曲率计

This paper used a method of curvature circle replacing general curve,the authors obtain twouniversal formulas calculating the inherent frequency of relative oscillation in miniamplitude be-tween columns that have general section curve.

本文应用曲率圆弧近似一般曲线的方法，导出了具复杂截面曲线的等截面柱体在另一柱体上微幅摆动时固有频率的一般计算式。

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。

The error is bringed because the post-vertex of the eyeglasses is not superposition with the post-focus of the objective of the dioptometer.

由于被测镜片的后表面曲率各不相同，致使镜片后顶点与焦度计物镜后焦点不相重合，因而造成测量误差。

ABSRTACT:Object to study the shape feature of the children′s corneal surface emmetropia with keratometry and corneal topography.

摘 要：目的应用角膜曲率计与角膜地形图仪研究儿童正视眼角膜表面形态特征。

Our investigation demonstrates that before refractive surgery the keratometer has a similar clinical value as that of corneal topography, and the △ Sim K value is related to the graphic pattern of corneal topography.

角膜曲率计与角膜地形图对术前角膜散光测量具有相似的临床价值，角膜地形图图形与参数△Sim K值有关。

Methods: A total of 366 eyes with keratoconus were subjected to wear proper RGPCL. Keratometer and corneal topography were used to determine the central cornea astigmatism, apex K value, apex decenteation distance, SRI and SAI before, 12 and 18 months after wearing RGPCL.

对圆锥角膜患者选配合适的高透氧RGPCL，分别于配戴前及配戴后12、18个月行角膜曲率计和角膜地形图检查，采集角膜中央散光值、锥顶K值、锥顶偏心距离、SRI、SAI等参数，进行统计学分析。

The Topcon KR-8100 automatic keratometry and the TMS-4 comeal topography can not be considered as interchangeable.

KR-8100自动角膜曲率计与TMS-4角膜地形图两种测量方法在临床上不能替代使用。

Objective To evaluate the agreement of measuring corneal power and astigmatism axis between automatic keratometry and corneal topography on ametropia' children.

目的 比较KR-8100自动角膜曲率计与TMS-4角膜地形图仪测量屈光不正儿童角膜屈光力及散光轴向的差异，并对两种测量方法进行一致性评价。

Methods Keratometric reading with Topcon KR-8100 automatic keratometry and comeal topography with the TMS-4 on 53 ametropia' children, 106 eyes were compared. Difference in measurements of steep meridian power magnitude Ks, flat meridian power magnitude Kf, astigmatism magnitude Ks-Kf and location as well between the two methods were assessed using paired t test.Bland-Altmann method was used to evaluate the agreement of the two methods.

采用KR-8100自动角膜曲率计及TMS-4角膜地形图仪对53例（106只眼）屈光不正儿童进行测量，应用配对t检验对两种方法测量的陡峭子午线角膜屈光力、平坦子午线角膜屈光力、角膜散光Ks-Kf大小及轴向进行比较，并应用Bland-Altmann分析对两种测量方法进行一致性评价。

The physical dimensions from ultrasound and keratometry,included axis length,anterior chamber depth,lens thickness,vitreous length and cornea refractive power.Both axis length and vitreous length were significantly correlated with refraction （correlation coefficient of 0.822 and 0.823,respectively）.

以13～25岁青少年为研究对象，应用眼科A型超声生物测量仪及角膜曲率计，由SAS软件支持，对240例近视眼屈光程度和屈光各要素（眼轴长度、前房深度、晶体厚度、玻璃体腔长度、角膜屈折力）测量值进行分析。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。