A novel structure for a charge pump circuit is proposed, in which the charge-pump （CP） current can adaptively regulated according to phase-locked loops （PLL） frequency synthesis demand. The current follow technolo...A novel structure for a charge pump circuit is proposed, in which the charge-pump （CP） current can adaptively regulated according to phase-locked loops （PLL） frequency synthesis demand. The current follow technology is used to make perfect current matching characteristics, and the two differential inverters are implanted to increase the speed of charge pump and decrease output spur due to theory of low voltage difference signal. Simulation results, with 1st silicon 0. 25μm 2. 5 V complementary metal-oxide-semiconductor （CMOS） mixed-signal process, show the good current matching characteristics regardless of the charge pump output voltages.展开更多
We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthi...We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.展开更多
We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per...We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.展开更多
Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of t...Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2（NM_1 =Cu or Al,NM_2 =Pt or Ta）,we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface（in contact with thin YIG）,either due to the magnetic proximity effect（MPE） or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect（ISHE）.The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on.展开更多
The adiabatic electron transport is theoretically studied in a zigzag graphene nanoribbon （ZGNR） junction with two time-dependent pumping electric fields. By modeling a ZGNR p-n junction and applying the Keldysh Gr...The adiabatic electron transport is theoretically studied in a zigzag graphene nanoribbon （ZGNR） junction with two time-dependent pumping electric fields. By modeling a ZGNR p-n junction and applying the Keldysh Green＇s function method, we find that a pumped charge current is flowing in the device at a zero external bias, which mainly comes from the photon-assisted tunneling process and the valley selection rule in an even-chain ZGNR junction. The pumped charge current and its ON and OFF states can be efficiently modulated by changing the system parameters such as the pumping frequency, the pumping phase difference, and the Fermi level. A ferromagnetic ZGNR device is also studied to generate a pure spin current and a fully polarized spin current due to the combined spin pump effect and the valley valve effect. Our finding might pave the way to manipulate the degree of freedom of electrons in a graphene-based electronic device.展开更多
Pumps with magnet systems constructed on permanent magnets and performed in two manners like two-disk type and the cylindrical rotor type are discussed.First,by way of example we consider the experimental study of dis...Pumps with magnet systems constructed on permanent magnets and performed in two manners like two-disk type and the cylindrical rotor type are discussed.First,by way of example we consider the experimental study of disk pump with straight channel;second,we analyse the results of numerical simulation of cylindrical pump in two cases,namely,of straight and U-bend forms of pump channels.At a high speed of pump rotation when induced magnetic field becomes essential in as against the applied field,i.e.when the skin-effect takes place,the pump characteristics are analyzed.Visualization of physical fields of the pumps is reported.展开更多
静止变频器(static frequency converter,SFC)是抽水蓄能电站大型同步机组启动过程的重要设备。在抽蓄机组启动的过程中,由于SFC机、网两侧电流频率不一致,使得基于工频相量的常规差动保护配置困难,且现有保护方案在速动性和可靠性上存...静止变频器(static frequency converter,SFC)是抽水蓄能电站大型同步机组启动过程的重要设备。在抽蓄机组启动的过程中,由于SFC机、网两侧电流频率不一致,使得基于工频相量的常规差动保护配置困难,且现有保护方案在速动性和可靠性上存在不足。为解决上述问题,提出了一种基于模型校核的SFC采样值差动保护原理。首先充分研究SFC的工作原理和控制策略,并基于电流采样值在时域内构建符合SFC工作原理的数学模型,然后采用模型校核的方法寻找故障前后差异并提出相应的保护判据。最后,在PSCAD/EMTDC中搭建抽蓄机组SFC启动的电磁暂态仿真模型,验证所提保护原理的有效性。仿真结果表明,所提保护原理不受SFC两侧不同频率的干扰,具有良好的选择性、速动性和可靠性。展开更多
为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以...为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以光伏分压注水泵为基础,通过分压压力缸对管网来水做功,实现高低压井能量转换;分析光伏分压注水泵的电流环、电压环,利用最优梯度的MPPT算法令光伏分压注水泵持续处于最大功率点状态下,当光伏分压注水泵运行功率产生变化时,调节电流环输出、控制主开关管占比、调节光伏分压注水泵的输出功率;通过实时监测和调整PWM脉冲宽度调制信号占空比,实现光伏分压注水泵闭环控制,由此提高水泵的能量转换效率。实验表明,该方法可以有效使水泵运行稳定性得以增强,并实现油气田管网注水量的合理有效控制,且有效提升油气田注水管注水效率。展开更多
文摘A novel structure for a charge pump circuit is proposed, in which the charge-pump （CP） current can adaptively regulated according to phase-locked loops （PLL） frequency synthesis demand. The current follow technology is used to make perfect current matching characteristics, and the two differential inverters are implanted to increase the speed of charge pump and decrease output spur due to theory of low voltage difference signal. Simulation results, with 1st silicon 0. 25μm 2. 5 V complementary metal-oxide-semiconductor （CMOS） mixed-signal process, show the good current matching characteristics regardless of the charge pump output voltages.
