53 results on '"Lee, Vincent W."'
Search Results
2. Promotion of β-catenin/Foxo1 signaling ameliorates renal interstitial fibrosis.
- Author
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Rao, Padmashree, Pang, Min, Qiao, Xi, Yu, Hong, Wang, Hailong, Yang, Ying, Ren, Xiaojun, Hu, Min, Chen, Titi, Cao, Qi, Wang, Yiping, Khushi, Matloob, Zhang, Geoff, Wang, Yuan Min, Heok P'ng, Chow, Nankivell, Brian, Lee, Vincent W., Alexander, Stephen I., Zheng, Guoping, and Harris, David C.
- Published
- 2019
- Full Text
- View/download PDF
3. In-plane soil-structure interaction excited by incident plane P waves.
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Cai, Yiwei, Lee, Vincent W., and Trifunac, Mihailo D.
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SOIL structure , *SOIL mechanics , *P-waves (Seismology) , *SOIL classification , *ROCK mechanics - Abstract
Abstract The subject of in-plane soil-structure interaction of a shear wall on a rigid circular foundation embedded in a linear elastic half-space under an incident plane P wave is revisited. It is known that satisfying the zero stress condition on the ground surface has been the major obstacle when developing an analytic solution of this model. Early solution procedures approximated the ground surface by the surface of a large cylinder. In this paper, two sets of closed-form solutions are derived based on the new approaches: one approach neglects the boundary conditions on the ground surface, while the other includes all boundary conditions by means of the weighted residue method. The objective of this work is to study the relative importance of these boundary conditions and evaluate the results generated from these two solution procedures. Foundation and building responses, as well as surface displacement and stress are compared for the two solutions and to previously published approximate solutions. Highlights • Dynamic soil-structure interaction in homogeneous half-space. • Shear beam building on semi-cylindrical foundation. • In-plane excitation by plane P waves. • Significance of surface boundary conditions on amplitudes of scattered waves. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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4. In-plane soil-structure interaction excited by incident plane SV waves.
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Cai, Yiwei, Lee, Vincent W., and Trifunac, Mihailo D.
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SOIL structure , *STRUCTURAL dynamics , *DEFORMATIONS (Mechanics) , *BOUNDARY value problems , *STRAINS & stresses (Mechanics) , *STATICS - Abstract
In-plane soil-structure-interaction of a shear wall on a rigid circular foundation embedded in a linear elastic half-space, excited by an incident plane SV wave, is solved by relaxing the zero-stress boundary conditions on the ground surface. An approximate solution of this model was previously presented for the cylindrical approximation of the ground surface. This paper formally neglects such boundary conditions, and as a result, the complexity of the formulation is significantly reduced. Solutions for foundation and building motions in frequency space are compared to the previous results and it is shown that the present approximate solution provides excellent and almost identical results. The objective of this paper is to provide further insight on the role and the effects of surface boundary conditions for this type of problem. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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5. Three-dimensional (3D) soil structure interaction with normal-plane P-wave incidence: Rigid foundation.
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Zhu, Guanying and Lee, Vincent W.
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SOIL structure , *STRUCTURAL dynamics , *STRAINS & stresses (Mechanics) , *FINITE element method , *PIEZOELECTRICITY - Abstract
This paper presents an analytic solution of a three-dimensional Soil-Structural Interaction (3D SSI) model in which the building and foundation are idealized as cylindrical thin-rod and rigid hemisphere. The ground is a stress-free elastic, isotropic, homogenous half-space, and excitation is vertically incident plane P-wave. Analytic three-dimensional (3D) solutions are presented which satisfy the stress-free boundary conditions at the half-space surface. Foundation motions, relative responses of building and surface displacement of soil around building are analyzed and discussed. A comparison with related two-dimensional (2D) SSI close-form solution is also described. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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6. SH waves in a moon-shaped valley.
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Le, Thang, Lee, Vincent W., and Trifunac, Mihailo D.
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WAVE functions , *INDUCED seismicity , *ELASTIC wave propagation , *DISCRETE cosine transforms , *MATHEMATICAL transformations - Abstract
The analytical solution of a two-dimensional moon-shaped alluvial valley embedded in an elastic half-space is analyzed for incident plane SH waves, using the wave function expansion and the Discrete Cosine Transform (DCT). A series of solutions with different depth-to-radius ratios have been computed, analyzed, and discussed. It is shown that amplification of incident motions along the thinning valley segment can be significant. The phenomena of combined action of the waves resulting from (a) turning (reversing the direction of propagation), (b) focusing, and (c) diffraction from the half space into the valley have been examined with an emphasis on the significance for surface-motion amplification and the power to damage man-made structures. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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7. Scattering of plane qP- and qSV-waves by a canyon in a multi-layered transversely isotropic half-space.
- Author
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Ba, Zhenning, Lee, Vincent W., Liang, Jianwen, and Yan, Yang
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METAPHYSICS , *ANGLES , *DYNAMICS , *FORCE & energy , *KINETIC energy - Abstract
An indirect boundary element method (IBEM) is developed to study the scattering and diffraction of plane qP- and qSV-waves by a canyon in a multi-layered transversely isotropic (TI) half-space. First, the exact dynamic stiffness matrix for in-plane motion is constructed to determine the free fields of the multi-layered TI half-space for incident plane qP- and qSV-waves. Dynamic Green's functions for uniformly distributed loads acting on an inclined line are then derived and the scattered fields are expressed as the summation of dynamic responses of a set of fictitious distributed loads applied on the canyon surface. Finally, the boundary condition is introduced to determine the densities of the distributed loads and the total dynamic responses are recovered by adding the free fields to the scattered fields. The proposed IBEM has the merits of distributed loads being directly applied on the real boundary of the irregularity without the problem of singularity, and the discretization effort being restricted to the surface of the canyon. Comparisons with existing numerical solutions for the isotropic (special) case are conducted to confirm the validity of the proposed formulations. And parametric studies are performed in both the frequency and time domains to investigate the influence of material anisotropy, frequency of excitation, incident angle and layering on the surface motions. Numerical results show that the surface motions for the TI medium can be significantly different from those of the isotropic case and that the responses are highly dependent on the TI parameters, especially for the layered TI half-space. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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8. Out-of-plane (SH) soil-structure interaction: Semi-circular rigid foundation revisited.
- Author
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Le, Thang H. and Lee, Vincent W.
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SOIL-structure interaction , *SHEAR walls , *APPROXIMATION theory , *PROBLEM solving , *COMPARATIVE studies - Abstract
The model studied in this paper presents an extension of previous work for a shear wall on a semi-circular rigid foundation in an isotropic homogeneous and elastic half-space. The objective is to develop a soil-structure interaction model that can later be applied to the case of a flexible foundation. As shown in the Introduction below, Luco considered the case of a rigid foundation subjected to vertical incident plane SH waves, and Trifunac extended the solution for the same rigid foundation subjected to SH waves but for arbitrary angles of the incidence. In this paper, a new approach and model are presented for the same semi-circular rigid foundation with a tapered-shape (instead of rectangular) superstructure. The analytical expression for the deformation of the semi-circular rigid foundation below this tapered shear wall with soil-structure interaction in an isotropic homogeneous and elastic half-space is thus derived. Results are then compared with those of Trifunac discussed in the section below. This problem formulation can and will later be extended in the case of a flexible foundation that is semi-circular or arbitrarily shaped. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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9. Two-dimensional scattering and diffraction of P- and SV-waves around a semi-circular canyon in an elastic half-space: An analytic solution via a stress-free wave function.
