频谱密度

The experimental results show: the flattop phenomenon on the diode voltage pulse was very apparent for using the carbon fiber cathode, that is to say, the pulse duration of the diode voltage was widened; moreover, under the condition of the same power of microwave, the pulse duration of the out-put microwave was prolonged by about 30%; the peak power of the microwave was enhanced by 3dB.

通过在装置上做的两种阴极的对比实验，结果显示：碳纤维阴极的使用，改善了电子束质量，使辐射微波的脉宽增加了30%以上，辐射主瓣方向上的功率密度提高了3dB以上，频谱分布较纯净，实现了微波的高效输出。

It shows the phase image filtered by vector filtering method which can decrease noise is still clean, the distribution of power spectral density has no change, the spectral information loss after pretreatment though vector filtering was smaller than second mean filtering.

结果表明，相比二次均值滤波法，向量滤波法在降噪的同时，相位图依然清晰，它的功率谱密度分布没有明显变化，预处理后频谱信息的丢失远小于二次均值滤波。

The content involves Digital Filter, Auto Correlation, Cross Correlation, mean and standard deviation, probability density and probability distribution statistic, as well as Auto Power Spectrum based on Fast Flourier Transfer, Correct Power Spectrum, Cestrum and Frequency Response. The Short-time Flourier Transfer and Wavelet Transfer are included in the analysis program.

具体内容包括：数字滤波、时域加窗、自相关计算与互相关处理、均值和方差计算、概率密度和概率分布统计，快速傅立叶变换基础上的自功率谱、互功率谱、频率响应函数、相关函数、倒频谱分析；基于短时傅立叶分析的联合时频分析、小波变换等。

In the paper,Power Spectrum Density of Orthogonal Unified Binary Shift Keying is figured out.

推导了统一的正交二元偏移键控信号的功率谱密度表达式，去除了高次谐波，获得了基本波形的优化结果，提高了频谱效率。

The paper determines compaction degree of subgrade making use of pumped sand, cutting ring ,nuclear density instrument and drop hammer frequent mensuration methods.

采用灌砂法、环刀法、核子密度仪法、落锤频谱式快速测定仪法4种方法对检测路基压实度的测试结果进行了比较分析；并以灌砂法作为现场测定压实度的标准方法，将其他方法与灌砂法进行回归标定，得出了相关关系，进一步证实了采用灌砂法作为路基压实度检测的标准方法是值得推广的。

The results indicate that the electron loss timescales due to artificial injection of ELF/VLF waves in the inner and the outer radiation belts depend largely on the value of the cold-plasma parameter α*(∝ B 2/ N 0, where B is the ambient magnetic field and N 0 the electron number density), the properties of wave frequency spectrum, the wave power and the electron energy in resonance with the waves.

数值计算结果表明，在内、外辐射带由于ELF/VLF波的人工注入而造成的高能电子损失时间尺度很大程度上取决于冷等离子体参量α*(∝ B 2/ N 0，这里 B 是背景磁场， N 0是电子数密度)、电波频谱特性和功率，以及与波发生回旋共振的电子能量。

It is shown that the modified model can predict successfully the characteristics of cavitation and the detailed process of the cavitation shedding. Values of n in the modified coefficient are found to have a strong influence on the cavity length, the vapor volume, the lift and drag force, but no significant effect on the frequency distribution of the dynamics around the foil is observed.

通过与实验结果的对比表明，修正后的模型可以更准确地捕捉云状空化区域的空穴形态和空泡脱落的非定常细节；密度函数中指数n的选取对计算所得的空穴长度和升阻力均有影响，然而对流场动力特性的主要频谱分布影响不明显。

At the same time, for ultraviolet, visible and near infrared range, the thickness, packing fraction and complex refractive indexes of the PZT thin films have been deduced from a transmission spectrum of the films by Envelope method.

同时，根据PZT铁电薄膜紫外、可见和近红外光区的透射光谱，采用&包络法&计算出了PZT薄膜的厚度、填充密度以及紫外、可见和近红外光区的复折射率及其射散频谱。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。