不同功率下无工质微波推力器的推力预估

基于经典电动力学理论,从麦克斯韦方程组和麦克斯韦张量出发,推导出无工质微波推力器的推力计算方程. 应用有限元分析软件,计算了特定谐振模式下的特定圆台谐振腔在不同功率条件下的电磁场分布;根据推导出的理论计算公式,计算了不同功率条件下推力器的总推力. 计算结果表明:推力与功率成正比,而且磁场力决定着总推力的大小;圆台谐振腔消耗20–200 W电磁波功率时所产生的推力在20–250 mN范围内. 关键词： 电磁波 麦克斯韦张量     

晶粒尺寸对气相沉积薄膜磁取向生长的影响研究

为了研究强磁场下薄膜取向生长规律,采用真空蒸发气相沉积法分别制备了不同磁场方向生长的Zn和Bi薄膜.XRD结果发现磁化率差异较小的Zn薄膜在4T时产生了明显的取向生长,而磁化率差异较大的Bi薄膜在5T磁场强度还没有发生取向生长.SEM结果显示Zn薄膜和Bi薄膜晶粒尺寸上有明显的差别,利用Zn薄膜在4T磁场下的取向建立晶粒尺寸和取向生长的对应关系,提出薄膜发生取向时晶粒的磁化能须大于热能kT的420倍.薄膜是否发生取向生长取决于三个因素:薄膜单个晶粒的大小V,材料不同晶向的磁化率差异Δ关键词： 强磁场 磁取向 薄膜生长 材料电磁加工     

惯性颗粒所见被动标量统计特性的DNS与模型研究

本文采用DNS方法,对惯性颗粒所见各向同性湍流中具有平均标量梯度的被动标量场统计特性进行了研究。结果表明：惯性对颗粒温度脉动强度,两相温度关联,自相关特性以及颗粒热流与两相交叉热流的统计特性具有明显的影响。在PDF方法的框架下,系统地推导了非等温气固两相流的PDF方程,且基于朗之万随机体系对方程进行了封闭,并利用前面的...     

Electromagnetic radiation from QGP with chromo-magnetic monopoles

We consider the radiation of photons from quarks scattering on color-magnetic monopoles in the Quark-Gluon Plasma. The calculation is performed in the classical, non-relativistic approximation and results are compared to photon emission from Coulomb scattering of quarks, known to provide a significant contribution to the photon emission rates from the QGP. The present study is a first step towards understanding whether this scattering process can give a sizable contribution to dilepton production in heavy-ion collisions.     

基于弱相干态光源的非正交编码被动诱骗态量子密钥分配

基于改造的弱相干态光源,提出了一种非正交编码被动诱骗态量子密钥分配方案.该方案不主动制备诱骗态,而是根据发送端探测器是否响应,将接收端的探测结果分为响应集合和未响应集合,以此分别作为信号态和诱骗态,并利用这两个集合来估计参量和生成密钥.数值仿真表明,非正交编码被动诱骗态方案的密钥生成效率和安全传输距离都优于现有的被动诱骗态方案,且性能非常接近主动无穷诱骗态方案的理论极限值;未响应集合对密钥生成的参与使方案性能免受发送端探测效率的影响,弥补了实际探测器探测效率低下的缺陷;由于不需要主动制备诱骗态,该方案实现非常简单,适用于高速量子密钥分配的场合. 关键词： 量子光学 量子密钥分配 被动诱骗态 密钥生成效率     

线圈炮电枢电磁-热耦合仿真分析

 从麦克斯韦方程组和导热微分方程出发,导出了3维多级感应线圈炮电磁场、温度场分布的基本方程,并以电磁场和温度场有限元分析为基础,建立了3维有限元分析模型,忽略级间的相互影响,多级线圈炮中电枢温升可以等效为多个单级电枢的温升,运用通用有限元分析软件ANSYS的耦合计算流程,对单级感应线圈炮中电枢电磁场和温度场进行仿真。计算中考虑了材料物理参数随温度变化对温度场的影响。仿真结果表明：电枢内的温升主要分布在电枢的外表面和尾部;电枢的温度随着电容器组电压和电容增加而升高,这是因为总能量增大,电枢中涡流也增大,从而电枢的温度升高;电枢的触发位置和速度匹配关系,也会对电枢温升造成很大的影响;电枢的温度随着级数的增加逐渐升高,说明电枢在一定级数后达到了材料的熔点而被破坏。     

Reflection of plane waves by rough surfaces in the sense of Born approximation

The topic of the present paper is the reflection of electromagnetic plane waves by rough surfaces, that is, by smooth and bounded perturbations of planar faces. Moreover, the contrast between the cover material and the substrate beneath the rough surface is supposed to be low. In this case, a modification of Stearns’ formula based on Born approximation and Fourier techniques is derived for a special class of surfaces. This class contains the graphs of functions where the interface function is a radially modulated almost periodic function. For the Born formula to converge, a sufficient and almost necessary condition is given. A further technical condition is defined, which guarantees the existence of the corresponding far field of the Born approximation. This far field contains plane waves, far‐field terms such as those for bounded scatterers, and, additionally, a new type of terms. The derived formulas can be used for the fast numerical computations of far fields and for the statistics of random rough surfaces. Copyright © 2013 John Wiley & Sons, Ltd.     

Alternative methods of producing photoionised plasmas in the laboratory

We present the conceptual design of a new experiment to reproduce the atomic kinetics of astrophysical photoionised plasmas in the laboratory. In particular the problems of the high densities usually found in laboratory experiments and the production of high colour temperature radiation fields are discussed and solutions presented. Following an analytic discussion, which allows one to find a combination of elements, one for the radiation source and one for the element to be photoionized, the proposed experiment is modelled using existing experimental data for the radiation source and a collisional-radiative model to calculate the photoionisation history. The results indicate that this approach is feasible with current experimental parameters and techniques.     

Electromagnetic processes in a χEFT framework

Recently,we have derived a two–nucleon potential and consistent nuclear electromagnetic currents in chiral effective field theory with pions and nucleons as explicit degrees of freedom.The calculation of the currents has been carried out to include N 3 LO corrections,consisting of two–pion exchange and contact contributions.The latter involve unknown low-energy constants (LECs),some of which have been fixed by fitting the np Sand P-wave phase shifts up to 100 MeV lab energies.The remaining LECs entering the current operator are determined so as to reproduce the experimental deuteron and trinucleon magnetic moments,as well as the np cross section.This electromagnetic current operator is utilized to study the nd and n 3 He radiative captures at thermal neutron energies.Here we discuss our results stressing on the important role played by the LECs in reproducing the experimental data.