Purpose - The purpose of this paper is to study the dynamic vibrations of the tethered satellite system (TSS).Design/methodology/approach - The energy principle and the variational approach are used to establish the dynamic equations of the TSS. By introducing new generalized coordinates, the equations are transformed into the Hamiltonian system. Then, the symplectic Runge-Kutta (SRK) method is used to solve the canonical equations.Findings - The influence of the tether length on the dynamic behavior of the TSS is very important.Originality/value - The dynamic responses of the TSS are obtained by using the SRK method.

The orbital dynamic behaviors of 3 typical space solar power stations (SSPSs) under the gravity gradient stabilized flight strategy were investigated.In view of the earth shadow and the effective cross-sectional area,a solar radiation pressure model was established.Firstly,the energy method was used,through the Legendre transformation and with the generalized momenta introduced,the canonical equations for the orbits in the Hamiltonian system were derived;then,the symplectic Runge-Kutta method was adopted to solve the corresponding canonical equations.Finally,several numerical examples were given,and the effectiveness of the proposed model and the stability of the numerical scheme were verified,in comparison with the previously reported results.The effects of the earth shadow and the effective cross-sectional area variations on SSPSs are significant.Meanwhile,the curves of the semi-major axis,eccentricity and orbital inclination in the geosynchronous orbit were obtained.The results provide a theoretical reference for the design of SSPSs.

基于连续介质力学理论和辛弹性理论,将载流碳纳米管等效为铁木辛柯梁,采用哈密顿变分原理建立了载流碳纳米管的振动控制方程;引入对偶变量将振动控制方程从拉格朗日体系导入到哈密顿体系下;通过波传播方法分析了载流碳纳米管的能带结构;研究了流体密度、流速对载流碳纳米管能带结构的影响;同时计算了载流碳纳米管的散射矩阵.研究发现:管内流速以及流体密度对剪切频率和弯曲频率有着非常重要的影响.研究结果表明:载流碳纳米管的剪切频率和弯曲频率因流体的加入而减小,并随流速及流体密度的增大而减小;通过对数值结果的分析发现:载流碳纳米管由于管内流体、流速以及流体密度的作用,会使得载流碳纳米管变的更"软".其中,哈密顿体系下所得出的载流碳纳米管弯曲频率随管内流体密度的增加而变小,有别于在拉格朗日体系下非局部梁理论所得的结论.同时,数值结果表明散射矩阵是酉矩阵,辛体系下的入射波功率流与反射波功率流相等,即功率流守恒,体现了辛弹性力学理论的优越性.

A new type of hexagonal honeycomb sandwich tube with plateau borders are introduced in this work and the Symplectic analysis with its high computational efficiency and high accuracy is applied to obtain the structural dynamic properties. The effects of material distribution (β) and relative density (ρ¯) on the dynamic properties of the structure are also studied. Based on the definition of the elastic constants and the homogenization method, the independent elastic constants are obtained. By introducing dual variables and applying the variational principle, the canonical equations of Hamiltonian system are constructed. The precise integration method and extended Wittrick–Williams algorithm are adopted to solve the canonical equations. The dispersion relations of sandwich tubes are obtained, and the effects of material distribution and relative density on the normalized frequencies of the sandwich tubes are investigated. The proposed homogenization method is verified by comparing with other researchers׳ works. Dispersion relations of the sandwich tubes are obtained. The material distribution parameter and the relative density have significant effects on the dynamic properties of the structures. This work expects to offer new opportunities for the optimal design of metallic honeycomb sandwich tubes and future applications in the engineering sector.

This paper studies terahertz wave propagation in a fluid-conveying single-walled carbon nanotube (SWCNT) under temperature and magnetic fields. The SWCNT is modelled as a Timoshenko beam based on the theory of nonlocal elasticity, where the nanoscale effects are only included in bending moment and shear force through a nonlocal parameter. The governing equations of motion are derived based on nonlocal Timoshenko beam theory. A wave analysis is carried out to get the equations of the dispersion characteristics of wave propagation. Numerical results confirm the validity of the present model by comparing the results in reduced cases with those reported in the published literature. The dispersion curves of wave propagation show that the initial stress plays a very important role on the shear and flexural frequencies of a fluid-conveying SWCNT. Meanwhile, the influences of the nonlocal parameter, fluid velocity, flow density, temperature change and magnetic field on the critical stress of a fluid-conveying SWCNT are discussed. This study may be useful for the design of smart nanodevices for the delivery of drugs to cells, carrying gases, and other applications of nanobeam devices.

