主动磁回热器端部流动不均匀性影响的数值模拟

本文借助COMSOL多物理场耦合软件构建了二维、瞬态磁制冷模型。利用该模型模拟了两种不同的算例,算例1中回热器与换热器直接连接,算例2中采用渐变段连接,渐变段为普通绝热管道,包含了死容积的影响,两种算例的回热器结构完全相同。通过对比上述算例研究了流体流入回热器时由于管道截面积突变导致的流动不均匀现象对制冷机性能的影响。模拟结果显示,尽管算例2中增加了死容积,但渐变段使流动更加均匀,磁制冷机无负荷温跨由18.65K增大到26.14 K,提升了40.16%;温跨为5 K时,算例2相对于算例1制冷量提高31.57%,COP提高69.85%。因此,回热器两端的截面积突变对磁制冷机的影响不容忽视,本模拟对磁制冷系统结构设计及改进具有重要的借鉴意义。     

基于PEG算法的连续变量量子密钥分发多维数据协调

针对连续变量量子密钥分发系统数据协调过程中效率偏低而造成的密钥量不易提取的问题,本文引入PEG(Progressive-edge-growth)算法构造合适度分布的LDPC校验矩阵,译码时采用LLR-BP译码算法。仿真结果表明,相同度分布下PEG方法构造出的校验矩阵比传统Mackay方法构造出的校验矩阵在译码时,能够更快达到收敛,并且在码率为0.5,码长为10~5时,PEG协调方案协调效率达到93.4%,提取到的安全密钥量为5.41 kb/s,信息传输距离为44.5 km。     

Determination of hyperfine structure constants of 5D_(5/2) and 7S_(1/2) states of rubidium in cascade atomic system

We present a method to precisely determine the hyperfine structure constants of the rubidium 5D_(5/2) and 7S_(1/2) states in a cascade atomic system. The probe laser is coupled to the 5S_(1/2)→ 5P_(3/2) hyperfine transition, while the coupling laser is scanned over the 5P_(3/2)→ 5D_(5/2)(7S_(1/2)) transition. The high-resolution double-resonance optical pumping spectra are obtained with two counter-propagating laser beams acting on rubidium vapor. The hyperfine splitting structures are accurately measured by an optical frequency ruler based on the acousto-optic modulator, thus, the magnetic dipole hyperfine coupling constant A and quadrupole coupling constant B are determined. It is of great significance for the atomic hyperfine structure and fundamental physics research.     

感悟同课异构和学案导学

1 感悟同课异构 所谓"同课异构",就是指针对相同的课题,同一个教学内容,采用不同的构思、不同的教学方法、不同的设计风格、不同的实施途径,达到同样的效果.这里的"同"是指内容的同,最终效果的同,即起点与终点的同,而这里的"异"是指方法、途径等具体过程的不同.     

50 km无特征源的测量设备无关量子密钥分发实验

测量设备无关量子密钥分发协议可以免疫所有测量端的漏洞，极大地推进量子保密通信的实用化进程。美中不足的是，该协议依然对源端有极强的安全性假设。源端设备的非完美性同样会留下多种侧信道，从而威胁系统的实际安全性。针对此问题，提出无特征源测量设备无关量子密钥分发协议。该协议在量子态制备不完美的情况下依然可以提取出安全的密钥，是理论无条件安全性与实际安全性的完美结合。通过三强度诱骗态方法以及自行研制的Sagnac-Asymmetric-Mach-Zehnder编码结构，成功搭建无特征源的测量设备无关量子密钥分发系统，并在长为50.4 km的光纤信道和25 MHz的系统重复频率下达到1.91×10^-6的安全密钥分发速率。     

基于三波段光学成像系统的地物辐亮度系数测量

为了对地面目标的辐亮度系数进行测量,研制了一套包含紫外、可见光和近红外三个波段的光学成像系统,用积分球对其辐亮度响应进行标定,得到辐亮度与图像灰度值和探测器积分时间的拟合方程。提出了一种地面目标辐亮度系数测量方法,采用两块不同辐亮度系数的漫反射板作为参照物,建立辐亮度方程组,最终求解得到的目标辐亮度系数表达式中将不含气象参数项。利用研制的三波段光学成像系统,对绿草地的辐亮度系数进行测量,使用辐亮度系数分别为0.99、0.50、0.20、0.10的四块漫反射板,测得草地的紫外、可见光和近红外波段的辐亮度系数分别为0.070、0.184和0.429。     

关于一类内交换群边传递的图

本文所指的图是有限的、单的、无向的且无孤立点,p是素数.G=〈a,b|a~(p~α)=b~(p~β)=c~p=1,[b,a]=c,[a,c]=[b,c]=1〉(α≥β,(α,β,p)≠(1,1,2))是一类内交换p-群.进一步获得了G的性质和关于G-边传递的图的完全分类.     

基于STC89C52单片机测量管道长度

采用STC89C52单片机,利用声音在管道内形成驻波,通过测量驻波发生时的共振频率,进而求得管道长度.文中对单片机实现的系统硬件结构、软件设计作了具体的说明,并给出了几个测量实例.     

NANOINDENTATION OF THIN-FILM-SUBSTRATE SYSTEM： DETERMINATION OF FILM HARDNESS AND YOUNG’S MODULUS

In the present paper, the hardness and Young‘s modulus of film-substrate systems are determined by means of nanoindentation experiments and modified models. Aluminum film and two kinds of substrates, i.e. glass and silicon, are studied. Nanoindentation XP Ⅱ and continuous stiffness mode are used during the experiments. In order to avoid the influence of the Oliver and Pharr method used in the experiments, the experiment data are analyzed with the constant Young‘s modulus assumption and the equal hardness assumption. The volume fraction model (CZ model) proposed by Fabes et al. (1992) is used and modified to analyze the measured hardness. The method proposed by Doerner and Nix (DN formula) (1986) is modified to analyze the measured Young‘s modulus. Two kinds of modified empirical formula are used to predict the present experiment results and those in the literature, which include the results of two kinds of systems, i.e., a soft film on a hard substrate and a hard film on a soft substrate. In the modified CZ model, the indentation influence angle, φ, is considered as a relevant physical parameter, which embodies the effects of the indenter tip radius, pile-up or sink-in phenomena and deformation of film and substrate.     

正态和非正态分布下结构系统的可靠性分析

本文在分析现有计算方法的基础上,提出了适合于多种结构系统可靠性分析的五种评价衡准.在失效概率的计算过程中,考虑了多种分布形式及随机变量间、失效形式间的相关性,从而为结构系统的最优可靠性设计提供了可靠的设计依据。