Density functional theory study on Ni-doped MgnNi (n=1-7) clusters

The possible geometrical and the electronic structures of small MgnNi(n = 1-7) clusters are optimised by the density functional theory with a LANL2DZ basis set.The binding energy,the energy gap,the electron affinity,the dissociation energy and the second difference in energy are calculated and discussed.The properties of Mg n Ni clusters are also discussed when the number of Mg atom increases.     

Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer

We present the growth of GaN epilayer on Si (111) substrate with a single AlGaN interlayer sandwiched between the GaN epilayer and AlN buffer layer by using the metalorganic chemical vapour deposition. The influence of the AlN buffer layer thickness on structural properties of the GaN epilayer has been investigated by scanning electron microscopy, atomic force microscopy, optical microscopy and high-resolution x-ray diffraction. It is found that an AlN buffer layer with the appropriate thickness plays an important role in increasing compressive strain and improving crystal quality during the growth of AlGaN interlayer, which can introduce a more compressive strain into the subsequent grown GaN layer, and reduce the crack density and threading dislocation density in GaN film.     

卫星搭载紫花苜蓿种子的拉曼光谱分析

为了了解卫星搭载对紫花苜蓿种子化学特性的影响,揭示空间诱变机理,文章利用傅里叶变换拉曼光谱法对卫星搭载当代的紫花苜蓿种子进行了研究。结果表明,与地面对照相比,飞行组在358和553 cm-1处的峰强增加,814,1 122,1 531,1 743 cm-1处的峰强降低,通过谱带归属发现,增强的358和553 cm-1分别与DNA和Ca2+有关,降低的4个峰与糖类、脂类有关。这说明经过卫星搭载后,苜蓿种子的DNA和Ca2+的量出现增加趋势,糖类与脂类的量出现降低趋势。其可能原因是(1)种子主动修复诱变产生的DNA损伤时,消耗部分贮存能量所致;(2)空间飞行过程中的超重导致种子细胞内的Ca2+ 浓度升高;(3)飞行因子导致种子提前萌发,DNA大量合成与复制,种子储藏的能量提前降解消耗。这一结果将对苜蓿空间诱变机理研究有重要参考价值。     

Variational iteration method for solving compressible Euler equations

This paper applies the variational iteration method to obtain approximate analytic solutions of compressible Euler equations in gas dynamics.This method is based on the use of Lagrange multiplier for identification of optimal values of parameters in a functional.Using this method,a rapid convergent sequence is produced which converges to the exact solutions of the problem.Numerical results and comparison with other two numerical solutions verify that this method is very convenient and efficient.     

Improving performances of ITO/GaP contact on AlGaInP light-emitting diodes

In this paper AlGaInP light emitting diodes with different types of electrodes:Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide (ITO), but also reduces the specific contact resistances between ITO and GaP, which are 1.273×10-6 ·cm2 and 1.743×10-3 ·cm2 between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA.     

最近邻耦合网络的时空混沌同步研究

本文进行了最近邻网络的时空混沌同步研究.以时空混沌系统作为网络的节点,基于Lyapunov稳定性定理,通过确定网络的最大Lyapunov指数,得到了实现网络完全同步的条件.采用Fisher-Kolmogorov时空混沌系统作为网络节点实例进行了仿真模拟,获得了理想的同步效果.进一步研究了有界噪声影响下网络的同步性能,结果显示它具有较强的抗干扰能力.     

薄膜-泡沫复合平面调制靶的制备

利用浇注法制备了具有正弦波调制图纹的溴代聚苯乙烯薄膜,并在此基础上将低密度聚-4-甲基-1-戊烯(PMP)泡沫溶胶浇注在薄膜调制图纹的表面,从而得到了薄膜-泡沫复合平面调制靶样品。较为详细的讨论了具有正弦波调制图纹的复合平面调制靶的制备方法并通过台阶仪、显微镜观测了薄膜表面条纹的起伏以及薄膜-泡沫截面的复合情况,实验结果发现,采用此种方法得到的复合平面调制靶样品,其薄膜厚度、泡沫密度易于控制,薄膜、泡沫调制界面清晰,易于微靶的加工与装配。     

LNG船用超低温球阀的低温应力分析及数值模拟

应用有限元分析软件分别对通径为DN15的LNG船用超低温球阀在超低温条件下的应力进行分析。研究了球阀的阀杆、阀颈、阀盖等部件的应力在低温下的数值。研究结果显示出了球阀在低温下的应力集中部位,并提出了改进措施。为超低温球阀的结构设计提供了理论指导。     

One-dimensional nonparaxial bright solitons and their coherent interactions in Kerr media

<正>The existence of one-dimensional bright Kerr solitons is investigated in Kerr media beyond the paraxial approximation. It is found that a nonparaxial soliton with no less than a minimum dimensionless width of about 0.76 can exist, which corresponds to the real width about a wavelength.Besides,the coherent interactions between two nonparaxial bright solitons in Kerr media are also investigated in detail.It is found that their separation and intensity ratio have great influence on the coherent interaction between these two solitons.Furthermore,the effect of the relative phase difference on the nonparaxial interaction is quite different from that on the paraxial interaction.Periodical breath, merging,repulsion,and energy transferring can be realized separately by choosing an appropriate initial relative phase between the coherent solitons.     

基于二维结构薄膜的偏振选择相位光栅的研究

利用二维结构薄膜构建了具有偏振选择特性的新型相位光栅,借助严格耦合波分析(RCWA)方法计算了光栅各级衍射强度随入射光波长及入射角的变化,发现在垂直入射情况下,波长600—640 nm范围内,相位光栅对横向电学(TE)模主要产生0级衍射,而对横向磁学(TM)模产生±1级衍射,在波长633nm处,0级衍射光的偏振消光比为109.8,±1级衍射光的偏振消光比为334.6.利用时域有限差分方法对这种相位光栅的偏振分束现象进行了模拟,偏振分离角在玻璃基板内可以达到10°左右,最后模拟了入射角为23°时光栅对不同偏