The equivalence of geophysical fields, the finiteness of measurements and the measurement errors make the result of geophysical inversion non-unique. For example, the measurements and inversion method used, the priori...The equivalence of geophysical fields, the finiteness of measurements and the measurement errors make the result of geophysical inversion non-unique. For example, the measurements and inversion method used, the priori rupture model determined and the slip distribution smoothing factor selected will have significant influences on the earthquake rupture slip distribution. Using different data and methods, different authors have given different rupture slip distribution models of the 2015 Mw7.9 Nepal earth- quake, with the maximum slip ranging from 3.0 m to 6.8 m. In this paper, geometry parameters of the single rectangular fault model in elastic half-space were inferred constraining with the Global Posi- tioning System （GPS） and Interferometric Synthetic Aperture Radar （InSAR） coseismic deformations and bounding the slip with approximate average value; and then, the single rectangular fault was divided into multiple sub-faults, and the final slip smoothing factor, the final slip distribution and the maximum slip were determined with the misfit-roughness tradeoff curve, the cross-validation sum of squares （CVSS） and the third-party observation data or indexes being comprehensively taken into account. The results show that, the rupture of the Nepal earthquake extended by over 100 km east by south. The maximum slip of the earthquake was about 6.5-6.7 m, and most of the slip is confined at depths of 8 -20 kin, consistent with the depth distribution of aftershocks. The method for reducing the multiplicity of solutions to rupture slip distribution in this paper was ever used in inversion of rupture slip distri- bution for the 2008 Wenchuan and 2013 Lushan earthquakes, and the third-party measurement - surface dislocation has very large effect on reducing the multiplicity of solutions to inversion of the Wenchuan earthquake. Other priori information or indicators, such as fault strike, dip, earthquake magnitude, seismic activity, Coulomb stress, and seismic period, can be used for beneficial validation of and comparison with inversion results.展开更多
Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this cha...Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.展开更多
Precise welding of the T-joints between aircraft hyperbolic panels and stringers is required. Therefore, a method of solving inverse kinematics equations for a cooperative welding robot with multiple manipulators base...Precise welding of the T-joints between aircraft hyperbolic panels and stringers is required. Therefore, a method of solving inverse kinematics equations for a cooperative welding robot with multiple manipulators based on neural networks was investigated. To build an effective Denavit-Hartenberg(DH)model for this robot, sample data was obtained considering the movement ranges of the robot joints.Based on back propagation(BP) and radial basis function(RBF) neural networks, 18 joint sub-spaces were mapped to the workspaces of three manipulators. The high-dimensional and nonlinear inverse kinematics problem was transformed into a multi-input and multi-output prediction model. The results revealed that the prediction model of solving the cooperative welding robot kinematics equations was quite accurate. Moreover, compared with the BP-based model, the calculation process of the RBF-based prediction model was slower, but yielded more accurate predictions.展开更多
Based on surfaced-related multiple elimination （SRME） , this research has derived the methods on multiples elimination in the inverse data space. Inverse data processing means moving seismic data from forwar...Based on surfaced-related multiple elimination （SRME） , this research has derived the methods on multiples elimination in the inverse data space. Inverse data processing means moving seismic data from forward data space （FDS） to inverse data space （ IDS） . The surface-related multiples and primaries can then be sepa-rated in the IDS, since surface-related multiples wi l l form a focus region in the IDS. Muting the multiples ener-gy can achieve the purpose of multiples elimination and avoid the damage to primaries energy during the process of adaptive subtraction. Randomized singular value decomposition （ RSYD） is used to enhance calculation speed and improve the accuracy in the conversion of FDS to IDS. The synthetic shot record of the salt dome model shows that the relationship between primaries and multiples is simple and clear, and RSVD can easily eliminate multiples and save primaries energy. Compared with conventional multiples elimination methods and ordinary methods of multiples elimination in the inverse data space, this technique has an advantage of high cal-culation speed and reliable outcomes.展开更多
