使不稳定

So welfare opportunities are a significant determinant of family instability in poor neighborhoods, but this is not the result of AFDC regulations that exclude most intact families from coverage .

所以福利机会在贫困社区是使家庭不稳定的重要的决定性因素，但家庭不稳定并非将多数完整家庭排除在未成年子女家庭补助之外这一制度的结果。

The effect of tribology factors on bearing vibration is studied experimentally. AR model and WPT are used to processing the normal arid abnormal signals. The results are as follows:1. The vibration of ball bearings is caused by the tribology action of contact pairs of ball and ring races and has the essential of tribo-dynamics. Any factors affecting the tribology characteristics of contact pairs will affect vibration and noise of bearings consequently.2. Vibration characteristics of bearing keep almostly unchanged with the increasing of axial load expecting the increasing of nature frequencies. When radial load increasing with axial load unchanged, nature frequencies keep unchanged but some new vibration peaks appears in the spectrum.3. Vibration amplitudes are damped and nature frequency are enhanced with sufficient lubrication. Vibration and noise of bearings increase obviously and roar can happen and the contact surfaces scratch slightly under insufficient and unclean lubrication state. Bearing will be disabled in a few minutes without any lubrication.4. Bearing vibration is unstable under low speed. With the speed increasing, the vibration become stable and natural frequencies increase slightly but the amplitudes increase apparently.5. Bearing vibration can be excited only by some harmonics ofwaviness without lubrication and by all harmonics with lubrication based on the theoretical analysis.6. The nature frequencies of ball bearings decrease with the increasing sizes. When international clearance increasing, nature frequencies decrease in radial and increase in axial and angular and the amplitudes increase in radial and decrease in axial and angular. When the number of balls increasing, nature frequencies increase and amplitudes decrease. When the pitch diameter increasing, axial nature frequency increase and others nearly keep no change. When outer race groove curvature radius increasing, nature frequencies increase in radial and decrease in axial and angular and amplitudes keep no change in radial and increase in axial and angular. When inner race groove curvature radius increasing, nature frequencies decrease and amplitudes increase.7. The distortion in amplitude and frequency components of bearing vibration signals picked up by the present probe measurement method is founded and right conclusions cannot be achieved by the signals. When accelerometer is rigidly screwed with steel stud onto a flat outer surface of a ball bearing, vibration signal can be got without distortion and the reliability of research on bearing vibration is assured.8. AR model is suitable for large samples of bearing vibration signals, square root of length of samples can be used as the upper limitation of order determination and the FPE order selection criterion is effective. Many advantages of AR spectrum are founded over the classical based on FFT.9. Time-Frequency analysis is necessary for abnormal noise of ball bearings. WPT overcomes the principle shortcomings of STFT and proved to be a best tool to process the abnormal signals.

