Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic...Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic exploration adopts a geometry in which the sources are downhole and receivers are on the ground which can reduce the influence of complex surfaces on seismic wave propagation(to some extent).Through numerical simulations and real data analysis,it was noted that in areas with complex surfaces and large numbers of underground karst caves,seismic waves generated in shallow boreholes are easily affected by various surface and multiple waves as well as by scattering from karst bodies.Therefore,the quality of the reflected seismic data is extremely low.Also,it is difficult to improve the signal to noise ratio(SNR)with conventional noise filtering methods.However,when the source depth is increased,the quality of the reflected waves can be improved.This is exactly what the RVSP method accomplishes.Besides,for the RVSP method,due to its particular geometry,the apparent velocities of the reflected waves and most interference waves are quite different,which can help to filter most noise to further improve the SNR of the reflected signals.In this study,a 3 D-RVSP exploration study using 8-hole joint acquisition was conducted in a typical karst landform.The results show that the 3 D-RVSP method can obtain higher quality seismic data for complex surface conditions that have large numbers of underground karst caves.Furthermore,multi-hole joint acquisition for 3 D-RVSP has higher data collection efficiency and better uniformity of underground coverage.Therefore,in this study,38 faults were accurately revealed and at high resolution based on the 3 D-RVSP imaging results.展开更多
In the practical measurement of signal to noise ratio(SNR)of analog-to-digital converters(ADCs)by using fast Fourier transformation(FFT)method,the non-coherent sampling is inevitable,leading to spectral leakage which ...In the practical measurement of signal to noise ratio(SNR)of analog-to-digital converters(ADCs)by using fast Fourier transformation(FFT)method,the non-coherent sampling is inevitable,leading to spectral leakage which in turn affects the calculation accuracy and final measurement results.In this paper,a new method based on the Blackman-Harris windowed triple-spectrum-line interpolation is presented for the measurement of ADCs SNR by FFT.The simulation platform is built based on MATLAB and the behavioral dynamic models of the high-speed ADC products of Analog Devices Inc.(ADI)are simulated.The simulation results show that,even in the case of the maximum non-coherent degree,the SNR error is less than0.23dB and reaches the testing standards provided by ADI,confirming that the proposed method is effective for suppressing the spectral leakage effects and improving the SNR test accuracy.展开更多
Given external disturbances and system uncertainties,a nonsingular fast terminal sliding mode control(NFTSMC)method integrated a nonlinear disturbance observer(NDO)is put forward for quadrotor aircraft.First,a NDO is ...Given external disturbances and system uncertainties,a nonsingular fast terminal sliding mode control(NFTSMC)method integrated a nonlinear disturbance observer(NDO)is put forward for quadrotor aircraft.First,a NDO is proposed to estimate the actual values of uncertainties and disturbances.Second,the NFTSM controller based on the reaching law is designed for the attitude subsystem(inner loop),and the control strategy can ensure Euler angles’fast convergence and stability of the attitude subsystem.Moreover,the NFTSMC strategy combined with backstepping is proposed for the position subsystem(outer loop),which can ensure subsystem tracking performance.Finally,comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control(SMC)and the SM integral backstepping control under uncertainties and disturbances.展开更多
Power consumption in test mode is much higher than that in normal mode,which is prone to causing circuit damage and reducing the yield of chips.To reduce the power dissipation efficiently,a modified linear feedback sh...Power consumption in test mode is much higher than that in normal mode,which is prone to causing circuit damage and reducing the yield of chips.To reduce the power dissipation efficiently,a modified linear feedback shift register(LFSR)is designed to decrease switching activity dramatically during the generation of address sequences for memory built-in self-test(MBIST).The address models are generated by a blend of two address generators with an optimized address partition and two distinct controlled clock signals.An address generator circuit for MBIST of 64 k×32 static random access memory(SRAM)is designed to illustrate the proposed scheme.Experimental results show that when the address bus size is 16 bits,compared with the traditional LFSR,the proposed LFSR can reduce the switching activity and dynamic power by 71.1%and 68.2%,respectively,with low area overhead.展开更多
基金This work was supported by the Shanghai Municipal Key Clinical Specialty,“Strong Body”Construction Program-Department of Pulmonary Medicine,Zhongshan Hospital,Fudan University.
