In situ observation of NaBi(WO4)2 dendrite growth and the study on microstructure of solidification

The dendrite growth process of transparent NaBi(WO₄)₂ with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased in the diffusive-convective region. The growth rate of branch had the same change trends as the arm’s. Based on the EPMA-EDS data of solidification structure of quenched NaBi(WO₄)₂ melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface during the growth process. Supported by the National Natural Science Foundation of China (Grant No. 50331040) and the Innovation Funds from Shanghai Institute of Ceramics, Chinese Academy of Sciences (Grant No. SCX0623)     

Synthesis of GaN Nanorods by Ammoniating Ga2O3/ZnO Films

Large quantities of CaN nanorods are successfully synthesized on Si（111） substrates by ammoniating the films of Ga2O3/ZnO at 950℃ in a quartz tube. The structure, morphology and optical properties of the as-prepared CaN nanorods are studied by x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence. The results show that the CaN nanorods have a hexagonal wurtzite structure with lengths of several micrometres and diameters from 80 nm to 300hm, which could supply an attractive potential to harmonically incorporate future GaN optoelectronic devices into Si-based large-scale integrated circuits. The growth mechanism is also briefly discussed.     

单晶和多晶纯铝蠕变过程中的内耗

研究了单晶和多晶纯铝蠕变过程中的低频内耗. 在单晶纯铝中观察到: 内耗在蠕变初期单调下降, 在蠕变第一阶段后期出现了一个显著的时间内耗峰, 在蠕变第二阶段内耗趋于稳定值. 多晶纯铝在类似实验条件下则不出现时间内耗峰. 文中分析了出现时间内耗峰的条件和原因, 认为它是由于蠕变第一阶段中运动位错的阻尼系数逐渐增大所引起的. 文中还从蠕变过程中位错运动的微观机制出发, 推导出了蠕变过程中内耗的表达式, 满意地解释了实验结果. 关键词：     

一种基于粒子滤波的测向定位跟踪算法

基于多站测向定位提供的目标辐射源方位角信息,提出了一种基于粒子滤波的测向定位跟踪算法.该算法采用序贯蒙特卡罗的粒子滤波技术,对目标辐射源方位信息进行粒子滤波融合处理,实现了对机动目标辐射源的无源定位跟踪.仿真实验表明,该算法适用于非线性模型和非高斯噪声的目标跟踪,与传统的基于卡尔曼滤波的多传感器融合跟踪算法相比,定位跟踪更为精确,从而对提高战场电子目标定位跟踪和精确打击具有广泛的应用价值.     

Bivariate Recursive Equations on Excess-of-loss Reinsurance

This paper investigates bivariate recursive equations on excess-of-loss reinsurance. For an insurance portfolio, under the assumptions that the individual claim severity distribution has bounded continuous density and the number of claims belongs to R1 （a, b） family, bivariate recursive equations for the joint distribution of the cedent＇s aggregate claims and the reinsurer＇s aggregate claims are obtained.     

Solvothermal synthesis of TiO2: anatase nanocrystals and rutile nanofibres from TiCl4 in acetone

This work reports a new synthetic approach for single‐phase TiO₂ nanomaterials by solvothermal treatment of titanium tetrachloride in acetone at 80–110 °C. Small, uniform, and yet size‐tunable (5–10 nm) anatase titania nanocrystallites were obtained using a low concentration of TiCl₄ in acetone (i.e., at molar ratios of TiCl₄/acetone ≤ 1:15) in the temperature range of 80–110 °C, while rutile nanofibers were synthesized using a high concentration of TiCl₄ (e.g., TiCl₄/acetone = 1:10) at 110 °C. Copyright © 2007 John Wiley & Sons, Ltd.     

拖曳线列阵用光纤水听器的研究

报道了光纤水听器用于拖曳线列阵的研究结果。在保证光纤水听器声相位灵敏度的前提下, 优化设计了光纤水听器的结构,降低了光纤水听器的加速度灵敏度36dB。实验测得在20-1600Hz 频段,该光纤水听器的相位灵敏度为-162．7dB,频段内灵敏度的起伏为±0．7dB,加速度灵敏度小于-30dB。     

Pascal矩阵与Vandermonde矩阵的关系

EI-Mikkawy M证明了对称Pascal矩阵Q_n和Vlandermonde矩阵V_n之间满足矩阵方程Q_n=T_nV_n,这里T_n是一个随机矩阵。本文证明了随机矩阵T_n能够分解成第一类Stirling矩阵和对角矩阵的乘积,得到了矩阵T_n的元素之间的递推关系,从而回答了EI-Mikkawy M的一个公开问题。同时得到了一些与Stirling数相关的组合恒等式。     

带强迫项变系数组合KdV方程的显式精确解

通过构造两个新的Riccati方程组，推广了Riccati方法，使其具有简洁的形式，丰富和发展了已有的结果，借助Mathematica软件，求出了带强迫项变系数组合KdV方程的一些精确解，包括各种类孤波解、类周期解和变速孤波解. 关键词： Riccati方程组 变系数组合KdV方程 强迫项 类孤波解