A Hauser-Ernst-type extended hyperbolic complex linear system given in our previous paper [Gao Y J 2004 Chin. Phys. 13 602] is slightly modified and used to develop a new inverse scattering method for the stationary a...A Hauser-Ernst-type extended hyperbolic complex linear system given in our previous paper [Gao Y J 2004 Chin. Phys. 13 602] is slightly modified and used to develop a new inverse scattering method for the stationary axisymmetric Einstein-Maxwell theory with multiple Abelian gauge fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the inverse scattering method be fine and effective in practical application. As an example, a concrete family of soliton solutions for the considered theory is obtained.展开更多
In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration.First,based on an inputted prestack time migration profile,the method predicts the prestack ti...This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration.First,based on an inputted prestack time migration profile,the method predicts the prestack time migration profile that only includes internal multiples by inverse scattering series method.Second,the method uses velocity-weighted Kirchhoff demigration to create shot gathers that contains only internal multiples.Internal multiple prediction based on the prestack time migration profile effectively reduces the computational cost of multiple predictions,and the internal-multiple shot gathers created by Kirchhoff demigration remarkably reduces the complexity of the practical problem.Internal multiple elimination can be conducted through the combined adaptive multiple subtraction based on event tracing.Synthetic and field data tests show that the method effectively predicts internal multiples and possesses considerable potential in field data processing,particularly in areas where internal multiples develop seriously.展开更多
We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are dis...We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are discussed,followed by the derivation of the attenuation and phase-shift geometrical factors to illustrate the relative contributions of formation units to the observed signals.Then,a new definition of detection depth,which considers the uncertainty of inversion results caused by the data noise,is proposed to quantify the detection capability of ED ARM.Finally,the B ayesian theory associated with Markov chain Monte Carlo sampling is introduced for fast processing of EDARM data.Numerical results show that ED ARM is capable of detecting the azimuth and distance of remote bed boundaries,and the detection capability increases with increasing spacing and resistivity contrast.The EDARM tool can accommodate a large range of formation resistivity and is able to provide the resistivity anisotropy at arbitrary relative dipping angles.In addition,multiple bed boundaries and reservoir images near the borehole are readily obtained by using the Bayesian inversion.展开更多
Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence...Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence angles, and elastic parameters on either side of the interface, which means that wave-propagation effects, such as spherical spreading, attenuation, transmission loss, multiples, and event mismatching of P-and S-waves, are not considered and cannot accurately describe the true propagation characteristics of seismic waves. Conventional AVA inversion methods require that these wave-propagation effects have been fully corrected or attenuated before inversion but these requirements can hardly be satisfied in practice. Using a one-dimensional(1 D) earth model, the reflectivity method can simulate the full wavefield response of seismic waves. Therefore, we propose a nonlinear multicomponent prestack AVA joint inversion method based on the vectorized reflectivity method, which uses a fast nondominated sorting genetic algorithm(NSGA II) to optimize the nonlinear multiobjective function to estimate multiple parameters, such as P-wave velocity, S-wave velocity, and density. This approach is robust because it can simultaneously cope with more than one objective function without introducing weight coefficients. Model tests prove the effectiveness of the proposed inversion method. Based on the inversion results, we find that the nonlinear prestack AVA joint inversion using the reflectivity method yields more accurate inversion results than the inversion by using the exact Zoeppritz equation when the wave-propagation effects of transmission loss and internal multiples are not completely corrected.展开更多
