“三角形的面积比”在平几证题中的应用

用面积法证几何题,是广大数学教师们所感兴趣的。近年来的许多数学教学报刊也时有探讨。但仍缺乏深入系统的归钠和总结。为此,本文首先给出有关“三角形的面积比”的两个简     

BES桶部簇射计数器性能的宇宙线测试结果

李文报道了用宇宙线带电粒子对北京谱仪(BES)桶部簇射计数器多项性能测试的结果,诸如从1到24层的信号电荷量谱;各层计数管的探测效率;信号电荷量在z向(沿丝方向)的均匀性;电荷分配法的z向分辨率;宇宙线径迹重建等.同时还讨论了该计数器工作气体的选择问题.     

叶栅正交和局部正交贴体网格的生成方法及其应用

一、二维叶栅正交O型网格的系列保角变换法 1.基本变换过程 变换公式和过程见图1。 在由Ω向ω的变换中,为求待定复常数a、b、c,先令ω(z=±∞)=±1,并定义Ω~+=[g(+∞)]~(1/k),Ω~-=[g(—∞)]~(1/k),由变换ω=(a—bΩ/c)/(1—Ω/c)得b=(—2c+Ω~-+Ω~+)/(Ω~+—Ω~-);a=1—(1—b)Ω~+/c;若r_(max)、r_(min)分别表示边界的最大、最小极径,则求常数c的迭代式为     

BaFBr：Eu2＋的发光及电特性研究

采用高温固相反应方法制备的BaFBr：Eu2 粉末样品，未经X射线、真空紫外或紫外光辐照，用波长大于400nm的光激发样品，可观测到Eu2 的390nm发光。样品的电子自旋共振(ESR)谱证实在BaFBr：Eu2 粉末样品的制备过程中，会产生大量的晶格缺陷，分别为电子和空穴陷阱，它们在光激励发光过程中充当不可缺少的角色。本工作将BaFBr：Eu2 粉末制成压片，在其一侧制作两个电极，以研究电阻-电压关系、剩余申压随时间的变化以及与电极材料的关系等电学特性。电特性研究结果也表明，样品中有电子和空穴陷阱两类缺陷，BaFBr：Eu2 的发光，源自激发能通过这两类缺陷向Eu2 的能量传递。     

楔形介质的折射率及楔角的测量

介绍用显微镜测量楔形介质的折射率及楔角的原理和方法，它对物点聚焦而不产生像差和像散，测量精度较高。     

薄夹层界面热弛豫解及其在冲击温度研究中的意义

 对样品/薄夹层/窗口组成的三层介质双界面热传导问题进行求解。在3个不同初温、不同热物性参数及边界条件下，获得了夹层介质中的温度解，给出了界面温度历史随薄层厚度、热扩散系数和介质之间热扩散系数之比的变化规律。从理论分析和实验结果发现，当夹层厚度小于1 μm，热扩散系数大于10^-4 m²/s时，在实验观测的时间内，界面温度历史将很快衰减到一平台，其幅度只由样品、窗口的初温和热扩散系数确定，而与夹层介质的初温、热传导系数无关。     

Femtosecond laser induced defects in various silica glasses

The mechanism of near infrared (IR) focused femtosecond (fs) laser induced defects in silica glasses produced by different methods is systematically investigated through measurements of absorption, fluorescence, and electronic spin resonance (ESR) spectra. The influence of impurities and hydroxyl groups on defects is discussed. The results show that ES silica glasses containing high OH and few defects are much stable under fs laser irradiation. It is also verified that Si E_δ~′center formation has no direct relation with chloride ions.     

Femtosecond laser induced defects in various silica glasses

The mechanism of near infrared (IR) focused femtosecond (fs) laser induced defects in silica glasses produced by different methods is systematically investigated through measurements of absorption,fluorescence, and electronic spin resonance (ESR) spectra. The influence of impurities and hydroxyl groups on defects is discussed. The results show that ES silica glasses containing high OH and few defects are much stable under fs laser irradiation. It is also verified that Si E'δ center formation has no direct relation with chloride ions.