"光子"与"光子学"

19世纪末普朗克在推导黑体辐射公式的过程中,假定物体在发射和吸收辐射时能量是不连续的,是呈现与辐射频率v成正比例的最小能量单位ε=hv的整数倍变化的,这个能量元ε称为能量子．普朗克所提出的“能量子”假说,冲破了经典物理学中的一切自然过程都是连续的这一原理,标志着人类对客观世界物     

物理"海马"、数学"海马"与生物"海马"

在C60-TCNQ(一种有机分子名称的缩写)和纯的TCNQ有机分子薄膜中,文章作者得到了一种形似海洋中生存的动物海马的图案结构,取名为"海马"分形结构.这种"海马"图案在旋转180度时具有近似的对称性,但是不同于简单的二维反转对称.在数学中用复变函数的多项式,通过Julia对复杂空间中函数的纯粹数学映射(即z→z2 c,其中c=-0.74543 0.1130i),也能模拟出相似的"海马"图案.对于"海马"分形,文章作者提出如下的一种形成机制,即:在薄膜形成初期过程中,中性分子或团簇中存在部分荷电粒子,由于库仑排斥作用,成核和生长过程中会形成对称性破缺,最终形成"海马"状分形."海马"的有趣图案,加深了人们对自然与科学统一的认识,激发了人们对自然本源的探索激情.     

谈"速度"与"速率"

一 高教出版社出版的中专《物理》教材(王银明主编1999年版)第40页中有这样一道题: 2-3-1关于匀速运动的特点,下列说法中正确的是: A.运动轨迹是直线 B.运动方向不变 C.运动速率不变 D.运动速度是常量     

浅说"混沌"

以单摆的强迫阻尼运动、罗伦兹系统及Ｌｏｇｉｓｔｉｃ映射为例,解说了混沌运动地主要特征,并介绍了混沌理论建立与与发展过程中的一些史话。     

试论"普朗克原理"

 德国著名的物理学家、一代宗师马克斯·普朗克(M.Plank,1858～1947),不仅因其发现能量子对物理学的发展所做出的卓越贡献而荣膺1918年的诺贝尔物理学奖,而且因他的一段特殊的人生经历而得出的一个深刻教训,亦即普朗克自称的"一个值得注意的事实",而被尊称为"现代物理学发展的精神之父"。现拟就这个在物理学界鲜为人知的"新事实",作如下简要的论述。     

"引力"七问

1 引力是什么 牛顿在17世纪就认识到宇宙中任何地方的一切物体的引力作用方式是相同的,且两物体间的吸引力与它们的质量的乘积成比例,与它们距离的平方成反比,即著名的"引力的平方反比律."爱因斯坦在20世纪初发表的广义相对论是研究物质在空间和时间中如何进行引力相互作用的理论,它将平方反比律解释成时空因物质和能量的存在而发生畸变的结果,并把牛顿理论包含在内.     

也议"三原色"

牛顿早在1672年就发现了光的色散现象,直到1801年英国医生托马斯·杨才提出了三原色理论,后来赫尔曼·冯·亥姆霍兹将它完善了.三原色是哪三原色?一次我问高职二年级学生.有人说三原色是红、黄、蓝;也有人说是红、绿、蓝;为什么会出现两种不同的"三原色"呢?究竟哪一个才是对的?     

"验证机械能守恒定律"实验中的"八项注意"

验证机械能守恒定律这个实验,是高中物理实验中十分重要的实验,因为它是“打点计时器的使用“、“长度的测量“、“运动学规律“、“能量的不同形式及其转化“等的综合应用,对培养学生动手能力,分析判断能力,综合能力都十分有益,并且在近几年来的高考中也时常出现本实验中的题目.为能够顺利完成并熟练掌握本实验,笔者总结出“八项注意“,望能引起注意.……     

"向心力"教学设计

1教学设计思路旧教材是从日常现象观察、猜测向心力会与什么因素有关,然后利用向心力演示仪得出向心力的表达式,再根据牛二定律推导出向心加速度表达式．向心加速度表达式没有进行理论推导．总体思路是由向心力这个本质到向心加速度这个现象．     

"解剖"激光告警

介绍了激光告警的作用,分析了激光告警器的原理、性能要求和分类,然后分别阐述了典型的光谱识别型、相干识别型和散射探测型激光告警器,并对不同类型的激光告警器进行了比较评价.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.