摘要：The disguised covert detection method that imitates whale calls has received great attention in recent years because it can solve the traditional problem of the trade-off between long-range detection and covert ***,under strong reverberation conditions,traditional echo signal processing methods based on matched filtering will be greatly *** on this,a disguised sonar signal waveform design is proposed based on imitating whale calls and computationally efficient anti-reverberation echo signal processing ***,this article proposed a disguised sonar signal waveform design method based on imitating whale *** method uses linear frequency modulation(LFM)signals to replace LFM-like segments in real whale calls,and extracts the envelope of the real whale call’s LFM-like segment to modify the LFM ***,this article proposed an echo signal processing method of fractional Fourier transform(FrFT)based on target echo locating of synchronization *** method uses the synchronization signal to locate the target echo,and determines the step-size interval of the FrFT based on the information carried by the synchronization *** with the traditional FrFT,this method effectively reduces the amount of calculation and also improves the anti-reverberation ***,the excellent performance of the proposed method is verified by simulation results.

摘要：In order to achieve high precision measurement of inductance in a wide frequency range,a method of inductance measurement based on double-excitation auto-balancing bridge is *** this method,the direct digital synthesizer(DDS)as signal generator is used as the bridge excitation source,and the bridge is automatically balanced by adjusting and measuring the voltage *** standard resistors,the system can achieve high precision measurement of four-terminal pair inductors in the frequency range of *** at the low efficiency of bridge balancing,an iterative balancing algorithm based on the steepest descent method is *** order to suppress the interference caused by the initial phase change and non-integer periodic sampling,the high-precision measurement of the complex impedance of inductance is realized based on the all-phase fast Fourier transform(apFFT).Finally,the corresponding measurement system is built and the inductance measurement experiment is carried *** experimental results show that the relative error of the system for inductance measurement can be as low as 0.009%,and the optimal relative measurement uncertainty of the system can reach 9.89×10^(-4)compared with 5×10^(-5)of commercial impedance analyzer.

摘要：In order to improve the resolution of seismic acquisition,a new seismic acquisition system based on tangential laser Doppler effect with an optimized differential optical configuration is *** relative movement of the inertia object and the immobile frame is measured by laser Doppler effect,which can avoid the electromagnetic and thermometric interference,and the adoption of frequency-modulated (FM) transmission can improve the ability of *** frequency bandwidth is properly determined by analyzing the frequency of the Doppler *** velocity, displacement,acceleration, and frequency to be measured can be real-time acquired by frequency/velocity (F/V) converting the FM Doppler signal. A 100-dB dynamic range and the linear frequency range of 1.0 to 1000 Hz are realized.

摘要：With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath *** eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of *** an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 *** tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.