频率

Instantaneous frequency is function of time that gives sharp identification of imbedded structures in signal.

由于瞬时频率是时间的函数，因此可以获得信号任意时刻的频率分布，利用瞬时频率的局部化特征可以有效地揭示信号的内在结构。

For this reason, an optimal automatic timing control algorithm is proposed, that can restrain the switching frequency in a certain range to achieve the purpose of high efficiency and energy conservation. Taking such factors as inductive reactance at AC side, switching frequency, harmonic distortion rate and switching loss as well as the interaction among them into consideration, the formulas for inductive reactance and switching frequency are given; then by use of digital signal processor TMS320F2812, a prototype based on the proposed algorithm is implemented, and using this prototype the effectiveness and practicality of the proposed method are verified by experimental research and simulation.

文章提出了自动定时控制的优化算法，将开关频率限定在一定范围内，以达到高效节能的目的；综合考虑交流侧感抗、开关频率、谐波畸变率和开关损耗等指标，提出了主电路电感参数和开关频率的选择公式，并采用TMS320F2812数字信号处理器构造了试验样机，进行仿真和试验研究，其结果证明了该方法的有效性和实用性。

A series of theoretical and experimental studies on the microstrip patch antennas with dielectric superstrates is carried out systematically. Firstly, a comprehensive survey of the microstrip antenna technology and its theories are presented. Then, two analysis techniques, named as the spectral domain Green's function method and the spectral domain integral equation method are developed. The SDGF method is a simplified analysis technique, which takes advantage of the spectral domain immittance approach to find the dyadic Green's function for the stratified media, and obtains the complete closed-form formulas for radiation patterns, directivity, efficiency, gain etc. Some interesting calculated results are presented. The SDIE method is capable of determining resonant frequency, radiation characteristics, input impedance etc, for the covered microstrip patch antennas. Comparing with other full-wave analyses it reduced computation and mathematical labour remarkably. The singularities near the pole location of the surface-wave modes and the difficulty of the integral computation over infinite range of oscillating integrands are dealt with actively and documented well. Results predicted by the SDIE method agree extremely well with our experimental results for resonant frequencies of various superstrates. The superstrate effects on impedance and radiation characteristics also have been investigated experimentally so that the gap due to lack of measured data and computed results for multi-layered superstrate has been filled to some degrees and two useful observations have been achieved for weakening the resonant frequency shift and optimizing the microstrip antenna gain. As a meaningful application, the design and analysis of a 4×4 patch array are introduced.

实用微带天线普遍加介质覆盖层来防护热，物理损伤和环境影响，也可能在飞行或严酷气候条件下自然形成覆盖层本论文对带介质覆盖层的微带贴片天线系统地作了一系列理论和实验研究首先，对微带天线技术和理论作了全面的综述然后，发展了两种分析方法，称为谱域格林函数法和谱域积分方程法SDGF法是一种简化的分析技术，它利用谱域导抗法来求得分层媒质的并矢格林函数，并得出方向图、方向性系数、增益等参数的完整的闭式公式，给出了一些令人感兴趣的计算结果SDIE法能确定介质覆盖微带天线的谐振频率、辐射特性和输入阻抗等与其它全波分析方法相比，它明显减小了计算量和数学工作量已有效地处理了表面波模极点附近的奇异性和对振荡的被积函数的无限区间积分计算的困难对于不同覆盖层情况下的谐振频率，由SDIE法所预示的结果与我们的实验结果吻合得很好对于覆盖层对阻抗和辐射特性的影响也已作了实验研究这在某种程度上填补了缺少实验数据和计算结果之间的间隙，并得出了缓解谐振频率偏移和优化天线增益的两点有用的结论作为有意义的应用，介绍了一个4×4元矩形贴片天线阵的设计和分析。

Occurrence of the triangular shape decreased with the age. The frequency of irregular labrum and absence labrum increased with the age. The frequency of labrum high signal intensity increased with the age.

随年龄的增长，三角形髋臼唇出现频率逐渐降低，不规则形及缺如型髋臼唇出现频率逐渐增高，髋臼唇出现异常信号的频率逐渐增高。

This makes it possible to reduce vibration and noise on a certain frequency in application. By finite element method, frequency response and radiating noise of block's lateral surface under the impact are analyzed.

根据不同频率灵敏度最大值所对应的位置不同这一特点，可进行局部参数修改，而对其它频率响应的影响很小，使得实际中针对某一频率的减振降噪成为可能。

The different width and length of Hilbert curve geometries were investigated by finite element method. The computation results show that the DGS rejects the signal at two frequencies 2.43 GHz and 7.11 GHz from 0~9 GHz with more than -15 dB suppression. Q factors of the Hilbert curve DGS is bigger than that of conventional DGS.

通过有限元法对不同Hilbert曲线宽度和长度的DGS结构微带线进行计算，计算结果表明，该结构在0~9 GHz频段内表现出2.43 GHz和7.11 GHz这2个谐振频率，对应频率的通带反射损耗低于-15 dB，并且阻带特性在谐振频率处比传统DGS微带线有更高的 Q 值。

The maxima of low-temperature internal friction peaks plot a symmetrical peak-like curve at logarithmic frequency spectrum and the peak-like curve shifts toward high frequencies with the increase of heating rate, indicating that phase transition relaxation time decreases; the maxima of high-temperature internal friction peaks exhibit a linear relation to the reciprocal frequencies, and as the heating rate increases its slope rises, which implies that the heating rate drives the normal movement of phase interface further in low-frequency measurements.

低温内耗峰峰值与对数频率呈现峰形函数关系，随升温速率的增加，频率峰向高频方向移动，相变弛豫时间减小；高温内耗峰峰值与倒数频率成直线关系，随升温速率的增加，直线斜率变大，表明低频测量时升温速率对相界面法向运动的驱动作用更强。

Where the irrigating frequency was 1 or more than 1 every four days, it did not remarkably affect the ET of potato; but where the irrigating frequency was 1 every six days or 1 every eight days, the ET of potato measured by a lysimeter was obviously higher than what it was in the treatment with a higher irrigating frequency.

大于或等于1次/4 d滴灌灌水频率对马铃薯的腾发量影响不明显；但当滴灌灌水频率为1次/6 d或1次/8 d时，由蒸渗仪测得的马铃薯腾发量明显低于更高频率处理。

The equations of dynamics for the balance are established by Kane's method, from which derives the characteristic equation of natural frequency by means of linearization of dynamic equations, and the six natural frequencies being developed according to the theory of vibration. The law of the six natural frequencies varying with mass of the upper platform and the stiffness of the elastic element are presented,and the Finite Element Method is employed to testify the validity of theoretical results.

基于 Kane 方法研究天平的动力学及模态，通过线性化动力学方程建立天平的固有频率方程，依据振动理论推导出并联天平的六阶固有频率及其对应的振型，同时研究了天平的六阶固有频率随敏感单元刚度系数及上平台质量的变化规律，并用有限元法验证理论计算结果的正确性。

By detecting the oscillation circuit natural frequency to determine the level of water.The frequencymeter use the Microprocessor internal counter to counting the film resonant frequency of the water level sensor pulse,then Microprocessor regular function to achieve frequency testing, final adoption of LED display circuit dynamic numerical show.

该频率计直接利用单片机内部的计数器对薄膜谐振式水位传感器的频率脉冲信号进行计数，然后利用单片机的定时功能实现对频率的检测，最后通过LED动态显示电路显示数值。

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。