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Lee, Vincent W. and Liu, Wen-Young
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SCATTERING (Physics) , *DIFFRACTION gratings , *SHEAR waves , *ELASTICITY , *WAVE functions , *CANYONS - Abstract
Abstract: A well-defined boundary-valued problem of wave scattering and diffraction in elastic half-space should have closed-form analytic solutions. This two-dimensional (2-D) scattering around a semi-circular canyon in elastic half-space subjected to seismic plane and cylindrical waves has long been a challenging boundary-value problem. In all cases, the diffracted waves will consist of both longitudinal (P-) and shear (S-) rotational waves. Together at the half-space surface, these in-plane longitudinal P- and shear SV-waves are not orthogonal over the infinite half-space flat-plane boundary. Thus, to simultaneously satisfy both the zero normal and shear stresses at the flat-plane boundary, some approximation of the geometry and/or wave functions often has to be made, or in some cases, relaxed (disregarded). This paper re-examines this two-dimensional (2-D) boundary-value problem from an applied mathematics points of view and redefines the proper form of the orthogonal cylindrical-wave functions for both the longitudinal P- and shear SV-waves so that they can together simultaneously satisfy the zero-stress boundary conditions at the half-space surface. With the zero-stress boundary conditions satisfied at the half-space surface, the most difficult part of the problem will be solved, and the remaining boundary conditions at the finite-canyon surface are then comparatively less complicated to solve. This is now a closed-form analytic solution of the 2-D boundary-valued problem satisfying the half-space zero-stress boundary conditions exactly. [Copyright &y& Elsevier]
- Published
- 2014
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10. A note on three-dimensional scattering and diffraction by a hemispherical canyon–I: Vertically incident plane P-wave.
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Lee, Vincent W. and Zhu, Guanying
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P-waves (Seismology) , *SEISMOLOGISTS , *SURFACE topography , *BOUNDARY value problems , *APPROXIMATION theory , *APPLIED mathematics - Abstract
Abstract: The three-dimensional scattering by a hemi-spherical canyon in an elastic half-space subjected to seismic plane and spherical waves has long been a challenging boundary-value problem. It has been studied by earthquake engineers and strong-motion seismologists to understand the amplification effects caused by surface topography. The scattered and diffracted waves will, in all cases, consist of both longitudinal (P-) and shear (S-) shear waves. Together, at the half-space surface, these waves are not orthogonal over the infinite plane boundary of the half-space. Thus, to simultaneously satisfy both zero normal and shear stresses on the plane boundary numerical approximation of the geometry and/or wave functions were required, or in some cases, relaxed (disregarded). This paper re-examines this boundary-value problem from the applied mathematics point of view, and aims to redefine the proper form of the orthogonal spherical-wave functions for both the longitudinal and shear waves, so that they can together simultaneously satisfy the zero-stress boundary conditions at the half-space surface. With the zero-stress boundary conditions satisfied at the half-space surface, the most difficult part of the problem will be solved, and the remaining boundary conditions at the finite canyon surface will be easy to satisfy. [Copyright &y& Elsevier]
- Published
- 2014
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11. Scattering of anti-plane (SH) waves by a semi-elliptical hill: I—Shallow hill.
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Lee, Vincent W. and Amornwongpaibun, Alongkorn
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SCATTERING (Physics) , *WAVES (Physics) , *ANALYTICAL solutions , *BOUNDARY value problems , *DIMENSIONAL analysis , *WAVE functions , *LINEAR equations , *NUMERICAL analysis - Abstract
Abstract: The paper presents an exact, analytical solution to the boundary-valued problem of the two-dimensional scattering of anti-plane (SH) waves by a shallow, semi-elliptical hill on an elastic half-space, based on the method of wave-function expansion in elliptical coordinate and elliptical cosine half-range expansion. It is expressed in terms of an infinite system of simultaneous linear equations that is later truncated for numerical computation. Some numerical results when semi-elliptical tends to semi-circular are compared with the existing results presented by Lee et al. (2006) [12]. Complicated effects on ground motion due to the existence of an elliptical hill at various aspect ratios and angles of wave incidence are illustrated. [Copyright &y& Elsevier]
- Published
- 2013
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12. Scattering of anti-plane (SH) waves by a semi-elliptical hill: II—deep hill.
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Amornwongpaibun, Alongkorn and Lee, Vincent W.
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SCATTERING (Physics) , *THEORY of wave motion , *ELASTICITY , *WAVE functions , *NUMERICAL analysis , *MATHEMATICAL expansion - Abstract
Abstract: The ground motion and wave propagation resulting from the scattering of anti-plane (SH) waves by a deep semi-elliptical hill on an elastic half-space are investigated. The solution is the closed-form one based on the method of wave-function expansion, and the expansion of elliptical sine and cosine over the half-range [−π/2, π/2]. The analysis shows that the interference of ground motion depends on several factors such as frequency of the incident waves, incident angle, and the aspect ratio of elliptical hills. Similar to part I: Shallow Hill, numerical results when semi-elliptical tends to semi-circular are compared with the work done by Lee et al. [17]. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
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13. Anti-plane foundationless soil–structure interaction
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Lee, Vincent W. and Luo, Hao
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SCATTERING (Physics) , *SOIL-structure interaction , *OPTICAL diffraction , *STRESS waves , *SEISMIC waves , *SHEAR walls , *NUMERICAL solutions to equations , *STRAINS & stresses (Mechanics) , *INTEGRALS - Abstract
Abstract: This paper presents a closed-form wave function analytic solution of two-dimensional scattering and diffraction of anti-plane SH-waves by a two-dimensional foundationless structure that corresponds to a shear wall on an elastic half-space. A wave-function expansion method is used to solve this model by first prescribing a set of wave functions with undetermined coefficients and then assembling them together based on the stress and displacement boundary conditions on the surface between the structure and half space. This results in a set of infinite equations to be solved by truncating to a finite set. The amplitudes and residuals of the displacement and stress distributions around the structure and nearby ground surface will be discussed carefully. While the solution is analytical, the computation of the numerical results involves the evaluation of complicated integrals. This analytic solution will be helpful to the understanding of propagation of seismic or other stress waves within the superstructure(s) undergoing earthquakes or other blast loads. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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14. Should average shear-wave velocity in the top 30m of soil be used to describe seismic amplification?
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Lee, Vincent W. and Trifunac, Mihailo D.
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SHEAR waves , *EARTHQUAKE resistant design , *SEISMIC waves , *SOIL vibration , *SPEED , *NUMERICAL analysis - Abstract
Abstract: The average velocity of shear waves in the top 30m of soil, ν L , has become the parameter used by many engineering design codes and most recently by published empirical-scaling equations to estimate the amplitudes of strong ground motion. Yet there are few studies to determine whether this is a meaningful parameter to use—and whether estimates that do use it are reliable. In 1995, the authors studied this problem and concluded that ν L should not be used. We reported then that an older site characterization in terms of the soil site parameter proposed by Seed et al. , s L , worked better because it included a measure of the thickness of the soil layers to considerably greater depths. Our report, however, made no difference; numerous papers continued to be published based only on scaling in terms of ν L , and worse, they also ignored the geological site conditions. The purpose of this paper is to emphasize that the average shear-wave velocity in the top 30m of soil should not be the only site parameter used to scale strong-motion amplitudes. While the search continues for the more meaningful site parameters to use in empirical scaling of strong earthquake ground motion, it is better to use s L to describe the amplification of seismic waves by soil deposits near the surface. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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15. Zero-stress, cylindrical wave functions around a circular underground tunnel in a flat, elastic half-space: Incident P-waves
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Lin, Chi Hsin, Lee, Vincent W., Todorovska, Maria I., and Trifunac, Mihailo D.