The simulation of the satellite rendezvous and docking is one of most important problems for space platforms and so on. The nonlinear dynamic behavior of the satellite rendezvous and docking was investigated. According to the energy principle,the Lagrange function was given; then,the generalized coordinates,generalized momentum and Legendre transformation were introduced to derive the Hamilton equations; both the symplectic Runge-Kutta method and the 4th-order Runge-Kutta method were comparatively used to solve the Hamilton equations. Through numerical analysis,it is easily found that the natural properties of the nonlinear dynamic system are well preserved with the symplectic Runge-Kutta method,especially in the long-time chasing cases. The proposed symplectic method is applicable to the related astrodynamic problems.

In the present study, forced vibration of a simply supported embedded curved single-walled carbon nanotube (ECSWCNT) subjected to a moving harmonic load is investigated based on nonlocal Euler-Bernoulli beam theory. By using a single-mode Galerkin approximation method, the nonlinear integral-differential equation governing the motion of the nanotube is converted into a second-order nonlinear ordinary differential equation. The differential equation of the model is solved using Magnus expansion method which is one of the geometric integration methods. In the numerical calculation, the effects of nonlocal parameter, aspect ratio of ECSWCNT, velocity and the elastic medium constant is discussed. The results show that the above mentioned effects play an important role on the dynamic behavior of ECSWCNT.

The effects of an imperfect horizontal strut of two-layer fully triangular grid material on the stress distribution are investigated analytically and numerically.Based on the structural variation method,an analytical equivalent model was proposed to quantify the influence of the imperfect strut on the stress distribution of the structure.The results show that the influence is independent with the imperfection degree and the stresses caused by the imperfect strut are decaying in a fixed rate that is equal to the Saint-Venant decay rate obtained by the transfer matrix method.The finite element simulations are used to validate the predictions.

Based on the continuum mechanics and elastic beam model,the nonlinear vibration of embedded single-walled carbon nanotube with clamped-clamped boundary condition is investigated,where the carbon nanotube is modeled as a harmonically excited beam under a transverse force.By using a single-mode Galerkin approximation method,the nonlinear integral-differential equation governing the motion of the nanotube is converted into a second-order nonlinear ordinary differential equation.The differential equation of the model is solved using Magnus expansion method which is one of the geometric integration methods.In the numerical calculation,the amplitude-frequency response curves for embedded single-walled carbon nanotube are analyzed,the effects of the surrounding elastic medium on the amplitude-frequency response characteristics are discussed,the periodic orbits and their bifurcations are obtained,the nonlinear dynamic theory shows that a sequence of period-doubling bifurcations leading to chaos.

在无刷直流电机数学模型的基础上,在第四工作象限下分析了120°斩波方式与全桥单级斩波方式对无刷直流电机转矩脉动的影响.得到了在不同斩波方式下,导通相电流与非导通相电流的脉动对转矩脉动所产生的影响的相关结论.给出了可以避免非导通相的导通对转矩脉动影响的斩波方式.最后通过Matlab进行了仿真验证.

The creeping flow in a wedge shaped geometry is commonly encountered in a revolving mechanical device.The traditional solution is to solve the laplace equation,the possion equation or the biharmonic equation in the Lagrange system,which will lead to the difficulities of solving the high order partial differential equations and treating the mixing boundary conditions.The symplectic analytical method is introduced for solving the problem of the creeping flow in wedge cavities driven by the radial boundary walls.Simulating radial coordinate r as time,the dual variables of velocities are found and the Hamiltonian function is achieved by the Legendre transformation.Taking velocities and dual variables as the basic variables,the Hamiltonian formulation can be introduced into creeping flow problems and a direct method is put forward.The solutions of the problem are composed of a general solution and a particular solution.In the symplectic space the general solution can be solved via the method of separation of variables and expansion of eigenfunctions,whilst the particular solution can be obtained by solving the homogeneous equation and the non-homogeneous boundary conditions.Numerical results show that the symplectic method is effective for creeping flow problems in the wedge cavities.

In this paper,the axisymmetric creeping flow problem is solved under Hamilton system by algebraic method.The biharmonic equation of creeping flow in cylindrical coordinate is a linear partial differential equation with variable coefficients which can be transformed into the infinite dimensional Hamilton system so that the Hamilton system is equivalent to the original equation and the introduced variation is as little as possible.This method includes the criterion principle and concretes the canonical infinite dimensional Hamilton representations instead of finding out the Legendre′s transformation and the Hamiltonian.By using the above method,the entry flow into a circular tube is studied,and the corresponding inlet length is equal to 1.2 times the radius of the tube.The results show that the algebra Hamilton method is effective and with high precision.

