Three dimensionally ordered macroporous （3DOM） Ce-based catalysts were successfully prepared via a surfactant-assisted colloidal crystal template （CCT） route. The as-synthesized catalysts showed well- ordered stru...Three dimensionally ordered macroporous （3DOM） Ce-based catalysts were successfully prepared via a surfactant-assisted colloidal crystal template （CCT） route. The as-synthesized catalysts showed well- ordered structures with macropores and small interconnected pore windows. The Raman results indi- cate that the catalyst persists pure fluorite cubic phases until the molar ratio of Mn exceeds O.3, therefore MnOx particles form and impede the contact of the active site and the reagent and restraining soot combustion. The doping of Nd into MnOx-CeO2 enhances the catalytic activity because of increased oxygen vacancy, Mn4- content and stronger redox ability. Nd-doping also improves thermal stability of the catalyst due to less sintering and none phase separation after thermal aging. The flesh and aged Mno.3Ceo.6Ndo.lO2 catalysts show the maximum oxidation rate for soot at 331 and 355 ℃in the O2/N2 atmosphere, achieving a nearly 100% CO2 selectivity.展开更多
A (2 + 1) dimensional KdV-mKdV equation is proposed and integrability in the sense of Painlevé and some exact solutions are discussed. The B?cklund transformation and bilinear equations are obtained through Painl...A (2 + 1) dimensional KdV-mKdV equation is proposed and integrability in the sense of Painlevé and some exact solutions are discussed. The B?cklund transformation and bilinear equations are obtained through Painlevé analysis. Some exact solutions are deduced by Hirota method and generalized Wronskian method.展开更多
The well-developed particle-swarm optimization method together with density functional theory calculations were employed to search lowest-energy geometric structures of two-dimensional(2D)SiGeP_(2).Two newly found str...The well-developed particle-swarm optimization method together with density functional theory calculations were employed to search lowest-energy geometric structures of two-dimensional(2D)SiGeP_(2).Two newly found structures(P3m1 and Pmm2)are predicted.The unbiased global search reveals that the two lowest-energy structures are honeycomb lattices with robust dynamical stabilities.A more accurate Heyd-Scuseria-Ernzerhof(HSE06)hybrid functional is used to estimate the band structures of SiGeP_(2),which indicates that both the structures are semiconductors with indirect band-gap energies 1.80 e V for P3m1 and1.93 e V for Pmm^(2),respectively.Using the deformation potential theory,the P3m1-SiGeP_(2)is predicted to have high electron mobilities(6.4×10^(4)along zigzag direction and 2.9×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively)and hole electron mobilities(1.0×10^(3)along zigzag direction and 2.5×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively),which can be comparable with that of phosphorene and show anisotropic character in-plane.In addition,to estimate the elastic limit of SiGeP_(2),we also calculated the surface tension of SiGeP_(2)as a function of tensile strain.Our results show that the 2D SiGeP_(2)may be good candidaticates for applications in nanoelectronic devices.展开更多
We study the symmetries of a （2＋1）-dimensional generalized Broer-Kaup system by means of the classical Lie group theory. The corresponding group algebra is constructed. Based on the symmetries, severaJ types of sim...We study the symmetries of a （2＋1）-dimensional generalized Broer-Kaup system by means of the classical Lie group theory. The corresponding group algebra is constructed. Based on the symmetries, severaJ types of similarity solutions are obtained.展开更多
This paper investigates a real version of a (2 + 1) dimensional nonlinear Schr?dinger equation through adoption of Painlevé test by means of which the (2 + 1) dimensional nonlinear Schr?dinger equation is studied...This paper investigates a real version of a (2 + 1) dimensional nonlinear Schr?dinger equation through adoption of Painlevé test by means of which the (2 + 1) dimensional nonlinear Schr?dinger equation is studied according to the Weiss et al. method and Kruskal’s simplification algorithms. According to Painlevé test, it is found that the number of arbitrary functions required for explaining the Cauchy-Kovalevskaya theorem exist. Finally, the associated B?cklund transformation and bilinear form is directly obtained from the Painlevé test.展开更多
An event-triggered scheme is proposed to solve the problems of robust guaranteed cost control for a class of two-dimensional(2-D)discrete-time systems.Firstly,an eventtriggered scheme is proposed for 2-D discrete-time...An event-triggered scheme is proposed to solve the problems of robust guaranteed cost control for a class of two-dimensional(2-D)discrete-time systems.Firstly,an eventtriggered scheme is proposed for 2-D discrete-time systems with parameter uncertainties and sector nonlinearities.Then,according to the Lyapunov functional method,the sufficient conditions for the existence of event-triggered robust guaranteed cost controller for 2-D discrete-time systems with parameter uncertainties and sector nonlinearities are given.Furthermore,based on the sufficient conditions and the linear matrix inequality(LMI)technique,the problem of designing event-triggered robust guaranteed cost controller is transformed into a feasible solution problem of LMI.Finally,a numerical example is given to demonstrate that,under the proposed event-triggered robust guaranteed cost control,the closed-loop system is asymptotically stable and fewer communication resources are occupied.展开更多
