Physical Properties of III-Antiminodes -- a First Principles Study

A comprehensive first principles study of III-Antimonide binary compounds is hardly found in literature. We report a broad study of structural and electronic properties of boron antimonide （BSb）, aluminium antimonide （AlSb）, gallium antimonide （GaSb） and indium antimonide （InSb） in zineblende phase based on density functional theory （DFT）. Our calculations are based on Full-PotentiM Lineaxized Augmented Plane wave plus local orbitals （FP- L（APWq-lo）） method. Different forms of exchange-correlation energy functional and corresponding potential are employed for structural and electronic properties. Our computed results for lattice parameters, bulk moduli, their pressure derivatives, and cohesive energy are consistent with the available experimental data. Boron antimonide is found to be the hardest compound of this group. For band structure calculations, in addition to LDA and GGA, we used GGA-EV, an approximation employed by Engel and Vosko. The band gap results with GGA-EV are of significant improvement over the earlier work.     

半线性非一致椭圆方程的局部最大值原理及其在Hessian方程上的应用

本文获得了一个半线性散度型非一致椭圆方程的局部最大值原理，并由此导出了Hessian方程解的局部C^1,1估计和一个Bernstein型结果。     

幼儿园珠心算教学方法初探——教师应怎样让孩子从“学会”到“会学”再到“愿学”

<正>在幼儿园开展的珠心算教学活动中,由于受传统教育思想的影响,往往只注重于教师的教,而较少考虑到幼儿的学。在教的过程中又更多地考虑怎样教幼儿学会而较少考虑到怎样教幼儿会学。"学会"和"会学"虽然只是两个字的颠倒,却是两种不同教育观的反映。教幼儿学会是着眼于当前,即孩子具体的认知结果。例如这一节课幼儿学会了多少珠心算的知识,掌握了哪     

铁路隧道基底破坏力学形态的试验研究

针对既有铁路隧道底部病害严重的现状，采用模型试验方法对该问题进行了研究。试验中主要对不同隧道铺底工况进行疲劳试验，以了解不同铺底工况疲劳裂纹的出现时间、扩展情况以及使用寿命等，同时对作用于铺底结构上的压应力及弯应力也进行了测试。试验结果表明，在机车轴重荷载作用下，作用于隧道铺底结构顶面的竖向压应力基本在0．2MPa以内，而铺底底面的弯拉应力一般在0．8MPa以上，铺底结构属于受弯破坏；另外，通过试验得到了20cm厚钢筋混凝土的隧道基底结构更优的结论。在试验成果的基础上，对隧道铺底结构的受力状态及其计算方法进行了探讨。     

THERMAL POST-BUCKLING OF FUNCTIONALLY GRADED MATERIAL TIMOSHENKO BEAMS

Analysis of thermal post-buckling of FGM (Functionally Graded Material) Timoshenko beams subjected to transversely non-uniform temperature rise is presented. By accurately considering the axial extension and transverse shear deformation in the sense of theory of Timoshenko beam, geometrical nonlinear governing equations including seven basic unknown functions for functionally graded beams subjected to mechanical and thermal loads were formulated. In the analysis, it was assumed that the material properties of the beam vary continuously as a power function of the thickness coordinate. By using a shooting method, the obtained nonlinear boundary value problem was numerically solved and thermal buckling and post-buckling response of transversely non-uniformly heated FGM Timoshenko beams with fixed-fixed edges were obtained. Characteristic curves of the buckling deformation of the beam varying with thermal load and the power law index are plotted. The effects of material gradient property on the buckling deformation and critical temperature of beam were discussed in details. The results show that there exists the tension-bend coupling deformation in the uniformly heated beam because of the transversely non-uniform characteristic of materials.     

电位滴定法测定苯乙烯中总醛含量

苯乙烯是一种重要的有机化工原料,主要用于制取树脂、塑料和合成橡胶等,还广泛应用于制药、涂料、纺织等工业,在国民经济中占有重要地位。目前,世界上苯乙烯的生产方法主要有乙苯脱氢法、环氧丙烷-苯乙烯(PO/SM)联产法、热解汽油抽提蒸馏回收法以及丁二烯合成法等。醛是苯乙烯中的主要杂质,其存在会对苯乙烯下游工艺产生影响。因此苯乙烯中总醛含量测定对保证和控制产品质量至关重要。通常采用的方法是盐酸羟胺法。即将盐酸羟胺加入到苯乙烯试样和甲醇的混合液中,经过一段时间反应后以百里酚蓝     

A Monte Carlo Study of Influences on Depletion Force from Another Large Sphere in Colloidal Suspensions

According to the acceptance ratio method, the influences on the depletion interactions between a large sphere and a plate from another closely placed large sphere are studied by Monte Carlo simulation. The numerical results show that both the depletion potential and depletion force are affected by the presence of the closely placed large sphere; the closer the large sphere are placed to them, the larger the influence will be. Furthermore, the influences on the depletion interactions from another large sphere are more sensitive to the angle than to the distance.     

基于数字信号处理的嗓音控制开关(VOX)算法研究

本文提出了一种基于数字谱分析的嗓音控制开关(VOX，Voice—Operated Transmit)的新算法，该算法简单、实用，在某种程度上克服了传统VOX算法的结构复杂、参数难调等局限，对噪声的鲁棒性也较好，而且易于用数字信号处理实现。首先利用信号功率谱二次处理，提取出语音的平均幅度包络，然后对所得包络进行阈值处理、限幅放大，最后就得到VOX函数。理论分析和计算机模拟结果表明，该算法不仅能较为准确地提取出语音波形的平均幅度包络，而且能工作在较低的信噪比条件下。     

An Efficient and Accurate Spectral Method for Acoustic Scattering in Elliptic Domains

An efficient and accurate method for solving the two-dimensional Helmhokz equation in domains exterior to elongated obstacles is developed in this paper. The method is based on the so called transformed field expansion (TFE) coupled with a spectral-Galerkin solver for elliptical domain using Mathieu functions. Numerical results are presented to show the accuracy and stability of the proposed method.