Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of grap...Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of graphene.Here we report for the first time the observation of moire patterns arising from a bilayer graphone/graphene superlattice produced through direct single-sided hydrogenation of a bilayer graphene on substrate.Compared to pristine graphene,the bilayer superlattice exhibits a rippled surface and two types of moire patterns are observed:triangular and linear moire patterns with the periodicities of 11 nm and 8-9 nm,respectively.These moire patterns are revealed from atomic force microscopy and further confirmed by following fast Fourier transform(FFT)analysis.Density functional theory(DFT)calculations are also performed and the optimized lattice constants of bilayer superlattice heterostructure are in line with our experimental analysis.These findings show that well-defined triangular and linear periodic potentials can be introduced into the graphene system through the single-sided hydrogenation and also open a route towards the tailoring of electronic properties of graphene by various moirépotentials.展开更多
In this paper, we discuss the Lipschitz equivalence of self-similar sets with triangular pattern. This is a generalization of {1, 3, 5}-{1, 4, 5} problem proposed by David and Semmes. It is proved that if two such sel...In this paper, we discuss the Lipschitz equivalence of self-similar sets with triangular pattern. This is a generalization of {1, 3, 5}-{1, 4, 5} problem proposed by David and Semmes. It is proved that if two such self-similar sets are totally disconnected, then they are Lipschitz equivalent if and only if they have the same Hausdorff dimension.展开更多
Turing demonstrated that spatially heterogeneous patterns can be self-organized, when the two substances interact locally and diffuse randomly. Turing systems have been applied not only to explain patterns observed wi...Turing demonstrated that spatially heterogeneous patterns can be self-organized, when the two substances interact locally and diffuse randomly. Turing systems have been applied not only to explain patterns observed within the biological and chemical fields, but also to develop image information processing tools. In a twin study, to evaluate the V-shaped bundle of the inner ear outer hair, we developed a method that utilizes a reaction-diffusion system with anisotropic diffusion that exhibited triangular patterns with the introduction of a certain anisotropy strength. In this study, we explored the parameter range over which these periodic triangular patterns were obtained. First, we defined an index for triangular clearness, TC. Triangular patterns can be obtained by introducing a large anisotropy δ, but the range of δ depends on the diffusion coefficient. We found an explanatory variable that can explain the change in TC based on a heuristic argument of the relative distance of the pitchfork bifurcation point between the maximum and minimum anisotropic diffusion function values. Clear periodic triangular patterns were obtained when the distance between the minimum anisotropic function value and pitchfork bifurcation point was over 2.5 times the distance to the anisotropic diffusion function maximum value. By changing the diffusion coefficients or the reaction terms, we further confirmed the accuracy of this condition using computer simulation. Its relevance to diffusion instability has also been discussed.展开更多
The novel approach of this paper describes the suppression of grating lobe level with the element count optimization in planar antenna array. Rectangular lattice (RL) and triangular lattice (TL) structures are chosen ...The novel approach of this paper describes the suppression of grating lobe level with the element count optimization in planar antenna array. Rectangular lattice (RL) and triangular lattice (TL) structures are chosen for determining the achievable array element patterns (EP) and further suppressing the grating lobe level. The element spacing and number of elements (10 × 20 array) are taken into account for particular lattice. Grating lobe peaks are observed for the 200-element planar array at maximum scan angle (θ) with the set frequency of 3 GHz. Further, it is found that 14°;bore sight elevation of rectangular lattice produces a transformed field of view, which permits a reduction in element count of 20.39% compared with 10° bore sight elevation. Finally, the typical values of elevation, element count and array size (25 cm2) are trained using artificial neural network (ANN) algorithm and element count is predicted after testing the network. The network shows a high success rate.展开更多
基金We acknowledge the financial support from the National Natural Science Foundation of China(No.51905306)the China Postdoctoral Science Fund(No.2018M642650)the Special Support for Post-doc Creative Funding of Shandong Province(No.201902005).We are also grateful for the funding support from the University of Manchester Donator Foundation and Swedish Research Council Formas(No.2019-01538).Dr.Chloe Holyord from National Graphene Institute,University of M anchester is gratefully acknowledged for the help with AFM m easurem ents.Dr.Linqing Zhang and Mr.Malachy Mcgowan are greatly acknowledged for the experimental support in the sample preparation.
