The wave dispersion due to the lateral inertia in the split Hopkinson pressure bar(SHPB) with large-(diameter) bar is numerically analyzed by means of the LS-DYNA3D code. The results show that, ① the stress distribut...The wave dispersion due to the lateral inertia in the split Hopkinson pressure bar(SHPB) with large-(diameter) bar is numerically analyzed by means of the LS-DYNA3D code. The results show that, ① the stress distribution across the bar section is non-uniform along the radius direction and such non-uniformity depends on the material Poisson ratio and propagation distance; ② with increasing the bar diameter, the high frequency oscillations are notably enhanced and the rise time of wave front becomes longer, meanwhile the amplitude of the stress wave attenuates; ③ with decreasing the rise time of wave front, the wave dispersion markedly enhanced, particularly in the large diameter bar. All of those effects should not be neglected in order to obtain accurate results by the SHPB test..展开更多
Motivated by the great potential of carbon nanotubes for developing nanofluidic devices, this paper presents a nonlocal elastic, Timoshenko multi-beam model with the second order of strain gradient taken into consider...Motivated by the great potential of carbon nanotubes for developing nanofluidic devices, this paper presents a nonlocal elastic, Timoshenko multi-beam model with the second order of strain gradient taken into consideration and derives the corresponding dispersion relation of flexural wave in multi-walled carbon nanotubes conveying fuids. The study shows that the moving flow reduces the phase velocity of flexural wave of the lowest branch in carbon nanotubes. The phase velocity of flexural wave of the lowest branch decreases with an increase of flow velocity. However, the effects of flow velocity on the other branches of the wave dispersion are not obvious. The effect of microstructure characterized by nonlocal elasticity on the dispersion of flexural wave becomes more and more remarkable with an increase in wave number.展开更多
AIM:To investigate the P wave dispersion as a non-invasive marker of intra-atrial conduction disturbances in patients with Wilson's disease. METHODS:We compared Wilson's disease patients (n = 18) with age matc...AIM:To investigate the P wave dispersion as a non-invasive marker of intra-atrial conduction disturbances in patients with Wilson's disease. METHODS:We compared Wilson's disease patients (n = 18) with age matched healthy subjects (n = 15) as controls. The diagnosis was based on clinical symptoms, laboratory tests (ceruloplasmin, urinary and hepatic copper concentrations). P wave dispersion, a measurement of the heterogeneity of atrial depolarization, was measured as the difference between the duration of the longest and the shortest P-waves in 12 lead electrocardiography. RESULTS:All the patients were asymptomatic on cardiological examination and have sinusal rhythm in electrocardiography. Left ventricular and left atrial diameters, left ventricular ejection fraction and left ventricular mass index were similar in both groups. The Wilson's disease patients had a significantly higher P wave dispersion compared with the controls (44.7 ± 5.8 vs 25.7 ± 2.5, P < 0.01). CONCLUSION:There was an increase in P wave dispersion in cardiologically asymptomatic Wilson's disease patients which probably represents an early stage of cardiac involvement.展开更多
Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a non...Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a nonlinear joint inversion of receiver functions and surface wave dispersion.We obtained some detailed information about the Tangshan earthquake region and its adjacent areas,including sedimentary thickness,Moho depth,and crustal and upper mantle S-wave velocity.Meanwhile,we also obtained the vP/vS structure along two sections across the Tangshan region.The results show that:(1)the Moho depth ranges from 30 km to 38 km,and it becomes shallower from Yanshan uplift area to North China basin;(2)the thickness of sedimentary layer ranges from 0 km to 3 km,and it thickens from Yanshan uplift region to North China basin;(3)the S-wave velocity structure shows that the velocity distribution of the upper crust has obvious correlation with the surface geological structure,while the velocity characteristics of the middle and lower crust are opposite to that of the upper crust.Compared with the upper crust,the heterogeneity of the middle and lower crust is more obvious;(4)the discontinuity of Moho on the two sides of Tangshan fault suggests that Tangshan fault cut the whole crust,and the low vS and high vP/vS beneath the Tangshan earthquake region may reflect the invasion of mantle thermal material through Tangshan fault.展开更多
Effect of the particle number density on the dispersion properties of longitudinal and transverse lattice waves in a two-dimensional Yukawa charged-dust system is investigated using molecular dynamics simulation. The ...Effect of the particle number density on the dispersion properties of longitudinal and transverse lattice waves in a two-dimensional Yukawa charged-dust system is investigated using molecular dynamics simulation. The dispersion relations for the waves are obtained. It is found that the frequencies of both the longitudinal and transverse dust waves increase with the density and when the density is sufficiently high a cutoff region appears at the short wavelength. With the increase of the particle number density, the common frequency tends to increase, and the sound speed of the longitudinal wave also increases, but that of the transverse wave remains low.展开更多
Ambient noise tomography is a rapidly emerging field of seismological research. This paper presents the current status of ambient noise data processing and its development history over the past several years, with the...Ambient noise tomography is a rapidly emerging field of seismological research. This paper presents the current status of ambient noise data processing and its development history over the past several years, with the intention to explain and justify this development through salient examples. The ambient noise data processing procedure can be divided into four principal phases： ① single station data preparation; ② cross- correlation and temporal stacking; ③ measurements of dispersion curves （ performed with frequency-time analysis for both group and phase speeds） ; ④ quality control, including SNR analysis and selection of the acceptable measurements. In addition, we provide a specific solution for a better use of the seismic station data to ambient noise study.展开更多
