The observation of GW150914 gave a new independent measurement of the luminosity distance of a gravitational wave event. In this paper, we constrain the anisotropy of the Universe by using gravitational wave events.We...The observation of GW150914 gave a new independent measurement of the luminosity distance of a gravitational wave event. In this paper, we constrain the anisotropy of the Universe by using gravitational wave events.We simulate hundreds of events of binary neutron star merger that may be observed by the Einstein Telescope. Full simulation of the production process of gravitational wave data is employed. We find that 200 binary neutron star merging events with the redshift in (0,1) observed by the Einstein Telescope may constrain the anisotropy with an accuracy comparable to that from the Union2.1 supernovae. This result shows that gravitational waves can be a powerful tool for investigating cosmological anisotropy.展开更多
Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases.As a key feature of microstructure,the morphology of the coherent particles...Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases.As a key feature of microstructure,the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys.This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation.We found that the ferrite grain tends to grow into an elongated plate-like shape,independent of its initial confi guration.The fi nal shape of the ferrite is closely related to the misfi t between the two phases,with the longest direction and the broad facet of the plate being,respectively,consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC)method.The strain energy calculation in the framework of Eshelby’s inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable.It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.展开更多
Calcite has a highly anisotropic thermal expansion coefficient,and repeated heating and cooling cycles can potentially destabilize chalks by breaking cement bonds between neighboring particles.Based on tensile strengt...Calcite has a highly anisotropic thermal expansion coefficient,and repeated heating and cooling cycles can potentially destabilize chalks by breaking cement bonds between neighboring particles.Based on tensile strength measurements,we investigated how temperature cycles induce weakening of chalk.Tensile strength tests were performed on chalk specimens sampled from Kansas(USA)and Mons(Belgium),each with differing amounts of contact cement.Samples of the two chalk types were tested in dry and water-saturated states,and then exposed to 0,15,and 30 temperature cycles in order to find out under what circumstances thermally induced tensile strength reduction occurs.The testing results show that the dry samples were not influenced by temperature cycling in either of the chalk types.However,in the water-saturated state,tensile strength is increasingly reduced with progressive numbers of temperature cycles for both chalk samples,especially for the more cemented Kansas chalk.The Kansas chalk demonstrated higher initial tensile strength compared to the less cemented Mons chalk,but the strength of both chalks was reduced by the same relative proportion when undergoing thermal cycles in the water-saturated state.展开更多
Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is...Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is effectively improved.It helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas,since towns tend to be built where terrain is more flat,due to the clay deposits.There are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting,to use micro-cements and micro-silica additives.The use of highpressure injection may cause joint jacking,but this is local in extent when the rapid pressure decay away from an injection hole is understood.This effect is variable and depends on the geometrical parameters of the joints.This pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the injection hole has ceased.The latter can cause damage to the grouting already achieved.Simplified methods of estimating mean hydraulic apertures(e)from Lugeon testing are described,and from more sophisticated three-dimensional(3D)permeability measurement.The estimation of the larger mean physical joint apertures(E)is based on the joint roughness coefficient(JRC).Comparison is then made with the empirical aperture-particle size criterion E>4d95,where d95 represents almost the largest cement particle size.Depending on joint set orientations and on the available micro-cements,the decision must be made of which range of pre-injection pressure should be aimed for,using successive reductions of the water-cement ratio w/c.More simple estimation of permeability,also with depth dependence,can be made with the empirical link between a modified rock mass quality Q and permeability,which is termed QH2O.The value of this parameter can be based on core-logging or intunnel face logging.The 3D before-and-after-grouting permeability measurements have been used to justify the quantification of rock mass qua展开更多
