A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on...A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on the previous work of Ge, we establish an expression for the surface potential with respect to Qi, and form an implicit equation, from which Qi can be solved. Results predicted by our model are compared to published data as well as results from Schred,a popular 1D numerical solver that solves the Poisson＇s and Schr6dinger equa- tions self-consistently. Good agreement is obtained for a wide range of silicon layer thickness,confirming the supe- riority of this model over previous work in this field.展开更多
Presently developed two-phase turbulence models under-predict the gas turbulent fluctuation, because their turbulence modification models cannot fully reflect the effect of particles. In this paper, a two-time-scale d...Presently developed two-phase turbulence models under-predict the gas turbulent fluctuation, because their turbulence modification models cannot fully reflect the effect of particles. In this paper, a two-time-scale dissipation model of turbulence modification, developed for the two-phase velocity correlation and for the dissipation rate of gas turbulent kinetic energy, is proposed and used to simulate sudden-expansion and swirling gas-particle flows. The proposed two-time scale model gives better results than the single-time scale model. Besides, a gas turbulence augmentation model accounting for the f＇mite-size particle wake effect in the gas Reynolds stress equation is proposed. The proposed turbulence modification models are used to simulate two-phase pipe flows. It can properly predict both turbulence reduction and turbulence enhancement for a certain size of particles observed in experiments.展开更多
Dynamic crack propagation in brittle materials plays an important role in unJerstanding the fracture mechanism.Numerical simulations on crack propagation in the polymethyle methacrylate(PMMA)under explosive loads were...Dynamic crack propagation in brittle materials plays an important role in unJerstanding the fracture mechanism.Numerical simulations on crack propagation in the polymethyle methacrylate(PMMA)under explosive loads were carried out through Autodyn 3D code.Although the Johnson-Holmquist(JH-2)constitutive model has been widely treated as an acceptable scheme,it cannot improve the description in the post-failure response of material and reduce the mesh dependency,so the crack softening failure model are introduced in our present work based on two failure criterions.First,material parameters of JH-2 model,failure criterion,and crack softening failure model are determined from available data and calculations.The circular and rectangle thin plates are modeled to explore the fracture mechanisms for single-borehole and dual-borehole explosions.The simulation results well reproduced the entire dynamic evolutionary process of the crushed and fractured zones,crack initiation,propagation and arrest as well as secondary propagation,which successfully proved the relibilities of the combination of JH-2 constitutive model,failure criterion,and crack softening failure model and corresponding material parameters.For dual-borehole explosion,the crack linkage is well performed when borehole distance L is 20 and 30 cm;cracks are failed to link with each other at L=40 cm although main cracks have arrived into the opposite fractured zone.More importantly,it is found that the crack linkage mainly depends on L,which has an important effect on linkage style and its location.Despite a larger L makes more difficult in crack linkage,this difficulty lies not in the shortage of crack length,but in losing control of directional fracture of cracks between two boreholes.展开更多
文摘A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on the previous work of Ge, we establish an expression for the surface potential with respect to Qi, and form an implicit equation, from which Qi can be solved. Results predicted by our model are compared to published data as well as results from Schred,a popular 1D numerical solver that solves the Poisson＇s and Schr6dinger equa- tions self-consistently. Good agreement is obtained for a wide range of silicon layer thickness,confirming the supe- riority of this model over previous work in this field.
基金Supported by the State Key Development Program for Basic Research of China （No.2006CB200305）, the National Natural Science Foundation of China （No.50376004）, and Ph.D. Program Foundation of Ministry of Education of China （No.20030007028）.
文摘Presently developed two-phase turbulence models under-predict the gas turbulent fluctuation, because their turbulence modification models cannot fully reflect the effect of particles. In this paper, a two-time-scale dissipation model of turbulence modification, developed for the two-phase velocity correlation and for the dissipation rate of gas turbulent kinetic energy, is proposed and used to simulate sudden-expansion and swirling gas-particle flows. The proposed two-time scale model gives better results than the single-time scale model. Besides, a gas turbulence augmentation model accounting for the f＇mite-size particle wake effect in the gas Reynolds stress equation is proposed. The proposed turbulence modification models are used to simulate two-phase pipe flows. It can properly predict both turbulence reduction and turbulence enhancement for a certain size of particles observed in experiments.
基金the Key Research Foundation of Education Bureau of Sichuan Province(Grant No.17zd1122)the Natural Science Foundation of Southwest University of Science and Technology(Grant No.19zx7168)+2 种基金the Shock and Vibration of Engineering Materials and Struc-tures Key Laboratory of Sichuan Province(Grant No.I9kfgk07)the Sci-ence and Technology Department of Sichuan Province(Grant No.2021 YJ0525)National Natural Science Foundation of China(Grant No.11802255).
文摘Dynamic crack propagation in brittle materials plays an important role in unJerstanding the fracture mechanism.Numerical simulations on crack propagation in the polymethyle methacrylate(PMMA)under explosive loads were carried out through Autodyn 3D code.Although the Johnson-Holmquist(JH-2)constitutive model has been widely treated as an acceptable scheme,it cannot improve the description in the post-failure response of material and reduce the mesh dependency,so the crack softening failure model are introduced in our present work based on two failure criterions.First,material parameters of JH-2 model,failure criterion,and crack softening failure model are determined from available data and calculations.The circular and rectangle thin plates are modeled to explore the fracture mechanisms for single-borehole and dual-borehole explosions.The simulation results well reproduced the entire dynamic evolutionary process of the crushed and fractured zones,crack initiation,propagation and arrest as well as secondary propagation,which successfully proved the relibilities of the combination of JH-2 constitutive model,failure criterion,and crack softening failure model and corresponding material parameters.For dual-borehole explosion,the crack linkage is well performed when borehole distance L is 20 and 30 cm;cracks are failed to link with each other at L=40 cm although main cracks have arrived into the opposite fractured zone.More importantly,it is found that the crack linkage mainly depends on L,which has an important effect on linkage style and its location.Despite a larger L makes more difficult in crack linkage,this difficulty lies not in the shortage of crack length,but in losing control of directional fracture of cracks between two boreholes.