Graphite‐like carbon nitride(g‐C3N4)‐based compounds have attracted considerable attention because of their excellent photocatalytic performance.In this work,a novel direct Z‐scheme system constructed from two‐di...Graphite‐like carbon nitride(g‐C3N4)‐based compounds have attracted considerable attention because of their excellent photocatalytic performance.In this work,a novel direct Z‐scheme system constructed from two‐dimensional(2D)g‐C3N4nanoplates and zero‐dimensional(0D)MoS2quantum dots(QDs)was prepared through the combination of a hydrothermal process and microemulsion preparation.The morphologies,structures,and optical properties of the as‐prepared photocatalysts were characterized by X‐ray diffraction,X‐ray photoelectron spectroscopy,atomic force microscopy,transmission electron microscopy,and UV‐vis diffuse reflectance spectroscopy.In addition,the photocatalytic performances of the prepared2D/0D hybrid composites were evaluated based on the photodegradation of rhodamine B under visible‐light irradiation.The results demonstrated that the introduction of MoS2QDs to g‐C3N4greatly enhanced the photocatalytic efficiency.For the optimum7%MoS2QD/g‐C3N4photocatalyst,the degradation rate constant was8.8times greater than that of pure g‐C3N4under visible‐light irradiation.Photocurrent and electrochemical impedance spectroscopy results further demonstrated that the MoS2QD/g‐C3N4composites exhibited higher photocurrent density and lower chargetransfer resistance than those of the pure g‐C3N4or MoS2QDs.Active species trapping,terephthalic acid photoluminescence,and nitro blue tetrazolium transformation experiments were performed to investigate the evolution of reactive oxygen species,including hydroxyl radicals and superoxide radicals.The possible enhanced photocatalytic mechanism was attributed to a direct Z‐scheme system,which not only can increase the separation efficiency of photogenerated electron‐hole pairs but also possesses excellent oxidation and reduction ability for high photocatalytic performances.This work provides an effective synthesis approach and insight to help develop other C3N4‐based direct Z‐scheme photocatalytic systems for environmental purification and energy conversion.展开更多
An accurate and efficient Synthetic Aperture Radar(SAR)raw data generator is of considerable value for testing system parameters and verifying imaging algorithms.Nevertheless,the existing simulator cannot exactly hand...An accurate and efficient Synthetic Aperture Radar(SAR)raw data generator is of considerable value for testing system parameters and verifying imaging algorithms.Nevertheless,the existing simulator cannot exactly handle the case of the fast moving targets in high squint geometry.As for the issue,the analytical expression for the two Dimensional(2-D)signal spectrum of moving targets is derived and a fast raw echo simulation method is proposed in this study.The proposed simulator can accommodate the moving targets in the high squint geometry,whose processing steps of the simulation are given in detail and its computational complexity is analyzed.The simulation data for static and moving targets are processed and analyzed,and the results are given to validate the effectiveness of the proposed approach.展开更多
Two-dimensional(2D)layered photocatalysts coupled with 2D Ti_(3)C_(2)T_(x)(T=OH,O,or F)MXene cocatalysts in 2D/2D configuration have been extensively studied for use in artificial photosynthesis.Unfortunately,the over...Two-dimensional(2D)layered photocatalysts coupled with 2D Ti_(3)C_(2)T_(x)(T=OH,O,or F)MXene cocatalysts in 2D/2D configuration have been extensively studied for use in artificial photosynthesis.Unfortunately,the overall photoreaction efficiency of these cocatalysts is often limited by weak 2D/2D interfacial van der Waals interactions,high interfacial electrostatic barriers,and slow interfacial charge transfer.In this study,1D crystalline g-C_(3)N_(4)(CCN)nanorods are grown along the c-axis using the molten-salt method and assembled onto a 2D Ti_(3)C_(2)T_(x)substrate by freeze-drying-assisted interfacial coupling,forming a unique Schottky junction photocatalyst in a 1D/2D configuration with interfacial hydrogen bonds.Transfer of photoelectrons in the CCN nanorods could along the radialπ-conjugated plane to the hydrogen-bonded 2D Ti_(3)C_(2)T_(x)in the 1D/2D configuration is more efficient than the slow interlayer charge transfer in catalysts with a conventional 2D/2D configuration.Consequently,the optimized 1D-CCN/2D-Ti_(3)C_(2)T_(x)hybrid photocatalyst assembled by freeze-drying(TC/CCN-FD)exhibited an outstanding photocatalytic CO_(2)reduction activity at a rate of 2.13μmol g^(-1)h^(-1),being 5.6 and 8.9 times more efficient than the pristine 1D CCN and 2D bulk g-C_(3)N_(4)counterparts,respectively.Moreover,the selectivity towards the multielectron reduction product(CH_(4))was significantly enhanced over TC/CCN-FD owing to the faster interfacial charge transfer across the CCN/Ti_(3)C_(2)T_(x)interface and the higher density of photoelectrons on the Ti_(3)C_(2)T_(x)cocatalysts.This work will inspire further studies on suppressing the interfacial charge transfer barrier by matching the interfacial crystal orientation and strengthening the interfacial interactions.展开更多