文摘Moirépatterns from two-dimensional(2D)graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of graphene.Here we report for the first time the observation of moire patterns arising from a bilayer graphone/graphene superlattice produced through direct single-sided hydrogenation of a bilayer graphene on substrate.Compared to pristine graphene,the bilayer superlattice exhibits a rippled surface and two types of moire patterns are observed:triangular and linear moire patterns with the periodicities of 11 nm and 8-9 nm,respectively.These moire patterns are revealed from atomic force microscopy and further confirmed by following fast Fourier transform(FFT)analysis.Density functional theory(DFT)calculations are also performed and the optimized lattice constants of bilayer superlattice heterostructure are in line with our experimental analysis.These findings show that well-defined triangular and linear periodic potentials can be introduced into the graphene system through the single-sided hydrogenation and also open a route towards the tailoring of electronic properties of graphene by various moirépotentials.
基金supported by National Natural Science of China (Grant Nos. 11071224, 11071082, 11071090, 10671180, 10631040)Natural Science Foundation of Ningbo (Grant No. 2009A610077)+1 种基金the Fundamental Research Funds for the Central Universities, SCUTthe Science Foundation for the Youth of South China University of Technology (Grant No. E5090470)
文摘In this paper, we discuss the Lipschitz equivalence of self-similar sets with triangular pattern. This is a generalization of {1, 3, 5}-{1, 4, 5} problem proposed by David and Semmes. It is proved that if two such self-similar sets are totally disconnected, then they are Lipschitz equivalent if and only if they have the same Hausdorff dimension.
文摘Turing demonstrated that spatially heterogeneous patterns can be self-organized, when the two substances interact locally and diffuse randomly. Turing systems have been applied not only to explain patterns observed within the biological and chemical fields, but also to develop image information processing tools. In a twin study, to evaluate the V-shaped bundle of the inner ear outer hair, we developed a method that utilizes a reaction-diffusion system with anisotropic diffusion that exhibited triangular patterns with the introduction of a certain anisotropy strength. In this study, we explored the parameter range over which these periodic triangular patterns were obtained. First, we defined an index for triangular clearness, TC. Triangular patterns can be obtained by introducing a large anisotropy δ, but the range of δ depends on the diffusion coefficient. We found an explanatory variable that can explain the change in TC based on a heuristic argument of the relative distance of the pitchfork bifurcation point between the maximum and minimum anisotropic diffusion function values. Clear periodic triangular patterns were obtained when the distance between the minimum anisotropic function value and pitchfork bifurcation point was over 2.5 times the distance to the anisotropic diffusion function maximum value. By changing the diffusion coefficients or the reaction terms, we further confirmed the accuracy of this condition using computer simulation. Its relevance to diffusion instability has also been discussed.
文摘The novel approach of this paper describes the suppression of grating lobe level with the element count optimization in planar antenna array. Rectangular lattice (RL) and triangular lattice (TL) structures are chosen for determining the achievable array element patterns (EP) and further suppressing the grating lobe level. The element spacing and number of elements (10 × 20 array) are taken into account for particular lattice. Grating lobe peaks are observed for the 200-element planar array at maximum scan angle (θ) with the set frequency of 3 GHz. Further, it is found that 14°;bore sight elevation of rectangular lattice produces a transformed field of view, which permits a reduction in element count of 20.39% compared with 10° bore sight elevation. Finally, the typical values of elevation, element count and array size (25 cm2) are trained using artificial neural network (ANN) algorithm and element count is predicted after testing the network. The network shows a high success rate.
