Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting i...Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting in the high assembly cost.This paper presents a novel tractive-magnetic-coupling(TMC)and its application on a 2D electro-hydraulic proportional flow valve(2D-EHPFV),whose configuration not only fulfill the requirements of 2D valve,but also oriented to integral-magnetization-process.To investigate the output torque of TMC,a detailed analytical model considering leakage flux,edge effect and tooth magnetic saturation is formulated based on the equivalent magnetic circuit method.To facilitate the magnetic saturation calculation,a special magnetic permeability database is established for tooth region of TMC using Ansoft/Maxwell software.Prototype of TMC is machined and an exclusive experimental platform is built.Torque-displacement characteristics under different working airgap and tooth number are measured.The experimental results are in good agreement with the analytical results,which verifies the correctness of the analytical model.Then the TMC is integrated into the 2D-EHPFV by replacing the repulsive-magnetic-coupling.Prototype of 2D-EHPFV is designed and manufactured to test the no-load flow characteristics,load flow characteristics,leakage characteristics,frequency characteristics and step response.Under working pressure of 15 MPa,the maximum no-load flow rate is 82.2 L/min with the hysteresis of 2.6%,and the amplitude and phase frequency width is 21.6 Hz,and 28.9 Hz.The detailed experimental results show that TMC can be applied to 2D valves to form 2D-EHPFV,which can reduce hysteresis and cost,and improve response speed.展开更多
A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are con...A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are converted into the frequency domain coefficient matrices(FDCM) with discrete cosine transform(DCT) operation. After that, a twodimensional(2D) coupled chaotic system is developed and used to generate one group of embedded matrices and another group of encryption matrices, respectively. The embedded matrices are integrated with the FDCM to fulfill the frequency domain encryption, and then the inverse DCT processing is implemented to recover the spatial domain signal. Eventually,under the function of the encryption matrices and the proposed diagonal scrambling algorithm, the final color ciphertext is obtained. The experimental results show that the proposed method can not only ensure efficient encryption but also satisfy various sizes of image encryption. Besides, it has better performance than other similar techniques in statistical feature analysis, such as key space, key sensitivity, anti-differential attack, information entropy, noise attack, etc.展开更多
In order to consider the influence of temperature and underground water movement, an elastoplastic model and a 2D FEM stress fields on the migration of radioactive nuclide with code for analysis of coupled thermo-hyd...In order to consider the influence of temperature and underground water movement, an elastoplastic model and a 2D FEM stress fields on the migration of radioactive nuclide with code for analysis of coupled thermo-hydro-mechanical （THM） processes in saturated and unsaturated porous media were extended and improved through introducing the percolation and migration equation, so that the code can be used for solving the temperature field, flow field, stress field and nuclide concentration field simultaneously. The states of temperatures, pore pressures and nuclide concentrations in the near field of a hypothetical nuclear waste repository were investigated. The influence of the half life of the radioactive nuclide on the temporal change of nuclide concentration was analyzed considering the thermo-hydro-mechanical-migratory coupling. The results show that, at the boundary of the vitrified waste, the concentration of radioactive nuclide with a half life of 10 a falls after a period of rising, with the maximum value of 0.182 mol/m3 and the minimum value of 0.181 mol/m^3 at the end of computation. For a half life of 1 000 a, the concentration of radioactive nuclide always increases with the increase of the time during the computation period; and the maximum value is 1.686 mol/m^3 at the end of the computation. Therefore, under the condition of THM coupling, the concentration of radioactive nuclide with a shorter half life will decrease more quickly with water flow; but for the radioactive nuclide with a longer half life, its concentration will keep at a higher level for a longer time in the migration process.展开更多
As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.B...As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.展开更多
The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional the...The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional theory method,a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted.The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions.Importantly,the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin-orbit coupling energy gap of 1.2 meV,which has an intrinsic Dirac cone arising from the special hexagonal lattice structure.Hole doping leads to the spin polarization of the electron,which results in a Dirac half-metal feature with single-spin Dirac fermion.This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.展开更多