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SEISMIC waves , *STRAINS & stresses (Mechanics) , *WAVE functions , *TUNNELS , *BOUNDARY value problems , *SURFACES (Technology) - Abstract
Abstract: The zero-stress boundary conditions at the surface of the half-space in the presence of surface and sub-surface cavities for in-plane, incident cylindrical P- and SV-waves have always posed challenging problems. The outgoing cylindrical P- and SV-waves can be represented by Hankel functions of radial distance coupled with the sine and cosine functions of angle. Together, at the half-space surface the P- and SV-wave functions are not orthogonal over the semi-infinite radial distance from 0 to infinity. Thus, to simultaneously satisfy the zero in-plane, normal, and shear stresses, an approximation of the geometry is often made. This paper presents an analytical formulation of the boundary-valued problem, where the Hankel wave functions are expressed in integral form, changing the representation from cylindrical to rectangular coordinates, so that the zero-stress boundary conditions at the half-space surface can be applied in a more straightforward way. It is sometimes desirable to use alternate, simpler, or approximate solutions to the boundary-valued problems, without going to great lengths to have all of the boundary conditions satisfied. The free-stress boundary conditions at the half-space surface to be solved here are among the most complicated boundary conditions to be satisfied in the present class of problems. It is thus of interest to illustrate what the solution would be like if the half-space boundary conditions are not imposed—in other words, if they are “relaxed.” A section of this paper is devoted to this approach, and the results of the solutions with the half-spaced, stress-free boundary conditions “imposed” and “relaxed” are presented and compared. The method introduced here may also be applied to more complicated wave-propagation problems, like the diffraction problems involving surface and sub-surface inhomogeneities in a poroelastic half-space medium. [Copyright &y& Elsevier]
- Published
- 2010
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16. Perinatal and Child Factors Mediate the Association between Preeclampsia and Offspring School Performance.
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Zen, Monica, Schneuer, Francisco, Alahakoon, Thushari I., Nassar, Natasha, and Lee, Vincent W.
- Abstract
Objective: To determine whether maternal preeclampsia is an independent risk factor for poorer academic school performance in offspring, taking into account important perinatal and child factors.Study Design: A population-based cohort study using record-linkage of state-wide data was undertaken. We evaluated children born at 28+ weeks of gestation in New South Wales, Australia who had grade 3 record-linked education outcomes via the National Assessment Program-Literacy and Numeracy (NAPLAN) between 2009 and 2014. Children with in utero preeclampsia exposure were compared with those without exposure. Robust multivariable Poisson models were used to determine adjusted relative risks.Results: Crude models demonstrated an increased risk of scoring below the national minimal standard in all 5 domains (reading, writing, spelling, grammar and punctuation, and numeracy) for children exposed to preeclampsia, ranging from a relative risk (RR) of 1.13 (95% CI, 1.04-1.24) for reading to 1.19 (95% CI, 1.09-1.30) for numeracy. These differences were attenuated once adjusted for perinatal and child factors (RR, 1.07 [95% CI, 0.97-1.18] to 1.11 (95% CI, 0.99-1.22]), with combined perinatal and childhood factors mediating between 35.7% (writing) to 55.1% (spelling) of the association. Gestational age at birth was the most important perinatal factor, explaining 10.5% (grammar and punctuation) to 20.6% (writing) of the association between preeclampsia and poor school performance, followed by small for gestational age.Conclusion: The poorer educational performance experienced by children born to women with preeclampsia appears largely attributable to perinatal and childhood factors, suggesting an opportunity to improve school performance in children exposed to preeclampsia by optimizing these perinatal factors, particularly gestational age at birth. [ABSTRACT FROM AUTHOR]- Published
- 2021
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17. The reflection of plane waves in a poroelastic half-space saturated with inviscid fluid
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Lin, Chi-Hsin, Lee, Vincent W., and Trifunac, Mihailo D.
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FORCE & energy , *OSMOSIS , *PERMEABILITY , *ADSORPTION (Chemistry) - Abstract
Abstract: This paper discusses surface displacements, surface strain, rocking, and energy partitioning during reflection-of-plane waves in a fluid-saturated poroelastic half-space. The medium is modeled by Biot''s theory, and is assumed to be saturated with inviscid fluid. A linear porosity-modulus relation based on experimental data on sandstones is used to determine the material parameters for Biot''s model. Numerical results in terms of angle of incident waves and Poisson''s ratio are illustrated for various porosities and degrees of solid frame stiffness. The results show that the amount of solid frame stiffness controls the response of a fluid-saturated porous system. A poroelastic medium with essentially dry-frame stiffness behaves like an elastic medium, and the influence of pore fluid increases as dry-frame stiffness is reduced. The effects of a second P-wave become noticeable in poroelastic media with low dry-frame stiffness. [Copyright &y& Elsevier]
- Published
- 2005
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18. Out-of-plane soil-structure interaction: A tapered shear wall on flexible semi-circular foundation excited by plane SH waves.
- Author
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Le, Thang, Lee, Vincent W., and Trifunac, Mihailo D.
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SOIL-structure interaction , *SHEAR walls , *PLANE wavefronts , *ELASTIC foundations , *FLEXIBLE structures , *REINFORCED masonry , *BENCHMARK problems (Computer science) - Abstract
Although most analytical research on soil-structure interaction (SSI) has assumed a rigid building foundation, numerical and experimental studies have shown that the dynamic response of a structure supported on flexible foundation will differ significantly from the same response on a rigid foundation. The analytical solutions have provided physical insights into the nature of the SSI problems and offered benchmarks to verify the approximate and numerical methods, among others. To this end, in this paper, we present an analytical solution of a tapered shear beam on an elastic semi-circular foundation excited by incident plane SH waves. • Two-dimensional Soil-structure interaction with flexible foundation. • Compared to rigid foundation elastic foundation scatters less of incident wave energy back into half space. • Elastic foundation allows more of the incident wave energy to enter the structure. • Response spectrum method cannot be used for incident waves shorter than twice the foundation width. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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19. Matrix metalloproteinase-9 of tubular and macrophage origin contributes to the pathogenesis of renal fibrosis via macrophage recruitment through osteopontin cleavage.
- Author
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Thian Kui Tan, Guoping Zheng, Tzu-Ting Hsu, So Ra Lee, Jianlin Zhang, Ye Zhao, Xinrui Tian, Yiping Wang, Yuan Min Wang, Qi Cao, Ya Wang, Lee, Vincent W. S., Changqi Wang, Dong Zheng, Alexander, Stephen I., Thompson, Erik, and Harris, David C. H.
- Published
- 2013
- Full Text
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20. A semi-analytical method for vibrations of a layered transversely isotropic ground-track system due to moving train loads.
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BA, Zhenning, Liang, Jianwen, Lee, Vincent W., and Gao, Yanan
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HIGH speed trains , *LIVE loads , *BALLAST (Railroads) , *DYNAMIC stiffness , *RAILROADS , *NUMERICAL calculations - Abstract
The vibrations of a ground-track system subjected to moving train loads are investigated by using a semi-analytical method combining with the substructure technique. In the coupled system, the ground is modeled as a multi-layered transversely isotropic (TI) half-space, and the track is modeled as a three-layered beam structure, which consists of the rails, sleepers and ballast. The two substructures are coupled by the compatibility condition of vertical displacement at the ballast centerline. The displacement and stress responses of the layered TI ground due to the reaction of the track are then obtained by employing the stiffness method. And solutions in the physical domain are recovered by Fourier synthesis of the frequency-wavenumber domain responses. The proposed semi-analytical model has the merits of all parameters having explicit physical meaning, which is very convenient for engineering application, and of the accuracy being not affected by the layers' thickness because of the exact dynamic stiffness matrix. The derived formulations are verified by comparison with the existing solutions for the isotropic medium that is a special case of the more general problem addressed. Numerical calculations are first performed for the case of a single wheel axle load moving at subsonic, transonic and supersonic speeds, and then for the case of the X-2000 high speed train of the Swedish National Railway travelling at a speed of 200 km/h. Numeric results show that the vibrations of the ground-track system can be very different when soil anisotropy is considered. And the variation of the TI parameters alters the resonance frequencies of the ground, which in turn alters the interaction between the track and ground. • A semi-analytical method is proposed to study vibrations of a Transversely Isotropic (TI) ground-track system. • The method gives accurate results and is very convenient for engineering application. • The method can serve as benchmark for the much more complex numerical methods. • Soil anisotropy should be considered to assess the train-induced vibrations accurately. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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21. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Imaging Approaches for Diagnosis.