理论分析和试验研究表明： 1球轴承振动是钢球—滚道接触副中的各种摩擦学作用引起的，具有摩擦动力学的本质，任何对接触副的摩擦学特性有影响的因素都将对球轴承的振动和噪声特性产生影响； 2中心轴向载荷作用下，载荷增大使球轴承的固有振动频率升高，载荷越大同样的载荷增幅引起的频率升幅减小，足够大的中心轴向载荷作用下载荷的变化对球轴承振动的频率特性不会产生明显的影响； 3轴向和径向联合载荷作用下，径向载荷不大时球轴承振动的固有频率基本不变，但是可能引起变刚度激励的非线性振动，出现新的频峰，过大的径向载荷将使部分钢球脱离接触，使球轴承的振动和噪声呈现不稳定状态； 4润滑对球轴承的振动和噪声特性有重要的影响，良好的润滑对振动有明显的抑制作用，润滑不充分时，振动和噪声的水平会有明显增高，一定条件下还会激发接触副中的谐振，发出啸声，造成接触表面的伤害，无润滑干接触时，短时的运转就会损伤接触副表面，使振动和噪声迅速增大，并随时可能引发严重的磨损和卡滞失效；接触副润滑良好时，油膜的"刚化效应"使球轴承振动的固有频率有所提高，润滑剂中含有弥散性污浊时，振动的幅度总体升高，但弥散性污浊不会改变球轴承振动的频率特性；浙江大学博士学位论文：球轴承振动的研究 5低速时，球轴承振动的基本特征呈现不稳定状态，随着转速的提高，球轴承振动的频率特性趋于稳定，固有频率频峰升高； 6理论分析表明，干接触时钢球和滚道表面波纹度的某些谐波分量能激励球轴承的振动，振动的幅值与谐波幅值成正比，实际球轴承中钢球的分布不可能完全均匀，波纹度的激励作用会随时发生；润滑接触的分析表明，波纹度的任意谐波分量均能激励球轴承的振动； 7球轴承的几何和结构参数分析表明，球轴承尺寸越大，径向、轴向和角振动的固有频率越低；钢球中心圆直径增大，球轴承的径向和轴向振动的固有频率基本不变，角振动的固有频率有所上升，振动的幅频特性基本不变；径向游隙加大使球轴承的径向振动固有频率降低，轴向和角振动的固有频率有所升高，径向振动幅频特性的幅值升高，而轴向和角向降低；钢球的数量增多使球轴承振动的固有频率上升，幅频特性的幅值下降，径向振动的幅值下降最为明显；外圈沟曲率半径系数增大使球轴承径向振动的固有频率升高，轴向和角振动的固有频率降低，径向幅频特性基本不变，轴向和角向幅频特性幅值升高；内圈沟曲率半径系数增大使径向、轴向和角振动固有频率均下降，振动幅频特性的幅值均有升高； 8试验对比表明，传感器采用探针式安装时，由于探针接触副接触特性的影响，钡(量得到的球轴承振动信号有失真，采用专门设计和制作的试验球轴承，以固定式安装加速度计，首次测量得到了球轴承振动的真实信号，通过对振动信号的分析，验证了球轴承振动的理论模型； 9)基于时间序列分析的AR模型适用于大样本球轴承振动信号的分析，以样本长度的均方根值作定阶上界，FPE做判阶准则，给出的AR谱光滑，频率分辨率高，是球轴承振动分析的简便而可靠的手段； 10以时频域分析的小波包变换分析球轴承异音信号能够比较好地定位和聚焦异音发生的时间，时间间隔，频率范围，同样是球轴承振动分析的可靠的手段，可用作球轴承故障诊断技术。

Numerical tests are also conducted to investigate the microphysical effects to the mesocale convective systems. The evaporation of raindrops can strengthen the surface "cold pool" to decease the temperature of rainfall center. The condensation of vapor can lower the air pressure and increase the convergence and updraft so that the convective echo develops stronger. The melting of graupel can cool the air to restrain the convective activity. The falling of precipitation particles can increase the downdraft and induce the outflow nearly the surface. The effect of condensation is the most important among all the microphysical processes. It can change the whole structure of cloud system.

微物理过程对对流系统发展和维持有重要作用：强降水的雨滴蒸发过程会加强"冷池"效应，同时增强了雨带南侧原有的地面中尺度辐合线；凝结潜热在低层诱发了与回波相应尺度的中尺度低压，增强了辐合和上升运动，促进对流发展；霰的融化吸热通过冷却大气会不利于气压下降、气流辐合抬升等过程，降低对流不稳定能量，减缓对流发展；重力拖曳使气块冷却降温，降低对流不稳定能量，并且使低层的气压升高、气流辐散，在近地面附近产生出流，加强地面中尺度辐合线的强度。

Based on two algebra Riccati equation method especially the structure of the system Hamilton matrix and system observability theory, the role of invariant zeros in constructing system reduced order controllers was given. That is, by the suitable selection of free parameters of the system H(subscript ∞) controller, some points which were symmetry with the unstable invariant zeros about the imaginary axis became the stable poles of the system controller which were not observable and could be reduced from the system, thus could get further reduced order controller.

