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The interference between ω and ωext results in jumps in the dc currentvoltage characteristics when ω and ωext are harmonically related1.


The Hilbert spectrum reveals maxima at 26, 39.7, and 66.9?cpd, but not at 52.7?cpd, suggesting that it is harmonically related to the oscillation at 26.0?cpd.


Dichoptic interaction of harmonically related spatial and temporal frequencies


A comparative study is made of the stepped structure of atmospherics during sunrise and sunset hours at three harmonically related frequencies in the VLF band, observed at the coast of the Bay of Bengal.


The calls consist of harmonically related frequencies and are produced by forcing the air out of the oral cavity through the larynx and into the lungs.

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 This paper introduces how to best the frequency response of a superlowpass filter by a microcomputer. The customary signal exciting the filter is a slowly swept sine. Due to the development of digital signal processing algorithms and especially the efficient implementation of the discrete Fourier transform (DFT) with the fast Fourier transform (FFT), it becomes possible to use more complex input signals. Instead of exciting the filter under test frequency by frequency, it is possible to generate arbitrary waveform... This paper introduces how to best the frequency response of a superlowpass filter by a microcomputer. The customary signal exciting the filter is a slowly swept sine. Due to the development of digital signal processing algorithms and especially the efficient implementation of the discrete Fourier transform (DFT) with the fast Fourier transform (FFT), it becomes possible to use more complex input signals. Instead of exciting the filter under test frequency by frequency, it is possible to generate arbitrary waveform with a broadband spaotrum, using a digitaltoanalog (D/A) converter, to gather all the speetral information in one measurement. In many applications, the prescribed spectral shape is a fiab spectrum. One waveform that has such a flat spectrum is a sharp impulsa, but in this case all the power is concentrated at one point in time, leading to a maximum peak power. This results in an important reduction of the measurement time, bub also in an undesired accuracy loss of the measurement results if no spacial precautions were taken. According to Schroader's method a waveform that is the sum of a number of harmonically related cosine waves with equal amplitudes and with modulated phases for reducing the peakfactor has been generated. The data file, which is discretely calculated by the microcomputer according to one period of the waveform, has been created. While the filter is tesbed, the data file will be read into the memory of the microcomputer. By interrupting the CPU of the microcomputer at regular intervals, the waveform is sent to the filter through the digitaltoanalog converter.At the same time, the output of the filter is collected by the microcomputer through an analogtodigital converter. The frequency response of the filter can be obtained by FFT for the output. Thus the test can be performed in a shorter time with better accuracy.  介绍采用中断方法由微计算机和D/A转换器发生低峰值系数多谐波合成信号作为超低通滤波器的输入信号,并同时经由A/D转换器采集该滤波器的输出信号.通过对滤波器输出波形进行快速富里叶变换实现对超低通滤波器幅频响应特性的快速测试.  Objective In order to examine EEG respones in photic driving in subjects with schizophrenia. Methods After a routine EEG examination, a photic stimulation was given to 45 paranoid schizophrenic patients and 50 sex and age matched control subjects. The frequencies of photic stimulation were 5, 10 and 15 Hz. Absolute power was examined using the fast Fourier transformation (FFT), and the amplitudes were measured. Results Quantitative analysis of EEG activity during photic stimulation demonstrated that the... Objective In order to examine EEG respones in photic driving in subjects with schizophrenia. Methods After a routine EEG examination, a photic stimulation was given to 45 paranoid schizophrenic patients and 50 sex and age matched control subjects. The frequencies of photic stimulation were 5, 10 and 15 Hz. Absolute power was examined using the fast Fourier transformation (FFT), and the amplitudes were measured. Results Quantitative analysis of EEG activity during photic stimulation demonstrated that the patients had a uniform topographic profile in EEG amplitude for the alpha bands. Significant group differences was found predominantly over the posterotemporal and occipital regions in the left hemisphere. No significant differences was found in amplitude for the frequency bands harmonically related to the stimulus frequency. In addition, in the resting EEG, the patients showed a significantly lower alpha 2 band amplitude over all recording regions when compared with the normal controls. Conclusions The present fingings indicate abnomal photic driving responses, suggest a dysfunction in the mechanisms underlying EEG alpha generation in schizophrenia, and support the hypothesis of left hemispheric dysfunction in this disorder.  目的 用定量分析法研究精神分裂症脑电图光驱动反应。方法 对 4 5例偏执型精神分裂症患者和正常健康者 5 0例 ,记录安静状态下脑电图 ,并进行闪光刺激。闪光刺激的频率为 5、1 0和 1 5Hz。经自动快速傅立叶转换 (FFT) ,将安静状态和闪光刺激中的脑电图功率值转换成振幅 ,对两组进行比较。结果 闪光刺激中 ,1 0Hz光刺激相对应的α带域 (9 5～ 1 0 5Hz)的振幅显示出独特的曲线 ,精神分裂症缺乏α波枕部优势特征 ,两组间的差异在左侧大脑半球的后颞部及枕部更显著 (P <0 0 5 )。安静状态下 ,精神分裂症患者组在α2 波带的所有部位比正常对照组有显著低的振幅 (P <0 0 5 ) ,而在其他波带的差异无显著意义。结论 精神分裂症有异常的光驱动反应 ,存在α波发生源的功能异常 ,支持本病左半球功能障碍的假说  The main purpose of the paper is to detect the helicopter target using a single passive acoustic sensor. Because the power spectrum of the helicopter acoustic signal consists of strong harmonically related tones superimposed on a broadband random component, we put emphasis on the algorithm study of Harmonic Set (HS) detection method in the frequency domain. Test on the real data shows that the HS detection method has good performance to the helicopter in almost all cases, and can extract effective features... The main purpose of the paper is to detect the helicopter target using a single passive acoustic sensor. Because the power spectrum of the helicopter acoustic signal consists of strong harmonically related tones superimposed on a broadband random component, we put emphasis on the algorithm study of Harmonic Set (HS) detection method in the frequency domain. Test on the real data shows that the HS detection method has good performance to the helicopter in almost all cases, and can extract effective features for the helicopter target identification furthermore.  利用单个被动声传感器的声信号进行直升机目标检测,介于直升机声信号的功率谱是由一系列强相关的谐波分量叠加于宽带随机分量组成,着重研究在频域中的谐波集(HS)检测并给出详细算法。通过大量实测信号的测试表明,该方法对于不同飞行状态和距离下的直升机均有较强的检测能力,而且可以进一步为直升机目标识别分类提取有效的特征量。   << 更多相关文摘 
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