The ground-state energy and the average number of virtual phonons around the electron in a parabolic quantum dot for the entire range of the electron-phonon coupling constant are obtained using the single-mode squeezed-state variational approach.The variational approach we applied is based on two successive canonical transformations and using a displaced-oscillator type unitary transformation to deal with the bilinear terms which are usually neglected.In order to study the relationship between the ground-state energy and the average number of virtual phonons around the electron of a polaron in a parabolic quantum dot with the electron-LO-phonon coupling constant and the confinement length,numerical calculations are carried out in the electron-LO-phonon strong-and weak-coupling regions.
针对基于电力线载波通信(PLC,Power Line Communication)技术的LED路灯监控系统,基于蚁群算法(ACA,Ant Colony Algorithm)开发了一种适用于低压配电网的LED路灯组网寻址算法,并在目标函数、信息素更新规则、状态转移规则和搜索等方面做了优化改进。建立了路灯自动路由模型,并给出自动路由协议框架。通过该模型,可动态识别低压配电网信道质量,并根据信道质量变化,动态维护电力线载波通信网络路由,保证通信网络有效性。最后,通过信道仿真模型和现场试验验证了该方法的可行性和有效性。
Within the frame of the Pavlov–Firsov spin–phonon coupling model, we study the spin-flip assisted by the acoustical phonon scattering between the first-excited state and the ground state in quantum dots. We analyze the behaviors of the spin relaxation rates as a function of an external magnetic field and lateral radius of quantum dot. The different trends of the relaxation rates depending on the magnetic field and lateral radius are obtained, which may serve as a channel to distinguish the relaxation processes and thus control the spin state effectively.
研究了能量在100到300 ke V区间的低能宽幅电子束从真空引出到空气中的特性。利用EGS5程序模拟了电子束穿过不同厚度钛箔后,在空气中距离钛箔5～10 cm距离处的能量损失、束流损失和束流分布均匀性等。模拟结果显示,对于低能电子,钛箔厚度应该在10μm左右为宜,其透射率与能量直接相关,在距离钛箔5 cm的位置,电子束的分布不均匀度低于±2%,优于工业应用±10%的标准(特殊情况下要求为±5%),完全满足工业辐照要求。