Due to the high population density and economic property in urban environments,urban flooding can result in substantial economic losses.However,accurate urban flood modeling and assessing the associated damages are ch...Due to the high population density and economic property in urban environments,urban flooding can result in substantial economic losses.However,accurate urban flood modeling and assessing the associated damages are challenging due to complex urban layouts and rugged topography.Furthermore,the rapid development of urban underground spaces has introduced additional complexities.To address the demanding need for accurate flood modeling and damage assessment in cities,a fine-scale flood damage assessment method was proposed in this study,based on the 1D/2D coupled hydrodynamic model,which can not only assess the flood damage on the ground surface but also evaluate the flood loss in underground spaces.Taking the Gangxi drainage area in Wuhan City,China as a case,this study extensively discussed the flood inundation processes on the ground surface as well as in the buildings and underground spaces,under different rainfall scenarios with the return period ranging from 2 to 200 years.Based on the high spatial-temporal hydrodynamic simulations,the flood damage degrees were evaluated for the buildings and underground spaces with different industry types.The results indicated that the inundation of buildings and underground spaces in densely built cities cannot be neglected in urban flood modeling.Buildings with public service attributes can have a higher flood damage degree,as compared with other types of buildings and underground spaces.展开更多
Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an a...Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an arbitrary functionφ(y),a family of deformed soliton and deformed breather solutions are presented with the improved Hirota’s bilinear method.By choosing the appropriate parameters,their interesting dynamic behaviors are shown in three-dimensional plots.Furthermore,novel rational solutions are generated by taking the limit of the obtained solitons.Additionally,twodimensional(2D)rogue waves(localized in both space and time)on the soliton plane are presented,we refer to them as deformed 2D rogue waves.The obtained deformed 2D rogue waves can be viewed as a 2D analog of the Peregrine soliton on soliton plane,and its evolution process is analyzed in detail.The deformed 2D rogue wave solutions are constructed successfully,which are closely related to the arbitrary functionφ(y).This new idea is also applicable to other nonlinear systems.展开更多
Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and ...Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and Fe_(3)GeTe_(2) opens up a new chapter in the remarkable field of two-dimensional materials.Here,we report on a theoretical analysis of the stability of ferromagnetism in Fe_(3)GeTe_(2).We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of Fe_(3)GeTe_(2).Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems.The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.展开更多
In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method a...In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method and targeted long narrow reaches of the river networks, while the 2D model targeted broad channels and embayment and solved the 2D shallow-water equations using a semi-implicit scheme applied to an unstructured grid of triangular cells. The 1D and 2D models were solved simultaneously by building a matrix for the free surface elevation at every 1D junction and 2D cell center. Velocities were then computed explicitly based on the results at the previous time step and the updated water level. The originality of the scheme arose from a novel coupling method. The results showed that the coupled 1D/2D model produced identical results as the full 2D model in classical to benchmark problems with considerable savings in computational effort. Application of the model to the Pearl River Estuary in southern China showed that complex patterns of tidal wave propagation could be efficiently modeled.展开更多
Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostruct...Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostructural to MnBi_(2)Te_(4),has been synthesized in experiments,but its detailed magnetic ordering and band topology have not been clearly understood yet.Here,based on first-principles calculations,we investigate the magnetic and electronic properties of FeBi_(2)Te_(4)in bulk and 2D forms.We show that different from MnBi_(2)Te_(4),the magnetic ground states of bulk,single-layer,and bilayer FeBi_(2)Te_(4)all favor a 120°noncollinear antiferromagnetic ordering,and they are topologically trivial narrow-gap semiconductors.For the bilayer case,we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state,which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling.Our work clarifies the physical properties of the new material system of FeBi_(2)Te_(4)and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.展开更多
This paper points out that a successful numerical simulation is to construct a correct conceptional model which is very dose to the natural condition. A new model, two dimensional coupled three dimensional model (2D -...This paper points out that a successful numerical simulation is to construct a correct conceptional model which is very dose to the natural condition. A new model, two dimensional coupled three dimensional model (2D -3D ) is presented in the Present paper,which is the most suitable one for the dual - structured - aquifer system. An example of Wenyinghu area is shown.By using the 2D-3D model, a satisfied result of the simulated area is achieved.展开更多