Vascular diseases such as aneurysm,hemadostenosis,aortic dissection are the primary causes of people’s death around world.As a result,it is significant to improve our knowledge about them,which can help to treat the ...Vascular diseases such as aneurysm,hemadostenosis,aortic dissection are the primary causes of people’s death around world.As a result,it is significant to improve our knowledge about them,which can help to treat the disease.Measuring the hemodynamic factor like the blood pressure,the wall shear stress(WSS)and the oscillatory shear index(OSI)is,however,still beyond the capabilities of in-vivo measurement techniques.So the use of mathematical models and numerical simulations for the studies of the blood flow in arteries and,in general,of the cardiovascular system,both in physiological and pathological conditions,has received an increasing attention in the biomedical community during the last two decades.Indeed,such studies aims at enhancing the current knowledge of the physiology of the cardiovascular system,as well as providing reliable tools for the medical doctors to predict the natural course of pathologies and,possibly,the occurrence of cardiovascular accidents.The computational vascular fluid-structure interaction(FSI)methodology is a numerical simulation method which is used to explain the hemodynamic factors.The WSS on the luminal wall and the mechanical stress in the vascular wall are directly related to the location of the lesion,and the blood flow strongly interacts with the vascular wall motion.The arterial wall continually adapts to the charge of its mechanical environment(due to,for example,growth,atrophy,remodelling,repair,ageing,and disease)and consequently undergoes several irreversible processes.Primary acute mechanisms of vascularFSI numerical simulation seem to be associated with(1)the arterial histology and the patient-specific complex geometry,(2)the typical mechanical properties of the layer,(3)properties of the blood is assumed as Newtonian fluid or non-Newtonian fluid based on the scale ofthe diameter of a vessel,(4)residual stress in the zero-pressure configuration.The arterial system naturally function under permanent physiological loading conditions.Fung defined the residual stress and展开更多
The activity and stability of Cu nanostructures strongly depend on their sizes,morphology and structures.Here we report the preparation of two-dimensional(2 D)Cu@Cu-BTC core-shell nanosheets(NSs).The thickness of the ...The activity and stability of Cu nanostructures strongly depend on their sizes,morphology and structures.Here we report the preparation of two-dimensional(2 D)Cu@Cu-BTC core-shell nanosheets(NSs).The thickness of the Cu NSs could be tuned to sub-10 nm through a mild etching process,in which the Cu-BTC in situ grow along with the oxidation on the surface of the Cu NSs.This unique strategy can also be extended to synthesize one-dimensional(1 D)Cu@Cu-BTC nanowires(NWs).Furthermore,the obtained Cu@Cu-BTC NSs could be applied as an effective material to the memory device with the write-onceread-many times(WORM)behavior and the high ION/I(OFF)ratio(>2.7×103).展开更多
In this paper,the authors investigate the differences between the dose results calculated with AAA(Anisotropic Analytical Algorithm)algorithm in Eclipse 13.0 treatment planning system,which has just commissioned,with ...In this paper,the authors investigate the differences between the dose results calculated with AAA(Anisotropic Analytical Algorithm)algorithm in Eclipse 13.0 treatment planning system,which has just commissioned,with the measured doses.The AAA algorithm in the Eclipse software is used to calculate the absolute dose,relative dose in profile line,and percent depth dose of some specific field size in Blue Phantom.The calculated dose results were compared with measured dose based on Technical Reports Series No.430 of International Atomic Energy Agency(IAEA No.430).The authors have used CC13 ion chamber,Famer Chamber,water phantom,and Omnipro software to measure relative,absolute doses of these fields size.The AAA algorithm was also used to calculate the doses in IMRT(Intensity Modulated Radiotherapy)plan of fifty head and neck cancer patients.These IMRT plans were controlled quality in some points with plastic phantom,and famer chamber FC65.The differences between calculated dose,and measured doses are in the limit of IAEA 430 report.The results of the QA IMRT plan processing are fitting with ESTRO(European Society Therapeutic Radiation Oncology)Booklet No.9.展开更多
