Four results of the rupture process of 14 April 2010 Yushu, Qinghai, earthquake, obtained by inverting the broadband seismic data of Global Seismographic Network （GSN） based on the inversion method of earthquake rup...Four results of the rupture process of 14 April 2010 Yushu, Qinghai, earthquake, obtained by inverting the broadband seismic data of Global Seismographic Network （GSN） based on the inversion method of earthquake rupture process, were compared and discussed. It is found that the Yushu earthquake has several basic characteristics as follows： 1 There exist two principal sub-events which correspond to two slip-concentrated patches being located near the hypocenter and to the southeast of the epicenter. The rupture of the slip-concentrated patch to the southeast of the epicenter broke though the ground surface; 2 The peak slip and peak slip-rate are about 2.1 m and 1.1 m/s, respectively, indicating that the Yushu earthquake is an event with large slip-rate on the fault plane; 3 Overall the Yushu earthquake is a unilateral rupture event with the rupture mainly propagating southeastward. The strong focusing of the seismic energy in the southeast of the epicenter due to the ＂seismic Doppler effect＂ reasonably accounts for the tremendous damage in the Yushu city.展开更多
Information about anisotropic resistivity is essential in real-time correlation,updating of formation model and making more confi dent geosteering decisions in logging-while-drilling(LWD)application.However,abnormal r...Information about anisotropic resistivity is essential in real-time correlation,updating of formation model and making more confi dent geosteering decisions in logging-while-drilling(LWD)application.However,abnormal responses such as curve separations and apparent resistivity“horns”often exist in the LWD resistivity measurements due to the infl uences of complex downhole environments.Thus,accurate formation resistivity is not readily available.In this paper,we present an effi cient inversion scheme for the rapid estimation of anisotropic resistivity from LWD resistivity measurements acquired in high-angle and horizontal wells.Several strategies are adopted in the inversion:(1)a one-dimensional(1D)simulator with a simplifi ed three-layered model guarantees the forward speed and keeps the number of inverted parameters as few as possible;(2)combined with geological and petrophysical bounds,the tool constraints derived from a detection capability analysis of LWD resistivity measurements are applied to scale down the inverted parameters’searching scope,which avoids meaningless solutions and accelerates the inversion signifi cantly;(3)multiple-initial guesses are used in the inversion to ensure a global solution.Inversion results over synthetic examples demonstrate that the proposed 1D inversion algorithm is well suited for complex formation structures.It is also robust and fast in extracting anisotropic resistivities from LWD resistivity measurements.展开更多
We conducted rapid inversions of rupture process for the 2023 earthquake doublet occurred in SE Türkiye,the first with a magnitude of M_(W)7.8 and the second with a magnitude of M_(W)7.6,using teleseismic and str...We conducted rapid inversions of rupture process for the 2023 earthquake doublet occurred in SE Türkiye,the first with a magnitude of M_(W)7.8 and the second with a magnitude of M_(W)7.6,using teleseismic and strong-motion data.The teleseismic rupture models of the both events were obtained approximately 88 and 55 minutes after their occurrences,respectively.The rupture models indicated that the first event was an asymmetric bilateral event with ruptures mainly propagating to the northeast,while the second one was a unilateral event with ruptures propagating to the west.This information could be useful in locating the meizoseismal areas.Compared with teleseismic models,the strong-motion models showed relatively higher resolution.A noticeable difference was found for the M_(W)7.6 earthquake,for which the strong-motion models shows a bilateral event,rather than a unilateral event,but the dominant rupture direction is still westward.Nevertheless,all strong-motion models are consistent with the teleseismic models in terms of magnitudes,durations,and dominant rupture directions.This suggests that both teleseismic and strong-motion data can be used for fast determination of major source characteristics.In contrast,the strong-motion data would be preferable in future emergency responses since they are recorded earlier and have a better resolution ability on the source ruptures.展开更多
Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harm...Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.展开更多
In this paper,a time-frequency associated multiple signal classification(MUSIC)al-gorithm which is suitable for through-wall detection is proposed.The technology of detecting hu-man targets by through-wall radar can b...In this paper,a time-frequency associated multiple signal classification(MUSIC)al-gorithm which is suitable for through-wall detection is proposed.The technology of detecting hu-man targets by through-wall radar can be used to monitor the status and the location information of human targets behind the wall.However,the detection is out of order when classical MUSIC al-gorithm is applied to estimate the direction of arrival.In order to solve the problem,a time-fre-quency associated MUSIC algorithm suitable for through-wall detection and based on S-band stepped frequency continuous wave(SFCW)radar is researched.By associating inverse fast Fouri-er transform(IFFT)algorithm with MUSIC algorithm,the power enhancement of the target sig-nal is completed according to the distance calculation results in the time domain.Then convert the signal to the frequency domain for direction of arrival(DOA)estimation.The simulations of two-dimensional human target detection in free space and the processing of measured data are com-pleted.By comparing the processing results of the two algorithms on the measured data,accuracy of DOA estimation of proposed algorithm is more than 75%,which is 50%higher than classical MUSIC algorithm.It is verified that the distance and angle of human target can be effectively de-tected via proposed algorithm.展开更多
