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本文通过对冲击检流计原理构造和测量实例的简要阐述,分析了换向开关在用冲击检流计进行精密测量过程中对测量结果误差的影响,说明了对目前实验中所使用的换向开关进行改进的必要性,并介绍了一种我们最近设计的新型换向开关,以及用它消除误差的原理。用冲击法测量磁性材料的特性或磁状态,是高校物理系学生应当掌握的实验方法之一。而在这一类实验中必不可少的仪器设备便是冲击检流计和换向开关。目前普遍使用的换向开关都是双刀双掷开关,就是先得将电路断开,然后再接通,即必须经过一个 相似文献
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电爆丝断路开关是在电感储能系统中广泛应用的断路开关,其具有结构简单、成本低、截断能力强的特点。介绍了电爆丝工作的基本原理,其本质为一个快速增长的电阻,利用高阻抗来实现断流。通过PSpice软件建立了电流通过电爆丝断路开关工作时,其电阻变化的模型,从而可以仿真电爆丝断路开关的工作过程。设计了一组电爆丝断路开关的实验,PSpice模型仿真结果同实验结果进行了比较。结果发现,该模型起爆时刻,产生电压幅值等方面和实验结果比较接近,说明该模型比较科学合理,对以后的电爆丝断路开关的设计具有较大的参考价值。分析了产生误差的原因及该种仿真方法的局限性。 相似文献
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采用聚酯薄膜为绝缘材料,设计了一种小型化便携式层绕Blumlein线,其主要特点是采用S型层绕的方法对薄膜介质平板Blumlein线进行绕制,使形成线的体积小,结构紧凑,有利于脉冲功率源小型化、实用化的发展。其集成了薄膜电容器易卷绕、耐高压、储能强的优势,同时具备了传输线的特点。采用气体火花间隙开关,对S型薄膜介质脉冲形成线的耐压特性及负载输出波形进行了实验研究。结果表明:开关的导通特性对脉冲形成线的负载输出波形有很大的影响,开关电感及开关抖动等因素会影响脉冲波形的前后沿,使输出脉冲方波波形质量变差。采用PSpice软件对实验等效电路进行了模拟,得到了与实验一致的结果。设计的Blumlein线体积为50 cm18 cm12 cm,承载电压50 kV,负载输出脉冲上升沿50 ns,平顶宽度120 ns。 相似文献
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利用成熟的偏振控制技术,设计了一种由偏振光分束器、相位型空间光调制器和反射镜构成的2×2光开关,该光开关所用器件少,具有结构简单紧凑、控制灵活方便、功能实现与信号光的偏振态无关以及可以双向交换等特点;在此基础上通过2×2光开关的串连,设计了一种与偏振无关的双向4×4光开关的实验模块,根据其路由选择与控制方法,得到了4×4光开关实现信号光全排列无阻塞输出与交换对应的路由状态表,并对该实验模块的功能实现进行了详细的分析与讨论。 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
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. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献