共查询到20条相似文献,搜索用时 62 毫秒
1.
1 提出问题。在中学物理教学中,机械波的速度决定于介质的性质.人民教育出版社物理室编著《物理》教材,是这样论述的:“机械波在介质中传播的速率是由介质本身的性质决定的,在不同介质中传播的速率并不相同.”对这个问题没有展开讨论,教师对这个问题也是一句带过,学生不易理解.究竟决定于介质的什么性质?或者说,机械波的速度跟哪些因素有关呢?在这个问题上我们以绳子为例进行了较为成功的探索,提高了学生的探索科学知识的兴趣和能力. 相似文献
2.
振动弦的“色散”实验研究 总被引:1,自引:1,他引:0
研究了有界弦横向强迫振动时弦上波速的色散现象.实验测量结果表明:由弦的张力和线密度决定的弦上的波速(T/ρ)~1/2不一定是常量,在一定的条件下,弦的波速会随着弦驻波的波长长度(弦长)改变而变化. 相似文献
3.
5.
7.
推导在一般情况下(不限于小扰动)作用于绳上某一质元两端张力所作功的表达式,导出了绳上某一质元能量与张力所做的功之间的关系,直观地得出行波能量传递是通过张力作功实现的,驻波的能量在波节、波腹之间转移也是张力作功的结果。 相似文献
8.
10.
11.
12.
In this paper, an active control scheme for an axially moving string system that suppresses both longitudinal and transverse vibrations and regulates the transport velocity of the string to track a desired moving velocity profile is investigated. The control scheme utilizes three inputs: one control force at the right boundary, which is exerted by a hydraulic actuator equipped with a damper, and two control torques applied at the left and right rollers. The equations of motion are derived by using Hamilton's principle. Two nonlinear partial differential equations govern the longitudinal and transverse motions, where the variation of the tension of the string due to the transverse and longitudinal vibrations is considered. Among four boundary conditions, two describe the rotational dynamics of the left and right rollers; one determines the dynamics of the hydraulic actuator at the right boundary, and the last one denotes that the left boundary is fixed. The Lyapunov method is employed to generate control laws. Asymptotic stability of the transverse and longitudinal dynamics and the velocity tracking error is achieved. The effectiveness of the proposed control scheme is illustrated via numerical simulations. 相似文献
13.
Mingyi Sun 《International Journal of Infrared and Millimeter Waves》1997,18(9):1725-1729
In this paper three-dimentional simulations are carried out to the phase velocity of a transverse electric wave which propagates
in a relativistic electron beam magnetized by a wiggler field and an axial guide magnetic field. Results show that the phase
velocities are quite different from each other as the axial guide magnetic field changes its direction. 相似文献
14.
A. I. Matveev 《Technical Physics》2012,57(12):1646-1655
The formation of a transverse wave with a phase velocity lower than the velocity of light, which can exist in an equilibrium plasma without a slow-wave structure in zero magnetic field, is described. It involves the transformation of a transverse wave with trapped electrons, traveling along the magnetic field, into a slow transverse wave after the removal of the magnetic field. During the evolution of the wave with trapped electrons, the magnetic induction decreases very slowly in the direction of the wave propagation. As a result, the velocity at which electrons are in resonant interaction with the wave increases; therefore, the electrons fall to the bottom of potential wells. Under the influence of the trapped electrons, the phase velocity of the wave decreases and becomes lower than the velocity of light. It becomes equal to the velocity at which the electrons are in resonance interaction with the wave at the instant when the magnetic field vanishes. It is demonstrated that a transverse wave with a velocity lower than the velocity of light can exist in an equilibrium plasma even after the magnetic field vanishes; in this case, the flow of trapped electrons serves as a slow-wave structure. 相似文献
15.
G. Fernandez 《Journal of sound and vibration》1984,96(1):37-43
For a submerged cable, the classical equation of a vibrating string must be modified to account for added mass and damping effects. This can be done with the aid of Morison's formulae. The resulting equation is non-linear. It is solved for the case when one end of the string is forced into sinusoidal transverse motion. The first harmonic approximations for both resonant and non-resonant responses are obtained by the method of matched asymptotic expansions under the assumption that the non-dimensional damping coefficient is small. 相似文献
16.
The dependence of distribution functions of quarks, antiquarks, diquarks and their fragmentation into hadrons on the transverse momentumk t is discussed in the frame of the quark-gluon string model. We then discuss the division ofk t between 2n-quark-antiquark chains, orn-pomeron showers. Hadron and hadron-nuclear processesp?p,p?A,K +?p,K +?A are analysed. A strong dependence of the observed values on the numbern is derived by this method, which is of special importance for the analysis of hadron-nucleus collisions. Our method is compared with the regulark t division method. 相似文献
17.
18.
19.
谈"圆驻波"演示实验中的思维误区 总被引:1,自引:0,他引:1
指出了对“圆驻波”演示实验在认识上的两个误区,并在理论上分析了在该装置中实现圆环驻波的条件,得到了和实验现象相一致的理论结果。 相似文献
20.
水声材料横波声速和衰减系数参量源法测量系统 总被引:1,自引:0,他引:1
提出了测量10-100 kHz频段水声材料平均横波声速和衰减系数的测量系统,系统具有低频、小尺寸、窄波束的特点。测量装置应用截断参量源作为声源,结合了精密的坐标系统。在对平板声压透射系数的平面波模型进行理论修正和实验研究的基础上,测量平板样品的透射系数(插入损失)的频谱和角谱,并采用曲线拟合方法来估计样品在测量频段的平均横波声速和衰减系数。在2 m×1 m×1.5 m消声水槽中,对一些典型样品(尺寸500 mm×600 mm)进行了测量实验,结果表明,水声材料样品在声波不同入射角时的声学性能有较大差异,不能用声波垂直入射时的声学性能数据代替;横波声速和衰减系数是评定水声材料声学性能的重要参数,尤其在声波斜入射情况下;在研究材料构件或复杂器件的声学性能时它们也是必不可少和不能不考虑的。实验还验证了测量方法和系统的可行性,也表明仅在这一频段的测量还远不能满足水声工程的实际需求,有必要将测量方法应用扩展到更低或更高的频段。 相似文献