正弦

This paper utilizes FFT after undersampling to analyze the relationship between the estimation of sinusoidal parameters and corresponding actual values on the basis of bandpass sampling theorem. In addition, the errors of parameter estimation using phase difference are deduced strictly.

摘要该文从带通采样定理出发，分析了欠采样后利用FFT估得的正弦信号参数与真实值之间的关系，并对欠采样下基于相位差分法的参数估计的误差进行了严格的推导。

Based on varying process of generator terminal parameters after excitation fault, shortages of excitation protective principle of static stability boundary and asynchronous impedance boundary are analyzed. It proposed that excitation fault research relates to large-disturbance stability. Because dynamic power-angle character of generator after excitation fault is non-sinusoidal, there are differences between dynamic power-angle character and static state power-angle character. So it isn't ideal to protective operation result based on small-disturbance stability and static stability boundary criterion. At the same time, it proposed that asynchronous boundary impedance criterion is a constant reactive power circle moving adown j Xd′. It can ensure complete loss-of-excitation generator measuring impedance enter into the circle, but can't ensure the other condition measuring impedance including impossible losing synchronism enter. So loss-of-excitation protection would be maloperation when system voltage drops short and recovers or generator rejects load.③Based on stability principle, it puts forward setting conditions and calculation method of generator loss-of-excitation protection by direct measuring power-angle.

以励磁故障后发电机端的相关参数的变化为基础，通过对以静稳定边界和异步阻抗边界作判据的两类三种现行励磁保护在原理上存在的缺陷分析，发现：励磁故障是一个大干扰稳定性问题，励磁故障后的发电机的动态功角特性与静态功角特性有很大的差异，已远非正弦曲线，因此基于小干扰稳定性原理、以静稳定边界作判据的保护必然动作不理想；异步边界阻抗判据是一个下移j Xd′的等无功阻抗圆，它可以保证完全失磁后的发电机测量阻抗能进入该阻抗圆，但不能保证完全失磁之外的其它状态不会进入该阻抗圆，因此在系统电压短时下降或发电机突然甩负荷等情况下可能启动该保护使之误动。

Through the test of sine wave sweep, the character of response of aeolian sand due to motivation is gained.

利用正弦波扫频试验，得到风积沙对激励的响应特性。

1The axial evolution law on the structure and the aerodynamic characteristics of the asymmetric flows around slender bodies of revolution at incidences is summarized:whether the flow asymmetry is powerless or powerful,the flow always appears in the structure that lee-side vortices rise,and shed vortices form,and new lee-side vortices come into being alternately on opposite sides of a slender body of revolution axially from nose apex downstream to afterbody,and always induces the sectional side force of waving quasi-sinusoidally downstream axially.

1总结出细长旋成体有攻角非对称绕流流场结构和气动力特性的轴向演化规律：无论非对称性强弱，沿轴向从头部尖顶往后体，非对称绕流总是呈现为左、右两侧背涡交替从物面向上飘起、形成脱落涡、再衍生出新生背涡的流场结构，并诱导出沿轴向呈类似正弦曲线形式振荡分布的截面侧向力。

For ensure safety normal use upmentioned equipment, then had to eliminate existent all sorts ofs disturbance in electrified wire netting, such as press, wave gush, depression, sinkness, aiguille disturb and so on … Base on above concept, our company de engineer Men cumulate ten number year current supply device de designer manufacture experience, very adopt sines energys dispensers circuit and our companys specific high-tech, launch this new generation de purify AC power certain press utensil.

为了保证安全正常的使用上述设备，就必须消除电网中所存在的各种干扰，诸如过压，波涌，低压，下陷，尖峰干扰等等…基於以上理念，本公司的工程师们累积了十数年电源设备的设计制造经验，特采用正弦能量分配器电路及本公司特有的高新技术，推出此新一代的净化交流电源稳压器。

The solution composed by algebraic polynomial with double sine series is used to satisfy the corner conditions.

另外用代数多项式和双正弦级数组成的解来满足角点条件。

The algebraic polynomial with double sine series solutions can also satisfy the problem of boundary conditions at four comers.

还有代数多项式和双正弦级数解，它能满足4个角的边界条件问题。

Meanwhile, this detected voltage difference is amplified and filtered, and finally the processed signal is transmitted to the analog input of the DAQ card for further software operation, display, and storage.

其工作原理是利用DAQ卡类比输出通道，送出不同频率且幅值恒定的正弦电压信号，透过修正型Howland定电流驱动电路将电压信号转成电流信号加入体内，由量测电极取出电压信号经放大滤波后，把讯号送入类比输入DAQ卡，并在LabVIEW人机介面上做运算处理、分析、显示与储存。

The analogue method and FFT method, as the basic measurement techniques for distortion are discussed, the technique and the difficulties of distortion measurement is analyzed in detail.

叙述了正弦信号源失真的分类：谐波失真、噪声失真和杂波失真；讨论了失真测量的基本技术的优点和局限性，分析了失真测量技术的难点和技术状况；介绍了谐波失真和总失真度的定义。

Comparing EMD method with traditional FFT method in the analytical process, Hilbert-Huang transformation is found to be superior in performance. Structural response of the warship subjected to underwater explosion is simulated numerically, and EMD method is applied to analyzing the structural impulse signals.

该方法不把信号分解成正弦或余弦函数，因此既能分析线性稳态信号又可用于非线性非平稳信号的分析，且避免了高频干扰结果的出现，被认为是近年来对以Fourier变换为基础的线性和稳态谱分析的一个重大突破。

Cynanchum Lingtai apricot production in the average weight 65 grams, the brightly-colored fruit, juicy rich, sweet-sour taste, sweet from the nucleolus, when the late Qing Dynasty famous Shaanxi, Gansu provinces, the Qing imperial court Tongzhi tribute for years.

灵台生产的牛心杏平均单果重65克，果实色泽鲜艳，汁多味浓，甜酸适口，离核仁甜，清末时就驰名陕、甘两省，清同治年间曾为朝廷贡品。

Chenopodium album,Solanum nigrum, and Amaranthus retroflexus were very susceptible to the herbicides. Polygonum persicaria and Abutilon theophrasti were relatively less susceptible to the herbicides, and Lycopersicon esculentum was not susceptible to it. The relationship between reduction rates of weed biomass and PPM values of weed leaves 2,4, and 6 days after treatment was established.

供试的6种杂草对该混剂的敏感性存在显著差异：红心藜Chenopodium album、龙葵Solanum nigrum和反枝苋Amaranthus retroflexus对该混剂最敏感，ED90值分别为47.65、71.67和29.17g/hm2；春蓼Polygonum persicaria和苘麻Abutilon theophrasti敏感，ED90值分别为96.91、114.20g/hm2；而番茄不敏感。