In this paper, a combined viscoelasticity-viscoplasticity model, coupled with anisotropic damage and moisture effects, is developed for short fiber reinforced polymers (SFRPs) with different fiber contents and subject...In this paper, a combined viscoelasticity-viscoplasticity model, coupled with anisotropic damage and moisture effects, is developed for short fiber reinforced polymers (SFRPs) with different fiber contents and subjected to a variety of strain rates. In our model, a rate-dependent yield surface for the matrix phase is employed to identify initial yielding of the material. When an SFRP is loaded at small deformation before yielding, its viscoelastic behavior can be described using the generalized Maxwell model, while when plasticity occurs, a scalar internal state variable (ISV) is used to capture the hardening behavior caused by the polymeric constituent of the composite. The material degradation due to the moisture absorption of the composite is modeled by employing another type of ISV with different evolution equations. The complicated damage state of the SFRPs is captured by a second rank tensor, which is further decomposed to model the subscale damage mechanisms of micro-voids/cracks nucleation, growth and coalescence. It is concluded that the proposed constitutive model can be used to accurately describe complicated behaviors of SFRPs because the results predicted from the model are in good agreement with the experimental data.展开更多
Background Tetralogy of Fallot(TOF)is the most common cyanotic heart defect,accounting for 10%of all congenital defects.Pulmonary valve stenosis(PVS)is one common right ventricular outflow tract obstruction problem in...Background Tetralogy of Fallot(TOF)is the most common cyanotic heart defect,accounting for 10%of all congenital defects.Pulmonary valve stenosis(PVS)is one common right ventricular outflow tract obstruction problem in patients with TOF.Congenital bicuspid pulmonary valve(BPV)is a condition of valvular stenosis,which morphologic feature is the presence of only two pulmonary leaflets instead of the normal tri-leaflet.Congenitally BPV are uncommon and the occurrence is often associated with TOF.Methods The three-dimensional geometric reconstruction of pulmonary root(PR)were based on well-accepted mathematical analytic models with physiological parameters obtained from a typical sample of the pulmonary root used in clinical surgery.The PR geometry included valvular leaflets,sinuses,interleaflet triangles and annulus.The dynamic computational models of normal PR with tri-leaflet and PR with BPV in patients with TOF were developed to investigate the effect of geometric structure of BPV on valve stress and strain distributions and the geometric orifice area.Mechanical properties of pulmonary valve leaflet were obtained from biaxial testing of human pulmonary valve left leaflet,and characterized by an anisotropic Mooney-Rivlin model.The complete cardiac cycle was simulated to observe valve leaflet dynamic stress and strain behaviors.Results Our results indicated that stress/strain distribution patterns of normal tri-leaflet pulmonary valve(TPV)and the BPV were different on valve leaflets when the valve was fully open,but they were similar when valves were completely closed.When the valve was fully open,the BPV maximum stress value on the leaflets was 218.1 kPa,which was 128.0%higher than of the normal TPV value(95.6 kPa),and BPV maximum strain value on the leaflets was 70.7%higher than of the normal TPV.The location of the maximum stress from TPV and BPV were also different,which were found at the bottom of the valve near the leaflet attachment for TPV and the vicinity of cusp of the fusion of two leaflets for BPV,respec展开更多
The direct numerical simulation (DNS) is carried out for the incompressible viscous turbulent flows over an anisotropic porous wall. Effects of the anisotropic porous wall on turbulence modifications as well as on the...The direct numerical simulation (DNS) is carried out for the incompressible viscous turbulent flows over an anisotropic porous wall. Effects of the anisotropic porous wall on turbulence modifications as well as on the turbulent drag reduction are investigated. The simulation is carried out at a friction Reynolds number of 180, which is based on the averaged friction velocity at the interface between the porous medium and the clear fluid domain. The depth of the porous layer ranges from 0.9 to 54 viscous units. The permeability in the spanwise direction is set to be lower than the other directions in the present simulation. The maximum drag reduction obtained is about 15.3% which occurs for a depth of 9 viscous units. The increasing of drag is addressed when the depth of the porous layer is more than 25 wall units. The thinner porous layer restricts the spanwise extension of the streamwise vortices which suppresses the bursting events near the wall. However, for the thicker porous layer, the wall-normal fluctuations are enhanced due to the weakening of the wall-blocking effect which can trigger strong turbulent structures near the wall.展开更多
