低频

First, the proposed scheme uses contourlet transform to extract multidirectional and multiscale texture information, and then obtains the feature points invariant to the affine transformation from the low and middle directional subbands by Harris-Affine detector. Second, the feature regions are adaptively computed by the feature scale of the local structure and normalized by U transform. The watermarking is embedded adaptively in those characteristic regions which are normalized. Finally, by vector quantization, several copies of the watermark are embedded into the no overlapped local feature regions in different directional subbands.

首先，用Contourlet变换提取出多尺度、多方向的纹理信息；再用Harris-Affine检测算子从变换域的中、低频方向子带中提取出仿射不变特征点，结合自适应局部结构的特征尺度确定特征区域，并用U变换对其归一化处理，水印就自适应地嵌入到归一化后的区域中；水印嵌入采纳矢量量化的策略，将水印信息重复嵌入到不同方向子带、多个不相交的局部仿射不变特征区域。

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。

A low frequency oscillation on-line monitoring and oscillation characteristics off-line analysis function module of power system based on wide area measurement systems was designed and implemented.

介绍了基于广域测量系统的电力系统低频振荡在线监测及振荡特性离线分析功能模块的设计及实现方法。

The simulation results show that it is a powerful tool for oscillation research.

仿真分析验证了该方法在低频振荡问题分析中的优势，从而为电力系统稳定分析提供了有力的工具。

Low frequency oscillation is an important problem which always affects the security and stabilization of power system.

低频振荡问题一直是影响电力系统安全稳定运行的重要问题。

The results in this thesis provide a new method to solve problems of interaction effects and low frequency oscillation in power system.

这也为研究电力系统中各个控制器的交互作用和互联电网的低频振荡抑制问题提供了新的解决方案。

For the first time, proposes a direct method to calculate the power system oscillatory stability margin.

首次提出了一种计算与低频振荡相对应的电力系统小干扰稳定极限的直接算法。

While the diameter of the semicircle at lower frequencies decreases with the increase of overpotential, this corresponds to the charge transfer process of oxygen reduction.

纳米碳管氧气扩散电极的Nyquist图在高频部分呈近似45°的直线，而在低频部分形成一个压扁的圆弧。

Using 75 varied low frequency noise samples with adjusted-loudness as sound stimuli, we investigate sound quality for low frequency noise with paired comparison method.

以等响处理后的 75 个稳态低频噪声样本为例，采用成对比较法，设计并完成了有 24 位评价者参与的大规模实验室主观评价实验。

Founded in 1966, Comdel, headquartered in Gloucester, Massachusetts, designs and manufactures RF and DC power supplies and process instruments for the semiconductor, flat panel, and industrial heating industries.

成立于1966年的Comdel电源公司位于美国马塞诸塞州的波士顿海滨，是一家专业致力于生产直流、低频、中频、高频、甚高频全频谱（DC- Khz-80MHz）精密电源的高科技公司。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。