A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered...A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered story isolated system model is established using SAP2000. The dynamic nonlinear dynamic alternate method is used to analyze the structure against progressive collapse. Results show that the structure has good resistance to progressive collapse, and there is no progressive collapse under each working condition. The progressive collapse does not occur for the case of removing only one vertical structural member of the new staggered of isolated system. The side column has big influence on this isolated structures’ progressive collapse;the removal of vertical structural member of the isolation layer has less impact on the structure than the removal of the bottom vertical structural member. After the removing of the member, the internal force of the structure will be redistributed, and the axial force of the adjacent columns will change obviously, showing a trend of “near large and far small”.展开更多
The local arc-length method is employed to control the incremental loading procedure for phase-field brittle fracture modeling.An improved staggered algorithm with energy and damage iterative tolerance convergence cri...The local arc-length method is employed to control the incremental loading procedure for phase-field brittle fracture modeling.An improved staggered algorithm with energy and damage iterative tolerance convergence criteria is developed based on the residuals of displacement and phase-field.The improved staggered solution scheme is implemented in the commercial software ABAQUS with user-defined element subroutines.The layered system of finite elements is utilized to solve the coupled elastic displacement and phase-field fracture problem.A one-element benchmark test compared with the analytical solution was conducted to validate the feasibility and accuracy of the developed method.Our study shows that the result calculated with the developed method does not depend on the selected size of loading increments.The results of several numerical experiments show that the improved staggered algorithm is efficient for solving the more complex brittle fracture problems.展开更多
The photo-induced buckling of axially periodic glassy nematic films with alternating stripped director domains is explored by the F¨oppl-von K′arm′an plate theory along with a modified kinetics approach.The eff...The photo-induced buckling of axially periodic glassy nematic films with alternating stripped director domains is explored by the F¨oppl-von K′arm′an plate theory along with a modified kinetics approach.The effects of domain widths on the critical light intensity as well as the buckling morphology are examined numerically.It is found that in most cases the buckled film forms regularly aligned dimples and protrusions,but shows large scale bending perpendicular to the periodic axis if the widths of the stripes are nearly the same.In addition,change in light intensity is shown to alter the wavenumber of the buckling pattern.These results are expected helpful to the design of shape-shifting structures with glassy nematic films.展开更多
The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of ...The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of many cylindrical structures.Many active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated cylinder.Due to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV suppression.Some efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two decades.The control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control devices.The FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and summarized.The FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence factors.Further research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.展开更多
We investigate the chiral edge states-induced Josephson current–phase relation in a graphene-based Josephson junction modulated by the off-resonant circularly polarized light and the staggered sublattice potential.By...We investigate the chiral edge states-induced Josephson current–phase relation in a graphene-based Josephson junction modulated by the off-resonant circularly polarized light and the staggered sublattice potential.By solving the Bogoliubov–de Gennes equation,a φ_(0) Josephson junction is induced in the coaction of the off-resonant circularly polarized light and the staggered sublattice potential,which arises from the fact that the center of-mass wave vector of Cooper pair becomes finite and the opposite center of-mass wave vector to compensate is lacking in the nonsuperconducting region.Interestingly,when the direction of polarization of light is changed,-φ_(0) to φ_(0) transition generates,which generalizes the concept of traditional 0–πtransition.Our findings provide a purely optical way to manipulate a phase-controllable Josephson device and guidelines for future experiments to confirm the presence of graphene-based φ_(0)Josephson junction.展开更多
There are many problems with the conventional processes of magnesium alloy bending products,such as long processes and difficulty in controlling the product shape.This paper provides a staggered extrusion(SE)process t...There are many problems with the conventional processes of magnesium alloy bending products,such as long processes and difficulty in controlling the product shape.This paper provides a staggered extrusion(SE)process to solve the above manufacturing bottlenecks.The effects of different extrusion ratios(λ)on the AZ31 magnesium alloy bending products prepared by the SE process was investigated in this paper.The results show that the bending radii of the AZ31 Mg bending products increase with the increase ofλat the same staggered distance(h=16 mm).When A is in creased from 11.11 to 44.44,the average bending radius of bending products is decreased from 14.7 mm to 9 mm,and the average grain size is decreased by 59.43%.After the SE process,the extruded fiber texture of the AZ31 Mg bending products is obvious,and the deformed texture is a mixed texture of{0001}(10-10)deformation texture and{10-11}(11-20)recrystallization texture.The results of XRD and EBSD showed that pyramidal slip is an important mode of crystal slip systems in AZ31 magnesium alloys during the SE process.It provided a scientific basis for forming AZ31 Mg alloy bending products with excellent microstructure by the SE process.展开更多
