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1.
利用速调管放大器产生高功率微波拍波实验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
在高功率微波(HPM)拍波效应实验中,采用了一种利用单只速调管放大器获取HPM拍波的方法.实验结果为:输出HPM拍波主频率位于S波段,拍频范围10—120MHz可调,拍波脉冲峰值功率可达1MW,脉冲重复频率最高可达500Hz,实验获取的拍波已成功应用到各类电子系统的HPM拍波易损性效应实验中. 关键词: 拍波 高功率微波(HPM)  相似文献   

2.
将虚拟技术与多媒体计算机教学技术相结合,演示正弦波的拍现象。方法是用麦克风采集拍音信号输入到计算机中,利用频谱分析软件进行实时分析,同时将拍信号投影在大屏幕上,以使学生全面、直观地认识而掌握拍的概念。  相似文献   

3.
双波长拍波干涉测长中拍波干涉条纹尾数的测量方法   总被引:2,自引:0,他引:2  
邓罗根  梁晋文 《光学学报》1993,13(3):62-267
描述在拍波干涉测长中使用的几种拍波干涉条纹尾数测量方法,提出一种拍波锁相型对准原理,介绍和比较拍波干涉仪的三个原理方案,讨论测量方法和测量精度等问题.  相似文献   

4.
王力  田方宝 《气体物理》2020,5(4):21-30
自然界中的昆虫和鸟类大都采用拍翼飞行的策略,其优越的气动表现使拍动飞行方式备受关注.值得注意的是,拍动飞行昆虫和鸟类在实现高机动性的同时,产生的噪音并不十分显著.因此,对拍翼飞行的流固声耦合问题进行研究,揭示其飞行动力学和声学特性,对于应用这类飞行技术具有重要的指导意义.文章采用一种浸入边界法对拍翼悬停时的流固声耦合问题进行数值模拟研究.具体针对刚性拍翼和不同刚度、质量比的柔性拍翼进行了数值模拟,分析了拍翼刚度和质量比对拍翼悬停时的升力和声学特性的影响.结果表明拍翼的转动能有效增加升力,提高效率并降低拍翼运动产生的声音;同时悬停拍翼的近场声受涡的影响明显,尤其是在较大的转动角度时;引入适当的弹性可有效提高拍翼在悬停时的气动表现,包括提高升力系数和效率;综合考虑气动和声学表现,可以看出当无量纲拍动频率在0.3~0.4时,低质量的拍翼(拍翼-流体质量比为1.0)产生的声音较小,同时又具备较高的效率.   相似文献   

5.
介绍了拍与调幅波的原理,提出了利用数字示波器观测拍与调幅波的方法.通过实验观测,加深了对拍和调幅波原理的理解.  相似文献   

6.
拍图形特征的相位分析   总被引:2,自引:0,他引:2  
王宁星 《大学物理》2000,19(5):8-12
用相位分析的方法,对拍的图形进行讨论,得出拍图形的特征及规律。  相似文献   

7.
本文简述了双光栅形成光拍信号的过程与微弱振动测试的基本原理,通过仿真计算与实验测试相互对比,对光拍信号的表达式进行了修正,振幅修正系数是由于光栅振动带动衍射光斑振动而产生的;同时,本文通过仿真计算解释了光拍信号毛刺的产生原理,光拍信号的毛刺是由于高级衍射带来的,要想降低毛刺对光拍信号的影响,应尽量使光栅条纹平行或者降低光路中激光强度,以此降低高级衍射对光拍信号的影响.  相似文献   

8.
姜洪喜  杜广环 《物理实验》2007,27(11):41-42
将传统的"拍"现象演示装置与现代的计算机多媒体教学技术结合,用麦克风采集拍音信号,并通过音箱放大,同时将采集到的信号输入到计算机中,利用频谱分析软件进行实时分析,并将拍信号投影在大屏幕上,使学生全面、直观地认识、掌握拍的概念.  相似文献   

9.
黄艳芳  刘勇君 《应用声学》2023,42(2):312-323
根据非对称圆环点冲击下拍的理论模型分析拍的分布特性,该文提出了一种调整圆环拍周期和清晰度的方法。阐明圆环结构拍的发生原理,从而控制清晰度;在圆环上添加质量或研磨可以改变非对称性进而调整拍频。引入等效圆环的概念,通过在轴对称圆环上添加一个质量,建立与非轴对称圆环振动特性相同的等效圆环模型。利用该模型,计算要在非轴对称圆环添加质量的大小和位置,以便获得拍的最佳周期及清晰度。用实验和有限元法验证了该方法的有效性。  相似文献   