Direct numerical simulation of a spatially developing turbulent boundary layer over a compliant wall with anisotropic wall material properties is performed. The Reynolds number varies from 300 to approximately 860 alo...Direct numerical simulation of a spatially developing turbulent boundary layer over a compliant wall with anisotropic wall material properties is performed. The Reynolds number varies from 300 to approximately 860 along the streamwise direction, based on the external flow velocity and the momentum thickness. Eight typical cases are selected for numerical investigation under the guidance of the monoharmonic analysis. The instantaneous flow fields exhibit the traveling wavy motion of the compliant wall, and the frequency-wavenumber power spectrum of wall pressure fluctuation is computed to quantify the mutual influence of the wall compliance and the turbulent flow at different wave numbers. It is shown that the Reynolds shear stress and the pressure fluctuation are generally enhanced by the wall compliance with the parameters considered in the present study. A dynamical decomposition of the skin-friction coefficient is derived, and a new term (CW) appears due to the wall-induced Reynolds shear stress. The influence of the anisotropic compliant wall motion on the turbulent boundary layer through the wall-induced negative Reynolds shear stress is discussed. To elucidate the underlying mechanism, the budget analysis of the Reynolds stresses transportation is further carried out. The impact of the wall compliance on the turbulent flow is disclosed by examining the variations of the diffusion and velocity-pressure correlation terms. It is shown that increase of the Reynolds stresses inside the flow domain is caused by enhancement of the velocity-pressure correlation term, possibly through the long-range influence of the wall compliance on the pressure field, rather than diffusion of the wall-induced Reynolds shear stress into the fluid flow.展开更多
We demonstrate theoretically the anisotropic quantum transport of electrons through an electric field on monolayer and multilayer phosphorene. Using the long-wavelength Hamiltonian with continuum approximation, we fin...We demonstrate theoretically the anisotropic quantum transport of electrons through an electric field on monolayer and multilayer phosphorene. Using the long-wavelength Hamiltonian with continuum approximation, we find that the transmission probability for transport through an electric field is an oscillating function of incident angle, electric field intensity, as well as the incident energy of electrons. By tuning the electric field intensity and incident angle, the channels can be transited from opaque to transparent. The conductance through the quantum waveguides depends sensitively on the transport direction because of the anisotropic effective mass, and the anisotropy of the conductance can be tuned by the electric field intensity and the number of layers. These behaviors provide us an efficient way to control the transport of phosphorene-based microstructures.展开更多
We consider three-dimensional incompressible Navier-Stokes equations(NS) with different viscous coefficients in the vertical and horizontal variables. In particular, when one of these viscous coefficients is large eno...We consider three-dimensional incompressible Navier-Stokes equations(NS) with different viscous coefficients in the vertical and horizontal variables. In particular, when one of these viscous coefficients is large enough compared with the initial data, we prove the global well-posedness of this system. In fact, we obtain the existence of a global strong solution to(NS) when the initial data verifies an anisotropic smallness condition which takes into account the different roles of the horizontal and vertical viscosity.展开更多
Two-dimensional(2D) anisotropic materials, such as B-P, B-As, GeSe, GeAs, ReSe2, KP15 and their hybrid systems, exhibit unique crystal structures and extraordinary anisotropy. This review presents a comprehensive comp...Two-dimensional(2D) anisotropic materials, such as B-P, B-As, GeSe, GeAs, ReSe2, KP15 and their hybrid systems, exhibit unique crystal structures and extraordinary anisotropy. This review presents a comprehensive comparison of various 2D anisotropic crystals as well as relevant FETs and photodetectors, especially on their particular anisotropy in optical and electrical properties. First, the structure of typical 2D anisotropic crystal as well as the analysis of structural anisotropy is provided. Then, recent researches on anisotropic Raman spectra are reviewed. Particularly, a brief measurement principle of Raman spectra under three typical polarized measurement configurations is introduced. Finally, recent progress on the electrical and photoelectrical properties of FETs and polarization-sensitive photodetectors based on 2D anisotropic materials is summarized for the comparison between different 2D anisotropic materials. Beyond the high response speed, sensitivity and on/off ratio, these 2D anisotropic crystals exhibit highly conduction ratio and dichroic ratio which can be applied in terms of polarization sensors, polarization spectroscopy imaging, optical radar and remote sensing.展开更多
基金grants from NSFC(11675182,11690022,11603005,1177503.