In this letter,P × N-pointIFFT is proposed to replace the N-point IFFT and analog fre-quency conversion in an Orthogonal Frequency Division Multiplexing (OFDM)-based Ultra-WideBand (UWB) system,and a new algorith...In this letter,P × N-pointIFFT is proposed to replace the N-point IFFT and analog fre-quency conversion in an Orthogonal Frequency Division Multiplexing (OFDM)-based Ultra-WideBand (UWB) system,and a new algorithm,named fast P × N-pointIFFT,is designed to reduce the com-plexity of the P × N-pointIFFT in the proposed scheme.展开更多
We propose a direct solver for the three-dimensional Poisson equation with a variable coefficient,and an algorithm to directly solve the associated sparse linear systems that exploits the sparsity pattern of the coeff...We propose a direct solver for the three-dimensional Poisson equation with a variable coefficient,and an algorithm to directly solve the associated sparse linear systems that exploits the sparsity pattern of the coefficient matrix.Introducing some appropriate finite difference operators,we derive a second-order scheme for the solver,and then two suitable high-order compact schemes are also discussed.For a cube containing N nodes,the solver requires O(N^(3/2)log^(2)N)arithmetic operations and O(NlogN)memory to store the necessary information.Its efficiency is illustrated with examples,and the numerical results are analysed.展开更多
This paper deals with a unified and novel approach for analyzing the frequency and time domain performance of grounding systems.The proposed procedure is based on solving the full set of Maxwell's equations in the...This paper deals with a unified and novel approach for analyzing the frequency and time domain performance of grounding systems.The proposed procedure is based on solving the full set of Maxwell's equations in the frequency domain,and enables the exact computation of very near fields at the surface of the grounding grid,as well as far fields,by simple and accurate closed-form expressions for solving Sommerfeld integrals.In addition,the soil ionization is easily considered in the proposed method.The frequency domain responses are converted to the time domain by fast inverse Laplace transform.The results are validated and have shown acceptable accuracy.展开更多
The trace inverse functions Tr(λx^(-1)) over the finite field F_(2~n) are a class of very important Boolean functions and are used in many stream ciphers such as SFINKS,RAKAPOSHI,the simple counter stream cipher(SCSC...The trace inverse functions Tr(λx^(-1)) over the finite field F_(2~n) are a class of very important Boolean functions and are used in many stream ciphers such as SFINKS,RAKAPOSHI,the simple counter stream cipher(SCSC) presented by Si W and Ding C(2012),etc.In order to evaluate the security of those ciphers in resistance to(fast) algebraic attacks,the authors need to characterize algebraic properties of Tr(λx^(-1)).However,currently only some bounds on algebraic immunity of Tr(λx^(-1)) are given in the public literature,for example,the NGG upper bound and the Bayev lower bound,etc.This paper gives the exact value of the algebraic immunity of Tr(λx^(-1)) over F_(2~n),that is,AI(Tr(λx^(-1))) =[2n^(1/2)]- 2,where n ≥ 2,A ∈ F_(2~n) and λ≠ 0,which shows that Dalai's conjecture on the algebraic immunity of Tr(λx^(-1)) is correct.What is more,the authors demonstrate some weak properties of Tr(λx^(-1)) against fast algebraic attacks.展开更多
This paper proposes to use Fast Fourier Transform （ FFT ） / Inverse Fast Fourier Transform （IFFT）, instead of vector-matrix multiplication, to implement the spreading/despreoding in Carrier-Interferometry Orthogon...This paper proposes to use Fast Fourier Transform （ FFT ） / Inverse Fast Fourier Transform （IFFT）, instead of vector-matrix multiplication, to implement the spreading/despreoding in Carrier-Interferometry Orthogonal Frequency Division Multiplexing （ CI/OFDM） and Pseudo-Orthogonal Carrier lnterferometry OFDM （PO-CI/OFDM）. That can improve the signal processing efficiency of CI/OFDM and PO-CI/OFDM systems by about 2N/log2N and 2N/（ 1 ＋ log2 N） times respectively and dose not make any difference to the system function and performance. Moreover, the effi- ciency benefits will increase with the increase of the number of sub-carriers. In addition to that, we point out that the transmitter of CI/OFDM is actually technically equivalent to that of a single-carrier system with cyclic-prefix and the receiver of CI/OFDM is a typical OFDM receiver with CI despreading. Hence the low Peak-to-Average Power Ratio （PA- PR） property and high anti-fading performance of CI/OFDM system can be well explained .展开更多
基金supported by China Postdoctoral Science Foundation funded project (20080440435)the project (DQJB09B06) from Institute of Geophysics (IGP),China Earthquake Administration (CEA). Contribution No. is 10FE3002, IGP-CEA
文摘Four results of the rupture process of 14 April 2010 Yushu, Qinghai, earthquake, obtained by inverting the broadband seismic data of Global Seismographic Network （GSN） based on the inversion method of earthquake rupture process, were compared and discussed. It is found that the Yushu earthquake has several basic characteristics as follows： 1 There exist two principal sub-events which correspond to two slip-concentrated patches being located near the hypocenter and to the southeast of the epicenter. The rupture of the slip-concentrated patch to the southeast of the epicenter broke though the ground surface; 2 The peak slip and peak slip-rate are about 2.1 m and 1.1 m/s, respectively, indicating that the Yushu earthquake is an event with large slip-rate on the fault plane; 3 Overall the Yushu earthquake is a unilateral rupture event with the rupture mainly propagating southeastward. The strong focusing of the seismic energy in the southeast of the epicenter due to the ＂seismic Doppler effect＂ reasonably accounts for the tremendous damage in the Yushu city.