基金funded jointly by National Key Research and Development Program of China(2017YFC0804105)Fundamental Research Funds for the Central Universities of China(2015XKMS036)+1 种基金Natural Science Foundation of Jiangsu Province(BK20160245)a Project Funded by Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Conventional surface seismic exploration in areas with complex surfaces such as karst landforms has been faced with the problem of poor excitation and reception conditions.RVSP(reverse vertical seismic profile)seismic exploration adopts a geometry in which the sources are downhole and receivers are on the ground which can reduce the influence of complex surfaces on seismic wave propagation(to some extent).Through numerical simulations and real data analysis,it was noted that in areas with complex surfaces and large numbers of underground karst caves,seismic waves generated in shallow boreholes are easily affected by various surface and multiple waves as well as by scattering from karst bodies.Therefore,the quality of the reflected seismic data is extremely low.Also,it is difficult to improve the signal to noise ratio(SNR)with conventional noise filtering methods.However,when the source depth is increased,the quality of the reflected waves can be improved.This is exactly what the RVSP method accomplishes.Besides,for the RVSP method,due to its particular geometry,the apparent velocities of the reflected waves and most interference waves are quite different,which can help to filter most noise to further improve the SNR of the reflected signals.In this study,a 3 D-RVSP exploration study using 8-hole joint acquisition was conducted in a typical karst landform.The results show that the 3 D-RVSP method can obtain higher quality seismic data for complex surface conditions that have large numbers of underground karst caves.Furthermore,multi-hole joint acquisition for 3 D-RVSP has higher data collection efficiency and better uniformity of underground coverage.Therefore,in this study,38 faults were accurately revealed and at high resolution based on the 3 D-RVSP imaging results.
基金Summit of the Six Top Talents Program of Jiangsu Province(No.2013-DZXX-027)Fundamental Research Funds for the Central Universities(Nos.JUSRP51510,JUSRP51323B)Graduate Student Innovation Program for Universities of Jiangsu Province(Nos.SJLX16_0500,KYLX16_0776,SJCX17_0510)
文摘In the practical measurement of signal to noise ratio(SNR)of analog-to-digital converters(ADCs)by using fast Fourier transformation(FFT)method,the non-coherent sampling is inevitable,leading to spectral leakage which in turn affects the calculation accuracy and final measurement results.In this paper,a new method based on the Blackman-Harris windowed triple-spectrum-line interpolation is presented for the measurement of ADCs SNR by FFT.The simulation platform is built based on MATLAB and the behavioral dynamic models of the high-speed ADC products of Analog Devices Inc.(ADI)are simulated.The simulation results show that,even in the case of the maximum non-coherent degree,the SNR error is less than0.23dB and reaches the testing standards provided by ADI,confirming that the proposed method is effective for suppressing the spectral leakage effects and improving the SNR test accuracy.
基金the National Natural Science Foundation of China(No.52175100)the Natural Science Foundation of Jiangsu Province(No.BK20201379)+2 种基金the 2020 Industrial Transformation and Upgrading Project of Industry and Information Technology Department of Jiangsu Province(No.JITC-2000AX0676-71)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(No.NY221076)the Scientific and Technological Achievements Transformation Project of Jiangsu Province(No.BA2020004)。
文摘Given external disturbances and system uncertainties,a nonsingular fast terminal sliding mode control(NFTSMC)method integrated a nonlinear disturbance observer(NDO)is put forward for quadrotor aircraft.First,a NDO is proposed to estimate the actual values of uncertainties and disturbances.Second,the NFTSM controller based on the reaching law is designed for the attitude subsystem(inner loop),and the control strategy can ensure Euler angles’fast convergence and stability of the attitude subsystem.Moreover,the NFTSMC strategy combined with backstepping is proposed for the position subsystem(outer loop),which can ensure subsystem tracking performance.Finally,comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control(SMC)and the SM integral backstepping control under uncertainties and disturbances.
基金Foundation items:Fundamental Research Funds for the Central Universities(No.JUSRP51510)Primary Research&Development Plan of Jiangsu Province(No.BE2019003-2)。
文摘Power consumption in test mode is much higher than that in normal mode,which is prone to causing circuit damage and reducing the yield of chips.To reduce the power dissipation efficiently,a modified linear feedback shift register(LFSR)is designed to decrease switching activity dramatically during the generation of address sequences for memory built-in self-test(MBIST).The address models are generated by a blend of two address generators with an optimized address partition and two distinct controlled clock signals.An address generator circuit for MBIST of 64 k×32 static random access memory(SRAM)is designed to illustrate the proposed scheme.Experimental results show that when the address bus size is 16 bits,compared with the traditional LFSR,the proposed LFSR can reduce the switching activity and dynamic power by 71.1%and 68.2%,respectively,with low area overhead.
