一种基于移相误差估计的5步移相算法

移相误差是用移相法进行相位测量的主要误差。本文提出一种 5步移相算法 ,分两步进行相位计算 ,首先估计实际步进移相的线性移相误差 ,然后再利用此移相误差估计值计算相位分布。移相误差估计公式和相位计算公式简洁 ,算法简单易行 ,对线性移相误差和二次谐波的敏感度低 ,可基本消除线性移相误差对解调相位的影响。对本文提出的算法进行了仿真研究 ,同时给出了 Hariharan 5步算法、Surrel 6步最小算法的仿真结果。结果表明 :本算法明显优于以上两种算法 ,可基本消除线性移相误差引起的相位偏移。本算法适用于作等步移相的相位测量或移相的标定。     

超导数字计算机

超导数字计算机是下世纪超级机的发展方向 ,它在计算机科学发展的历史上将具有十分重要的意义,文章简要介绍了快速单磁通量子（ＲＳＦＱ）超导计算机研究的发展、ＲＳＦＱ逻辑电路的基本原理、超导计算机的基本结构以及超导数字计算机的展望。     

计算的量子飞跃

利用量子力学的迭加和纠缠等特性进行的量子计算是计算技术的巨大飞跃。它能够比经典计算远为有效地解决一些问题。例如最为著名的Ｓｈｏｒ的算法原则上能够以多项式的时间因子化大的合数,从而使得经典计算机难以计算的这一问题得以解决。文章介绍了至今所发现的主要量子算法的基本原理和步骤,并且概述了量子计算的优越性、现状和发展前景,同时讨论了量子计算在物理学上的应用和意义。     

SrS:Eu与SrS:Eu,Sm中电子陷阱与光存储研究

对SrS:Eu和SrS:Eu,Sm激发初始阶段的荧光上升过程和余辉进行了研究,并进一步考证其中 电子陷阱的属性.通过两种样品和两个阶段的比较,对陷阱数量和深度的变化、量子效率以 及电子俘获和释放、复合过程进行了分析,发现Sm离子并不影响陷阱的数量.利用吸收光谱 方法研究了SrS:Eu,Sm中电子由陷阱能级向导带的跃迁.通过陷阱饱和-倒空吸收谱差,即激 励吸收谱及其强度随Eu,Sm浓度的变化,探讨了掺杂浓度对陷阱浓度和光存储饱和量的影响. 结果表明Sm离子的作用是使陷阱能级加深从而能稳定地储存电子.通过激励吸收谱峰值强度 可确切地比较光存储材料在这方面的性能,并与光激励谱的测量方法作了对照. 关键词： 电子陷阱 光存储 电子俘获 光激励发光     

LINEAR AND NONLINEAR SEMICLASSICAL THEORY OF WHISPERING-GALLERY-MODE MICROSPHERE LASER

A complete whispering-gallery-mode microsphere laser theory is developed, which combines usual laser semiclassical theory with Lorenz-Mie theory. The linear and nonlinear problems of the microsphere lasing are dealt with in the universal mode picture. The threshold condition, average amplitude of the steady state and frequency effect are obtained. A comparison between the theory and experiments is also made.     

THE NONLINEAR SCHR?DINGER EQUATION AND THE CROSS-PHASE MODULATION IN ERBIUM-DOPED FIBER AMPLIFIERS

The nonlinear Schr$\ddot{o}$dinger equation(NLSE) in erbium-doped fiber(EDF) was obtained. The cross-phase modulation (XPM) in the erbium-doped fiber amplifiers (EDFA) was studied based on this NLSE and the rate equations. A more generalized form of the propagation equation in EDFA was obtained which included the phase shifts the EDFA induced. An analytical expression was given to the XPM in the EDFA. It was found that the XPM in the EDFA dose not change very much with the wavelength except at the neighboring wavelengths (around 1531 nm) where the absorption and emission cross-sections of the erbium ions reach their maxima, and the XPMs have opposite signs on the two sides around 1531 nm. Furthermore, it was found that the XPM increases with the increase of the length of EDF.     

分子转动惯量与正烷烃熔沸点的预测

在分子转动模型基础上,以半经验分子轨道（ＡＭ１）方法计算分子的转动惯量及其它结构参数,获得１５个正烷烃的沸点和熔点的多元线性回归方程。其中正烷烃的沸点与短轴转动惯量（ｃ）和碳原子数（ｎ）相关（ｂｐ＝－１４７．－０．０１１８９ｃ＋３６．１７ｎ,Ｒ＝０．９９８５,ＳＤ＝６．９７）,而熔点与分子的长轴转动惯量（ａ）、短轴转动惯量（ｂ,ｃ）及重定向能（Ｅ）相关（ｍｐ＝－２６０．３＋１５．７０ａ＋１９．７４     

The Detection of Defects in Optical Fibers Using a Hybrid Opto-electronic Correlator

A hybrid opto-electronic correlator for detecting defects in optical fibers is proposed. After the light from a He-Ne laser being expanded and filtered it is not collimated but directly passes a Fourier transform lens and illuminates a reference fiber and a test fiber at the same input plane. The Fourier transform spectrum of the two fibers is therefore obtained at the rear focal plane of the lens, where it is sampled via a CCD array connected with a computer through a frame grabber. The computer performs filter, inverse Fourier transform and setting threshold operation on classification. The system is an equivalent of joint transform correlator with a Fourier lens of long focal length. The experiment results for optical fibers having incoordinate defects are presented. The results indicate that the system can be used for fiber defect detection, and has the advantages of high identification, compact configuration, easy adjustment and flexible manipulation.     

Correlation between P chemical shift tensor and local structure in lithium cyclohexaphosphates Li6P6O18·3H2O and Li6P6O18

To understand the surprising behavior between the variations of the P′–P–P″ angles and the correlated variations of the O′–P–O″ ones, two lithium cyclohexaphosphate compounds Li₆P₆O₁₈·3H₂O and Li₆P₆O₁₈ are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P₆O₁₈]⁶⁻ ring anions but with 3m or internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of ⁷Li and ³¹P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for ⁷Li or ³¹P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the ³¹P chemical shift tensor is dependent on the deviations of the O–P–O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P′–P–P″ and the ones of the O′–P–O″ is related to the overall charge on the PO₄ group. We also find the positions of the isotropic lines for ⁷Li essentially depend on the site co-ordination of this nuclei.     

Electron transport in modulation-doped GaAs v-groove quantum wires

We report the growth of modulation-doped GaAs/Al_xGa_1−xAs v-groove quantum wires and structural, electrical and optical investigations of their electronic states and transport properties. By using alternative group III precursors on partially SiO₂ masked pre-patterned GaAs substrates, samples have been fabricated which permit electrical measurements of single isolated wire structures without the need for additional electron-beam lithography. Magneto-transport was measured as a function of tilt angle of the incident magnetic field to identify the formation of low-dimensional electron gases in different parts of the structure. Photoluminescence investigations reveal 1D and 2D confined states which show different carrier heating when electric fields are applied along the wire structure.