具有非线性阻尼的记忆型抽象发展方程的时间依赖吸引子

运用时间依赖空间中的过程理论和收缩函数方法以及更多细节性估计,研究了具有非线性阻尼和衰退记忆的抽象发展方程的解在时间依赖空间中的渐近性态,证明了时间依赖吸引子在空间E_t^{\theta }中的存在性。     

Gas damping force noise on a macroscopic test body in an infinite gas reservoir

We analyze here the force noise associated with the mechanical damping of a test body surrounded by a large volume of rarefied gas, considering the statistics of momentum exchange in inelastic molecular collisions. In addition to calculating the force noise on a cube, sphere, and cylinder, we discuss the limits in applying this analysis to experimental configurations in which the test body is surrounded by an enclosure that is only slightly larger than the test body itself.     

On the critical damping in multi-degree-of-freedom systems

The concept of criticality in viscously damped multi-degree-of-freedom systems is discussed. A necessary and sufficient condition for critical damping is presented. The fundamental physical basis is the same as in Beskos and Boley [ASME J. Appl. Mech. 47 (1980) 627], but numerical convenience is enhanced.     

YB叶片泵降噪途径的探讨

通过对ＹＢ型叶片泵的固体振动、液压冲击与脉动的噪声测定与分析，确定噪声源并探讨了对该类泵行之有效的降噪途径。文章对新颖的高次方程定子曲线特性进行了数学模拟，并确定其特征方程各系数，同时，文章又探讨了对减振槽的优化设计，以其最小压差、最低液压冲击作为目标函数，确定了减振槽最佳几何尺寸。     

Radiation damping in closed expanding universes

The dynamics of a coupled model (harmonic oscillator-relativistic scalar field) in Conformal Robertson-Walker (k = +1) spacetimes is investigated. The exact radiation-reaction equation of the source-including the retarded radiation terms due to the closed space geometry – is obtained and analyzed. A suitable family of Lyapunov functions is constructed to show that, if the spacetime expands monotonely, then the source's energy damps. A numerical simulation of this equation for expanding Universes, with and without Future Event Horizon, is performed.     

Wave Motions in a Two-Layer Fluid Driven by Small Oscillations of a Cylinder Intersecting the Interface

The plane problem of steady-state small oscillations of a horizontal cylinder located at the interface between two fluids of different densities and indefinite depth is considered in the linear formulation. Boundary integral equations for the surface source distribution are derived. The behavior of the distributed singularities at points of intersection of the body contour and the interface is investigated. The problem of oscillations of a circular cylinder is solved by the multipole expansion method. The apparent mass and damping coefficients of the radiation problem and the reflection coefficient of the problem of scattering of an impinging wave by a floating body are calculated.     

复测法测定气轨的粘性阻尼常量

运用解决天平不等臂的复称法的思想，设计了复测法测定气轨的粘性阻尼常量的方法。     

合肥光源储存环上八极磁铁的动力学效应分析

 为达到合肥光源二期工程通用模式的设计流强，在储存环上选择垂直方向β函数比较大的位置增加一组八极磁铁。该组八极磁铁对水平方向动力学孔径影响很小，虽然垂直方向动力学孔径明显减小，但仍然大于物理孔径，不会影响束流的注入积累过程。该组八极磁铁产生的垂直方向振荡频率分散可以提供ms量级的Landau阻尼时间，将明显增强抑制垂直方向束流集体不稳定性的能力。该组八极磁铁投入运行后，合肥光源注入积累过程明显改善，注入流强从无八极磁铁时的约100 mA提高到330 mA左右。     

Effect of viscous damping on power transmissibility for the vibration isolation of building services equipment

Vibration isolation plays an important role in both the vibration and noise control of building services equipment. To evaluate vibration isolation performance, the force transmissibility method is commonly adopted. However, increasing the damping effect in the force transmissibility method reduces both the resonance peak value and the isolation performance in the “isolation region”. The limitation of the method is that the transmitted displacement of a floor structure and the interaction of mounting points are neglected. To include the floor displacement and the interaction of mounting points, Mak and Su recently proposed the power transmissibility method to assess the performance of vibration isolation. In this paper, the effect of viscous damping on power transmissibility is investigated. A practical procedure for experimentally determining the damping ratio is also given.