In modelling elastic wave propagation in a porous medium, when the ratio between the fluid viscosity and the medium permeability is comparatively large, the stiffness problem of Blot's poroelastic equations will be e...In modelling elastic wave propagation in a porous medium, when the ratio between the fluid viscosity and the medium permeability is comparatively large, the stiffness problem of Blot's poroelastic equations will be encountered. In the paper, a partition method is developed to solve the stiffness problem with a staggered high-order finite-difference. The method splits the Biot equations into two systems. One is stiff, and solved analytically, the other is nonstiff, and solved numerically by using a high-order staggered-grid finite-difference scheme. The time step is determined by the staggered finite-difference algorithm in solving the nonstiff equations, thus a coarse time step may be employed. Therefore, the computation efficiency and computational stability are improved greatly. Also a perfect by matched layer technology is used in the split method as absorbing boundary conditions. The numerical results are compared with the analytical results and those obtained from the conventional staggered-grid finite-difference method in a homogeneous model, respectively. They are in good agreement with each other. Finally, a slightly more complex model is investigated and compared with related equivalent model to illustrate the good performance of the staggered-grid finite-difference scheme in the partition method.展开更多
Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion...Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.展开更多
Reverse time migration and full waveform inversion involve the crosscorrelation of two wavefields,propagated in the forward-and reverse-time directions,respectively.As a result,the forward-propagated wavefield needs t...Reverse time migration and full waveform inversion involve the crosscorrelation of two wavefields,propagated in the forward-and reverse-time directions,respectively.As a result,the forward-propagated wavefield needs to be stored,and then accessed to compute the correlation with the backward-propagated wavefield.Boundary-value methods reconstruct the source wavefield using saved boundary wavefields and can significantly reduce the storage requirements.However,the existing boundary-value methods are based on the explicit finite-difference(FD)approximations of the spatial derivatives.Implicit FD methods exhibit greater accuracy and thus allow for a smaller operator length.We develop two(an accuracy-preserving and a memory-efficient)wavefield reconstruction schemes based on an implicit staggered-grid FD(SFD)operator.The former uses boundary wavefields at M layers of grid points and the spatial derivatives of wavefields at one layer of grid points to reconstruct the source wavefield for a(2M+2)th-order implicit SFD operator.The latter applies boundary wavefields at N layers of grid points,a linear combination of wavefields at M–N layers of grid points,and the spatial derivatives of wavefields at one layer of grid points to reconstruct the source wavefield(0≤N<M).The required memory of accuracy-preserving and memory-efficient schemes is(M+1)/M and(N+2)/M times,respectively,that of the explicit reconstruction scheme.Numerical results reveal that the accuracy-preserving scheme can achieve accurate reconstruction at the cost of storage.The memory-efficient scheme with N=2 can obtain plausible reconstructed wavefields and images,and the storage amount is 4/(M+1)of the accuracy-preserving scheme.展开更多
The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then sin...The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then singularity arises at the center of the Earth where r=0 since the 1/r term appears in the wave equations. In this paper, we extended the global seismic wavefield simulation algorithm for regular grid mesh to staggered grid configuration and developed a scheme to solve the numerical problems associated with the above singularity for a 2-D global Earth model defined on staggered grid using pseudospectral method. This scheme uses a coordinate transformation at the center of the model, in which the field variables at the center are calculated in Cartesian coordinates from the values on the grids around the center. It allows wave propagation through the center and hence the wavefield at the center can be stably calculated. Validity and accuracy of the scheme was tested by compared with the discrete wavenumber method. This scheme could also be suitable for other numerical methods or models parameterized in cylindrical or spherical coordinates when singularity arises at the center of the model.展开更多
Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam...Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications.展开更多
Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of...Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of the side rock bolt and anchor cable parameters on the mechanical properties of the anchorage body and the support stress distribution of the lateral coal body were revealed using the FLAC3D software.The optimal support parameters of the side rock bolts and anchor cables were subsequently determined,and the support effect of gob-side entry in a mining scenario was verified.The results show that the support of the side rock bolts and anchor cables improves the mechanical properties and stress state of the anchorage body,producing a good protective effect on the coal body of the air-intake entry roof and side wall.This is beneficial to the stability of the side wall and the realization of the suspension effect for roof rock bolts and anchor cables,which in turn makes the surrounding rock maintenance of the gob-side entry to a thick coal seam more favorable.展开更多
