梯度折射率棒中传播的高斯光束轨迹解析解及其存在条件的讨论

本文提出光束轨迹方程的一般解，导出解析解的存在条件，推广了文献［１］的光线传播理论，文中以一特定梯度折射率棒为例，讨论了高斯光束在棒中的传播特性。     

厄米-双曲余弦-高斯光束的瞄准稳定性

用失调叠加积分的方法 ,对厄米双曲余弦高斯光束的瞄准稳定性作了研究 ,得到了厄米双曲余弦高斯光束失调因子 ηm2 的精确解析公式和近似解析公式 ,并用数值计算了相对横向偏移和相对角向偏移对失调因子ηm2 的影响以及对精确解析公式和近似解析公式的适用范围作了分析和说明。     

基于DFT插值的宽带波束形成器设计

本文提出一种基于DFT插值的宽带波束形成器设计方法。首先推导了具有频率不变波束图的连续线阵的灵敏度函数与离散线列阵加权系数之间的关系；接着给出了基于DFT插值的宽带波束形成器设计的两个步骤：（1）使用窄带波束形成器的设计方法计算在参考频率下基阵的加权系数；（2）根据参考频率下基阵的权系数与其它子带权系数之间的关系，利用DFT插值的方法求出其它子带的加权系数。最后，给出了一个设计实例说明本文方法的有效性。     

Defects in molecular beam epitaxial GaAs grown at low temperatures

We have utilized a variable energy positron beam and infrared transmission spectroscopy to study defects in GaAs epilayers grown at low temperatures (LT-GaAs) by molecular beam epitaxy. We have measured the Doppler broadening of the positron-electron annihilation gamma ray spectra as a function of positron implantation energy. From these measurements, we have obtained results for the depth profiles of Ga monovacancies in unannealed LT-GaAs and Ga monovacancies and arsenic cluster related defects in annealed LT-GaAs. We have also studied the effects of the Si impurities in annealed LT-GaAs. The infrared transmission measurements on unannealed LT-GaAs furnish a broad defect band, related to As antisites, centered at 0.370 eV below the conduction band.     

Investigation of iodine as a donor in MBE grown Hg1−xCdxTe

N-type Hg_1−xCd_xTe layers with x values of 0.3 and 0.7 have been grown by molecular beam epitaxy using iodine in the form of CdI₂ as a dopant. Carrier concentrations up to 1.1 × 10¹⁸ cm⁻³ have been achieved for x = 0.7 and up to 7.6 × 10¹⁷ cm⁻³ for x=0.3. The best low temperature mobilities are 460 cm²/(Vs) and 1.2 × 10⁵ cm²/(Vs) for x=0.7 and x=0.3, respectively. Using CdI₂ as the dopant modulation doped HgTe quantum well structures have been grown. These structures display very pronounced Shubnikov-de Haas oscillations and quantum Hall plateaus. Electron densities in the 2D electron gas in the HgTe quantum well could be varied from 1.9 × 10¹¹ cm⁻² up to 1.4 × 10¹² cm⁻² by adjusting the thicknesses of the spacer and doped layer. Typical mobilities of the 2D electron gas are of the order of 5.0 × 10⁴ cm²/(Vs) with the highest value being 7.8 × 10⁴ cm²/(Vs).     

基于嵌入式计算机和Ethernet的分布式波控系统

介绍一种基于嵌入式计算机和以太网(Ethernet)的相控阵雷达分布式波控系统。整个波控系统以数个嵌入式计算机为核心，通过以太网与雷达的控制计算机通讯。     

离子束引起的在Al／Cr双层薄膜界面处的原子混合

用600keV的Kr~ 离子轰击Al/Cr双层薄膜样品进行界面原子反应及相互混合的研究。实验样品是在单晶硅上蒸镀约500nm厚的铝膜,相继再蒸上所需厚度的铬膜而制成的。轰击剂量为2.0×10~(15)-2.5×10~(16)Kr~ /cm~2。用2.0MeVa粒子对轰击前后的样品进行了卢瑟福背散射(RBS)分析,发现界面处有明显的原子混合存在;当轰击剂量≥1.0×10~(16)Kr~ /cm~2时,RBS谱出现有明显的坪台,经拟合计算和x射线衍射(XRD)测量证实确有化合物Al_(13)Cr_2存在;还分别得到了原子混合量及混合效率与轰击剂量的关系;最后对界面处的原子混合机制进行了讨论。     

A generalized Adadorov theory for anisotropic thin-walled beams

This paper presents a generalized Adadorov theory for anisotropic thin—walled beams. The theory takes account of the shear strain of the middle surface, which exerts a significant influence on the anisotropic thin-walled beams. A new approach is established to solve the governing equations, which have the same form for both open and closed section beams. The numerical examples show that the effects of the shear strain cannot be neglected for this class of beams.This work was part of research project supported by the National Natural Science Foundation of China     

Thermal transformations of selected transition metals oxyhydroxides

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Propagation properties of vectorial elliptical Gaussian beams beyond the paraxial approximation

Starting from the vectorial Rayleigh diffraction integral formula and without using the far-field approximation, a solution of the wave equation beyond the paraxial approximation is found, which represents vectorial non-paraxial elliptical Gaussian beams in free space. The far-field expressions for non-paraxial Gaussian beams and elliptical Gaussian beams can be regarded as special cases treated in this paper. Some basic propagation properties of vectorial non-paraxial elliptical Gaussian beams, including the irradiance distribution, phase term, beam widths and divergence angles are studied. Numerical results are given and illustrated.