三个简谐振动合成的拍现象和实验仪

在三个简谐振动合成的拍现象进行理论分析基础上,提出了一种能够准确演示三个简谐振动拍现象的实验仪器,对进行的演示和计算机仿真比较,所给结果正确,并比传统演示手段更加直观,演示内容更加丰富.     

用示波器观察简谐振动的合成

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     

“拍”现象课堂演示实验仪

“拍”现象课堂演示实验仪高文亭任鸣放（桂林电子工业学院，桂林５４１００４）（收稿日期：１９９６－０８－１０）众所周知，振动方向相同，而频率不同的两个简谐振动合成时，如果频率相差不太大，将有“拍”现象发生，即合振动的振幅出现周期性的时而加强、时而减弱现...     

用C语言模拟拍的产生

用C语言对同方向的两简谐振动的合成问题进行了模拟 ,由此对拍的产生条件进行定量讨论。     

振动综合演示仪的设计与制作

我们设计制作了一种振动综合演示仪 ,不仅可以用它演示简谐振动、拍现象 ,还可以用来演示李萨如图形 ,并介绍了此仪器的结构和原理。     

基于Vpython的简谐振动合成可视化研究

二维三维简谐振动的合成是个复杂且抽象的物理问题,使用Python的3D模块Vpython对简谐振动合成进行了可视化模拟,形象直观地展示了简谐振动合成所形成的李萨如图形,并简单讨论了李萨如图形与频率相位的关系.     

用激光扫描法合成简谐运动图像

针对传统简谐振动图像演示仪存在的不足,设计了激光扫描法简谐振动图像演示仪。该演示仪用半导体激光器为光源,通过激光将竖直方向的简谐振动和水平方向的往复运动进行合成得到简谐振动图像,通过观察屏可观察到光点振动展开后形成的正弦(或余弦)简谐振动曲线的全过程.     

UEW-99智能型简谐振动合成实验仪在实验中的应用

UEW-99智能型简谐振动合成实验仪能同时发生出两个频率、幅值和相位可调的简谐振动．在国内高校实验仪器中率先实现了千赫兹级简谐振动的相位调整。该实验仪填补了大学物理实验中有关简谐振动合成的空白，成功地解决了简谐振动实验中的定量和定性研究。     

高等教育自学考试物理专业试用力学课程考试大纲(草案)

(接上期) (七)固体的弹性 应力和应变. 拉伸和压缩形变、胡克定律、杨氏模量、形变势能、 切变、切变模量. *弯曲和扭转.说明: (1)正确理解应力和应变概念. (2)掌握伸缩形变和切变这两种基本形变及其规律——胡克定律.对杨氏模量、切变模量、泊松比等弹性模量有一般了解. (3)结合伸缩形变熟悉形变势能. (4)弯曲和扭转形变不作为基本要求. (八)振动 简谐振动系统的动力学特征.运动微分方程. 简谐振动的运动学方程.振幅、周期和频率、位相和初位相.简谐振动的振幅矢量图。 简谐振动的能量. 简谐振动的合成、拍、互相垂直的两个振动的合成. *振…     

多个简谐振动合成问题进一步研究

本文通过讨论大学物理课程教学中简谐振动合成问题的传统方法的基础上,重点讨论了利用旋转矢量法来合成多个简谐振动问题。通过研究,N个简谐振动合成的合振动振幅取最小值时,其闭合多边形的形状个数是N-1,N取偶数时,存在两矢量相位相反合成矢量后为零,不存在闭合多边形的情况;若N取奇数时,多个矢量合成后不存在为零的情况。对多个矢量合成问题的讨论,能够进一步了解振动合成的理论和规律,理清对简谐振动合成问题的教学思路。     

Field-free alignment of molecules observed with high-order harmonic generation

High-order harmonic generation is demonstrated to provide a sensitive way for an extensive study of dynamic processes in the field-free alignment of strong-field-induced molecular rotational wave packets. The time-dependent harmonic signal observed from field-free-aligned N2, O2, and CO2 has been found to include two sets of beat frequency for pairs of coherently populated rotational states. One of them is the well-known frequency component characterizing the field-free alignment of molecules, and the other is ascribed to the beat that arises from coherence embedded in the wave packet. We discuss the effect of each frequency component on the revival signal observed with the harmonic generation.     

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.     

Frequency stability and reproducibility of iodine stabilised He-Ne laser at 633 nm

The frequency of a 633 nm He-Ne laser is stabilised on a hyperfine-structure-component of natural iodine vapour. The third harmonic component of an applied modulation frequency is detected and a servosystem is used to lock the laser frequency to the zero-crossing of the third harmonic component. The stability and the reproducibility of the laser are determined by beat frequency experiment.     

The study of third harmonic demodulation in phase modulation optical heterodyne technique using optical resonator

With the technique of phase modulation optical heterodyne(PMOH), we detected the beat-frequency signal of the reflected wave from a F-P cavity. The frequency of the beat signal was three times of that of the modulation electric field, when the 3rd harmonic of the modulation electric field was used as the phase reference signal. The line shapes of the signal match those of the theoretical calculations, and the dispersion signal has good frequency-discrimination characteristic.     

大钟拍声的调整实验

阐明大钟拍声的发生原理,并用大钟振动拍的理论模型说明拍的特性,从而控制清晰度。在实验钟上附着质量,根据附着质量位置的不同,能够改变其非对称程度,进一步调整拍频,同时用有限元分析的结果和等效圆环理论计算的结果对比。引入等效圆环理论,通过建立一个理论上带有附加质量的轴对称圆环模型,达到具有和大钟相同的振动特性。根据模型,得到在大钟特定位置附加的质量,以同时调整所需拍的清晰度和周期。在大钟多个位置进行实验,并进行有限元分析,验证了该理论的有效性。     

Developments in laser Doppler accelerometry (LDAc) and comparison with laser Doppler velocimetry

This paper outlines the principles and early development of an interferometric technique for remote measurement of vibration acceleration — laser Doppler accelerometry (LDAc). One of the key advantages of LDAc over laser Doppler velocimetry (LDV) is its ability to measure extremely high vibration accelerations and shocks, effectively without limit, and this point is expanded upon in the paper. Early LDAc development showed how unwanted, velocity-dependent optical beats could occur on the photodetector but novel use of a frequency shifting device, whose primary purpose was for direction discrimination, was successful in isolating the required acceleration-dependent beat. A problem remained in the rate at which the velocity-dependent and acceleration-dependent beats broadened during target motion. In a further development, it was possible to 'select’ a back reflection to produce a velocity-dependent beat that was NOT modulated in the presence of target motion. The acceleration-dependent beat could then be demodulated and preliminary results are given to demonstrate this outcome.     

Jet offset, harmonic content, and warble in the flute

The effects of jet offset in the flute, directing the jet above or below the edge, were explored by two distinct means-experiments with a Boehm flute sounded by an artificial blower, and time domain simulation. Very large changes in harmonic content and dynamics were observed, changing greatly with blowing pressure. Warble, a modulation of the tone at frequencies of the order of 20 Hz, was observed both in the experiment and in the simulation. The phenomenon is explained as a beat between the frequency of a second harmonic generated by nonlinearity in the jet current and a neighboring partial sustained by jet feedback near the second mode resonance. A second type of warble, in which amplitude modulation occurs in all partials but with different phases, is yet to be explained.