Theory Study of the Adsorption of Hydrocyanic Acid onto Small Silver Clusters

Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2 ~Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C–N and C–H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

一种模拟动边界绕流的锐利界面浸入边界法

When the structural wall moves over a fixed grid, the structure coverage will change, resulting in many dead and emerging elements. To avoid the influence of malformation and reconstruction of body-fitted grids on the calculation efficiency and accuracy of the fluid-structure interaction problems with coupled boundary movement on the fixed grid, an improved numerical method for describing the interaction between an immersed rigid body and fluid based on a sharp-interface is proposed. In this method, both the fluid and solid are regarded as pure fluid domains in the whole computational domain, and the solid boundary is divided into several Lagrangian grid points. The flow parameter or velocity is reconstructed by interpolation at the interface element, which is then directly used as the boundary condition of the flow field, thus reflecting the influence of the wall boundary conditions. The method constructs the calculation structure of “virtual point, force point and vertical foot point”, and the velocity of the virtual point is obtained by bilinear interpolation. Then, the velocity of the force point is calculated by forcing the solid boundary to meet the no-slip condition, and the equations of the coupling system based on the immersion boundary method are finally solved to realize the numerical simulation of the flow with a complex moving boundary. The numerical program for this immersed boundary method is established using C++, then the accuracy and reliability of the proposed method are validated by comparison with the literature and experimental results of the basic numerical example of flow around a cylinder. Furthermore, the effects of the structural shape and the angle of attack on the trailing vortex structure, the vortex shedding frequency, and the lift/ coefficient characteristics of the flow around the elliptical cylinder have been analyzed. The anti-symmetric S-type, “P+S” Ⅰ-type and “P+S” Ⅱ-type trailing vortex shedding modes, as well as the variation laws of the vortex structure size, vortex shedding frequency and lift-drag coefficients ratio with axis ratio and angle of attack, are captured. The critical angle of attack (25°) corresponding to the maximum lift-drag ratio is determined as 25°.     

NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-（4-ethoxyphenyl） thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-(4- ethoxyphenyl)thiophene (C16H12N2OS) are calculated at the HF/6-31++G(d,p) and B3LYP/6- 311++G(d,p) levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed. The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.     

检测低通滤波器插入损耗的组合系统

文章介绍了用示波器和信号发器搭配成的检测低通滤波器插入损耗的组合系统。列举了该系统对典型低通滤波器插入损耗的检测结果。     

基于非线性晶体及H(a)nsch-Couillaud技术的激光-环形腔频率锁定技术研究

基于H(a)nsch-Couillaud(H-C)频率锁定技术,通过理论计算得到了用于实现激光到环形腔频率锁定的误差信号,并在实验上利用1583 nm激光与腔内含有KTP晶体的蝶形环形腔对激光到环形腔的频率锁定进行了实验研究,理论结果与实验结果相符.该方案与传统方法相比,大大简化了实验装置,而且操作方便灵活,可以广泛地...     

高温烧蚀初始印记及其发展的研究

直接驱动惯性约束聚变（ICF）中，高温烧蚀初始印记（Imprint）产生的密度调制经过瑞和泰勒（RT）不稳定性发展得到放大，会破坏对称压缩，降低聚变增益，甚至导致点火失败。为此，从实验上研究了调制深度约为1／5的正弦调制激光作用厚CH靶（驱动激光结束时刻，靶背未开始移动）时的Imprint及其发展情况，并进行了初步的模拟计算分析。     

High-Current Multi-Finger Mesa InGaAs/InP DHBTs

Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors （DHBTs） are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the mutual thermal interaction between the fingers. The Kirk current can be as high as 150mA for four-finger DHBT. No degradation of the peak of the current gain cutoff frequency ft is found for multi-finger DHBTs. The peak of the maximum oscillation frequency fmax decreases with an increase of nf due to the increasing parasitic resistance of the base. The results are very helpful for applications of the common-base DHBTs in power amplifiers operating at very high frequencies.     

Analytical Solitary Wave Solutions to a （3＋1）-Dimensional Gross-Pitaevskii Equation with Variable Coefficients

A （3＋1）-dimensional Gross-Pitaevskii （GP） equation with time variable coefficients is considered, and is transformed into a standard nonlinear Schrodinger （NLS） equation. Exact solutions of the （3＋1）D GP equation are constructed via those of the NLS equation. By applying specific time-modulated nonlinearities, dispersions, and potentials, the dynamics of the solutions can be controlled. Solitary and periodic wave solutions with snaking and breathing behavior are reported.     

A New 3D Four-Wing Chaotic System with Cubic Nonlinearity and Its Circuit Implementation

A new 3D four-wing smooth autonomous chaotic system in which each equation contains a cubic product term is presented and physically implemented. Spectral analysis shows that the four-wing chaotic attractor has extremely wide frequency bandwidth compared with that of the Lorenz system and other four-wing chaotic systems, which is important in some relevant engineering applications such as secure communications.     

从一道题的错解说弹簧振子

本文对一道高考模拟试卷中引发热议的多项选择题做了详细的分析和深入的讨论.本期同时发表的还有陆天明老师的《对一道双平衡位置振动问题的讨论》.二文各有千秋.