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     

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.     

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...     

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。     

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。     

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.     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.