- Author
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Mai, Jun, Lee, Vincent W., Lopez-Vargas, Pamela, and Vladica, Philip
- Published
- 2015
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22. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Screening for Polycystic Kidney Disease.
- Author
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Rangan, Gopala K., Lee, Vincent W., Alexander, Stephen I., Patel, Chirag, Tunnicliffe, David J., and Vladica, Philip
- Published
- 2015
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23. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Pharmacological Management.
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Mallett, Andrew, Lee, Vincent W., Mai, Jun, Lopez-Vargas, Pamela, and Rangan, Gopala K.
- Published
- 2015
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24. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Management of End-Stage Kidney Disease.
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Lee, Vincent W., Tunnicliffe, David J., and Rangan, Gopala K.
- Published
- 2015
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25. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Monitoring Disease Progression.
- Author
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Mai, Jun, W. Lee, Vincent, Lopez-Vargas, Pamela, Vladica, Philip, Rangan, Gopala K., and Lee, Vincent W
- Published
- 2015
- Full Text
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26. KHA-CARI Autosomal Dominant Polycystic Kidney Disease Guideline: Management of Intracranial Aneurysms.
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Lee, Vincent W., Dexter, Mark A.J., Mai, Jun, Vladica, Philip, Lopez-Vargas, Pamela, and Rangan, Gopala K.
- Published
- 2015
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27. Scattering of plane P- and SV-waves by periodic topography: Modeled by a PIBEM.
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Zhenning, B.A., Gao, Xu, and Lee, Vincent W.
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GREEN'S functions , *BOUNDARY element methods , *TOPOGRAPHY , *PLANE wavefronts - Abstract
For model of periodic topography subjected to plane waves, the wave fields have feature of repeating themselves with a certain shift of phase in the frequency domain. By fully exploring this particular feature, a periodic indirect boundary element method (PIBEM) is proposed to study the scattering of plane P- and SV-waves by periodic topography. The discretization effort of the PIBEM is reduced to a single topography using Green's functions of equivalent distributed loads acting on an inclined line as fundamental solutions. Compared to the traditional way of choosing a certain number of topographies to solve the problem with boundary conditions of other topographies being relaxed, the new method has the merits of higher precision and lower memory requirement. By taking periodic hill and canyon as examples, parametric studies are conducted to investigate the complex effects due to the periodic irregularity. Numerical results show that responses of periodic topography are quite different from those of a single and multiple topographies, demonstrating that it is very difficult to obtain the accurate results by choosing a certain number of topographies. In addition, periodic canyon has a stronger shielding effect on P-waves, while periodic hill has a stronger shielding effect on SV-waves. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
28. Scattering and amplification of SV waves by a semi-cylindrical hill in a half-space by a wavefunction-based meshless method using mapping and point-matching strategies.
- Author
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Dai, Denghui, Zhang, Ning, Lee, Vincent W., Gao, Yufeng, and Chen, Xin
- Subjects
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SCATTERING (Physics) , *THEORY of wave motion , *EXPONENTIAL functions , *TRANSFER functions - Abstract
The zero-stress boundary conditions along the semi-infinite surface of a half-space have always posed challenging issues for the classical wavefunction expansion method to deal with in-plane wave propagation and scattering problems. A mapping and a point matching method are both introduced in this study to overcome the issue to propose a new wavefunction series solution to the scattering of SV-waves by a semi-cylindrical hill. The semi-infinite space is divided into an open and an enclosed region with a virtual boundary. After mapping the infinite surface into a finite interval, a good match of the zero-stress conditions in the open region is achieved. The zero-stress conditions in the enclosed hill region are satisfied analytically using the orthogonality of complex exponential functions. Taking into account the stress and displacement continuity conditions on the virtual boundary, the series solution can be obtained by solving a matrix to get the unknown coefficients of the wave fields. The accuracy of the solution is verified by comparing with two existing numerical solutions. To be helpful for engineering applications, the acceleration time histories at different locations under a real earthquake input are found to be obtainable based on the transfer functions of the frequency domain solution. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
29. 3D dynamic response of a multi-layered transversely isotropic half-space subjected to a moving point load along a horizontal straight line with constant speed.
- Author
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BA, Zhenning, Liang, Jianwen, Lee, Vincent W., and Ji, Hang
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DYNAMIC mechanical analysis , *MECHANICAL loads , *ISOTROPIC properties , *STIFFNESS (Mechanics) , *WAVENUMBER , *MATHEMATICAL domains - Abstract
The steady-state dynamic response of a multi-layered transversely isotropic (TI) half-space generated by a point load moving along a horizontal straight line with constant speed is investigated in this paper. To solve this problem, the direct stiffness method combined with the inverse Fourier transform is employed. First, the dynamic equilibrium equations for the TI medium are solved in the frequency and wavenumber domains and the exact three-dimensional (3D) dynamic stiffness matrix for the layered TI half-space is established. Then, the solution in the frequency and wavenumber domains is obtained through the direct stiffness method. Finally, the dynamic response in the time and space domains is obtained using the double inverse Fourier transform with respect to the frequency and one horizontal wavenumber. The accuracy of the method is verified through comparisons with the results for the limiting isotropic case ( de Barros and Luco, 1994 ) as well as the results for the non-moving 3D point load being applied in a multi-layered TI half-space ( Khojasteh et al., 2011 ). Numerical results for both the uniform TI half-space and multi-layered TI half-space are presented, and the effects of the moving speed and especially the material anisotropy on the dynamic response are analyzed. Numerical results show that the dynamic response in a TI medium can be significantly different from that in an isotropic medium, and material anisotropy is very important for the accurate assessment of the dynamic response due to a point load moving in a TI half-space. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
30. Dynamic impedance functions for a rigid strip footing resting on a multi-layered transversely isotropic saturated half-space.
- Author
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Ba, Zhenning, Liang, Jianwen, Lee, Vincent W., and Kang, Zeqing
- Subjects
- *
CONCRETE footings , *MECHANICAL loads , *ISOTROPIC properties , *RIGID dynamics , *NUMERICAL analysis - Abstract
This paper is concerned with the dynamic impedance functions (force-displacement relationships) of a surface rigid strip footing resting on a multi-layered transversely isotropic (TI) saturated half-space. The rigid footing is perfectly bonded to the layered half-space and is subjected to time-harmonic vertical, horizontal and moment loadings. The half-space under consideration consists of a number of horizontal layers with different thicknesses and an underlying half-space, which are all governed by the Biot's poroelastodynamic theory. The surface of the half-space can be either fully permeable or impermeable. The dynamic interaction problem is solved by employing an indirect boundary element method (IBEM), which uses Green's functions for uniform strip loads acting on the surface of a multi-layered TI saturated half-space. The discretization of the method is restricted to the footing-subsoil interface because of the layered half-space kernel functions, and the accuracy of the method would not be affected by the thickness of the discrete layers because of the exact dynamic stiffness matrix. Comparison with the existing solutions for the TI elastic and isotropic saturated media is conducted to verify the method, which are special cases of the more general problems addressed. Selected numerical solutions are presented to portray the influence of material anisotropy, frequency of excitation, surfaced drainage condition and layering on the dynamic impedance functions. Numerical results show that the dynamic impedance functions for the TI material can be significantly different from those of the isotropic material. The variation of the TI parameters alters the resonant frequencies of the layer and further alters the dynamic interaction between the layer and the footing. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
31. Plane strain dynamic responses of a multi-layered transversely isotropic saturated half-space.
- Author
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Ba, Zhenning, Kang, Zeqing, and Lee, Vincent W.
