Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered ext...Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered extrusion(SE)process was used to form the curved profile of AZ31 magnesium alloy in this paper.The study investigates the mapping relationship between the curvature,microstructure,and mechanical properties of the formed profiles by using different eccentricities of the die.Scanning electron microscopy(SEM)and electron backscatter diffraction techniques are employed to examine the effects of different eccentricity values(e)on grain morphology,recrystallization mechanisms,texture,and Schmid factors of the products.The results demonstrate that the staggered extrusion method promotes the deep refinement of grain size in the extruded products,with an average grain size of only 15%of the original billet,reaching 12.28μm.The tensile strength and elongation of the curved profiles after extrusion under the eccentricity value of 10 mm,20 mm and 30 mm are significantly higher than those of the billet,with the tensile strength is increased to 250,270,235 MPa,and the engineering strain elongation increased to 10.5%,12.1%,15.9%.This indicates that staggered extrusion enables curvature control of the profiles while improving their strength.展开更多
With the widespread application of Staggered Counter-rotating Rotor(SCR)systems in eVTOL and UAV configurations,a comprehensive understanding of SCR performance under Outof-Ground Effect(OGE)and In-Ground Effect(IGE)c...With the widespread application of Staggered Counter-rotating Rotor(SCR)systems in eVTOL and UAV configurations,a comprehensive understanding of SCR performance under Outof-Ground Effect(OGE)and In-Ground Effect(IGE)conditions is crucial for aircraft design and landing safety.This study experimentally measured the changes in thrust and torque of the upper and lower rotors in an SCR system under varying axial and radial distances.It focuses on the interaction mechanisms between the upper and lower rotors and conducts specific IGE state experiments for certain SCR configurations.The findings reveal that changes in the lower rotor predominantly influence the overall performance of the SCR system,regardless of OGE or IGE conditions.Under OGE conditions,radial distance has a more significant impact than axial distance.Conversely,under IGE conditions,the axial distance plays a critical role in improving SCR system performance.These results provide a broad parameter range to assess SCR system performance variations,offering guidance for the design of new concept rotorcraft configurations and the development of aerodynamic prediction models under IGE conditions.展开更多
The lattice Boltzmann method(LBM)is employed to simulate flow around two staggered cylinders within a confined channel.The numerical model is validated against existing experimental data by comparing drag coefficients...The lattice Boltzmann method(LBM)is employed to simulate flow around two staggered cylinders within a confined channel.The numerical model is validated against existing experimental data by comparing drag coefficients and Strouhal numbers in the single-cylinder configuration.The study systematically investigates the influence of vertical(h)and horizontal(l)spacing between the cylinders,as well as the Reynolds number(Re=0.1–160),on the hydrodynamic forces,streamline patterns,and vortex dynamics.Results indicate that reducing the horizontal spacing l suppresses flow separation behind the upstream cylinder,while either excessively small or large vertical spacing h diminishes separation in the downstream cylinder.The onset of periodic vortex shedding is delayed due to inter-cylinder interactions,with the critical Reynolds number increasing to Rec=71–112,significantly higher than that of a single-cylinder case(Re_(c)≈69).During the vortex shedding regime,the downstream cylinder exhibits a greater lift force fluctuation compared to the upstream cylinder.At Re=160,the root-mean-square lift coefficient(C′_(L))ranges from approximately 0.17 to 0.56 for the downstream cylinder,and from 0.018 to 0.4 for the upstream one.The shedding frequency,characterized by the Strouhal number(St),increases with Reynolds number,reaching St=0.12–0.18 at Re=160.Variations in h and l significantly influence St,with a decrease in l or an increase in h lowering the shedding frequency—this effect is more pronounced in the horizontal direction.展开更多
Natural biomaterials with staggered structures exhibit remarkable mechanical properties owing to their unique microstructure.The microstructural arrangement can induce size-dependent and viscoelastic responses within ...Natural biomaterials with staggered structures exhibit remarkable mechanical properties owing to their unique microstructure.The microstructural arrangement can induce size-dependent and viscoelastic responses within the material.This study proposes a strain gradient viscoelastic shear-lag model to elucidate the intricate interplay between the strain gradient and viscoelastic effect in staggered shells.Our model clarifies the role of both effects,as experimentally observed,in governing the mechanical properties of these biomaterials.A detailed characterization of the size-dependent responses is conducted through the utilization of a microstructural characterization parameter alongside viscoelastic constitutive models.Then,the effective modulus of the staggered shell is defined and its formula is derived through the Laplace transform.Compared to classical models and even the strain gradient elastic model,the strain gradient viscoelastic model offers calculated moduli that are more consistent with experimental data.Moreover,the strengthening-softening effect of staggered structures is predicted using the strain gradient viscoelastic model and critical energy principle.This study contributes significantly to our understanding of the mechanical behavior of structural materials.Additionally,it provides insights for the design of advanced bionic materials with tailored properties.展开更多
