The band structures of both in-plane and anti-plane elastic waves propagating in two-dimensional ordered and disordered （in one direction） phononic crystals are studied in this paper. The localization of wave propag...The band structures of both in-plane and anti-plane elastic waves propagating in two-dimensional ordered and disordered （in one direction） phononic crystals are studied in this paper. The localization of wave propagation due to random disorder is discussed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method. By treating the quasi-periodicity as the deviation from the periodicity in a special way, two kinds of quasi phononic crystal that has quasi-periodicity （Fibonacci sequence） in one direction and translational symmetry in the other direction are considered and the band structures are characterized by using localization factors. The results show that the localization factor is an effective parameter in characterizing the band gaps of two-dimensional perfect, randomly disordered and quasi-periodic phononic crystals. Band structures of the phononic crystals can be tuned by different random disorder or changing quasi-periodic parameters. The quasi phononic crystals exhibit more band gaps with narrower width than the ordered and randomly disordered systems.展开更多
Many studies suggest that there are distinct regulatory processes controlling compound leaf development in different clades of legumes.Loss of function of the LEAFY(LFY)orthologs results in a reduction of leaf complex...Many studies suggest that there are distinct regulatory processes controlling compound leaf development in different clades of legumes.Loss of function of the LEAFY(LFY)orthologs results in a reduction of leaf complexity to different degrees in inverted repeat-lacking clade(IRLC)and non-IRLC species.To further understand the role of LFY orthologs and the molecular mechanism in compound leaf development in non-IRLC plants,we studied leaf development in unifoliate leaf(un)mutant,a classical mutant of mungbean(Vigna radiata L.),which showed a complete conversion of compound leaves into simple leaves.Our analysis revealed that UN encoded the mungbean LFY ortholog(VrLFY)and played a significant role in leaf development.In situ RNA hybridization results showed that STM-like KNOXI genes were expressed in compound leaf primordia in mungbean.Furthermore,increased leaflet number in heptafoliate leaflets1(hel1)mutants was demonstrated to depend on the function of VrLFY and KNOXI genes in mungbean.Our results suggested that HEL1 is a key factor coordinating distinct processes in the control of compound leaf development in mungbean and its related non-IRLC legumes.展开更多
The dominant deformation mode at low temperatures for magnesium and its alloys is generally regarded to be twinning because of the hcp crystal structure. More recently, the phenomenon of a ＂loss＂ of the twins has be...The dominant deformation mode at low temperatures for magnesium and its alloys is generally regarded to be twinning because of the hcp crystal structure. More recently, the phenomenon of a ＂loss＂ of the twins has been reported in microcompression experiments of the magnesium single crystals. Molecular dynamics simulation of compression deformation shows that the pyramidal 〈α ＋ c〉 slip dominates compression behavior at the nanoscale. No compression twins are observed at different temperatures at different loadings and boundary conditions. This is explained by the analyses, that is, the {10^_12} and {10^11} twins can be activated under c-axis tension, while compression twins will not occur when the c/α ratio of the hcp metal is below √3. Our theoretical and simulation results are consistent with recent microcompression experiments of the magnesium （0001） single crystals.展开更多
The deformation behavior in magnesium single crystal under c-axis tension is investigated in a temperature range between 250 K and 570 K by molecular dynamics simulations. At a low temperature, twinning and shear band...The deformation behavior in magnesium single crystal under c-axis tension is investigated in a temperature range between 250 K and 570 K by molecular dynamics simulations. At a low temperature, twinning and shear bands are found to be the main deformation mechanisms. In particular, the {102} tension twins with the reorientation angle of about 90 °are observed in the simulations. The mechanisms of {102} twinning are illustrated by the simulated motion of atoms. Moreover, grain nucleation and growth are found to be accompanied with the {102} twinning. At temperatures above 450 K, the twin frequency decreases with increasing temperature. The {102} extension twin almost disappears at the temperature of 570 K. The non-basal slip plays an important role on the tensile deformation in magnesium single crystal at high temperatures.展开更多
基金supported by the National Natural Science Foundation of China(No.10632020).