As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to intr...As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to introduce a new rock skeleton parameter which is the dry-rock VP/VS ratio squared(DVRS).In the process of fluid factor calculation or inversion,the existing methods take this parameter as a static constant,which has been estimated in advance,and then apply it to the fluid factor calculation and inversion.The fluid identification analysis based on a portion of the Marmousi 2 model and numerical forward modeling test show that,taking the DVRS as a static constant will limit the identification ability of fluid factor and reduce the inversion accuracy.To solve the above problems,we proposed a new method to regard the DVRS as a dynamic variable varying with depth and lithology for the first time,then apply it to fluid factor calculation and inversion.Firstly,the exact Zoeppritz equations are rewritten into a new form containing the fluid factor and DVRS of upper and lower layers.Next,the new equations are applied to the four parameters simultaneous inversion based on the generalized nonlinear inversion(GNI)method.The testing results on a portion of the Marmousi 2 model and field data show that dynamic DVRS can significantly improve the fluid factor identification ability,effectively suppress illusion.Both synthetic and filed data tests also demonstrate that the GNI method based on Bayesian deterministic inversion(BDI)theory can successfully solve the above four parameter simultaneous inversion problem,and taking the dynamic DVRS as a target inversion parameter can effectively improve the inversion accuracy of fluid factor.All these results completely verified the feasibility and effectiveness of the proposed method.展开更多
Aimed at the serious mismatch between the synthetic seismogram and the real data of the Sinian Dengying Formation and the Lower Cambrian Qiongzhusi Formation in the GS1 well area, Sichuan Basin, four aspects of intern...Aimed at the serious mismatch between the synthetic seismogram and the real data of the Sinian Dengying Formation and the Lower Cambrian Qiongzhusi Formation in the GS1 well area, Sichuan Basin, four aspects of internal multiples identification and suppression were studied. Firstly, a forward modeling method of internal multiple based on reflectivity method was developed. Through eight means such as post-stack and pre-stack forward modeling of internal multiple, and combined with VSP data, it was demonstrated that well-seismic mismatching in this area is mainly caused by the internal multiples. Secondly, the simulation results of internal multiple forward modeling using the stripping method combined with the internal multiple periodicity analysis showed that four groups of overburden layers with velocity inversion were the main sources of the internal multiples. Thirdly, by identifying internal multiples accurately and using suppression technology based on pattern recognition, an effective and replicable suppression scheme suitable for these formations was established, overcoming the difficulty of the small speed difference between internal multiple and primary reflection wave which makes the current methods ineffective. Fourthly, an evaluation index of internal multiple intensity was proposed, and the internal multiple intensity distribution diagram of the fourth member of Dengying Formation(Deng-4 Member) in Gaoshiti-Moxi area was compiled. This scheme greatly improved the well-seismic match, and the strata sedimentary features are clearer on the new seismic profiles with higher lateral resolution, with which smaller faults and geological anomalies can be identified and a series of the bead reflections in the Dengying Formation are first discovered. The coincidence rate of reservoir prediction based on seismic waveform classification was increased from 60% to 90%, and that of hydrocarbon detection based on dual phase medium theory was increased from 70% to 100%.展开更多
Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite ...Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite fields. The constructions can be implemented fast since multiplicative inverse over finite fields can be computed in polynomial time.展开更多
In certain computational systems the amount of space required to execute an algorithm is even more restrictive than the corresponding time necessary for solution of a problem. In this paper an algorithm for modular mu...In certain computational systems the amount of space required to execute an algorithm is even more restrictive than the corresponding time necessary for solution of a problem. In this paper an algorithm for modular multiplicative inverse is introduced and its computational space complexity is analyzed. A tight upper bound for bit storage required for execution of the algorithm is provided. It is demonstrated that for range of numbers used in public-key encryption systems, the size of bit storage does not exceed a 2K-bit threshold in the worst-case. This feature of the Enhanced-Euclid algorithm allows designing special-purpose hardware for its implementation as a subroutine in communication-secure wireless devices.展开更多
The high resolution 3D nonlinear integrated inversion method is based on nonlinear theory. Under layer control, the log data from several wells （or all wells） in the study area and seismic trace data adjacent to the...The high resolution 3D nonlinear integrated inversion method is based on nonlinear theory. Under layer control, the log data from several wells （or all wells） in the study area and seismic trace data adjacent to the wells are input to a network with multiple inputs and outputs and are integratedly trained to obtain an adaptive weight function of the entire study area. Integrated nonlinear mapping relationships are built and updated by the lateral and vertical geologic variations of the reservoirs. Therefore, the inversion process and its inversion results can be constrained and controlled and a stable seismic inversion section with high resolution with velocity inversion, impedance inversion, and density inversion sections, can be gained. Good geologic effects have been obtained in model computation tests and real data processing, which verified that this method has high precision, good practicality, and can be used for quantitative reservoir analysis.展开更多
