The determination of an equivalent elastic modulus for bodies with cracks by boundary element method

The equivalent elastic modulus of cracked bodies with orderly distributed cracks was computed with the boundary element method. A practical self-consistent scheme has been proposed in consideration of the mutual interaction effects of the cracks. The influence of friction coefficients and orientation of cracks has been investigated. Some computational examples have been given, and the results show that the proposed method is adequate and the scheme is efficient.This project is supported by the National Natural Science Foundation of China.     

Binding energies of excitons in ionic quantum well structures

Il Nuovo Cimento D - We have calculated the binding energies of excitons in quantum well structures based on ionic semiconductors by including the electron-hole interactions with the...     

大血管中的血液流动 (一)刚性管情况

本文讨论了血液在大血管中的非定常振荡流动问题,导出了一组血液流动的速度分布、压力分布公式。分析表明,本文公式既适用于入口区域的流动,也适用于远离入口区域的流动;既可描述定常流动,也可描述非定常的振荡流动。数值算例还表明,本文结果不但和已有的理论结果相一致,而且较之简单,并和实验结果相当吻合。     

ZnSe相变、电子结构的第一性原理计算

基于第一性原理平面波赝势(PWP)和广义梯度近似(GGA)方法,对闪锌矿结构(ZB)和岩盐结构(RS)的ZnSe在0—20GPa高压下的几何结构、态密度、能带结构进行了计算研究,分析了闪锌矿结构ZnSe和岩盐结构ZnSe的几何结构.在此基础上,研究了ZnSe的结构相变、弹性常数、成键情况以及相变压强下电子结构的变化机理.结果发现:通过焓相等原理得到的ZB相到RS相的相变压强为15.3GPa,而由弹性常数判据得到的相变压强为11.52GPa,但在9.5GPa左右并没有发现简单立方相的出现;在结构相变过程中,sp3轨道杂化现象并未消除,Zn原子的4s电子在RS相ZnSe的导电性中起主要贡献.     

具有部分超结的新型SiC SBD特性分析

提出了一种具有部分超结（super junction, SJ）结构的新型SiC肖特基二极管,命名为SiC Semi-SJ-SBD结构,通过将常规SBD耐压区分为常规耐压区和超结耐压区来减小导通电阻,改善正向特性.利用二维器件模拟软件MEDICI仿真分析,研究了不同超结深度和厚度时击穿电压(V_B)和比导通电阻(R_on-sp),与常规结构的SBD比较得出,半超结结构可以明显改善SiC肖特基二极管特性,并得到优化的设计方案,选择超结宽度2< 关键词： SiC肖特基二极管 super junction 导通电阻 击穿电压     

DNS study of swirling intensity effect on flow pattern of a circular jet

Abstract  

The figures show the 3D flow pattern of a circular jet with different swirling intensity. Reynolds number is approximately 4300 computed based on the nozzle diameter (d), jet velocity (U), and air fluid property at 1 atm and 300 K. The overall computational domain is set to be 4 × 4 × 12 d in spanwise, height, and streamwise direction. The governing equations are the fully compressible Navier–Stokes equations, firstly differenced by eighth-order explicit scheme and then advanced temporarily by using the fourth-order explicit Runge–Kutta method. 3D characteristics non-reflecting boundary condition including transverse source contribution is imposed on all other boundaries except the inflow boundary handled by assigning fixed profiles of temperature and velocity. To ensure the simulation resolution, here over 16 million grids are employed in sum, combined with a handful of grids located at buffer zones of outflow boundaries. To correctly represent the vortex in the flow field, velocity gradient tensor invariant Q is used here. And ψ refers to the swirling intensity defined as the ratio of tangential momentum to axis momentum. As shown in velocity profile, the flow pattern of the jet changes from a close mode to a totally open mode as ψ increases from 0.4 to 1.5. Accordingly, the recirculation zone gradually moves upstream and backflow velocity is enlarged as well. It is inteseting to found that the obvious drops of the momentums in two shown directions always occur at the same position downstream, no matter how large the ψ value is. Therefore, a momentum compensatory mechanism is expected to exist in the vortex-abundant zone. With the increase of ψ value, the increased strain rate in tangential direction can induce vortex more quickly, intensifying the entrainment and velocity-attenuation, which can be observed in Q value profile.     

Design of dispersive multilayer with particle swarm optimization method

<正>We present a new and efficient method for the design of dispersive multilayer by employing a particle swarm optimization(PSO) technique.Its mathematical background is given and an adaptive PSO is realized with computer code.Two practical designing tasks are solved with this method,and the obtained results are competitive compared with other published structures.The adaptive PSO method demonstrates its merits of fast convergence and powerful global search ability,and could be used as a valuable tool for the optical thin film design.     

Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde

A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0×10⁻³ g ml⁻¹ formaldehyde, netilmicin exhibits a sensitive cathodic peak at −1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton–Robinson buffer (pH 8.7) with a scan rate of 100 mV s⁻¹ after a preconcentration period of 120 s at −1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2×10⁻⁹–1.0×10⁻⁷ g ml⁻¹. The achieved limits of detection and quantitation were 1.0×10⁻¹⁰ and 3.3×10⁻¹⁰ g ml⁻¹ netilmicin, respectively. It was deduced from the experiments that the amine–aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.      

光纤布拉格光栅传感器的一种波长解调方法

光纤布拉格光栅（FBG）经过中心波长解调,可实现对应变、温度等物理量的高精度传感检测．在光纤光栅传感中,如何检测中心波长的微小移位是传感解调的核心问题．为此,文中介绍了一种基于互相关原理的FBG中心波长解调方法．FBG的初始光谱和被调制后的受扰光谱形状相似,只是中心波长产生了漂移,通过对初始光谱与受扰光谱互相关值的解算,即可解调出中心波长的位移量．将实验结果与自相关法、功率加权法和最小二乘法等波长解调方法进行了对比,结果表明互相关方法可以有效地进行中心波长解调．     

Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

We numerically simulate the hydrodynamic interaction of aerosol particles due to the acoustic wake effect under the Oseen flow condition.Attraction is found for two nearby particles with an orientation angle of 0 to 50° with respect to the acoustic field,and weak repulsion is found outside this range.Good agreement is obtained between the numerical results and experiments in the literature.We study the influence of particle size,sound wave frequency and the particle separation.The result shows that the acoustic wake effect plays a significant role in acoustic agglomeration.It could be either the major agglomeration mechanism of monodisperse aerosols or the major refill mechanism for polydisperse aerosols to supplement orthokinetic interaction.