In order to gain a deeper understanding of the quantum criticality in the explicitly staggered dimerized Heisenberg models, we study a generalized staggered dimer model named the J0 J1 J2 model, which corresponds to t...In order to gain a deeper understanding of the quantum criticality in the explicitly staggered dimerized Heisenberg models, we study a generalized staggered dimer model named the J0 J1 J2 model, which corresponds to the staggered j-j′ model on a square lattice and a honeycomb lattice when J1/J0 equals 1 and O, respectively. Using the quantum Monte Carlo method, we investigate all the quantum critical points of these models with J1/J0 changing from 0 to 1 as a function of coupling ratio a = J2/J0. We extract all the critical values of the coupling ratio ac for these models, and we also obtain the critical exponents v,β/ν, and η using different finite-size scaling ansatz,. All these exponents are not consistent with the three-dimensional Heisenberg universality class, indicating some unconventional quantum ciriteial points in these models.展开更多
Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and structures.Although a substantial number of studies have been devoted to assessing FIV response behavio...Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and structures.Although a substantial number of studies have been devoted to assessing FIV response behaviours,fatigue damage features of staggered flexible cylinders are not fully understood.Moreover,the wake-induced flutter constitutes an intricate hydrodynamic behaviour that frequently occurs when one cylinder is in the vicinity of another one.Unfortunately,existing studies on the fatigue damage caused by wake-induced flutter are incapable of achieving better results.This paper,therefore,estimates the FIV fatigue damage of two staggered flexible cylinders with an aspect ratio of 350 and a mass ratio of 1.90 based on normal S−N curves according to Det Norske Veritas(DNV)regulations.Twelve staggered cases(cross-flow spacing ratios of 2.0,3.0,4.0,and 6.0 and in-line spacing ratios of 4.0,6.0,and 8.0)are discussed for comparison,and fatigue damage caused by wake-induced flutter is thoroughly considered.Fatigue damage results indicate that the variation of the cross-flow(CF)spacing ratio has a greater influence than that of the in-line(IL)spacing ratio on the CF fatigue damage of the upstream cylinder.Lower IL fatigue damages of the upstream cylinder are observed when reduced velocity V_(r)≥15.03 due to the wake flow patterns with different IL spacing ratios.Moreover,wake interference,especially wake-induced flutter,predominates the fatigue damage characteristics of the downstream cylinder.When V_(r)=8.77−11.27,wake-induced flutter enhances the IL fatigue damage of the downstream cylinder and slightly affects that of the upstream body.Furthermore,wake-induced flutter causes considerable IL fatigue damage disparity between the two staggered cylinders by suppressing the IL fatigue damage of the upstream cylinder when V_(r)≥20.04.展开更多
Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical structures.It is omnidirectional and can effectively reduce FIV response amplitude.Studies on the passive FIV contro...Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical structures.It is omnidirectional and can effectively reduce FIV response amplitude.Studies on the passive FIV control for cylindrical structures are mainly concerned with a single isolated cylinder,while the influence of wake interference between multiple cylinders on FIV suppression devices is less considered up to now.In engineering applications,multiple flexible cylinders with large aspect ratios can be subjected to complex flow forces,and the effects of wake interference are obvious.The FIV suppression effect of helical strake of a common configuration(17.5D pitch and 0.25D height,where D is the cylinder diameter)in two staggered cylinders system is still unknown.This paper systematically studied the FIV response of multiple cylinders system fitted with the helical strakes by model tests.The relative spatial position of the two cylinders is fixed at S=3.0D and T=8.0D,which ensures the cylindrical structures in the flow interference region.The experimental results show that the helical strakes effectively reduce the FIV response on staggered upstream cylinder,and the suppression efficiency is barely affected by the smooth or straked downstream cylinder.The corresponding FIV suppression efficiency on the downstream cylinder is remarkably reduced by the influence of the upstream wake flow.The wake-induced vibration(WIV)phenomenon is not observed on the staggered downstream cylinder,which normally occurs on the downstream straked cylinder in a tandem arrangement.展开更多
Strong ground motion of an earthquake is simulated by using both staggered grid finite difference method (FDM) and stochastic method, respectively. The acceleration time histories obtained from the both ways and their...Strong ground motion of an earthquake is simulated by using both staggered grid finite difference method (FDM) and stochastic method, respectively. The acceleration time histories obtained from the both ways and their response spectra are compared. The result demonstrates that the former is adequate to simulate the low-frequency seismic wave; the latter is adequate to simulate the high-frequency seismic wave. Moreover, the result obtained from FDM can better reflect basin effects.展开更多
