Anisogrid composite lattice conical shells, which exhibit varying stiffness along their cone generators, are widely used as interstage structures in aerospace applications. Buckling under axial compression represents ...Anisogrid composite lattice conical shells, which exhibit varying stiffness along their cone generators, are widely used as interstage structures in aerospace applications. Buckling under axial compression represents one of the most hazardous failure modes for such structures. In this paper, the smeared stiffness method, which incorporates the effect of component torsion, is used to obtain the equivalent stiffness coefficients for composite lattice conical shells with triangular and hexagonal patterns. A unified framework based on the variational differential quadrature (VDQ) method is established, leveraging its suitability for asymptotic expansion to determine the critical buckling loads and the b-imperfection sensitivity parameter of lattice conical shells with axially varying stiffness due to rib layout. The influence of pre-buckling deformation is taken into account to enhance the accuracy of predictions on the linear buckling loads. The feasibility of the present equivalent continuum model is verified, and the differences in buckling behaviors for composite lattice conical shells with both triangular and hexagonal unit cells are numerically evaluated through the finite element (FE) simulations and the VDQ method.展开更多
Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism ...Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism for modeling temperature effects.Here,a three-temperaturemodel was developed to describe the energy transfer process between electrons,soft-mode and non-soft-mode phonons.In particular,mode-selective smearing induced soft-mode phonons were assigned a temperature to analyze its contributions to the relaxation between electrons and phonons.A relative standard was established to screen soft-mode phonons quantitatively for different materials.In addition,three smearing methods(Fermi–Dirac,Gaussian,and Methfessel–Paxton)and eight materials(monolayer or bulk TX_(2),T=Ti,Nb,Ta and X=Se,S)were tested.Critical temperatures corrected by the three-temperature model were in great agreement with experimental results.This work provides new insights into correctly predicting critical temperatures of charge density waves,addressing the relaxation process of electrons and phonons using smearing method and determining phase transitions by phonon softening.展开更多
This paper proposes a new approach to the water flow algorithm for text line segmentation. In the basic method the hypothetical water flows under few specified angles which have been defined by water flow angle as par...This paper proposes a new approach to the water flow algorithm for text line segmentation. In the basic method the hypothetical water flows under few specified angles which have been defined by water flow angle as parameter. It is applied to the document image frame from left to right and vice versa. As a result, the unwetted and wetted areas are established. These areas separate text from non-text elements in each text line, respectively. Hence, they represent the control areas that are of major importance for text line segmentation. Primarily, an extended approach means extraction of the connected-components by bounding boxes over text. By this way, each connected component is mutually separated. Hence, the water flow angle, which defines the unwetted areas, is determined adaptively. By choosing appropriate water flow angle, the unwetted areas are lengthening which leads to the better text line segmentation. Results of this approach are encouraging due to the text line segmentation improvement which is the most challenging step in document image processing.展开更多
基金Project supported by the Shanghai Aerospace Science and Technology Innovation Foundation(No.SAST2021048)。
文摘Anisogrid composite lattice conical shells, which exhibit varying stiffness along their cone generators, are widely used as interstage structures in aerospace applications. Buckling under axial compression represents one of the most hazardous failure modes for such structures. In this paper, the smeared stiffness method, which incorporates the effect of component torsion, is used to obtain the equivalent stiffness coefficients for composite lattice conical shells with triangular and hexagonal patterns. A unified framework based on the variational differential quadrature (VDQ) method is established, leveraging its suitability for asymptotic expansion to determine the critical buckling loads and the b-imperfection sensitivity parameter of lattice conical shells with axially varying stiffness due to rib layout. The influence of pre-buckling deformation is taken into account to enhance the accuracy of predictions on the linear buckling loads. The feasibility of the present equivalent continuum model is verified, and the differences in buckling behaviors for composite lattice conical shells with both triangular and hexagonal unit cells are numerically evaluated through the finite element (FE) simulations and the VDQ method.
基金supported by the Guangdong Special Support Program(Grant No.2021TQ06C953)the Shenzhen Science and Technology Programs(Grant No.JCYJ20241202123506009 and GXWD20220811164433002).
文摘Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism for modeling temperature effects.Here,a three-temperaturemodel was developed to describe the energy transfer process between electrons,soft-mode and non-soft-mode phonons.In particular,mode-selective smearing induced soft-mode phonons were assigned a temperature to analyze its contributions to the relaxation between electrons and phonons.A relative standard was established to screen soft-mode phonons quantitatively for different materials.In addition,three smearing methods(Fermi–Dirac,Gaussian,and Methfessel–Paxton)and eight materials(monolayer or bulk TX_(2),T=Ti,Nb,Ta and X=Se,S)were tested.Critical temperatures corrected by the three-temperature model were in great agreement with experimental results.This work provides new insights into correctly predicting critical temperatures of charge density waves,addressing the relaxation process of electrons and phonons using smearing method and determining phase transitions by phonon softening.
文摘This paper proposes a new approach to the water flow algorithm for text line segmentation. In the basic method the hypothetical water flows under few specified angles which have been defined by water flow angle as parameter. It is applied to the document image frame from left to right and vice versa. As a result, the unwetted and wetted areas are established. These areas separate text from non-text elements in each text line, respectively. Hence, they represent the control areas that are of major importance for text line segmentation. Primarily, an extended approach means extraction of the connected-components by bounding boxes over text. By this way, each connected component is mutually separated. Hence, the water flow angle, which defines the unwetted areas, is determined adaptively. By choosing appropriate water flow angle, the unwetted areas are lengthening which leads to the better text line segmentation. Results of this approach are encouraging due to the text line segmentation improvement which is the most challenging step in document image processing.
