查询词典 frequency

At first, the last low-frequency image after wavelet decomposition can be an initial approximation of the next low-frequency image. It is tested and verified that the last low-frequency image can diffuse and converge to the next low-frequency image. On the other hand, the next low-frequency image can also diffuse and converge to the last low-frequency image. Above process just presents the gradual variation of wavelet decomposition and reconstruction.

首先，用小波分解后下层的低频图像作为对上层低频图像的一个初始近似，验证了由上层低频图像经方向扩散方程可逐渐扩散收敛到下层的低频图像；反过来，由下层低频图像经方向扩散方程亦可逐渐扩散恢复到上层低频图像，这正体现了小波分解与重构的渐变过程。

No additional data for frequency tracking are need, but higher estimation accuracy and low computational complexity can be obtained. Finally, a kind of optimizing joint algorithm for symbol timing, frequency synchronization and channel estimation is proposed. The false alarm probability and miss detect probability of the symbol timing are derived. We proved that the time－frequency offset domain random sequence sliding in the frequency offset direction is orthogonal with the original random sequence, and proposed a new integer frequency offset estimation algorithm. The coarse estimation methods for fractional frequency offset both in AWGN and multipath channels are proposed too.

最后，提出了一种优化的符号同步、频偏估计和信道估计的联合算法，推导了符号同步方法的虚警概率和漏检概率，给出了随机序列在时间－频率偏移域沿频率偏移方向滑动后与原序列近似正交的证明，提出了一种新的在时间－频率偏移域沿频率偏移方向进行滑动相关估计整数频偏的方法，提出了在AWGN信道和多径信道下进行小数频偏粗估计的方法，给出了小数频偏细估计的ML估计结果和利用频域PN序列取值特性的简洁的信道估计结果。

Zhang Qi pointed out that the RFID application has the different frequency band, low frequency, high frequency and ultra-high frequency, at present will speak the high frequency application was still the market mainstream, in the short-term will not change, in 2008 the high frequency application occupied 70% market share, from now on will keep pace with the times unceasingly carries on the development.

张琪指出，RFID应用有不同频段，低频、高频和超高频，目前来讲高频应用仍是市场主流，短期内不会改变，2008年高频应用占70%的市场份额，今后会不断与时俱进地进行发展。

Similarly, if the strong shear, which could suppress all the scattering in the quiescent two phase region, stopped, the follow-up phase separation also displayed characteristics of anisotropism and relaxation, In this dissertation, the transposed"butterfly'and"streakpattern were observed for the first time within the shear-history-influenced phase separation, which is found closely relevant to the anisotropical relaxation behavior of macromolecules. 5. The phase separation kinetics of PS/PVME under oscillatory shear was further studied on the base of that done under simple shear. It is found that, under specific temperature and strain amplitude, the occurrence of phase separation is strongly contingent on oscillatory frequency and only intermediate frequency could effectively induce phase separation; If all considered oscillatory shear could stimulate phase separation, a fixed frequency can maintain specific most probable phase size and higher frequency yields smaller phase, which makes a higher elasticity but weaker stress relaxation; Furthermore, higher frequency can produces stronger compulsory oscillation on the MPPS but won't change the mean of the MPPS. Under given frequency and strain amplitude, the phase separation kinetics dramatically depends on the phase angle of oscillation and the phase separation corresponding to different phase angle follows different dynamical process.

在简单剪切场下相分离动力学研究的基础上进一步对振动剪切场下PS／PVME的相分离动力力学进行了尝试性的研究，发现：在一定温度和振幅条件下，相分离的发生强烈的依赖于振动频率，只有中等频率的振动剪切才能有效地促进相分离的发生；在都能使相分离发生的前提下，一定频率的剪切能够使体系维持一定的最可几相尺寸，较高频率的剪切导致体系形成的相区尺寸较小，因而体系的弹性效应较强而应力松弛效应较弱；同时，更高频率的剪切对最可几相尺寸的强迫振动效应越强，但不会使最可几相尺寸的平均值发生改变；在一定的振幅和频率条件下，相分离的动力学过程会强烈地依赖于相位角，不同相位角对应的相分离遵循不同的动力学过程但机理一样。

As a differential detection is used between the intercarrier, the proposed algorithm overcome the high sensitivity to timing error of conventional algorithm and is robust to multi-path. The effect of sample frequency offset can't be ignored in a continuous OFDM system of a large number of subcarriers. The estimation precision of the conventional algorithm is low and the realization is complex. A joint estimation of sample frequency offset and fine frequency offset based on difference operation is proposed. As averaging use a large number of samples in a maximum likelihood algorithm, the estimation precision is very high. The use of difference operation cancel the effect of carrier frequency offset, and the proposed sampling frequency estimation algorithm is robust to carrier frequency offset.