Staggered herringbone micromixer has shown good efficiency of mixing and performance of synthesizing nanoparticles.To bring a detailed understanding of the mixing dynamics and syn-thesis performance of this kind of mi...Staggered herringbone micromixer has shown good efficiency of mixing and performance of synthesizing nanoparticles.To bring a detailed understanding of the mixing dynamics and syn-thesis performance of this kind of micromixer,this paper carries out a high-fidelity numerical simu-lation and a parametrial experimental study on a well-established design.A passive tracer is induced in the numerical simulation to analyze mixing dynamics induced by the staggered herring-bone structures.Three effects are identified to reveal the underlying mechanisms,including folding,stretching,and splitting.To the authors’knowledge,the splitting effect is identified for the first time by the isosurface of the passive tracer,to show the high efficiency of the staggered herring-bone design.The micromixer is then used to synthesize lipid nanoparticles by mixing a mixture of lipid and poly(lactic-co-glycolic acid)(PLGA)solutions with deionized water.Under a wide mass ratio of lipid and PLGA solutions,nanoparticles with good monodispersity are synthesized to reflect the good compatibility of the micromixer and the mixture.In addition,an optimized mass ratio is identified from the parametrical experiment.展开更多
A finite volume method based unstructured grid is presented to solve the two dimensional viscous and incompressible flow.The method is based on the pressure-correction concept and solved by using a semi-staggered grid...A finite volume method based unstructured grid is presented to solve the two dimensional viscous and incompressible flow.The method is based on the pressure-correction concept and solved by using a semi-staggered grid technique.The computational procedure can handle cells of arbitrary shapes,although solutions presented in this paper were only involved with triangular and quadrilateral cells.The pressure or pressure-correction value was stored on the vertex of cells.The mass conservation equation was discretized on the dual cells surrounding the vertex of primary cells,while the velocity components and other scale variables were saved on the central of primary cells.Since the semi-staggered arrangement can’t guarantee a strong coupling relationship between pressure and velocity,thus a weak coupling relationship leads to the oscillations for pressure and velocity.In order to eliminate such an oscillation,a special interpolation scheme was used to construct the pressure-correction equation.Computational results of several viscous flow problems show good agreement with the analytical or numerical results in previous literature.This semi-staggered grid method can be applied to arbitrary shape elements,while it has the most efficiency for triangular cells.展开更多
Equipped with a two-dimensional topological structure,a group of masses,springs and dampers can be demonstrated to model the internal dynamics of a thin-film transistor(TFT).In this paper,the two-dimensional Mass-Spri...Equipped with a two-dimensional topological structure,a group of masses,springs and dampers can be demonstrated to model the internal dynamics of a thin-film transistor(TFT).In this paper,the two-dimensional Mass-Spring-Damper(MSD)representation of an inverted staggered TFT is proposed to explore the TFT’s internal stress/strain distributions,and the stress-induced effects on TFT’s electrical characteristics.The 2DMSD model is composed of a finite but massive number of interconnected cellular units.The parameters,such as mass,stiffness,and damping ratios,of each cellular unit are approximated from constitutive equations of the compositematerials,while the electrical properties of the inverted staggered TFT are characterized by utilizing an electro-mechanical coupling relation derived from the quantum mechanics.TFTs are often used in biomedical sensors/transducers attached to human skins,and,for the purpose of simulation and validation,the boundary conditions on the interface between the TFT and the human skin were modeled as a spatially distributed sinusoidal excitation with a frequency of 50 Hz,assuming the TFT thickness is more than tens of microns.The fidelity of the 2D MSD structure in the modeling of an inverted staggered TFT is verified by comparing its simulated total displacement fieldwith that of a finite element analysis(FEA)model.The advantages of the MSD model include a dramatic reduction in memory use by up to 60%and faster computation times that are up to 80%lower.More importantly,the MSD model is better suited than FEA to many problems in accurate tissue modeling for medical applications,for which FEA is becoming a bottleneck.This work develops a novel modeling approach,which can be extended to other types of flexible thin film transistors.展开更多
文摘A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered story isolated system model is established using SAP2000. The dynamic nonlinear dynamic alternate method is used to analyze the structure against progressive collapse. Results show that the structure has good resistance to progressive collapse, and there is no progressive collapse under each working condition. The progressive collapse does not occur for the case of removing only one vertical structural member of the new staggered of isolated system. The side column has big influence on this isolated structures’ progressive collapse;the removal of vertical structural member of the isolation layer has less impact on the structure than the removal of the bottom vertical structural member. After the removing of the member, the internal force of the structure will be redistributed, and the axial force of the adjacent columns will change obviously, showing a trend of “near large and far small”.
