The effects of two viscoelastic parameters on the thermal convection of a viscoelastic Oldroyd-B fluid in an open-top porous square box with constant heat flux are investigated. The results show that the increase of r...The effects of two viscoelastic parameters on the thermal convection of a viscoelastic Oldroyd-B fluid in an open-top porous square box with constant heat flux are investigated. The results show that the increase of relaxation time is able to destabilize the fluid flow leading to a higher heat transfer rate, while the increase of retardation time tends to stabilize the flow and suppress the heat transfer. The flow bifurcation appears earlier with the increase of the relaxation time and the decrease of the retardation time, re- suiting in more complicated flow patterns in the porous medium.展开更多
Rheological properties are the theoretical basis and the key to common problems in ferrofluid applications,therefore they are expected to be adjustable to satisfy different technical requirements through altering the ...Rheological properties are the theoretical basis and the key to common problems in ferrofluid applications,therefore they are expected to be adjustable to satisfy different technical requirements through altering the microstructure of ferrofluid during the process of preparation.In this paper,Four ferrofluid samples with different magnetic particle size were prepared by controlling the concentration of precursor solution during co-precipitation process and the rheological properties of these samples were investigated.These samples exhibited field-controlled rheological properties.Eternal magnetic field would enhance the formation of microstructures,resulting in an increase of viscosity.While with the increase of shear rate,microstructures tended to be destroyed,causing viscosity to decrease.There were two opposing mechanisms of the influence of precursor solution concentration.On one hand,the reduction of the precursor solution concentration would produce primary magnetic particles of smaller size.But on the other hand,the surfactant became insufficient to completely coat the magnetic particles because of an increased specific surface area,causing the magnetic particles to aggregate and form secondary clustering structures which strongly enhanced the magnetoviscous effect and weakened the viscoelastic effect.展开更多
Within the consistent daily rhythm of human life,intervertebral discs endure a variety of complex loads beyond the influences of gravity and muscle forces,leading to significant morphological changes(in terms of volum...Within the consistent daily rhythm of human life,intervertebral discs endure a variety of complex loads beyond the influences of gravity and muscle forces,leading to significant morphological changes(in terms of volume,area,and height)as well as biomechanical alterations,including an increase in disc stiffness and a decrease in intradiscal pressure.Remarkably,the discs demonstrate an ability to regain their original morphological and biomechanical characteristics after a period of nocturnal rest.The preservation of normal disc function is critically dependent on this recovery phase,which serves to forestall premature disc degeneration.This phenomenon of disc recovery has been extensively documented through numerous in vivo studies employing advanced clinical techniques such as Magnetic Resonance Imaging(MRI),stadiometry,and intradiscal pressure measurement.However,the findings from in vitro studies present a more complex picture,with reports varying between full recovery and only partial recuperation of the disc properties.Moreover,research focusing on degenerated discs in vitro has shed light on the quantifiable impact of degeneration on the disc ability to recover.Fluid dynamics within the disc are considered a primary factor in recovery,yet the disc intricate multiscale structure and its viscoelastic properties also play key roles.These elements interact in complex ways to influence the recovery mechanism,particularly in relation to the overall health of the disc.The objective of this review is to collate,analyze,and critically evaluate the existing body of in vivo and in vitro research on this topic,providing a comprehensive understanding of disc recovery processes.Such understanding offers a blueprint for future advancements in medical treatments and bionic engineering solutions designed to mimic,support,and enhance the natural recovery processes of intervertebral discs.展开更多
The interseismic locking state of tectonic faults is essential for regional seismic hazard assessments.However,it is challenging to obtain this parameter reliably due to the weak deformation and complex model configur...The interseismic locking state of tectonic faults is essential for regional seismic hazard assessments.However,it is challenging to obtain this parameter reliably due to the weak deformation and complex model configurations.To better probe the fault locking state,more reliable physical models and well-covered observations are required.Here we investigate the locking state of the Xianshuihe fault based on a new-developed viscoelastic deformation model.Meanwhile,we combine GPS velocities from 13 new near-field stations and existing stations in this region to improve the spatial resolution.Similar to the theoretical predictions,our results indicate that the elastic model will clearly overestimate the fault locking depth and seismic moment accumulation rate,and the fault slip rate inferred from the elastic model is slightly lower than that from the viscoelastic model.Relying on the locking distribution inferred from the viscoelastic model,we identify four potential asperities on the Xianshuihe fault.More importantly,we find a clear spatial correlation between the fault locking distribution and the rupture extent of historical earthquakes,which indicates that the fault locking state may control the rupture extent and thus the magnitude of earthquakes.In addition,our results show that the 2022 M6.8 Luding earthquake only ruptured the south part of a potential asperity,and the accumulated energy in the northern unruptured area is equivalent to an Mw6.9 earthquake,where the seismic hazard deserves special attention.展开更多
基金Project supported by the National Key Basic Research Development Program of China (973 Program, Grant Nos.2006CB705803, 2013CB531200)
文摘The effects of two viscoelastic parameters on the thermal convection of a viscoelastic Oldroyd-B fluid in an open-top porous square box with constant heat flux are investigated. The results show that the increase of relaxation time is able to destabilize the fluid flow leading to a higher heat transfer rate, while the increase of retardation time tends to stabilize the flow and suppress the heat transfer. The flow bifurcation appears earlier with the increase of the relaxation time and the decrease of the retardation time, re- suiting in more complicated flow patterns in the porous medium.