To attain a circular carbon economy and resolve CO_(2) electroreduction technology obstacles,single‐atom catalysts(SACs)have emerged as a logical option for electrocatalysis because of their extraordinary catalytic a...To attain a circular carbon economy and resolve CO_(2) electroreduction technology obstacles,single‐atom catalysts(SACs)have emerged as a logical option for electrocatalysis because of their extraordinary catalytic activity.Among SACs,metal–organic frameworks(MOFs)have been recognized as promising support materials because of their exceptional ability to prevent metal aggregation.This study shows that atomically dispersed Ni single atoms on a precisely engineered MOF nanosheet display a high Faradaic efficiency of approximately 100% for CO formation in H‐cell and three‐compartment microfluidic flow‐cell reactors and an excellent turnover frequency of 23,699 h^(−1),validating their intrinsic catalytic potential.These results suggest that crystallographic variations affect the abundant vacancy sites on the MOF nanosheets,which are linked to the evaporation of Zn‐containing organic linkers during pyrolysis.Furthermore,using X‐ray absorption spectroscopy and density functional theory calculations,a comprehensive investigation of the unsaturated atomic coordination environments and the underlying mechanism involving CO^(*) preadsorbed sites as initial states was possible and provided valuable insights.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
Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained...Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For comparison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives.展开更多
In this paper, infinitesimal deformations of time-like surfaces are investigated in Minkowski 3-space R2,1. It is shown that some given deformations of the time-like surface can be described by 2+1 dimensional integra...In this paper, infinitesimal deformations of time-like surfaces are investigated in Minkowski 3-space R2,1. It is shown that some given deformations of the time-like surface can be described by 2+1 dimensional integrable systems. Moreover spectral parameters are introduced, and it is proved that deformation families are soliton surfaces’ families.展开更多
In this paper,we study the homotopy classification of continuous maps between two r-1 connected 2r dimensional topological manifolds M,N.If we assume some knowledge on the homotopy groups of spheres,then the complete ...In this paper,we study the homotopy classification of continuous maps between two r-1 connected 2r dimensional topological manifolds M,N.If we assume some knowledge on the homotopy groups of spheres,then the complete classification can be obtained from the homotopy invariants of M,N.We design an algorithm and compose a program to give explicit computations.展开更多
Although mechanical vibration is extremely complicated, each fault signal produced by it has its own inherent features, The distinction may be most prominent between the certain components hidden in those features and...Although mechanical vibration is extremely complicated, each fault signal produced by it has its own inherent features, The distinction may be most prominent between the certain components hidden in those features and the same components of normal signals. Three-order cumulant can reduce the Gaussian background noise automatically and its complex formal includes different coupling information of its signal. In the experiment, through these different coupling modes, the same coupling components are fetched from specific fault signal and normal signal, then these components are used to diagnose that certain fault. The results show that the method can fetch the most prominent distinction between normal signal and the specific fault signal, so the specific fault diagnosis by this method is satisfactory.展开更多
Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered...Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered the related practical applications.Here,we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe2 down to the ultra-thin limit.It thus makes CrTe2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature.An in-plane room-temperature negative anisotropic magnetoresistance(AMR)was obtained in ultra-thin CrTe2 devices,with a sign change in the AMR at lower temperature,with−0.6%and+5%at 300 and 10 K,respectively.Our findings provide insights into magnetism in ultra-thin CrTe2,expanding the vdW crystals toolbox for future room-temperature spintronic applications.展开更多
Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity ...Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence （at room temperature and 10 K） is assessed on mechanically exfoliated WSe2 monolayer flakes encapsulated with SiOx and AlxOy layers by means of chemical and physical deposition techniques. Conformal coating on untreated and non- functionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion （charged exciton） photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.展开更多
Particles of aerodynamic diameter〈2.5 pm （PM/.5） caused extremely severe and persistent haze pollution is of concern in many cities. In this study, samples of PM2.5 were collected from atmosphere environment of Bei...Particles of aerodynamic diameter〈2.5 pm （PM/.5） caused extremely severe and persistent haze pollution is of concern in many cities. In this study, samples of PM2.5 were collected from atmosphere environment of Beijing and Shanxi Province, and analyzed using terahertz （THz） radiation. The transmission spectrum of PM2.5 in Shanxi Province had two distinct absorption peaks at 6.0 and 6.7 THz, and the curve was increasing on the whole. However, the transmission spectrum of PMa.5 in Beijing had obviously different variation tendency and the absorption peak was studied by monitoring PM2.5 masses in conjunction with two-dimensional correlation spectro- scopy （2DCOS）. By comparing the pollutant species and concentrations of Shanxi Province and Beijing over the time of collecting samples, the concentrations of sulfate and ammonium were similar, which contributed to emerge absorption bands in the same position. While the concentrations of organic matter （OM）, nitrate, chloride and elemental carbon （EC） were different. Furthermore, dust and some other inorganic ion are unique to Shanxi province, which lead to different variation tendency of the transmission spectrum of PM2.5. These results will be of importance for environmental monitoring and for control- ling PM emissions. According to this research, optical techniques, and especially spectral methods, should be considered for PM2.5 monitoring.展开更多
In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic stru...In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.展开更多
Additive manufacturing(AM)has shown promise in designing 3D scaffold for regenerative medicine.However,many synthetic biomaterials used for AM are bioinert.Here,we report synthesis of bioactive nanocomposites from a p...Additive manufacturing(AM)has shown promise in designing 3D scaffold for regenerative medicine.However,many synthetic biomaterials used for AM are bioinert.Here,we report synthesis of bioactive nanocomposites from a poly(ethylene oxide terephthalate)(PEOT)/poly(butylene terephthalate)(PBT)(PEOT/PBT)copolymer and 2D nanosilicates for fabricating 3D scaffolds for bone tissue engineering.PEOT/PBT have been shown to support calcification and bone bonding ability in vivo,while 2D nanosilicates induce osteogenic differentiation of human mesenchymal stem cells(hMSCs)in absence of osteoinductive agents.The effect of nanosilicates addition to PEOT/PBT on structural,mechanical and biological properties is investigated.Specifically,the addition of nanosilicate to PEOT/PBT improves the stability of nanocomposites in physiological conditions,as nanosilicate suppressed the degradation rate of copolymer.However,no significant increase in the mechanical stiffness of scaffold due to the addition of nanosilicates is observed.The addition of nanosilicates to PEOT/PBT improves the bioactive properties of AM nanocomposites as demonstrated in vitro.hMSCs readily proliferated on the scaffolds containing nanosilicates and resulted in significant upregulation of osteo-related proteins and production of mineralized matrix.The synergistic ability of nanosilicates and PEOT/PBT can be utilized for designing bioactive scaffolds for bone tissue engineering.展开更多
基金Project supported by the National Natural Science Foundation of China(21006130,51274261)
文摘Three dimensionally ordered macroporous （3DOM） Ce-based catalysts were successfully prepared via a surfactant-assisted colloidal crystal template （CCT） route. The as-synthesized catalysts showed well- ordered structures with macropores and small interconnected pore windows. The Raman results indi- cate that the catalyst persists pure fluorite cubic phases until the molar ratio of Mn exceeds O.3, therefore MnOx particles form and impede the contact of the active site and the reagent and restraining soot combustion. The doping of Nd into MnOx-CeO2 enhances the catalytic activity because of increased oxygen vacancy, Mn4- content and stronger redox ability. Nd-doping also improves thermal stability of the catalyst due to less sintering and none phase separation after thermal aging. The flesh and aged Mno.3Ceo.6Ndo.lO2 catalysts show the maximum oxidation rate for soot at 331 and 355 ℃in the O2/N2 atmosphere, achieving a nearly 100% CO2 selectivity.