- Subjects
- *
STRAIN energy , *ISOTROPIC properties , *FOURIER transforms , *ANISOTROPY , *WAVENUMBER - Abstract
An exact dynamic stiffness matrix method is proposed to evaluate the plane strain responses due to time-harmonic loads and pore fluid pressure applied in the interior or on the surface of a multi-layered transversely isotropic (TI) saturated half-space. First, the governing equations of the TI saturated medium are solved analytically by using the Fourier transform and the exact global dynamic stiffness matrix in the wavenumber domain is established describing the relationship between the generalized displacement and force vectors. Then, solutions of the multi-layered system for discrete wavenumbers are obtained by using the dynamic stiffness matrix method, which are then synthesized to retrieve the responses in the physical domain. The accuracy of the method is confirmed by comparison with existing solutions for the TI elastic as well as isotropic saturated media that are special cases of the more general problems addressed. Selected numerical results are presented to investigate the effects of material anisotropy, layering, surface drainage condition, buried depth of the source and permeability on the responses. It is found that material anisotropy is very important for the accurate assessment of the dynamic responses subjected to time-harmonic sources. In addition, the presented solutions form a complete set of Green's functions which is required in the application of plane strain boundary methods for multi-layered TI saturated medium. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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- View/download PDF
32. Wave propagation of buried spherical SH-, P1-, P2- and SV-waves in a layered poroelastic half-space.
- Author
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Ba, Zhenning, Liang, Jianwen, and Lee, Vincent W.
- Subjects
- *
SHEAR waves , *POROELASTICITY , *LIGHT propagation , *STIFFNESS (Engineering) , *DYNAMIC models - Abstract
Few studies have investigated the wave propagation of spherical sources in a layered half-space. In this paper, based on Biot's theory of poroelastic media, the exact anti-axisymmetric (cylindrical SH-waves) and axisymmetric (cylindrical P1-P2-SV waves) stiffness matrices for a layered poroelastic half-space are derived. Then the dynamic responses due to buried spherical SH-, P1-, P2- and SV-waves in a layered poroelastic half-space are studied by using the direct stiffness method combined with the Hankel transform. The present solutions are in good agreements with those in a uniform pure elastic half-space as well as a uniform poroelastic half-space. These solutions have the advantages that all of the parameters in the solutions have explicit physical meanings and the thickness of discrete layers does not affect the precision of calculation; thus, the presented formulations are very convenient for engineering applications. Numerical calculations are performed in both the frequency and time domains by taking buried spherical SH-, P1- and SV- waves in a uniform poroelastic half-space and in a single poroelastic layer over a poroelastic half-space as examples. The numerical results show that wave propagation of spherical sources in a layered half-space can be significantly different from that in a uniform half-space; the dynamic responses are highly dependent on the saturated parameters, vibration frequency and the surface drained condition; the presence of the underlying half-space makes the time histories of the dynamic responses in a single layered half-space much more complicated with much longer duration. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
33. Three-dimensional diffraction of plane P, SV & SH waves by a hemispherical alluvial valley
- Author
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Lee, Vincent W.
- Published
- 1984
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34. A new fast algorithm for the calculation of response of a single-degree-of-freedom system to arbitrary load in time
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Lee, Vincent W.
- Published
- 1984
- Full Text
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35. Torsional accelerograms
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Lee, Vincent W. and Trifunac, Mihailo D.
- Published
- 1985
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36. A note on the scattering of elastic plane waves by a hemispherical canyon
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Lee, Vincent W.
- Published
- 1982
- Full Text
- View/download PDF
37. Scattering of plane SV-waves by a circular lined tunnel in an undersea saturated half-space.
- Author
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Li, Weihua, Zhu, Sainan, Lee, Vincent W., Shi, Peixin, and Zhao, Chenggang
- Subjects
- *
UNDERWATER tunnels , *POISSON'S ratio , *WATERLOGGING (Soils) , *HANKEL functions , *SEISMIC response , *PORE water pressure , *SOIL structure - Abstract
Considering the fluid-soil coupling of saturated soil and seawater-saturated soil-structure dynamic interaction, the Hankel function integral transformation method is employed herein to obtain an analytical solution to the scattering and diffraction problem posed by the plane SV-waves in an undersea lined tunnel. This study is based on the porous medium wave function theory of saturated soil proposed by Biot and the ideal fluid medium wave theory. The impact of factors, such as the incident angle, frequency, water depth, buried depth of tunnel, porosity, and Poisson's ratio of the saturated soil, on the horizontal and vertical displacement at the seawater–saturated soil interface, and on the pore water pressure and total circumferential stress at the saturated soil–tunnel interface, are computed and analyzed. • Analytical solution to scattering of plane SV waves by a circular lined tunnel in an undersea saturated half-space is obtained. • The Hankel function integral transformation method is employed herein. • The effects of water depth, saturated soil parameters and wave characters on the seismic responses of the tunnel and undersea layer are analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
38. Synthetic earthquake ground motions on an array
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Todorovska, Maria I., Trifunac, Mihailo D., Lee, Vincent W., and Orbović, Nebojša
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- *
EARTHQUAKE zones , *NONLINEAR analysis , *SURFACE strains , *RAYLEIGH waves , *STRAINS & stresses (Mechanics) , *APPROXIMATION theory , *MATHEMATICAL models - Abstract
Abstract: Linear and especially non-linear analyses of spatially extended structures, such as pipelines and bridges, often requires specification of time histories of ground motion at an array of closely spaced points. As the number of dense accelerograph arrays worldwide is small, and the number of earthquake observations is limited, synthetic motions with desired characteristics become necessary. This paper presents a method for synthesizing such motions, which is an extension of the SYNACC method, developed first in the early 1970s for synthetic accelerations, velocities and displacements at a point, and later extended to synthetic near surface strains, rotations and curvatures of ground motion at a point. It consists of unfolding in time a site specific Fourier amplitude spectrum of ground acceleration, obtained by an empirical scaling model, by representing the ground motion as a superposition of traveling wavelets of Love and Rayleigh waves and body waves, which propagate with phase and group velocities consistent with the dispersion characteristic of the site geology, approximated by parallel layers. Uniform hazard Fourier spectra or any specified target Fourier spectrum can also be used. Derivations of the point strains, rotations and curvatures are also presented. The method is illustrated for scenario M6.5 and M7.5 earthquakes and three dispersion models. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
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39. Lipopolysaccharide-pretreated plasmacytoid dendritic cells ameliorate experimental chronic kidney disease.