基金National Natural Science Foundation of China(Grant Nos.51927810,51735006,U1837206)Beijing Municipal Natural Science Foundation of China(Grant No.3182013).
文摘Rheological properties are the theoretical basis and the key to common problems in ferrofluid applications,therefore they are expected to be adjustable to satisfy different technical requirements through altering the microstructure of ferrofluid during the process of preparation.In this paper,Four ferrofluid samples with different magnetic particle size were prepared by controlling the concentration of precursor solution during co-precipitation process and the rheological properties of these samples were investigated.These samples exhibited field-controlled rheological properties.Eternal magnetic field would enhance the formation of microstructures,resulting in an increase of viscosity.While with the increase of shear rate,microstructures tended to be destroyed,causing viscosity to decrease.There were two opposing mechanisms of the influence of precursor solution concentration.On one hand,the reduction of the precursor solution concentration would produce primary magnetic particles of smaller size.But on the other hand,the surfactant became insufficient to completely coat the magnetic particles because of an increased specific surface area,causing the magnetic particles to aggregate and form secondary clustering structures which strongly enhanced the magnetoviscous effect and weakened the viscoelastic effect.
文摘Within the consistent daily rhythm of human life,intervertebral discs endure a variety of complex loads beyond the influences of gravity and muscle forces,leading to significant morphological changes(in terms of volume,area,and height)as well as biomechanical alterations,including an increase in disc stiffness and a decrease in intradiscal pressure.Remarkably,the discs demonstrate an ability to regain their original morphological and biomechanical characteristics after a period of nocturnal rest.The preservation of normal disc function is critically dependent on this recovery phase,which serves to forestall premature disc degeneration.This phenomenon of disc recovery has been extensively documented through numerous in vivo studies employing advanced clinical techniques such as Magnetic Resonance Imaging(MRI),stadiometry,and intradiscal pressure measurement.However,the findings from in vitro studies present a more complex picture,with reports varying between full recovery and only partial recuperation of the disc properties.Moreover,research focusing on degenerated discs in vitro has shed light on the quantifiable impact of degeneration on the disc ability to recover.Fluid dynamics within the disc are considered a primary factor in recovery,yet the disc intricate multiscale structure and its viscoelastic properties also play key roles.These elements interact in complex ways to influence the recovery mechanism,particularly in relation to the overall health of the disc.The objective of this review is to collate,analyze,and critically evaluate the existing body of in vivo and in vitro research on this topic,providing a comprehensive understanding of disc recovery processes.Such understanding offers a blueprint for future advancements in medical treatments and bionic engineering solutions designed to mimic,support,and enhance the natural recovery processes of intervertebral discs.
基金This study was supported by the National Key Research and Development Program of China(Grant No.2017YFC1500501)the National Natural Science Foundation of China(Grant No.41731072).
文摘The interseismic locking state of tectonic faults is essential for regional seismic hazard assessments.However,it is challenging to obtain this parameter reliably due to the weak deformation and complex model configurations.To better probe the fault locking state,more reliable physical models and well-covered observations are required.Here we investigate the locking state of the Xianshuihe fault based on a new-developed viscoelastic deformation model.Meanwhile,we combine GPS velocities from 13 new near-field stations and existing stations in this region to improve the spatial resolution.Similar to the theoretical predictions,our results indicate that the elastic model will clearly overestimate the fault locking depth and seismic moment accumulation rate,and the fault slip rate inferred from the elastic model is slightly lower than that from the viscoelastic model.Relying on the locking distribution inferred from the viscoelastic model,we identify four potential asperities on the Xianshuihe fault.More importantly,we find a clear spatial correlation between the fault locking distribution and the rupture extent of historical earthquakes,which indicates that the fault locking state may control the rupture extent and thus the magnitude of earthquakes.In addition,our results show that the 2022 M6.8 Luding earthquake only ruptured the south part of a potential asperity,and the accumulated energy in the northern unruptured area is equivalent to an Mw6.9 earthquake,where the seismic hazard deserves special attention.