The utilization of urban underground space in a smart city requires an accurate understanding of the underground structure.As an effective technique,Rayleigh wave exploration can accurately obtain information on the s...The utilization of urban underground space in a smart city requires an accurate understanding of the underground structure.As an effective technique,Rayleigh wave exploration can accurately obtain information on the subsurface.In particular,Rayleigh wave dispersion curves can be used to determine the near-surface shear-wave velocity structure.This is a typical multiparameter,high-dimensional nonlinear inverse problem because the velocities and thickness of each layer must be inverted simultaneously.Nonlinear methods such as simulated annealing(SA)are commonly used to solve this inverse problem.However,SA controls the iterative process though temperature rather than the error,and the search direction is random;hence,SA always falls into a local optimum when the temperature setting is inaccurate.Specifically,for the inversion of Rayleigh wave dispersion curves,the inversion accuracy will decrease with an increasing number of layers due to the greater number of inversion parameters and large dimension.To solve the above problems,we convert the multiparameter,highdimensional inverse problem into multiple low-dimensional optimizations to improve the algorithm accuracy by incorporating the principle of block coordinate descent(BCD)into SA.Then,we convert the temperature control conditions in the original SA method into error control conditions.At the same time,we introduce the differential evolution(DE)method to ensure that the iterative error steadily decreases by correcting the iterative error direction in each iteration.Finally,the inversion stability is improved,and the proposed inversion method,the block coordinate descent differential evolution simulated annealing(BCDESA)algorithm,is implemented.The performance of BCDESA is validated by using both synthetic data and field data from western China.The results show that the BCDESA algorithm has stronger global optimization capabilities than SA,and the inversion results have higher stability and accuracy.In addition,synthetic data analysis also shows that BCDESA can avoid the problems of the conventional SA method,which assumes the S-wave velocity structure in advance.The robustness and adaptability of the algorithm are improved,and more accurate shear-wave velocity and thickness information can be extracted from Rayleigh wave dispersion curves.展开更多
We presents a generalized(2+1)-dimensional Sharma-Tasso-Olver-Burgers(STOB)equation,unifying dissipative and dispersive wave dynamics.By introducing an auxiliary potential𝑦as a new space variable and employing...We presents a generalized(2+1)-dimensional Sharma-Tasso-Olver-Burgers(STOB)equation,unifying dissipative and dispersive wave dynamics.By introducing an auxiliary potential𝑦as a new space variable and employing a simpler deformation algorithm,we deform the(1+1)-dimensional STOB model to higher dimensions.The resulting equation is proven Lax-integrable via introducing strong and weak Lax pairs.Traveling wave solutions of the(2+1)-dimensional STOB equation are derived through an ordinary differential equation reduction,with implicit solutions obtained for a special case.Crucially,we demonstrate that the system admits dispersionless decompositions into two types:Case 1 yields non-traveling twisted kink and bell solitons,while Case 2 involves complex implicit functions governed by cubic-algebraic constraints.Numerical visualizations reveal novel anisotropic soliton structures,and the decomposition methodology is shown to generalize broadly to other higher dimensional dispersionless decomposition solvable integrable systems.展开更多
In this paper, we introduce the complex modulus to express the viscoelasticity of a medium. According to the correspondence principle, the Biot-Squirt （BISQ） equations in the steady-state case are presented for the ...In this paper, we introduce the complex modulus to express the viscoelasticity of a medium. According to the correspondence principle, the Biot-Squirt （BISQ） equations in the steady-state case are presented for the space-frequency domain described by solid displacements and fluid pressure in a homogeneous viscoelastic medium. The effective bulk modulus of a multiphase flow is computed by the Voigt formula, and the characteristic squirt-flow length is revised for the gas-included case. We then build a viscoelastic BISQ model containing a multiphase flow. Through using this model, wave dispersion and attenuation are studied in a medium with low porosity and low permeability. Furthermore, this model is applied to observed interwell seismic data. Analysis of these data reveals that the viscoelastic parameter tan6 is not a constant. Thus, we present a linear frequen- cy-dependent function in the interwell seismic frequency range to express tanG. This improves the fit between the observed data and theoretical results.展开更多
The fluid-saturated porous layered(FSPL)media widely exist in the Earth's subsurface and their overall mechanical properties,microscopic pore structure and wave propagation characteristics are highly relevant to t...The fluid-saturated porous layered(FSPL)media widely exist in the Earth's subsurface and their overall mechanical properties,microscopic pore structure and wave propagation characteristics are highly relevant to the in-situ stress.However,the effect of in-situ stress on wave propagation in FSPL media cannot be well explained with the existing theories.To fill this gap,we propose the dynamic equations for FSPL media under the effect of in-situ stress based on the theories of poroacoustoelasticity and anisotropic elasticity.Biot loss mechanism is considered to account for the stress-dependent wave dispersion and attenuation induced by global wave-induced fluid flow.Thomsen's elastic anisotropy parameters are used to represent the anisotropy of the skeleton.A plane-wave analysis is implemented on dynamic equations yields the analytic solutions for fast and slow P waves and two S waves.Modelling results show that the elastic anisotropy parameters significantly determine the stress dependence of wave velocities.Vertical tortuosity and permeability have remarkable effects on fast and slow P-wave velocity curves and the corresponding attenuation peaks but have little effect on S-wave velocity.The difference in velocities of two S waves occurs when the FSPL medium is subjected to horizontal uniaxial stress,and the S wave along the stress direction has a larger velocity,which implies that the additional anisotropy other than that induced by the beddings appears due to horizontal stress.Besides,the predicted velocity results have the reasonable agreement with laboratory measurements.Our equations and results are relevant to a better understanding of wave propagation in deep strata,which provide some new theoretical insights in the rock physics,hydrocarbon exploration and stress detection in deep-strata shale reservoirs.展开更多