Numerous cryptographic algorithms (ElGamal, Rabin, RSA, NTRU etc) require multiple computations of modulo multiplicative inverses. This paper describes and validates a new algorithm, called the Enhanced Euclid Algorit...Numerous cryptographic algorithms (ElGamal, Rabin, RSA, NTRU etc) require multiple computations of modulo multiplicative inverses. This paper describes and validates a new algorithm, called the Enhanced Euclid Algorithm, for modular multiplicative inverse (MMI). Analysis of the proposed algorithm shows that it is more efficient than the Extended Euclid algorithm (XEA). In addition, if a MMI does not exist, then it is not necessary to use the Backtracking procedure in the proposed algorithm;this case requires fewer operations on every step (divisions, multiplications, additions, assignments and push operations on stack), than the XEA. Overall, XEA uses more multiplications, additions, assignments and twice as many variables than the proposed algorithm.展开更多
Dear Editor,For virologists,it is crucial to confidently determine the concentration of infectious particles that are utilized and produced in experiments（Dulbecco,1952;Bushar and Sagripanti,1990;La Barre and Lowy,20...Dear Editor,For virologists,it is crucial to confidently determine the concentration of infectious particles that are utilized and produced in experiments（Dulbecco,1952;Bushar and Sagripanti,1990;La Barre and Lowy,2001;Gueret et al.,2002;Gao et al.,2009;Kutner et al.,2009;Grigorov et al.,2011.展开更多
Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated ...Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated and observed wave-form using the sparse constraint of primary impulse responses to predict multiples and remove them directly,instead of using the conventional adaptive subtraction method.Even though the generalized EPSI method provides a good estimate of the primaries and multiples when they overlap,it is limited by intensive computational cost.In this paper,we introduce two strategies to improve computational efficiency.First,the interface-controlled strategy is introduced by only selecting high-amplitude primary responses related to the interfaces with strong impedance contrasts to estimate multiples.The computational time is approximately proportional to the number of involved reflectors and usually,most of the internal multiple energy in the data is only related to a few strong reflectors.Therefore the modified method can remove most of the internal multiples in fewer computations than in the generalized EPSI,which loops through all the interfaces.Next,an approximate formula for estimating primary impulse responses is proposed by neglecting a computationally intensive term which corresponds to the primary responses estimated from internal multiples.According to our analyses and experiments,in most cases,the contribution of this term is negligible because the internal multiples are weak.Therefore,the computational efficiency can be improved without significantly losing quality when estimating most primaries and multiples.In order to demonstrate this,multiple elimination of a two-layered simple data and the Pluto data are implemented.We find that the modified method can yield reliable results that require fewer computations.The improvements of the modified method may encourage the use of the generalized EPSI method in industry.展开更多
为使对换流阀工作状态的控制更加精确、抑制换相失败,提出了一种基于多分支多输入多输出(Multiple input multiple output,MIMO)深度学习的高压直流输电(Line commutated converter high voltage direct current,LCC-HVDC)换流器阀电流...为使对换流阀工作状态的控制更加精确、抑制换相失败,提出了一种基于多分支多输入多输出(Multiple input multiple output,MIMO)深度学习的高压直流输电(Line commutated converter high voltage direct current,LCC-HVDC)换流器阀电流波形反演方案。对现行实际工程中常用的基于差流换相失败的检测方案进行仿真分析,发现检测结果存在滞后性。阀电流波形的反演模型,其输入特征量为三相交流电流、输出量为6个阀电流,属于MIMO的场景。为提取更多特征信息,基于Inception-ResNet结构、采用多种不同尺寸的卷积,设计多分支MIMO深度学习的换流器阀电流反演模型,并以三相电流作为模型输入,6个阀电流作为输出量,对多分支MIMO模型进行训练。最后,对阀电流的波形进行预测反演。仿真结果表明,多分支MIMO模型对阀电流波形的反演具有较好的适用性,反演结果的相关系数在0.9836以上、平均绝对误差在0.1284以下、且均方误差在0.0286以内,误差变化程度较低。展开更多
Radon变换反演分辨率是其在地震资料处理中应用的关键因素.常规高分辨率Radon变换反演模型采用L_(1)范数实现稀疏正则化,其以Radon系数振幅总体大小衡量稀疏性,未能充分考虑到Radon系数振幅相对强弱,以此构建的反演方法旨在通过衰减弱...Radon变换反演分辨率是其在地震资料处理中应用的关键因素.常规高分辨率Radon变换反演模型采用L_(1)范数实现稀疏正则化,其以Radon系数振幅总体大小衡量稀疏性,未能充分考虑到Radon系数振幅相对强弱,以此构建的反演方法旨在通过衰减弱振幅来提高稀疏性,对Radon系数分辨率提高效果有限.本文提出一种以信号振幅相对大小衡量Radon系数稀疏性的尺度不变稀疏度量(Scale-Invariant Sparsity Measure,SSM)函数,并以L_(1)/L_(2)范数作为其光滑近似.针对L_(1)/L_(2)正则化的非线性,改进交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)对其求解.合成数据与实际地震资料处理结果表明,该方法能够增强一次波与多次波在Radon域的分辨率,降低Radon变换的能量扩散,提高多次波压制效果;同时该方法能够较好地压制随机噪声,方法具有一定的稳健性.展开更多
基金supported by the Director Foundation of Institute of Seismology,China Earthquake Adminstration(IS201506220)the National Natural Science Foundation of China(40974012,41304019)the Special Foundation for Seismic Research(201208006)