基于2代数黎卡提方程方法，特别是系统Hamilton矩阵的结构特点和系统可观测性理论，论述了不变零点在构造系统降阶控制器中所起的作用，即通过选择控制器的自由参量，使某些不稳定的不变零点关于虚轴对称的点构成系统控制器不可观的稳定极点，从而实现了控制器进一步降阶。

In addition to increasing the risk for making errors, failing to obtain enough sleep can yield a labile or unstable mood, making people very irritable.

此外，以增加风险为决策错误，未能获得充足的睡眠可以产生不稳定或不稳定的情绪，使人们很烦燥。

First, the problem of stabilizing a given periodic orbit in a chaotic system is discussed. Then, a method for the stabilization of an unstable focus point is presented, which does not require the location of the focus point. At last, a method for the synchronization of chaotic systems using neural networks is proposed.

首先给出了使系统稳定在某个给定的周期轨道上的方法；接着讨论了如何使系统稳定在某个事先未知的不动点上；最后，提出了一种基于神经网络的混沌系统的同步化方法。

When the bed morphology is in an unstable statement, the variation of bed resistance makes the flow unstable and forms seiche.

当床面形态处于不稳定状态时，河床阻力的变化使水流处于不稳定状态，形成假潮。

The results show that for a supersonic shear layer without reaction, a disturbance can make the shear layer become unstable, this results in one vortex or more than one vortex. The combination and seperation of vortex can intensify the mixing. But it is not easy for supersonic reacting shear layer with exotherm to become unstable with disturbance, and the effect duration is very long.

结果表明，对完全气体的超声速剪切层流动，一定的激励方式能使原先较为稳定的剪切层流动变得不稳定，产生单涡或多涡结构，发生多涡间的合并，使混合加剧；但对于存在放热现象的反应超声速剪切层流动，外加激励方式不易使流动从稳定变为不稳定，而且外加扰动的作用特征时间也较长，实际应用前景不乐观。

The technique of microwave sterilize and refreshing have overcome the uneven, no thorough, unsteady defects of microwave sterilize. It makes microwave sterilizes to be suitable to demand of stability , homoeothermic preserved , safe, hygiene and low cost for industrialization product. And it has got very satisfied effects after use.

其中微波杀菌综合保鲜技术克服了微波杀菌不均匀、不彻底不稳定的缺陷，使微波杀菌适合于工业化生产的稳定、常温保存、安全卫生、成本低廉的要求，经全国各地近百家企业的生产应用，取得了非常满意的效果。

The results show that stable organic sulfur is the main s9lfur form in ZY coal. Pyrite can be removed under all the atmospheres in the tests, except for nitrogen at 500℃ 1% O2-N2 atmosphere has strong reactivity to remove the stable organic sulfur in ZY coal, especially at 700℃. Under 1% O2-N2 atmosphere, not only a part of stable organic sulfurs can be decomposed, but also more stable organic sulfur-containing structure can be broken down into less stable one.

结果表明，对于ZY煤而言，黄铁矿和不稳定有机硫除在氮气气氛下500℃时热解不能全部分解外，在其他条件下热解时都可以分解。1%氧气对ZY煤中稳定的有机硫的分解有很强的促进作用，不仅可以脱除稳定的有机硫，还可以使更稳定的有机硫断裂生成次稳定的有机硫，在随后的AP-TPR-MS实验过程中，这部分硫在较低的温度下逸出。

I am accused of being overreligious," she said in her quiet, frank manner,"but that does not prevent me thinking the children very cruel who obstinately commit such suicide.""

客人们在卡罗利娜·埃凯家里，举止就文雅一些，因为卡罗利娜的母亲治家很严厉。

Designed by French fashion house Herm è s, this elegant uniform was manufactured in our home, Hong Kong, and was the first without a hat.

由著名品牌 Herm è s 设计，这件高贵的制服是香港本土制造，是我们第一套不配帽子的制服。