A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step am...A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can be used to hydrothermal synthesize ZSM-5 zeolite without impurity phase contamination, which was confirmed by XRD, TG, SEM, BET and EDS characteristic techniques. It was found that with the increase of SiO_2/Al_2O_3 ratio and the extension of reaction time, the crystal type transform from the orthorhombic to the monoclinic phase. The impurity fluorine content of the recovered SiO_2 from H_2SiF_6 has great influence on the hydrothermal process for ZSM-5 crystal structure formation.Moreover, the increase of fluorine ions content in the hydrothermal process can control the crystal morphology and size of synthesized ZSM-5. Catalytic properties of synthesized HZSM-5 with different SiO_2/Al_2O_3 ratio in transalkylation of toluene and 1,2,4-trimethylbenzene show good and stable catalytic performance. The ZSM-5 synthesized with recovered silica source exhibits similar catalyst life as the performance of small particle size HZSM-5, because the ZSM-5 synthesized with the silica source from industrial hexafluorosilicic acid prefers a thin disk crystal along the b axis direction, which shortens the diffusion distance of generated products.展开更多
In this study, the trends in latent and sensible heat fluxes (LHF and SHF) over the Southern Ocean (oceans south of 35?S) and the contributions of the Antarctic Oscillation (AAO), the Pacific-South America teleconnect...In this study, the trends in latent and sensible heat fluxes (LHF and SHF) over the Southern Ocean (oceans south of 35?S) and the contributions of the Antarctic Oscillation (AAO), the Pacific-South America teleconnection patterns (PSA1 and PSA2) and The El Ni?o-Southern Oscillation (ENSO) to these heat fluxes were investigated using the Objectively Analyzed Air-Sea Fluxes (OAFlux) dataset from 1979 to 2008. Significant positive annual trends in LHF occur over the Agulhas Current, the Brazil Current, the oceans in the vicinity of New Zealand and southern Australia, and the eastern Pacific Ocean near between 35?S and 40?S. Significant negative seasonal trends occur in LHF which differ among the four seasons. The spatial pattern and seasonal variation of the trends in SHF over the Southern Ocean are similar to those of LHF. The spatial patterns of the trends in LHF and SHF caused by the AAO, PSA1, PSA2 and Southern Oscillation Index (SOI) indices show a wave-like feature, varying with different seasons, that can be explained by the anomalous meridional wind associated with the four indices. The above four indices account for a small portion of the trend in LHF and SHF. The residual trends in LHF over the Southern Ocean may be explained by a climate shift in the late 1990s for the four seasons. But the residual trends in SHF over the Southern Ocean are not associated with the climate shift.展开更多
The spinodal decomposition method emerges as a promising methodology,showcasing its potential in exploring the design space for metamaterial structures.However,spinodal structures design is still largely limited to re...The spinodal decomposition method emerges as a promising methodology,showcasing its potential in exploring the design space for metamaterial structures.However,spinodal structures design is still largely limited to regular structures,due to their relatively easy parameterization and controllability.Efficiently predicting the mechanical properties of 3D spinodal membrane structure remains a challenge,given that the features of the membrane necessitate adaptive mesh through the modelling process.This paper proposes an integrated approach for morphological design with customized mechanical properties,incorporating the spinodal decomposition method and adaptive coarse-grained modeling,which can produce various morphologies such as lamellar,columnar,and cubic structures.Pseudo-periodic parameterβand orientational parameterΘ(θ_(1),θ_(2),θ_(3))are identified to achieve the optimal goal of anisotropic mechanical properties.Parametric analysis is conducted to reveal the correlation between the customized spinodal structure and mechanical performance.Our work provides an integrated approach for morphological variation and tuning mechanical properties,paving the way for the design and development of customized functional materials similar to 3D spinodal membrane structures.展开更多