文摘The observation of GW150914 gave a new independent measurement of the luminosity distance of a gravitational wave event. In this paper, we constrain the anisotropy of the Universe by using gravitational wave events.We simulate hundreds of events of binary neutron star merger that may be observed by the Einstein Telescope. Full simulation of the production process of gravitational wave data is employed. We find that 200 binary neutron star merging events with the redshift in (0,1) observed by the Einstein Telescope may constrain the anisotropy with an accuracy comparable to that from the Union2.1 supernovae. This result shows that gravitational waves can be a powerful tool for investigating cosmological anisotropy.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51471097 and 51671111)the National Key Research and Development Program of China (Grant No. 2016YFB0701304).
文摘Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases.As a key feature of microstructure,the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys.This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation.We found that the ferrite grain tends to grow into an elongated plate-like shape,independent of its initial confi guration.The fi nal shape of the ferrite is closely related to the misfi t between the two phases,with the longest direction and the broad facet of the plate being,respectively,consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC)method.The strain energy calculation in the framework of Eshelby’s inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable.It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.
文摘Calcite has a highly anisotropic thermal expansion coefficient,and repeated heating and cooling cycles can potentially destabilize chalks by breaking cement bonds between neighboring particles.Based on tensile strength measurements,we investigated how temperature cycles induce weakening of chalk.Tensile strength tests were performed on chalk specimens sampled from Kansas(USA)and Mons(Belgium),each with differing amounts of contact cement.Samples of the two chalk types were tested in dry and water-saturated states,and then exposed to 0,15,and 30 temperature cycles in order to find out under what circumstances thermally induced tensile strength reduction occurs.The testing results show that the dry samples were not influenced by temperature cycling in either of the chalk types.However,in the water-saturated state,tensile strength is increasingly reduced with progressive numbers of temperature cycles for both chalk samples,especially for the more cemented Kansas chalk.The Kansas chalk demonstrated higher initial tensile strength compared to the less cemented Mons chalk,but the strength of both chalks was reduced by the same relative proportion when undergoing thermal cycles in the water-saturated state.
文摘Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is effectively improved.It helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas,since towns tend to be built where terrain is more flat,due to the clay deposits.There are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting,to use micro-cements and micro-silica additives.The use of highpressure injection may cause joint jacking,but this is local in extent when the rapid pressure decay away from an injection hole is understood.This effect is variable and depends on the geometrical parameters of the joints.This pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the injection hole has ceased.The latter can cause damage to the grouting already achieved.Simplified methods of estimating mean hydraulic apertures(e)from Lugeon testing are described,and from more sophisticated three-dimensional(3D)permeability measurement.The estimation of the larger mean physical joint apertures(E)is based on the joint roughness coefficient(JRC).Comparison is then made with the empirical aperture-particle size criterion E>4d95,where d95 represents almost the largest cement particle size.Depending on joint set orientations and on the available micro-cements,the decision must be made of which range of pre-injection pressure should be aimed for,using successive reductions of the water-cement ratio w/c.More simple estimation of permeability,also with depth dependence,can be made with the empirical link between a modified rock mass quality Q and permeability,which is termed QH2O.The value of this parameter can be based on core-logging or intunnel face logging.The 3D before-and-after-grouting permeability measurements have been used to justify the quantification of rock mass qua
基金supported by the National Natural Science Foundation of China(11732001).
