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Theoretical and numerical study on the coupling acoustic field of the plane p-wave to a cased borehole is carried out. The medium outside the cased borehole is modeled as the porous medium. The scattering field characteristics in the cased borehole are investigated when a plane fast p-wave is incident in tilt to the cased borehole from the porous medium. The scattering fields inside and outside the cased borehole are analyzed and deduced by Biot＇s theory under the boundary conditions on each interface, and they are numerically studied. It is found that the scattering field has strong resonant characteristics and there exists a series of resonant frequencies and peaks. The effects of the frequency, radii of each interface, incident angle, porosity, and other parameters on the resonant acoustic field have been investigated in detail in the fast and slow formations respectively. The resonant characteristics of the scattering field are also analyzed from the physical sense. 相似文献
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推导出氢原子基下径向矩阵元〈nl|rk|n′l′〉所满足的递推关系. 相似文献
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The conversion of energy between seismic and electromagnetic wave fields has been described by Pride’s coupled equations in porous media. In this paper, the seismoelectric field excited by the explosive point source located at the outside of the borehole is studied. The scattering fields inside and outside a borehole are analyzed and deduced under the boundary conditions at the interface between fluid and porous media. The influences of the distance of the point source, multipole components of the eccentric explosive source, and the receiving position along the axis of vertical borehole, on the converted waves inside the borehole are all investigated. When the distance from the acoustic source to the axis of a borehole is far enough, the longitudinal and coseismic longitudinal wave packets dominate the acoustic and electric field, respectively. The three components of both electric field and magnetic field can be detected, and the radial electric field is mainly excited and converted by the dipole component. Owing to the existence of borehole, the electric fields and magnetic fields in the borehole are azimuthal. The distance from the point where the maximum amplitude of the axial components of electric field is recorded, to the origin of coordinate indicates the horizontal distance from the explosive source to the axis of vertical borehole. 相似文献
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张清;张玉君;陶冶;胡冬梅;张超学 《影像科学与光化学》2025,(2):11-17+29
目的：本研究旨在探讨基于常规超声、剪切波弹性成像及超声造影等多模态超声参数,利用LASSO回归分析和Logistic回归构建预测甲状腺微小乳头状癌（PTMC）颈部中央区淋巴结转移（CLNM）的模型。方法：选取2022年6月至2024年6月期间收治的220例PTMC患者,根据术后病理结果分为CLNM组和非CLNM组,通过LASSO回归筛选出年龄、结节最大径、微钙化、被膜侵犯、增强均匀性和弹性评分6个关键因素,并构建预测模型。结果：该模型在预测CLNM时,AUC值达到0.825(95%CI:0.769～0.873),敏感度为81.10%,特异度为71.90%。结论：基于多模态超声特征构建的预测模型能有效预测PTMC患者的CLNM风险,为临床精准治疗方案的制定提供有力支持。 相似文献
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