查询词典 frequency analysis

The instantaneous frequency of a real signal is one of the most important concepts in time-frequency analysis.

瞬时频率是时频分析中的核心概念之一，它的定义也一直是信号处理领域的理论难题。

Time domain signal is transformed to the frequency domain signal by FFT. Dispersion curve is obtained from phase angle that is calculated by the frequency spectrum analysis. A compound dispersion curve is obtained from the dispersion curves intervale, and the representative dispersion curve is used to evaluate dimensions and quality of soil grouting body.

由FLAC所得不同点位的速度历时透过快速傅立叶转换后，得到频率域讯号，再经过频谱分析计算其相位角，得到其频散曲线，由不同间距的频散曲线集合成复合频散曲线，再绘制成一"代表性"频散曲线，以评估灌浆体品质及范围。

It is shown by frequency domain analysis and simulations that the transfigured controller can improve the dynamic behavior of the system if the frequency spectrum of the inverse of the non-transfigured controller has the low-pass and high-obstructive characteristics.

从理论上分析了如果用常规的回路成形算法设计出的控制器的逆的频谱具有低通和高阻特性，常规的回路成形控制器变形后能够改善系统的动态性能，并将之应用于船舶自动舵的设计中，获得了满意的控制结果。

This paper aims at the analysis and computation of double machine power systems frequency dynamics and provides the characteristics of double machine power systems frequency dynamics .

本文首先对双机系统频率动态过程进行了理论分析，给出了双机系统频率动态过程的特点。

The main work and innovation1 In general , a image compression method has different effect to different image . Some are fit for image which has much high frequency . Some are fit for image which has much low frequency .This paper analysis the applicability of fractal algorithm . In this dissertation , an improved algorithum is given . The basic algorithum without eight change and the joint use of quantitative coding , The compression ratio and PSNR can be adjusted , and it can get more quickly speed of coding .2 To a group of exact fractal code , the decoding image can be any resolution .With this characteristic ,choose the proper domain block and range block,this paper get an algorithum which can get higher decoding PSNR and speed than the basic fractal algorithum.3 Give a new method to calculate the scale factor . The calculation of basic algorithum is complex and enormous . The factor of scale is an important variable of the basic algorithm. Now there are two methods to calculate the factor of scale .A new method was given to calculate the factor of scale. The calculation load and complexity are reduced by the new method. Compared with the basic algorithm , the method can reduce coding time.4 The basic fractal algorithum is based on the Collage theorem and contraction mapping theorem . A mathematic model based on basic fractal algorithum is given .

本文的主要工作及创新点主要包括以下几点：1一般情况下，一种图像压缩的方法对不同特点的图像，压缩效果会有所不同，本文利用分形压缩编码对不同特点的图像进行编码，分析了分形编码对不同图像的编码适用性，利用去掉8种变换的分形编码算法与简单的均匀量化编码方案相结合，得到了一种可以调节压缩比与解码质量的分形编码方案，该提高编码速度6倍以上。2分形编码的特点之一是分形解码的分辨率无关性，即对于一组分形编码可以将其解码到任意分辨率下，本文利用分形编码的这一特点，结合不同的量化编码方案，选择合适的定义域块与值域块及适当的编解码分辨率，得到了一种提高解码质量，编码速度提高12倍以上的加速算法。3比例因子是基本分形算法中的一个重要变量，目前有两种计算比例因子的方法，文中给出了一种新的求比例因子的方法，该方法简化了求比例因子的计算，从整体上减小了基本分形算法的计算量，简化了算法4分形压缩的数学基础是不动点定理与拼贴定理，本文根据基本的自动分形编码方法，建立数学模型对其进行推导，得到了用普通数学的极限理论解释分形编码的数学表达式，从而对由基本分形编码得到的解码图像中的像素点的值给出了确定的表达式。

Statistic analysis on IR image characteristics shows that IR target has relatively more and larger regions which are of same quality, mainly expressed by smooth images and by that the energy distribution is concentrated on low frequency band in L〓 linear normed space, while large quantity of background regions show as texture images and their energy in L〓 space is concentrated on high frequency band. Based on this difference, the IR target segmentation method on the basis wavelet transformation is proposed.

通过对红外图像特征的统计分析证明，红外目标含有较多较大的同质区，主要表现为平滑图像，在L〓线性赋范空间的能量分布集中在低频，而大量的背景区域表现为纹理图像，在L〓空间中能量集中在高频部分，根据这一差别，提出了一种基于小波变换的红外目标分割方法。

Based on the analysis of the Doppler effect of the mobile channel, the performance of two MIMO-OFDM systems (STTC-OFDM and SFBC-OFDM) in the fast-moving environment is studied. Then, the algorithm for channel estimation based on the training sequence is extended into the fast-moving environment by introducing the space-frequency coding, the method of the equal-interval pectinate pilot-inserting, and the complete Maximum-Likelihood space-frequency decoding.