文摘Vascular diseases such as aneurysm,hemadostenosis,aortic dissection are the primary causes of people’s death around world.As a result,it is significant to improve our knowledge about them,which can help to treat the disease.Measuring the hemodynamic factor like the blood pressure,the wall shear stress(WSS)and the oscillatory shear index(OSI)is,however,still beyond the capabilities of in-vivo measurement techniques.So the use of mathematical models and numerical simulations for the studies of the blood flow in arteries and,in general,of the cardiovascular system,both in physiological and pathological conditions,has received an increasing attention in the biomedical community during the last two decades.Indeed,such studies aims at enhancing the current knowledge of the physiology of the cardiovascular system,as well as providing reliable tools for the medical doctors to predict the natural course of pathologies and,possibly,the occurrence of cardiovascular accidents.The computational vascular fluid-structure interaction(FSI)methodology is a numerical simulation method which is used to explain the hemodynamic factors.The WSS on the luminal wall and the mechanical stress in the vascular wall are directly related to the location of the lesion,and the blood flow strongly interacts with the vascular wall motion.The arterial wall continually adapts to the charge of its mechanical environment(due to,for example,growth,atrophy,remodelling,repair,ageing,and disease)and consequently undergoes several irreversible processes.Primary acute mechanisms of vascularFSI numerical simulation seem to be associated with(1)the arterial histology and the patient-specific complex geometry,(2)the typical mechanical properties of the layer,(3)properties of the blood is assumed as Newtonian fluid or non-Newtonian fluid based on the scale ofthe diameter of a vessel,(4)residual stress in the zero-pressure configuration.The arterial system naturally function under permanent physiological loading conditions.Fung defined the residual stress and
基金the National Key R&D Program of China(No.2017YFA0700104)National Natural Science Foundation of China(Nos.21571169,21871238)+2 种基金Fundamental Research Funds for the Central Universities(No.WK2060190081)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2018494)Young Elite Scientists Sponsorship Program by CAST(No.2016QNRC001).
文摘The activity and stability of Cu nanostructures strongly depend on their sizes,morphology and structures.Here we report the preparation of two-dimensional(2 D)Cu@Cu-BTC core-shell nanosheets(NSs).The thickness of the Cu NSs could be tuned to sub-10 nm through a mild etching process,in which the Cu-BTC in situ grow along with the oxidation on the surface of the Cu NSs.This unique strategy can also be extended to synthesize one-dimensional(1 D)Cu@Cu-BTC nanowires(NWs).Furthermore,the obtained Cu@Cu-BTC NSs could be applied as an effective material to the memory device with the write-onceread-many times(WORM)behavior and the high ION/I(OFF)ratio(>2.7×103).
文摘In this paper,the authors investigate the differences between the dose results calculated with AAA(Anisotropic Analytical Algorithm)algorithm in Eclipse 13.0 treatment planning system,which has just commissioned,with the measured doses.The AAA algorithm in the Eclipse software is used to calculate the absolute dose,relative dose in profile line,and percent depth dose of some specific field size in Blue Phantom.The calculated dose results were compared with measured dose based on Technical Reports Series No.430 of International Atomic Energy Agency(IAEA No.430).The authors have used CC13 ion chamber,Famer Chamber,water phantom,and Omnipro software to measure relative,absolute doses of these fields size.The AAA algorithm was also used to calculate the doses in IMRT(Intensity Modulated Radiotherapy)plan of fifty head and neck cancer patients.These IMRT plans were controlled quality in some points with plastic phantom,and famer chamber FC65.The differences between calculated dose,and measured doses are in the limit of IAEA 430 report.The results of the QA IMRT plan processing are fitting with ESTRO(European Society Therapeutic Radiation Oncology)Booklet No.9.
基金the Mississippi NASA EPSCoR through its Research Infrastructure Development (RID) Program.
