In this paper,we propose a new biased estimator of the regression parameters,the generalized ridge and principal correlation estimator.We present its some properties and prove that it is superior to LSE(least squares ...In this paper,we propose a new biased estimator of the regression parameters,the generalized ridge and principal correlation estimator.We present its some properties and prove that it is superior to LSE(least squares estimator),principal correlation estimator,ridge and principal correlation estimator under MSE(mean squares error) and PMC(Pitman closeness) criterion,respectively.展开更多
Before the implementation of offshore oil and gas exploitation,it is essential to understand the various factors that influence the stability of submarine sediments surrounding the project.Considering the factors such...Before the implementation of offshore oil and gas exploitation,it is essential to understand the various factors that influence the stability of submarine sediments surrounding the project.Considering the factors such as cost and operability,it is not feasible to assess the physical-mechanical properties of sediments covering the entire region by borehole sampling.In this study,the correlation between near seafloor seismic amplitude and the mean shear strength of shallow sediments was explored using seismic and core testing data from the northern continental slope area of the South China Sea.Results showed that the mean water content of sediments in the layer up to 12 m below the seafloor(mbsf)gradually increased with increasing water depth,and the mean shear strength tended to decrease rapidly near the 1000 m depth contour.The near seafloor seismic amplitude could reflect the mean shear strength of sediments in the 12 mbsf layer under seismic frequency of 65 Hz and wave velocity of 1600 m/s.When the mean shear strength was greater than 10 kPa or the water depth was less than 1000 m,there was a significant linear positive correlation between mean shear strength and near seafloor seismic amplitude.Otherwise,there was a significant linear negative correlation between mean shear strength and near seafloor seismic amplitude.On the basis of these correlations,the pattern of shear strength was estimated from near seafloor seismic amplitude and mapped.The mean shear strength of sediments above 12 mbsf gradually decreased with increasing water depth in the continental slope area,whereas little change occurred in the continental shelf and the end of the canyon.Within the canyon area,the mean shear strength of sediments was characterized by larger values in both sides of the canyon walls and smaller values in the canyon bottom,which was consistent with the infinite slope stability theory.The study provides a method for using near seafloor seismic amplitude data to guide sediment sampling design,and presents a continuous dataset of sediment strength for the simulation of regional sediment stability.展开更多
Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging resu...Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging result. In this letter, the principle and algorithms of Doppler centroid frequency estimation are introduced. Then the echo data of ScanSAR system is analyzed. Based on the algorithms of energy balancing and correlation Doppler estimator in the estimation of Doppler centroid frequency in strip mode SAR, an improved method for Doppler centroid frequency estimation in ScanSAR is proposed. The method has improved the accuracy of Doppler centroid frequency estimation in ScanSAR by zero padding between burst data. Finally, the proposed method is validated with the processing of ENVIronment SATellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) wide swath raw data.展开更多
This paper proposes a new signal noise level estimation approach by local regions. The estimated noise variance is applied as the threshold for an improved empirical mode decomposition（EMD） based signal denoising me...This paper proposes a new signal noise level estimation approach by local regions. The estimated noise variance is applied as the threshold for an improved empirical mode decomposition（EMD） based signal denoising method. The proposed estimation method can effectively extract the candidate regions for the noise level estimation by measuring the correlation coefficient between noisy signal and a Gaussian filtered signal. For the improved EMD based method, the situation of decomposed intrinsic mode function（IMFs） which contains noise and signal simultaneously are taken into account. Experimental results from two simulated signals and an X-ray pulsar signal demonstrate that the proposed method can achieve better performance than the conventional EMD and wavelet transform（WT） based denoising methods.展开更多
Based on the structures of the short preamble and long preamble, which are defined for synchronization in IEEES02.16e specification, the robust synchronization algorithm for IEEES02.16e OFDM system is proposed. The co...Based on the structures of the short preamble and long preamble, which are defined for synchronization in IEEES02.16e specification, the robust synchronization algorithm for IEEES02.16e OFDM system is proposed. The correlations among the sample sequences in the preamble are investigated, especially the correlation between the first sample sequence and the last sample sequence in the long preamble. The conventional joint timing and frequency synchronization algorithm is reviewed based on the short preamble referring to the algorithm proposed by Schmidl, then a robust joint timing and frequency synchronization algorithm is proposed based on the long preamble. The simulations in the multi-path and frequency selective fading channel show that the proposed algorithm has improved the performances of timing metric plateau, timing offset and synchronization acquisition time even when signal-to-noise ratio is less than -5 dB.展开更多
In this paper, we investigate the variable selection problem of the generalized regression models. To estimate the regression parameter, a procedure combining the rank correlation method and the adaptive lasso techniq...In this paper, we investigate the variable selection problem of the generalized regression models. To estimate the regression parameter, a procedure combining the rank correlation method and the adaptive lasso technique is developed, which is proved to have oracle properties. A modified IMO （iterative marginal optimization） algorithm which directly aims to maximize the penalized rank correlation function is proposed. The effects of the estimating procedure are illustrated by simulation studies.展开更多
基金Foundation item： the National Natural Science Foundation of China （Nos. 60736047 10671007+2 种基金 60772036） the Foundation of Beijing Jiaotong University （Nos. 2006XM037 2007XM046）.
