论Whittaker-Shannon抽样定理及其一些推广

The aim of this paper is to present a survey of results concerning the Whittaker-Kotel'nikov-Raabe-Shannon-Someya sampling theorem and its various extensions obtained at Aachen since 1977. This theorem, basic in communication engineering, is often called the cardinal interpolation series theorem in mathematical circles. The interconnections of the sampling theorem (in the setting of Paley-Wiener space) with the theory of Fourier series and integrals are examined. Emphasis is placed upon error analysis, including the aliasing, round-off (or quantization), and time jitter errors. Some new error estimates are given, others are improved; many of the proofs are reduced to a common structure. Both deterministic and probabilistic methods are employed. whereas these results are worked out in detail, the paper also contains a brief discussion of some of the various generalizations.     

ON OSCILLATIONS OF PERTURBED SECOND ORDER DIFFERENTIAL EQUATION

A perturbed second order linear differential eqtuation is considered. A criteria concerning the oscillatory behaviour of solutions of the perturbed equation based on the perturbing function and the solutions of the associated unperturbed equation is given.     

碲镉汞的透射电子显微术和X-射线形貌法研究

用x—射线形貌法和透射电子显微术(以下简称TEM)研究了MCT晶体的缺陷结构。采用这两种技术揭示和鉴别了亚晶粒间界,计算出其倾斜角为10~(-3)弧度。由TEM     

铌酸钾锂单晶的SAW特性

利用曾报导过的有关数据计算了铌酸钾锂(K_(2.98)Li_(1.55)Nb_(5.11)O_(15))单晶的SAW特性。发现有两组传播平面的SAW延时温度系数为零。一组具有较大的机电耦合系数(K_s~2=0.9％),而且功率流角为零。这种单晶的温度稳定性介于Tl_3TaSe_4和ST切石英之间。     

一种由微处理机控制的半导体测量系统

由微处理机控制的仪器在精度、多功能性和分析能力方面均优于其对应的模拟计算部件。本文所介绍的仪器可完成器件制造者在前道工艺监控和器件最终测试时所需要的多种测量和分析工作。本文所讨论的范围包括仪器设计原理、模拟-计算机接口的性能、程序和应用。     

FEATURE SENSITIVITy ANALYSIS IN CHEMICAL KINETICS

THIS paper presents a formulation for analyzing physical fea-tures present in observable concentration profiles.The anal-ysis is confined to time dependent kinetic systems.With thekinetic mechanism described by a vector of input parameters αit is argued that the resultant chemical species concentra-tions are most adequately described in terms of their own na-tural vector of output observable parameters β.Featuresensitivity analysis aims to bridge this natural dichotomy andestablish the relation between the input and output physicalparameters by means of calculating the feature sensitivitycoefficients .These feature sensitivity coefficientsare obtained by a procedure drawing on the computationallyavailable elementary sensitivity coefficients of the con-centration vector c and a numerical fitting of the concentra-tion profiles themselves to a physically acceptable form con-taining the feature parameters.The resultant analysis leadsto a set of linear equations for the feature sensitivity coef-ficients.The technique is illustrated for a kinetic systemexhibiting oscillatory behavior.Various mathematical ques-tions and other approaches to the subject are also mentioned.     

一些染料分子中电子单重激发态的无辐射内转换效率与溶剂粘度的关系

本文应用倍频锁模钕玻璃激光器产生脉冲时间为6微微秒、波长530毫微米的激光脉冲,激发3,3′-diethyl-9-methyl thiacarbocyanino Bromide(DMTCB)等染料分子,然后用时间分辨率为微微秒级的条纹相机测定它们的荧光衰变动力学光谱,以研究这些染料分子的荧光寿命与它们的溶剂粘度之间的关系。     

声光调制器强度伺服系统

本文描述一台用伺服系统控制声光强度调制的、兼作光隔离并能减小幅度噪声的装置。光隔离基本上是理想的,而噪声的减小高达100MHz 左右仍是有效的,在低频时可达到80dB。对声光调制器采用负反馈,将布拉格衍射光强度补偿到一个恒定值,就能达到以上性能。     

单片计算机兼作密码机

对于通信、计算机和银行等行业说来、主要的问题是敏感的数据会遭受非法操纵和全部盗窃。随着数据业务的迅速增长,这种情况已愈来愈严重。由于国家标准局的努力,现在已有了一个用以保护关键性的(但不是机密的)信息的联邦数据加密标准(DES)。这个文件规定了具体的保密方法并定义了标准的数据加密算法。根据法令,DES只适用于不涉及国家安全的政府机关。已经有迹象表明,DES也将广泛用于商业部门。对于诸如资金兑换和债卷与商品交易之类事业,联邦政府可能要求某些非官方数据通信用户保护他们的信息传输。然而,银行界正在采用DES而不用官方敦促。     

哈罗德·尤里和氘的发现

在原子核被认识前，化学、核物理、光谱学和热 力学都在沉睡，唯独发现了重氢．