不稳定性

PIC results show that the occurrence of absolute instability is determined by the operating current.

通过PIC模拟，给出了采用无损耗波导结构，且工作电流为25A和10A条件下的放大器频谱图和功率图，结果表明绝对不稳定性的出现与否主要由工作电流是否超过起振的阈值电流决定，损耗波导是抑制绝对不稳定性的有效手段。

The physical interpretations,character and suppressing methods of absolute instability were analyzed and verified by a W-band TE_(01) experiment.

通过回旋行波管色散方程，详细分析了W波段基波回旋行波管绝对不稳定性的形成和特征，提出了采用多段损耗波导来抑制绝对不稳定性的方法。

In the second chapter, we investigate propagations of desynchronous disturbances in synchronized chaotic one-way coupled map lattices. It is well known that spatiotemporally chaotic systems with large gradient couplings may show convective instability under the absolute stability condition of chaos synchronization. This convective instability is the key reason for the effective propagation of control signals.

时空混沌在不同的耦合系数情况下会表现出不同的动力学行为，用驱动实现具有强梯度耦合系数的时空混沌同步时，会观察到在绝对稳定条件下被驱动系统表现出对流不稳定性，这种对流不稳定性是在单个信号驱动下实现混沌同步的关键原因。

The basicflows are computed by a low-dimensional Galerkin method.The results confirm thattwo times global mode switching occur with increasing Re up to which the Hopf bifur-cation occurs when the absolutely unstable region cover the whole reversed flow region,and the first explanation of this phenomenon with absolute/convective instability theoryis given.

结果证实了只有当绝对不稳定性区域完全覆盖了回流区才会形成整体的Hopf分叉，此前随着Re数的增加整体模态经历了两次跳跃；并首次用绝对/对流不稳定性理论解释了这一现象。

In this paper the effect of the spatial gradients of the electric field and the neutral wind on the linear growth of the plasma R-T instability and its growth rate are analyzed, based on the quality and the charge conservation equation.

本文从质量和电荷守恒方程出发，分析了控制电离层等离子体R-T不稳定性线性增长的各种因素，重点研究了热层风和背景电场的空间梯度对R-T不稳定性线性增长的影响。

By dimensionless analysis, a predicting corelation on liquid sodium boiling density wave instability is obtained.

获得了大量液钠沸腾密度波不稳定性和其诸多静态不稳定性的实验曲线和数据。

The results show that the quintic nonlinearity plays a role similar to the case of neglecting the group-velocity mismatch in modifying the modulation instability, namely, the positive and negative quintic nonlinearities can still enhance and weaken the modulation instability, respectively.

结果表明，五阶非线性对调制不稳定性的影响与忽略群速度失配的情形是类似的，即正负五阶非线性分别能够增强和减弱调制不稳定性。

Numerical results demonstrated that there are three kinds of the instability for the under-expanded supersonic jets according to their shock cell structure patterns:(1) the regular reflection shock cell with a single shear layer,(2) the Mach reflection shock cell with two shear layers and (3) the curved Mach stem with a relatively high expansion ratio.

计算结果表明欠膨胀超声速射流的失稳机制根据射流激波结构的特征可分为3种失稳模式：具有规则反射激波结构和单一剪切层特征的射流不稳定性；带有马赫反射激波结构和双剪切层特征的射流不稳定性；具有弯曲马赫杆和高度欠膨胀射流的不稳定性。

The effects of shear stress, Reynolds number, wave number on the fluid film stability are analyzed.

结合切应力作用下液膜的流动状态，分析了表面波扰动在初发时刻的不稳定性，并着重描述引发不稳定性的各种物理原因。

The theory of accretion disks are important for many astrophysical phenomena, including Quasars, active galatic nucleic, X-ray binary stars, and young stellar objects. The most important branch of accretion djsk theory is the stability properties of djsks. It is widely considered that the luminosity variations of various astronomical objects are associated with the instability of accretion disk. The viscosity plays an important role in the accretion disk theory, and magnetic field exists commonly in astronomical phenomena. A more realistic analysis of the stabihty of the accretion disk should include both the radjal and azimuthal perturbations because of the strong shear of viscous flow.In this paper, according to the luminosity Variations of Various astronomical objects, we study the radial-azimuthal instability of an isothermal with magnetic field. We find that the radial and azimuthal fields B〓,B〓 are mainly responsible for enhancing the instability of the magneto-acoustic modes and non-axisymmetric modes,and that pulsational oscillations are larger in the radial than in the Z direction. The model may be useful in explaining the periodic light variation of FU orionis and. T Tauri stars.

在许多天体物理现象中，例如活动星系核，X-射线双星和年青的恒星理论中，吸积盘理论起着重要的作用，而吸积盘理论中的一个重要分支是吸积盘的不稳定性理论，普遍认为活动天体的周期，准周期光变现象与吸积盘的不稳定性有关，在吸积盘理论中，粘滞起着重要的作用，而磁场是天体物理中普遍存在的现象，对于几何薄吸积盘不稳定性分析，由于强剪切流的缘故，应该包括径向和环向扰动两个方面，本文结合天体物理中的各种周期，准周期光变现象，研究了含磁场的等温薄吸积盘的径向-环向振荡不稳定性，结果表明：磁场的径向和环向分量对磁声模和非轴对称模的不稳定性的增加起着主要的作用，且径向振荡大于轴向振荡，所得结果有利于解释FU Orionis和T Tauri Stars的周期光变现象。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。