Stability and vibrational properties of the hydrogen atom for p-type AlN doped with group-Ⅱ:a first-principles study

The stability and local vibrational mode (LVM) of hydrogen related p-type AlN have been studied by first-principles calculations based on density functional theory. The stable and metastable microscopic geometries ofgroup-Ⅱ (Be, Mg, Ca, Sr, Ba)-H complexes have been investigated. The calculated results indicate that BCⅡ is the most stable configuration for isolated interstitial H+ and Be-H complexes, while it is ABN,⊥ for Mg-H, Ca-H, Sr-H and BaH complexes. Moreover, the vibrational frequencies and the values ofk and |α| for the H atom with LVM are calculated. Here, the values of k and |α| are used to describe the parameters of the harmonic and anharmonic contributions, re-spectively. The calculated results indicate that the larger the size of the doped ion is, the shorter the N-H bond length is, and the larger the potential energy, the vibrational frequencies, the values of k and |α| are. This implies that the size of the doped ion has an important influence on the vibrational properties of H.     

有机化蒙脱土和纳米粒子对水性聚氨酯的改性作用

针对纳米改性剂在水性聚氨酯改性方面的应用,介绍了水性聚氨酯纳米复合材料的制备方法,总结了近年来在水性聚氨酯纳米改性方面所取得的成就,重点讨论了有机化蒙脱土和纳米粒子SiO_2改性剂在提高水性聚氨酯的耐水性、热稳定性和力学性能方面的突出作用,并展望了今后水性聚氨酯纳米复合材料的发展方向。     

基于Evolutility的工程训练教学管理系统的优化

针对当前高校工程训练教学管理系统页面风格杂乱以及后期维护不便的问题,提出运用最新的Evolutility4.0在原有的基础上对高校工程训练教学管理系统进行优化,使系统能够达到页面简洁统一、操作方便的效果,同时减少后期维护的不便。     

非常规投资项目收益率指标评价研究

非常规投资项目不存在具有真正经济意义的内部收益率 (IRR) ,因此 ,关于非常规投资项目的收益率指标评价研究一直令人关注。文章在综述投资收益率研究的基础上 ,对非常规投资项目外部收益率指标评价进行分析研究     

利用废钢结硬质合金制备杂多酸

探讨了利用稀硫酸和浓硝酸分步处理废TLMW50钢结硬质合金,结合焙烧、浸取、结晶、水解、还原等方法,分离金属成分,制备12-磷钨酸、12-磷钼酸、绿矾、硫酸铬等化学试剂的生产工艺。     

济南市燃气汽车发展对策探讨

1前言近年来,济南市燃气汽车有了一定的发展,对治理汽车空气污染,净化空气,改善环境起到了明显的作用。在发展燃气汽车的过程中,济南市与国内外许多城市一样,社会各方面敏锐地看到了发展燃气汽车市场的前景,表现出了极高的热情,因此,城市燃气汽车如何发展这一问题,已是摆在我们     

用西文BASIC绘图时标注中文字符的方法

介绍了几种在IBM—PC机上采用西文BASIC而无需中文磁盘操作系统支持下,在屏幕上绘制科技图形时如何显示中文字符简单而实用的方法。     

检漏技术在供水管道上的应用

该漏水检测技术采用听音杆、检漏仪和相关仪对地埋供水管道进行泄漏探测 ,最大测试距离可达5 0 0m ,可对泄漏点进行精确定位。文中详细论述了仪器的使用方法和应注意的问题 ,并列举了检测实例     

文字识别中的图象自适应预处理

为了提高文字识别的正确率，本文比较详细地探讨了手写文字图象在归一化、细化过程中存在的复杂的随机变形，提出了一些有特色的自适应性较强的预处理方法来解决诸如手写文字图象的总尺寸与其构成的笔划宽度一般不成正比等难题，我们还研究出比较符合人眼视觉效果的快速自适应细化算法（375字／秒），这些处理的结果能很稳定地保持原始文字的结构信息，为识别手写的汉字、字母、数字带来了方便。     

A Rapid Code Acquisition Scheme for DS/SS Systems

In this paper, we propose a rapid code acquisition scheme for direct-sequence spread-spectrum (DS/SS) system basing on the improved seed accumulation of sequential estimation (ISASE). This method solves the problem that SASE scheme cannot work in the presence of carrier-frequency offset. The mean acquisition time of the ISASE scheme is derived by the generating function flow graph technique, and the tolerance of carrier-frequency offset is obtained in a closed-form expression. The performance of the proposed acquisition scheme is analytically evaluated in terms of the mean acquisition time. Analysis in theory and numerical results show that the proposed scheme yields improvement of the mean acquisition time over the RASE scheme by a factor of 2–15 times for the PN} period more than 255 in normal operating condition. For the important parameter-accumulating number m, we recommend to choose from 5 to 20 through the tradeoff of the tolerance of carrier-frequency offset and acquisition speed. Jiachi Wang was born in September, 1971. He is a Phd candidate in department Electronics and Information Engineering, Huazhong University of Science and Technology. His research areas include spread spectrum and digital communication, and digital signal processing. Xiulin Hu was born in 1945. He is a professor and Phd advisor in department Electronics and Information Engineering, Huazhong University of Science and Technology. His research areas include spread spectrum and digital communication. Yunyu Zhang was born in 1948. She is a professor in department Electronics and Information Engineering, Huazhong University of Science and Technology. Her research areas include software radio and digital communication. Qingyun Dai was born in 1977. She is a Phd candidate in department of Electronics and Information Engineering, Huazhong University of Science and Technology. Her research areas is wireless network.