Two-dimensional relativistic electromagnetic dromion-like soliton in a cold transparent plasma

By using a standard multiple scale method, a Davey--Stewartson (DS) equation has been derived and also applied to a multi-dimensional analytical investigation on the interaction of an ultra-intense laser pulse with a cold unmagnetized transparent electron-ion plasma. The regions of instability are found by considering the modulation instability of a plane wave solution of the DS equation. The DS equation is just of the Davey--Stewartson 1 (DS1) type and admits a dromion solution, i.e. a two-dimensional (2D) dromion soliton decaying exponentially in all spatial directions. A 2D relativistic electromagnetic dromion-like soliton (2D REDLS) is derived for a vector potential.     

Relativistic Electromagnetic Solitary Wave in a Cylindrical Magnetized Plasma

In the presence of an applied static and uniform magnetic field, a cylindrical Kadomtsev-Petviashivili equation is derived for a relativistic electromagnetic solitary wave propagating in collisionless plasma consisting electrons, positrons, and ions in the case of weak relativistic limit. This equation is solved in a stationary frame to obtain explicit expression for the velocity, amplitude and width of solitons. The amplitude of the solitary wave has a maximum value at a critical αc of the ratio of the ion equilibrium density to the electron one, and it increases as the applied magnetic field becomes larger.     

大学物理实验课反溯教学方法研究

为促进新形势下的“大学物理实验”课程体系改革，推动“高素质、创新型”人才培养朝新方向、高水平前进，北京科技大学“大学物理实验课反溯教学方法研究”课题组提出了物理实验课反溯教学方法，将现代科技的最新发展引入课程，对反溯教学方法进行了探索。课题组从实验现象出发，引导学生反溯基本物理学概念、原理和现象，并相应组织编排物理实验内容，激发学生的探索欲和创造欲，全面提升学生的学习兴趣和学习能力。课题组从实验室建设、新教材建设、新实验编排、本科生科技创新、实验课程与最新科研项目结合等多个角度出发，对“大学物理实验”课程体系进行了全面深化，促进学生变“要我学”为“我要学”,并取得了一系列教学成果。     

Relativistic degenerate effects of electrons and positrons on modulational instability of quantum ion acoustic waves in dense plasmas with two polarity ions

The nonlinear propagation of quantum ion acoustic wave(QIAW) is investigated in a four-component plasma composed of warm classical positive ions and negative ions,as well as inertialess relativistically degenerate electrons and positrons.A nonlinear Schrodinger equation is derived by using the reductive perturbation method,which governs the dynamics of QIAW packets.The modulation instability analysis of QIAWs is considered based on the typical parameters of the white dwarf.The results exhibit that both in the weakly relativistic limit and in the ultrarelativistic limit,the modulational instability regions are sensitively dependent on the ratios of temperature and number density of negative ions to those of positive ions respectively,and on the relativistically degenerate effect as well.     

结合单目视觉成像和深度测量的行为检测研究

人体行为自动检测技术易受成像角度、环境因素的影响,造成检测准确性下滑,结合单目视觉和深度传感器提出了一种新的行为检测技术.首先筛选出人体行为相关的关键帧,以解决行为速度不统一的问题;结合卷积神经网络特征和幅度直方图作为行为描述符;利用对抗网络实现人体行为的域适应迁移学习,解决单目视觉成像角度偏差的问题.在公开的行为检测...     

Site preference and thermodynamic properties of R3Ni13-xCoxB2（R=Y,Nd and Sm）

This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2(R=Y,Nd and Sm) with Nd 3 Ni 13 B 2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials.The space group remains unchanged upon substitution of Co for Ni in R3Ni13-xCoxB2 and the calculated lattice constants are found to agree with reports in literatures.The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g,4h and 6i.Moreover,the total and partial phonon densities of states are first evaluated for the R 3 Ni 13 B 2 compounds with the hexagonal Nd 3 Ni 13 B 2-type structure.