查询词典 keep in contact

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。

They are respectively as follows:Ahow to enforce whatever concerning full-time teachers, Bhow to link up the education al courses, Chow to reform evaluating methods, Dhow to reform the curriculum , Ehow to establish good contact between in class and after class activities, Fhow to keep a good contact between school and out of school activities.

即：专任教师队伍建设问题，教育类课程的相互衔接问题，课程及教学内容改革问题，教学评价方法的改革问题及课内与课外、校内与校外的联系问题。

It is used for all parts of a ship where wood and metal come in contact, for it has a kind of oil to keep metal away from rust It can also stop the attack of white ants and other insects.

它能用于船体所有有木头和金属接触的地方，因为它能析出一种防止金属生锈的油，这种油还能阻止白蚁和其它昆虫的攻击。

Keep your hands in contact with the victim's sternum to maintain proper hand position.

使手与胸骨接触以保持正确手的位置。

Keep close contact with the stevedore to prevent unsuitable stowage which may result in the excessive list of the ship.

与搬运者保持联系，防止不合适的堆积。

Helpful Tips to Keep in Mind for Those Afflicted with Xeroderma Pigmentosum by dave4 Xeroderma pigmentosum is a rare medical condition whereby individuals are unable to have direct contact with the sunlight and other sources of ultraviolet rays.

帮助提示，以铭记那些患有着色性干皮病的dave4着色性干皮病是一种罕见的医学条件，使个人无法直接接触阳光和其他来源提供的紫外线。

It also helps us to keep track and in contact with those brave adventurers who test the boundaries of endurance and skill.

它还可以帮助我们了解和接触到那些勇敢的冒险者测试的界限耐力和技能。

It also helps us to keep track and in contact with those brave adventurers who test the boundaries of endurance and skill.

它还可以帮助我们跟踪和接触那些勇敢的探险者测试的界限耐力和技能。

Based on the simulation data, the effects of clearances, damping coefficient and the rotation speed on the dynamic behaviors are studied: compared with ideal mechanisms, mechanisms with clearances are less stable; as for mechanisms with clearances, when the crank rotates at the speed of 100rad/s, the actual clearances are always above the radium of clearances, axle pin and axle cover keep contact throught the rotation; when the crank rotates at the speed of 20rad/s, mechanisms are in an unstable state, at an angle of about 300, the actual clearances are below the radium of clearances, pairs lose contact, which results in collision between them; with the speed of 20rad/s, when damping coefficient is assumed 175Ns/m, distinct separation and collision happen between pairs; when damping coefficient is assumed 220Ns/m, separation and collision are controlled.

在含间隙机构中，当曲柄以100rad/s转动时，运动副间隙始终大於半径间隙，轴销与轴套始终保持连续接触；当曲柄以低速20rad/s转动时，系统处於极不稳定的震荡状态，在转至300°左右时，运动副间隙小於半径间隙，脱离接触，发生明显的分离碰撞现象。在含间隙机构中，曲柄以低速20rad/s转动，当取法向阻尼系数为175Ns/m时，副元素发生明显的分离碰撞现象；当取法向阻尼系数为220Ns/m时控制了副元素的分离，副元素一直处於连续接触状态。

Thanks to the good public praise and reputation in the industry, more and more professional managers and enterprises keep good contact with us and so that we have builtup a Century Sunshine High-grade Talents Bank.

由于在业界树立了良好的口碑和声誉，越来越多的职业经理及企业与我们保持良好的接触和联系，构建成世纪阳光高质量的人才库。

The labia have now been sutured together almost completely.The drains and the Foley catheter come out at the top.

此刻阴唇已经几乎完全的缝在一起了，排除多余淤血体液的管子和Foley导管从顶端冒出来。

To get the business done, I suggest we split the difference in price.

为了做成这笔生意，我建议我们在价格上大家各让一半。