The paper studies the dispersion of axisymmetric longitudinal waves in the bi-material compound circular cylinder made of linear viscoelastic materials.The investigations are carried out within the scope of the piecew...The paper studies the dispersion of axisymmetric longitudinal waves in the bi-material compound circular cylinder made of linear viscoelastic materials.The investigations are carried out within the scope of the piecewise homogeneous body model by utilizing the exact equations of linear viscoelasto-dynamics.The corresponding dispersion equation is derived for an arbitrary type of hereditary operator and the algorithm is developed for its numerical solution.Concrete numerical results are obtained for the case where the relations of the constituents of the cylinder are described through fractional exponential operators.The influence of the viscosity of the materials of the compound cylinder on the wave dispersion is studied through the rheological parameters which indicate the characteristic creep time and long-term values of the elastic constants of these materials.Dispersion curves are presented for certain selected dispersive and non-dispersive attenuation cases under various values of the problem parameters and the influence of the aforementioned rheological parameters on these curves is discussed.As a result of the numerical investigations,in particular,it is established that in the case where the rheological parameters of the components of the compound cylinder are the same,the viscosity of the layers’materials causes the axisymmetric wave propagation velocity to decrease.展开更多
Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to...Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to spread, and the modes overlap in both time and frequency domains as they propagate through the structures. By using a two-component laser interferometer technique, in combination with a priori knowledge of the dispersion characteristics and wave structure information of Lamb wave modes, a two-component signal processing technique is presented for implementing dispersion removal and mode separation simultaneously for two modes mixture signals of Lamb waves. The proposed algorithm is first processed and verified using synthetic Lamb wave signals. Then, the two-component displacements test experiment is conducted using different aluminum plate samples. Moreover, we confirm the effectiveness and robustness of this method.展开更多
To accurately characterize the shear wave speed dispersion of seafloor sediments in the northern South China Sea,five types of sediments including silty clay,clayey silt,sandy silt,silty sand,and clayey sand were sele...To accurately characterize the shear wave speed dispersion of seafloor sediments in the northern South China Sea,five types of sediments including silty clay,clayey silt,sandy silt,silty sand,and clayey sand were selected,on which the measurements of the shear wave speed at 0.5-2.0 kHz and related physical properties were performed.Results reveal that the shear wave speed of sediments increases as the frequency increases,and the dispersion enhanced in the sediments in the order of silty clay,clayey silt,sandy silt,silty sand,and clayey sand,at a linear change rate of 0.727,0.787,3.32,4.893,and 6.967 m s−1 kHz−1,respectively.Through regression analysis,linear and logarithmic regression equations for the correlation between shear wave speed and frequency were established for each sediment type and the determination coefficients of regression equations indicate that the correlation is closer to a logarithmic relationship.The Grain-Shearing(GS)and Biot-Stoll models were used to calculate the shear wave speed dispersion of the five sediment types,and the comparison between theoretical prediction and measured results of shear wave speeds shows that the GS model can more accurately describe the shear wave speed dispersion characteristics of these sediments in the frequency band of 0.5-2.0 kHz.In the same band,the predictions obtained by using the Biot-Stoll model are significantly different from the measured data.展开更多
The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency...The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh-Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances （cold test）. Periodic structures resonate at specific frequencies when the terminals are shorted numerical calculation, synthetic technique and cold appropriately. The dispersion characteristics obtained from test are compared, and an excellent agreement is achieved.展开更多
On April 3,2024,a magnitude Mw 7.4 earthquake struck the city of Hualien,Taiwan,China,causing casualties and immense damage.This earthquake triggered a tsunami,which was recorded by the nearby tide gauges and Deep-Oce...On April 3,2024,a magnitude Mw 7.4 earthquake struck the city of Hualien,Taiwan,China,causing casualties and immense damage.This earthquake triggered a tsunami,which was recorded by the nearby tide gauges and Deep-Ocean Assessment and Reporting of Tsunamis(DART)buoys.These recordings are valuable for evaluating the tsunami source and quantifying the tsunami characteristics.In this study,we conduct tsunami simulations based on three earthquake source models,and analyze their reliability by comparing the computed results with observed waveforms.The evaluated source models are the United States Geological Survey(USGS)finite-fault model,and two uniform slip models using different scaling relations.The tsunami waves generated by each source are simulated with a nonhydrostatic tsunami model,which accounts for the effects of wave dispersion.The computed tsunami arrival times and wave heights are compared to the observed data and show high consistency,indicating that the magnitude and location of the earthquake source are well estimated.Also,the three source models with different rupture area and average slip lead to almost the same tsunami waves at each station,which suggests that earthquake rupture details have limited impact on far-filed tsunami records.It is also found that wave dispersion effects in this event are negligible at most stations.The findings are useful for tsunami warning.For fast warning purposes,it is practically useful to adopt simplified uniform slip models,which are able to predict the tsunami arrival time and wave height relatively well without knowing the earthquake source details.展开更多
Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in ser...Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in series for combinations of submarine ridges of different heights and ISW of different amplitudes. The resuhant wave motions were found differing from thee of surface gravity waves. In deeper water, where an ISW of depression-type prevailed, the process of wave breaking displayed downward motion with continuous eddy on the front face of the ridge followed by upward motion towards the apex of the obstacle. Experimental results also suggested that blockage parameter ξ could be applied to classify various degrees of ISW-ridge interaction, i.e., ξ 〈 0.5 for weak interaction, 0.5 〈 ξ 〈 0.7 for moderate interaction, and 0.7 〈 ξ for wave breaking.展开更多
