查询词典 radio-frequency spectrum

Radio spectrometer is important method and main instrument of radio astronomy research, through which we can research radio astronomy phenomenon in wide frequency spectrum and continuous time with high frequency resolution and high temporal resolution.

射电频谱仪是通过高的频率分辨率和高的时间分辨率，在广泛的频谱范围内和连续的时间演化上进行射电天文观测的仪器，它是射电天文研究的重要方法和主要工具。

A Reflectional radio receiver also called a reflex radio is a radio receiver design in which the same amplifier is used for both the high-frequency radio RF and low-frequency sound AF signals .

一个来复收音接收机是这样一种收音机，它的放大器同时用来对高频信号和低频信号进行放大。

By adopting modern optics information processing technology and changing frequency spectrum of optical signal, zero frequency spectrum was enabled to interfere with the first class frequency spectrum.

采用现代光学信息处理技术改变光信号的频谱，使零级频谱与一级频谱干涉，从而实现由位相到强度的调制，最终检测到透明材料的位相缺陷。

The results showed that the echolocation calls of the leaf-nosed bats were constant frequency-frequency modulation signals with 2-3 harmonics and the second one among these three harmonics was its dominant frequency. The constant frequency components of three harmonics (Mean±SD, n=18 ) were 33.3±0.2 kHz, 66.5±0.3 kHz, and 99.4±0.5 kHz, respectively. In examined FTCs of 72 IC neurons, their Q 10 -dB values ranged from 0.5 to 95.4 (9.2±14.6) and the neurons whose best frequency around the dominant frequency had sharp frequency tuning.

结果发现，大蹄蝠回声定位叫声为恒频-调频(constant frequency-frequency modulated，CF-FM)信号，一般含有2~3个谐波，第二谐波为其主频，CF成分频率(Mean±SD，n=18)依次为：(33.3±0.2)、(66.5±0.3)、(99.4±0.5)kHz；电生理实验共获得72个神经元的频率调谐曲线，Q10-dB值的范围是0.5~95.4(9.2±14.6， n=72)，最佳频率(best frequency，BF)在回声定位主频附近的神经元具有尖锐的频率调谐特性。

This result can best be viewed as a quantum black hole version of the third law of thermodynamics. As a result of this area spectrum, the spectrum of M is discrete, bounded below, and can be made positive. Prom the physical point of view, the semiboundedness and positivity of the spectrum are very satisfying results: The semi-boundedness of the spectrum implies that one cannot extract an infinite amount of energy from the system, whereas the positivity of the spectrum is in agreement with the well-known positive-energy theorems of general relativity.

同时根据EMDA黑洞动力学，存在与面积谱对应的大于零且有下界的质量离散谱，从物理上来看，质量谱的半有界性意味着不可能从系统吸取无限的能量，而正定性则与广义相对论中的正能定理一致，也就说稳态轴对称EMDA时空的ADM能量总是大于零。

In this thesis, we use the Min-Max criterion and Parks-McClellan algorithm to design this optimal approximation error of spectrum. Moreover, we give constraint of this optimal spectrum to get the positive spectrum. Then the positive spectrum can be factored by Spectrum Factorization Theorem and can be realized by FIR system.

我们利用最小化最大误差指标，及Parks-McClellan演算法，设计出具有最佳误差的频谱，并对此频谱做限制式上的处理，来得到正数列频谱，并将所得到之正数列频谱利用分解理论做分解，并以FIR系统实现之。

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。

Receiving, the radio waves from celestial observation equipment, which can be used to determine the strength of celestial radio, radio source location, size, the polarization of the radio emission and spectrum, etc..

接收、观测来自天体的射电波的设备，它可用来测定天体射电的强度，射电源的位置、大小，射电辐射的偏振和频谱等等。

Vertically put the KAS detector on the upper part of the transmitter cover, turn EAS detector power supply switch on, EAS detector displays radio frequency output center frequency is: 8.2±0.05MHz; Adjust R15 (counterclockwise decrease, clockwise increase) can change radio frequency output center frequency.

把 EAS 检测仪垂直放置于发射机壳上部，按动 EAS 检测仪电源开关， EAS 检测仪显示射频输出中心频率为：8.2±0.05MHz ；调节 R15（反时针减少、顺时针增大）可改变射频输出中心频率。

Based on the requisition of wireless system debugging, this paper develops a novel radio-frequency beaconing. Design method and system constitution of a novel beaconing based on PLL IC PE3336 are given, and the accomplish method of the system's hardware and software arc expounded. The test results show that the beaconing adopted in this method has a reliable and stable frequency conversion features. The more applications in the wireless system find that the users can set necessary frequency conveniently. Especial1, the friendly man-machine interface makes the operation is more flexible. It is as excellent performance-price-ratio beaconing, and as a signal source, it can be used in the research and the debug procession of variable radio-frequency components.

根据无线电数据链系统及部件的调试需要，研制开发了一种新型的以锁相环为核心、由单片机控制的射频信标机；文中给出了基于锁相环芯片PE3336的新型信标机的设计方法与系统组成，阐述了系统硬件及软件的具体实现为法；测试结果表明，利用该方法设计的信标机具有稳定、可靠的变频特性，且各项指标均达到了要求；进一步在某无线电系统中的应用发现，用户可方便地设置所需频点；特别是友好的人机界面，使用户操作更为灵活方便，是一种性能价格比优良的信标机；并可作为信源用于不同的射频部件研制与调试过程中。

The use of the web to spread fears that flicking the switch on the LHC could create a Black Hole that could swallow up the Earth particularly concerned him, he said.

他说，使用互联网散布恐慌说启动LHC会生成一个可能吞噬地球的黑洞的做法让他感到忧虑。

Not a single word have I written down.

我一个字也没有写下来。