共查询到20条相似文献,搜索用时 218 毫秒
1.
讨论圆截面弹性细杆在黏性介质中的平面振动. 基于Kirchhoff理论,以杆中心线的Frenet坐标系为参考系,建立其动力学方程,杆中心线为任意平面曲线时,其扭转振动与弯曲振动解耦. 讨论两端固定条件下任意形状杆的平面扭转振动,以及无扭转的轴向受压直杆和圆环杆的平面弯曲振动,导出其自由振动频率和阻尼系数. 证明空间域内压杆的Lyapunov稳定性和欧拉稳定性条件为时域内渐近稳定性的充分必要条件,或无阻尼压杆的稳定性必要条件. 圆环杆平衡恒满足渐近稳定性条件.
关键词:
弹性细杆
黏性介质
扭转振动
弯曲振动 相似文献
2.
本文对指数型纵-扭复合振动模式的复合超声变幅杆进行了理论及实验研究,该变幅杆由均匀截面直棒及指数型截面杆组成。文中推出了变幅杆中纵向振动及扭转振动的共振频率方程,通过发迹指数型变截面棒的截面变化规律,实现了同一变幅杆中纵向振动与扭转振动的同频共振。 相似文献
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基于Kirchhoff理论讨论圆截面弹性螺旋杆的动力学问题.以杆中心线的Frenet坐标系为参考系,建立用欧拉角描述的弹性杆动力学方程.讨论其在端部轴向力和扭矩作用下保持的无扭转螺旋线平衡状态.在静力学和动力学领域内讨论其平衡稳定性问题.还讨论了弹性杆平衡的Lyapunov稳定性和欧拉稳定性两种不同稳定性概念之间的区别和联系.在一次近似意义下证明了螺旋杆在空间域内的欧拉稳定性条件是时域内Lyapunov稳定性的必要条件.导出了解析形式螺旋杆三维弯曲振动的固有频率,为螺旋线倾角和受扰挠性线波数的函数.
关键词:
弹性螺旋杆
Kirchhoff动力学比拟
Lyapunov稳定性
欧拉稳定性 相似文献
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研究了采用扭转柱面镜光学系统将厄米-高斯光束变换成为具有轨道角动量的拉盖尔-高斯扭转对称光束. 采用本征模式分解的方法分析了扭转柱面镜光学变换系统实现光束变换的原理.利用光束传输矩阵和二阶矩理论分析计算了光束经过扭转柱面透镜变换过程中的轨道角动量传递过程,证明光束与透镜系统的轨道角动量交换发生在第一个柱面透镜处,光束经过第一个柱面透镜后,具有的轨道角动量保持不变.
关键词:
轨道角动量
光束变换
扭转对称光束
轨道角动量传递 相似文献
11.
V. V. Fisanov 《Russian Physics Journal》2006,49(8):853-856
The singularity index of the electromagnetic field on the edge of wedge structures of two types (with and without ideally
conducting sides) is investigated in the presence of a sector of a medium with negative permittivity and permeability (the
Veselago medium). Restrictions on the material and geometrical parameters at which the condition on the edge is violated are
determined.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 56–58, August, 2006. 相似文献
12.
We obtain the solution to the problem of the skin effect in a metal with specular-diffusion boundary conditions for arbitrary
values of the anomaly parameter in the form of the Neumann series. For this purpose, we develop a method based on the idea
of representation of not only the boundary condition imposed on the field (as is conventionally done), but also the boundary
condition imposed on the distribution function, in the form of a source. The specular reflectance is an arbitrary function
of the angle of incidence of electrons on the metal surface. 相似文献
13.
We propose one a variant of calculation of the energy spectrum of bound state systems with relativistic corrections. In the
framework of quantum field theory, an expression that takes into account relativistic corrections to the mass of the bound
state with a known nonrelativistic pair interaction potential is proposed on the basis of calculating the asymptotic behavior
of correlation functions of the corresponding field currents with the necessary quantum numbers. Excluding the time variables
allows one to determine nonperturbative corrections to the interaction potential. The following results have been obtained
in the framework of this approach. The nonperturbative corrections arising due to the relativistic nature of a system to the
interaction Hamiltonian are determined. The dependence of the constituent mass of bound-state forming particles on the free
state mass and on the orbital and radial quantum numbers is analytically derived. The energy level shift of muonic hydrogen
taking into account relativistic corrections is calculated. The energy spectrum of a wide class of potentials that describe
the Coulomb bound state is analytically derived with relativistic corrections. The mass spectrum of the glueballs and the
constituent masses of the gluons are analytically calculated taking into account spin-orbit, spin—spin, and tensor interactions.
Our numerical results have shown very good agreement with the lattice data. Taking into account nonperturbative and nonlocality
characters of interactions, the mass spectrum of the mesons consisting of light-light and light-heavy quarks with orbital
and radial excitations is determined. Our results show that good agreement with the experimental data for the slope and the
intercept of the Regge trajectory can be obtained only taking into account the nonperturbative and the nonlocal characters
of interactions. The dependences of the constituent masses of constituent particles on the masses of a free state are certain.
When quarks are light, then the difference between current and valent masses of quarks is greater than valent masses of quarks,
and when quarks are heavy, then the difference between these masses is insignificant. One of the alternative variants of taking
nonlocality into account has been suggested for the definition of properties of hadrons at large distances. The dependence
of the constituent masses of constituent particles on the radius of confinement is determined. 相似文献
14.
