低频

The time-domain response of the induced currents on a scattering object irradiated by a plane wave with a Gaussian pulse in time is expanded as an associate Hermite series in this paper. Using the isomorphism of the associate Hermite function and its Fourier transform, the frequency-domain information can be obtained similarly to the time-domain expansion. According to the corresponding relation between time-domain analysis and frequency-domain analysis, and using the early-time response and the low-frequency information of the induced currents, the non-known coefficients in the expansion series can be decided. The entire responses of the induced currents on the scattering object in both time and frequency domains can be obtained at one time by simultaneous extrapolation computation using both the early-time response and the low-frequency information of the induced currents.

摘要首先根据散射体在高斯脉冲平面波激励下感应电流的能量几乎全部集中在时间轴和频率轴上的有限范围内，该文将时域响应展开为系数待定的连带Hermite级数的叠加，并根据连带Hermite函数的傅里叶变换的自反性，得到与时域响应形式类似的频域响应；然后利用时域方法和频域方法分别计算散射体上感应电流的早时响应和低频信息；最后经过时域和频域联合外推计算，由早时响应和低频信息确定时域和频域响应的待定系数，从而获得了整个时域和频域的完全响应。

For reducing boundary distortion area, the elevations of grid DEM are viewed as a discrete sequence under a generalized coordinate, so that the boundary problem of two-dimensional discrete wavelet transform is turned into the boundary problem of one-dimensional discrete wavelet transform, which not only greatly reduces the boundary distortion area, improves the precision of reconstructed DEM data near the boundary, but also decreases the number of zeros adding on the boundary for wavelet transform, and boosts the compression ratio. On the basis of analyzing the distribution characteristics of coefficients in low and high frequency bands, a mixed entropy coding plan is applied, and a high efficient quantizator called"self-adaptive hard threshold"is established, which is helpful for improving the precision of the reconstructed DEM data and for enhancing compression ratio.

为了减小小波变换山区格网DEM数据压缩中边界失真区域，将山区格网DEM高程值视为广义坐标下的离散随机序列，把二维离散小波变换中的边界问题转换为一维离散小波变换中的边界问题，不仅大大减少了小波变换边界失真区域，提高了重构DEM数据边界点的精度，而且减少了边界补零个数，提高了压缩比；通过对山区格网DEM数据小波变换低频区和高频区变换系数分布特点的分析，采取了霍夫曼—游程混合熵编码方案，设计了高效、低失真的"自适应硬阈值"量化器，即对低频区变换系数不进行量化，直接进行霍夫曼编码；对高频区变换系数则先用"自适应硬阈值"方法量化处理，再进行游程编码。

Methods By using the theories of conservation of mass, of energy, Darcy's law and hydrokinetics, the mechanical model of oil layer fluid under the function of low frequency vibrated wave was studied. With the combination of indoor experiment and the numerical simulation, the effect of downhole low frequency vibration on oil viscosity, interfacial tension, capillary pressure, producing water cut and the rising velocity of it was studied quantitatively.

应用质量守恒定律、能量守恒定律、达西定律、流体动力学等基本原理研究了低频振动波作用下油层流体的数学模型，将室内实验和数值模拟技术相结合定量地研究了低频振动对原油私度、界面张力、毛管压力、产水率及产水率上升速度的影响。

In the case of FTIR,-- OH absorption peak at 930-970cm^-1 and 1480cm^-1 are weakened, and C-N absorption peak of imide is enhanced.

在红外吸收图谱中，930～970cm^-1处和1480cm^-1处的-OH吸收峰减弱，在1220cm^-1处的酰胺C—N吸收峰增强，1700cm^-1左右的〉C=O吸收峰略向低频偏移且低频子峰增大；在2240cm。

In Group P, epinephrine and norepinephrine increased in all patients during peritoneal insufflation and tumor resection.

group p 中所有病人在腹膜充气和肿瘤切除时肾上腺素和去甲肾上腺素水平均升高。16个病人同时伴有收缩压、心率、低频和 LF/HF 比值的升高。3个病人的低频和 LF/HF 比值降低。

The current signals were gathered in the tests, and processed by wavelet package transform. A characteristic vector was constructed by the energy of different frequency segment, which was calculated by using the coefficient of wavelet package transform of the current signals. The vector shows that the energy of low frequency segment is of the majority of the total energy, and becomes larger as the interelectrode gap decreasing.

在线采集真实电解加工过程中的电流信号，用对实测信号进行小波包分解和重构后的小波系数计算各频段的能量，构造一个由不同频段能量组成的特征向量，发现特征向量的低频分量占总能量的大部分，随着平衡间隙的减小，低频分量能量增大。

In the method the discrete cosine transform DCT is first applied to noisy facial images to remove its high frequency component noise, the removed noisy face images can be obtain through performing inverse discrete cosine transform. Then the two dimensional principal component analysis (2DPCA) is exploited to the removed noisy face images to obtain a set of eigenvectors that have larger correspondent eigenvalues, and the features of images with lower information dimensions are extracted to get fast recognition speed.

这方法首先对具杂讯脸部影像进行离散余弦转换去除高频杂讯，取得低频影像以降低高频杂讯干扰，然后再对低频影像以二维主分量分析(2DPCA)撷取前几个较高特徵值所对应的一组特徵向量，以降维与资讯集中达到快速辨识的目的。

The paper studies UFLS with several times accelerating shedding load function, analyzes dynamic frequency characteristic of power system during UFLS, derives the formula which is served as setting rate of frequency change for criterion of accelerating shedding load, and designs the logical diagram expressing UFLS operation.

研究了同时依据频率和频率变化率两个变量，在每个频率定值处设置加速减载功能的低频减载方案。文中详细分析了低频减载过程中频率的动态特性，推导了作为加速减载判据的频率变化率整定值的计算公式。

The paper studies UFLS with severaltimes accelerating shedding load function, analyzes dynamic frequencycharacteristic of power system during UFLS, derivesthe formula which is served as setting rate of frequency change for criterionof accelerating shedding load, and designs the logical diagram expressing UFLSoperation.

研究了同时依据频率和频率变化率两个变量，在每个频率定值处设置加速减载功能的低频减载方案。文中详细分析了低频减载过程中频率的动态特性，推导了作为加速减载判据的频率变化率整定值的计算公式。

This is a practical design approach for the filter of the low-frequency oscillations.

同时，对带有低频振荡滤波器的系统进行仿真分析，讨论影响低频振荡的因素。

As she looked at Warrington's manly face, and dark, melancholy eyes, she had settled in her mind that he must have been the victim of an unhappy attachment.

每逢看到沃林顿那刚毅的脸，那乌黑、忧郁的眼睛，她便会相信，他一定作过不幸的爱情的受害者。

Maybe they'll disappear into a pothole.

也许他们将在壶穴里消失