基金This work was supported by the National Natural Science Foundation of China(No.41904109,No.41974146,and No.42074134),China Postdoctoral Science Foundation(No.2018M640663),the Shandong Province Postdoctoral Innovation Projects(No.sdbh20180025),State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Eff ective Development Projects(No.20-YYGZ-KF-GC-11),and National key Laboratory of Electromagnetic Environment Projects(No.6142403200307).We also wish to thank peer reviewer,Hu Song and Wang Zhicai for their comments and suggestions.
文摘Information about anisotropic resistivity is essential in real-time correlation,updating of formation model and making more confi dent geosteering decisions in logging-while-drilling(LWD)application.However,abnormal responses such as curve separations and apparent resistivity“horns”often exist in the LWD resistivity measurements due to the infl uences of complex downhole environments.Thus,accurate formation resistivity is not readily available.In this paper,we present an effi cient inversion scheme for the rapid estimation of anisotropic resistivity from LWD resistivity measurements acquired in high-angle and horizontal wells.Several strategies are adopted in the inversion:(1)a one-dimensional(1D)simulator with a simplifi ed three-layered model guarantees the forward speed and keeps the number of inverted parameters as few as possible;(2)combined with geological and petrophysical bounds,the tool constraints derived from a detection capability analysis of LWD resistivity measurements are applied to scale down the inverted parameters’searching scope,which avoids meaningless solutions and accelerates the inversion signifi cantly;(3)multiple-initial guesses are used in the inversion to ensure a global solution.Inversion results over synthetic examples demonstrate that the proposed 1D inversion algorithm is well suited for complex formation structures.It is also robust and fast in extracting anisotropic resistivities from LWD resistivity measurements.
基金supported by the National Key Research and Development Program of China(2022YFF0800603).
文摘We conducted rapid inversions of rupture process for the 2023 earthquake doublet occurred in SE Türkiye,the first with a magnitude of M_(W)7.8 and the second with a magnitude of M_(W)7.6,using teleseismic and strong-motion data.The teleseismic rupture models of the both events were obtained approximately 88 and 55 minutes after their occurrences,respectively.The rupture models indicated that the first event was an asymmetric bilateral event with ruptures mainly propagating to the northeast,while the second one was a unilateral event with ruptures propagating to the west.This information could be useful in locating the meizoseismal areas.Compared with teleseismic models,the strong-motion models showed relatively higher resolution.A noticeable difference was found for the M_(W)7.6 earthquake,for which the strong-motion models shows a bilateral event,rather than a unilateral event,but the dominant rupture direction is still westward.Nevertheless,all strong-motion models are consistent with the teleseismic models in terms of magnitudes,durations,and dominant rupture directions.This suggests that both teleseismic and strong-motion data can be used for fast determination of major source characteristics.In contrast,the strong-motion data would be preferable in future emergency responses since they are recorded earlier and have a better resolution ability on the source ruptures.
基金Project supported by the National Natural Science Foundation of China (No.10172038)
文摘Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.
文摘In this paper,a time-frequency associated multiple signal classification(MUSIC)al-gorithm which is suitable for through-wall detection is proposed.The technology of detecting hu-man targets by through-wall radar can be used to monitor the status and the location information of human targets behind the wall.However,the detection is out of order when classical MUSIC al-gorithm is applied to estimate the direction of arrival.In order to solve the problem,a time-fre-quency associated MUSIC algorithm suitable for through-wall detection and based on S-band stepped frequency continuous wave(SFCW)radar is researched.By associating inverse fast Fouri-er transform(IFFT)algorithm with MUSIC algorithm,the power enhancement of the target sig-nal is completed according to the distance calculation results in the time domain.Then convert the signal to the frequency domain for direction of arrival(DOA)estimation.The simulations of two-dimensional human target detection in free space and the processing of measured data are com-pleted.By comparing the processing results of the two algorithms on the measured data,accuracy of DOA estimation of proposed algorithm is more than 75%,which is 50%higher than classical MUSIC algorithm.It is verified that the distance and angle of human target can be effectively de-tected via proposed algorithm.