Inspired by the profoundly observed odd-even staggering and the inverted parabolic-like shape in charge radii along calcium isotopic chain,the ground state properties of calcium isotopes are investigated by constraini...Inspired by the profoundly observed odd-even staggering and the inverted parabolic-like shape in charge radii along calcium isotopic chain,the ground state properties of calcium isotopes are investigated by constraining the root-mean-square charge radii under the covariant energy density functionals with effective forces NL3 and PK1.In this work,the pairing correlations are tackled by solving the state-dependent Bardeen-Cooper-Schrieffer equations.The calculated results suggest that the binding energies obtained by the radius constraint method have been slightly changed by about 0.2%.But for charge radii,the corresponding results deriving from NL3 and PK1 forces have been increased by about 1.0%and 2.0%,respectively.This means that the charge radius is a more sensitive quantity in the calibrated protocol.Meanwhile,it is found that the reproduced charge radii of calcium isotopes are attributed to the rather strong isospin dependence of effective potential.The odd-even oscillation behavior can also be presented in the proton Fermi energies along calcium isotopic family,but keep opposite trends with respect to the corresponding binding energies and charge radii.As encountered in charge radii,the weakened odd-even oscillation behavior still emerged from the proton Fermi energies at the neutron numbers N=20 and 28 as well,but not in binding energies.展开更多
We investigate the quantum phase transitions(QPTs)of the two-qubit quantum Rabi model with staggered qubit biases.In the limit of an infinite qubit-to-cavity frequency ratio,we analytically derive the mean-field Hamil...We investigate the quantum phase transitions(QPTs)of the two-qubit quantum Rabi model with staggered qubit biases.In the limit of an infinite qubit-to-cavity frequency ratio,we analytically derive the mean-field Hamiltonian and the order-parameter-dependent energy density functional,which yields the ground-state energy and order parameter.The rich superradiant phase transitions(SRPTs),including both second-and first-order QPTs and a tricritical point(TCP),are analytically derived.Specifically,we derive the analytical expressions for all phase transition points,including the nonperturbative point of the first-order SRPT.The analytical findings are further corroborated by numerical finite-size scaling analysis.It is found that both the critical correlation-length and order-parameter exponents at the TCP differ from those of the original second-order SRPTs,implying that the TCP belongs to a new universality class.This work provides a reliable theoretical framework for designing new,simple experimental platforms to explore the rich QPTs.展开更多
The numerical dispersion and computational cost are high for conventional Taylor series expansion staggered-grid finite-difference forward modeling owing to the high frequency of the wavelets and the large grid interv...The numerical dispersion and computational cost are high for conventional Taylor series expansion staggered-grid finite-difference forward modeling owing to the high frequency of the wavelets and the large grid intervals. In this study, the cosine-modulated binomial window function （CMBWF）-based staggered-grid finite-difference method is proposed. Two new parameters, the modulated time and modulated range are used in the new window function and by adjusting these two parameters we obtain different characteristics of the main and side lobes of the amplitude response. Numerical dispersion analysis and elastic wavefield forward modeling suggests that the CMBWF method is more precise and less computationally costly than the conventional Taylor series expansion staggered-grid finite-difference method.展开更多
Numerical simulations of a seismic wavefield are important to analyze seismic wave propagation. Elastic-wave equations are used in data simulation for modeling migration and imaging. In elastic wavefield numerical mod...Numerical simulations of a seismic wavefield are important to analyze seismic wave propagation. Elastic-wave equations are used in data simulation for modeling migration and imaging. In elastic wavefield numerical modeling, the rotated staggered-grid method （RSM） is a modification of the standard staggered-grid method （SSM）. The variable-order method is based on the method of variable-length spatial operators and wavefield propagation, and it calculates the real dispersion error by adapting different finite-difference orders to different velocities. In this study, the variable-order rotated staggered-grid method （VRSM） is developed after applying the variable-order method to RSM to solve the numerical dispersion problem of RSM in low-velocity regions and reduce the computation cost. Moreover, based on theoretical dispersion and the real dispersion error of wave propagation calculated with the wave separation method, the application of the original method is extended from acoustic to shear waves, and the calculation is modified from theoretical to time-varying values. A layered model and an overthrust model are used to demonstrate the applicability of VRSM. We also evaluate the order distribution, wave propagation, and computation time. The results suggest that the VRSM order distribution is reasonable and VRSM produces high-precision results with a minimal computation cost.展开更多
Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments a...Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.展开更多
Finite-difference(FD) methods are widely used in seismic forward modeling owing to their computational efficiency but are not readily applicable to irregular topographies. Thus, several FD methods based on the transfo...Finite-difference(FD) methods are widely used in seismic forward modeling owing to their computational efficiency but are not readily applicable to irregular topographies. Thus, several FD methods based on the transformation to curvilinear coordinates using body-fitted grids have been proposed, e.g., stand staggered grid(SSG) with interpolation, nonstaggered grid, rotated staggered grid(RSG), and fully staggered. The FD based on the RSG is somewhat superior to others because it satisfies the spatial distribution of the wave equation without additional memory and computational requirements; furthermore, it is simpler to implement. We use the RSG FD method to transform the firstorder stress–velocity equation in the curvilinear coordinates system and introduce the highprecision adaptive, unilateral mimetic finite-difference(UMFD) method to process the freeboundary conditions of an irregular surface. The numerical results suggest that the precision of the solution is higher than that of the vacuum formalism. When the minimum wavelength is low, UMFD avoids the surface wave dispersion. We compare FD methods based on RSG, SEM, and nonstaggered grid and infer that all simulation results are consistent but the computational efficiency of the RSG FD method is higher than the rest.展开更多
基金Project(JQ2022E004)supported by the Natural Science Foundation of Heilongjiang Province,China。
文摘Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered extrusion(SE)process was used to form the curved profile of AZ31 magnesium alloy in this paper.The study investigates the mapping relationship between the curvature,microstructure,and mechanical properties of the formed profiles by using different eccentricities of the die.Scanning electron microscopy(SEM)and electron backscatter diffraction techniques are employed to examine the effects of different eccentricity values(e)on grain morphology,recrystallization mechanisms,texture,and Schmid factors of the products.The results demonstrate that the staggered extrusion method promotes the deep refinement of grain size in the extruded products,with an average grain size of only 15%of the original billet,reaching 12.28μm.The tensile strength and elongation of the curved profiles after extrusion under the eccentricity value of 10 mm,20 mm and 30 mm are significantly higher than those of the billet,with the tensile strength is increased to 250,270,235 MPa,and the engineering strain elongation increased to 10.5%,12.1%,15.9%.This indicates that staggered extrusion enables curvature control of the profiles while improving their strength.
基金funded by the National Natural Science Foundation of China(Nos.52202443,52275114)the China Postdoctoral Science Foundation(No.2023M731656)+3 种基金the National Key Laboratory of Helicopter Aeromechanics Foundation,China(No.2023-HA-LB-067-05e)the Natural Science Foundation of Jiangsu Province,China(No.BK20220898)the Jiangsu Funding Program for Excellent Postdoctoral Talent,China(No.JB0202003)the Aeronautical Science Foundation of China(No.20232010052002)。
文摘With the widespread application of Staggered Counter-rotating Rotor(SCR)systems in eVTOL and UAV configurations,a comprehensive understanding of SCR performance under Outof-Ground Effect(OGE)and In-Ground Effect(IGE)conditions is crucial for aircraft design and landing safety.This study experimentally measured the changes in thrust and torque of the upper and lower rotors in an SCR system under varying axial and radial distances.It focuses on the interaction mechanisms between the upper and lower rotors and conducts specific IGE state experiments for certain SCR configurations.The findings reveal that changes in the lower rotor predominantly influence the overall performance of the SCR system,regardless of OGE or IGE conditions.Under OGE conditions,radial distance has a more significant impact than axial distance.Conversely,under IGE conditions,the axial distance plays a critical role in improving SCR system performance.These results provide a broad parameter range to assess SCR system performance variations,offering guidance for the design of new concept rotorcraft configurations and the development of aerodynamic prediction models under IGE conditions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12372251 and 12132015).
