The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is prop...The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.展开更多
Objective: to study and analyze the clinical effect of high frequency color Doppler ultrasound in the diagnosis of peripheral nerve injury. Methods: a total of 87 patients diagnosed with peripheral nerve injury during...Objective: to study and analyze the clinical effect of high frequency color Doppler ultrasound in the diagnosis of peripheral nerve injury. Methods: a total of 87 patients diagnosed with peripheral nerve injury during surgical treatment in our hospital from July 2019 to June 2020 were selected in this study. All 87 patients in the study group underwent routine examination and high-frequency color Doppler ultrasound. According to the basis of diagnosis, the diagnostic results of routine examination were classified into the conventional group, and the diagnostic results of high-frequency color Doppler ultrasound were classified into the observation group. The difference of detection rates of patients in the study group in these two different diagnostic methods was compared. Results: among the 87 patients in the observation group, 82 patients were diagnosed as peripheral nerve injury by high-frequency color Doppler ultrasound, and the diagnosis rate was 94.25%. In the routine group, only 56 patients were diagnosed as peripheral nerve injury by routine examination, and the diagnostic rate was 64.37%. The diagnostic rate of the observation group was significantly higher than that of the conventional group (p < 0.05). Conclusion: in the clinical diagnosis of patients with peripheral nerve injury, the application of high-frequency color Doppler ultrasound can better identify the lesion site of patients and improve the diagnostic accuracy of patients, and also reduce the rate of missed diagnosis. So that provide more reliable basis for clinicians to diagnose and treat diseases, thus improving the efficiency and quality of treatment of related diseases, which is worthy of promotion and use in clinical treatment.展开更多
Typhoon ' Meranti'(1010) is one of the rare offshore strengthened mini-typhoons,featured by heavy impacts,meandering moving route,small coverage,strong intensity and large difficulty in prediction and preventi...Typhoon ' Meranti'(1010) is one of the rare offshore strengthened mini-typhoons,featured by heavy impacts,meandering moving route,small coverage,strong intensity and large difficulty in prediction and prevention.Therefore,the partial characteristics of such typhoon are analyzed in this paper and the discussions of location of the typhoon in offshore area by Doppler radar are the focus of this paper.展开更多
An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the for...An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation（Fa FFA） in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle（LGA）.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
基金supported by the China Major State Basic Research Development Program(973 Program,No.2012CB316100)National Natural Science Foundation of China(No.61171064)+2 种基金the China National Science and Technology Major Project(No.2010ZX03003-003)NSFC(No.61021001)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2011D13)
文摘The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.
文摘Objective: to study and analyze the clinical effect of high frequency color Doppler ultrasound in the diagnosis of peripheral nerve injury. Methods: a total of 87 patients diagnosed with peripheral nerve injury during surgical treatment in our hospital from July 2019 to June 2020 were selected in this study. All 87 patients in the study group underwent routine examination and high-frequency color Doppler ultrasound. According to the basis of diagnosis, the diagnostic results of routine examination were classified into the conventional group, and the diagnostic results of high-frequency color Doppler ultrasound were classified into the observation group. The difference of detection rates of patients in the study group in these two different diagnostic methods was compared. Results: among the 87 patients in the observation group, 82 patients were diagnosed as peripheral nerve injury by high-frequency color Doppler ultrasound, and the diagnosis rate was 94.25%. In the routine group, only 56 patients were diagnosed as peripheral nerve injury by routine examination, and the diagnostic rate was 64.37%. The diagnostic rate of the observation group was significantly higher than that of the conventional group (p < 0.05). Conclusion: in the clinical diagnosis of patients with peripheral nerve injury, the application of high-frequency color Doppler ultrasound can better identify the lesion site of patients and improve the diagnostic accuracy of patients, and also reduce the rate of missed diagnosis. So that provide more reliable basis for clinicians to diagnose and treat diseases, thus improving the efficiency and quality of treatment of related diseases, which is worthy of promotion and use in clinical treatment.
文摘Typhoon ' Meranti'(1010) is one of the rare offshore strengthened mini-typhoons,featured by heavy impacts,meandering moving route,small coverage,strong intensity and large difficulty in prediction and prevention.Therefore,the partial characteristics of such typhoon are analyzed in this paper and the discussions of location of the typhoon in offshore area by Doppler radar are the focus of this paper.
基金supported by the National Natural Science Foundation of China(61372033)
文摘An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation（Fa FFA） in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle（LGA）.
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.
