浅埋炸药爆炸动力学研究进展

浅埋炸药爆炸是现代装甲车辆及其乘员的主要威胁。分析和探究浅埋炸药爆炸的作用机理及其影响因素是提升装甲车辆地雷生存能力、保障乘员安全的前提条件和重要基础。综述了目前国内外学者在浅埋炸药爆炸动力学方面的最新研究成果。首先介绍了浅埋爆炸动力学的研究方法,进而梳理了浅埋爆炸毁伤机理及其载荷传递规律。最后,针对本领域中相关研究工作给出了几点建议。     

Effect of size polydispersity on the structural and vibrational characteristics of two-dimensional granular assemblies

Two-dimensional disordered granular assemblies composed of 2048 polydispersed frictionless disks are simulated using the discrete element method. The height of the first peak of the pair correlation function, g1, the local and global gbond orientational parameters lψ6and ψ6, and the fluctuations of these parameters decrease with increasing polydispersity s,implying the transition from a polycrystalline state to an amorphous state in the system. As s increases, the peak position of the boson peak ωBP shifts towards a lower frequency and the intensity of the boson peak D(ωBP)/ωBP increases, indicating that the position and the strength of the boson peak are controlled by the polydispersity of the system. Moreover, the inverse of the boson peak intensity ωBP/D(ωBP), the shear modulus G, and the basin curvature SIS all have a similar dependence on s, implying that the s dependence of the vibrational density of states at low frequencies likely originates from the s dependence of the basin curvature.     

颗粒介质固-流态转变的理论分析及实验研究

颗粒介质由大量离散的颗粒聚集而成,因而与传统固体和流体不同,运动过程中的颗粒介质中可能同时存在多种流态及其相互间复杂的转换过程. 颗粒介质弹性失稳机理、不可恢复应变量化是研究颗粒介质固态和流态及固-流态转变的关键. 在前期建立的双颗粒温度热力学(two-granular-temperature, TGT) 理论基础上,确定了颗粒介质的弹性稳定性条件,建立了不可恢复应变流动法则,搭建了描述颗粒固态-液态及其相互转化的简单模型. 颗粒堆积体坍塌过程是典型的颗粒介质固态和流态及其转变过程,因此本文首先开展了25 167 个陶颗粒堆积体坍塌过程的实验研究,并使用基于TGT 理论的物质点方法和离散元方法对物理实验进行了模拟. 结果表明,模型数值结果与物理实验在颗粒堆坍塌过程中的形态、速度分布等细节上吻合很好,同时也发现了现阶段所使用的物质点方法和TGT 理论的不足. 初步说明TGT 理论可以实现颗粒介质固态和流态,以及状态转变的描述.      

Raman scattering studies on the collapsed phase of CaCo_2As_2

In this work,Raman scattering measurements have been performed on the collapsed phase CaCo_2As_2 crystals.At least 8 Raman modes were observed at room temperature though CaCo_2As_2 is structurally similar to other 122 compounds like BaFe_2As_2.Two Raman modes are assigned to the intrinsic A_(1g)and B_(1g)of this material system respectively.The other ones are considered to originate from the local vibrations relevant to cobalt vacancies.Careful polarized measurements allow us to clearly resolve the four-fold symmetry of the B_(1g)mode,which put strong constraints on possible point group symmetries of the system with Co vacancies.The temperature-dependent measurements demonstrate that the anomalies in both frequency and width of the B_(1g)mode occur around Neel temperature T_N.The anomalies are considered to be related to the gap opening near the magnetic transition.The study may shed light on the structural and magnetic changes and their correlations with superconductivity in 122 systems.     

电子被氩,氪,氙原子散射总截面的光学模型研究

文中基于光学模型势方法，详细分析并改进了一种准自由模型吸收势，把它作为光学模型的虚部，在能量０．１－３００ｅＶ的范围内计算了电子被Ａｒ，Ｋｒ，Ｘｅ原子散射的总截面，计算结果与实验值进行了比较。     

A General Response System Control Method Based on Backstepping Design for Synchronization of Continuous Scalar Chaotic Signal

A general response system control method for synchronization of continuous scalar chaotic signal is presented. The proposed canonical genera/response system can cover most of the well-known chaotic systems. Conversely, each of these chaotic systems can Mso be used to construct the genera/response system. Furthermore, a novel controller of the proposed response system is designed based on backstepping technique, with which the output of the genera/response system and the given continuous chaotic signal can synchronize perfectly. Two numerical examples are given to illustrate the effectiveness of the proposed control method.     

超高压均质技术在鲜榨果蔬汁加工中应用的研究进展北大核心CSCD

鲜榨果蔬汁富含维生素C、酚类等活性物质。超高压均质技术是基于传统均质技术发展起来的一种非热加工技术,压力最高可达400MPa,能在常温或较低温度下达到杀菌、钝酶等效果。将超高压均质技术应用于鲜榨果蔬汁的加工,可最大限度地保留鲜榨果蔬汁的原有品质。综述了超高压均质处理对鲜榨果蔬汁中微生物、酶及品质影响的研究进展,讨论了超高压均质技术在鲜榨果蔬汁加工中的应用前景。     

Stimulated photoluminescence emission and trap states in Si/SiO2 interface formed by irradiation of laser

Stimulated photoluminescence （PL） emission has been observed from an oxide structure of silicon when optically excited by a radiation of 514nm laser. Sharp twin peaks at 694 and 692nm are dominated by stimulated emission, which can be demonstrated by its threshold behaviour and linear transition of emission intensity as a function of pump power. The oxide structure is formed by laser irradiation on silicon and its annealing treatment. A model for explaining the stimulated emission is proposed, in which the trap states of the interface between an oxide of silicon and porous nanocrystal play an important role.     

Electronic structure and spatial inhomogeneity of iron-based superconductor FeS

Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing symmetry.In this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline domains.Unlike FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio calculations.Remarkably,mixed with the 1×1 tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.