打点计时器的正确使用与调整

Ｊ０２０３型电磁式打点计时器是研究物体运动规律的一种实验仪器．它价格比气垫导轨便宜的多，结构比气垫导轨简单的多．而且省去了气垫导轨的复杂调整．也不存在气垫导轨的导轨变形、气孔阻塞、滑块磨损，光电门失效，计时器故障，气源故障等．电磁打点计时器也没有气垫...     

评介一套气垫导轨气源系统

气垫导轨实验装置可精确完成多种力学实验,而气源对实验的完成有较大影响.配备一套好的气源系统,对圆满完成气垫导轨上的实验是十分必要的.我们物理实验室对气垫导轨的气源系统几经改进,最后采用了“罗茨式”鼓风机气源     

关于改进《在气垫导轨上验证机械能转换与守恒定律》实验方法的探讨

关于改进《在气垫导轨上验证机械能转换与守恒定律》实验方法的探讨蒋于佳（成都航空工业学校６１００６１）用数字计时器配合气垫导轨进行实验时，由于气垫导轨比较有效地减小了力学实验中国摩擦而造成的误差，所以能比较准确地对力学规律进行定量的验证，较传统仪器实验...     

一个取代气垫导轨验证牛顿第一定律的演示实验

牛顿第一运动定律在教材中没有安排演示实验,而通常的演示大多是在气垫导轨上进行.我们设计该演示实验不仅可以取代气垫导轨,而且取材容易,操作简单,可见度大,还可在任意方向上演示第一定律,克服了在气垫导轨上演示的固有缺点.具体介绍如下.     

气垫导轨气源消声箱的研制

气垫导轨是实验室的基本仪器.用吹尘器作气垫导轨的气源,与用吸尘器或小型空气压缩机相比具有很多优点,如售价仅135元,耗电约400瓦,其输出空气流量为1.5—1.8m~3/min 风压为66000～80000N/m~2(500—600mmHg 柱).一台吹尘器可同时带动多达6～8台气垫导轨进行实验.吹尘     

气垫导轨在刚体转动惯量测定实验中的应用

本文介绍了一种测量刚体转动惯量的新方法。即把气垫导轨和刚体转动仪结合起来来测量刚体的转动惯量,使传统的气垫导轨实验和刚体转动惯量测定实验得以更新,提高了实验测量的精度,拓展了实验内容。     

利用Tracker软件分析气垫导轨上弹簧振子的阻尼振动

利用Tracker视频软件的自动追踪功能,有效地跟踪气垫导轨上弹簧振子的阻尼振动,实时描绘出振动的位移-时间曲线,利用软件自带的功能拟合出振动曲线方程和包络线方程,计算出该气垫导轨的阻尼常数,并由坐标转换功能得到运动的相图.     

计程气垫导轨

计程气垫导轨是自带计程装置的气垫导轨。在气垫导轨上与导轨平行地安装一支由电动机带动的滚筒,在滑块上固定一与滚筒刚好能接触的墨水笔,滑块在运动过程中墨水笔在滚筒上画出螺旋线。与前进一个螺距对应的时间等于滚筒的转动周期。螺旋线的转向可区分滑块运动的往、返。以此为基础,可同时记录滑块运动的时间和位移。导轨用有机玻璃粘制(或用角铝加工),采用小型鼓风机作气源。     

气垫弹簧振子简谐振动正弦曲线合成演绘仪

针对传统简谐振动图像演示仪存在的不足,气垫弹簧振子简谐振动正弦曲线合成演绘仪利用气垫导轨,在弹簧振子上安装一强激光器,在气垫导轨的前端安放一热转印卷纸的走纸机构,当弹簧振子在气垫导轨上作简谐振动时激光器跟随振子一起运动,强激光打在匀速向上运动的卷纸上,两运动一合成得到简谐振动正弦曲线图像。仪器结构简单,操作方便,学生能很好理解简谐振动曲线的形成过程,演示效果好。     

气垫导轨水平状态的判断和调节

本文给出气垫导轨水平状态的判断和调节的方法     

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.     

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.     

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.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.