查询词典 instability

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。

The high frequency combustion instability in liquid rocket engine LRE is analyti cally studied by usin g CFD methods.The comprehensive model and governing equations for numerical simu lation of high frequency combustion instability are presented.The PISO and MacCo rmack algorithms are compared in this study.Both methods can successfully handle combustion instability analysis.

应用CFD方法对液体火箭发动机中的高频燃烧不稳定性进行了分析研究，建立了液体火箭发动机不稳定燃烧数值模拟的综合模型和控制方程，比较了PISO和Ma cCormack两种算法，得出了两种算法均能成功应用于不稳定燃烧分析的结论。

The larger subharmonic component will be introduced into the system after the instability of system periodic motions, the motion of systems will be nonsynchronous precession and the amplitude of alternate stress in the rotor shaft is high. The long-term existence of instability will directly threaten the safe running of the rotor systems. Research on the influence of the change of system parameters on the system dynamical behaviors, the stability of system periodic solutions with the change of system rotational speed and the system motion after instability will have the theoretical and engineering-oriented significance for the long-term safe running of large-scale rotating machinery.

转子系统失稳后会产生较大的低频振动分量，系统运动出现非协调进动，系统转轴中会产生幅值很大的交变应力，转子失稳状态的存在直接影响系统的安全运行，因此研究转子系统自身参数的变化对系统动力稳定性的影响，研究系统周期解随工作转速的变化情况及其失稳后的运动规律，对大型旋转机械的安全稳定运行具有重要的理论意义和工程实用价值。

Overbreak excavation instability and local instability are indicated on the phase of construction about soil nail wall on the base of different instability situation about two cases,when excavation beginning.

结合两个纯土钉墙工程实例，根据工程失稳时新开挖土层的不同失稳现象，提出了土钉墙施工失稳有超挖失稳和局压失稳两种类型。

Fracture is caused by sheet's tensile instability, Hill's totalized instability theories and Swift's diffuse instability theories which based on continuous mechanics are applied to isotropic blank; Marciniak and Kuczynski's theories are applied to orthotropic blank, which introduced thickness imperfections normal to the principal stress and strain direction as a groove pre-existing defects in the material. The stability of each part of blank at each moment is described by numerical method, and the results are shown by computer simulation, thus the fracture in sheet forming can be predicted preciously.

拉裂是由于拉伸失稳引起的，以连续体力学为基础的Hill集中性失稳理论和Swift分散性失稳理论应用到各向同性板料进行失稳判定；将Marciniak和Kuczynski的凹槽损伤失稳理论应用到正交各向异性板料拉伸失稳判定，对板料各处在成型过程中不同时刻的稳定性进行数值化描述，并运用计算机仿真技术进行直观的表现，可以准确地预测板料成型中可能出现的拉裂现象。

Firstly, we simulate the influence of pump waves on two-stream instability occurred at heights of equatorial ionospheric E region. The simulation results show that pump waves can control the two-stream instability, that's to say, pump radio can stabilized or unstabilized this instability.

首先，模拟了加热泵波对赤道电离层E区双流不稳定性的影响，模拟结果定性地表明，在一定条件下，加热泵波对发生在该区域的双流不稳定性有很好的致稳或不稳作用。

The region where it produces two-stream instability is encircles by three boundaries: the outer open field lines, the nearest distance where the instability could take place (corresponding the charactistical frequence is equal to the plasma frequence), and the largest distance where the instability could take place along field lines.

可以发生双流不稳的区域是由三个边界面围成的：一是最外的开场线。一是不稳定性可以发生的最近距离(对应于曲率光子特征频率等于等离子体频率的地方)，最后是沿磁力线能够激发起双流不稳性的最大距离。

Based on both the strong-weak model and the strong-strong model, the instability caused by ions in equilibrium is simulated, some useful results are obtained. The results include the relation between instability growth rate and neutralization factor, the relation between instability threshold and neutralization factor, and the incoherent tune shift, the tune spread, the ion cloud distribution, the ion loss mechanism, as well as the ion accumulation limitation in the storage ring. With this understanding, we have carried out theoretical and experimental study for some ion clearing methods and their effects for the HLS ring. The minimum static clearing voltage is determined through calculating beam electric field and measuring ion current.

在上述基础上，我们对各种离子清洗的方法及清洗效果进行了理论和实验的研究：通过计算束流电场和测量清洗电极上的离子流来确定直流清洗电极所需的最小清洗电压；通过测量离子引起的频移来计算储存环的中性化系数；用模拟计算和实验测量证实了高频清洗能有效地克服储存环上离子俘获不稳定性；对由高频剔除系统形成的储存环部分束团填充模式下的离子俘获问题进行了初步研究，证实采用束团部分填充模式能在一定范围内克服离子俘获效应；并对各种离子清洗方法进行了比较。

Instability of two-dimensional jets has been studied by numerical analysis and experiments based on the theoretical framework of absolute and convective instability.

在绝对／对流不稳定理论框架下，从粘性方程出发系统分析了二维均质射流稳定性。

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 father that if work,mad father, love annoys, disposition is too indrawn the be short ofing that the father of Mu Ne, resign oneself to adversity causes father easily to love is broken; Communicate time effectively between father and son, Mu Zizhi to be less than a hour on average to wait a moment every week, it is the cause that causes the child to become addiction.

如工作狂的父亲、爱愤怒的父亲、性格过于内向木讷、逆来顺受的父亲都易造成父爱的缺失；父子、母子之间的有效沟通时间每周平均小于一小时等等，都是造成孩子成瘾的原因。

These are vandal proof and they come with a locking mechanism.

这是野蛮的证据，他们来到了锁机制。