查询词典 spectrum

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。

A necessary and sufficient condition for a fx + t(y + g to be a bent function is disscussed,on which basis a necessary and sufficient condition for a function F = fix + tq + g to be a bent function is given when q is not a balanced-function by use of cyclic walsh spectrum and decomposition formula of walsh spectrum.

讨论了形如fx+τ(y+g的布尔函数是Bent函数的充分必要条件，在此基础上利用Bent函数的循环Walsh谱及谱分解式，进一步给出了当q不是平衡函数时，形如F=fx+τ(yq+g布尔函数是Bent函数的充分必要条件。

Simulation results show that:1 The FWHM of the spectrum has an effect on the performance of a depolarizer. 2 The spectrum width of every longitudinal mode has no effect on the performance.

仿真计算表明：1消偏器的性能与光谱的半峰全宽有关；2每个纵模谱宽的变化不影响消偏性能。

The data were applied to simulate the neutron energy spectrum and angular distribution of Lanzhou University 3×10^12 s^(-1) intense neutron generator with 260 keV deuteron beam using MCNP. The interactions of neutron and the materials of neutron generator and laboratary wall were included in this MCNP simulation. The simulation results on the neutron energy spectrum and angular distribution of Lanzhou University 3×10^12 s^(-1) intense neutron generator with 260 keV deuteron beam were presented.

以分割法计算得到的能谱和角分布数据为基础，建立了D-T中子源Monte-Carlo模拟抽样模型，在考虑中子发生器各元件材料及实验大厅墙壁对快中子的慢化、散射和吸收的条件下，采用MCNP程序对兰州大学3×10^12s^(-1)强流中子发生器260 keV氘束流能量下的中子能谱和角分布进行了模拟，给出了模拟结果。

Furthermore, the interaction of L-C10HL and D-C10HL with cyclodextrin was also investigated by fluorescence excitation spectrum and circular dichroism spectrum.

利用荧光激发光谱和圆二色性谱研究了L-C10HL和D-C10HL与环糊精之间的相互作用。

Based on the table of matrix element of spectrum decomposition, the Helmhotz matrix can be decomposed by recursion of the direct solution. A numerical comparison has been made with the spectrum LU decomposition and direct solution.

通过与谱法分解和直解法在分解精度和分解速度两方面的比较表明，本文方法与谱法相比，在非均匀介质中亥姆霍兹算子矩阵分解时的精度提高10倍；在计算速度方面，混合方法比简化后的直解法快。

Damping identification ; Transfer function ; Spectrum analysis ; Discrete spectrum ; Signal processing

阻尼识别；传递函数；频谱分析；离散频谱；信号处理

In order to avoid spectrum error due to energy leakage, the thesis research on identification of parameters of two close frequency components in discrete spectrum analysis, and simulation result shows the validity of the method.

针对由于能量泄漏造成的频谱误差，深入研究了密集频谱的频域参数识别法，从理论上加以推导，并通过仿真证明了该方法的有效性，可以识别1个频率分辨率以内的两临近频率分量。

The continuous channel model is represented by the delay power spectrum and the discrete channel model by the envelope delay power spectrum and the arrival rate of the paths.

连续的频道模型被延迟力量光谱和不连续的频道表现模型被路径的信封延迟力量光谱和抵达率。

By means of the discrete frequency spectrum, the frequency spectrum leakage s of the conventional DFT and the DFT with a Hanning window are comparatively analyzed in this paper.

利用离散频谱详细对比分析了DFT的频谱泄漏和加汉宁窗DFT的频谱泄漏现象，讨论了用异步顺序采样值计算电量产生误差的原因，提出了利用异步顺序采样值精确计算电量的方法，实现了畸变电量的精确测量。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。