最后，本文对连续系统中的采样频率和载波频率精同步技术进行较为深入的研究，由于子载波数目大的连续OFDM传输系统中，采样频率偏差不可忽视，以往的采样频率估计方法精度低、实现复杂，因此本文提出了一种基于差分处理的采样频率偏差和精载波频率偏差联合估计算法，利用了最大似然算法进行采样频率偏差的估计，由于采用了差分处理方法，消除了载波频率偏差对采样频率偏差估计的影响，采用的最大似然算法对大量样点进行平均化处理，所以，相对以往算法，提出的联合算法估计精度高，而且采样频率偏差估计对载波频率偏差具有鲁棒性。

The wavelet time-frequency properties of the uncracked rotor and the cracked rotor were discussed by the continuous wavelet time-frequency analysis algorithm. A new algorithm using the wavelet time-frequency analysis algorithm to detect the crack was proposed. The influence of the sampling frequency on the wavelet time-frequency analysis algorithm was analyzed through the numerical simulation research; the valid sampling frequency was presented.

利用连续小波时频分析方法，讨论了裂纹转子与无裂纹转子的小波时频特性，提出了利用小波时频分析方法识别裂纹的新方法；数值仿真研究了采样频率对小波时频分析方法的准确性和有效性的影响，并给出了建议性的采样频率。

When microgrid is operated in islanded mode, VSGs can be divided into non-frequency regulation units and frequency regulation units, the former can generate power and participates in primary frequency control according to dispatching to mitigate system frequency deviation due to disturbances; the latter can offer referential voltage of microgrid and use secondary frequency regulation to implement no-error frequency control.

微电网孤岛运行时，将虚拟同步发电机分为非调频发电单元和调频发电单元，前者既能按照功率调度指令发电，又能参与一次调频，缓解扰动情况下系统频率的波动，后者提供微电网参考电压，并利用二次调频实现频率的无差控制。

The number of the frequency division of the method and the circuit structure thereof do not influence the highest frequency of the working circuit. The normal work of the frequency division circuit can be at a comparatively high clock frequency, and the clock frequency division can be realized in the manner of cascade connection of the frequency division circuit so that the scale of the circuit realization can be properly reduced.

本发明所述方法及其电路结构的分频数大小不影响电路工作的最高频率，可以使分频电路正常的工作在相对很高的时钟频率，而且可以通过分频电路级联的方式实现时钟分频，从而可以适当减小电路实现的规模。

The Company is responsible for people at high-frequency machine Through more than ten years of research and design, has been developed to create a series of applicable to all types of plastic / PVC, rubber, leather, Blister packaging high-frequency welding / fusing machine; trademark high-frequency equipment machinery, high-frequency metal weld / heat treatment machine ; high-frequency pipe machine; high-frequency synthetic resin preheating aircraft and other special plastics processing machinery.

本公司负责人在高周波机器上通过十余年的研究和设计，现已开发，制造出一系列适用于各类塑胶/PVC，橡胶，皮革，吸塑包装等高周波熔接/熔断机；高周波商标专用设备机械，高周波金属熔接/热处理机；高周波制管机；高周波合成树脂预热机以及其它特殊塑胶加工机械等。

Simulation results show that, for the fixed sampling frequency, the error rises with the frequency increasing of periodic signal, and decreases with the attenuation time constant increasing of non-periodic signal. The sampling frequency determines the upper limit of appropriate frequency band directly. The research provides the basis for the selection of cutoff frequency in filter design.

仿真结果表明，在采样频率确定时，对于周期信号，计算误差随频率的增加而增大，而对于非周期信号，计算误差随衰减时间常数的增大而减小，采样频率大小决定了插值法用于分布参数模型的适用频带上限，该研究为滤波器设计中截止频率的选择提供了依据。

The statistical analysis of this large set of mutations has led us to propose a diagnostic strategy that should help with the molecular work-up of optic neuropathies.

这一大系列基因突变的统计学分析引导我们提出一个诊断策略，可以帮助我们对视神经病变进行分子学的诊断检查。

The results show that the pipe grouting changes the mechanical parameters of surrounding rocks to achieve the security of engineering objectives by reinforcing surrounding rocks and bolcking the water.

研究表明：小导管注浆一方面改变了围岩的力学参数，另一方面利用浆液的固结特性可以实现堵水和加固围岩的工程目标，使隧道在开挖过程中的安全得到保障。