Cerenkov发射线和类星体参量的确定

本文进一步论证,类星体的发射线有可能来自erenkov线状发射机制,并针对样品3C 273完成了L_α观测谱线和理论谱线的拟合。从而定出3C 273的物理参量的估值。平均气体密度为N≈1.8×10¹⁶厘米^-3,平均气体温度为T≈13000K,相对论电子密度则为N_e≈10⁸厘米^-3。     

非线性对流扩散方程的UNO-MMOCAA差分方法

本文把MMOCAA差分方法与UNO插值相结合，提出了求解对流占优扩散问题的UN0—MMOCAA差分方法，它避免了基于高次(≥2)Lagrange插值的MMOCAA差分方法在方程解的陡峭前沿附近产生的振荡．本文通过引入辅助插值算于等方法，给出了非线性UNO—MMOCAA差分格式的误差分析．数值例子表明新格式无振荡。     

基于激光超声的微裂纹检测技术的研究

在固体中利用激光产生超声波 ,可作为超声测量和材料无损检测的一种新方法。介绍了激光超声表面波的产生机理、微裂纹的检测方法及其应用。采用Nd∶YAG脉冲激光器、扩束与聚焦透镜组、PZT探头、数据分析仪等器件设计并构建了一套基于接触式检测方法的激光超声微裂纹检测实验系统。通过对大量实验数据进行处理 ,得出了相应的各种关系曲线 ,说明了线光源产生的超声表面波非常适用于材料表面微裂纹的检测     

低对称性晶场中3d5离子零场劈裂常数的计算

作为文献[4]的自然推广,本文讨论了低对称性(C_4v或D_4h,C_3v或D_3h)晶场中3d⁵离子零场劈裂常数D值的计算。给出D值依赖于Racah参数、晶场参数和自旋-轨道耦合常数ξ的表示式。用于α-Al₂O₃晶体中Fe³⁺,离子D值的计算,结果与实验值能够较好地符合。 关键词：     

DNA-catalyzed polymerization

Native DNA oligomers are shown to be stereoselective catalysts for the polymerization of 5'-amino-3'-acetaldehyde-modified thymidine/adenosine nucleosides through reductive amination. The reaction follows step-growth kinetics to read the encoded sequence and chain-length information in the antiparallel direction. Single mismatches in the template are selected against at a level of >100:1. A method is therefore established to translate biopolymer-encoded information stereoselectively into sequence- and chain-length specific synthetic polymers.     

结型场效应晶体管的光敏特性及其在紫外检测器上的应用

本文通过合理选择输入阻抗,零偏置时的源漏电流(I_DSS)和跨导,可从常规的n沟道耗尽型结型场效应管中,得到高灵敏度的光敏场效应管.与其它光敏器件比较具有下列优点:线性动态范围大,使用照度范围为10^-3—10⁴勒克司;光谱响应范围自紫外至近红外;输出阻抗低,并且具有可直接用于测定吸收值的特点.我们在测量光强度或吸收值时,对一些因素如外偏置电压、跨导对光灵敏度的影响作了讨论.并使用这种新型元件,装置了单波长双光路的紫外检测器,已用于自制的高速液相色谱仪上.     

Energy loss correction for a crystal calorimeter

Material effect of inner-detectors on the performances of the BESⅢ Electromagnetic Calorimeter (EMC)is investigated.The BESⅢ Time-Of-Flight counters(TOF)have been utilized to improve the energy resolution and detection efficiency for photons after a careful energy calibration.A matching algorithm between TOF and EMC energy deposits is developed,and the effects of beam-related background are discussed.The energy resolution is improved and the photon detection efficiency can be increased by the combined measurement of EMC and TOF detectors.     

利用BESⅢ的双层TOF寻找D~0-■混合的研究(英文)

在ψ(3770)处,D0→K-π+是研究D0-■混合的非常理想的衰变道．实验上,良好的K／π识别技术将对寻找D0-■混合过程起着决定性的作用．在BESⅢ实验的物理预研究中,发现利用飞行时间的信息,能够精确测定末态中含有多条带电径迹事例的起始时间,从而可以改善飞行时间计数器的时间分辨率．进一步的研究表明,应用该方法后,BESⅢ双层TOF的时间分辨率从～78ps降到～64ps．按照20fb-1的ψ(3770)数据量进行估算,在95％置信度下,D0-■混合率的上限值可以提高7％左右．     

Polarization Properties of Quantum Cyclotron Radiation

We present a simplified formulae system describing the polarization properties of the quantum cyclotron radiation by a nonrelativistic thermal electron in a very strong magnetic field. In this system, each of the derived quantities, including the Einstein coefficients, the absorption cross sections, and scattering cross sections, as well as the absorption coefficients by plasma, is divided into the perpendicularly and parallelly polarized components. The results, especially the absorption and scattering cross sections of resonant frequency photons, are potentially important in x-ray and γ-ray astronomy, particularly in the study of gamma-ray bursts and pulsars.