Effective recognition of a coalfield fire area improves fire-fighting efficiency and helps avoid potential geological hazards. Coalfield fire areas are hard to detect accurately using general geophysical methods. This...Effective recognition of a coalfield fire area improves fire-fighting efficiency and helps avoid potential geological hazards. Coalfield fire areas are hard to detect accurately using general geophysical methods. This paper describes simulations of shallow, buried coalfield fires based on real geological conditions. Recognizing the coalfield fire by Rayleigh wave is proposed. Four representative geological models are constructed, namely; the non-burning model, the pseudo-burning model, the real-burning model, and the hidden-burning model. Numerical simulation using these models shows many markedly different characteristics between them in terms of Rayleigh wave dispersion and Eigen displacement. These characteristics, as well as the shear wave velocity obtained by inverting the fundamental dispersion, make it possible to distinguish the type of the coalfield fire area and indentify the real and serious coalfield fire area. The results are very helpful for future application of Rayleigh waves for the detection of coalfield fire area.展开更多
BACKGROUND： Activation of the sympathetic nervous system plays an important role in regulating cardiovascular actions. P wave parameters can provide general information on central cardiovascular autonomic regulatory ...BACKGROUND： Activation of the sympathetic nervous system plays an important role in regulating cardiovascular actions. P wave parameters can provide general information on central cardiovascular autonomic regulatory responses, which are altered in patients with anxiety disorders and depression. In particular, there are no reports addressing changes in P wave duration and dispersion. OBJECTIVE： To compare the differences in P wave duration and P wave dispersion between patients with anxiety disorders and depression, because patients with anxiety disorders and depression develop abnormal electrocardiograms. DESIGN, TIME AND SETTING： A non-randomized concurrent controlled study was performed. Patients with depression and general anxiety disorders were admitted at the psychiatry outpatient clinics of the Medical Faculty of Duezce University of Turkey between May 2005 and October 2006. PARTICIPANTS： A total of 71 consecutive patients with depression and anxiety disorders, as well as 50 physically and mentally healthy age- and gender-matched controls were selected. METHODS： Electrocardiogram records were obtained at the time of admission to the outpatient clinics. MAIN OUTCOME MEASURES： P wave duration and P wave dispersion were measured. RESULTS： Both the maximum （Prnax） and minimum （Pmin） P wave duration were greater in patients with psychiatric disorders than in healthy controls. Pmax was significantly greater in patients with depression or anxiety disorders （Bonferroni test, P 〈 0.017）. The P wave dispersion was similar between patients and controls （P 〉 0.017）. P waves were similar between panic patients and other anxiety patients. Beck depression results were positively correlated with Prawn and Prnax （r= 0.374, 0.302, P = 0.013, 0.049, respectively）, and not associated with P wave dispersion （P 〉 0.05）. CONCLUSION： Psychiatric disorders are associated with increases in Prnax, but not with P wave dispersion. The P wave changes were associated with the degree of depression.展开更多
The crustal structure in Myanmar can provide valuable information for the eastern margin of the ongoing IndoEurasian collision system.We successively performed H-k stacking of the receiver function and joint inversion...The crustal structure in Myanmar can provide valuable information for the eastern margin of the ongoing IndoEurasian collision system.We successively performed H-k stacking of the receiver function and joint inversion of the receiver function and surface wave dispersion to invert the crustal thickness(H),shear wave velocity(V_(S)),and the V_(P)/V_(S) ratio(k)beneath nine permanent seismic stations in Myanmar.H was found to increase from 26 km in the south and east of the study area to 51 km in the north and west,and the V_(P)/V_(S) ratio was complex and high.Striking differences in the crust were observed for different tectonic areas.In the Indo-Burma Range,the thick crust(H~51 km)and lower velocities may be related to the accretionary wedge from the Indian Plate.In the Central Myanmar Basin,the thin crust(H=26.9-35.5 km)and complex V_(P)/V_(S) ratio and V_(S) suggest extensional tectonics.In the Eastern Shan Plateau,the relatively thick crust and normal V_(P)/V_(S) ratio are consistent with its location along the western edge of the rigid Sunda Block.展开更多
In this study, the ambient seismic noise cross-correlation technique is applied to estimate the upper structure of the crust beneath Great Island of Tierra del Fuego（TdF）, Argentina, by the analysis of shortperiod R...In this study, the ambient seismic noise cross-correlation technique is applied to estimate the upper structure of the crust beneath Great Island of Tierra del Fuego（TdF）, Argentina, by the analysis of shortperiod Rayleigh wave group velocities. The island, situated in the southernmost South America, is a key area of investigation among the interaction between the South American and Scotia plates and is considered as a very seismically active one. Through cross-correlating the vertical components of ambient seismic noise registered at four broadband stations in TdF, we were able to extract Rayleigh waves which were used to estimate group velocities in the period band of 2.5-16 s using a timefrequency analysis. Although ambient noise sources are distributed in homogeneously, robust empirical Green＇s functions could be recovered from the cross-correlation of 12 months of ambient noise, The observed group velocities were inverted considering a non-linear iterative damped least-squares inversion procedure and several 1-D shear wave velocity models of the upper crust were obtained.According to the inversion results, the S-wave velocity ranges between 1.75 and 3,7 km/s in the first10 km of crust, depending on the pair of stations considered. These results are in agreement to the major known surface and sub-surface geological and tectonic features known in the area. This study represents the first ambient seismic noise analysis in TdF in order to constraint the upper crust beneath this region.It can also be considered as a successful feasibility study for future analyses with a denser station deployment for a more detailed imaging of structure.展开更多
文摘The wave dispersion due to the lateral inertia in the split Hopkinson pressure bar(SHPB) with large-(diameter) bar is numerically analyzed by means of the LS-DYNA3D code. The results show that, ① the stress distribution across the bar section is non-uniform along the radius direction and such non-uniformity depends on the material Poisson ratio and propagation distance; ② with increasing the bar diameter, the high frequency oscillations are notably enhanced and the rise time of wave front becomes longer, meanwhile the amplitude of the stress wave attenuates; ③ with decreasing the rise time of wave front, the wave dispersion markedly enhanced, particularly in the large diameter bar. All of those effects should not be neglected in order to obtain accurate results by the SHPB test..