Surface radiative fluxes over landfast sea ice off Zhongshan station have been measured in austral spring for five springs between 2010 and 2015.Downward and upward solar radiation vary diurnally with maximum amplitud...Surface radiative fluxes over landfast sea ice off Zhongshan station have been measured in austral spring for five springs between 2010 and 2015.Downward and upward solar radiation vary diurnally with maximum amplitudes of 473 and 290 W m^(−2),respectively.The maximum and minimum long-wave radiation values of the mean diurnal cycle are 218 and 210 W m^(−2)for downward radiation,277 and 259 W m^(−2)for upward radiation and 125 and−52 W m^(−2)for net radiation.The albedo has a U-shaped mean diurnal cycle with a minimum of 0.64 at noon.Sea ice thickness is in the growth phase for most spring days,but can be disturbed by synoptic processes.The surface temperature largely determines the occurrence of ice melting.Surface downward and upward long-wave radiation show synoptic oscillations with a 5–8 day period and intraseasonal variability with a 12–45 day period.The amplitudes of the diurnal,synoptic and intraseasonal variability show some differences during the five austral springs considered here.The intraseasonal and synoptic variability of downward and upward long-wave radiation are associated with the variability of cloud cover and surface temperature induced by the atmospheric circulation.展开更多
A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small com...A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small compared to the structural scale. Different length scales should be adopted considering the efficiency and computational cost. In the principle of physics, different length scales are stipulated to correspond to different time scales. This concept lays the foundation of the framework for this multiple-time-scale algorithm. A multiple-time-scale algorithm, which involves different time steps for different regions, while enforcing the compatibility of displacement, force and stress fields across the interface, is proposed. Furthermore, a defected beam component is studied as a numerical sample. The structural component is divided into two regions： a coarse one and a fine one; a micro-defect exists in the fine region and the finite element sizes of the two regions are diametrically different. Correspondingly, two different time steps are adopted. With dynamic load applied to the beam, stress and displacement distribution of the defected beam is investigated from the global and local perspectives. The numerical sample reflects that the proposed algorithm is physically rational and computationally efficient in the potential damage simulation of civil structures.展开更多
Over Antarctica,surface fluxes play an important role in the local atmospheric dynamical processes.To reveal the surface fluxes characteristics and aerodynamic and thermal roughness lengths over Zhongshan station,Anta...Over Antarctica,surface fluxes play an important role in the local atmospheric dynamical processes.To reveal the surface fluxes characteristics and aerodynamic and thermal roughness lengths over Zhongshan station,Antarctica,this paper analyzes the data observed at the station during 3 March 2008 through 15 February 2009.It is found that easterlies dominated this site throughout the whole year,with a maximum(average)speed of 25(5.6)m s−1 at 3.9 m height,and the annual maximum(minimum)surface temperature reached 291.05(230.05)K,while the annual maximum(minimum)air-specific humidity was 4.1(0.05)g/kg at 3.9 m height.The maximum(minimum)values of seasonal mean temperature,humidity,each radiation components,sensible and latent heat flux occurred in summer(winter),while for the seasonal averaged wind speed andτthe minimums(maximums)appeared in summer(autumn).After comparing with a partially linear regression method for aerodynamic roughness length and four previous equations that derive thermal roughness length from surface Reynolds number,constant values of aerodynamic roughness length as 3.6×10^(−3)m and thermal roughness length as 1.2×10^(−4)m at this site were validated by using the other three level observations and suggested for future studies.展开更多
Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two...Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.展开更多
The utilization of piezoelectric materials in MEMS devices under harsh environments has gained affordable appreciations due to its unique mechanical and electrical material properties.However,the reliability of MEMS d...The utilization of piezoelectric materials in MEMS devices under harsh environments has gained affordable appreciations due to its unique mechanical and electrical material properties.However,the reliability of MEMS devices triggered by fatigue damage remains elusive and needs to be further explored.Here,we present a continuum constitutive model for piezoelectric materials containing a substantive amount of randomly dispersed microcracks.The constitutive equation of the piezoelectric materials with microcracks is formulated via Helmholtz free energy by combining the Kachanvo damage evolution law and the Chaboche fatigue damage development to express the fatigue damage growth.A case of the fatigue damage analysis of the piezoelectric microplate with transverse matrix cracks in the status of plane stress is presented by adopting the von Karman’s plate theory.With numerical schemes employed,the effect of cyclic impulsive loadings and electrical loadings on the fatigue damage and fatigue life prediction of a piezoelectric microplate is investigated and discussed.The findings provide valuable insights into the fundamental mechanism of reliability in piezoelectric MEMS devices due to cyclic loadings,thereby offering new ways to exploit and fabricate the piezoelectric-based MEMS devices suitable for harsh conditions.展开更多
