Based on waveform fitting,full waveform inversion(FWI)is an important inversion method with the ability to reconstruct multi-parameter models in high precision.However,the strong nonlinear equation used in FWI present...Based on waveform fitting,full waveform inversion(FWI)is an important inversion method with the ability to reconstruct multi-parameter models in high precision.However,the strong nonlinear equation used in FWI presents the following challenges,such as low convergence efficiency,high dependence on the initial model,and the energy imbalance in deep region of the inverted model.To solve these inherent problems,we develop a timedomain elastic FWI method based on gradient preconditioning with the following details:(1)the limited memory Broyden Fletcher Goldfarb Shanno method with faster convergence is adopted to im-prove the inversion stability;(2)a multi-scaled inversion strategy is used to alleviate the nonlinear inversion instead of falling into the local minimum;(3)in addition,the pseudo-Hessian preconditioned illumination operator is involved for preconditioning the parameter gradients to improve the illumination equilibrium degree of deep structures.Based on the programming implementation of the new method,a deep depression model with five diffractors is used for testing.Compared with the conventional elastic FWI method,the technique proposed by this study has better effectiveness and accuracy on the inversion effect and con-vergence,respectively.展开更多
肺部疾病是全球重要的公共卫生问题,其高发病率与死亡率凸显了早期诊断和精准评估的重要性^([1])。然而,现有诊断方法在全面评估肺部病变方面仍存在局限。传统肺功能检查(pulmonary function tests,PFTs)虽然无创便捷,但仅能提供整体肺...肺部疾病是全球重要的公共卫生问题,其高发病率与死亡率凸显了早期诊断和精准评估的重要性^([1])。然而,现有诊断方法在全面评估肺部病变方面仍存在局限。传统肺功能检查(pulmonary function tests,PFTs)虽然无创便捷,但仅能提供整体肺功能参数,难以反映肺部病变的区域异质性,且依赖于患者的良好配合。对于早期局灶性病变,由于肺组织的代偿作用,PFTs结果可能仍处于正常范围,从而延误了疾病的早期诊断和干预^([2])。高分辨率CT(high-resolution computed tomography,HRCT)是评估肺部结构的“金标准”,但电离辐射风险限制了其在儿童、孕妇及需长期随访的慢性肺病患者中的应用^([3])。展开更多
基金supported by the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(Grant No.2021QNLM020001)the National Key R&D Program of China(Grant No.2019YFC0605503C)+2 种基金the Major Scientific and Technological Projects of China National Petroleum Corporation(CNPC)(Grant No.ZD2019-183-003)the National Outstanding Youth Science Foundation(Grant No.41922028)the National Innovation Group Project(Grant No.41821002).
文摘Based on waveform fitting,full waveform inversion(FWI)is an important inversion method with the ability to reconstruct multi-parameter models in high precision.However,the strong nonlinear equation used in FWI presents the following challenges,such as low convergence efficiency,high dependence on the initial model,and the energy imbalance in deep region of the inverted model.To solve these inherent problems,we develop a timedomain elastic FWI method based on gradient preconditioning with the following details:(1)the limited memory Broyden Fletcher Goldfarb Shanno method with faster convergence is adopted to im-prove the inversion stability;(2)a multi-scaled inversion strategy is used to alleviate the nonlinear inversion instead of falling into the local minimum;(3)in addition,the pseudo-Hessian preconditioned illumination operator is involved for preconditioning the parameter gradients to improve the illumination equilibrium degree of deep structures.Based on the programming implementation of the new method,a deep depression model with five diffractors is used for testing.Compared with the conventional elastic FWI method,the technique proposed by this study has better effectiveness and accuracy on the inversion effect and con-vergence,respectively.
文摘肺部疾病是全球重要的公共卫生问题,其高发病率与死亡率凸显了早期诊断和精准评估的重要性^([1])。然而,现有诊断方法在全面评估肺部病变方面仍存在局限。传统肺功能检查(pulmonary function tests,PFTs)虽然无创便捷,但仅能提供整体肺功能参数,难以反映肺部病变的区域异质性,且依赖于患者的良好配合。对于早期局灶性病变,由于肺组织的代偿作用,PFTs结果可能仍处于正常范围,从而延误了疾病的早期诊断和干预^([2])。高分辨率CT(high-resolution computed tomography,HRCT)是评估肺部结构的“金标准”,但电离辐射风险限制了其在儿童、孕妇及需长期随访的慢性肺病患者中的应用^([3])。