基金supported in part by the National Natural Science Foundation of China (No10702026)
文摘Motivated by the great potential of carbon nanotubes for developing nanofluidic devices, this paper presents a nonlocal elastic, Timoshenko multi-beam model with the second order of strain gradient taken into consideration and derives the corresponding dispersion relation of flexural wave in multi-walled carbon nanotubes conveying fuids. The study shows that the moving flow reduces the phase velocity of flexural wave of the lowest branch in carbon nanotubes. The phase velocity of flexural wave of the lowest branch decreases with an increase of flow velocity. However, the effects of flow velocity on the other branches of the wave dispersion are not obvious. The effect of microstructure characterized by nonlocal elasticity on the dispersion of flexural wave becomes more and more remarkable with an increase in wave number.
文摘AIM:To investigate the P wave dispersion as a non-invasive marker of intra-atrial conduction disturbances in patients with Wilson's disease. METHODS:We compared Wilson's disease patients (n = 18) with age matched healthy subjects (n = 15) as controls. The diagnosis was based on clinical symptoms, laboratory tests (ceruloplasmin, urinary and hepatic copper concentrations). P wave dispersion, a measurement of the heterogeneity of atrial depolarization, was measured as the difference between the duration of the longest and the shortest P-waves in 12 lead electrocardiography. RESULTS:All the patients were asymptomatic on cardiological examination and have sinusal rhythm in electrocardiography. Left ventricular and left atrial diameters, left ventricular ejection fraction and left ventricular mass index were similar in both groups. The Wilson's disease patients had a significantly higher P wave dispersion compared with the controls (44.7 ± 5.8 vs 25.7 ± 2.5, P < 0.01). CONCLUSION:There was an increase in P wave dispersion in cardiologically asymptomatic Wilson's disease patients which probably represents an early stage of cardiac involvement.
基金This research is supported by Spark Program of Earthquake Science(No.XH18065Y)National Natural Science Foundation of China(Nos.41774066 and 41604049)。
文摘Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a nonlinear joint inversion of receiver functions and surface wave dispersion.We obtained some detailed information about the Tangshan earthquake region and its adjacent areas,including sedimentary thickness,Moho depth,and crustal and upper mantle S-wave velocity.Meanwhile,we also obtained the vP/vS structure along two sections across the Tangshan region.The results show that:(1)the Moho depth ranges from 30 km to 38 km,and it becomes shallower from Yanshan uplift area to North China basin;(2)the thickness of sedimentary layer ranges from 0 km to 3 km,and it thickens from Yanshan uplift region to North China basin;(3)the S-wave velocity structure shows that the velocity distribution of the upper crust has obvious correlation with the surface geological structure,while the velocity characteristics of the middle and lower crust are opposite to that of the upper crust.Compared with the upper crust,the heterogeneity of the middle and lower crust is more obvious;(4)the discontinuity of Moho on the two sides of Tangshan fault suggests that Tangshan fault cut the whole crust,and the low vS and high vP/vS beneath the Tangshan earthquake region may reflect the invasion of mantle thermal material through Tangshan fault.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11675261 and 21403297the Scientific Research Foundation of Ludong University under Grant No LY2014010
文摘Effect of the particle number density on the dispersion properties of longitudinal and transverse lattice waves in a two-dimensional Yukawa charged-dust system is investigated using molecular dynamics simulation. The dispersion relations for the waves are obtained. It is found that the frequencies of both the longitudinal and transverse dust waves increase with the density and when the density is sufficiently high a cutoff region appears at the short wavelength. With the increase of the particle number density, the common frequency tends to increase, and the sound speed of the longitudinal wave also increases, but that of the transverse wave remains low.
基金Jointly funded by the Natural Science Foundation of China(40774018)the Seismic Scientific and Technological Spark Project,China Earthquake Administration(XH13009Y)the Earthquake Research Foundation,Earthquake Administration of Anhui Province(20120702)
文摘Ambient noise tomography is a rapidly emerging field of seismological research. This paper presents the current status of ambient noise data processing and its development history over the past several years, with the intention to explain and justify this development through salient examples. The ambient noise data processing procedure can be divided into four principal phases： ① single station data preparation; ② cross- correlation and temporal stacking; ③ measurements of dispersion curves （ performed with frequency-time analysis for both group and phase speeds） ; ④ quality control, including SNR analysis and selection of the acceptable measurements. In addition, we provide a specific solution for a better use of the seismic station data to ambient noise study.
基金Supported by National Natural Science Foundation of China(NOs.41974150,42174158,42174151,41804126)a supporting program for outstanding talent of the University of Electronic Science and Technology of China(No.2019-QR-01)+1 种基金Project of Basic Scientific Research Operating Expenses of Central Universities(ZYGX2019J071ZYGX 2020J013).
