线轴状刚体平面平行运动实验简析

用细丝线拉动线轴状刚体在水平平面桌面上(或水平导轨上)的运动,是典型的平面平行运动.改变细丝线拉力的倾角或方式,线轴状刚体可以有多种不同的运动状态,因此这是一个有趣的演示实验.之所以线轴状刚体有多种运动状态,关键因素是线轴状刚体在作纯滚动时它与平面桌面或导轨之间的相互作用力是静摩擦力,静摩擦力可以在一定范围连续变化以使线轴状刚体的运动能够满足动力学方程和运动学方程.当所需要的静摩擦力超出其最大允许值时,线轴状刚体与平面桌面或导轨之间将出现滑动,二者之间的摩擦力将由静摩擦力变为滑动摩擦力,纯滚动状态将消失.     

慢速高电荷态离子与氦原子碰撞中双俘获稳定比的势能参量(英文)

在慢速高电荷态离子与氦原子碰撞的双电子转移过程中,借用虚态图像来描绘转移电子间的强关联特性;根据分子库仑过垒模型纳入反应Q值,定义势能参量ω来区分碰撞系统并度量双电子转移过程。对照之前的实验数据,清晰地显示当ω1和ω2时,纯双电子俘获或自电离双俘获分别占优。澄清了碰撞系统的本质区别在于散射离子上两个转移电子的平均激发能和平均束缚能的相对比率。     

锥体上滚实验的原因分析

从锥体上滚实验的几何条件出发,分析该实验中双圆锥体沿倾斜导轨向上滚动的根本原因,并讨论了几何参数对实验的影响.     

气垫导轨实验中容易忽略的调整

在气垫导轨实验中,第一步即是通过调节底脚螺丝校正气垫导轨的水平。通常检验导轨水平的方法是在导轨通气以后,将滑块放在导轨不同位置,看能否保持稳定不动;或者观察滑块起动后通过两个不同位置光电门的时间是否相等,从而判断导轨是否水平。需要指出的是,这种调整方法往往只注意了横向(导轨轴向)的水平调整,而忽略了纵向(垂直导轨)的水平调整。因为横向水平较为直观,采用上述方法检验很灵敏、方便。而纵向水平的调整,采用上述方法并不灵敏,用眼睛观察也不易察觉,所以往往易被实验者忽略。事实上纵向不水平和横向     

大小钢球对心碰撞实验

用两个一维单摆进行大小钢球对心完全弹性碰撞的实验,表明碰撞前后两钢球的运动状态是分立的,仅为4个点,碰撞过程是在这4个点间依次跃变的循环过程.     

利用全信息声发射仪实现恢复系数与重力加速度的快速测量

本文利用DS2型全信息声发射信号分析仪构建了可以快速测量并计算出小球与平板之间弹性碰撞恢复系数及重力加速度的实验测量系统。通过实时记录小钢球与瓷砖地面之间,玻璃球和弹力球与钢板之间3种不同碰撞模式下的碰撞全波列,本文分析获取了相邻两次碰撞之间的时间间隔序列T_n,并建立了lnT_n与碰撞次数n之间的线性关系,从而实现对弹性碰撞恢复系数及重力加速度的快速测量与分析。实验测量表明,弹性碰撞恢复系数与重力加速度快速实验测量系统具有实验原理简单、清晰,记录的碰撞波形清晰、完整,实验测量精度高和稳定性好的特点。     

多体碰撞实验的设计与讨论

设计了一套简单的多体碰撞实验装置,应用统计原理研究了1个小钢球与N个束缚钢球的碰撞过程,分析了其中一些有趣的现象.     

一种新的自调整多叉树防碰撞算法

针对标签碰撞问题进行了研究,提出了一种新的自调整多叉树防碰撞算法。新算法采用曼彻斯特编码准确判断碰撞位置,根据碰撞位类型的不同自动调整树的叉数;引入异或运算优化查询请求,避免了标签识别过程中不必要空闲时隙的产生;利用二进制数替代标签EPC码,很大程度上减少了通信量。通过理论分析,准确计算出新算法的性能参数。利用Matlab平台对新算法和其他四种常见算法进行了对比仿真实验,新算法在总时隙、吞吐率以及通信复杂度等方面都表现出良好的性能。     

液滴撞击超疏水碳纳米管阵列表面的行为研究

实验研究了不同韦伯数(We)时液滴碰撞碳纳米管阵列表面的动态过程行为,并借助改进的水平集方法对液滴碰撞过程进行了数值模拟。模拟过程中,分别引入了接触角动态变化的Kistler模型和Blake模型,并就液滴铺展因子和顶点高度等方面将模拟与实验结果进行了对比分析。结果表明:在We=1.4～110范围内液滴碰撞都经历了相似的铺展-收缩-弹跳过程,不同We时模拟和实验结果都比较接近;在液滴铺展阶段,依据Kistler模型的模拟结果与实验值更接近,而在收缩阶段,依据Blake模型的模拟结果与实验值更加吻合.综合考虑后发现Blake模型与实验值的偏差较Kistler模型在整体上更小,细节吻合较好,验证了模型的可靠性。     

滚球混沌运动演示实验

以滚球在3个凹形槽上的受力体现作用的非线性,导轨由电机推动作简谐振动,滚球在导轨上作受迫(滚动)振动,可以把导轨作简谐振动的频率或振幅作为调整参量.当受迫振动的滚球振幅小时,滚球只在1个凹形槽中作简谐振动;当振幅渐渐增大时,可呈现周期倍增和渐至混沌状态.通过观察安装在同一振动滑板上的2套导轨上的滚球的运动,则可以演示混沌运动对初值的敏感性.     

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.     

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.     

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.     

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.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

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.