文摘The equivalence of geophysical fields, the finiteness of measurements and the measurement errors make the result of geophysical inversion non-unique. For example, the measurements and inversion method used, the priori rupture model determined and the slip distribution smoothing factor selected will have significant influences on the earthquake rupture slip distribution. Using different data and methods, different authors have given different rupture slip distribution models of the 2015 Mw7.9 Nepal earth- quake, with the maximum slip ranging from 3.0 m to 6.8 m. In this paper, geometry parameters of the single rectangular fault model in elastic half-space were inferred constraining with the Global Posi- tioning System （GPS） and Interferometric Synthetic Aperture Radar （InSAR） coseismic deformations and bounding the slip with approximate average value; and then, the single rectangular fault was divided into multiple sub-faults, and the final slip smoothing factor, the final slip distribution and the maximum slip were determined with the misfit-roughness tradeoff curve, the cross-validation sum of squares （CVSS） and the third-party observation data or indexes being comprehensively taken into account. The results show that, the rupture of the Nepal earthquake extended by over 100 km east by south. The maximum slip of the earthquake was about 6.5-6.7 m, and most of the slip is confined at depths of 8 -20 kin, consistent with the depth distribution of aftershocks. The method for reducing the multiplicity of solutions to rupture slip distribution in this paper was ever used in inversion of rupture slip distri- bution for the 2008 Wenchuan and 2013 Lushan earthquakes, and the third-party measurement - surface dislocation has very large effect on reducing the multiplicity of solutions to inversion of the Wenchuan earthquake. Other priori information or indicators, such as fault strike, dip, earthquake magnitude, seismic activity, Coulomb stress, and seismic period, can be used for beneficial validation of and comparison with inversion results.
基金funded by the National Key R&D Program of China(Grant No.2022YFC2903904)the National Natural Science Foundation of China(Grant Nos.51904057 and U1906208).
文摘Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.
基金supported by National Key R&D Program of China (2017YFB1301600)。
文摘Precise welding of the T-joints between aircraft hyperbolic panels and stringers is required. Therefore, a method of solving inverse kinematics equations for a cooperative welding robot with multiple manipulators based on neural networks was investigated. To build an effective Denavit-Hartenberg(DH)model for this robot, sample data was obtained considering the movement ranges of the robot joints.Based on back propagation(BP) and radial basis function(RBF) neural networks, 18 joint sub-spaces were mapped to the workspaces of three manipulators. The high-dimensional and nonlinear inverse kinematics problem was transformed into a multi-input and multi-output prediction model. The results revealed that the prediction model of solving the cooperative welding robot kinematics equations was quite accurate. Moreover, compared with the BP-based model, the calculation process of the RBF-based prediction model was slower, but yielded more accurate predictions.
文摘Based on surfaced-related multiple elimination （SRME） , this research has derived the methods on multiples elimination in the inverse data space. Inverse data processing means moving seismic data from forward data space （FDS） to inverse data space （ IDS） . The surface-related multiples and primaries can then be sepa-rated in the IDS, since surface-related multiples wi l l form a focus region in the IDS. Muting the multiples ener-gy can achieve the purpose of multiples elimination and avoid the damage to primaries energy during the process of adaptive subtraction. Randomized singular value decomposition （ RSYD） is used to enhance calculation speed and improve the accuracy in the conversion of FDS to IDS. The synthetic shot record of the salt dome model shows that the relationship between primaries and multiples is simple and clear, and RSVD can easily eliminate multiples and save primaries energy. Compared with conventional multiples elimination methods and ordinary methods of multiples elimination in the inverse data space, this technique has an advantage of high cal-culation speed and reliable outcomes.
基金Project supported by the National Natural Science Foundation of China (Grant No 10475036)
文摘A Hauser-Ernst-type extended hyperbolic complex linear system given in our previous paper [Gao Y J 2004 Chin. Phys. 13 602] is slightly modified and used to develop a new inverse scattering method for the stationary axisymmetric Einstein-Maxwell theory with multiple Abelian gauge fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the inverse scattering method be fine and effective in practical application. As an example, a concrete family of soliton solutions for the considered theory is obtained.