文摘We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.
基金supported by the State Key Program for Basic Research of China(Grant Nos.2015CB921202,2014CB921103,2011CB922103,and 2010CB923400)the National Natural Science Foundation of China(Grant Nos.11225420,11174125,and 91021003)the Priority Academic Program Development of Higher Education Institutions of Jiangsu Province,China
文摘We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921502 and 2013CB922303)the National Natural Science Foundation of China(Grant Nos.11474184,116627805,and 11504203)+2 种基金the 111 Project(Grant No.B13029)Zhang Yin and Wang Xiangrong were supported by the Hong Kong RGC Grants(Grant Nos.16301816 and 605413)Wu Yong and Jiang Yong were supported by the National Natural Science Foundation of China(Grant No.51501007)
文摘Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2（NM_1 =Cu or Al,NM_2 =Pt or Ta）,we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface（in contact with thin YIG）,either due to the magnetic proximity effect（MPE） or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect（ISHE）.The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on.
基金supported by the National Natural Science Foundation of China(Grant No.110704033)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK2010416)the Natural Science Foundation for Colleges and Universities in Jiangsu Province,China(Grant No.13KJB140005)
文摘The adiabatic electron transport is theoretically studied in a zigzag graphene nanoribbon （ZGNR） junction with two time-dependent pumping electric fields. By modeling a ZGNR p-n junction and applying the Keldysh Green＇s function method, we find that a pumped charge current is flowing in the device at a zero external bias, which mainly comes from the photon-assisted tunneling process and the valley selection rule in an even-chain ZGNR junction. The pumped charge current and its ON and OFF states can be efficiently modulated by changing the system parameters such as the pumping frequency, the pumping phase difference, and the Fermi level. A ferromagnetic ZGNR device is also studied to generate a pure spin current and a fully polarized spin current due to the combined spin pump effect and the valley valve effect. Our finding might pave the way to manipulate the degree of freedom of electrons in a graphene-based electronic device.
基金Sponsored by German Research Foundation (Deutsche Forschungsgemeinschaft) in the Framework of the Research Training Group (Graduiertenkolleg) "Lorentz Force Velocimetry and Lorentz Force Eddy Current Testing"
文摘Pumps with magnet systems constructed on permanent magnets and performed in two manners like two-disk type and the cylindrical rotor type are discussed.First,by way of example we consider the experimental study of disk pump with straight channel;second,we analyse the results of numerical simulation of cylindrical pump in two cases,namely,of straight and U-bend forms of pump channels.At a high speed of pump rotation when induced magnetic field becomes essential in as against the applied field,i.e.when the skin-effect takes place,the pump characteristics are analyzed.Visualization of physical fields of the pumps is reported.
文摘静止变频器(static frequency converter,SFC)是抽水蓄能电站大型同步机组启动过程的重要设备。在抽蓄机组启动的过程中,由于SFC机、网两侧电流频率不一致,使得基于工频相量的常规差动保护配置困难,且现有保护方案在速动性和可靠性上存在不足。为解决上述问题,提出了一种基于模型校核的SFC采样值差动保护原理。首先充分研究SFC的工作原理和控制策略,并基于电流采样值在时域内构建符合SFC工作原理的数学模型,然后采用模型校核的方法寻找故障前后差异并提出相应的保护判据。最后,在PSCAD/EMTDC中搭建抽蓄机组SFC启动的电磁暂态仿真模型,验证所提保护原理的有效性。仿真结果表明,所提保护原理不受SFC两侧不同频率的干扰,具有良好的选择性、速动性和可靠性。
文摘为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以光伏分压注水泵为基础,通过分压压力缸对管网来水做功,实现高低压井能量转换;分析光伏分压注水泵的电流环、电压环,利用最优梯度的MPPT算法令光伏分压注水泵持续处于最大功率点状态下,当光伏分压注水泵运行功率产生变化时,调节电流环输出、控制主开关管占比、调节光伏分压注水泵的输出功率;通过实时监测和调整PWM脉冲宽度调制信号占空比,实现光伏分压注水泵闭环控制,由此提高水泵的能量转换效率。实验表明,该方法可以有效使水泵运行稳定性得以增强,并实现油气田管网注水量的合理有效控制,且有效提升油气田注水管注水效率。
