As an integrated structure,an arch dam is assumed to bear loads in its design consideration.However,multi-defects,such as cracks and the opening of transverse joints,are unavoidable during construction and operation.M...As an integrated structure,an arch dam is assumed to bear loads in its design consideration.However,multi-defects,such as cracks and the opening of transverse joints,are unavoidable during construction and operation.Multi-defects will reduce the structural integrity and stiffness of the dam and affect its working performance and degree of safety.In the current paper,a numerical model of defects and a simulation method of a high arch dam are introduced.The Chencun arch dam is analyzed as a case study.An entire course simulation analysis of the Chencun arch dam from construction to operation is carried out,through which the opening of the transverse and longitudinal joints,formation of cracks,and their influence on deformation and stress of the dam are studied.According to the results of the analysis,appropriate measures should be adopted to prevent the development of cracks,and observation should be strengthened for a more timely discovery of risks.展开更多
The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Ha...The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods. The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO, which make the p-type conductance hard to obtain. The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO. However, the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment. Therefore, p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.展开更多
Electronic properties of multi-defected zigzag single-walled carbon nanotubes are investigated by use of the tight-binding Green's function method. The Stone-Wales defects and the vacancies are considered. We find...Electronic properties of multi-defected zigzag single-walled carbon nanotubes are investigated by use of the tight-binding Green's function method. The Stone-Wales defects and the vacancies are considered. We find that the conductance sensitively depends on the realistic defect configurations for the metallic zigzag carbon nanotubes. Interestingly, the electronic transport properties of the nanotubes with three vacancies can be considered as the sum effect of two double-vacancies, while those with Stone-Wales defects can not. The electron interference along the longitudinal axis and the transport blocking are observed, which may be useful for understanding the electron transport behavior of carbon nanotube in experiments.展开更多
基金supported by the National Key Technology R&D Program (Grant No.2008BAB29B05)the National Natural Science Foundation of China(Grant No.50909105)+1 种基金the Public Industry Research Special Funds of MWR(Grant No.200801007)the Research Special Funds of IWHR
文摘As an integrated structure,an arch dam is assumed to bear loads in its design consideration.However,multi-defects,such as cracks and the opening of transverse joints,are unavoidable during construction and operation.Multi-defects will reduce the structural integrity and stiffness of the dam and affect its working performance and degree of safety.In the current paper,a numerical model of defects and a simulation method of a high arch dam are introduced.The Chencun arch dam is analyzed as a case study.An entire course simulation analysis of the Chencun arch dam from construction to operation is carried out,through which the opening of the transverse and longitudinal joints,formation of cracks,and their influence on deformation and stress of the dam are studied.According to the results of the analysis,appropriate measures should be adopted to prevent the development of cracks,and observation should be strengthened for a more timely discovery of risks.
文摘The electronic properties and stability of Li-doped ZnO with various defects have been stud- ied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods. The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO, which make the p-type conductance hard to obtain. The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO. However, the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment. Therefore, p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.
基金supported by the Ministry of Science and Technology of Chinathe Ministry of Education of Chinathe National Natural Science Foundation of China
文摘Electronic properties of multi-defected zigzag single-walled carbon nanotubes are investigated by use of the tight-binding Green's function method. The Stone-Wales defects and the vacancies are considered. We find that the conductance sensitively depends on the realistic defect configurations for the metallic zigzag carbon nanotubes. Interestingly, the electronic transport properties of the nanotubes with three vacancies can be considered as the sum effect of two double-vacancies, while those with Stone-Wales defects can not. The electron interference along the longitudinal axis and the transport blocking are observed, which may be useful for understanding the electron transport behavior of carbon nanotube in experiments.