The phenomena of buckyball-graphene collisions were investigated by classical molecular dynamics(MD)simulation using the empirical Tersoff potential.Three cases were investigated:collisions between a buckyball and a s...The phenomena of buckyball-graphene collisions were investigated by classical molecular dynamics(MD)simulation using the empirical Tersoff potential.Three cases were investigated:collisions between a buckyball and a single-layer graphene;collisions between a nano-onion(a double-layer concentric spherical nanostructure:a C_(60) in a C_(320))and a single-layer graphene;collisions between a nano-onion and a double-layer graphene.The impact velocity of the buckyball or nano-onion ranged from 4.37 km/s to 15.31 km/s.Simulation results for the buckyball-graphene collisions show that the buckyball bounces back when the impact velocity is less than 8.75 km/s,sticks to the graphene when the impact velocity is between 8.75 km/s and 12.03 km/s,and breaks when the impact velocity is greater than 12.03 km/s.Similar phenomena are observed for the other two cases.A single buckyball can never go through a single-layer graphene intact;however,the inner structure(C_(60))of a nano-onion can penetrate through a single-layer graphene without any damage.The energy evolution during the whole simulation process was also studied.展开更多
基金Supported by the National Natural Science Foundation of China(21306143)the Educational Commission of Hubei Province of China(D20161503)the Hubei Province Phosphorus Resource and Ethylene Project Downstream Exploitation Collaborative Innovation Center
文摘A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can be used to hydrothermal synthesize ZSM-5 zeolite without impurity phase contamination, which was confirmed by XRD, TG, SEM, BET and EDS characteristic techniques. It was found that with the increase of SiO_2/Al_2O_3 ratio and the extension of reaction time, the crystal type transform from the orthorhombic to the monoclinic phase. The impurity fluorine content of the recovered SiO_2 from H_2SiF_6 has great influence on the hydrothermal process for ZSM-5 crystal structure formation.Moreover, the increase of fluorine ions content in the hydrothermal process can control the crystal morphology and size of synthesized ZSM-5. Catalytic properties of synthesized HZSM-5 with different SiO_2/Al_2O_3 ratio in transalkylation of toluene and 1,2,4-trimethylbenzene show good and stable catalytic performance. The ZSM-5 synthesized with recovered silica source exhibits similar catalyst life as the performance of small particle size HZSM-5, because the ZSM-5 synthesized with the silica source from industrial hexafluorosilicic acid prefers a thin disk crystal along the b axis direction, which shortens the diffusion distance of generated products.
基金supported by the National Natural Science Foundation(41175010,40930848 and 41106164)Marine Public Welfare Project(201205007)+1 种基金National Program on Key Basic Research Project of China(2010CB950301)sponsored by the National Science Foundation
文摘In this study, the trends in latent and sensible heat fluxes (LHF and SHF) over the Southern Ocean (oceans south of 35?S) and the contributions of the Antarctic Oscillation (AAO), the Pacific-South America teleconnection patterns (PSA1 and PSA2) and The El Ni?o-Southern Oscillation (ENSO) to these heat fluxes were investigated using the Objectively Analyzed Air-Sea Fluxes (OAFlux) dataset from 1979 to 2008. Significant positive annual trends in LHF occur over the Agulhas Current, the Brazil Current, the oceans in the vicinity of New Zealand and southern Australia, and the eastern Pacific Ocean near between 35?S and 40?S. Significant negative seasonal trends occur in LHF which differ among the four seasons. The spatial pattern and seasonal variation of the trends in SHF over the Southern Ocean are similar to those of LHF. The spatial patterns of the trends in LHF and SHF caused by the AAO, PSA1, PSA2 and Southern Oscillation Index (SOI) indices show a wave-like feature, varying with different seasons, that can be explained by the anomalous meridional wind associated with the four indices. The above four indices account for a small portion of the trend in LHF and SHF. The residual trends in LHF over the Southern Ocean may be explained by a climate shift in the late 1990s for the four seasons. But the residual trends in SHF over the Southern Ocean are not associated with the climate shift.