基金supported by Chinese National Social Science Foundation(Grant Number:CNSSF:13CJY037)Research on the indemnificatory Apartment Construction Based on Residential Integration.
文摘A (2 + 1) dimensional KdV-mKdV equation is proposed and integrability in the sense of Painlevé and some exact solutions are discussed. The B?cklund transformation and bilinear equations are obtained through Painlevé analysis. Some exact solutions are deduced by Hirota method and generalized Wronskian method.
基金Funded by Henan Joint Funds of the National Natural Science Foundation of China(No.U1904179)the National Natural Science Foundation of China(No.51501093)the Key Scientific and Technological Project of Technology Department of Henan Province of China(No.212102210448)。
文摘The well-developed particle-swarm optimization method together with density functional theory calculations were employed to search lowest-energy geometric structures of two-dimensional(2D)SiGeP_(2).Two newly found structures(P3m1 and Pmm2)are predicted.The unbiased global search reveals that the two lowest-energy structures are honeycomb lattices with robust dynamical stabilities.A more accurate Heyd-Scuseria-Ernzerhof(HSE06)hybrid functional is used to estimate the band structures of SiGeP_(2),which indicates that both the structures are semiconductors with indirect band-gap energies 1.80 e V for P3m1 and1.93 e V for Pmm^(2),respectively.Using the deformation potential theory,the P3m1-SiGeP_(2)is predicted to have high electron mobilities(6.4×10^(4)along zigzag direction and 2.9×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively)and hole electron mobilities(1.0×10^(3)along zigzag direction and 2.5×10^(3)cm^(2)·V^(-1)·s^(-1)along armchair direction,respectively),which can be comparable with that of phosphorene and show anisotropic character in-plane.In addition,to estimate the elastic limit of SiGeP_(2),we also calculated the surface tension of SiGeP_(2)as a function of tensile strain.Our results show that the 2D SiGeP_(2)may be good candidaticates for applications in nanoelectronic devices.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10475055 and 10547124 and partly by Shanghai Leading Academic Discipline Project under Grant No. T0401.Acknowledgments The authors would like to thank Prof. S.Y. Lou for his helpful discussions.
文摘We study the symmetries of a （2＋1）-dimensional generalized Broer-Kaup system by means of the classical Lie group theory. The corresponding group algebra is constructed. Based on the symmetries, severaJ types of similarity solutions are obtained.
基金supported by the National Natural Science Foundation of China(grant No.11371361)the Innovation Team of Jiangsu Province hosted by China University of Mining and Technology(2014)the Key Discipline Construction by China University of Mining and Technology(Grant No.XZD 201602).
文摘This paper investigates a real version of a (2 + 1) dimensional nonlinear Schr?dinger equation through adoption of Painlevé test by means of which the (2 + 1) dimensional nonlinear Schr?dinger equation is studied according to the Weiss et al. method and Kruskal’s simplification algorithms. According to Painlevé test, it is found that the number of arbitrary functions required for explaining the Cauchy-Kovalevskaya theorem exist. Finally, the associated B?cklund transformation and bilinear form is directly obtained from the Painlevé test.
基金supported by the National Natural Science Foundation of China(61573129 U1804147)+2 种基金the Innovative Scientists and Technicians Team of Henan Provincial High Education(20IRTSTHN019)the Innovative Scientists and Technicians Team of Henan Polytechnic University(T2019-2 T2017-1)
文摘An event-triggered scheme is proposed to solve the problems of robust guaranteed cost control for a class of two-dimensional(2-D)discrete-time systems.Firstly,an eventtriggered scheme is proposed for 2-D discrete-time systems with parameter uncertainties and sector nonlinearities.Then,according to the Lyapunov functional method,the sufficient conditions for the existence of event-triggered robust guaranteed cost controller for 2-D discrete-time systems with parameter uncertainties and sector nonlinearities are given.Furthermore,based on the sufficient conditions and the linear matrix inequality(LMI)technique,the problem of designing event-triggered robust guaranteed cost controller is transformed into a feasible solution problem of LMI.Finally,a numerical example is given to demonstrate that,under the proposed event-triggered robust guaranteed cost control,the closed-loop system is asymptotically stable and fewer communication resources are occupied.