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Zheng, Dong, Cao, Qi, Lee, Vincent W S, Wang, Ya, Zheng, Guoping, Wang, YuanMin, Tan, Thian Kui, Wang, Changqi, Alexander, Stephen I, Harris, David C H, and Wang, Yiping
- Subjects
- *
DENDRITIC cells , *T cells , *CELLULAR immunity , *IMMUNOLOGIC diseases , *IMMUNE response - Abstract
Plasmacytoid dendritic cells play important roles in inducing immune tolerance, preventing allograft rejection, and regulating immune responses in both autoimmune disease and graft-versus-host disease. In order to evaluate a possible protective effect of plasmacytoid dendritic cells against renal inflammation and injury, we purified these cells from mouse spleens and adoptively transferred lipopolysaccharide (LPS)-treated cells, modified ex vivo, into mice with adriamycin nephropathy. These LPS-treated cells localized to the kidney cortex and the lymph nodes draining the kidney, and protected the kidney from injury during adriamycin nephropathy. Glomerulosclerosis, tubular atrophy, interstitial expansion, proteinuria, and creatinine clearance were significantly reduced in mice with adriamycin nephropathy subsequently treated with LPS-activated plasmacytoid dendritic cells as compared to the kidney injury in mice given naive plasmacytoid dendritic cells. In addition, LPS-pretreated cells, but not naive plasmacytoid dendritic cells, convert CD4+CD25− T cells into Foxp3+ regulatory T cells and suppress the proinflammatory cytokine production of endogenous renal macrophages. This may explain their ability to protect against renal injury in adriamycin nephropathy. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
40. Scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space, modeled using the indirect boundary element method
- Author
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Liang, Jianwen, You, Hongbing, and Lee, Vincent W.
- Subjects
- *
ADSORPTION (Chemistry) , *PERMEABILITY , *POROSITY , *SCATTERING (Physics) - Abstract
Abstract: The scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space is modeled using the indirect boundary element method in the frequency domain. The free-field responses are calculated to determine the displacements and stresses at the surface of the canyon, and fictitious distributed loads are then applied at the surface of the canyon in the free field to calculate the Green''s functions for displacements and stresses. The amplitudes of the fictitious distributed loads are determined from the boundary conditions, and the displacements arising from the waves in the free field and from the fictitious distributed loads are summed to obtain the solution. The effects of fluid saturation, boundary conditions, porosity, and soil layers on the surface displacement amplitudes and phase shifts are discussed, and some useful conclusions are obtained. It is shown that the surface displacement amplitudes due to saturation and boundary conditions, different porosities, or the presence of a soil layer can be very dissimilar, and large phase shifts can be observed. The resulting wavelengths for an undrained saturated poroelastic medium are slightly longer than those for a drained saturated poroelastic medium; and are longer for a drained saturated poroelastic medium than those for a dry poroelastic medium. As porosity increases, the wavelengths become longer; and a layered half-space produces longer wavelengths than a homogeneous half-space. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
41. Diffraction of plane SV waves by a shallow circular-arc canyon in a saturated poroelastic half-space
- Author
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Liang, Jianwen, Ba, Zhenning, and Lee, Vincent W.
- Subjects
- *
ADSORPTION (Chemistry) , *HYDRAULIC engineering , *EVAPORATION (Meteorology) , *POROSITY - Abstract
Abstract: An analytical solution for the scattering and diffraction of incident plane SV waves by a shallow circular-arc canyon in a saturated poroelastic half-space is derived by the wave function expansion method. The solution is utilized to analyze the dependence of the computed surface motions on the incident frequencies, incident angles, porosity, boundary drainage and Poisson''s ratio. It is shown that, depending on the incident angles, the surface displacement amplitudes around a canyon in a dry poroelastic half-space and saturated poroelastic half-space can be very different. The surface displacement amplitudes of an undrained saturated poroelastic half-space are close to those of a drained saturated poroelastic half-space. For low porosity, the surface displacement amplitudes of a saturated poroelastic half-space are almost identical to those of a dry poroelastic half-space, and drainage condition has little influence on the surface displacement amplitudes. But for high porosity, the effect of drainage condition becomes significant, and for the same porosity, the displacement amplitudes of an undrained saturated half-space will be larger than those of a drained saturated half-space. Poisson''s ratio is also an important factor affecting the surface displacement amplitudes around the canyon, both in drained and undrained conditions, but leads to larger effects for an undrained saturated half-space than for a drained saturated half-space. Large pore pressures are found around the canyon and their amplitudes depend on the incident angles and frequencies. Below the surface, the amplitudes of pore pressures are less than they are at the surface, especially for high frequencies. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
42. 2.5D scattering of obliquely incident seismic waves due to a canyon cut in a multi-layered TI saturated half-space.
- Author
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BA, Zhenning, Sang, Qiaozhi, and Lee, Vincent W.
- Subjects
- *
GREEN'S functions , *BOUNDARY element methods , *RAYLEIGH waves , *CANYONS , *DRAINAGE , *SEISMIC waves , *PERMEABILITY , *LIVE loads - Abstract
This paper extends the two and a half-dimensional (2.5D) indirect boundary element method (IBEM) from the isotropic medium to the transversely isotropic (TI) saturated case, to study the three-dimensional (3D) scattering behavior of a two-dimensional (2D) geometric canyon cut in a multi-layered TI half-space. This method, conquering the drawbacks of both 2D and 3D simulations, can realistically assess the ground motion with less computation effort. The 3D exact stiffness matrix (Ba and Liang 2017) is adopted to solve the free-fields, through which the system with a great number of layers can be conveniently handled and the precision is not affected by layer's thickness. And the Green's functions for moving distributed loads in a multi-layered TI saturated half-space are derived in detail within the framework of Biot's theory (1962a, b), which is subsequently utilized to construct the scattered fields. The accuracy is illustrated by comparison with a verification example (Liang and Liu 2009) for a 2D isotropic case. The effects of some key parameters (anisotropy degree, incident angle, drainage condition, permeability and layering) on dynamic response are investigated through numerical implementations in frequency domain. The results show that material anisotropy has a noticeable influence on the displacement and pore pressure, and the influence becomes prominent for high incident frequency. The displacement amplitude is rather sensitive to permeability, whereas its distribution is hardly affected by permeability. Furthermore, the existence of layer complicates the scattering mechanics of layered system, heavily relating to material anisotropy. • The 2.5D IBEM is proposed to study 3D scattering of a 2D canyon in a TI saturated half-space. • The moving Green's functions of layered TI saturated half-space are semi-analytically derived. • The method can realistically assess the ground motion with less computation effort. • Material anisotropy has a noticeable influence on displacement and pore pressure responses. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
43. Free-field response of a transversely isotropic saturated half-space subjected to incident plane qP1- and qSV-waves.
- Author
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Ba, Zhenning, Liang, Jianwen, Lee, Vincent W., and Sang, Qiaozhi
- Subjects
- *
PLANE wavefronts , *SEISMIC waves , *FREE surfaces , *PERMEABILITY , *SCATTERING (Physics) , *ORTHOTROPIC plates , *CONTAINER ships - Abstract
Many natural soils and rocks are not only saturated but are also anisotropic. Due to the fundamental importance of having an understanding of the free-field response of an anisotropic half-space subjected to incident seismic waves, the surface displacements, surface strain, rocking, and pore pressure due to reflection of plane waves in a transversely isotropic (TI) saturated half-space are discussed. The governing equations in u- w formulation are first derived and the plane harmonic wave solution of these equations is then proposed. The free-field response is finally determined by specifying the stress free and surface drainage conditions at the boundary. The half-space surface can be either completely permeable or impermeable, and the excitation includes incident plane qP1- and qSV-waves. The proposed formulations are verified by comparing our results with those for the isotropic half-space. A parametric study is performed to illustrate the influences of the material anisotropy, surface drainage condition and permeability on the surface motions. Numerical results show that the surface motions of the TI half-space are significantly different from those of the isotropic case. The surface motions of the TI half-space are much more dependent on the TI parameters when the incident waves are qSV-waves than when they are qP1-waves because the dynamic responses change sharply as the incident angles approach the critical angles. In contrast with the isotropic case, with an identical angle of 45°, the total reflection angle of the TI half-space varies with the TI parameters. In general, the surface motions of the permeable surface are smaller than those of the impermeable surface, particularly in response to incident qSV-waves. • Free field response of a TI saturated half-space for incident plane waves is presented. • The solution is of great importance in solving wave scattering and SSI problems. • The free field response of qSV-waves is more dependent on the TI parameters. • Material anisotropy should be considered to provide more accurate free field results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
