A few constitutive models for unsaturated soils have already been proposed,however,many classic models such as the Barcelona basic model can simulate neither complex volumetric soil behaviour（without forgetting its s...A few constitutive models for unsaturated soils have already been proposed,however,many classic models such as the Barcelona basic model can simulate neither complex volumetric soil behaviour（without forgetting its supreme merit of being the first consistently and rigorously formulated model） nor post-peak softening,and most advanced models generally comprise a large number of parameters making them more difficult to be applied to practical situations.In this paper,we present a new model for unsaturated soils based on an existing model developed originally for saturated soils.It comprises a minimum number of constitutive parameters.The extension to unsaturated state is achieved by following a general methodology previously developed in our laboratory.The capacities of this simple model are tested.With only 13 parameters,it can reproduce the basic behaviour of unsaturated soils such as rebound or collapse upon wetting,depending on the stress levels.It can also reproduce post-peak softening and transition from contractant to dilatant volumetric behaviour during undrained shear.Overall,the first tentative of validation gives a good correlation between simulations and experimental data,and shows encouraging signs for future developments.展开更多
Temperature dependences of the high-field electron trapping in a SiO_(2) thin film for temperature ranging from 100 to 423K are investigated.It is found that in the investigated temperature range,when the temperature ...Temperature dependences of the high-field electron trapping in a SiO_(2) thin film for temperature ranging from 100 to 423K are investigated.It is found that in the investigated temperature range,when the temperature decreases the effective surface density of the electron traps in the film decreases;the energy levels of the effective electron traps at high field concentrate at very narrow energy range.The thermal generation rate is found to be 1.283x10^(10)/cm^(2).K and its activation energy is 0.192eV.Based on these results,a model for the electron traps generated at high field in thin oxide is proposed.展开更多
The behaviors of constant electric field stressing of the thin(200Å)oxynitride and re-oxidized oxynitride films are investigated.The flat-band shift is not a simple function of the stressing field.The observed ph...The behaviors of constant electric field stressing of the thin(200Å)oxynitride and re-oxidized oxynitride films are investigated.The flat-band shift is not a simple function of the stressing field.The observed phenomena are attributed to the significance of trap filling,electronic tunneling and trap generation at different stressing field strengths.Re-oxidized sample is found to have high resistant to the electron tunneling and trap generation.展开更多
文摘A few constitutive models for unsaturated soils have already been proposed,however,many classic models such as the Barcelona basic model can simulate neither complex volumetric soil behaviour（without forgetting its supreme merit of being the first consistently and rigorously formulated model） nor post-peak softening,and most advanced models generally comprise a large number of parameters making them more difficult to be applied to practical situations.In this paper,we present a new model for unsaturated soils based on an existing model developed originally for saturated soils.It comprises a minimum number of constitutive parameters.The extension to unsaturated state is achieved by following a general methodology previously developed in our laboratory.The capacities of this simple model are tested.With only 13 parameters,it can reproduce the basic behaviour of unsaturated soils such as rebound or collapse upon wetting,depending on the stress levels.It can also reproduce post-peak softening and transition from contractant to dilatant volumetric behaviour during undrained shear.Overall,the first tentative of validation gives a good correlation between simulations and experimental data,and shows encouraging signs for future developments.
基金Supported in part by the Strategic Research Grant of City University of Hong Kong
文摘Temperature dependences of the high-field electron trapping in a SiO_(2) thin film for temperature ranging from 100 to 423K are investigated.It is found that in the investigated temperature range,when the temperature decreases the effective surface density of the electron traps in the film decreases;the energy levels of the effective electron traps at high field concentrate at very narrow energy range.The thermal generation rate is found to be 1.283x10^(10)/cm^(2).K and its activation energy is 0.192eV.Based on these results,a model for the electron traps generated at high field in thin oxide is proposed.
基金Supported in part by the National Natural Science Foundation of Chinathe Croucher Foundation and the UPGC research grant of Hong Kong。
文摘The behaviors of constant electric field stressing of the thin(200Å)oxynitride and re-oxidized oxynitride films are investigated.The flat-band shift is not a simple function of the stressing field.The observed phenomena are attributed to the significance of trap filling,electronic tunneling and trap generation at different stressing field strengths.Re-oxidized sample is found to have high resistant to the electron tunneling and trap generation.
