对比地

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。

At the same time, girls here are dancing beautifully in the hall,focusing every little attention on their motions.They have determined to make their performance a perfection at the celebration of the school's 100th anniversary.

与之形成鲜明对比的，则是在形体房内曼妙舞动的女孩子们，她们专心致志地纠正每一个动作，只为在校庆庆典上展现出自己的最美。

Based on kinetic experiments, the reaction and deactivation kinetic models are obtained by least square method.

对比实验数据和模拟结果表明，该模型可以较好地模拟稳态条件下的反应过程特征。

This paper introduces the basic theory to develop coalbed methane reservoir. It compares coalbed methane reservoir with conventional natural gas reservoir on geology and production characteristics, and explains the storage and migration mechanism in detail. And it also provides a set of new integrated mathematics, numerical model for the simulation of degasification process from coalbed seams. At last, it presents a significant computer software corresponding with the model.

为此，本文从煤层甲烷的开发基础入手，对煤层气藏与常规天然气藏储集特征和开采特征进行了综合对比分析研究；通过对煤层气藏的赋存、运移机理的深入研究，首次建立了一套完整的煤层甲烷运移的数学模型、数值模型，并研制开发了相应的计算机模拟模型，创造性地建立了一套煤层甲烷气藏开发动态评价和预测的理论和方法，对煤层气藏的开发具有重要的实际意义和重要的指导作用。

A biblical theist not only believes that the one, living God is separate from the world, as against pantheism and panentheism, but also that God is continuously active throughout the world providentially, in contrast to deism.

一个圣经者不仅认为，一个，活着的上帝是脱离世界，因为对泛神论和panentheism ，但也相信上帝是不断地活跃在世界各地的providentially ，形成对比的自然神论。

Three methods were compared,the results showed that the mothod——rceirculation fumigation under film through PH 3 dynamic deliquescence can reduce fumigation spaces effectively,save CO 2,control the moisture content losses of grain bulk,and the phosphide residue in grain were in accord with the national health standard,the effect of controlling stored-grain insects was obviously.

三种方法的对比试验表明，膜下动态潮解法，有效地减少了熏蒸空间，节省了CO2 ，控制了粮堆的水分散失，粮食中的磷化物残留量低于国家卫生标准，杀虫效果显著。

During the calculation the results got by quintic spline kernel was the best so it was chosen as the proper kernel for the SPH simulation. By comparison of the simulation results got by SPH and finite volume method, it was proved that the buffer cells method proposed in the SPH simulation to implement the Dirichlet boundary conditions was accurate, and this is of great importance for the simulation of flows pass a pipe. At last, the SPH method was improved to simulate the liquid-solid two phase flows and the results show that this method was appropriate for the simulation of flows containing viscous fluid and macroscopic solid components. Now the two methods are both able to predict the continuum flows and rarefied flows severally, but the hybrid program still has some aspects to be improved.

首先用标准算例验证了SPH方法的理论模型和计算程序的准确性；通过比较确定选用五次样条核作为计算低雷诺数下的粘性连续流动时的核函数；采用SPH方法和有限体积法分别对同一管道流动进行了对比计算，证明了本文提出的边界缓冲区方法在实现SPH方法中的流体边界条件时的有效性，解决了SPH方法模拟管道流动时的一个关键问题；巧妙地使用SPH方法对化工分离流动中常见的固液两相流及固液耦合作用进行了模拟尝试，获得了较好的结果；在跨尺度计算方面，目前两个子程序已经能够分别模拟连续的和稀薄的二维管流问题，二者的耦合计算程序还处于调试和优化阶段，各个参数对于计算精度和计算速度的影响规律仍在探索中。

Similarly, at the Canton Trade Fair in October, vendors hawking familiar-looking silver and black slabs were convulsed in crowds, in sharp contrast to the deserted booths of rival brands, where lonely salesmen slurped disconsolately at noodles.

在10月份举行的广交会上，兜售外形与之之相似的银黑相间的手机的商贩被人群前呼后拥，与无人问津的品牌展位形成鲜明对比：孤独的销售人员郁郁寡欢、"稀溜稀溜"地吃着面条。

In stark contrast to bankers' doom-laden predictions about the City's imminent demise, and defections of hedge funds amid relocations of some staff to Switzerland by prominent funds such as BlueCrest Capital and Brevan Howard, Toscafund is convinced the growth of the Bric nations Brazil, Russia, India and China can only work to London's advantage.

此前一些银行家悲观地预测称，伦敦金融城即将日落西山，对冲基金即将撤离，因为BlueCrest Capital 和 Brevan Howard等知名对冲基金要将一些员工转移到瑞士，而Tosca基金的态度与它们形成鲜明对比。Tosca确信，巴西、俄罗斯、印度和中国的增长只会对伦敦有利。

In stark contrast to bankers' doom-laden predictions about the City's imminent demise, and defections of hedge funds amid relocations of some staff to Switzerland by prominent funds such as BlueCrest Capital and Brevan Howard, Toscafund is convinced the growth of the Bric nations ndash; Brazil, Russia, India and China ndash; can only work to London's advantage.

此前一些银行家悲观地预测称，伦敦金融城即将日落西山，对冲基金即将撤离，因为BlueCrest Capital 和 Brevan Howard等知名对冲基金要将一些员工转移到瑞士，而Tosca基金的态度与它们形成鲜明对比。Tosca确信，巴西、俄罗斯、印度和中国的增长只会对伦敦有利。

Finally, according to market conditions and market products this article paper analyzes the trends in the development of camera technology, and designs a color night vision camera.

最后根据市场情况和市面上产品的情况分析了摄像机技术的发展趋势，并设计了一款彩色夜视摄像机。

Only person height weeds and the fierce looks stone idles were there.

只有半人深的荒草和龇牙咧嘴的神像。