基金supported by National Natural Science Foundation of China(51672113)Six Talent Peaks Project in Jiangsu Province(2015-XCL-026)+3 种基金Natural Science Foundation of Jiangsu Province(BK20171299)State Key Laboratory of Photocatalysis on Energy and Environment(SKLPEE-KF201705),Fuzhou UniversityState Key Laboratory of Advanced Technology for Materials Synthesis and Processing(2016-KF-10),Wuhan University of Technologythe Qing Lan Project Foundation of Jiangsu Province~~
文摘Graphite‐like carbon nitride(g‐C3N4)‐based compounds have attracted considerable attention because of their excellent photocatalytic performance.In this work,a novel direct Z‐scheme system constructed from two‐dimensional(2D)g‐C3N4nanoplates and zero‐dimensional(0D)MoS2quantum dots(QDs)was prepared through the combination of a hydrothermal process and microemulsion preparation.The morphologies,structures,and optical properties of the as‐prepared photocatalysts were characterized by X‐ray diffraction,X‐ray photoelectron spectroscopy,atomic force microscopy,transmission electron microscopy,and UV‐vis diffuse reflectance spectroscopy.In addition,the photocatalytic performances of the prepared2D/0D hybrid composites were evaluated based on the photodegradation of rhodamine B under visible‐light irradiation.The results demonstrated that the introduction of MoS2QDs to g‐C3N4greatly enhanced the photocatalytic efficiency.For the optimum7%MoS2QD/g‐C3N4photocatalyst,the degradation rate constant was8.8times greater than that of pure g‐C3N4under visible‐light irradiation.Photocurrent and electrochemical impedance spectroscopy results further demonstrated that the MoS2QD/g‐C3N4composites exhibited higher photocurrent density and lower chargetransfer resistance than those of the pure g‐C3N4or MoS2QDs.Active species trapping,terephthalic acid photoluminescence,and nitro blue tetrazolium transformation experiments were performed to investigate the evolution of reactive oxygen species,including hydroxyl radicals and superoxide radicals.The possible enhanced photocatalytic mechanism was attributed to a direct Z‐scheme system,which not only can increase the separation efficiency of photogenerated electron‐hole pairs but also possesses excellent oxidation and reduction ability for high photocatalytic performances.This work provides an effective synthesis approach and insight to help develop other C3N4‐based direct Z‐scheme photocatalytic systems for environmental purification and energy conversion.
文摘An accurate and efficient Synthetic Aperture Radar(SAR)raw data generator is of considerable value for testing system parameters and verifying imaging algorithms.Nevertheless,the existing simulator cannot exactly handle the case of the fast moving targets in high squint geometry.As for the issue,the analytical expression for the two Dimensional(2-D)signal spectrum of moving targets is derived and a fast raw echo simulation method is proposed in this study.The proposed simulator can accommodate the moving targets in the high squint geometry,whose processing steps of the simulation are given in detail and its computational complexity is analyzed.The simulation data for static and moving targets are processed and analyzed,and the results are given to validate the effectiveness of the proposed approach.
文摘Two-dimensional(2D)layered photocatalysts coupled with 2D Ti_(3)C_(2)T_(x)(T=OH,O,or F)MXene cocatalysts in 2D/2D configuration have been extensively studied for use in artificial photosynthesis.Unfortunately,the overall photoreaction efficiency of these cocatalysts is often limited by weak 2D/2D interfacial van der Waals interactions,high interfacial electrostatic barriers,and slow interfacial charge transfer.In this study,1D crystalline g-C_(3)N_(4)(CCN)nanorods are grown along the c-axis using the molten-salt method and assembled onto a 2D Ti_(3)C_(2)T_(x)substrate by freeze-drying-assisted interfacial coupling,forming a unique Schottky junction photocatalyst in a 1D/2D configuration with interfacial hydrogen bonds.Transfer of photoelectrons in the CCN nanorods could along the radialπ-conjugated plane to the hydrogen-bonded 2D Ti_(3)C_(2)T_(x)in the 1D/2D configuration is more efficient than the slow interlayer charge transfer in catalysts with a conventional 2D/2D configuration.Consequently,the optimized 1D-CCN/2D-Ti_(3)C_(2)T_(x)hybrid photocatalyst assembled by freeze-drying(TC/CCN-FD)exhibited an outstanding photocatalytic CO_(2)reduction activity at a rate of 2.13μmol g^(-1)h^(-1),being 5.6 and 8.9 times more efficient than the pristine 1D CCN and 2D bulk g-C_(3)N_(4)counterparts,respectively.Moreover,the selectivity towards the multielectron reduction product(CH_(4))was significantly enhanced over TC/CCN-FD owing to the faster interfacial charge transfer across the CCN/Ti_(3)C_(2)T_(x)interface and the higher density of photoelectrons on the Ti_(3)C_(2)T_(x)cocatalysts.This work will inspire further studies on suppressing the interfacial charge transfer barrier by matching the interfacial crystal orientation and strengthening the interfacial interactions.
