一、前言基底隔震系统在地震工程界已受到极大的重视。已经出现了许多隔震方案,像弹簧质量系统、柔性底层概念,特别是滚轴隔震系统和迭层钢板橡胶支座。曾采用过许多模型研究隔震系统的效果。最近,文献(L. Su, G. Ahmadi and I. G. Tadj...一、前言基底隔震系统在地震工程界已受到极大的重视。已经出现了许多隔震方案,像弹簧质量系统、柔性底层概念,特别是滚轴隔震系统和迭层钢板橡胶支座。曾采用过许多模型研究隔震系统的效果。最近,文献(L. Su, G. Ahmadi and I. G. Tadjbakhsh, 1989)中利用数学模型对那些物理模型进行了分类。作为最简单的一个模型,Younis与Tadjbakhsh(1984)、Westermo与Udwadia(1983)和Crandall等(1974)都采用过图1(a)所示的在基础上滑移的一个刚块。当模型受谐和激励时,可以观察到刚块随时间作周期运动。展开更多
A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distributi...A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distribution and pressure distribution are deduced from theNavier-Stokes equation on the basis of a laminar flow when the membrane rotates at the speed of Asin(αt). And then the shear stress, shear force, moment of force on the membrane surface and powerconsumed by viscous force are calculated. The velocity distribution demonstrates that the phase ofmembrane velocity does not synchronize with that of shear stress. The simple harmonic motion canresult in self-cleaning, optimize energy utilization, provide the velocity field with instability,and make the feed fluid fluctuation. It also results in higher shear stress on the membrane surfacethan the constant motion when they consume the same quantitative energy.展开更多
The harmonic oscillator with time? dependent frequency and driving is studied by means of a new, simple method. By means of simple transformations of variables, the time dependent Schrdinger equation is first tr...The harmonic oscillator with time? dependent frequency and driving is studied by means of a new, simple method. By means of simple transformations of variables, the time dependent Schrdinger equation is first transformed into the time independent one. And then exact wave function is found in terms of solutions of the classical equation of motion of the oscillator.展开更多
The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering t...The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering the effects of several system parameters such as the mean speed,flow velocity,axial added mass coefficient,mass ratio,slenderness ratio,tension and viscosity coefficient.Numerical results show that when the pulsation frequency of the axial speed is close to the sum of first-and second-mode frequencies or twice the lowest two natural frequencies,instability with combination or subharmonic resonance would occur.It is found that the beam can undergo the periodic-1 motion under subharmonic resonance and the quasi-periodic motion under combination resonance.With the change of system parameters,the stability boundary may be widened,narrowed or drifted.In addition,the vibration amplitude of the beam under resonance can also be affected by changing the values of system parameters.展开更多
Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures.Therefore,a thorough investigation on the formation and characteristics of longperio...Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures.Therefore,a thorough investigation on the formation and characteristics of longperiod ground motion is desirable for engineering applications.In this work,an analytical study is performed to examine the effect of several parameters and the combining mode for equivalent harmonic components on the dynamic response of systems.The results of the work show that the harmonic components in equivalent ground motion are evidently influenced by the intensity rise time,duration,phase and combining mode.Moreover,the long-period ground motions are simplified and simulated by separate harmonic components through proper combination.The findings of the work are believed to be useful in the selection of input ground motion in structural seismic analysis.展开更多
文摘一、前言基底隔震系统在地震工程界已受到极大的重视。已经出现了许多隔震方案,像弹簧质量系统、柔性底层概念,特别是滚轴隔震系统和迭层钢板橡胶支座。曾采用过许多模型研究隔震系统的效果。最近,文献(L. Su, G. Ahmadi and I. G. Tadjbakhsh, 1989)中利用数学模型对那些物理模型进行了分类。作为最简单的一个模型,Younis与Tadjbakhsh(1984)、Westermo与Udwadia(1983)和Crandall等(1974)都采用过图1(a)所示的在基础上滑移的一个刚块。当模型受谐和激励时,可以观察到刚块随时间作周期运动。
文摘A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distribution and pressure distribution are deduced from theNavier-Stokes equation on the basis of a laminar flow when the membrane rotates at the speed of Asin(αt). And then the shear stress, shear force, moment of force on the membrane surface and powerconsumed by viscous force are calculated. The velocity distribution demonstrates that the phase ofmembrane velocity does not synchronize with that of shear stress. The simple harmonic motion canresult in self-cleaning, optimize energy utilization, provide the velocity field with instability,and make the feed fluid fluctuation. It also results in higher shear stress on the membrane surfacethan the constant motion when they consume the same quantitative energy.
基金National Natural Science Foundation (K19972 0 11)
文摘The harmonic oscillator with time? dependent frequency and driving is studied by means of a new, simple method. By means of simple transformations of variables, the time dependent Schrdinger equation is first transformed into the time independent one. And then exact wave function is found in terms of solutions of the classical equation of motion of the oscillator.
基金supported by the National Natural Science Foundation of China(Nos.11972167,12072119,12102139).
文摘The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering the effects of several system parameters such as the mean speed,flow velocity,axial added mass coefficient,mass ratio,slenderness ratio,tension and viscosity coefficient.Numerical results show that when the pulsation frequency of the axial speed is close to the sum of first-and second-mode frequencies or twice the lowest two natural frequencies,instability with combination or subharmonic resonance would occur.It is found that the beam can undergo the periodic-1 motion under subharmonic resonance and the quasi-periodic motion under combination resonance.With the change of system parameters,the stability boundary may be widened,narrowed or drifted.In addition,the vibration amplitude of the beam under resonance can also be affected by changing the values of system parameters.
基金Supported by Major Research Plan of National Natural Science Foundation of China(No.91215301)National Natural Science Foundation of China(No.51238012,No.51178152,No.51008208)the Special Fund for Earthquake Scientific Research in the Public Interest(No.201208013)
文摘Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures.Therefore,a thorough investigation on the formation and characteristics of longperiod ground motion is desirable for engineering applications.In this work,an analytical study is performed to examine the effect of several parameters and the combining mode for equivalent harmonic components on the dynamic response of systems.The results of the work show that the harmonic components in equivalent ground motion are evidently influenced by the intensity rise time,duration,phase and combining mode.Moreover,the long-period ground motions are simplified and simulated by separate harmonic components through proper combination.The findings of the work are believed to be useful in the selection of input ground motion in structural seismic analysis.
