The coupled motion of two flexible bodies with different lengths immersed in moving fluid is studied numerically. The flapping frequency, flapping amplitude and average drag coefficient of each body are calculated and...The coupled motion of two flexible bodies with different lengths immersed in moving fluid is studied numerically. The flapping frequency, flapping amplitude and average drag coefficient of each body are calculated and the influences of the arranging manner and separation distance are analyzed. In our simulation, when placed in the flow individually, the flexible body with a longer length will flap in period and the shorter one will maintain still straightly in the flow direction. The numerical results show that, two different flexible structures near placed in moving flow would strongly interact. When they are placed side by side, the existence of the stable shorter flexible body will restrain the flapping of the longer one while the existence of the longer flexible body may also induce the shorter one to flap synchronously. When placed in tandem with the shorter flexible body in upstream, the flapping of the longer one in downstream will be obviously enhanced. In the situation for the longer flexible body placed in upstream of the shorter one, the coupled flapping amplitude and average drag coefficients increase and decrease periodically with increasing the arranging space, and peak values appear as a result of the mediate of the tail wakes.展开更多
The interaction of a shock wave with a spherical helium bubble is investigated numerically by using the high- resolution piecewise parabolic method （PPM）, in which the viscous and turbulence effects are both conside...The interaction of a shock wave with a spherical helium bubble is investigated numerically by using the high- resolution piecewise parabolic method （PPM）, in which the viscous and turbulence effects are both considered. The bubble is of the same size and is accelerated by a planar shock of different Mach numbers （Ma）. The re- suits of low Ma cases agree quantitatively with those of experiments [G. Layes, O. Le M4tayer. Phys. Fluids 19 （2007） 042105]. With the increase of Ma, the final geometry of the bubble becomes quite different, the com- pression ratio is highly raised, and the time-dependent mean bubble velocity is also influenced. The compression ratios measured can be well normalized when Ma is low, while less agreement has been achieved for high Ma cases. In addition, the mixedness between two fluids is enhanced greatly as Ma increases. Some existed scaling laws of these quantities for the shock wave strength cannot be directly applied to high Ma cases.展开更多
Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to th...Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to the insufficient information about thecharacteristics of varieties.So,it is impor-tant to find ways of determining the potential展开更多
In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the p...In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the physical quantity in the wave equation is treated as a substitution variable.Based on the temporal discretization with the Krylov deferred correction(KDC)technique,the original wave problem is then converted into the modified Helmholtz equation.The transformed boundary value problem(BVP)in space is efficiently simulated by using the meshless generalized finite difference method(GFDM)with Taylor series after truncating the second and fourth order approximations.The developed scheme is finally verified by four numerical experiments including cases with complicated domains or the temporally piecewise defined source function.Numerical results match with the analytical solutions and results by the COMSOL software,which demonstrates that the developed KDC-GFDM can allow large time-step sizes for wave propagation problems in longtime intervals.展开更多
Building energy modeling,also known as building energy simulation,has developed rapidly in recent years and plays a crucial role in building life-cycle analysis.It can be employed in the design phase to predict the en...Building energy modeling,also known as building energy simulation,has developed rapidly in recent years and plays a crucial role in building life-cycle analysis.It can be employed in the design phase to predict the energy consumption of different design schemes and evaluate various control and retrofitting measures at the operation stage.In such simulations,it is commonly understood and accepted that the simulated relative differences are more reliable than the predictions of absolute energy results.However,whether this common understanding is true is yet to be thoroughly investigated.In this study,we investigate the simulated relative differences and the extent to which they are affected by the degree of model input deviation.Simulation and Monte Carlo approaches are adopted for the analysis.The results indicate that the simulated relative differences are not as reliable as expected,and the outputs strongly depend on the degree of the model input deviation.When the degree of deviation is less than 15%or the model inputs are within reasonable ranges,the simulated relative differences match the baseline obtained using Monte Carlo simulations.Moreover,the model’s error indicators meet the requirements of the ASHRAE Guideline 14–2014 when the degree of input deviation is below 15%.展开更多