文摘In this paper,we propose a new biased estimator of the regression parameters,the generalized ridge and principal correlation estimator.We present its some properties and prove that it is superior to LSE(least squares estimator),principal correlation estimator,ridge and principal correlation estimator under MSE(mean squares error) and PMC(Pitman closeness) criterion,respectively.
基金The National Natural Science Foundation of China under contract No.41706065the Basic Scientific Fund for National Public Research Institutes of China under contract No.2015G08+1 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers of China under contract No.U1606401the National Program on Global Change and Air-sea Interaction of China under contract No.GASI-GEOGE-05.
文摘Before the implementation of offshore oil and gas exploitation,it is essential to understand the various factors that influence the stability of submarine sediments surrounding the project.Considering the factors such as cost and operability,it is not feasible to assess the physical-mechanical properties of sediments covering the entire region by borehole sampling.In this study,the correlation between near seafloor seismic amplitude and the mean shear strength of shallow sediments was explored using seismic and core testing data from the northern continental slope area of the South China Sea.Results showed that the mean water content of sediments in the layer up to 12 m below the seafloor(mbsf)gradually increased with increasing water depth,and the mean shear strength tended to decrease rapidly near the 1000 m depth contour.The near seafloor seismic amplitude could reflect the mean shear strength of sediments in the 12 mbsf layer under seismic frequency of 65 Hz and wave velocity of 1600 m/s.When the mean shear strength was greater than 10 kPa or the water depth was less than 1000 m,there was a significant linear positive correlation between mean shear strength and near seafloor seismic amplitude.Otherwise,there was a significant linear negative correlation between mean shear strength and near seafloor seismic amplitude.On the basis of these correlations,the pattern of shear strength was estimated from near seafloor seismic amplitude and mapped.The mean shear strength of sediments above 12 mbsf gradually decreased with increasing water depth in the continental slope area,whereas little change occurred in the continental shelf and the end of the canyon.Within the canyon area,the mean shear strength of sediments was characterized by larger values in both sides of the canyon walls and smaller values in the canyon bottom,which was consistent with the infinite slope stability theory.The study provides a method for using near seafloor seismic amplitude data to guide sediment sampling design,and presents a continuous dataset of sediment strength for the simulation of regional sediment stability.
文摘Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging result. In this letter, the principle and algorithms of Doppler centroid frequency estimation are introduced. Then the echo data of ScanSAR system is analyzed. Based on the algorithms of energy balancing and correlation Doppler estimator in the estimation of Doppler centroid frequency in strip mode SAR, an improved method for Doppler centroid frequency estimation in ScanSAR is proposed. The method has improved the accuracy of Doppler centroid frequency estimation in ScanSAR by zero padding between burst data. Finally, the proposed method is validated with the processing of ENVIronment SATellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) wide swath raw data.
基金supported by the China Aerospace Science and Technology Corporation’s Aerospace Science and Technology Innovation Fund Project(casc2013086)CAST Innovation Fund Project(cast2012028)
文摘This paper proposes a new signal noise level estimation approach by local regions. The estimated noise variance is applied as the threshold for an improved empirical mode decomposition（EMD） based signal denoising method. The proposed estimation method can effectively extract the candidate regions for the noise level estimation by measuring the correlation coefficient between noisy signal and a Gaussian filtered signal. For the improved EMD based method, the situation of decomposed intrinsic mode function（IMFs） which contains noise and signal simultaneously are taken into account. Experimental results from two simulated signals and an X-ray pulsar signal demonstrate that the proposed method can achieve better performance than the conventional EMD and wavelet transform（WT） based denoising methods.
文摘Based on the structures of the short preamble and long preamble, which are defined for synchronization in IEEES02.16e specification, the robust synchronization algorithm for IEEES02.16e OFDM system is proposed. The correlations among the sample sequences in the preamble are investigated, especially the correlation between the first sample sequence and the last sample sequence in the long preamble. The conventional joint timing and frequency synchronization algorithm is reviewed based on the short preamble referring to the algorithm proposed by Schmidl, then a robust joint timing and frequency synchronization algorithm is proposed based on the long preamble. The simulations in the multi-path and frequency selective fading channel show that the proposed algorithm has improved the performances of timing metric plateau, timing offset and synchronization acquisition time even when signal-to-noise ratio is less than -5 dB.
基金supported by National Natural Science Foundation of China(10901162)supported by the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(10XNF073)supported by China Postdoctoral Science Foundation(2014M550799)
文摘In this paper, we investigate the variable selection problem of the generalized regression models. To estimate the regression parameter, a procedure combining the rank correlation method and the adaptive lasso technique is developed, which is proved to have oracle properties. A modified IMO （iterative marginal optimization） algorithm which directly aims to maximize the penalized rank correlation function is proposed. The effects of the estimating procedure are illustrated by simulation studies.