文摘The utilization of urban underground space in a smart city requires an accurate understanding of the underground structure.As an effective technique,Rayleigh wave exploration can accurately obtain information on the subsurface.In particular,Rayleigh wave dispersion curves can be used to determine the near-surface shear-wave velocity structure.This is a typical multiparameter,high-dimensional nonlinear inverse problem because the velocities and thickness of each layer must be inverted simultaneously.Nonlinear methods such as simulated annealing(SA)are commonly used to solve this inverse problem.However,SA controls the iterative process though temperature rather than the error,and the search direction is random;hence,SA always falls into a local optimum when the temperature setting is inaccurate.Specifically,for the inversion of Rayleigh wave dispersion curves,the inversion accuracy will decrease with an increasing number of layers due to the greater number of inversion parameters and large dimension.To solve the above problems,we convert the multiparameter,highdimensional inverse problem into multiple low-dimensional optimizations to improve the algorithm accuracy by incorporating the principle of block coordinate descent(BCD)into SA.Then,we convert the temperature control conditions in the original SA method into error control conditions.At the same time,we introduce the differential evolution(DE)method to ensure that the iterative error steadily decreases by correcting the iterative error direction in each iteration.Finally,the inversion stability is improved,and the proposed inversion method,the block coordinate descent differential evolution simulated annealing(BCDESA)algorithm,is implemented.The performance of BCDESA is validated by using both synthetic data and field data from western China.The results show that the BCDESA algorithm has stronger global optimization capabilities than SA,and the inversion results have higher stability and accuracy.In addition,synthetic data analysis also shows that BCDESA can avoid the problems of the conventional SA method,which assumes the S-wave velocity structure in advance.The robustness and adaptability of the algorithm are improved,and more accurate shear-wave velocity and thickness information can be extracted from Rayleigh wave dispersion curves.
基金supported by the National Natural Science Foundations of China(Grant Nos.12235007,12375003,and 11975131).
文摘We presents a generalized(2+1)-dimensional Sharma-Tasso-Olver-Burgers(STOB)equation,unifying dissipative and dispersive wave dynamics.By introducing an auxiliary potential𝑦as a new space variable and employing a simpler deformation algorithm,we deform the(1+1)-dimensional STOB model to higher dimensions.The resulting equation is proven Lax-integrable via introducing strong and weak Lax pairs.Traveling wave solutions of the(2+1)-dimensional STOB equation are derived through an ordinary differential equation reduction,with implicit solutions obtained for a special case.Crucially,we demonstrate that the system admits dispersionless decompositions into two types:Case 1 yields non-traveling twisted kink and bell solitons,while Case 2 involves complex implicit functions governed by cubic-algebraic constraints.Numerical visualizations reveal novel anisotropic soliton structures,and the decomposition methodology is shown to generalize broadly to other higher dimensional dispersionless decomposition solvable integrable systems.
基金supported by the National Natural Sciences Foundation of China(Grant Nos.41390452 and 11002025)the National Science Foundation for Distinguished Young Scholars of China(Grant No.40725012)
文摘In this paper, we introduce the complex modulus to express the viscoelasticity of a medium. According to the correspondence principle, the Biot-Squirt （BISQ） equations in the steady-state case are presented for the space-frequency domain described by solid displacements and fluid pressure in a homogeneous viscoelastic medium. The effective bulk modulus of a multiphase flow is computed by the Voigt formula, and the characteristic squirt-flow length is revised for the gas-included case. We then build a viscoelastic BISQ model containing a multiphase flow. Through using this model, wave dispersion and attenuation are studied in a medium with low porosity and low permeability. Furthermore, this model is applied to observed interwell seismic data. Analysis of these data reveals that the viscoelastic parameter tan6 is not a constant. Thus, we present a linear frequen- cy-dependent function in the interwell seismic frequency range to express tanG. This improves the fit between the observed data and theoretical results.
基金the sponsorship of the National Natural Science Foundation of China(Grant Nos.42174139,41974119,42030103)the Laoshan Laboratory Science and Technology Innovation Program(Grant No.LSKJ202203406)+1 种基金the China Scholarship Council(Grant No.202206450050)the Innovation Fund Project for Graduate Students of China University of Petroleum(East China)(Grant No.23CX04003A)。
文摘The fluid-saturated porous layered(FSPL)media widely exist in the Earth's subsurface and their overall mechanical properties,microscopic pore structure and wave propagation characteristics are highly relevant to the in-situ stress.However,the effect of in-situ stress on wave propagation in FSPL media cannot be well explained with the existing theories.To fill this gap,we propose the dynamic equations for FSPL media under the effect of in-situ stress based on the theories of poroacoustoelasticity and anisotropic elasticity.Biot loss mechanism is considered to account for the stress-dependent wave dispersion and attenuation induced by global wave-induced fluid flow.Thomsen's elastic anisotropy parameters are used to represent the anisotropy of the skeleton.A plane-wave analysis is implemented on dynamic equations yields the analytic solutions for fast and slow P waves and two S waves.Modelling results show that the elastic anisotropy parameters significantly determine the stress dependence of wave velocities.Vertical tortuosity and permeability have remarkable effects on fast and slow P-wave velocity curves and the corresponding attenuation peaks but have little effect on S-wave velocity.The difference in velocities of two S waves occurs when the FSPL medium is subjected to horizontal uniaxial stress,and the S wave along the stress direction has a larger velocity,which implies that the additional anisotropy other than that induced by the beddings appears due to horizontal stress.Besides,the predicted velocity results have the reasonable agreement with laboratory measurements.Our equations and results are relevant to a better understanding of wave propagation in deep strata,which provide some new theoretical insights in the rock physics,hydrocarbon exploration and stress detection in deep-strata shale reservoirs.
