Simulation of an apodizer's effect for high-density optical storage

The effect of an apodizer with two parallel taper refractive surfaces is theoretically investigated for high-density optical storage. The apodizer may modulate an incident Gaussian beam into an annular beam. Simulation shows that with the increasing inner radius of the modulated beam, the focal spot shrinks obviously. The depolarization effect gets strong simultaneously, which induces the circular symmetry loss of the focal spot. In this process, pattern density of the orthogonal and longitudinal diffractive fields increases remarkably.

A novel polarization modulator for a Moire system with grating imaging

A polarization modulator based on splitting with a Savart plate and rotation of an analyzer for a moire system with grating imaging is presented, and its modulation principle is analyzed. The polarization modulator is simple and achromatic. It is composed of a polarizer, a Savart plate, and an analyzer. The polarizer and the Savart plate are placed in front of the index grating to split the image of the scale grating in the moire system. The analyzer is placed behind the grating and rotated to realize the modulation of the moire signal. The analyzer can be rotated either continually with high speed or step by step with low speed to form different modulation modes. The polarization modulator makes the moire system insensitive to the change of initial intensity. In experiments, we verified the usefulness of the polarization modulator.

新核素~(263)Hs,~(260)Bh及其α衰变链上核素的半衰期

运用推广的液滴模型(GLDM)并结合量子力学中的WKB方法计算了新核素~(263)Hs和~(260)Bh及其α衰变链上各核素的势垒贯穿概率,对该链上各原子核的α衰变半衰期进行了研究。计算结果表明:利用推广的液滴模型结合WKB方法计算出的α衰变半衰期可以很好地符合在超重核区的实验值,验证了推广的液滴模型在超重核区的适用性,能够很好地描述超重核的α衰变。同时,计算表明新核素~(260)Bh和~(263)Hs的合成及其半衰期的测量是可靠的。

Nanostructure of nacre and its mechanical effects

A type of nanostructure in the organic matrix interfaces of nacre, which is referred to as mineral bridge in the biomineralization, is directly observed with a transmission electron microscope. It is showed that the existence of mineral bridges in nacre i

Ga1-xMnxSb grown on GaSb substrate by liquid phase epitaxy

The Gal(1-x)Mn(x)Sb epilayer was prepared on the n-type GaSb substrate by liquid phase epitaxy. The structure of the Gal(1-x)Mn(x)Sb epilayer was analyzed by double-crystal X-ray diffraction. From the difference of the lattice constant between the GaSb substrate and the Ga1-xMnxSb epilayer, the Mn content in the Ga1-xMnxSb epilayer were calculated as x = 0.016. The elemental composition of Ga1-xMnxSb epilayer was analyzed by energy dispersive spectrometer. The carrier concentration was obtained by Hall measurement. The hole concentration in the Ga1-xMnxSb epilayer is 4.06 x 10(19)cm(-3). It indicates that most of the Mn atoms in Ga1-xMnxSb take the site of Ga, and play a role of acceptors. The current-voltage curve of the Ga1-xMnxSb/GaSb heterostructure was measured, and the rectifying effect is obvious. (C) 2003 Elsevier B.V. All rights reserved.

(Ga, Gd, As) film growth on GaAs substrate by low-energy ion-beam deposit

(Ga, Gd, As) film was fabricated by the mass-analyzed dual ion-beam epitaxy system with the energy of 1000 eV at room temperature. There was no new peak found except GaAs substrate peaks (0 0 2) and (0 0 4) by X-ray diffraction. Rocking curves were measured for symmetric (0 0 4) reflections to further yield the lattice mismatch information by employing double-crystal X-ray diffraction. The element distributions vary so much due to the ion dose difference from AES depth profiles. The sample surface morphology indicates oxidizing layer roughness is also relative to the Gd ion dose, which leads to islandlike feature appearing on the high-dose sample. One sample shows ferromagnetic behavior at room temperature. (C) 2003 Elsevier B.V. All rights reserved.