In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.A...In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.And then,four finite element models of a same long-span suspension bridge with different cable element are set up to be analyzed.Both experimental and numerical simulation results show that,with the increase of the span and the decrease of sag-span ratio,the influence of the cable flexural rigidity is significant.The difference of nodes displacement reaches more than 10 cm in construction analysis,which will bring some trouble to the construction.And the difference of the maximum section edge normal stress may reach 15%,which may have an adverse impact onto the bridge.Therefore,considering the cable flexural rigidity is necessary on some analysis of suspension bridges.展开更多
Transmembrane water exchange(TWE)including transcytolemmal water exchange and transvascular water exchange is involved in many in vivo measurements and makes different contributions to the measuring results.In this st...Transmembrane water exchange(TWE)including transcytolemmal water exchange and transvascular water exchange is involved in many in vivo measurements and makes different contributions to the measuring results.In this study,we focus on the potential influence of TWE on the cell density parameter,intracellular water mole fraction pi,derived by dynamic contrast enhanced-magnetic resonance imaging(DCE-MRI)which has been reported as a technique to characterize perfusion and vascularization of tissues,but its accuracy in measuring cell density(or interstitial space)has been questioned.Sixteen patients with glioblastoma multiforme(GBM)were enrolled since GBM shows strong intratumor heterogeneity in both cell density and TWE.All the subjects were collected with DCE-MRI and apparent diffusion coefficient(ADC)map.The latter was considered as a valid surrogate of cell density.Extended Tofts(eTofts)model considering TWE as infinitely large variables and shutter-speed model(SSM)considering TWE as finite ones were used to fit DCE-MRI data.Monte Carlo(MC)and finite difference(FD)methods were used to simulate the influence of TWE on DCE-MRI-derived pi and ADC,respectively.The eTofts model shows a significant overestimation of pi in comparison with SSM in GBM(P<0.001),which is in accordance with MC simulations,and this overestimation shows dependence on the intra-to-extracellular water exchange rate constant(kio).Significant negative correlations between ADC and SSM-derived pi were found in both voxel-wise analyses(t-test P<0.001,average r=-0.74)and inter-subject comparisons(r=-0.63,P=0.009).But no consistent voxel-wise correlations(P>0.05)and a weaker inter-subject negative correlation(r=-0.56,P=0.02)were found between ADC and eTofts-derived pi.Further experimental and FD results revealed that kio made a limited contribution to ADC values in the physiological kio range in GBM,supporting ADC as a valid biomarker of cell density.These results suggest that the DCE-MRI pharmacokinetic shutter-speed model could significantly improve its accuracy in cell density estimation because of the considering transmembrane water exchange.展开更多
By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the ...By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry–Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.展开更多
The unique structural features represented by micro-nanoneedle tip structure reflect wonderful physical and chemical properties.The tip effect includes the concentration of energy such as electrons,photons and magneti...The unique structural features represented by micro-nanoneedle tip structure reflect wonderful physical and chemical properties.The tip effect includes the concentration of energy such as electrons,photons and magnetism in the tip region,which has promising applications in the fields of energy conversion,water capture,environmental restoration and so on.In this review,a comprehensive and systematic summary of the latest advances in the application of the tip effect in different fields is provided.Utilizing advanced Finite Difference Time Domain simulation,we further propose our understanding of the fundamental mechanism of the tip effect induced by micro-nanostructure.However,we need to forge the present study to further reveal the essential law of the tip effect from the perspective of theoretical calculations.This review would provide a solid foundation for further development and application of the tip effect.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51479007,51309017,and 11102027the Natural Science Foundation of Hubei Province under Grant No 2015CFA026the Fundamental Research Fund for State Public-Benefic Scientific Institutes of CRSRI under Grant No CKSF2015026/SL