This paper presents a Symplectic method in circumferential direction to determine the Stokes flow in an annular cavity.The flow is drawn across the radial direction with constant velocities.Taking velocities and their dual variables as the basic variables,the Hamilton formulation can be introduced into Stokes flow problems.Then the non-zero eigenvalues and their eigenvectors for the Symplectic eigenvalue problem in circumferential direction are obtained.Using the two ends boundary conditions to determine the coefficients,the method of eigenvector expansion can be used.The results of the examples show that the Symplectic method is effective.

We present a symplectic analytical method for the study of two-dimensional low Reynolds number flow in a wedge-shaped cavity caused by constant unit tangential velocity of the curved wall.Taking velocities and their dual variables as the basic variables,the Hamiltonian formulation can be introduced into low Reynolds number flow problems and a direct method is put forward.In the symplectic space,the problem can be solved via the method of separation of variables and eigenvector expansion.The flow is anti-symmetric with respect to the polar axis,and all values towards the wedge vertex are necessarily finite,so its expansion is composed of the anti-symmetric solution with eigenvalues whose real parts are positive.The direct method is employed to solve the flow problem in the wedge cavity with special corner angle values.Results show that the wedge cavity consists of a sequence of eddies separated by the zero-value streamlines which intersect the wedge lateral wall,and the adjacent eddies rotate in the opposite sense.Numerical examples show that the Hamiltonian method is effective for low Reynolds number flow problems in polar coordinates.

This paper presents a Hamiltonian analytical method to determine the Stokes flow in an annular cavity.The flow is induced by a rotation of the curved walls with prescribed constant unit velocities.Taking velocity and its dual variables as the basic variable,the Hamiltonian formulation can be introduced into Stokes flow problems.In the Symplectic space the problem can be solved by using the method of separation of variables,and the original problem is reduced to finding zero eigenvalue eigen-solutions and non-zero eigenvalue eigen-solutions.Based on the adjoint Symplectic orthogonality relationship between eigenvectors of Hamiltonian matrix,the solutions of equation can be obtained by eigenvectors expansion.Substituting them into the of boundary conditions two ends and determining the related constants,the analytical solutions can be derived.Finally,two examples are given to illustrate the Symplectic method.The results of the examples show that the Symplectic method is effective,and our method is applicable to other Stokesflow in a two-dimensional polar region,thus widening the application of the Hamiltonian system.

VxWorks as a real-time multitask operating system designed by Wind River Inc is used in embedded fields widely.For a VxWorks system engineer,serial driver may be needed to be solved frequently.As a basic step,serial driver is absolutely necessarily in the development of BSP and application programs.This paper focuses on the serial driver in S3C44B0X,whose architecture and powerful instruction set with ARM7TDMI CPU core,and discusses the hierarchy and corresponding mechanism about serial driver.In addition,it stresses on the operational principle about the tty driver and the SCC driver.The design method,approach and notes of ARM 's serial driver are explained with writing and parameter setting S3C44B0X's driver.

面向先进主动流动控制,在国内率先研发了一种基于微机电系统(MEMS)的气泡型微致动器阵列技术.分析了气泡型微致动器用于主动流动控制的原理,阐述了致动器结构及其加工工艺.通过对气泡样件的压力载荷-变形行为的测试,表明其具有较好的线性和较大承载能力.结合不同翼型的风洞试验表明,微致动器作动可以影响翼型表面的压强分布,从而可用于增升等控制目的.

With the wide application of bar code identification technique,more attention is focused on the requirements of intelligence,small size and low cost.Aimed at this issue,it is a wise choice that we use ARM embedded processor based on Linux as platform to design a portable handheld bar code scanner.The design circuit,Linux driver realization method and application software development of MiniGUI are described.Now,the design and test of the device has been accomplished,and the experiment results reach the expectation.In addition,this design is a good reference of application and development based on embedded Linux.

FS1016 4 800 bit/s is the Federal Standard for speech coding based on the excited linear prediction technique.It is widely used in the speech communication in the narrow band with high quality.The standard of FS1016 4 800 bit/s and the principle of CELP are introduced,and the coder and encoder based on the standard are simulated.