文摘In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
基金support of the NSFC-Shandong Joint Fund for Marine Science Research Centers (No. U1606401)the National Natural Science Foundation of China (Nos. 41704114 and 41574105)+3 种基金the National Science and Technology Major Project of China (No. 2016Z X05027-002)the Scientific and Technological Innovation Project financially supported by Qingdao National Laboratory for Marine Science and Technology (No. 2016 ASKJ13)Taishan Scholar Project Funding (No. tspd2016 1007)the Latitudinal Project of Algorithm Research of Internal Multiple Prediction financially supported by CNOOC
文摘This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration.First,based on an inputted prestack time migration profile,the method predicts the prestack time migration profile that only includes internal multiples by inverse scattering series method.Second,the method uses velocity-weighted Kirchhoff demigration to create shot gathers that contains only internal multiples.Internal multiple prediction based on the prestack time migration profile effectively reduces the computational cost of multiple predictions,and the internal-multiple shot gathers created by Kirchhoff demigration remarkably reduces the complexity of the practical problem.Internal multiple elimination can be conducted through the combined adaptive multiple subtraction based on event tracing.Synthetic and field data tests show that the method effectively predicts internal multiples and possesses considerable potential in field data processing,particularly in areas where internal multiples develop seriously.
基金co-funded by Chinese Postdoctoral Science Foundation(2018M640663)the National Natural Science Foundation of China(41474100,41574118,41674131)National Science and Technology Major Project of the Ministry of Science and Technology of China(2017ZX05009-001)
文摘We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are discussed,followed by the derivation of the attenuation and phase-shift geometrical factors to illustrate the relative contributions of formation units to the observed signals.Then,a new definition of detection depth,which considers the uncertainty of inversion results caused by the data noise,is proposed to quantify the detection capability of ED ARM.Finally,the B ayesian theory associated with Markov chain Monte Carlo sampling is introduced for fast processing of EDARM data.Numerical results show that ED ARM is capable of detecting the azimuth and distance of remote bed boundaries,and the detection capability increases with increasing spacing and resistivity contrast.The EDARM tool can accommodate a large range of formation resistivity and is able to provide the resistivity anisotropy at arbitrary relative dipping angles.In addition,multiple bed boundaries and reservoir images near the borehole are readily obtained by using the Bayesian inversion.
基金supported by the National Science and Technology Major Project(No.2016ZX05003-003)
文摘Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence angles, and elastic parameters on either side of the interface, which means that wave-propagation effects, such as spherical spreading, attenuation, transmission loss, multiples, and event mismatching of P-and S-waves, are not considered and cannot accurately describe the true propagation characteristics of seismic waves. Conventional AVA inversion methods require that these wave-propagation effects have been fully corrected or attenuated before inversion but these requirements can hardly be satisfied in practice. Using a one-dimensional(1 D) earth model, the reflectivity method can simulate the full wavefield response of seismic waves. Therefore, we propose a nonlinear multicomponent prestack AVA joint inversion method based on the vectorized reflectivity method, which uses a fast nondominated sorting genetic algorithm(NSGA II) to optimize the nonlinear multiobjective function to estimate multiple parameters, such as P-wave velocity, S-wave velocity, and density. This approach is robust because it can simultaneously cope with more than one objective function without introducing weight coefficients. Model tests prove the effectiveness of the proposed inversion method. Based on the inversion results, we find that the nonlinear prestack AVA joint inversion using the reflectivity method yields more accurate inversion results than the inversion by using the exact Zoeppritz equation when the wave-propagation effects of transmission loss and internal multiples are not completely corrected.
基金the National Natural Science Foundation of China(41904116,41874156,42074167 and 42204135)the Natural Science Foundation of Hunan Province(2020JJ5168)the China Postdoctoral Science Foundation(2021M703629)for their funding of this research.
文摘As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to introduce a new rock skeleton parameter which is the dry-rock VP/VS ratio squared(DVRS).In the process of fluid factor calculation or inversion,the existing methods take this parameter as a static constant,which has been estimated in advance,and then apply it to the fluid factor calculation and inversion.The fluid identification analysis based on a portion of the Marmousi 2 model and numerical forward modeling test show that,taking the DVRS as a static constant will limit the identification ability of fluid factor and reduce the inversion accuracy.To solve the above problems,we proposed a new method to regard the DVRS as a dynamic variable varying with depth and lithology for the first time,then apply it to fluid factor calculation and inversion.Firstly,the exact Zoeppritz equations are rewritten into a new form containing the fluid factor and DVRS of upper and lower layers.Next,the new equations are applied to the four parameters simultaneous inversion based on the generalized nonlinear inversion(GNI)method.The testing results on a portion of the Marmousi 2 model and field data show that dynamic DVRS can significantly improve the fluid factor identification ability,effectively suppress illusion.Both synthetic and filed data tests also demonstrate that the GNI method based on Bayesian deterministic inversion(BDI)theory can successfully solve the above four parameter simultaneous inversion problem,and taking the dynamic DVRS as a target inversion parameter can effectively improve the inversion accuracy of fluid factor.All these results completely verified the feasibility and effectiveness of the proposed method.
