In this paper, we describe the saturation effect of a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) fabricated on a thin silicon-on-insulator (SOI) with a step-by-step derivation of the model ...In this paper, we describe the saturation effect of a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) fabricated on a thin silicon-on-insulator (SOI) with a step-by-step derivation of the model formulation. The collector injection width, the internal base-collector bias, and the hole density at the base-collector junction interface are analysed by considering the unique features of the internal and the external parts of the collector, as they are different from those of a bulk counterpart.展开更多
The ion saturation current is very important in probe theory, which can be used to measure the electron temperature and the floating potential. In this work, the effects of energetic ions on the ion saturation current...The ion saturation current is very important in probe theory, which can be used to measure the electron temperature and the floating potential. In this work, the effects of energetic ions on the ion saturation current are studied via particle-in-cell simulations. It is found that the energetic ions and background ions can be treated separately as different species, and they satisfy their individual Bohm criterion at the sheath edge. It is shown that the energetic ions can significantly affect the ion saturation current if their concentration is greater than root T-e/(gamma T-i2(i2)), where T-e is the electron temperature, and gamma(i2) and T-i2 represent the polytropic coefficient and temperature of energetic ions, respectively. As a result, the floating potential and the I-V characteristic profile are strongly influenced by the energetic ions. When the energetic ion current dominates the ion saturation current, an analysis of the ion saturation current will yield the energetic ion temperature rather than the electron temperature.展开更多
Using a strong nonlinear saturation absorption effect is one technique for breaking through the diffraction limit. In this technique, formation of a dynamic and reversible optical pinhole channel and transient superre...Using a strong nonlinear saturation absorption effect is one technique for breaking through the diffraction limit. In this technique, formation of a dynamic and reversible optical pinhole channel and transient superresolution is critical. In this work, a pump–probe transient detection and observation–experimental setup is constructed to explore the formation process directly. A Ge2Sb2Te5 thin film with strong nonlinear saturation absorption is investigated. The dynamic evolution of the optical pinhole channel is detected and imaged, and the transient superresolution spot is directly captured experimentally. Results verify that the superresolution effect originates from the generation of an optical pinhole channel and that the formation of the optical pinhole channel is dynamic and reversible. A good method is provided for direct detection and observation of the transient process of the superresolution effect of nonlinear thin films.展开更多
With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.Luo Junwei(骆军委)from the Institute of Semiconductors,Chinese Academy of Sciences discovered a rapid tran...With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.Luo Junwei(骆军委)from the Institute of Semiconductors,Chinese Academy of Sciences discovered a rapid transition of the hole Rashba effect from strong field dependence to saturation展开更多
The infiltration,evaporation and variation of the groundwater table have significant effects on the suction stress of the soils and the supporting earth pressures of the foundation excavation.The distribution of the s...The infiltration,evaporation and variation of the groundwater table have significant effects on the suction stress of the soils and the supporting earth pressures of the foundation excavation.The distribution of the suction stresses above the ground water table is derived under different fluxes at the ground surface,according to the soil-water characteristic parameters and the effective degree of saturation.In consideration of the cohesive stress formed from the soil suction stress and the relevant anti sliding effect,the calculation model of supporting earth pressures for foundation excavation is established by the variational limit equilibrium method under the steady flow condition.The evolution of the supporting earth pressures is studied in detail for foundation excavation under different fluxes at the ground surface.The effects of the soil-water characteristic parameters,the ground water table and the internal friction angle on the supporting earth pressures are discussed.The results show that the suction stress is reduced because of the infiltration,and thus the supporting earth pressure increases.The larger the air-entry pressures and the pore size are,the smaller the supporting earth pressures are.The higher the ground water table is,the larger the supporting earth pressures are.In order to reduce the construction risk,the effects of the suction stress and the evolution of the potential critical sliding surface should be considered during the calculation of the supporting earth pressures.展开更多
We demonstrate an intracavity self-synchronized multi-color Q-switched fiber laser using a parallel-integrated fiber Bragg grating(PI-FBG), fabricated by a femtosecond laser with a point-by-point parallel inscription ...We demonstrate an intracavity self-synchronized multi-color Q-switched fiber laser using a parallel-integrated fiber Bragg grating(PI-FBG), fabricated by a femtosecond laser with a point-by-point parallel inscription method. The multi-color Q-switched pulses can be always self-synchronized when the group delay differences between neighboring spectra range from-3.4 to 3.4 ps.The starting and evolution dynamics indicate that the saturable absorption effect of the carbon nanotube plays a dual role: synchronously triggering the startup of the pulse at successive colors by active Q-switching and spontaneously compensating to some extent the temporal walk-off of the multi-color pulses through the cross saturable absorption modulation. This work unveils the intracavity self-synchronization mechanism of the multi-color Q-switched pulses and also demonstrates the potential of PI-FBGs for the customizable generation of the synchronized multi-color pulse in a single cavity.展开更多
基金Project supported by the National Ministries and Commissions,China (Grant Nos.51308040203 and 6139801)the Fundamental Research Funds for the Central Universities,China (Grant Nos.72105499 and 72104089)the Basic Natural Science Research Program in Shaanxi Province,China (Grant No.2010JQ8008)
文摘In this paper, we describe the saturation effect of a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) fabricated on a thin silicon-on-insulator (SOI) with a step-by-step derivation of the model formulation. The collector injection width, the internal base-collector bias, and the hole density at the base-collector junction interface are analysed by considering the unique features of the internal and the external parts of the collector, as they are different from those of a bulk counterpart.