文摘In this paper, a combined viscoelasticity-viscoplasticity model, coupled with anisotropic damage and moisture effects, is developed for short fiber reinforced polymers (SFRPs) with different fiber contents and subjected to a variety of strain rates. In our model, a rate-dependent yield surface for the matrix phase is employed to identify initial yielding of the material. When an SFRP is loaded at small deformation before yielding, its viscoelastic behavior can be described using the generalized Maxwell model, while when plasticity occurs, a scalar internal state variable (ISV) is used to capture the hardening behavior caused by the polymeric constituent of the composite. The material degradation due to the moisture absorption of the composite is modeled by employing another type of ISV with different evolution equations. The complicated damage state of the SFRPs is captured by a second rank tensor, which is further decomposed to model the subscale damage mechanisms of micro-voids/cracks nucleation, growth and coalescence. It is concluded that the proposed constitutive model can be used to accurately describe complicated behaviors of SFRPs because the results predicted from the model are in good agreement with the experimental data.
基金supported in part by National Sciences Foundation of China grants(11672001,81571691 and 81771844).
文摘Background Tetralogy of Fallot(TOF)is the most common cyanotic heart defect,accounting for 10%of all congenital defects.Pulmonary valve stenosis(PVS)is one common right ventricular outflow tract obstruction problem in patients with TOF.Congenital bicuspid pulmonary valve(BPV)is a condition of valvular stenosis,which morphologic feature is the presence of only two pulmonary leaflets instead of the normal tri-leaflet.Congenitally BPV are uncommon and the occurrence is often associated with TOF.Methods The three-dimensional geometric reconstruction of pulmonary root(PR)were based on well-accepted mathematical analytic models with physiological parameters obtained from a typical sample of the pulmonary root used in clinical surgery.The PR geometry included valvular leaflets,sinuses,interleaflet triangles and annulus.The dynamic computational models of normal PR with tri-leaflet and PR with BPV in patients with TOF were developed to investigate the effect of geometric structure of BPV on valve stress and strain distributions and the geometric orifice area.Mechanical properties of pulmonary valve leaflet were obtained from biaxial testing of human pulmonary valve left leaflet,and characterized by an anisotropic Mooney-Rivlin model.The complete cardiac cycle was simulated to observe valve leaflet dynamic stress and strain behaviors.Results Our results indicated that stress/strain distribution patterns of normal tri-leaflet pulmonary valve(TPV)and the BPV were different on valve leaflets when the valve was fully open,but they were similar when valves were completely closed.When the valve was fully open,the BPV maximum stress value on the leaflets was 218.1 kPa,which was 128.0%higher than of the normal TPV value(95.6 kPa),and BPV maximum strain value on the leaflets was 70.7%higher than of the normal TPV.The location of the maximum stress from TPV and BPV were also different,which were found at the bottom of the valve near the leaflet attachment for TPV and the vicinity of cusp of the fusion of two leaflets for BPV,respec
基金the National Natural Science Foundation of China (Nos. 11572183, 91852111, and 11825204)the Program of Shanghai Municipal Education Commission (No. 2019-01-07-00- 09-E00018).
文摘The direct numerical simulation (DNS) is carried out for the incompressible viscous turbulent flows over an anisotropic porous wall. Effects of the anisotropic porous wall on turbulence modifications as well as on the turbulent drag reduction are investigated. The simulation is carried out at a friction Reynolds number of 180, which is based on the averaged friction velocity at the interface between the porous medium and the clear fluid domain. The depth of the porous layer ranges from 0.9 to 54 viscous units. The permeability in the spanwise direction is set to be lower than the other directions in the present simulation. The maximum drag reduction obtained is about 15.3% which occurs for a depth of 9 viscous units. The increasing of drag is addressed when the depth of the porous layer is more than 25 wall units. The thinner porous layer restricts the spanwise extension of the streamwise vortices which suppresses the bursting events near the wall. However, for the thicker porous layer, the wall-normal fluctuations are enhanced due to the weakening of the wall-blocking effect which can trigger strong turbulent structures near the wall.
基金the National Natural Science Foundation of China (Grants 11772172 and 11490551).