基金Supported by the Natural Science Foundation of Jiangsu Province (No.BK2005409)the National 863 Program (No.2005AA123320).
文摘In this letter,P × N-pointIFFT is proposed to replace the N-point IFFT and analog fre-quency conversion in an Orthogonal Frequency Division Multiplexing (OFDM)-based Ultra-WideBand (UWB) system,and a new algorithm,named fast P × N-pointIFFT,is designed to reduce the com-plexity of the P × N-pointIFFT in the proposed scheme.
基金supported by NFS No.11001257,was stimulated by Per-Gunnar Martinsson’s paper”A Fast Direct Solver for a Class of Elliptic Partial Differential Equations”.Professor Jingfang Huang suggested solving the Poisson equation with variable coefficient as a test case.We are very grateful to both of them for their selfless help.
文摘We propose a direct solver for the three-dimensional Poisson equation with a variable coefficient,and an algorithm to directly solve the associated sparse linear systems that exploits the sparsity pattern of the coefficient matrix.Introducing some appropriate finite difference operators,we derive a second-order scheme for the solver,and then two suitable high-order compact schemes are also discussed.For a cube containing N nodes,the solver requires O(N^(3/2)log^(2)N)arithmetic operations and O(NlogN)memory to store the necessary information.Its efficiency is illustrated with examples,and the numerical results are analysed.
文摘This paper deals with a unified and novel approach for analyzing the frequency and time domain performance of grounding systems.The proposed procedure is based on solving the full set of Maxwell's equations in the frequency domain,and enables the exact computation of very near fields at the surface of the grounding grid,as well as far fields,by simple and accurate closed-form expressions for solving Sommerfeld integrals.In addition,the soil ionization is easily considered in the proposed method.The frequency domain responses are converted to the time domain by fast inverse Laplace transform.The results are validated and have shown acceptable accuracy.
基金supported by the National Natural Science Foundation of China under Grant No.61572491the 973 Program under Grant No.2011CB302401the open project of the SKLOIS in Institute of Information Engineering,Chinese Academy of Sciences under Grant No.2015-MS-03
文摘The trace inverse functions Tr(λx^(-1)) over the finite field F_(2~n) are a class of very important Boolean functions and are used in many stream ciphers such as SFINKS,RAKAPOSHI,the simple counter stream cipher(SCSC) presented by Si W and Ding C(2012),etc.In order to evaluate the security of those ciphers in resistance to(fast) algebraic attacks,the authors need to characterize algebraic properties of Tr(λx^(-1)).However,currently only some bounds on algebraic immunity of Tr(λx^(-1)) are given in the public literature,for example,the NGG upper bound and the Bayev lower bound,etc.This paper gives the exact value of the algebraic immunity of Tr(λx^(-1)) over F_(2~n),that is,AI(Tr(λx^(-1))) =[2n^(1/2)]- 2,where n ≥ 2,A ∈ F_(2~n) and λ≠ 0,which shows that Dalai's conjecture on the algebraic immunity of Tr(λx^(-1)) is correct.What is more,the authors demonstrate some weak properties of Tr(λx^(-1)) against fast algebraic attacks.
基金Paper supported by the Teaching and Research Award Programfor Outstanding Young Professor in High Education Institute, MOE,P.R.C.
文摘This paper proposes to use Fast Fourier Transform （ FFT ） / Inverse Fast Fourier Transform （IFFT）, instead of vector-matrix multiplication, to implement the spreading/despreoding in Carrier-Interferometry Orthogonal Frequency Division Multiplexing （ CI/OFDM） and Pseudo-Orthogonal Carrier lnterferometry OFDM （PO-CI/OFDM）. That can improve the signal processing efficiency of CI/OFDM and PO-CI/OFDM systems by about 2N/log2N and 2N/（ 1 ＋ log2 N） times respectively and dose not make any difference to the system function and performance. Moreover, the effi- ciency benefits will increase with the increase of the number of sub-carriers. In addition to that, we point out that the transmitter of CI/OFDM is actually technically equivalent to that of a single-carrier system with cyclic-prefix and the receiver of CI/OFDM is a typical OFDM receiver with CI despreading. Hence the low Peak-to-Average Power Ratio （PA- PR） property and high anti-fading performance of CI/OFDM system can be well explained .
