In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element me...In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element method （FEM）. The stresses and strains are concentrated at the boundaries of the WL and QDs, are reduced gradually from the boundaries to the interior, and tend to a uniform state for the positions away from the boundaries. The maximal strain energy density occurs at the vicinity of the interface between the WL and the substrate. The stresses, strains and released strain energy are reduced gradually with increasing WL thickness. The above results show that a critical WL thickness may exist, and the stress and strain distributions can make the growth of QDs a growth of strained three-dimensional island when the WL thickness is above the critical value, and FEM can be applied to investigate such nanosystems, QDs, and the relevant results are supported by the experiments.展开更多
High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increa...High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increased ramp time is a known disadvantage of the NI approach. To solve this problem, a proportional and integral(PI) active feedback control has been proposed in the charging experiments of the NI magnet. In this study, the electromagnetic-thermal-mechanical characteristics of an NI magnet with and without PI are analyzed to ensure the safety and reliability of PI control. Due to the increase in the radial current of the magnet, the turn-to-turn loss energy of the magnet with PI is more than twice that without PI. However, the magnetization loss energy of the magnet has a small difference with and without PI. It can be also found that the NI magnet with PI has a large temperature rise, and thus it has a low thermal stability margin. Moreover, in the high field, the hoop stress and hoop strain peaks of a magnet with PI are larger than those without PI. Thus, PI control can induce a relatively high risk of mechanical damage in the applications of NI magnets.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 90101004） and by the National Basic Research Program of China （Grant No G2000067102）.
文摘In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots （QDs） with different wetting layer （WL） thickness, using the finite element method （FEM）. The stresses and strains are concentrated at the boundaries of the WL and QDs, are reduced gradually from the boundaries to the interior, and tend to a uniform state for the positions away from the boundaries. The maximal strain energy density occurs at the vicinity of the interface between the WL and the substrate. The stresses, strains and released strain energy are reduced gradually with increasing WL thickness. The above results show that a critical WL thickness may exist, and the stress and strain distributions can make the growth of QDs a growth of strained three-dimensional island when the WL thickness is above the critical value, and FEM can be applied to investigate such nanosystems, QDs, and the relevant results are supported by the experiments.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11872195, and 11932008)Fundamental Research Funds for the Central Universities (Grant No. lzujbky-2020-1)。
文摘High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increased ramp time is a known disadvantage of the NI approach. To solve this problem, a proportional and integral(PI) active feedback control has been proposed in the charging experiments of the NI magnet. In this study, the electromagnetic-thermal-mechanical characteristics of an NI magnet with and without PI are analyzed to ensure the safety and reliability of PI control. Due to the increase in the radial current of the magnet, the turn-to-turn loss energy of the magnet with PI is more than twice that without PI. However, the magnetization loss energy of the magnet has a small difference with and without PI. It can be also found that the NI magnet with PI has a large temperature rise, and thus it has a low thermal stability margin. Moreover, in the high field, the hoop stress and hoop strain peaks of a magnet with PI are larger than those without PI. Thus, PI control can induce a relatively high risk of mechanical damage in the applications of NI magnets.
