不稳定性

Absolute instability is a major physics limitation in the realization of the ultimate capability of gyro-traveling-wave tube.

绝对不稳定性是制约回旋行波管性能的主要因素之一。

A threshold current which brings about the transition to absolute instability was investigated.

分析表明，绝对不稳定性的起振存在一定阈值，起振电流对电子注参数和电路参数极其敏感，确定起振电流是稳定器件工作的前提条件。

In addition, the absolute/convective instability is studied, and the governing region in the parameter plane is declared. It is shown that the absolute instability may become predominant when the electric field or the surface tension is sufficiently large.

另外，研究了单流体射流的绝对和对流不稳定性，在参数平面上给出了它们的控制区域，发现在电场强度足够大或表面张力足够大时，射流可能由对流不稳定状态进入绝对不稳定状态。

The unstable fracture of scapular neck can be divided into two main types: absolute instability and relative instability, based on the stability of the glenoid fragment in the scapular neck fracture. The former needs early operation.

根据不稳定性肩胛颈骨折中的关节盂骨折块的稳定程度，可将其分为关节盂骨折块绝对不稳定和相对不稳定两类。

The numerical results show that lossy dielectric-load can heighten the start oscillation current of absolute instability, and increase depends on the magnetic field strength and the perpendicular-to-parallel velocity ratio of the electrons; The thickness of the lossy waveguide increases the start oscillation length of backward wave oscillation.

结果表明：损耗介质的加载，可以提高绝对不稳定性起振电流，提高的幅度依赖于工作磁场偏离饱和磁场的程度、电子束横纵速度比等；增加波导损耗介质加载的厚度，可以提高竞争模式的回旋返波起振长度。

In addition,Various methods of stability analysis of wakes behind bluff bodies arediscussed,among which the general theory of absolute/convective instability is strictlyformulized from stability equations of viscous flow;the theoretical foundation of stabil-ity analysis of time-average flows is also discussed from basic equations of fluids,andthe reason for the stability analysis of time-average flow can predict the frequency inthe saturation state is explaned.

此外，讨论了钝体尾迹稳定性分析的各种方法，其中从粘性流的稳定性方程出发严格推导了绝对/对流不稳定性的理论公式；从基本方程出发探讨了采用时均流场作稳定性分析的可行性，并解释了用时均流场作稳定性分析可以更好地预示饱和频率的原因。

The formation mechanism of the absolute instability and gyrotron backward wave oscillations is analyzed, and the methods to suppress the parasitical modes are discussed.The nonlinear theory model of gyro-TWT is consummated by considering the influence of tapered magnetic field and waveguide radius, electron velocity spread, and waveguide loss on electron beam-wave interaction. The large-signal characteristic of gyro-TWT, such as launching loss and absolute instability, are also analyzed in detail. This work establishes the foundation for the development of a gyro-TWT amplifier.

重点研究了两段损耗波导结构和损耗陶瓷结构回旋行波管中的电子注-波互作用，分析了绝对不稳定性和回旋返波振荡的形成机制和抑制寄生模式的方法；完善了回旋行波管的非线性理论模型，并考虑了磁场和波导半径渐变、速度零散、波导损耗等因素对注-波互作用的影响；详细分析了发射损耗、相位稳定性等回旋行波管的大信号特征，为回旋行波管放大器的研制奠定了基础。

This paper, with the analysis of the propagation characteristics in a lossy cylindrical waveguide and using small-signal theoretical dispersion relation, presents study on the device stability with influence of the absolute instability and the backward wave oscillation in TE01-mode lossy dielectric-load gyrotron traveling wave amplifier.

摘要该文从分析损耗介质加载金属圆波导中电磁波传输特性出发，应用回旋行波管放大器小信号色散方程，研究损耗介质加载结构TE01模回旋行波管放大器绝对不稳定性振荡和回旋返波振荡对器件稳定性的影响。

The absolute/convective instability of incompressible swirling flows and the temporalinstability of compressible swirling flows have been fully explored, whereas the absolute/convectiveinstability of compressible swirling fl.

从N－S方程出发，通过正则模方法，研究了超声速尾涡的绝对／对流不稳定性性质。

However, operating of the high current, the output power, gain, and efficiency of gyro-TWT will be degraded where the absolute instability, gyrotron backward oscillation and reflective oscillation occur to cause mode competition. Stability issues comprise the key factors limiting the performance of the gyro-TWT, therefore physical origins of spontaneous oscillations in the gyro-TWT are analyzed and characterized.

然而受限於操作高电流，磁旋行波放大器可能引发绝对不稳定性、磁旋返波振荡(gyrotron backward oscillation；gyro-BWO)及反射振荡，造成模式竞争而抑制原先操作模式的放大波，进而影响其输出功率、增益及效率。

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％。