To investigate the bedding influence on coal mechanical behaviour in underground environments such as coal or rock burst, simulations of dynamic SHPB tests of pre-stressed coal specimens with different bedding angles ...To investigate the bedding influence on coal mechanical behaviour in underground environments such as coal or rock burst, simulations of dynamic SHPB tests of pre-stressed coal specimens with different bedding angles were carried out using a particle flow code 2-dimensional(PFC2D). Three impact velocities of 4, 8 and 12 m/s were selected to study dynamic behaviours of coal containing bedding planes under different dynamic loads. The simulation results showed that the existence of bedding planes leads to the degradation of the mechanical properties and their weakening effect significantly depends on the angle h between the bedding planes and load direction. With h increaseing from 0° to 90°, the strength first decreased and subsequently increased and specimens became most vulnerable when h was 30° or 45°.Five failure modes were observed in the specimens in the context of macro-cracks. Furthermore, energy characteristics combined with ultimate failure patterns revealed that maximum accumulated energy and failure intensity have a positive relation with the strength of specimen. When bedding planes were parallel or perpendicular to loading direction, specimens absorbed more energy and experienced more violent failure with increased number of cracks. In contrast, bedding planes with h of 30° or 45° reduced the specimens' ability of storing strain energy to the lowest with fewer cracks observed after failure.展开更多
A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction be...A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction between the nanoplates and the elastic medium. The exact solutions of the nonlocal vibration frequency and buckling critical load of the 2 D decagonal QC layered nanoplates are obtained by solving the eigensystem and using the propagator matrix method. The present three-dimensional(3 D) exact solution can predict correctly the nature frequencies and critical loads of the nanoplates as compared with previous thin-plate and medium-thick-plate theories.Numerical examples are provided to display the effects of the quasiperiodic direction,length-to-width ratio, thickness of the nanoplates, nonlocal parameter, stacking sequence,and medium elasticity on the vibration frequency and critical buckling load of the 2 D decagonal QC nanoplates. The results show that the effects of the quasiperiodic direction on the vibration frequency and critical buckling load depend on the length-to-width ratio of the nanoplates. The thickness of the nanoplate and the elasticity of the surrounding medium can be adjusted for optimal frequency and critical buckling load of the nanoplate.This feature is useful since the frequency and critical buckling load of the 2 D decagonal QCs as coating materials of plate structures can now be tuned as one desire.展开更多
Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and requi...Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.展开更多
Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to...Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will.Nowadays,LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion,hybrid materials or magnetism.α-Co hydroxides(Simonkolleite-like structures)are promising phases with tuneable electronic and magnetic properties by ligand modification.However,even in the simple case ofα-Co^(Ⅱ)hydroxychlorides,the preparation of well-defined large 2D crystals is not straightforward,hindering the development of fundamental studies.Herein,we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter>5μm and thickness of 20±7 nm)by a simple homogeneous synthesis taking place at room temperature.In structural terms,no differences are observed between our layered materials and those obtained hydrothermally.However,dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices,which have been rationalized with structural DFT calculations.This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based onα-CoIIhydroxides,paving the way for the development of fundamental studies and applications.展开更多
We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride,...We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride, molybdenum disulfide, and black phosphorus. Different possibilities of phonon engineering for optimization of electrical and heat conductions are discussed. The role of the phonon energy spectra modification on the thermal conductivity in semiconductor nanostructures is revealed. The dependence of thermal conductivity in graphene and related two-dimensional（2 D） materials on temperature, flake size, defect concentration, edge roughness, and strain is analyzed.展开更多
Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear ...Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.展开更多
The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained base...The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.展开更多
Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful charact...Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful characterization method to investigate the spin-related properties in 2D vdW magnets,including magnon and spin–lattice interaction,which are hardly accessible by other optical methods.In this paper,the recent progress of various magnetic properties in 2D vdW magnets studied by Raman spectroscopy is reviewed,including the magnetic transition,spin-wave,spin–lattice interaction,symmetry tuning induced by spin ordering,and nonreciprocal magneto-phonon Raman scattering.展开更多
The two-dimensional(2D) pseudo-steady isothermal flow, which is isentropic and irrotational, around a convex corner is studied. The self-similar solutions for the supersonic flow around the convex corner are construct...The two-dimensional(2D) pseudo-steady isothermal flow, which is isentropic and irrotational, around a convex corner is studied. The self-similar solutions for the supersonic flow around the convex corner are constructed, where the properties of the centered simple wave are used for the 2D isentropic irrotational pseudo-steady Euler equations. The geometric procedures of the center simple waves are given. It is proven that the supersonic flow turns the convex corner by an incomplete centered expansion wave or an incomplete centered compression wave, depending on the conditions of the downstream state.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51975524,52375067)Zhejiang Provincial Natural Science Foundation of China(Grant No.Y23E050014).