文摘The coupled motion of two flexible bodies with different lengths immersed in moving fluid is studied numerically. The flapping frequency, flapping amplitude and average drag coefficient of each body are calculated and the influences of the arranging manner and separation distance are analyzed. In our simulation, when placed in the flow individually, the flexible body with a longer length will flap in period and the shorter one will maintain still straightly in the flow direction. The numerical results show that, two different flexible structures near placed in moving flow would strongly interact. When they are placed side by side, the existence of the stable shorter flexible body will restrain the flapping of the longer one while the existence of the longer flexible body may also induce the shorter one to flap synchronously. When placed in tandem with the shorter flexible body in upstream, the flapping of the longer one in downstream will be obviously enhanced. In the situation for the longer flexible body placed in upstream of the shorter one, the coupled flapping amplitude and average drag coefficients increase and decrease periodically with increasing the arranging space, and peak values appear as a result of the mediate of the tail wakes.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11232011 and 11402262the 111 Project under Grant No B07033the China Postdoctoral Science Foundation Funded Project under Grant No 2014M561833
文摘The interaction of a shock wave with a spherical helium bubble is investigated numerically by using the high- resolution piecewise parabolic method （PPM）, in which the viscous and turbulence effects are both considered. The bubble is of the same size and is accelerated by a planar shock of different Mach numbers （Ma）. The re- suits of low Ma cases agree quantitatively with those of experiments [G. Layes, O. Le M4tayer. Phys. Fluids 19 （2007） 042105]. With the increase of Ma, the final geometry of the bubble becomes quite different, the com- pression ratio is highly raised, and the time-dependent mean bubble velocity is also influenced. The compression ratios measured can be well normalized when Ma is low, while less agreement has been achieved for high Ma cases. In addition, the mixedness between two fluids is enhanced greatly as Ma increases. Some existed scaling laws of these quantities for the shock wave strength cannot be directly applied to high Ma cases.
文摘Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to the insufficient information about thecharacteristics of varieties.So,it is impor-tant to find ways of determining the potential
基金supported by the National Natural Science Foundation of China(Grant No.11802165)the Natural Science Foundation of Shandong Province of China(Grant No.ZR2017BA003)the China Postdoctoral Science Foundation(Grant No.2019M650158).
文摘In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the physical quantity in the wave equation is treated as a substitution variable.Based on the temporal discretization with the Krylov deferred correction(KDC)technique,the original wave problem is then converted into the modified Helmholtz equation.The transformed boundary value problem(BVP)in space is efficiently simulated by using the meshless generalized finite difference method(GFDM)with Taylor series after truncating the second and fourth order approximations.The developed scheme is finally verified by four numerical experiments including cases with complicated domains or the temporally piecewise defined source function.Numerical results match with the analytical solutions and results by the COMSOL software,which demonstrates that the developed KDC-GFDM can allow large time-step sizes for wave propagation problems in longtime intervals.
基金supported by the“Urban Carbon Neutral”Science and Technology Innovation Fund Project from Beijing University of Technology and Beijing Postdoctoral Research Foundation.
文摘Building energy modeling,also known as building energy simulation,has developed rapidly in recent years and plays a crucial role in building life-cycle analysis.It can be employed in the design phase to predict the energy consumption of different design schemes and evaluate various control and retrofitting measures at the operation stage.In such simulations,it is commonly understood and accepted that the simulated relative differences are more reliable than the predictions of absolute energy results.However,whether this common understanding is true is yet to be thoroughly investigated.In this study,we investigate the simulated relative differences and the extent to which they are affected by the degree of model input deviation.Simulation and Monte Carlo approaches are adopted for the analysis.The results indicate that the simulated relative differences are not as reliable as expected,and the outputs strongly depend on the degree of the model input deviation.When the degree of deviation is less than 15%or the model inputs are within reasonable ranges,the simulated relative differences match the baseline obtained using Monte Carlo simulations.Moreover,the model’s error indicators meet the requirements of the ASHRAE Guideline 14–2014 when the degree of input deviation is below 15%.