基金supported by the National Natural Science Foundation of China(Grant No.11872278)the Science and Technology Commission of Shanghai Municipality(Grant No.21ZR1467200)the Fundamental Research Funds for the Central Universities.
文摘The spinodal decomposition method emerges as a promising methodology,showcasing its potential in exploring the design space for metamaterial structures.However,spinodal structures design is still largely limited to regular structures,due to their relatively easy parameterization and controllability.Efficiently predicting the mechanical properties of 3D spinodal membrane structure remains a challenge,given that the features of the membrane necessitate adaptive mesh through the modelling process.This paper proposes an integrated approach for morphological design with customized mechanical properties,incorporating the spinodal decomposition method and adaptive coarse-grained modeling,which can produce various morphologies such as lamellar,columnar,and cubic structures.Pseudo-periodic parameterβand orientational parameterΘ(θ_(1),θ_(2),θ_(3))are identified to achieve the optimal goal of anisotropic mechanical properties.Parametric analysis is conducted to reveal the correlation between the customized spinodal structure and mechanical performance.Our work provides an integrated approach for morphological variation and tuning mechanical properties,paving the way for the design and development of customized functional materials similar to 3D spinodal membrane structures.
基金the National Natural Science Foundation of China[nos.41376005,41606222]the Chinese Polar Environmental Comprehensive Investigation and Assessment Program under contract[no.CHINARE2017-04-04]The National Center for Atmospheric Research is sponsored by the U.S.National Science Foundation.
文摘Surface radiative fluxes over landfast sea ice off Zhongshan station have been measured in austral spring for five springs between 2010 and 2015.Downward and upward solar radiation vary diurnally with maximum amplitudes of 473 and 290 W m^(−2),respectively.The maximum and minimum long-wave radiation values of the mean diurnal cycle are 218 and 210 W m^(−2)for downward radiation,277 and 259 W m^(−2)for upward radiation and 125 and−52 W m^(−2)for net radiation.The albedo has a U-shaped mean diurnal cycle with a minimum of 0.64 at noon.Sea ice thickness is in the growth phase for most spring days,but can be disturbed by synoptic processes.The surface temperature largely determines the occurrence of ice melting.Surface downward and upward long-wave radiation show synoptic oscillations with a 5–8 day period and intraseasonal variability with a 12–45 day period.The amplitudes of the diurnal,synoptic and intraseasonal variability show some differences during the five austral springs considered here.The intraseasonal and synoptic variability of downward and upward long-wave radiation are associated with the variability of cloud cover and surface temperature induced by the atmospheric circulation.
基金supports from NSFC(No.11302078)China Postdoctoral Science Foundation(No.2013M531139)Shanghai Postdoctoral Sustentation Fund(No.12R21412000)
文摘A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small compared to the structural scale. Different length scales should be adopted considering the efficiency and computational cost. In the principle of physics, different length scales are stipulated to correspond to different time scales. This concept lays the foundation of the framework for this multiple-time-scale algorithm. A multiple-time-scale algorithm, which involves different time steps for different regions, while enforcing the compatibility of displacement, force and stress fields across the interface, is proposed. Furthermore, a defected beam component is studied as a numerical sample. The structural component is divided into two regions： a coarse one and a fine one; a micro-defect exists in the fine region and the finite element sizes of the two regions are diametrically different. Correspondingly, two different time steps are adopted. With dynamic load applied to the beam, stress and displacement distribution of the defected beam is investigated from the global and local perspectives. The numerical sample reflects that the proposed algorithm is physically rational and computationally efficient in the potential damage simulation of civil structures.