文摘The paper studies the dispersion of axisymmetric longitudinal waves in the bi-material compound circular cylinder made of linear viscoelastic materials.The investigations are carried out within the scope of the piecewise homogeneous body model by utilizing the exact equations of linear viscoelasto-dynamics.The corresponding dispersion equation is derived for an arbitrary type of hereditary operator and the algorithm is developed for its numerical solution.Concrete numerical results are obtained for the case where the relations of the constituents of the cylinder are described through fractional exponential operators.The influence of the viscosity of the materials of the compound cylinder on the wave dispersion is studied through the rheological parameters which indicate the characteristic creep time and long-term values of the elastic constants of these materials.Dispersion curves are presented for certain selected dispersive and non-dispersive attenuation cases under various values of the problem parameters and the influence of the aforementioned rheological parameters on these curves is discussed.As a result of the numerical investigations,in particular,it is established that in the case where the rheological parameters of the components of the compound cylinder are the same,the viscosity of the layers’materials causes the axisymmetric wave propagation velocity to decrease.
基金Project supported by the National Natural Science Foundation of China(Grant No.11374230)
文摘Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to spread, and the modes overlap in both time and frequency domains as they propagate through the structures. By using a two-component laser interferometer technique, in combination with a priori knowledge of the dispersion characteristics and wave structure information of Lamb wave modes, a two-component signal processing technique is presented for implementing dispersion removal and mode separation simultaneously for two modes mixture signals of Lamb waves. The proposed algorithm is first processed and verified using synthetic Lamb wave signals. Then, the two-component displacements test experiment is conducted using different aluminum plate samples. Moreover, we confirm the effectiveness and robustness of this method.
基金supported by the Basic Scientific Fund for National Public Research Institutes of China(No.GY0220Q09)the National Natural Science Foundation of China(Nos.41676055,41527809,42176191,and 41330965)+1 种基金the Opening Fund of Qingdao National Laboratory for Marine Science and Technology(No.QNLM2016ORP0209)the Taishan Scholar Pro-ject Funding(No.tspd20161007).
文摘To accurately characterize the shear wave speed dispersion of seafloor sediments in the northern South China Sea,five types of sediments including silty clay,clayey silt,sandy silt,silty sand,and clayey sand were selected,on which the measurements of the shear wave speed at 0.5-2.0 kHz and related physical properties were performed.Results reveal that the shear wave speed of sediments increases as the frequency increases,and the dispersion enhanced in the sediments in the order of silty clay,clayey silt,sandy silt,silty sand,and clayey sand,at a linear change rate of 0.727,0.787,3.32,4.893,and 6.967 m s−1 kHz−1,respectively.Through regression analysis,linear and logarithmic regression equations for the correlation between shear wave speed and frequency were established for each sediment type and the determination coefficients of regression equations indicate that the correlation is closer to a logarithmic relationship.The Grain-Shearing(GS)and Biot-Stoll models were used to calculate the shear wave speed dispersion of the five sediment types,and the comparison between theoretical prediction and measured results of shear wave speeds shows that the GS model can more accurately describe the shear wave speed dispersion characteristics of these sediments in the frequency band of 0.5-2.0 kHz.In the same band,the predictions obtained by using the Biot-Stoll model are significantly different from the measured data.
文摘The linear dispersion relation of a trapezoidally corrugated slow wave structure （TCSWS） is analyzed and presented. The size parameters of the TCSWS are chosen in such a way that they operate in the x-band frequency range. The dispersion relation is solved by utilizing the Rayleigh-Fourier method by expressing the radial function in terms of the Fourier series. A highly accurate synthetic technique is also applied to determine the complete dispersion characteristics from experimentally measured resonances （cold test）. Periodic structures resonate at specific frequencies when the terminals are shorted numerical calculation, synthetic technique and cold appropriately. The dispersion characteristics obtained from test are compared, and an excellent agreement is achieved.
基金The National Key R&D Program of China under contract No.2024YFF0506800the National Natural Science Foundation of China under contract No.T2122012.
文摘On April 3,2024,a magnitude Mw 7.4 earthquake struck the city of Hualien,Taiwan,China,causing casualties and immense damage.This earthquake triggered a tsunami,which was recorded by the nearby tide gauges and Deep-Ocean Assessment and Reporting of Tsunamis(DART)buoys.These recordings are valuable for evaluating the tsunami source and quantifying the tsunami characteristics.In this study,we conduct tsunami simulations based on three earthquake source models,and analyze their reliability by comparing the computed results with observed waveforms.The evaluated source models are the United States Geological Survey(USGS)finite-fault model,and two uniform slip models using different scaling relations.The tsunami waves generated by each source are simulated with a nonhydrostatic tsunami model,which accounts for the effects of wave dispersion.The computed tsunami arrival times and wave heights are compared to the observed data and show high consistency,indicating that the magnitude and location of the earthquake source are well estimated.Also,the three source models with different rupture area and average slip lead to almost the same tsunami waves at each station,which suggests that earthquake rupture details have limited impact on far-filed tsunami records.It is also found that wave dispersion effects in this event are negligible at most stations.The findings are useful for tsunami warning.For fast warning purposes,it is practically useful to adopt simplified uniform slip models,which are able to predict the tsunami arrival time and wave height relatively well without knowing the earthquake source details.
基金The work was supported bythe National Science Council ,Taiwan,China (Grant No. NSC93-2611-M-110-001)
文摘Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in series for combinations of submarine ridges of different heights and ISW of different amplitudes. The resuhant wave motions were found differing from thee of surface gravity waves. In deeper water, where an ISW of depression-type prevailed, the process of wave breaking displayed downward motion with continuous eddy on the front face of the ridge followed by upward motion towards the apex of the obstacle. Experimental results also suggested that blockage parameter ξ could be applied to classify various degrees of ISW-ridge interaction, i.e., ξ 〈 0.5 for weak interaction, 0.5 〈 ξ 〈 0.7 for moderate interaction, and 0.7 〈 ξ for wave breaking.