文摘The lattice Boltzmann method(LBM)is employed to simulate flow around two staggered cylinders within a confined channel.The numerical model is validated against existing experimental data by comparing drag coefficients and Strouhal numbers in the single-cylinder configuration.The study systematically investigates the influence of vertical(h)and horizontal(l)spacing between the cylinders,as well as the Reynolds number(Re=0.1–160),on the hydrodynamic forces,streamline patterns,and vortex dynamics.Results indicate that reducing the horizontal spacing l suppresses flow separation behind the upstream cylinder,while either excessively small or large vertical spacing h diminishes separation in the downstream cylinder.The onset of periodic vortex shedding is delayed due to inter-cylinder interactions,with the critical Reynolds number increasing to Rec=71–112,significantly higher than that of a single-cylinder case(Re_(c)≈69).During the vortex shedding regime,the downstream cylinder exhibits a greater lift force fluctuation compared to the upstream cylinder.At Re=160,the root-mean-square lift coefficient(C′_(L))ranges from approximately 0.17 to 0.56 for the downstream cylinder,and from 0.018 to 0.4 for the upstream one.The shedding frequency,characterized by the Strouhal number(St),increases with Reynolds number,reaching St=0.12–0.18 at Re=160.Variations in h and l significantly influence St,with a decrease in l or an increase in h lowering the shedding frequency—this effect is more pronounced in the horizontal direction.
基金supported by the National Natural Science Foundation of China(with Grant Nos.12432003 and 12032001)the National Science and Technology Major Project(Grant No.J2022-V-0003-0029).
文摘Natural biomaterials with staggered structures exhibit remarkable mechanical properties owing to their unique microstructure.The microstructural arrangement can induce size-dependent and viscoelastic responses within the material.This study proposes a strain gradient viscoelastic shear-lag model to elucidate the intricate interplay between the strain gradient and viscoelastic effect in staggered shells.Our model clarifies the role of both effects,as experimentally observed,in governing the mechanical properties of these biomaterials.A detailed characterization of the size-dependent responses is conducted through the utilization of a microstructural characterization parameter alongside viscoelastic constitutive models.Then,the effective modulus of the staggered shell is defined and its formula is derived through the Laplace transform.Compared to classical models and even the strain gradient elastic model,the strain gradient viscoelastic model offers calculated moduli that are more consistent with experimental data.Moreover,the strengthening-softening effect of staggered structures is predicted using the strain gradient viscoelastic model and critical energy principle.This study contributes significantly to our understanding of the mechanical behavior of structural materials.Additionally,it provides insights for the design of advanced bionic materials with tailored properties.
基金supported by the Natural Science Foundation of Ningxia Province,China(No.2024AAC03015)the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology,No.NLK2023-05+9 种基金the Central Government Guidance Funds for Local Scientific and Technological Development,China(No.Guike ZY22096024)the Key Laboratory of Beam Technology of Ministry of Education,China(No.BEAM2024G04)the National Natural Science Foundation of China under Grants No.11705118,No.12175151the Major Project of the GuangDong Basic and Applied Basic Research Foundation(2021B0301030006)NT is grateful for the support of the key research and development project of Ningxia(Grant No.2024BEH04090)the Key Laboratory of Beam Technology of Ministry of Education,China(No.BEAM2024G05)the National Natural Science Foundation of China under Grants No.12275025,No.11975096the Fundamental Research Funds for the Central Universities(2020NTST06)supported by the National Key R&D Program of China under Grant No.2023YFA1606401the National Natural Science Foundation of China under Grants No.12135004,No.11635003,No.11961141004.
文摘Inspired by the profoundly observed odd-even staggering and the inverted parabolic-like shape in charge radii along calcium isotopic chain,the ground state properties of calcium isotopes are investigated by constraining the root-mean-square charge radii under the covariant energy density functionals with effective forces NL3 and PK1.In this work,the pairing correlations are tackled by solving the state-dependent Bardeen-Cooper-Schrieffer equations.The calculated results suggest that the binding energies obtained by the radius constraint method have been slightly changed by about 0.2%.But for charge radii,the corresponding results deriving from NL3 and PK1 forces have been increased by about 1.0%and 2.0%,respectively.This means that the charge radius is a more sensitive quantity in the calibrated protocol.Meanwhile,it is found that the reproduced charge radii of calcium isotopes are attributed to the rather strong isospin dependence of effective potential.The odd-even oscillation behavior can also be presented in the proton Fermi energies along calcium isotopic family,but keep opposite trends with respect to the corresponding binding energies and charge radii.As encountered in charge radii,the weakened odd-even oscillation behavior still emerged from the proton Fermi energies at the neutron numbers N=20 and 28 as well,but not in binding energies.