文摘Magnetization convenience is crucial consideration for design of valve magnetic actuators.The existing repulsive-magnetic-coupling of 2D maglev valve is not oriented to the integral-magnetization-processes,resulting in the high assembly cost.This paper presents a novel tractive-magnetic-coupling(TMC)and its application on a 2D electro-hydraulic proportional flow valve(2D-EHPFV),whose configuration not only fulfill the requirements of 2D valve,but also oriented to integral-magnetization-process.To investigate the output torque of TMC,a detailed analytical model considering leakage flux,edge effect and tooth magnetic saturation is formulated based on the equivalent magnetic circuit method.To facilitate the magnetic saturation calculation,a special magnetic permeability database is established for tooth region of TMC using Ansoft/Maxwell software.Prototype of TMC is machined and an exclusive experimental platform is built.Torque-displacement characteristics under different working airgap and tooth number are measured.The experimental results are in good agreement with the analytical results,which verifies the correctness of the analytical model.Then the TMC is integrated into the 2D-EHPFV by replacing the repulsive-magnetic-coupling.Prototype of 2D-EHPFV is designed and manufactured to test the no-load flow characteristics,load flow characteristics,leakage characteristics,frequency characteristics and step response.Under working pressure of 15 MPa,the maximum no-load flow rate is 82.2 L/min with the hysteresis of 2.6%,and the amplitude and phase frequency width is 21.6 Hz,and 28.9 Hz.The detailed experimental results show that TMC can be applied to 2D valves to form 2D-EHPFV,which can reduce hysteresis and cost,and improve response speed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62105004 and 52174141)the College Student Innovation and Entrepreneurship Fund Project(Grant No.202210361053)+1 种基金Anhui Mining Machinery and Electrical Equipment Coordination Innovation Center,Anhui University of Science&Technology(Grant No.KSJD202304)the Anhui Province Digital Agricultural Engineering Technology Research Center Open Project(Grant No.AHSZNYGC-ZXKF021)。
文摘A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are converted into the frequency domain coefficient matrices(FDCM) with discrete cosine transform(DCT) operation. After that, a twodimensional(2D) coupled chaotic system is developed and used to generate one group of embedded matrices and another group of encryption matrices, respectively. The embedded matrices are integrated with the FDCM to fulfill the frequency domain encryption, and then the inverse DCT processing is implemented to recover the spatial domain signal. Eventually,under the function of the encryption matrices and the proposed diagonal scrambling algorithm, the final color ciphertext is obtained. The experimental results show that the proposed method can not only ensure efficient encryption but also satisfy various sizes of image encryption. Besides, it has better performance than other similar techniques in statistical feature analysis, such as key space, key sensitivity, anti-differential attack, information entropy, noise attack, etc.
基金Project(2010CB732101) supported by the National Basic Research Program of China Project(SKLQ 008) supported by the Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering of China
文摘In order to consider the influence of temperature and underground water movement, an elastoplastic model and a 2D FEM stress fields on the migration of radioactive nuclide with code for analysis of coupled thermo-hydro-mechanical （THM） processes in saturated and unsaturated porous media were extended and improved through introducing the percolation and migration equation, so that the code can be used for solving the temperature field, flow field, stress field and nuclide concentration field simultaneously. The states of temperatures, pore pressures and nuclide concentrations in the near field of a hypothetical nuclear waste repository were investigated. The influence of the half life of the radioactive nuclide on the temporal change of nuclide concentration was analyzed considering the thermo-hydro-mechanical-migratory coupling. The results show that, at the boundary of the vitrified waste, the concentration of radioactive nuclide with a half life of 10 a falls after a period of rising, with the maximum value of 0.182 mol/m3 and the minimum value of 0.181 mol/m^3 at the end of computation. For a half life of 1 000 a, the concentration of radioactive nuclide always increases with the increase of the time during the computation period; and the maximum value is 1.686 mol/m^3 at the end of the computation. Therefore, under the condition of THM coupling, the concentration of radioactive nuclide with a shorter half life will decrease more quickly with water flow; but for the radioactive nuclide with a longer half life, its concentration will keep at a higher level for a longer time in the migration process.
基金funded by the National Natural Science Foundation of China(Grant No.NSFC51374147)the German Society for Petroleum and Coal Science and Technology(Grant No.DGMK680-4)
文摘As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.