基金supports by the National Key R&D Program of China(No.2018YFD1100401)the National Natural Science Foundation of China(No.51578142)+1 种基金the Fundamental Research Funds for the Central Universities(No.LEM21A03)Jiangsu Key Laboratory of Engineering Mechanics(Southeast University)are gratefully acknowledged.
文摘The local arc-length method is employed to control the incremental loading procedure for phase-field brittle fracture modeling.An improved staggered algorithm with energy and damage iterative tolerance convergence criteria is developed based on the residuals of displacement and phase-field.The improved staggered solution scheme is implemented in the commercial software ABAQUS with user-defined element subroutines.The layered system of finite elements is utilized to solve the coupled elastic displacement and phase-field fracture problem.A one-element benchmark test compared with the analytical solution was conducted to validate the feasibility and accuracy of the developed method.Our study shows that the result calculated with the developed method does not depend on the selected size of loading increments.The results of several numerical experiments show that the improved staggered algorithm is efficient for solving the more complex brittle fracture problems.
基金Project supported by the National Natural Science Foundation of China(No.12332011)。
文摘The photo-induced buckling of axially periodic glassy nematic films with alternating stripped director domains is explored by the F¨oppl-von K′arm′an plate theory along with a modified kinetics approach.The effects of domain widths on the critical light intensity as well as the buckling morphology are examined numerically.It is found that in most cases the buckled film forms regularly aligned dimples and protrusions,but shows large scale bending perpendicular to the periodic axis if the widths of the stripes are nearly the same.In addition,change in light intensity is shown to alter the wavenumber of the buckling pattern.These results are expected helpful to the design of shape-shifting structures with glassy nematic films.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U2106223,51979193,52301352)。
文摘The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of many cylindrical structures.Many active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated cylinder.Due to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV suppression.Some efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two decades.The control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control devices.The FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and summarized.The FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence factors.Further research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12104232,11805103,and 11804167)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20190137 and BK20180739)+2 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.020414380195 and B230201042)the Jit-b Project(Grant No.201831)the Natural Science Fund of Nanjing University of Posts and Telecommunications(Grant No.NY222163)。
文摘We investigate the chiral edge states-induced Josephson current–phase relation in a graphene-based Josephson junction modulated by the off-resonant circularly polarized light and the staggered sublattice potential.By solving the Bogoliubov–de Gennes equation,a φ_(0) Josephson junction is induced in the coaction of the off-resonant circularly polarized light and the staggered sublattice potential,which arises from the fact that the center of-mass wave vector of Cooper pair becomes finite and the opposite center of-mass wave vector to compensate is lacking in the nonsuperconducting region.Interestingly,when the direction of polarization of light is changed,-φ_(0) to φ_(0) transition generates,which generalizes the concept of traditional 0–πtransition.Our findings provide a purely optical way to manipulate a phase-controllable Josephson device and guidelines for future experiments to confirm the presence of graphene-based φ_(0)Josephson junction.
基金the National Natural Science Foundation of China(51675143)the Fundamental Research Foundation for Universities of Heilongjiang Province(LGYC2018JQ011)the Natural Science Foundation of Heilongjiang Province(LH2019E056).
文摘There are many problems with the conventional processes of magnesium alloy bending products,such as long processes and difficulty in controlling the product shape.This paper provides a staggered extrusion(SE)process to solve the above manufacturing bottlenecks.The effects of different extrusion ratios(λ)on the AZ31 magnesium alloy bending products prepared by the SE process was investigated in this paper.The results show that the bending radii of the AZ31 Mg bending products increase with the increase ofλat the same staggered distance(h=16 mm).When A is in creased from 11.11 to 44.44,the average bending radius of bending products is decreased from 14.7 mm to 9 mm,and the average grain size is decreased by 59.43%.After the SE process,the extruded fiber texture of the AZ31 Mg bending products is obvious,and the deformed texture is a mixed texture of{0001}(10-10)deformation texture and{10-11}(11-20)recrystallization texture.The results of XRD and EBSD showed that pyramidal slip is an important mode of crystal slip systems in AZ31 magnesium alloys during the SE process.It provided a scientific basis for forming AZ31 Mg alloy bending products with excellent microstructure by the SE process.
基金Project supported by the "100 Talents Project" of the Chinese Academy of Sciences and the Major Program of the National Natural Science Foundation of China (Grant No 10534040).