文摘The band structures of both in-plane and anti-plane elastic waves propagating in two-dimensional ordered and disordered （in one direction） phononic crystals are studied in this paper. The localization of wave propagation due to random disorder is discussed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method. By treating the quasi-periodicity as the deviation from the periodicity in a special way, two kinds of quasi phononic crystal that has quasi-periodicity （Fibonacci sequence） in one direction and translational symmetry in the other direction are considered and the band structures are characterized by using localization factors. The results show that the localization factor is an effective parameter in characterizing the band gaps of two-dimensional perfect, randomly disordered and quasi-periodic phononic crystals. Band structures of the phononic crystals can be tuned by different random disorder or changing quasi-periodic parameters. The quasi phononic crystals exhibit more band gaps with narrower width than the ordered and randomly disordered systems.
基金supported by the National Natural Science Foundation of China(Grant No.31700186)the Ministry of Agriculture of China for Transgenic Research(Grant No.2014ZX0800943B).
文摘Many studies suggest that there are distinct regulatory processes controlling compound leaf development in different clades of legumes.Loss of function of the LEAFY(LFY)orthologs results in a reduction of leaf complexity to different degrees in inverted repeat-lacking clade(IRLC)and non-IRLC species.To further understand the role of LFY orthologs and the molecular mechanism in compound leaf development in non-IRLC plants,we studied leaf development in unifoliate leaf(un)mutant,a classical mutant of mungbean(Vigna radiata L.),which showed a complete conversion of compound leaves into simple leaves.Our analysis revealed that UN encoded the mungbean LFY ortholog(VrLFY)and played a significant role in leaf development.In situ RNA hybridization results showed that STM-like KNOXI genes were expressed in compound leaf primordia in mungbean.Furthermore,increased leaflet number in heptafoliate leaflets1(hel1)mutants was demonstrated to depend on the function of VrLFY and KNOXI genes in mungbean.Our results suggested that HEL1 is a key factor coordinating distinct processes in the control of compound leaf development in mungbean and its related non-IRLC legumes.
基金supported by the National Natural Science Foundation of China (Nos. 11072026 and 10632020)the Fundamental Research Funds for the Central Universities (No. 2009JBZ015)
文摘The dominant deformation mode at low temperatures for magnesium and its alloys is generally regarded to be twinning because of the hcp crystal structure. More recently, the phenomenon of a ＂loss＂ of the twins has been reported in microcompression experiments of the magnesium single crystals. Molecular dynamics simulation of compression deformation shows that the pyramidal 〈α ＋ c〉 slip dominates compression behavior at the nanoscale. No compression twins are observed at different temperatures at different loadings and boundary conditions. This is explained by the analyses, that is, the {10^_12} and {10^11} twins can be activated under c-axis tension, while compression twins will not occur when the c/α ratio of the hcp metal is below √3. Our theoretical and simulation results are consistent with recent microcompression experiments of the magnesium （0001） single crystals.
基金supported by National Natural Science Foundation of China (GrantNos.11072026 and 10632020)the Fundamental Research Funds for the Central Universities, and finalized during a sabbatical leave of D.S. at the Graduate Institute of Ferrous Technology (G.I.F.T.) of POSTECHPohang, Korea as part of an International Outgoing Fellowship (Marie Curie Actions) of the 7th Programme of the European Commission
文摘The deformation behavior in magnesium single crystal under c-axis tension is investigated in a temperature range between 250 K and 570 K by molecular dynamics simulations. At a low temperature, twinning and shear bands are found to be the main deformation mechanisms. In particular, the {102} tension twins with the reorientation angle of about 90 °are observed in the simulations. The mechanisms of {102} twinning are illustrated by the simulated motion of atoms. Moreover, grain nucleation and growth are found to be accompanied with the {102} twinning. At temperatures above 450 K, the twin frequency decreases with increasing temperature. The {102} extension twin almost disappears at the temperature of 570 K. The non-basal slip plays an important role on the tensile deformation in magnesium single crystal at high temperatures.