基金National Research Foundation of Korea(NRF),Grant/Award Numbers:2021R1A4A3027878,RS‐2023‐00209139,2015M3D3A1A01064929Korea Institute of Energy Technology&Energy(MOTIE)of the Republic of Korea,Grant/Award Number:20212010100040。
文摘To attain a circular carbon economy and resolve CO_(2) electroreduction technology obstacles,single‐atom catalysts(SACs)have emerged as a logical option for electrocatalysis because of their extraordinary catalytic activity.Among SACs,metal–organic frameworks(MOFs)have been recognized as promising support materials because of their exceptional ability to prevent metal aggregation.This study shows that atomically dispersed Ni single atoms on a precisely engineered MOF nanosheet display a high Faradaic efficiency of approximately 100% for CO formation in H‐cell and three‐compartment microfluidic flow‐cell reactors and an excellent turnover frequency of 23,699 h^(−1),validating their intrinsic catalytic potential.These results suggest that crystallographic variations affect the abundant vacancy sites on the MOF nanosheets,which are linked to the evaporation of Zn‐containing organic linkers during pyrolysis.Furthermore,using X‐ray absorption spectroscopy and density functional theory calculations,a comprehensive investigation of the unsaturated atomic coordination environments and the underlying mechanism involving CO^(*) preadsorbed sites as initial states was possible and provided valuable insights.
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 project was supported by Equipment Pre-research Key Laboratory Fund(No.6142020305)The authors would like to thank Shiyanjia Lab(www.shiyanjia.com)for the support of XPS test.
文摘Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For comparison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives.
基金This work was supported by NSFC(10301030) and 973 project, "nonlinear
文摘In this paper, infinitesimal deformations of time-like surfaces are investigated in Minkowski 3-space R2,1. It is shown that some given deformations of the time-like surface can be described by 2+1 dimensional integrable systems. Moreover spectral parameters are introduced, and it is proved that deformation families are soliton surfaces’ families.
基金the National Natural Science Foundation of China(Grant No.10671018)
文摘In this paper,we study the homotopy classification of continuous maps between two r-1 connected 2r dimensional topological manifolds M,N.If we assume some knowledge on the homotopy groups of spheres,then the complete classification can be obtained from the homotopy invariants of M,N.We design an algorithm and compose a program to give explicit computations.
文摘Although mechanical vibration is extremely complicated, each fault signal produced by it has its own inherent features, The distinction may be most prominent between the certain components hidden in those features and the same components of normal signals. Three-order cumulant can reduce the Gaussian background noise automatically and its complex formal includes different coupling information of its signal. In the experiment, through these different coupling modes, the same coupling components are fetched from specific fault signal and normal signal, then these components are used to diagnose that certain fault. The results show that the method can fetch the most prominent distinction between normal signal and the specific fault signal, so the specific fault diagnosis by this method is satisfactory.
基金This work is supported by the National Key R&D Program of China(Nos.2019YFA0307800,2017YFA0206302,and 2017YFA0206200)the National Natural Science Foundation of China(NSFC)(Nos.11974357,U1932151,and 51627801)+4 种基金G.Y.and X.H.thank the financial supports from the National Natural Science Foundation of China(NSFC)(No.11874409)This work is supported by the National Natural Science Foundation of China(NSFC)(Nos.61574060,and 8206300210)T.Y.acknowledges supports from the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation NSFC and CASC,China(No.U1537204)Z.H.acknowledges the support from the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(No.KF201816)The authors appreciate the help of Dr.Binbin Jiang in obtaining the HAADF-STEM images.