文摘In modelling elastic wave propagation in a porous medium, when the ratio between the fluid viscosity and the medium permeability is comparatively large, the stiffness problem of Blot's poroelastic equations will be encountered. In the paper, a partition method is developed to solve the stiffness problem with a staggered high-order finite-difference. The method splits the Biot equations into two systems. One is stiff, and solved analytically, the other is nonstiff, and solved numerically by using a high-order staggered-grid finite-difference scheme. The time step is determined by the staggered finite-difference algorithm in solving the nonstiff equations, thus a coarse time step may be employed. Therefore, the computation efficiency and computational stability are improved greatly. Also a perfect by matched layer technology is used in the split method as absorbing boundary conditions. The numerical results are compared with the analytical results and those obtained from the conventional staggered-grid finite-difference method in a homogeneous model, respectively. They are in good agreement with each other. Finally, a slightly more complex model is investigated and compared with related equivalent model to illustrate the good performance of the staggered-grid finite-difference scheme in the partition method.
基金supported by National Natural Science Foundation of China(No.61671431)
文摘Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.
基金partially supported by National Key R&D Program of China(2021YFA0716902)the National Natural Science Foundation of China(42174156)the Fundamental Research Funds for the Central Universities,CHD(300102261107)。
文摘Reverse time migration and full waveform inversion involve the crosscorrelation of two wavefields,propagated in the forward-and reverse-time directions,respectively.As a result,the forward-propagated wavefield needs to be stored,and then accessed to compute the correlation with the backward-propagated wavefield.Boundary-value methods reconstruct the source wavefield using saved boundary wavefields and can significantly reduce the storage requirements.However,the existing boundary-value methods are based on the explicit finite-difference(FD)approximations of the spatial derivatives.Implicit FD methods exhibit greater accuracy and thus allow for a smaller operator length.We develop two(an accuracy-preserving and a memory-efficient)wavefield reconstruction schemes based on an implicit staggered-grid FD(SFD)operator.The former uses boundary wavefields at M layers of grid points and the spatial derivatives of wavefields at one layer of grid points to reconstruct the source wavefield for a(2M+2)th-order implicit SFD operator.The latter applies boundary wavefields at N layers of grid points,a linear combination of wavefields at M–N layers of grid points,and the spatial derivatives of wavefields at one layer of grid points to reconstruct the source wavefield(0≤N<M).The required memory of accuracy-preserving and memory-efficient schemes is(M+1)/M and(N+2)/M times,respectively,that of the explicit reconstruction scheme.Numerical results reveal that the accuracy-preserving scheme can achieve accurate reconstruction at the cost of storage.The memory-efficient scheme with N=2 can obtain plausible reconstructed wavefields and images,and the storage amount is 4/(M+1)of the accuracy-preserving scheme.
基金supported by the National Natural Science Foundation of China under grant Nos.40474012,40874020 and 40821062
文摘The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then singularity arises at the center of the Earth where r=0 since the 1/r term appears in the wave equations. In this paper, we extended the global seismic wavefield simulation algorithm for regular grid mesh to staggered grid configuration and developed a scheme to solve the numerical problems associated with the above singularity for a 2-D global Earth model defined on staggered grid using pseudospectral method. This scheme uses a coordinate transformation at the center of the model, in which the field variables at the center are calculated in Cartesian coordinates from the values on the grids around the center. It allows wave propagation through the center and hence the wavefield at the center can be stably calculated. Validity and accuracy of the scheme was tested by compared with the discrete wavenumber method. This scheme could also be suitable for other numerical methods or models parameterized in cylindrical or spherical coordinates when singularity arises at the center of the model.
基金Project supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 61125103)the National Natural Science Foundation of China (Grant Nos. 60971038 and 60971031)the Fundamental Research Funds for the Central Universities (Grant No. ZYGX2009Z003)
文摘Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications.
基金National Natural Science Foundation of Surface Project of China(Grant Nos.5177428952074291)+2 种基金The National Natural Science Foundation of the Youth Science Foundation of China(Grant No.51404270)The Fundamental Research Funds for the Central Universities(Grant No.2011QZ06)The Open Fund of State Key Laboratory of Coal Resources in Western China(Grant No.SKLCRKF1903).