针对快速移动环境中存在的多普勒效应，研究了两种多输入多输出正交频分复用系统在快衰落信道中的误码性能，采用空频编码梳状等间隔导频插入方式，以及完全最大似然空频分组码解码算法，使用导频与接收信号进行信道参数估计，将一般多输入多输出正交频分复用系统中的基于训练序列的最小均方误差信道估计算法推广到了快衰落信道环境中。

Based on the concept of frequency analysis in periodic orbit theory and matrix principle, a method of changing fundamental frequency of chaotic systems is put forward.

文中基于混沌吸引子周期轨道理论的频域分析概念和矩阵分析原理提出了一种混沌系统基波频率变换方法。

In this paper, first, a method of fundamental frequency transformation for chaotic systems is proposed based on the concept of frequency domain analysis in the periodic orbit theory of chaotic attractors and on the matrix principle.

文中基于混沌吸引子周期轨道理论的频域分析概念和矩阵分析原理，提出了一种混沌系统基波频率变换方法。

In this topic, the dynamic analysis methods for piezoelectric vibrator are studied systematically based on the theoretical model, FEM numerical experimentation and FEM governing equation for given compound-mode vibrator, and some valuable conclusions are obtained. The main work accomplished is summarized as follows: 1.Elaborate the main modeling methods for piezoelectric vibrator and the significance and necessity to study the dynamic characteristics of piezoelectric vibrator which emphasize the urgency of this paper. 2.Take the bending deformation induced by piezoelectric ceramic as example, the energy transfer mechanism of electric energy to mechanical energy are analyzed; the motion and force transfer mechanism are analyzed for the longitudinal-bending vibrator. 3.Based on mode assumption and Hamilton principle, the coupling model of piezoelectric vibrator of linear USM is built; moreover, the equivalent circuit model is obtained and a coupling equation represents the relation between electric parameters and mechanical parameters is derived which provides foundation to match the vibrator and driving circuit. 4.Combine the constitutive equation of piezoelectric ceramic with elastic-dynamical equation, geometric equation in force field and the Maxwell equation in electric field and the corresponding boundary condition equation, the FEM control equation for piezoelectric vibrator of USM to solve dynamic electro-mechanical coupling field is established by employing the principle of virtual displacement. The equation lays the foundation to study the non-linear constitutive equation of piezoelectric ceramic driven by high-power. 5.Define the dynamic indexes of characteristic of vibrator and carry out variable parameters simulation by calculating the model parameters and the electric characteristics of vibrator are simulated according to the equivalent circuit model. By numerical experimentation, the working mode of vibration of vibrator and the shock excitation results of the working frequency band which provides the mode frequency to realize bimodal are analyzed. Detailed calculation of the electro-mechanical coupling field parameters is made by programming the FEM control equation.

本课题从理论模型、有限元数值试验、有限元控制模型等方面以复合振动模式振子为例对超声电机压电振子的动力学特性及其分析方法进行了全面系统地研究，得出了许多有价值的结论，主要概括如下： 1、阐述了目前针对超声电机压电振子的主要建模方法，对压电振子动态特性的研究意义和必要性进行了论述，突出了本文研究内容的迫切性； 2、以压电陶瓷诱发弹性体发生弯曲变形为例，分析了压电陶瓷通过诱发应变来实现机电能量转换的机理；对基于纵弯模式的压电振子的运动及动力传递机理进行了分析； 3、基于模态假定，利用分析动力学的Hamilton原理，建立了面向直线超声电机压电振子的机电耦合动力学模型，并据此建立了压电振子的等效电路模型，导出了电参量与动力学特性参量的耦合方程，为压电振子与驱动电路的匹配提供了依据； 4、从压电陶瓷的本构方程出发，综合力场的弹性动力学方程、几何方程、电场的麦克斯韦方程以及相应的边界条件方程，采用虚位移原理，建立了压电振子动态问题机电耦合场求解的有限元控制方程，为研究其大功率驱动下的非线性本构模型奠定了基础； 5、界定压电振子的动力学特性指标，对压电振子的机电耦合动力学模型参数进行计算及变参数仿真；依据等效电路模型，对压电振子的电学特性进行了仿真分析；通过有限元数值实验，对压电振子工作模态附近的模态振型及工作频率附近的频段进行了激振效果分析，找出了实现模态简并的激振频率；利用有限元控制方程，通过编程计算，对压电振子的力电耦合场参数进行了详细计算，得出了一些有价值的结论。

He got into race cars, while my father liked go-karts more, so I didn't really pay attention to what Diego was doing, as I was just racing karts.

叔叔开的是跑车，而我父亲更喜欢越野卡丁车，所以我并不太关注Diego在做什么，我仅仅在跑我的卡丁车而已。

She is at present gone to look for the best nectar and ambrosia to regale me this evening.

她今晚为款待我，现在又去准备美酒佳肴去了。