The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying L...The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying Lyapunov stability method, the state feedback control laws are designed and the close-loop error systems are proved to be uniformly asymptotically stable by Matrosov theorem. In particular, the controller does not need knowledge on system parameters in the case of set-point stabilization, which makes the controller robust with respect to parameter uncertainty. Numerical simulations illustrate the effectiveness of the controller designed.展开更多
In order to study the relationship between the main process parameters and the cell size,the mathematical model of cell growth of microcellular foaming injection process is built.Then numeric simulation is employed as...In order to study the relationship between the main process parameters and the cell size,the mathematical model of cell growth of microcellular foaming injection process is built.Then numeric simulation is employed as experimental method,and the Taguchi method is used to analyze significance of effect of process parameters on the cell size.At last the process parameters are focused on melt temperature,injection time,mold temperature and pre-filled volume.The significance order from big to small of the effect of each process parameters on cell size is melt temperature,pre-filled volume,injection time,and mold temperature.On the basis of above research,the effect of each process parameter on cell size is further researched.Appropriate reduction of the melt temperature and increase of the pre-filled volume can optimize the cell size effectively,while the effects of injection time and mold temperature on cell size are less significant.展开更多
β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 th...β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 that results the 4T2 to 4A2 transition and show broad emission around 690 nm. β-Ga2O3 single crystals doped with different Cr3+ concentrations were grown by floating zone technique. Their absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were calculated based on the absorption spectra.展开更多
Nitridated β-Ga2O3 （100） substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of β-Ga2O3 wafers on the formation of GaN were studied. I...Nitridated β-Ga2O3 （100） substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of β-Ga2O3 wafers on the formation of GaN were studied. It was found that the most optimized nitridation temperature was 900 ℃, and hexagonal GaN with preferred orientation was produced on the well-polished wafer. The nitridation mechanism was also discussed.展开更多
文摘The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying Lyapunov stability method, the state feedback control laws are designed and the close-loop error systems are proved to be uniformly asymptotically stable by Matrosov theorem. In particular, the controller does not need knowledge on system parameters in the case of set-point stabilization, which makes the controller robust with respect to parameter uncertainty. Numerical simulations illustrate the effectiveness of the controller designed.
文摘In order to study the relationship between the main process parameters and the cell size,the mathematical model of cell growth of microcellular foaming injection process is built.Then numeric simulation is employed as experimental method,and the Taguchi method is used to analyze significance of effect of process parameters on the cell size.At last the process parameters are focused on melt temperature,injection time,mold temperature and pre-filled volume.The significance order from big to small of the effect of each process parameters on cell size is melt temperature,pre-filled volume,injection time,and mold temperature.On the basis of above research,the effect of each process parameter on cell size is further researched.Appropriate reduction of the melt temperature and increase of the pre-filled volume can optimize the cell size effectively,while the effects of injection time and mold temperature on cell size are less significant.
基金Project supported by the National Natural Science Foundation of China (50472032) and Hundred Talents Program of Chinese Academy of Sciences
文摘β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 that results the 4T2 to 4A2 transition and show broad emission around 690 nm. β-Ga2O3 single crystals doped with different Cr3+ concentrations were grown by floating zone technique. Their absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were calculated based on the absorption spectra.
基金the National Natural Science Foundation of China under Grant No.50672105the Hundred Talents Program of Chinese Academy of Sciences.
文摘Nitridated β-Ga2O3 （100） substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of β-Ga2O3 wafers on the formation of GaN were studied. It was found that the most optimized nitridation temperature was 900 ℃, and hexagonal GaN with preferred orientation was produced on the well-polished wafer. The nitridation mechanism was also discussed.