基金the National Natural Science Foundation of China(Grant Nos.11674136 and 11564022)Yunnan Province for Recruiting High-Caliber Technological Talents,China(Grant No.1097816002)+3 种基金Reserve Talents for Yunnan Young and Middle-aged Academic and Technical Leaders,China(Grant No.2017HB010)the Academic Qinglan Project of KUST(Grant No.1407840010)the Analysis and Testing Fund of KUST(Grant No.2017M20162230010)the High-level Talents of KUST(Grant No.1411909425)。
文摘The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional theory method,a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted.The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions.Importantly,the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin-orbit coupling energy gap of 1.2 meV,which has an intrinsic Dirac cone arising from the special hexagonal lattice structure.Hole doping leads to the spin polarization of the electron,which results in a Dirac half-metal feature with single-spin Dirac fermion.This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.
基金National Natural Science Foundation of China,Grant/Award Numbers:41890820,51725902,52209098Special Fund for Science and Technology Innovation Strategy of Guangdong Province,Grant/Award Number:gdsky2023-02+1 种基金Newton Advanced Fellowships from the NSFC and the UK Royal Society,Grant/Award Numbers:52061130219,NAF\R1\201156Science and Technology Innovation Program from Water Resources of Guangdong Province,Grant/Award Numbers:2022-01,2023-05。
文摘Due to the high population density and economic property in urban environments,urban flooding can result in substantial economic losses.However,accurate urban flood modeling and assessing the associated damages are challenging due to complex urban layouts and rugged topography.Furthermore,the rapid development of urban underground spaces has introduced additional complexities.To address the demanding need for accurate flood modeling and damage assessment in cities,a fine-scale flood damage assessment method was proposed in this study,based on the 1D/2D coupled hydrodynamic model,which can not only assess the flood damage on the ground surface but also evaluate the flood loss in underground spaces.Taking the Gangxi drainage area in Wuhan City,China as a case,this study extensively discussed the flood inundation processes on the ground surface as well as in the buildings and underground spaces,under different rainfall scenarios with the return period ranging from 2 to 200 years.Based on the high spatial-temporal hydrodynamic simulations,the flood damage degrees were evaluated for the buildings and underground spaces with different industry types.The results indicated that the inundation of buildings and underground spaces in densely built cities cannot be neglected in urban flood modeling.Buildings with public service attributes can have a higher flood damage degree,as compared with other types of buildings and underground spaces.
基金Project supported by the National Natural Scinece Foundation of China(Grant Nos.11671219,11871446,12071304,and 12071451).
文摘Within the(2+1)-dimensional Korteweg–de Vries equation framework,new bilinear B¨acklund transformation and Lax pair are presented based on the binary Bell polynomials and gauge transformation.By introducing an arbitrary functionφ(y),a family of deformed soliton and deformed breather solutions are presented with the improved Hirota’s bilinear method.By choosing the appropriate parameters,their interesting dynamic behaviors are shown in three-dimensional plots.Furthermore,novel rational solutions are generated by taking the limit of the obtained solitons.Additionally,twodimensional(2D)rogue waves(localized in both space and time)on the soliton plane are presented,we refer to them as deformed 2D rogue waves.The obtained deformed 2D rogue waves can be viewed as a 2D analog of the Peregrine soliton on soliton plane,and its evolution process is analyzed in detail.The deformed 2D rogue wave solutions are constructed successfully,which are closely related to the arbitrary functionφ(y).This new idea is also applicable to other nonlinear systems.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.XJS200503)the Post-Doctoral Research Project of Shaanxi Province,China。
文摘Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI_(3),Cr_(2) Ge_(2) Te_(6),and Fe_(3)GeTe_(2) opens up a new chapter in the remarkable field of two-dimensional materials.Here,we report on a theoretical analysis of the stability of ferromagnetism in Fe_(3)GeTe_(2).We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of Fe_(3)GeTe_(2).Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems.The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.
基金financially supporrted by the National Key Research and Development Program of China(Grant No.2017YFC1404200)the National Natural Science Foundation of China(Grant Nos.51779150 and 51979040)
文摘In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method and targeted long narrow reaches of the river networks, while the 2D model targeted broad channels and embayment and solved the 2D shallow-water equations using a semi-implicit scheme applied to an unstructured grid of triangular cells. The 1D and 2D models were solved simultaneously by building a matrix for the free surface elevation at every 1D junction and 2D cell center. Velocities were then computed explicitly based on the results at the previous time step and the updated water level. The originality of the scheme arose from a novel coupling method. The results showed that the coupled 1D/2D model produced identical results as the full 2D model in classical to benchmark problems with considerable savings in computational effort. Application of the model to the Pearl River Estuary in southern China showed that complex patterns of tidal wave propagation could be efficiently modeled.