文摘Direct numerical simulation of a spatially developing turbulent boundary layer over a compliant wall with anisotropic wall material properties is performed. The Reynolds number varies from 300 to approximately 860 along the streamwise direction, based on the external flow velocity and the momentum thickness. Eight typical cases are selected for numerical investigation under the guidance of the monoharmonic analysis. The instantaneous flow fields exhibit the traveling wavy motion of the compliant wall, and the frequency-wavenumber power spectrum of wall pressure fluctuation is computed to quantify the mutual influence of the wall compliance and the turbulent flow at different wave numbers. It is shown that the Reynolds shear stress and the pressure fluctuation are generally enhanced by the wall compliance with the parameters considered in the present study. A dynamical decomposition of the skin-friction coefficient is derived, and a new term (CW) appears due to the wall-induced Reynolds shear stress. The influence of the anisotropic compliant wall motion on the turbulent boundary layer through the wall-induced negative Reynolds shear stress is discussed. To elucidate the underlying mechanism, the budget analysis of the Reynolds stresses transportation is further carried out. The impact of the wall compliance on the turbulent flow is disclosed by examining the variations of the diffusion and velocity-pressure correlation terms. It is shown that increase of the Reynolds stresses inside the flow domain is caused by enhancement of the velocity-pressure correlation term, possibly through the long-range influence of the wall compliance on the pressure field, rather than diffusion of the wall-induced Reynolds shear stress into the fluid flow.
基金Supported by the National Natural Science Foundation of China under Grant No 11374002the Scientific Research Fund of Hunan Provincial Education Department under Grant No 17A001the Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering of Changsha University of Science and Technology.
文摘We demonstrate theoretically the anisotropic quantum transport of electrons through an electric field on monolayer and multilayer phosphorene. Using the long-wavelength Hamiltonian with continuum approximation, we find that the transmission probability for transport through an electric field is an oscillating function of incident angle, electric field intensity, as well as the incident energy of electrons. By tuning the electric field intensity and incident angle, the channels can be transited from opaque to transparent. The conductance through the quantum waveguides depends sensitively on the transport direction because of the anisotropic effective mass, and the anisotropy of the conductance can be tuned by the electric field intensity and the number of layers. These behaviors provide us an efficient way to control the transport of phosphorene-based microstructures.
基金supported by the Agence Nationale de la Recherche,Project IFSMACS(Grant No.ANR-15-CE40-0010)supported by National Natural Science Foundation of China(Grant Nos.11371347 and 11688101)Morningside Center of Mathematics of the Chinese Academy of Sciences and Innovation Grant from National Center for Mathematics and Interdisciplinary Sciences.
文摘We consider three-dimensional incompressible Navier-Stokes equations(NS) with different viscous coefficients in the vertical and horizontal variables. In particular, when one of these viscous coefficients is large enough compared with the initial data, we prove the global well-posedness of this system. In fact, we obtain the existence of a global strong solution to(NS) when the initial data verifies an anisotropic smallness condition which takes into account the different roles of the horizontal and vertical viscosity.
基金the National Natural Science Foundation of China (Grant Nos. 61622406, 61571415, 11874350, 11434010)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000).
文摘Two-dimensional(2D) anisotropic materials, such as B-P, B-As, GeSe, GeAs, ReSe2, KP15 and their hybrid systems, exhibit unique crystal structures and extraordinary anisotropy. This review presents a comprehensive comparison of various 2D anisotropic crystals as well as relevant FETs and photodetectors, especially on their particular anisotropy in optical and electrical properties. First, the structure of typical 2D anisotropic crystal as well as the analysis of structural anisotropy is provided. Then, recent researches on anisotropic Raman spectra are reviewed. Particularly, a brief measurement principle of Raman spectra under three typical polarized measurement configurations is introduced. Finally, recent progress on the electrical and photoelectrical properties of FETs and polarization-sensitive photodetectors based on 2D anisotropic materials is summarized for the comparison between different 2D anisotropic materials. Beyond the high response speed, sensitivity and on/off ratio, these 2D anisotropic crystals exhibit highly conduction ratio and dichroic ratio which can be applied in terms of polarization sensors, polarization spectroscopy imaging, optical radar and remote sensing.