In this study we performed a classical spectrum analysis of seismic waveforms recorded at far field stations of the great MW7.9 Wenchuan earthquake to observe the shifts of the corner frequency with azimuth due to the...In this study we performed a classical spectrum analysis of seismic waveforms recorded at far field stations of the great MW7.9 Wenchuan earthquake to observe the shifts of the corner frequency with azimuth due to the Doppler effect.Our results show that this damaging great earthquake had a dominating rupture propagation direction of 64.0°.The equivalent radius of the fault rupture surface was estimated to be 33 km,yielding the rupture area of about 3 500 km2.Thus the length of the rupture fault surface is about 230 km if the depth（or width） extent is 15 km.The computer program developed in this study can quickly provide the information about the source of a future large（damaging） earthquake,which could be very useful for predicting aftershocks and planning the rescue operations.展开更多
Doppler radar have become one of the most important instruments for weather now casting,and for meso-scale weather research because of its higher spatial and temporal resolutions. A dealing system for Doppler radar gr...Doppler radar have become one of the most important instruments for weather now casting,and for meso-scale weather research because of its higher spatial and temporal resolutions. A dealing system for Doppler radar graphic was researched and implemented so as to providing a convenient tool for users. We research and realized CINRAD/XD Doppler radar's graphic system. It contains three important parts:reading,standardization and pretreatment. It can be used very easily and conveniently. Besides,the system can be expanded and transplanted simply.展开更多
A novel rotational invariance technique for blind estimates of direction of arrival (I)OA) and Doppler frequency with unknown array manifold due to array sensor uncertainties is proposed, taking Doppler frequency diff...A novel rotational invariance technique for blind estimates of direction of arrival (I)OA) and Doppler frequency with unknown array manifold due to array sensor uncertainties is proposed, taking Doppler frequency difference between a successive pulses as rotational parameter. The effectiveness of the new method is confirmed by computer simulation. Compared with the existing 2-D DOA-frequeucy estimate techniques, the computation load of the proposed method can be saved greatly.展开更多
The proposed Doppler measurement technique shows that the Doppler measurements can be accomplished by a single pulse with multiple frequency components through optical fibre delay lines.Range and velocity ambiguity ca...The proposed Doppler measurement technique shows that the Doppler measurements can be accomplished by a single pulse with multiple frequency components through optical fibre delay lines.Range and velocity ambiguity can be removed,and the velocity resolution can be improved dramatically by using long optical fibre delay lines.Furthermore,the velocity resolution can be modified by adjusting the length of optical fibre delay lines.In addition,the proposed radar can achieve high range resolution by using a single wideband pulse.As a result,the new approach can improve radar performance significantly.展开更多
The problem of joint direction of arrival (DOA) and Doppler frequency estimation in monostatic multiple-input multiple-output (MIMO) radar is studied and a computationally efficient multiple signal classification (CE-...The problem of joint direction of arrival (DOA) and Doppler frequency estimation in monostatic multiple-input multiple-output (MIMO) radar is studied and a computationally efficient multiple signal classification (CE-MUSIC) algorithm is proposed.Conventional MUSIC algorithm for joint DOA and Doppler frequency estimation requires a large computational cost due to the two dimensional (2D) spectral peak searching.Aiming at this shortcoming,the proposed CE-MUSIC algorithm firstly uses a reduced-dimension transformation to reduce the subspace dimension and then obtains the estimates of DOA and Doppler frequency with only one-dimensional (1D) search.The proposed CE-MUSIC algorithm has much lower computational complexity and very close estimation performance when compared to conventional 2D-MUSIC algorithm.Furthermore,it outperforms estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm.Meanwhile,the mean squared error (MSE) and Cramer-Rao bound (CRB) of joint DOA and Doppler frequency estimation are derived.Detailed simulation results illustrate the validity and improvement of the proposed algorithm.展开更多
In this paper, we propose extraction of signals buried in non-ergodic processes. It is shown that the proposed method extracts signals defined in a non-ergodic framework without averaging or smoothing in the direct ti...In this paper, we propose extraction of signals buried in non-ergodic processes. It is shown that the proposed method extracts signals defined in a non-ergodic framework without averaging or smoothing in the direct time or frequency domain. Extraction is achieved independently of the nature of noise, correlated or not with the signal, colored or white, Gaussian or not, and locations of its spectral extent. Performances of the pro-posed extraction method and comparative results with other methods are demonstrated via experimental Doppler velocimetry measurements.展开更多
文摘In this study we performed a classical spectrum analysis of seismic waveforms recorded at far field stations of the great MW7.9 Wenchuan earthquake to observe the shifts of the corner frequency with azimuth due to the Doppler effect.Our results show that this damaging great earthquake had a dominating rupture propagation direction of 64.0°.The equivalent radius of the fault rupture surface was estimated to be 33 km,yielding the rupture area of about 3 500 km2.Thus the length of the rupture fault surface is about 230 km if the depth（or width） extent is 15 km.The computer program developed in this study can quickly provide the information about the source of a future large（damaging） earthquake,which could be very useful for predicting aftershocks and planning the rescue operations.