文摘Using the spatial structure of the external staggered split-level panel layout,a combined support technology for adjacent roadways was developed and analyzed for a rock bolt and anchor cable mechanism.The influence of the side rock bolt and anchor cable parameters on the mechanical properties of the anchorage body and the support stress distribution of the lateral coal body were revealed using the FLAC3D software.The optimal support parameters of the side rock bolts and anchor cables were subsequently determined,and the support effect of gob-side entry in a mining scenario was verified.The results show that the support of the side rock bolts and anchor cables improves the mechanical properties and stress state of the anchorage body,producing a good protective effect on the coal body of the air-intake entry roof and side wall.This is beneficial to the stability of the side wall and the realization of the suspension effect for roof rock bolts and anchor cables,which in turn makes the surrounding rock maintenance of the gob-side entry to a thick coal seam more favorable.
基金Project supported by the National Natural Science Foundation of China (Grants Nos. 11174359 and 10874232)the National Basic Research Program of China (Grant No. 2012CB932302)
文摘In order to gain a deeper understanding of the quantum criticality in the explicitly staggered dimerized Heisenberg models, we study a generalized staggered dimer model named the J0 J1 J2 model, which corresponds to the staggered j-j′ model on a square lattice and a honeycomb lattice when J1/J0 equals 1 and O, respectively. Using the quantum Monte Carlo method, we investigate all the quantum critical points of these models with J1/J0 changing from 0 to 1 as a function of coupling ratio a = J2/J0. We extract all the critical values of the coupling ratio ac for these models, and we also obtain the critical exponents v,β/ν, and η using different finite-size scaling ansatz,. All these exponents are not consistent with the three-dimensional Heisenberg universality class, indicating some unconventional quantum ciriteial points in these models.
基金financially supported by the National Natural Science Foundation of China(Grant No.51979193)the Major Consulting Project of Academy-Local Cooperation of Chinese Academy of Engineering(Grant No.2021DFZD2).
文摘Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and structures.Although a substantial number of studies have been devoted to assessing FIV response behaviours,fatigue damage features of staggered flexible cylinders are not fully understood.Moreover,the wake-induced flutter constitutes an intricate hydrodynamic behaviour that frequently occurs when one cylinder is in the vicinity of another one.Unfortunately,existing studies on the fatigue damage caused by wake-induced flutter are incapable of achieving better results.This paper,therefore,estimates the FIV fatigue damage of two staggered flexible cylinders with an aspect ratio of 350 and a mass ratio of 1.90 based on normal S−N curves according to Det Norske Veritas(DNV)regulations.Twelve staggered cases(cross-flow spacing ratios of 2.0,3.0,4.0,and 6.0 and in-line spacing ratios of 4.0,6.0,and 8.0)are discussed for comparison,and fatigue damage caused by wake-induced flutter is thoroughly considered.Fatigue damage results indicate that the variation of the cross-flow(CF)spacing ratio has a greater influence than that of the in-line(IL)spacing ratio on the CF fatigue damage of the upstream cylinder.Lower IL fatigue damages of the upstream cylinder are observed when reduced velocity V_(r)≥15.03 due to the wake flow patterns with different IL spacing ratios.Moreover,wake interference,especially wake-induced flutter,predominates the fatigue damage characteristics of the downstream cylinder.When V_(r)=8.77−11.27,wake-induced flutter enhances the IL fatigue damage of the downstream cylinder and slightly affects that of the upstream body.Furthermore,wake-induced flutter causes considerable IL fatigue damage disparity between the two staggered cylinders by suppressing the IL fatigue damage of the upstream cylinder when V_(r)≥20.04.
基金the National Natural Science Foundation of China(Grant No.51979193)the Natural Science Foundation of Tianjin(Grant No.20JCYBJC00890).
文摘Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical structures.It is omnidirectional and can effectively reduce FIV response amplitude.Studies on the passive FIV control for cylindrical structures are mainly concerned with a single isolated cylinder,while the influence of wake interference between multiple cylinders on FIV suppression devices is less considered up to now.In engineering applications,multiple flexible cylinders with large aspect ratios can be subjected to complex flow forces,and the effects of wake interference are obvious.The FIV suppression effect of helical strake of a common configuration(17.5D pitch and 0.25D height,where D is the cylinder diameter)in two staggered cylinders system is still unknown.This paper systematically studied the FIV response of multiple cylinders system fitted with the helical strakes by model tests.The relative spatial position of the two cylinders is fixed at S=3.0D and T=8.0D,which ensures the cylindrical structures in the flow interference region.The experimental results show that the helical strakes effectively reduce the FIV response on staggered upstream cylinder,and the suppression efficiency is barely affected by the smooth or straked downstream cylinder.The corresponding FIV suppression efficiency on the downstream cylinder is remarkably reduced by the influence of the upstream wake flow.The wake-induced vibration(WIV)phenomenon is not observed on the staggered downstream cylinder,which normally occurs on the downstream straked cylinder in a tandem arrangement.