10.
黎开管中燃烧振荡现象的实验研究发现,在不稳定发生的极限工况附近可能存在幅值周期性变化的振荡现象,也即拍振,其拍频可低于l Hz。本文比较了铁丝网和穿孔陶瓷两种稳焰体对拍振发生的影响;通过时频分析揭示了拍振的声压脉动的主频随时间周期性变化的特征。采用基于数字信号处理器的控制系统,研究了对极限环和拍振的主动控制效果,实验结果表明,黎开管系统中导致拍振的非线性可能使得采用常规主动控制方法难以取得满意的控制效果。  相似文献   

11.
The beat spectrum between modes of a gas laser having a resonator with a plane-and-sphere mirror system was studied. Intense beats were detected in the 0–1.5 Mc range. It is shown that the presence of low-frequency beats can be associated with the nonideality of the resonator. The intensity of the beats was found to depend on their spectral composition and on the degree of beam limiting. This effect is related to the presence of antiphase oscillation zones in the laser beam for azimuthal modes and to the variation of the interference pattern with time when the beam is limited in the focus of the objective.  相似文献   

12.
We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system. More importantly, the fifth-order phase-sensitive heterodyne detection of ultrafast polarization beats has been exploited. The fifth-order nonlinear optical response can be controlled and modified through the colour-locked correlation of twin noisy fields. Thus, this method with the phase dispersion information is a good way to measure the real and imaginary parts of the fifth-order nonlinear susceptibility.  相似文献   

13.
For Λ-type three-level atomic systems we have clarified using diagram that (1) it is impossible to observe quantum beats due to the ground state sublevels by measuring the time dependence of the fluorescence intensity, and (2) why it is physically possible to observe and how we can observe quantum beats in the ground state sublevels by using fluorescence. Generalization of the results shows that we can determine from which state (the ground state or the excited state) the quantum beats are originated. Analytical result is shown for four-level atomic systems.  相似文献   

14.
Interaction between forward bulk magnetostatic waves propagating in a structure consisting of two planar films separated by a nonmagnetic spacer is studied. When two modes are excited in the structure, a phase mismatch between them produces symmetric, asymmetric, and “forked” beats of the amplitudes of the magnetically coupled modes. It is shown that the parameters of the beats can be controlled by varying the magnetic field intensity and ration between the initial amplitudes of the modes excited in the structure.  相似文献   

15.
A discussion is given of the time-behavior of recoil-free γ-radiation passing through a resonant medium. The classical dispersion theory of Hamermesh is extended to account for different linewidths in source or absorber so that a synchrotron-radiation source can be simulated. A result, essentially the same as that of Kagan et al., follows in the limit of large source width. A review is given of the quantum beats which result from the absorption of one line of a frequency-modulation spectrum. An example is given of the measurement of second-order Doppler shift in Fe−Be by the method of quantum beats. Finally, there is a discussion of the measurement by quantum beats of the very small energy shift in a57Co−Cu source by a magnetic field.  相似文献   

16.
本文通过用双踪示波器来观察李萨如图形和“拍”现象 ,加深学生对两种特殊形式的简谐振动合成的理解  相似文献   

17.
We report experimental studies of absorption quantum beats induced by electron spin coherence in GaAs quantum wells. Absorption quantum beats occur for strongly localized excitons, but nearly vanish for mobile excitons in the third order nonlinear optical response. Pronounced quantum beats for mobile excitons emerge in an unusual fifth order process. These results, along with a qualitative analysis based on the use of N-exciton eigenstates, elucidate how the manifestation of electron spin coherence in the excitonic nonlinear optical response can differ fundamentally from that in an atomic system.  相似文献   

18.
It is shown that excitonic transients of bulk GaN can be accurately measured by an interferometric correlation technique used in reflection geometry. This is demonstrated for resonantly excited excitons in high quality GaN epilayers. The interferograms exhibit a clear modulation of the signal due the quantum beats between A and B excitons. The period of these beats is in good agreement with the A–B exciton energy splitting measured by means of frequency-resolved reflectivity. The decrease of the overall signal is mainly connected to the crystal quality and strongly dependent on the inhomogeneous broadening which can be extracted from the correlation spectra. These results are in agreement with numerical calculations based on the Fourier transform determination of the time-resolved reflection coefficient in the framework of linear semi-classical theory carried out in order to obtain the autocorrelation response.  相似文献   

19.
It is shown that coherence between nondegenerate sublevels of an atomic ground state is efficiently induced by means of a short resonant light pulse. The free precession of the coherence causes beats in forward stattering of a probe beam, which can sensitively be detected by a polarization technique. Zeeman beats on the 4f6 6s27 F1-4f6 6s6p 7F0 transition of samarium were observed. In sodium vapor transient ground state coherence was detected in a single-shot measurement.  相似文献   

20.
基于V型三级级原子由于真空与原子耦合引起的量子相干效应,研究了泵浦-探测技术中透射受激量子拍特征.理论计算表明:这种受激量子拍与荧光量子拍相比具有高的信噪比.理论结果与实验有较好的一致性.  相似文献   

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