44. Running safety assessment of trains considering post-earthquake damage state of bridge–track system.
- Author
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Tang, Yongjiu, Zhu, Zhihui, Ba, Zhenning, Lee, Vincent W., and Gong, Wei
- Subjects
- *
EARTHQUAKE damage , *SPEED limits , *GROUND motion , *EARTHQUAKE intensity , *SEISMIC response , *RUNNING training , *TELECOMMUNICATION - Abstract
• The damage state and residual deformation of the bridge-track system after different earthquake intensities are studied. • OpenSees-TRBF co-simulation method is proposed for the running safety analysis considering the post-earthquake damage state of the bridge-track system. • The post-earthquake safety speed thresholds of train are analyzed. A bridge–track system (BTS) is inevitably damaged during an earthquake; this is reflected in its stiffness deterioration and residual deformation, which affect the post-earthquake running safety of trains. The influence of the post-earthquake damage state of an actual BTS on train running safety remains unclear. Hence, this study mainly discussed the influence of post-earthquake bridge–track damage state and residual deformation on running safety and established a safe speed limit for trains under different seismic intensities. A finite element (FE) model of a simply supported railway BTS was established using the OpenSees software. A nonlinear seismic response analysis was performed under different ground motion intensities (0.1, 0.3, and 0.6 g for frequent, design, and rare earthquakes, respectively), and bridge damage, fastener damage, and residual deformation of the rail after the earthquakes were studied. An OpenSees-TRBF (train-rail-bridge-foundation coupled system dynamic analysis software, TRBF) co-simulation method was developed to analyze the running safety of trains after earthquakes under a damaged state of the BTS based on the TCP/IP communication interaction technology. A safe speed limit for trains considering the post-earthquake damage state and residual deformation was proposed, providing a reference for the post-earthquake capacity of trains. The results of the BTS seismic damage analysis showed that the residual displacement of the bearing was the fundamental reason for the change in the rail line shape, and fastener damage mainly occurred in the range of 2–4 fasteners at the end of the girder under the design and rare earthquakes. The results of the running safety analysis showed that, if damage to the BTS is ignored, the running safety after an earthquake will be misjudged. Based on the continuous overrun time limit index, the running safety indices for ground motion intensities of 0–0.4, 0.4–0.5, and 0.5–0.6 g could meet the speed requirements of 350, 300, and 150 km/h, respectively. This study provides some references and suggestions for the running safety of trains following an earthquake. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. Autophagy links β-catenin and Smad signaling to promote epithelial-mesenchymal transition via upregulation of integrin linked kinase.
- Author
-
Pang, Min, Wang, Hailong, Rao, Padmashree, Zhao, Ye, Xie, Jun, Cao, Qi, Wang, Yiping, Wang, Yuan Min, Lee, Vincent W., Alexander, Stephen I., Harris, David C.H., and Zheng, Guoping
- Subjects
- *
AUTOPHAGY , *CATENINS , *SMAD proteins , *INTEGRIN-linked kinase , *TRANSFORMING growth factors , *LABORATORY mice - Abstract
TGF-β1 induces epithelial-mesenchymal transition (EMT) and autophagy in a variety of cells. However, the role of autophagy in TGF-β1-induced EMT has not been clearly elucidated and the underlying mechanisms are unclear. In the present study, we found that TGF-β1 induced both autophagy and EMT in mouse tubular epithelial C1.1 cells. Inhibition of autophagy by 3-methyladenine or siRNA knockdown of Beclin 1 reduced TGF-β1-induced increase of vimentin and decreased E-cadherin expression. In contrast, rapamycin-associated enhancement of TGF-β1-induced autophagy increased EMT of C1.1 cells. Serum rescue inhibited autophagy followed by reversal of EMT. Blocking of autophagosome-lysosomal but not proteosomal degradation reduced the decrease of E-cadherin, demonstrating a role for autophagy in degradation of E-cadherin during EMT. Autophagy promoted the activation of Src and Src-associated phosphorylation of β-catenin at Y-654 leading to pY654-β-catenin/p-Smad2 complex formation. Chromatin immunoprecipitation assay demonstrated binding by the pY654-β-catenin/p-Smad2 complex to ILK promoter thus increasing ILK expression. Taken together, our results demonstrate that TGF-β1-induced autophagy links β-catenin and Smad signaling to promote EMT in C1.1 cells through a novel pY654-β-catenin/p-Smad2/ILK pathway. The pathway delineated links disruption of E-cadherin/β-catenin-mediated cell–cell contact to induction of EMT via upregulation of ILK. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
46. A two-step approach combining FK with SE for simulating ground motion due to point dislocation sources.
- Author
-
Ba, Zhenning, Wu, Mengtao, Liang, Jianwen, Zhao, Jingxuan, and Lee, Vincent W.
- Subjects
- *
GROUND motion , *SEISMIC waves , *SEISMIC response , *THEORY of wave motion , *GROUND cover plants - Abstract
It has been well established that source-path-site effects have had an essential impact on the seismic analysis of major infrastructure over the past few decades, where the accurate and efficient modeling of seismic wave propagation can become a critical issue. In this study, a two-step approach combining the frequency-wavenumber (FK) technique with the spectral element (SE) method is developed based on the concept of domain reduction to simulate three-dimensional (3D) ground motion due to point dislocation sources. In the first step, the seismic responses for the dislocations in a layered half-space crustal model are solved exactly using the FK method and converted into effective input seismic loads around the region of interest. In the second step, the local wavefields of a 3D complex site are finely simulated using the SEM, while absorbing conditions are imposed at five boundaries of the SE model to achieve absorption of the outward scattered energy. The semi-analytical FK method is well-matched to the propagation frequencies because it allows the broadband synthesis associated with engineered systems to be addressed without additional calculations. When the FK is combined with the SEM, it is feasible to efficiently simulate earthquake ground motions covering a broad range of frequencies in the region of interest. Comparisons with the results of existing studies and the traditional SEM show that our approach is accurate and robust for arbitrary geometries and point sources. To further illustrate the efficiency and general applicability of the proposed method, three examples are presented. The results demonstrate that the two-step approach can consider the effects of the seismic source, propagation path, and local site geological conditions on the earthquake ground motions and serve as an effective forward modeling tool for reducing the computational cost. • The FK and SEM are hybridized to simulate seismic response of a 3D complex layered site. • The presented methodology is programmed and well verified by comparison with existing solutions. • The effects of the source-, propagation-, and site conditions on ground motions are studied. • The proposed two-step approach reduces computational cost in source-path-site modeling. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
47. Failed renoprotection by alternatively activated bone marrow macrophages is due to a proliferation-dependent phenotype switch in vivo.