基金Supported by the CNPC Geophysical Major Technology Field Examination and Integrated Support Project(2017D-3503)Scientific Research and Technological Development Project of PetroChina Company Ltd.(kt2018-10-02)
文摘Aimed at the serious mismatch between the synthetic seismogram and the real data of the Sinian Dengying Formation and the Lower Cambrian Qiongzhusi Formation in the GS1 well area, Sichuan Basin, four aspects of internal multiples identification and suppression were studied. Firstly, a forward modeling method of internal multiple based on reflectivity method was developed. Through eight means such as post-stack and pre-stack forward modeling of internal multiple, and combined with VSP data, it was demonstrated that well-seismic mismatching in this area is mainly caused by the internal multiples. Secondly, the simulation results of internal multiple forward modeling using the stripping method combined with the internal multiple periodicity analysis showed that four groups of overburden layers with velocity inversion were the main sources of the internal multiples. Thirdly, by identifying internal multiples accurately and using suppression technology based on pattern recognition, an effective and replicable suppression scheme suitable for these formations was established, overcoming the difficulty of the small speed difference between internal multiple and primary reflection wave which makes the current methods ineffective. Fourthly, an evaluation index of internal multiple intensity was proposed, and the internal multiple intensity distribution diagram of the fourth member of Dengying Formation(Deng-4 Member) in Gaoshiti-Moxi area was compiled. This scheme greatly improved the well-seismic match, and the strata sedimentary features are clearer on the new seismic profiles with higher lateral resolution, with which smaller faults and geological anomalies can be identified and a series of the bead reflections in the Dengying Formation are first discovered. The coincidence rate of reservoir prediction based on seismic waveform classification was increased from 60% to 90%, and that of hydrocarbon detection based on dual phase medium theory was increased from 70% to 100%.
基金Supported by the Open Funds of Key Lab of Fujian Province University Network Security and Cryptology (07B005)the Funds of the Education Department of Fujian Province (JA07164)the Natural Science Foundation of Fujian Province of China (2007F3086)
文摘Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite fields. The constructions can be implemented fast since multiplicative inverse over finite fields can be computed in polynomial time.
文摘In certain computational systems the amount of space required to execute an algorithm is even more restrictive than the corresponding time necessary for solution of a problem. In this paper an algorithm for modular multiplicative inverse is introduced and its computational space complexity is analyzed. A tight upper bound for bit storage required for execution of the algorithm is provided. It is demonstrated that for range of numbers used in public-key encryption systems, the size of bit storage does not exceed a 2K-bit threshold in the worst-case. This feature of the Enhanced-Euclid algorithm allows designing special-purpose hardware for its implementation as a subroutine in communication-secure wireless devices.
基金supported by the Key Project of the National Natural Scientific Foundation(Grant No.40839909)
文摘The high resolution 3D nonlinear integrated inversion method is based on nonlinear theory. Under layer control, the log data from several wells （or all wells） in the study area and seismic trace data adjacent to the wells are input to a network with multiple inputs and outputs and are integratedly trained to obtain an adaptive weight function of the entire study area. Integrated nonlinear mapping relationships are built and updated by the lateral and vertical geologic variations of the reservoirs. Therefore, the inversion process and its inversion results can be constrained and controlled and a stable seismic inversion section with high resolution with velocity inversion, impedance inversion, and density inversion sections, can be gained. Good geologic effects have been obtained in model computation tests and real data processing, which verified that this method has high precision, good practicality, and can be used for quantitative reservoir analysis.
文摘Numerous cryptographic algorithms (ElGamal, Rabin, RSA, NTRU etc) require multiple computations of modulo multiplicative inverses. This paper describes and validates a new algorithm, called the Enhanced Euclid Algorithm, for modular multiplicative inverse (MMI). Analysis of the proposed algorithm shows that it is more efficient than the Extended Euclid algorithm (XEA). In addition, if a MMI does not exist, then it is not necessary to use the Backtracking procedure in the proposed algorithm;this case requires fewer operations on every step (divisions, multiplications, additions, assignments and push operations on stack), than the XEA. Overall, XEA uses more multiplications, additions, assignments and twice as many variables than the proposed algorithm.
