Study on lattice vibrational properties and Raman spectra of Bi_2Te_3 based on density-functional perturbation theory

We present a variational density-functional perturbation theory(DFPT) to investigate the lattice dynamics and vibrational properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states(DOS) of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field,atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO–TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.     

Navier-Stokes方程的最小二乘等几何方法

基于Hermite多项式的C¹型单元构造复杂,限制了最小二乘有限元法的应用.引入高阶光滑的非均匀有理B样条作为基函数简化C¹型单元构造,提出求解黏性不可压流动Navier-Stokes方程的最小二乘等几何方法.用Newton法或Picard法对Navier-Stokes方程线性化,用线性化偏微分方程的余量定义最小二乘泛函,导出最小二乘变分方程,用NURBS构造高阶光滑的有限维空间来近似速度场和压力场.计算表明:本文方法计算的二维顶盖驱动流数值解能准确描述流动状况,计算的二维通道内圆柱绕流全局质量损失由最小二乘有限元法的6%降为0.018%,该方法可用于Navier-Stokes方程的求解,并且具有较好的质量守恒性.     

大学物理互动教学研究

通过分析大学物理互动教学的必要性及意义,结合自身的教学实践及兄弟单位的有关经验,探讨了大学物理互动教学的几种模式,认为：大学物理互动教学有利于体现教学以学生为主体的思想,有利于提高学生学习大学物理的积极性及主动性,大学物理互动教学法是一种值得推广的教学方法。     

亂世之中的生命哲學——《庄子·人间世》第三讲

颜回曰:"端而虚,勉而一,则可乎?"曰:"恶!恶可H夫以阳为充孔扬,采色不定,常人之所不违,因案人之所感,以求容与其心,名之日日渐之德不成,而况大德乎!将执而不化,外合而内不訾,其庸讵可乎!"     

冷等离子体提纯硅的速率模型分析

应用反应动力学方法建立基元反应速率方程并按工艺条件进行耦合,得出了以宏观工艺参数表达的提纯速率方程,这种方程便于计算,能指导工艺优化并容易为工程师应用,计算结果与实验数据能较好的吻合。     

激光工作者皮肤体检观察

由于激光具有极高能量和高度聚焦的性能,因此,它必然具有一般光的生物作用,也有一般光所没有的独特的生物作用.为此,我们于1980年2月对广州市部分激光工作者共129人(其中男58人,女71人)进行了皮肤体格检查.检查结果见表.     

Dynamical Lie algebra method for highly excited vibrational state of asymmetric linear tetratomic molecules

The highly excited vibrational states of asymmetric linear tetratomic molecules are studied in the framework of Lie algebra. By using symmetric groupU ₁(4)U ₂(4)⊗U ₃(4), we construct the Hamiltonian that includes not only Casimir operators but also Majorana operators M₁₂, M₁₃ and M₂₃, which are useful for getting potential energy surface and force constants in Lie algebra method. By Lie algebra treatment, we obtain the eigenvalues of the Hamiltonian, and make the concrete calculation for molecule C₂HF.     

广播电视机房设备安装与维护

广播电视机房是电视系统的核心，也是整个网络的心脏，不管是同轴电缆网还是光缆传输网，如果广播电视机房信号处理不好，信号质量不高，线路传输、用户分配系统再优良也无济于事，因此提高广播电视机房信号质量至关重要。广播电视机房信号的优劣是一个综合因素，牵涉到多个环节，既有设备因素又有人为因素，但只要我们抓住主要环节，优质播出将基本上得到保证。