基金Sponsored by Major Research Plan of the National Natural Science Foundation of China (Grant No.90715021)
文摘In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.And then,four finite element models of a same long-span suspension bridge with different cable element are set up to be analyzed.Both experimental and numerical simulation results show that,with the increase of the span and the decrease of sag-span ratio,the influence of the cable flexural rigidity is significant.The difference of nodes displacement reaches more than 10 cm in construction analysis,which will bring some trouble to the construction.And the difference of the maximum section edge normal stress may reach 15%,which may have an adverse impact onto the bridge.Therefore,considering the cable flexural rigidity is necessary on some analysis of suspension bridges.
基金the National Natural Science Foundation of China(NSFC)(Grant No.81873894,Grant No.21922410)Natural Science Foundation of Zhejiang Province,China(Grant No.LR20H180001,Grant No.LR19B050001)Taishan Scholars Program(No.tsqn20161070).
文摘Transmembrane water exchange(TWE)including transcytolemmal water exchange and transvascular water exchange is involved in many in vivo measurements and makes different contributions to the measuring results.In this study,we focus on the potential influence of TWE on the cell density parameter,intracellular water mole fraction pi,derived by dynamic contrast enhanced-magnetic resonance imaging(DCE-MRI)which has been reported as a technique to characterize perfusion and vascularization of tissues,but its accuracy in measuring cell density(or interstitial space)has been questioned.Sixteen patients with glioblastoma multiforme(GBM)were enrolled since GBM shows strong intratumor heterogeneity in both cell density and TWE.All the subjects were collected with DCE-MRI and apparent diffusion coefficient(ADC)map.The latter was considered as a valid surrogate of cell density.Extended Tofts(eTofts)model considering TWE as infinitely large variables and shutter-speed model(SSM)considering TWE as finite ones were used to fit DCE-MRI data.Monte Carlo(MC)and finite difference(FD)methods were used to simulate the influence of TWE on DCE-MRI-derived pi and ADC,respectively.The eTofts model shows a significant overestimation of pi in comparison with SSM in GBM(P<0.001),which is in accordance with MC simulations,and this overestimation shows dependence on the intra-to-extracellular water exchange rate constant(kio).Significant negative correlations between ADC and SSM-derived pi were found in both voxel-wise analyses(t-test P<0.001,average r=-0.74)and inter-subject comparisons(r=-0.63,P=0.009).But no consistent voxel-wise correlations(P>0.05)and a weaker inter-subject negative correlation(r=-0.56,P=0.02)were found between ADC and eTofts-derived pi.Further experimental and FD results revealed that kio made a limited contribution to ADC values in the physiological kio range in GBM,supporting ADC as a valid biomarker of cell density.These results suggest that the DCE-MRI pharmacokinetic shutter-speed model could significantly improve its accuracy in cell density estimation because of the considering transmembrane water exchange.
基金Project supported by the National Key Basic Research Program of China (Grant No. 2013CB328702)
文摘By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry–Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.
基金financially supported by the Natural Science Foundation of China(No.51902101)Natural Science Foundation of Jiangsu Province(No.BK20201381)+1 种基金Science Foundation of Nanjing University of Posts and Telecommunications(No.NY219144)the National College Student Innovation and Entrepreneurship Training Program(No.202210293017Z).
文摘The unique structural features represented by micro-nanoneedle tip structure reflect wonderful physical and chemical properties.The tip effect includes the concentration of energy such as electrons,photons and magnetism in the tip region,which has promising applications in the fields of energy conversion,water capture,environmental restoration and so on.In this review,a comprehensive and systematic summary of the latest advances in the application of the tip effect in different fields is provided.Utilizing advanced Finite Difference Time Domain simulation,we further propose our understanding of the fundamental mechanism of the tip effect induced by micro-nanostructure.However,we need to forge the present study to further reveal the essential law of the tip effect from the perspective of theoretical calculations.This review would provide a solid foundation for further development and application of the tip effect.
