冲击作用下HMX晶体孔洞塌缩热点生成机制的细观数值模拟

热点的形成、点火以及成长过程是理解非均匀炸药冲击起爆的关键.采用离散元法,对冲击作用下含孔洞的HMX晶体进行了细观数值模拟.计算结果表明:在较低冲击作用下,孔洞边缘发生了较大的剪切变形,粘塑性功形成热点;而在较高冲击作用下,孔洞塌缩产生射流,汇聚流动,冲击下游炸药形成热点,并获得了孔洞塌缩和热点生成演化的细观过程.     

高度均一ZnO纳米梭的水热法制备及其性能

以六亚甲基四胺和硝酸锌为原料,采用水热法在90℃条件下反应24h,于Si衬底上制备出一维ZnO纳米梭材料.采用场发射扫描电镜、X射线衍射仪和高分辨透射电镜等方法对样品形貌和晶体结构进行了表征.结果表明,所得ZnO纳米梭形貌一致、尺寸均匀,为六方纤锌矿型结构,具有良好的结晶性能.对ZnO纳米梭的光致发光性能的研究表明,该...     

Analytic soliton solutions of cubic‐quintic Ginzburg‐Landau equation with variable nonlinearity and spectral filtering in fiber lasers

In fiber lasers, the study of the cubic‐quintic complex Ginzburg‐Landau equations (CGLE) has attracted much attention. In this paper, four families (kink solitons, gray solitons, Y‐type solitons and combined solitons) of exact soliton solutions for the variable‐coefficient cubic‐quintic CGLE are obtained via the modified Hirota method. Appropriate parameters are chosen to investigate the properties of solitons. The influences of nonlinearity and spectral filtering effect are discussed in these obtained exact soliton solutions, respectively. Methods to amplify the amplitude and compress the width of solitons are put forward. Numerical simulation with split‐step Fourier method and fourth‐order Runge‐Kutta algorithm are carried out to validate some of the analytic results. Transformation from the variable‐coefficient cubic‐quintic CGLE to the constant coefficients one is proposed. The results obtained may have certain applications in soliton control in fiber lasers, and may have guiding value in experiments in the future.

     

A high‐accuracy complex‐phase method of simulating X‐ray propagation through a multi‐lens system

The propagation of X‐ray waves through an optical system consisting of many X‐ray refractive lenses is considered. For solving the problem for an electromagnetic wave, a finite‐difference method is applied. The error of simulation is analytically estimated and investigated. It was found that a very detailed difference grid is required for reliable and accurate calculations of the propagation of X‐ray waves through a multi‐lens system. The reasons for using a very detailed difference grid are investigated. It was shown that the wave phase becomes a function, very quickly increasing with increasing distance from the optical axis, after the wave has passed through the multi‐lens system. If the phase is a quickly increasing function of the coordinates perpendicular to the optical axis, then the electric field of the wave is a quickly oscillating function of these coordinates, and thus a very detailed difference grid becomes necessary to describe such a wavefield. To avoid this difficulty, an equation for the phase function is proposed as an alternative to the equation of the electric field. This allows reliable and accurate simulations to be carried out when using the multi‐lens system. An equation for the phase function is derived and used for accurate simulations. The numerical error of the suggested method is estimated. It is shown that the equation for the phase function allows efficient simulations to be fulfilled for the multi‐lens system.     

PVDF压电计的动态响应特性及其在橡胶材料SHPB实验中的应用

通过夹心式PVDF(Polyvinylide Fluoride)压电计的动态分离式Hopkinson压杆(SHPB)标定实验,系统地讨论了传感器的动态响应特性,其中包括测量电路、PVDF表面应力集中、压电计的材料及结构特性和同一压电计受多次撞击对测试信号的影响,为PVDF压电计的制作工艺研究提供参考。利用标定好的压电计测试了橡胶材料在SHPB实验中的动态应力均匀过程。结果表明:调节并联电阻值可以提高压电计的传感精度;增大压电计的敏感面积可以减小因应力集中所造成的信号失真;材料的热粘塑性性质、摩擦效应等将使信号振荡幅度偏小;多次撞击对信号的加载与卸载段都将产生影响,但当传感器表面未发生明显损伤时,测试的应力平台平均值与真实信号近似相同。     

Analytical Approach to Fractional Zakharov-Kuznetsov Equations by He＇s Homotopy Perturbation Method

The aim of this paper is to obtain the approximate analytical solution of a fractional Zakharov-Kuznetsov equation by using homotopy perturbation method （HPM）. The fractional derivatives are described in the Caputo sense. Several examples are given and the results are compared to exact solutions. The results reveal that the method is very effective and simple.     

Linear and Nonlinear Optical Properties in Spherical Quantum Dots

We calculate the energy eigenvalues and the sate functions of one-electron Quantum Dot （QD） by using a combination of Quantum Genetic Algorithm （QGA） and Hartre-Fock-Roothaan （HFR） method. The linear and the third-order nonlinear optical absorption coefficients for the 1s-1p, 1p-1d, and 1d-1f transitions are examined as a function of the incident photon energy for three different values of the stoichiometric ratio. The results show that the stoichiometric ratio, impurity, relaxation time, and dot size have great influence on the optical absorption coefficients of QDs.     

Effective Action for Noncommutative U（1） Gauge Theory with Higher Dimensional Terms

In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U（1） gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U（1） gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories.