV) 的质子注量灵敏度,在35MeV质子加速器上利用TLD对质子注量进行了监测,并将结果与法拉第筒所测注量进行了比较,证明采用TLD监测质子注量的结果是准确的。     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

Analysis of the spatio-temporal scales of laminar premixed flames near equilibrium

The interplay between chemistry and transport is addressed by exploring the coupling between the spatial and temporal scales of one-dimensional laminar premixed combustion in reactive mixtures described by detailed chemical kinetics and multicomponent transport. System dynamics are investigated in the neighbourhood of the equilibrium state; in so doing, the time scales associated with modes of varying wavelength for the complete unsteady, spatially inhomogeneous system are obtained. The results reveal that short wavelength modes are dominated by diffusion-based time scales, and long wavelength modes are dominated by reaction-based time scales. The analysis further identifies critical wavelengths where the effects of reaction and diffusion are balanced, and it is seen that the critical wavelengths are well estimated by classical diffusion theory.