By computing the quadratic phase (QP)function of the signal,it is shown that the QP function is concentrated along the frequency rate law of the signal So the peak of the QP function yields the estimates of the frequency rate,and the initial frequency is obtained by the dechirp technique.

By fractional dimension search,the Chirp rate,initial frequency,pulse width and time of arrive are estimated with relatively high accuracy at negative SNR.

Based on the remainder theorem and direct dechirp operation,an algorithm for estimation of chirp rate and initial frequency of the subsampling wideband LFM signal unambiguously is presented.

Cropping mechanism is a key component for variant frequency vibration cropping,and its excited frequency directly affects manufacturing quality and production efficiency.

By using the statistical analysis and mathematical model establishment technique, the vibration frequency and perpendicular velocity of metering disc mathematical models were established, the influence of the vibration frequency and perpendicular velocity of metering disc on the seeding apparatus was analyzed, and the mechanism for the seeding uniformity was confirmed.

In this paper a study on the effects of different vibration frequency on the reduction extent of welding residual stress systematicly is implemented.

The design variables include the excitation frequency and the stiffness of vibration isolation system.

By calculating,it is found that the bent shaft natural frequency is intensive at low-level frequency segment,there are only two available frequency interval,the current excitation frequency is in the mode frequency interval[15,16],the other available frequency interval is fixed frequency interval[23,24].