- Author
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Cao, Qi, Wang, Yiping, Zheng, Dong, Sun, Yan, Wang, Changqi, Wang, Xin M, Lee, Vincent W S, Wang, Ya, Zheng, Guoping, Tan, Thian K, Wang, Yuan M, Alexander, Stephen I, and Harris, David C H
- Subjects
- *
BONE marrow diseases , *MACROPHAGES , *CELL proliferation , *PHENOTYPES , *DOXORUBICIN - Abstract
Alternatively activated macrophages (M2) regulate immune responses and ex vivo polarized splenic M2 are able to ameliorate renal injury including models of renal disease, such as adriamycin nephropathy. Whether M2 derived from other organs have similar protective efficacy is unknown. Here, we report adoptively transferred bone marrow M2 macrophages did not improve renal function or reduce renal injury in adriamycin nephropathy, whereas splenic M2 macrophages were protective. Bone marrow and splenic M2 macrophages showed similar regulatory phenotypes and suppressive functions in vitro. Within the inflamed kidney, suppressive phenotypes in bone marrow but not in splenic M2 macrophages, were dramatically reduced. Loss of the suppressive phenotype in bone marrow M2 was related to strong proliferation of bone marrow M2. Bone marrow M2 proliferation in vivo correlated with M-CSF expression by tubular cells in the inflamed kidney. Inhibition of M-CSF in vitro limited bone marrow M2 proliferation and prevented switch of phenotype. Proliferating cells derived from transfused bone marrow M2 were inflammatory rather than regulatory in their phenotype and function. Thus bone marrow in contrast to splenic M2 macrophages do not protect against renal structural and functional injury in murine adriamycin nephropathy. The failed renoprotection of bone marrow M2 is due to the switch of transfused M2 macrophages from a regulatory to an inflammatory phenotype. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
48. Discrete functions of M2a and M2c macrophage subsets determine their relative efficacy in treating chronic kidney disease.
- Author
-
Lu, Junyu, Cao, Qi, Zheng, Dong, Sun, Yan, Wang, Changqi, Yu, Xiao, Wang, Ya, Lee, Vincent W S, Zheng, Guoping, Tan, Thian K., Wang, Xin, Alexander, Stephen I, Harris, David C H, and Wang, Yiping
- Subjects
- *
MACROPHAGES , *KIDNEY diseases , *ANTI-inflammatory agents , *DOXORUBICIN , *GLOMERULOSCLEROSIS - Abstract
Two types of alternatively activated macrophages, M2a induced by IL-4/IL-13 and M2c by IL-10/TGF-β, exhibit anti-inflammatory functions in vitro and protect against renal injury in vivo. Since their relative therapeutic efficacy is unclear, we compared the effects of these two macrophage subsets in murine adriamycin nephrosis. Both subsets significantly reduced renal inflammation and renal injury; however, M2c macrophages more effectively reduced glomerulosclerosis, tubular atrophy, interstitial expansion, and proteinuria than M2a macrophages. The M2c macrophages were also more effective than M2a in reduction of macrophage and CD4+ T-cell infiltration in kidney. Moreover, nephrotic mice treated with M2c had a greater reduction in renal fibrosis than those treated with M2a. M2c but not M2a macrophages induced regulatory T cells (Tregs) from CD4+CD25- T cells in vitro, and increased Treg numbers in local draining lymph nodes of nephrotic mice. To determine whether the greater protection with M2c was due to their capability to induce Tregs, the Tregs were depleted by PC61 antibody in nephrotic mice treated with M2a or M2c. Treg depletion diminished the superior effects of M2c compared to M2a in protection against renal injury, inflammatory infiltrates, and renal fibrosis. Thus, M2c are more potent than M2a macrophages in protecting against renal injury due to their ability to induce Tregs. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
49. Scattering of elastic spherical P, SV, and SH waves by three-dimensional hill in a layered half-space.
- Author
-
Ba, Zhenning, Fu, Jisai, Liu, Yue, Lee, Vincent W., and Wang, Ying
- Subjects
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RAYLEIGH waves , *ELASTIC scattering , *GREEN'S functions , *SPHERICAL waves , *BOUNDARY element methods , *SEISMIC response - Abstract
In this paper, the method of combining indirect boundary element method (IBEM) with the region-matching technique is used to solve the seismic responses of a three-dimensional (3D) hill in a layered half-space subjected to spherical P, SV, and SH waves. The direct stiffness method and Hankel transform method are used to solve the free field of spherical wave source field, and the scattering field is constructed by Green's function in half-space. The correctness and accuracy of this method are verified by comparing with the results of several literatures. This method can be used to deal with arbitrary-shaped hill topography, and has the advantages of wide applicability, high accuracy and fast convergence. Taking Gaussian hill topography as an example, the scattering phenomenon of hill under the incidence of spherical P, SV and SH waves is studied, and the influences of hill topography, source location and frequency on site seismic responses are explored. The results show that: Existence of the hill topography has evident focusing effect, which significantly enlarges the seismic response on the hill surface, and the hill has evident isolation effect in the process of energy propagation; With higher frequency of the incident wave, the fluctuation amplitude of displacement on the hill surface increases; The fluctuation amplitude of horizontal displacement on the hill surface is SV wave > SH wave > P wave, and the vertical displacement is P wave > SV wave. • The scattering of spherical P, SV, and SH waves by 3D hill in a layered half-space is studied. • Combining the direct stiffness method and Hankel transform method, the free field of spherical wave source are derived. • Assuming that the incident wave is spherical wave, the near-source topographic effect caused by hills is revealed. • The method can deal with 3D arbitrary-shaped hill topography, and has the merits of high accuracy and easy convergence. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
50. Surface motion of a layered transversely isotropic half-space with a 3D arbitrary-shaped alluvial valley under qP-, qSV- and SH-waves.
- Author
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Liang, Jianwen, Wu, Mengtao, Ba, Zhenning, and Lee, Vincent W.
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GREEN'S functions , *BOUNDARY element methods , *MULTILAYERS , *INCLINED planes , *VALLEYS - Abstract
An indirect boundary element method (IBEM) is proposed to solve the scattering of qP-, qSV- and SH-waves by a three-dimensional (3D) arbitrary-shaped alluvial valley embedded in a layered transversely isotropic (TI) half-space. First, the 3D dynamic Green's functions for the uniformly distributed loads acting on an interior inclined plane in a multi-layered TI half-space are derived by means of exact stiffness matrix method combined with the Fourier transform. Next, the deduced 3D Green's functions are used as fundamental solutions to formulate a special IBEM, and the IBEM is further used to investigate the surface motion of a 3D surface irregularities in a multi-layered TI half-space subjected to incident body waves. Compared to the traditional BEM adopting Green's functions for the concentrated loads as the kernel, the new method has the merits of higher precision and none of the problem of singularity. By comparing our results with the published ones, accuracy of the presented 3D Green's functions as well as IBEM solution are verified. To further demonstrate the general applicability and effectiveness of the present method, taking a semi-ellipsoidal alluvial valley in a single TI layered half-space as an example, numerical calculations are performed in both the frequency and time domain. Results in frequency domain show that material anisotropy has an important influence on the surface motion of semi-ellipsoidal alluvial valley. In general, the displacement amplitudes decrease as the degree of anisotropy increases. Displacement amplification spectra are significantly different among the various materials, which strongly depend on the incident angles and the observation points. Results in time domain show that with the increase of the degree of anisotropy, the peak ground acceleration (PGA) of each point inside the valley gradually decreases. Compared with the case of isotropic, the difference of PGA can reach 53.8%. • Scattering of a 3D arbitrary-shaped alluvial valley in a layered TI half-space is studied by using an IBEM. • Dynamic Green's functions for uniformly distributed loads acting on an inclined plane are derived. • The method has the merits of high precision and none of the problem of singularity. • The ground motion considering anisotropy is assessed both in the frequency and time domains. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
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