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We study the efficiency of modulated external electric pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction. 相似文献
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85.
晶体表面的扩散和缺陷对晶体振动模式的影响是表面物理学研究的一个重要和基本的课题.晶格振动的频率对应于系统的能带.由于晶格中原子的振动不是孤立的,并且晶格具有周期性,所以在晶体中形成格波.格波代表晶体中所有原子都参与的频率相同的振动,又常称为一种振动模.本文讨论在表面吸附位势系数β_0与晶体内部原子的周期位势系数β不同的情况下,晶体表面吸附一个质量为m_0(与晶格原子质量m不同)的原子以后晶格的振动模.采用不变本征算符方法,严格地导出此振动模为ω=((2β(1-coshα))/(hm))~(1/2),其中α=ln[-(mβ_0+m_0(-2β+β_0)+(β_0)~(1/2)((-4mm_0β+(m+m_0)~2β_0))~(1/2)/2m_0β].此结果表明,ω不但取决于吸附位势与吸附原子的质量,也与晶格原子的质量与内位势有关. 相似文献
86.
《Particuology》2015
The influence of Na2SO4 on the formation of ZnO whiskers was investigated in this paper. ZnO whiskers with aspect ratios of up to 50 were synthesized by dissolving ɛ-Zn(OH)2 precursor in NaOH/Na2SO4 solution at room temperature, followed by aging of the resulting solution at 140 °C for 6 h. Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy analyses revealed that SO42− ions were primarily adsorbed on the (1 0 0) plane of the ZnO whiskers via an outer-sphere complex configuration (OH···O), thereby promoting the one-dimensional growth of ZnO whiskers along the c-axis. 相似文献
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88.
发展高效绿色电炉冶炼技术是淘汰落后产能、钢铁产业调整升级的重要举措。电弧炉作为核心生产设备,防止其生产运行中无功冲击造成的电压跌落至关重要。而目前单一的有源、无源补偿方式无法同时满足电弧炉负荷日益增长的大容量且快速响应的无功补偿需求。研究了静止无功补偿器(SVC)和静止无功发射器(SVG)相结合的混联补偿方式,分析了SVC在分相不平衡大容量补偿及SVG在无功快速响应方面中的特性,并针对某钢厂电弧炉工作运行情况,计算其无功需求,充分利用其原有的SVC装置,设计混联SVG方案来抵消剩余无功缺口,使用PSCAD/EMTDC进行了联合应用仿真,证实其理论有效性。 相似文献
89.
有源电力滤波器(APF)是电力系统中实现电能质量管理的关键设备,谐波检测作为APF的关键技术之一,检测的精度和响应速度直接决定了APF的整体性能。介绍了传统的基于瞬时无功功率理论的ip-iq谐波电流检测算法; 针对其检测精度受锁相环输出相位误差影响,以及低通滤波器的存在限制了谐波检测系统的响应速度,提出了应用锁频环技术,产生与电网电压同频的单位正余弦信号的一种改进谐波检测算法; 并提出采用滑动平均滤波器(MAF)代替低通滤波器提高其响应速度以及改善谐波检测精度; 对改进的检测算法进行了理论分析,通过MATLAB进行仿真研究,理论分析和仿真结果都证明了该方法的有效性。 相似文献
90.
J. Chen K. Ida M. Yoshinuma I. Murakami T. Kobayashi M.Y. Ye B. Lyu 《Physics letters. A》2019,383(12):1293-1299
Charge exchange spectroscopy (CXS) is widely used to measure plasma flow velocity. Accurate measurement is heavily affected by energy dependent cross section between neutral atoms and impurity ions. One symmetric layout of poloidal CXS is applied on Large Helical Device. Correction velocity due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout. A linear relationship between correction velocity and ion temperature is observed. Abundant discharges with wide plasma conditions are investigated and the ratio of correction velocity to ion temperature with the same beam energy shows the normal distribution. The impact of beam energy on the ratio of correction velocity to ion temperature of the carbon system and the hydrogen system is discovered based upon the statistics. Effective emission coefficient (Q) from Atomic Data and Analysis Structure (ADAS) is utilized to study the dependence of correction velocity on Q. The relationship in which the ratio of correction velocity to ion temperature increases linearly with the increasing normalized effective emission coefficient ((1/Q)dQ/dv) is observed. Experimental (1/Q)dQ/dv is obtained according to this observation, and comparison with different fractions of n?=?2 excited state is also discussed. The influence of different receivers (carbon and hydrogen) is also presented. The experimental (1/Q)dQ/dv from the carbon system decreases with beam energy decreasing when beam energy is less than 30 keV/amu. This tendency of (1/Q)dQ/dv at low beam energy indicates the existence of the contribution of n?=?2 excited state donors to the cross section. 相似文献