基金The important science and technology itemof Jiangsu province.(BR2004012)
文摘Doppler radar have become one of the most important instruments for weather now casting,and for meso-scale weather research because of its higher spatial and temporal resolutions. A dealing system for Doppler radar graphic was researched and implemented so as to providing a convenient tool for users. We research and realized CINRAD/XD Doppler radar's graphic system. It contains three important parts:reading,standardization and pretreatment. It can be used very easily and conveniently. Besides,the system can be expanded and transplanted simply.
基金Supported by the National Natural Science Foundation of China
文摘A novel rotational invariance technique for blind estimates of direction of arrival (I)OA) and Doppler frequency with unknown array manifold due to array sensor uncertainties is proposed, taking Doppler frequency difference between a successive pulses as rotational parameter. The effectiveness of the new method is confirmed by computer simulation. Compared with the existing 2-D DOA-frequeucy estimate techniques, the computation load of the proposed method can be saved greatly.
文摘The proposed Doppler measurement technique shows that the Doppler measurements can be accomplished by a single pulse with multiple frequency components through optical fibre delay lines.Range and velocity ambiguity can be removed,and the velocity resolution can be improved dramatically by using long optical fibre delay lines.Furthermore,the velocity resolution can be modified by adjusting the length of optical fibre delay lines.In addition,the proposed radar can achieve high range resolution by using a single wideband pulse.As a result,the new approach can improve radar performance significantly.
基金supported in part by the Funding for Outstanding Doctoral Dissertation in NUAA (No.BCXJ1503)the Funding of Jiangsu Innovation Program for Graduate Education(No.KYLX15_0281)the Fundamental Research Funds for the Central Universities
文摘The problem of joint direction of arrival (DOA) and Doppler frequency estimation in monostatic multiple-input multiple-output (MIMO) radar is studied and a computationally efficient multiple signal classification (CE-MUSIC) algorithm is proposed.Conventional MUSIC algorithm for joint DOA and Doppler frequency estimation requires a large computational cost due to the two dimensional (2D) spectral peak searching.Aiming at this shortcoming,the proposed CE-MUSIC algorithm firstly uses a reduced-dimension transformation to reduce the subspace dimension and then obtains the estimates of DOA and Doppler frequency with only one-dimensional (1D) search.The proposed CE-MUSIC algorithm has much lower computational complexity and very close estimation performance when compared to conventional 2D-MUSIC algorithm.Furthermore,it outperforms estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm.Meanwhile,the mean squared error (MSE) and Cramer-Rao bound (CRB) of joint DOA and Doppler frequency estimation are derived.Detailed simulation results illustrate the validity and improvement of the proposed algorithm.
文摘In this paper, we propose extraction of signals buried in non-ergodic processes. It is shown that the proposed method extracts signals defined in a non-ergodic framework without averaging or smoothing in the direct time or frequency domain. Extraction is achieved independently of the nature of noise, correlated or not with the signal, colored or white, Gaussian or not, and locations of its spectral extent. Performances of the pro-posed extraction method and comparative results with other methods are demonstrated via experimental Doppler velocimetry measurements.