基金funded by the National Key Project (No.2011ZX05035)the State Key Basic Research Program of China(No. 2009CB219603)the Project of Scientific Innovation Research of College Graduate in Jiangsu Province (No. CXLX11-0334).
文摘Effective recognition of a coalfield fire area improves fire-fighting efficiency and helps avoid potential geological hazards. Coalfield fire areas are hard to detect accurately using general geophysical methods. This paper describes simulations of shallow, buried coalfield fires based on real geological conditions. Recognizing the coalfield fire by Rayleigh wave is proposed. Four representative geological models are constructed, namely; the non-burning model, the pseudo-burning model, the real-burning model, and the hidden-burning model. Numerical simulation using these models shows many markedly different characteristics between them in terms of Rayleigh wave dispersion and Eigen displacement. These characteristics, as well as the shear wave velocity obtained by inverting the fundamental dispersion, make it possible to distinguish the type of the coalfield fire area and indentify the real and serious coalfield fire area. The results are very helpful for future application of Rayleigh waves for the detection of coalfield fire area.
文摘BACKGROUND： Activation of the sympathetic nervous system plays an important role in regulating cardiovascular actions. P wave parameters can provide general information on central cardiovascular autonomic regulatory responses, which are altered in patients with anxiety disorders and depression. In particular, there are no reports addressing changes in P wave duration and dispersion. OBJECTIVE： To compare the differences in P wave duration and P wave dispersion between patients with anxiety disorders and depression, because patients with anxiety disorders and depression develop abnormal electrocardiograms. DESIGN, TIME AND SETTING： A non-randomized concurrent controlled study was performed. Patients with depression and general anxiety disorders were admitted at the psychiatry outpatient clinics of the Medical Faculty of Duezce University of Turkey between May 2005 and October 2006. PARTICIPANTS： A total of 71 consecutive patients with depression and anxiety disorders, as well as 50 physically and mentally healthy age- and gender-matched controls were selected. METHODS： Electrocardiogram records were obtained at the time of admission to the outpatient clinics. MAIN OUTCOME MEASURES： P wave duration and P wave dispersion were measured. RESULTS： Both the maximum （Prnax） and minimum （Pmin） P wave duration were greater in patients with psychiatric disorders than in healthy controls. Pmax was significantly greater in patients with depression or anxiety disorders （Bonferroni test, P 〈 0.017）. The P wave dispersion was similar between patients and controls （P 〉 0.017）. P waves were similar between panic patients and other anxiety patients. Beck depression results were positively correlated with Prawn and Prnax （r= 0.374, 0.302, P = 0.013, 0.049, respectively）, and not associated with P wave dispersion （P 〉 0.05）. CONCLUSION： Psychiatric disorders are associated with increases in Prnax, but not with P wave dispersion. The P wave changes were associated with the degree of depression.
基金supported by the open fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resource,Institute of Geology,Chinese Academy of Geological Sciences(J1901-16)by the fund from the State Key Laboratory of Geodesy and Earth’s Dynamics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences(S21L6403)。
文摘The crustal structure in Myanmar can provide valuable information for the eastern margin of the ongoing IndoEurasian collision system.We successively performed H-k stacking of the receiver function and joint inversion of the receiver function and surface wave dispersion to invert the crustal thickness(H),shear wave velocity(V_(S)),and the V_(P)/V_(S) ratio(k)beneath nine permanent seismic stations in Myanmar.H was found to increase from 26 km in the south and east of the study area to 51 km in the north and west,and the V_(P)/V_(S) ratio was complex and high.Striking differences in the crust were observed for different tectonic areas.In the Indo-Burma Range,the thick crust(H~51 km)and lower velocities may be related to the accretionary wedge from the Indian Plate.In the Central Myanmar Basin,the thin crust(H=26.9-35.5 km)and complex V_(P)/V_(S) ratio and V_(S) suggest extensional tectonics.In the Eastern Shan Plateau,the relatively thick crust and normal V_(P)/V_(S) ratio are consistent with its location along the western edge of the rigid Sunda Block.
基金scientific projects funded by the National Agency for the Promotion of Science and TechnologyArgentina(ANPCyT)+1 种基金the National University of La Plata,Argentina(UNLP)the National Institute of Oceanography and Experimental Geophysics,Italy(OGS)
文摘In this study, the ambient seismic noise cross-correlation technique is applied to estimate the upper structure of the crust beneath Great Island of Tierra del Fuego（TdF）, Argentina, by the analysis of shortperiod Rayleigh wave group velocities. The island, situated in the southernmost South America, is a key area of investigation among the interaction between the South American and Scotia plates and is considered as a very seismically active one. Through cross-correlating the vertical components of ambient seismic noise registered at four broadband stations in TdF, we were able to extract Rayleigh waves which were used to estimate group velocities in the period band of 2.5-16 s using a timefrequency analysis. Although ambient noise sources are distributed in homogeneously, robust empirical Green＇s functions could be recovered from the cross-correlation of 12 months of ambient noise, The observed group velocities were inverted considering a non-linear iterative damped least-squares inversion procedure and several 1-D shear wave velocity models of the upper crust were obtained.According to the inversion results, the S-wave velocity ranges between 1.75 and 3,7 km/s in the first10 km of crust, depending on the pair of stations considered. These results are in agreement to the major known surface and sub-surface geological and tectonic features known in the area. This study represents the first ambient seismic noise analysis in TdF in order to constraint the upper crust beneath this region.It can also be considered as a successful feasibility study for future analyses with a denser station deployment for a more detailed imaging of structure.