基金funding support from the Singapore MOE Ac RF 308 Tier 2(Grant No.T2EP50220-0026)funding support from Shandong Provincial Natural Science Foundation(Grant No.ZR2023QA012)+3 种基金the Special Fund-ing in the Project of Qilu Young Scholar Program of Shandong Universityfunding support from Australian Research Council Future Fellowship(Grant No.FT220100290)funding support from the AINSE postgraduate awardfunding support from the Research and Development Administration Office at the University of Macao(Grants Nos.MYRG2022-00088-IAPME and SRG2021-00003-IAPME)。
文摘Layered magnetic materials,such as MnBi_(2)Te_(4),have drawn much attention owing to their potential for realizing twodimensional(2D)magnetism and possible topological states.Recently,FeBi_(2)Te_(4),which is isostructural to MnBi_(2)Te_(4),has been synthesized in experiments,but its detailed magnetic ordering and band topology have not been clearly understood yet.Here,based on first-principles calculations,we investigate the magnetic and electronic properties of FeBi_(2)Te_(4)in bulk and 2D forms.We show that different from MnBi_(2)Te_(4),the magnetic ground states of bulk,single-layer,and bilayer FeBi_(2)Te_(4)all favor a 120°noncollinear antiferromagnetic ordering,and they are topologically trivial narrow-gap semiconductors.For the bilayer case,we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state,which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling.Our work clarifies the physical properties of the new material system of FeBi_(2)Te_(4)and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.
文摘This paper points out that a successful numerical simulation is to construct a correct conceptional model which is very dose to the natural condition. A new model, two dimensional coupled three dimensional model (2D -3D ) is presented in the Present paper,which is the most suitable one for the dual - structured - aquifer system. An example of Wenyinghu area is shown.By using the 2D-3D model, a satisfied result of the simulated area is achieved.
基金the Chinese Scholarship Council (No. 201706370022) for the financial support to the joint Ph.D. programme at the University of Wollongong,Australia
文摘To investigate the bedding influence on coal mechanical behaviour in underground environments such as coal or rock burst, simulations of dynamic SHPB tests of pre-stressed coal specimens with different bedding angles were carried out using a particle flow code 2-dimensional(PFC2D). Three impact velocities of 4, 8 and 12 m/s were selected to study dynamic behaviours of coal containing bedding planes under different dynamic loads. The simulation results showed that the existence of bedding planes leads to the degradation of the mechanical properties and their weakening effect significantly depends on the angle h between the bedding planes and load direction. With h increaseing from 0° to 90°, the strength first decreased and subsequently increased and specimens became most vulnerable when h was 30° or 45°.Five failure modes were observed in the specimens in the context of macro-cracks. Furthermore, energy characteristics combined with ultimate failure patterns revealed that maximum accumulated energy and failure intensity have a positive relation with the strength of specimen. When bedding planes were parallel or perpendicular to loading direction, specimens absorbed more energy and experienced more violent failure with increased number of cracks. In contrast, bedding planes with h of 30° or 45° reduced the specimens' ability of storing strain energy to the lowest with fewer cracks observed after failure.
基金the National Natural Science Foundation of China(Nos.12072166 and 11862021)the Program for Science and Technology of Inner Mongolia Autonomous Region of China(No.2021GG0254)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2020MS01006)。
文摘A mathematical model for nonlocal vibration and buckling of embedded two-dimensional(2 D) decagonal quasicrystal(QC) layered nanoplates is proposed. The Pasternak-type foundation is used to simulate the interaction between the nanoplates and the elastic medium. The exact solutions of the nonlocal vibration frequency and buckling critical load of the 2 D decagonal QC layered nanoplates are obtained by solving the eigensystem and using the propagator matrix method. The present three-dimensional(3 D) exact solution can predict correctly the nature frequencies and critical loads of the nanoplates as compared with previous thin-plate and medium-thick-plate theories.Numerical examples are provided to display the effects of the quasiperiodic direction,length-to-width ratio, thickness of the nanoplates, nonlocal parameter, stacking sequence,and medium elasticity on the vibration frequency and critical buckling load of the 2 D decagonal QC nanoplates. The results show that the effects of the quasiperiodic direction on the vibration frequency and critical buckling load depend on the length-to-width ratio of the nanoplates. The thickness of the nanoplate and the elasticity of the surrounding medium can be adjusted for optimal frequency and critical buckling load of the nanoplate.This feature is useful since the frequency and critical buckling load of the 2 D decagonal QCs as coating materials of plate structures can now be tuned as one desire.