基金supported in part by NIH Research Grant R01NS081109 to SVHthe content is solely the responsibility of the authors and does not necessarily represent the official views of the NINDS/NIHappreciate the assistance of the editorial staff at UMES
文摘Dear Editor,For virologists,it is crucial to confidently determine the concentration of infectious particles that are utilized and produced in experiments（Dulbecco,1952;Bushar and Sagripanti,1990;La Barre and Lowy,2001;Gueret et al.,2002;Gao et al.,2009;Kutner et al.,2009;Grigorov et al.,2011.
基金supported by the National Natural Science Foundation of China(Grant Nos.41704061,41730425)the National Major Project of China(Grant No.2017ZX05008-007)the Seismometry Talent Training Project of the China Earthquake Administration(Grant No.CEA-JC/QNCZ-18322).
文摘Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated and observed wave-form using the sparse constraint of primary impulse responses to predict multiples and remove them directly,instead of using the conventional adaptive subtraction method.Even though the generalized EPSI method provides a good estimate of the primaries and multiples when they overlap,it is limited by intensive computational cost.In this paper,we introduce two strategies to improve computational efficiency.First,the interface-controlled strategy is introduced by only selecting high-amplitude primary responses related to the interfaces with strong impedance contrasts to estimate multiples.The computational time is approximately proportional to the number of involved reflectors and usually,most of the internal multiple energy in the data is only related to a few strong reflectors.Therefore the modified method can remove most of the internal multiples in fewer computations than in the generalized EPSI,which loops through all the interfaces.Next,an approximate formula for estimating primary impulse responses is proposed by neglecting a computationally intensive term which corresponds to the primary responses estimated from internal multiples.According to our analyses and experiments,in most cases,the contribution of this term is negligible because the internal multiples are weak.Therefore,the computational efficiency can be improved without significantly losing quality when estimating most primaries and multiples.In order to demonstrate this,multiple elimination of a two-layered simple data and the Pluto data are implemented.We find that the modified method can yield reliable results that require fewer computations.The improvements of the modified method may encourage the use of the generalized EPSI method in industry.
文摘为使对换流阀工作状态的控制更加精确、抑制换相失败,提出了一种基于多分支多输入多输出(Multiple input multiple output,MIMO)深度学习的高压直流输电(Line commutated converter high voltage direct current,LCC-HVDC)换流器阀电流波形反演方案。对现行实际工程中常用的基于差流换相失败的检测方案进行仿真分析,发现检测结果存在滞后性。阀电流波形的反演模型,其输入特征量为三相交流电流、输出量为6个阀电流,属于MIMO的场景。为提取更多特征信息,基于Inception-ResNet结构、采用多种不同尺寸的卷积,设计多分支MIMO深度学习的换流器阀电流反演模型,并以三相电流作为模型输入,6个阀电流作为输出量,对多分支MIMO模型进行训练。最后,对阀电流的波形进行预测反演。仿真结果表明,多分支MIMO模型对阀电流波形的反演具有较好的适用性,反演结果的相关系数在0.9836以上、平均绝对误差在0.1284以下、且均方误差在0.0286以内,误差变化程度较低。
文摘Radon变换反演分辨率是其在地震资料处理中应用的关键因素.常规高分辨率Radon变换反演模型采用L_(1)范数实现稀疏正则化,其以Radon系数振幅总体大小衡量稀疏性,未能充分考虑到Radon系数振幅相对强弱,以此构建的反演方法旨在通过衰减弱振幅来提高稀疏性,对Radon系数分辨率提高效果有限.本文提出一种以信号振幅相对大小衡量Radon系数稀疏性的尺度不变稀疏度量(Scale-Invariant Sparsity Measure,SSM)函数,并以L_(1)/L_(2)范数作为其光滑近似.针对L_(1)/L_(2)正则化的非线性,改进交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)对其求解.合成数据与实际地震资料处理结果表明,该方法能够增强一次波与多次波在Radon域的分辨率,降低Radon变换的能量扩散,提高多次波压制效果;同时该方法能够较好地压制随机噪声,方法具有一定的稳健性.
