According to clinical observations and model experiment,we have developed a theoretical mod- el and obtained its mathematical equations to investigate the displacement wave of the blood vessel.The waveform and its occ...According to clinical observations and model experiment,we have developed a theoretical mod- el and obtained its mathematical equations to investigate the displacement wave of the blood vessel.The waveform and its occurrence criterion have been obtained by using perturbation theory and numerical method. The present study suggests that the displacement wave is associated with the blood velocity waveform and the machanical behaviour of the blood vessel,but not with the pressure waveform.The clinical criterion is in agreement with the observations.展开更多
The Yecheng-Shiquanhe profile runs over the western Tibetan Plateau from the south margin of the Tarim Basin, crossing the west Kunlun orogeny, to the east of Karakorum. The authors applied body waves to 3-dimensional...The Yecheng-Shiquanhe profile runs over the western Tibetan Plateau from the south margin of the Tarim Basin, crossing the west Kunlun orogeny, to the east of Karakorum. The authors applied body waves to 3-dimensional inversion of travel time residuals and outlined the deep tectonic pattern of the northwestern Tibetan Plateau. An image was obtained, showing that the Tarim lithosphere is subducted southwards underneath the west Kunlun orogeny at an angle of 40° and a depth of 280 km. Surface structures are well expressed in the image and can be further traced in deeper levels. The prominent finding is that the Gozha Fault and Karakax Fault are likely to join together beyond a depth of ～200 km, which is the very zone of active seismicity.展开更多
Internal waves play a crucial role in ocean mixing, and density perturbation and energy flux are essential quantities to investigate the generation and propagation of internal waves. This paper presents a methodology ...Internal waves play a crucial role in ocean mixing, and density perturbation and energy flux are essential quantities to investigate the generation and propagation of internal waves. This paper presents a methodology for calculating density perturbation and energy flux of internal waves only using a velocity field that is based on linearized equations for internal waves. The method was tested by numerical simulations of internal waves generated by tidal flowing over a Gaussian topography in a stratified fluid. The density perturbations and energy fluxes determined using our method that only used velocity data agreed with density perturbations and energy fluxes determined by the equation of state based on temperature data. The mean relative error(MRE) and root mean square error(RMSE) between the two methods were lower than 5% and 10% respectively. In addition, an experiment was performed to exam our method using the velocity field measured by Particle Image Velocimetry(PIV), and the setup of the experiment is consistent with the numerical model. The results of the experiments calculated by the methods using PIV data were also generally equal to those of the numerical model.展开更多
The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. Th...The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. The velocity and pressure distributions are solved successively by different numerical methods with the zeroth-order and first-order equation. Agreement in results is found with the present method and software ANSYS-CFX, which illustrates the applicability of perturbation method in solving complicated flow field inside small gaps.展开更多
PS converted-waves （C-waves） have been commonly used to image through gas clouds but the C-wave imaging may also be degraded by the diodic effect introduced by the gas cloud. It may be compensated for using a veloci...PS converted-waves （C-waves） have been commonly used to image through gas clouds but the C-wave imaging may also be degraded by the diodic effect introduced by the gas cloud. It may be compensated for using a velocity perturbation method which decouples the diodic moveout into two parts： the base velocity and the velocity perturbation. Gas clouds are widely distributed in the Sanhu area in the Qaidam basin of northwest China which is rich in natural gas. A land 2D3C seismic dataset is analyzed from the Sanhu area and significant diodic effects are observed in the data which harm the C-wave imaging. The diodic correction is applied to this data and the resultant C-wave imaging and the details of the reservoir structure are significantly improved. The diodic moveout plays an important role in working out the residu~ shear wave statics and the association of diodie correction and shear wave residual statics computation is a key step of C-wave high fidelity imaging in the gas cloud area. Finally, the new process workflow with diodic moveout is given.展开更多
文摘According to clinical observations and model experiment,we have developed a theoretical mod- el and obtained its mathematical equations to investigate the displacement wave of the blood vessel.The waveform and its occurrence criterion have been obtained by using perturbation theory and numerical method. The present study suggests that the displacement wave is associated with the blood velocity waveform and the machanical behaviour of the blood vessel,but not with the pressure waveform.The clinical criterion is in agreement with the observations.
基金suppoted by the Ministry of Land and Res ources,PRC(Grant No.20001010201)and CNRS of France.
文摘The Yecheng-Shiquanhe profile runs over the western Tibetan Plateau from the south margin of the Tarim Basin, crossing the west Kunlun orogeny, to the east of Karakorum. The authors applied body waves to 3-dimensional inversion of travel time residuals and outlined the deep tectonic pattern of the northwestern Tibetan Plateau. An image was obtained, showing that the Tarim lithosphere is subducted southwards underneath the west Kunlun orogeny at an angle of 40° and a depth of 280 km. Surface structures are well expressed in the image and can be further traced in deeper levels. The prominent finding is that the Gozha Fault and Karakax Fault are likely to join together beyond a depth of ～200 km, which is the very zone of active seismicity.
基金supported by the National Key Research and Development Program of China (No. 2017YFA0604103)the Natural Science Foundation of China (NSFC) (No. 41476001)
文摘Internal waves play a crucial role in ocean mixing, and density perturbation and energy flux are essential quantities to investigate the generation and propagation of internal waves. This paper presents a methodology for calculating density perturbation and energy flux of internal waves only using a velocity field that is based on linearized equations for internal waves. The method was tested by numerical simulations of internal waves generated by tidal flowing over a Gaussian topography in a stratified fluid. The density perturbations and energy fluxes determined using our method that only used velocity data agreed with density perturbations and energy fluxes determined by the equation of state based on temperature data. The mean relative error(MRE) and root mean square error(RMSE) between the two methods were lower than 5% and 10% respectively. In addition, an experiment was performed to exam our method using the velocity field measured by Particle Image Velocimetry(PIV), and the setup of the experiment is consistent with the numerical model. The results of the experiments calculated by the methods using PIV data were also generally equal to those of the numerical model.
文摘The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. The velocity and pressure distributions are solved successively by different numerical methods with the zeroth-order and first-order equation. Agreement in results is found with the present method and software ANSYS-CFX, which illustrates the applicability of perturbation method in solving complicated flow field inside small gaps.
基金supported by the National Natural Science Foundation of China (No. 41074080)the Important National Science & Technology Specific Projects (No. 2011ZX05019-008)
文摘PS converted-waves （C-waves） have been commonly used to image through gas clouds but the C-wave imaging may also be degraded by the diodic effect introduced by the gas cloud. It may be compensated for using a velocity perturbation method which decouples the diodic moveout into two parts： the base velocity and the velocity perturbation. Gas clouds are widely distributed in the Sanhu area in the Qaidam basin of northwest China which is rich in natural gas. A land 2D3C seismic dataset is analyzed from the Sanhu area and significant diodic effects are observed in the data which harm the C-wave imaging. The diodic correction is applied to this data and the resultant C-wave imaging and the details of the reservoir structure are significantly improved. The diodic moveout plays an important role in working out the residu~ shear wave statics and the association of diodie correction and shear wave residual statics computation is a key step of C-wave high fidelity imaging in the gas cloud area. Finally, the new process workflow with diodic moveout is given.