基金the National Natural Science Foundation of China(Grant Nos.41376005 and 41505004)the National Key Projects of Ministry of Science and Technology of China(2016YFA0602100)+1 种基金the Chinese Polar Environmental Comprehensive Investigation and Assessment Program,and the Open Project Program(KLME1508)the Key Laboratory of Meteorological Disaster of Ministry of Education at Nanjing University of Information Science and Technology。
文摘Over Antarctica,surface fluxes play an important role in the local atmospheric dynamical processes.To reveal the surface fluxes characteristics and aerodynamic and thermal roughness lengths over Zhongshan station,Antarctica,this paper analyzes the data observed at the station during 3 March 2008 through 15 February 2009.It is found that easterlies dominated this site throughout the whole year,with a maximum(average)speed of 25(5.6)m s−1 at 3.9 m height,and the annual maximum(minimum)surface temperature reached 291.05(230.05)K,while the annual maximum(minimum)air-specific humidity was 4.1(0.05)g/kg at 3.9 m height.The maximum(minimum)values of seasonal mean temperature,humidity,each radiation components,sensible and latent heat flux occurred in summer(winter),while for the seasonal averaged wind speed andτthe minimums(maximums)appeared in summer(autumn).After comparing with a partially linear regression method for aerodynamic roughness length and four previous equations that derive thermal roughness length from surface Reynolds number,constant values of aerodynamic roughness length as 3.6×10^(−3)m and thermal roughness length as 1.2×10^(−4)m at this site were validated by using the other three level observations and suggested for future studies.
文摘Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.
文摘The utilization of piezoelectric materials in MEMS devices under harsh environments has gained affordable appreciations due to its unique mechanical and electrical material properties.However,the reliability of MEMS devices triggered by fatigue damage remains elusive and needs to be further explored.Here,we present a continuum constitutive model for piezoelectric materials containing a substantive amount of randomly dispersed microcracks.The constitutive equation of the piezoelectric materials with microcracks is formulated via Helmholtz free energy by combining the Kachanvo damage evolution law and the Chaboche fatigue damage development to express the fatigue damage growth.A case of the fatigue damage analysis of the piezoelectric microplate with transverse matrix cracks in the status of plane stress is presented by adopting the von Karman’s plate theory.With numerical schemes employed,the effect of cyclic impulsive loadings and electrical loadings on the fatigue damage and fatigue life prediction of a piezoelectric microplate is investigated and discussed.The findings provide valuable insights into the fundamental mechanism of reliability in piezoelectric MEMS devices due to cyclic loadings,thereby offering new ways to exploit and fabricate the piezoelectric-based MEMS devices suitable for harsh conditions.
文摘The phenomena of buckyball-graphene collisions were investigated by classical molecular dynamics(MD)simulation using the empirical Tersoff potential.Three cases were investigated:collisions between a buckyball and a single-layer graphene;collisions between a nano-onion(a double-layer concentric spherical nanostructure:a C_(60) in a C_(320))and a single-layer graphene;collisions between a nano-onion and a double-layer graphene.The impact velocity of the buckyball or nano-onion ranged from 4.37 km/s to 15.31 km/s.Simulation results for the buckyball-graphene collisions show that the buckyball bounces back when the impact velocity is less than 8.75 km/s,sticks to the graphene when the impact velocity is between 8.75 km/s and 12.03 km/s,and breaks when the impact velocity is greater than 12.03 km/s.Similar phenomena are observed for the other two cases.A single buckyball can never go through a single-layer graphene intact;however,the inner structure(C_(60))of a nano-onion can penetrate through a single-layer graphene without any damage.The energy evolution during the whole simulation process was also studied.