基金National Natural Science Foundation of China (5048003) and DAAD of Munich University, Germany.
文摘Strong ground motion of an earthquake is simulated by using both staggered grid finite difference method (FDM) and stochastic method, respectively. The acceleration time histories obtained from the both ways and their response spectra are compared. The result demonstrates that the former is adequate to simulate the low-frequency seismic wave; the latter is adequate to simulate the high-frequency seismic wave. Moreover, the result obtained from FDM can better reflect basin effects.
基金supported by the National Natural Science Foundation of China(No.11772343)the Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Staggered herringbone micromixer has shown good efficiency of mixing and performance of synthesizing nanoparticles.To bring a detailed understanding of the mixing dynamics and syn-thesis performance of this kind of micromixer,this paper carries out a high-fidelity numerical simu-lation and a parametrial experimental study on a well-established design.A passive tracer is induced in the numerical simulation to analyze mixing dynamics induced by the staggered herring-bone structures.Three effects are identified to reveal the underlying mechanisms,including folding,stretching,and splitting.To the authors’knowledge,the splitting effect is identified for the first time by the isosurface of the passive tracer,to show the high efficiency of the staggered herring-bone design.The micromixer is then used to synthesize lipid nanoparticles by mixing a mixture of lipid and poly(lactic-co-glycolic acid)(PLGA)solutions with deionized water.Under a wide mass ratio of lipid and PLGA solutions,nanoparticles with good monodispersity are synthesized to reflect the good compatibility of the micromixer and the mixture.In addition,an optimized mass ratio is identified from the parametrical experiment.
基金supported by the Natural Science Foundation of China(No.51676208)the Fundamental Research Funds for the Central Universities(No.18CX07012A and No.19CX05002A)support from the Major Program of the Natural Science Foundation of Shandong Province(No.ZR2019ZD11).
文摘A finite volume method based unstructured grid is presented to solve the two dimensional viscous and incompressible flow.The method is based on the pressure-correction concept and solved by using a semi-staggered grid technique.The computational procedure can handle cells of arbitrary shapes,although solutions presented in this paper were only involved with triangular and quadrilateral cells.The pressure or pressure-correction value was stored on the vertex of cells.The mass conservation equation was discretized on the dual cells surrounding the vertex of primary cells,while the velocity components and other scale variables were saved on the central of primary cells.Since the semi-staggered arrangement can’t guarantee a strong coupling relationship between pressure and velocity,thus a weak coupling relationship leads to the oscillations for pressure and velocity.In order to eliminate such an oscillation,a special interpolation scheme was used to construct the pressure-correction equation.Computational results of several viscous flow problems show good agreement with the analytical or numerical results in previous literature.This semi-staggered grid method can be applied to arbitrary shape elements,while it has the most efficiency for triangular cells.
基金This work was supported in part by the National Science Foundation through grant CNS-1726865 and by the USDA under grant 2019-67021-28990.
文摘Equipped with a two-dimensional topological structure,a group of masses,springs and dampers can be demonstrated to model the internal dynamics of a thin-film transistor(TFT).In this paper,the two-dimensional Mass-Spring-Damper(MSD)representation of an inverted staggered TFT is proposed to explore the TFT’s internal stress/strain distributions,and the stress-induced effects on TFT’s electrical characteristics.The 2DMSD model is composed of a finite but massive number of interconnected cellular units.The parameters,such as mass,stiffness,and damping ratios,of each cellular unit are approximated from constitutive equations of the compositematerials,while the electrical properties of the inverted staggered TFT are characterized by utilizing an electro-mechanical coupling relation derived from the quantum mechanics.TFTs are often used in biomedical sensors/transducers attached to human skins,and,for the purpose of simulation and validation,the boundary conditions on the interface between the TFT and the human skin were modeled as a spatially distributed sinusoidal excitation with a frequency of 50 Hz,assuming the TFT thickness is more than tens of microns.The fidelity of the 2D MSD structure in the modeling of an inverted staggered TFT is verified by comparing its simulated total displacement fieldwith that of a finite element analysis(FEA)model.The advantages of the MSD model include a dramatic reduction in memory use by up to 60%and faster computation times that are up to 80%lower.More importantly,the MSD model is better suited than FEA to many problems in accurate tissue modeling for medical applications,for which FEA is becoming a bottleneck.This work develops a novel modeling approach,which can be extended to other types of flexible thin film transistors.