Microstructure and nanomechanical properties of the wing membrane of dragonfly

Detailed investigations on the microstructure and the mechanical properties of the wing membrane of the dragonfly were carried out. It was found that in the direction of the thickness the membrane was divided into three layers rather than as traditionally considered as a single entity, and on the surfaces the membrane displayed a random distribution rough microstructure that was composed of numerous nanometer scale columns coated by the cuticle wax secreted. The characteristics of the surfaces were accurately measured and a statistical radial distribution function of the columns was presented to describe the structural properties of the surfaces. Based on the surface microstructure, the mechanical properties of the membranes taken separately from the wings of living and dead dragonflies were investigated by the nanoindentation technique. The Young's moduli obtained here are approximately two times greater than the previous result, and the reasons that yield the difference are discussed. (C) 2007 Elsevier B.V. All rights reserved.

等离子体反应器流场、温度场和浓度场的参数研究

文献[3,4]表述了描述等离子CVD化学反应器流场的数学物理模型,并利用Patankar方法对冷热流场作了求解。本文在此基础上就影响反应器流场、温度场和浓度场的有关参数作了理论研究。所研究的问题有:冷热流场的差别,喷射环缝密度和主流旋转速度对流动的影响。所得结果清楚地表明:这些参数的选择对反应器的性能有着不同程度的影响,而有些影响则是本质的。

分枝裂纹的应力强度因子计算

<正> 一、问题的提出 如图1所示,主裂纹与分枝裂纹的长度分别为r_1,r_2.分枝角为γ。利用已有的保角函数,■可将z平面(物理平面)上裂纹外区域,映射到ζ平面(映象平面)上单位圆外区域。并把裂纹的顶点及折点A,B,O_1、O_2分别映射成ζ平面上的γ_1,γ_2,σ_1,σ_2。

不稳定腔的本征值与本征函数

本文证明了不稳定谐振腔的本征值与本征函数的存在性,并证明了不稳定腔的本征值与本征函数组成可数的无穷序列;同时,指出了文献[1]所提出的ε近似本征值与δ近似本征函数的概念并不能真实反映实际不稳定谐振腔的损失与场分布,并指出了有限镜面不稳定谐振腔是具有选模特性的.

Asymmetric structure of an isolated flux arch

This paper extends two-dimensional model of symmetric magnetostatic flux arches confined in stratified atmospheres (Zhang and Hu, 1992, 1993) to asymmetric models. Numerical results show that the flux structure is influenced greatly by the boundary condition of magnetic field, the force-free factor, the atmospheric pressure distribution and the position of footpoints (especially the width ratio of outlet to entrance, which differs from symmetric case).

采动影响下覆岩垮落过程的数值模拟

应用岩层破断过程分析SFPA2D系统 ,分析了采动影响下覆岩破坏的动态发展过程。数值模拟再现了上覆岩层离层、弯曲、沉降、开裂直至冒落的全过程 ,以及采动工作面推进过程中逐步演化的应力场和应变场。根据数值模拟的结果 ,初步探讨了覆岩破断机理 ,指出覆岩的破断特征受分步开挖引起的应力重新分布及其损伤积累以及岩梁的非均质性的影响。

适用于裂解制造乙烯的气体动力学加热方法

对乙烷裂解制造乙烯的非平衡过程进行了分析，为了获得高的乙烯产率，需准确控制裂解停留时间并提高裂解反应温度。探讨了目前工业生产中普遍采用的管式裂解炉的特性及局限。这种管式裂解炉的性能虽已接近完善，但仍不能满足裂解工艺需求。对几种利用激波控制加热方法生产乙烯的发明及其不足进行了评述。提出新颖的反向超声速射流混合加热方法。该方法能满足裂解制造乙烯的要求。

探针移动速度对等离子体射流热流密度测量结果的影响

采用自行研制的中心嵌有铜柱感应件的小尺寸杆状热流探针,在低扰动条件下,对射入大气环境的纯氩层流等离子体射流传向铜探头表面的热流密度进行了动态测量。结果表明,在射流最高温度16500 K、最大轴向速度850 m/s、探针垂直于射流流动方向的移动速度130～260 mm/s的实验参数范围内,随着探针移动速度的提高,测得的热流密度值减小;射流温度和速度越高,探针移动速度对热流密度测量值的影响越大。