R. Plaga 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):397-403
The consequences of a violation of the Pauli principle for the physics of the solar interior are explored. It is found that a bound state of two protons becomes possible. This leads to an increase in the rate of hydrogen burning in the sun. Because a very large cross section for this reaction is in clear contradiction with the theory of stellar structure when compared with observations of solar luminosity, radius and mechanical oscillations, stringent limits on a violation of the Pauli principle in the two nucleon system can be given. However, a very small violation of the Pauli principle in the two nucléon system might solve the longstanding solar neutrino problem. 相似文献
15.
Dmitriev A. I. Vishnjak V. V. Lashkarev G. V. Karbovskyi V. L. Kovaljuk Z. D. Bahtinov A. P. 《Physics of the Solid State》2011,53(3):622-633
The morphology of the (0001) van der Waals surfaces of the layered single crystal In1.03Se0.97, which were prepared using different techniques, has been investigated by scanning probe microscopy methods. It has been
assumed that the van der Waals surface prepared with the use of an adhesive tape oxidizes in air due to the chemisorption
of acid agents on dangling bonds of the metal and selenium. An analysis of the current-voltage characteristics of the tunneling
current has shown that the composition of natural oxides represents a mixture of phases of the In2O3 oxide and wide-band-gap selenium oxides. In the InSe surface prepared by cleavage with subsequent exposure in air for approximately
2 min, the scanning with a tunneling microscope has revealed a surface ordering in the form of a corrugation of a complex
profile with a fine structure. The last fact reflects the charge density redistribution after the chemisorption of gas molecules
from air on this surface and its relaxation to the state with a minimum energy. Atoms of the basal plane are observed on the
InSe(0001) van der Waals surface prepared by cleavage in an oxygen-free medium. The surface corrugation is absent. Point defects
cause a disturbance of the periodic potential of the single crystal, which extends over a distance equal to four lattice spacings
and appears as a shadowing. A technique has been proposed for producing In2O3 oxide nanostructures on the surface of the single crystal of the layered semiconductor InSe with the use of an atomic-force
microscope probe as a nanoindenter. The ability of the probe to operate in gaseous and liquid media significantly extends
the capabilities of the method. 相似文献
16.
O. V. Klyavin N. N. Aruev L. I. Derkachenko V. Yu. Fedorov Yu. M. Chernov V. V. Shpeizman 《Physics of the Solid State》2016,58(4):711-715
The load dependence of the microhardness of polycrystalline aluminum and iron specimens produced by rolling in a nitrogen, helium, or air medium has been investigated. It has been found that nitrogen and helium have different effects on the microhardness of these metals in the low-load range. This difference is associated with the specific features in the intensity of dynamic penetration of nitrogen and helium into the surface layer of aluminum and iron, which depends on the initial defect crystal structure of the metals, as well as on the type of bonding of helium atoms and nitrogen molecules with metal atoms. It has been shown that the effect of the gaseous medium of the rolling on the microhardness manifests itself only in a very thin surface layer of metal specimens, where the microhardness exhibits a size effect, and an increase in the microhardness indentation depth remains unchanged with an increase in the load and does not depend on the gaseous medium of the prerolling of the specimens. 相似文献
17.
A comparison of the available concepts on the effect of spontaneous polarization on the height of the Schottky barrier at the metal-ferroelectric contact with the corresponding experimental data has been used as a basis for setting up an alternative model of this phenomenon, which draws on the dependence of the electron work function of a ferroelectric on the magnitude and orientation of the spontaneous polarization vector. 相似文献
18.
基于势流假设,建立气泡与壁面耦合数值模型,运用边界积分法求解,并开发三维计算程序,计算值与实验值符合很好.从气泡与壁面相互作用的基本现象入手,基于开发的程序系统地研究了刚性壁面附近气泡的动力学特性,其中包括水平壁面及倾斜壁面,研究壁面的Bjerknes效应与各特征参数之间的关系,并将各种工况的计算结果与基于Kelvin-impulse理论的Blake准则进行对比分析讨论,得出偏射流方向及壁面压力与气泡的特征参数有密切的关系,同时给出了Blake准则的适用范围.旨在为相关的近壁面气泡动态特性研究提供参考.
关键词:
气泡
壁面
边界积分
Bjerknes效应 相似文献
19.
J. Ellis G.G. Ross J. Williams 《The European Physical Journal C - Particles and Fields》1999,10(3):443-460
We suggest that the pseudo-rapidity cut dependence of diffractive deep-inelastic scattering events at HERA may provide a
sensitive test of models of diffraction. A comparison with the experimental cross section shows that the Donnachie-Landshoff
model and a simple two-gluon exchange model of the pomeron model are disfavoured. However a model with a direct coupling of
the pomeron to quarks is viable for a harder quark–pomeron form factor, as is a model based on the leading-twist operator
contribution. We also consider a direct-coupling scalar pomeron model. We comment on the implications of these results for
the determination of the partonic structure of the pomeron.
Received: 5 March 1999 / Published online: 3 August 1999 相似文献
20.
The first year data from the Wilkinson Microwave Anisotropy Probe are used to place stringent constraints on the topology of the Universe. We search for pairs of circles on the sky with similar temperature patterns along each circle. We restrict the search to back-to-back circle pairs, and to nearly back-to-back circle pairs, as this covers the majority of the topologies that one might hope to detect in a nearly flat universe. We do not find any matched circles with radius greater than 25 degrees. For a wide class of models, the nondetection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc. 相似文献