基金Supported by the Program of Fusion Reactor Physics and Digital Tokamak with the Chinese Academy of Sciences'One-Three Five'Strategic Planningthe JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics(NSFC No 11261140328 and NRF No 2012K2A2A6000443)+1 种基金the National ITER Program of China under Grant No 2015GB101003the National Natural Science Foundation of China under Grant Nos 11405215,11475223 and 11505236
文摘The ion saturation current is very important in probe theory, which can be used to measure the electron temperature and the floating potential. In this work, the effects of energetic ions on the ion saturation current are studied via particle-in-cell simulations. It is found that the energetic ions and background ions can be treated separately as different species, and they satisfy their individual Bohm criterion at the sheath edge. It is shown that the energetic ions can significantly affect the ion saturation current if their concentration is greater than root T-e/(gamma T-i2(i2)), where T-e is the electron temperature, and gamma(i2) and T-i2 represent the polytropic coefficient and temperature of energetic ions, respectively. As a result, the floating potential and the I-V characteristic profile are strongly influenced by the energetic ions. When the energetic ion current dominates the ion saturation current, an analysis of the ion saturation current will yield the energetic ion temperature rather than the electron temperature.
基金partially supported by National Natural Science Foundation of China (Nos. 51172253 and 61137002)
文摘Using a strong nonlinear saturation absorption effect is one technique for breaking through the diffraction limit. In this technique, formation of a dynamic and reversible optical pinhole channel and transient superresolution is critical. In this work, a pump–probe transient detection and observation–experimental setup is constructed to explore the formation process directly. A Ge2Sb2Te5 thin film with strong nonlinear saturation absorption is investigated. The dynamic evolution of the optical pinhole channel is detected and imaged, and the transient superresolution spot is directly captured experimentally. Results verify that the superresolution effect originates from the generation of an optical pinhole channel and that the formation of the optical pinhole channel is dynamic and reversible. A good method is provided for direct detection and observation of the transient process of the superresolution effect of nonlinear thin films.
文摘With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.Luo Junwei(骆军委)from the Institute of Semiconductors,Chinese Academy of Sciences discovered a rapid transition of the hole Rashba effect from strong field dependence to saturation
基金the National Natural Science Foundation of China(No.41272288)。
文摘The infiltration,evaporation and variation of the groundwater table have significant effects on the suction stress of the soils and the supporting earth pressures of the foundation excavation.The distribution of the suction stresses above the ground water table is derived under different fluxes at the ground surface,according to the soil-water characteristic parameters and the effective degree of saturation.In consideration of the cohesive stress formed from the soil suction stress and the relevant anti sliding effect,the calculation model of supporting earth pressures for foundation excavation is established by the variational limit equilibrium method under the steady flow condition.The evolution of the supporting earth pressures is studied in detail for foundation excavation under different fluxes at the ground surface.The effects of the soil-water characteristic parameters,the ground water table and the internal friction angle on the supporting earth pressures are discussed.The results show that the suction stress is reduced because of the infiltration,and thus the supporting earth pressure increases.The larger the air-entry pressures and the pore size are,the smaller the supporting earth pressures are.The higher the ground water table is,the larger the supporting earth pressures are.In order to reduce the construction risk,the effects of the suction stress and the evolution of the potential critical sliding surface should be considered during the calculation of the supporting earth pressures.
基金supported by the National Natural Science Foundation of China (No. 12274344)the Natural Science Basic Research Program of Shaanxi (No. 2023-JC-YB-563)the Guangdong Basic and Applied Basic Research Foundation (No. 2023A1515011517)。
文摘We demonstrate an intracavity self-synchronized multi-color Q-switched fiber laser using a parallel-integrated fiber Bragg grating(PI-FBG), fabricated by a femtosecond laser with a point-by-point parallel inscription method. The multi-color Q-switched pulses can be always self-synchronized when the group delay differences between neighboring spectra range from-3.4 to 3.4 ps.The starting and evolution dynamics indicate that the saturable absorption effect of the carbon nanotube plays a dual role: synchronously triggering the startup of the pulse at successive colors by active Q-switching and spontaneously compensating to some extent the temporal walk-off of the multi-color pulses through the cross saturable absorption modulation. This work unveils the intracavity self-synchronization mechanism of the multi-color Q-switched pulses and also demonstrates the potential of PI-FBGs for the customizable generation of the synchronized multi-color pulse in a single cavity.