The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low im...The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low impedance medium is introduced to replace the free stress boundary, which largely reduces the computational complexity. The dependence of band gaps on structural parameters is investigated in detail. To prove the validity of the super-cell plane wave expansion, the transmitted power spectra of the Lamb wave are calculated by using a finite element method. With the detailed computation, the band-gap of a one-dimensional plate can be designed as required with appropriate structural parameters, which provides a guide to the fabrication of a Lamb wave phononic crystal.展开更多
The structural parameters, the formation energies, and the elastic and thermodynamic properties of the （CuxNi1-x）3Sn phase with different structures are studied by the virtual crystal approximation （VCA） and super...The structural parameters, the formation energies, and the elastic and thermodynamic properties of the （CuxNi1-x）3Sn phase with different structures are studied by the virtual crystal approximation （VCA） and super-cell （SC） methods. The lattice constants, formation energies, and elastic constants obtained by SC and VCA are generally consistent with each other. It can be inferred that ttle VCA method is suitable for （CuxNil ,）3Sn ordered phase calculation. The calculated results show that the equilibrium structures of Cu3Sn and Ni3Sn are D0a and D019 respectively. （CuxNi1-x）3Sn D03 with various components are the mctastable phase at temperature of 0 K, just as D022 and L I2. With the temperature increase, tile free energy of the D03 is lower than those of D022 and L12, and D022 and L12 eventually turn into D03 in tile aging process. The （CuxNi1-x）3Sn D022 is first precipitated in a solid solution because its structure and cell volume are most similar to Ihose of a solid solution matrix. The LI2 and the D022 possess better mechanical stability than the D03. Also, they may play a more important role in the strengthening of Cu-Ni-Sn alloys. This study is valuable lk）r further research on Cu-Ni-Sn alloys.展开更多
An attempt has been made in the present research to simulate a deadly flash-flood event over the City of Skopje,Macedonia on 6 August 2016.A cloud model ensemble forecast method is developed to simulate a super-cell s...An attempt has been made in the present research to simulate a deadly flash-flood event over the City of Skopje,Macedonia on 6 August 2016.A cloud model ensemble forecast method is developed to simulate a super-cell storm’s initiation and evolutionary features.Sounding data are generated using an ensemble approach,that utilizes a triple-nested WRF model.A three-dimensional(3-D)convective cloud model(CCM)with a very fine horizontal grid resolution of 250-m is initialized,using the initial representative sounding data,derived from the WRF 1-km forecast outputs.CCM is configured and run with an open lateral boundary conditions LBC,allowing explicit simulation of convective scale processes.This preliminary study showed that the ensemble approach has some advantages in the generation of the initial data and the model initialization.The applied method minimizes the uncertainties and provides a more qualitative-quantitative assessment of super-cell storm initiation,cell structure,evolutionary properties,and intensity.A high-resolution 3-D run is capable to resolve detailed aspects of convection,including high-intensity convective precipitation.The results are significant not only from the aspect of the cloud model’s ability to provide a qualitative-quantitative assessment of intense precipitation but also for a deeper understanding of the essence of storm development,its vortex dynamics,and the meaning of micro-physical processes for the production and release of large amounts of precipitation that were the cause of the catastrophic flood in an urban area.After a series of experiments and verification,such a system could be a reliable tool in weather services for very short-range forecasting(now-casting)and early warning of weather disasters.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874086 and 10834009)the National Basic Research Program of China (Grant No. 2010CB327803)
文摘The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low impedance medium is introduced to replace the free stress boundary, which largely reduces the computational complexity. The dependence of band gaps on structural parameters is investigated in detail. To prove the validity of the super-cell plane wave expansion, the transmitted power spectra of the Lamb wave are calculated by using a finite element method. With the detailed computation, the band-gap of a one-dimensional plate can be designed as required with appropriate structural parameters, which provides a guide to the fabrication of a Lamb wave phononic crystal.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0301402)the Project of Innovation-Driven Plan in Central South Universitythe State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China
文摘The structural parameters, the formation energies, and the elastic and thermodynamic properties of the （CuxNi1-x）3Sn phase with different structures are studied by the virtual crystal approximation （VCA） and super-cell （SC） methods. The lattice constants, formation energies, and elastic constants obtained by SC and VCA are generally consistent with each other. It can be inferred that ttle VCA method is suitable for （CuxNil ,）3Sn ordered phase calculation. The calculated results show that the equilibrium structures of Cu3Sn and Ni3Sn are D0a and D019 respectively. （CuxNi1-x）3Sn D03 with various components are the mctastable phase at temperature of 0 K, just as D022 and L I2. With the temperature increase, tile free energy of the D03 is lower than those of D022 and L12, and D022 and L12 eventually turn into D03 in tile aging process. The （CuxNi1-x）3Sn D022 is first precipitated in a solid solution because its structure and cell volume are most similar to Ihose of a solid solution matrix. The LI2 and the D022 possess better mechanical stability than the D03. Also, they may play a more important role in the strengthening of Cu-Ni-Sn alloys. This study is valuable lk）r further research on Cu-Ni-Sn alloys.
文摘An attempt has been made in the present research to simulate a deadly flash-flood event over the City of Skopje,Macedonia on 6 August 2016.A cloud model ensemble forecast method is developed to simulate a super-cell storm’s initiation and evolutionary features.Sounding data are generated using an ensemble approach,that utilizes a triple-nested WRF model.A three-dimensional(3-D)convective cloud model(CCM)with a very fine horizontal grid resolution of 250-m is initialized,using the initial representative sounding data,derived from the WRF 1-km forecast outputs.CCM is configured and run with an open lateral boundary conditions LBC,allowing explicit simulation of convective scale processes.This preliminary study showed that the ensemble approach has some advantages in the generation of the initial data and the model initialization.The applied method minimizes the uncertainties and provides a more qualitative-quantitative assessment of super-cell storm initiation,cell structure,evolutionary properties,and intensity.A high-resolution 3-D run is capable to resolve detailed aspects of convection,including high-intensity convective precipitation.The results are significant not only from the aspect of the cloud model’s ability to provide a qualitative-quantitative assessment of intense precipitation but also for a deeper understanding of the essence of storm development,its vortex dynamics,and the meaning of micro-physical processes for the production and release of large amounts of precipitation that were the cause of the catastrophic flood in an urban area.After a series of experiments and verification,such a system could be a reliable tool in weather services for very short-range forecasting(now-casting)and early warning of weather disasters.