基金supported by the National Science Foundation of China under Grants No.12105001the Natural Science Foundation of Anhui Province under Grant No.2108085QA24supported by the National Key R&D Program of China under Grants No.2024YFA1408900。
文摘We investigate the quantum phase transitions(QPTs)of the two-qubit quantum Rabi model with staggered qubit biases.In the limit of an infinite qubit-to-cavity frequency ratio,we analytically derive the mean-field Hamiltonian and the order-parameter-dependent energy density functional,which yields the ground-state energy and order parameter.The rich superradiant phase transitions(SRPTs),including both second-and first-order QPTs and a tricritical point(TCP),are analytically derived.Specifically,we derive the analytical expressions for all phase transition points,including the nonperturbative point of the first-order SRPT.The analytical findings are further corroborated by numerical finite-size scaling analysis.It is found that both the critical correlation-length and order-parameter exponents at the TCP differ from those of the original second-order SRPTs,implying that the TCP belongs to a new universality class.This work provides a reliable theoretical framework for designing new,simple experimental platforms to explore the rich QPTs.
基金supported by the National Major Research Equipment Development Projects(No.ZDYZ2012-1-02-04)the National Natural Science Foundation of China(No.41474106)
文摘The numerical dispersion and computational cost are high for conventional Taylor series expansion staggered-grid finite-difference forward modeling owing to the high frequency of the wavelets and the large grid intervals. In this study, the cosine-modulated binomial window function （CMBWF）-based staggered-grid finite-difference method is proposed. Two new parameters, the modulated time and modulated range are used in the new window function and by adjusting these two parameters we obtain different characteristics of the main and side lobes of the amplitude response. Numerical dispersion analysis and elastic wavefield forward modeling suggests that the CMBWF method is more precise and less computationally costly than the conventional Taylor series expansion staggered-grid finite-difference method.
基金supported by the National Science and Technology Major Project of China(No.2011ZX05004-003)the National Basic Research Program of China(No.2013CB228602)the National High Tech Research Program of China(No.2013AA064202)
文摘Numerical simulations of a seismic wavefield are important to analyze seismic wave propagation. Elastic-wave equations are used in data simulation for modeling migration and imaging. In elastic wavefield numerical modeling, the rotated staggered-grid method （RSM） is a modification of the standard staggered-grid method （SSM）. The variable-order method is based on the method of variable-length spatial operators and wavefield propagation, and it calculates the real dispersion error by adapting different finite-difference orders to different velocities. In this study, the variable-order rotated staggered-grid method （VRSM） is developed after applying the variable-order method to RSM to solve the numerical dispersion problem of RSM in low-velocity regions and reduce the computation cost. Moreover, based on theoretical dispersion and the real dispersion error of wave propagation calculated with the wave separation method, the application of the original method is extended from acoustic to shear waves, and the calculation is modified from theoretical to time-varying values. A layered model and an overthrust model are used to demonstrate the applicability of VRSM. We also evaluate the order distribution, wave propagation, and computation time. The results suggest that the VRSM order distribution is reasonable and VRSM produces high-precision results with a minimal computation cost.
基金Supported by National Natural Science Foundation of China (Grant Nos.51621061,51139007,51409247)National Science and Technology Support Project of China(Grant No.2015BAD20B01)
文摘Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.
基金supported by the National Nature Science Foundation of China(Nos.41504102 and 41604037)National Science and Technology Major Project(No.2016ZX05015-006)Yangtze University Youth Found(No.2015cqn32)
文摘Finite-difference(FD) methods are widely used in seismic forward modeling owing to their computational efficiency but are not readily applicable to irregular topographies. Thus, several FD methods based on the transformation to curvilinear coordinates using body-fitted grids have been proposed, e.g., stand staggered grid(SSG) with interpolation, nonstaggered grid, rotated staggered grid(RSG), and fully staggered. The FD based on the RSG is somewhat superior to others because it satisfies the spatial distribution of the wave equation without additional memory and computational requirements; furthermore, it is simpler to implement. We use the RSG FD method to transform the firstorder stress–velocity equation in the curvilinear coordinates system and introduce the highprecision adaptive, unilateral mimetic finite-difference(UMFD) method to process the freeboundary conditions of an irregular surface. The numerical results suggest that the precision of the solution is higher than that of the vacuum formalism. When the minimum wavelength is low, UMFD avoids the surface wave dispersion. We compare FD methods based on RSG, SEM, and nonstaggered grid and infer that all simulation results are consistent but the computational efficiency of the RSG FD method is higher than the rest.