文摘Although many emerging new phenomena have been unraveled in two dimensional(2D)materials with long-range spin orderings,the usually low critical temperature in van der Waals(vdW)magnetic material has thus far hindered the related practical applications.Here,we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe2 down to the ultra-thin limit.It thus makes CrTe2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature.An in-plane room-temperature negative anisotropic magnetoresistance(AMR)was obtained in ultra-thin CrTe2 devices,with a sign change in the AMR at lower temperature,with−0.6%and+5%at 300 and 10 K,respectively.Our findings provide insights into magnetism in ultra-thin CrTe2,expanding the vdW crystals toolbox for future room-temperature spintronic applications.
基金The authors would like to thank Georgios Katsaros and Tim Wehling for valuable discussions. Stephan Br~iuer, Albin Schwarz, and Ursula Kainz are ackno- wledged for technical support. A. M. acknowledges the financial support through BES-2013-062593. G. G. acknowledges support from the Austrian Science Fund through project P 28018-B27. I. Z. acknowledges financial support from the Swiss National Science Foundation research grant （No. 200021_165784）. This work was partially funded by the Austrian Science Fund through the projects P24471 and P26830, and by the Spanish Ministry for Economy and Competitiveness trough the project MINECO/FEDER TEC2015-69916- C2-1-R.
文摘Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence （at room temperature and 10 K） is assessed on mechanically exfoliated WSe2 monolayer flakes encapsulated with SiOx and AlxOy layers by means of chemical and physical deposition techniques. Conformal coating on untreated and non- functionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion （charged exciton） photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.
文摘Particles of aerodynamic diameter〈2.5 pm （PM/.5） caused extremely severe and persistent haze pollution is of concern in many cities. In this study, samples of PM2.5 were collected from atmosphere environment of Beijing and Shanxi Province, and analyzed using terahertz （THz） radiation. The transmission spectrum of PM2.5 in Shanxi Province had two distinct absorption peaks at 6.0 and 6.7 THz, and the curve was increasing on the whole. However, the transmission spectrum of PMa.5 in Beijing had obviously different variation tendency and the absorption peak was studied by monitoring PM2.5 masses in conjunction with two-dimensional correlation spectro- scopy （2DCOS）. By comparing the pollutant species and concentrations of Shanxi Province and Beijing over the time of collecting samples, the concentrations of sulfate and ammonium were similar, which contributed to emerge absorption bands in the same position. While the concentrations of organic matter （OM）, nitrate, chloride and elemental carbon （EC） were different. Furthermore, dust and some other inorganic ion are unique to Shanxi province, which lead to different variation tendency of the transmission spectrum of PM2.5. These results will be of importance for environmental monitoring and for control- ling PM emissions. According to this research, optical techniques, and especially spectral methods, should be considered for PM2.5 monitoring.
基金support of the National Natural Science Foundation of China(Grant Nos.51527901,51335005,51475256,and 51605249)
文摘In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.
基金from National Science Foundation(CBET 1705852)National Institute of Health(EB026265,EB023454).A.D.L.and L.M.are grateful to the Dutch Technology Foundation(Grant no.11135).
文摘Additive manufacturing(AM)has shown promise in designing 3D scaffold for regenerative medicine.However,many synthetic biomaterials used for AM are bioinert.Here,we report synthesis of bioactive nanocomposites from a poly(ethylene oxide terephthalate)(PEOT)/poly(butylene terephthalate)(PBT)(PEOT/PBT)copolymer and 2D nanosilicates for fabricating 3D scaffolds for bone tissue engineering.PEOT/PBT have been shown to support calcification and bone bonding ability in vivo,while 2D nanosilicates induce osteogenic differentiation of human mesenchymal stem cells(hMSCs)in absence of osteoinductive agents.The effect of nanosilicates addition to PEOT/PBT on structural,mechanical and biological properties is investigated.Specifically,the addition of nanosilicate to PEOT/PBT improves the stability of nanocomposites in physiological conditions,as nanosilicate suppressed the degradation rate of copolymer.However,no significant increase in the mechanical stiffness of scaffold due to the addition of nanosilicates is observed.The addition of nanosilicates to PEOT/PBT improves the bioactive properties of AM nanocomposites as demonstrated in vitro.hMSCs readily proliferated on the scaffolds containing nanosilicates and resulted in significant upregulation of osteo-related proteins and production of mineralized matrix.The synergistic ability of nanosilicates and PEOT/PBT can be utilized for designing bioactive scaffolds for bone tissue engineering.