基金supported by the National Basic Research Program of China (Grant No. 2013CBA01600)the National Natural Science Foundation of China (Grant Nos. 61261160499 and 11274154)+2 种基金the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011ZX02707)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2012302)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120091110028)
文摘Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.
基金supported by the European Research Council(ERC Starting Grant No.2D-Pnicto Chem 804110)the Spanish MICINN(PID2019-111742GA-I00 and Unit of Excellence“María de Maeztu”CEX2019-000919-M)+2 种基金the Deutsche Forschungsgemeinschaft DFG(FLAG-ERA AB694/2-1)the Generalitat Valenciana(CIDEGENT/2018/001 and i Di FEDER/2018/061 co-financed by FEDER)CONICET for financial support and CNEA Computing Clusters for computer time(density functional theory calculations).
文摘Research on two-dimensional(2D)materials is one of the most active fields in materials science and nanotechnology.Among the members of the 2D family,layered hydroxides(LHs)represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will.Nowadays,LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion,hybrid materials or magnetism.α-Co hydroxides(Simonkolleite-like structures)are promising phases with tuneable electronic and magnetic properties by ligand modification.However,even in the simple case ofα-Co^(Ⅱ)hydroxychlorides,the preparation of well-defined large 2D crystals is not straightforward,hindering the development of fundamental studies.Herein,we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter>5μm and thickness of 20±7 nm)by a simple homogeneous synthesis taking place at room temperature.In structural terms,no differences are observed between our layered materials and those obtained hydrothermally.However,dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices,which have been rationalized with structural DFT calculations.This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based onα-CoIIhydroxides,paving the way for the development of fundamental studies and applications.
基金Project supported by the Republic of Moldova through the projects 15.817.02.29F and 17.80013.16.02.04/Ua
文摘We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride, molybdenum disulfide, and black phosphorus. Different possibilities of phonon engineering for optimization of electrical and heat conductions are discussed. The role of the phonon energy spectra modification on the thermal conductivity in semiconductor nanostructures is revealed. The dependence of thermal conductivity in graphene and related two-dimensional（2 D） materials on temperature, flake size, defect concentration, edge roughness, and strain is analyzed.
基金financially supported by the National Natural Science Foundation of China(No.21604046)the National Young Thousand Talents Program,Shandong Provincial Natural Science Foundation,China(No.ZR2016XJ004)
文摘Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.
基金the National Natural Science Foundation of China (Nos. 11572289,1171407,11702252,and 11902293)the China Postdoctoral Science Foundation (No. 2019M652563)。
文摘The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.
基金Project supported by Beijing Natural Science Foundation,China(Grant No.JQ18014)the National Natural Science Foundation of China(Grant No.12074371)Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000),and CAS Interdisciplinary Innovation Team.
文摘Ultrathin van der Waals(vdW)magnets provide a possibility to access magnetic ordering in the two-dimensional(2D)limit,which are expected to be applied in the spintronic devices.Raman spectroscopy is a powerful characterization method to investigate the spin-related properties in 2D vdW magnets,including magnon and spin–lattice interaction,which are hardly accessible by other optical methods.In this paper,the recent progress of various magnetic properties in 2D vdW magnets studied by Raman spectroscopy is reviewed,including the magnetic transition,spin-wave,spin–lattice interaction,symmetry tuning induced by spin ordering,and nonreciprocal magneto-phonon Raman scattering.
基金Project supported by the National Natural Science Foundation of China(Nos.11371240 and11771274)
文摘The two-dimensional(2D) pseudo-steady isothermal flow, which is isentropic and irrotational, around a convex corner is studied. The self-similar solutions for the supersonic flow around the convex corner are constructed, where the properties of the centered simple wave are used for the 2D isentropic irrotational pseudo-steady Euler equations. The geometric procedures of the center simple waves are given. It is proven that the supersonic flow turns the convex corner by an incomplete centered expansion wave or an incomplete centered compression wave, depending on the conditions of the downstream state.
