Resonant Activation Induced by Four-Value Noise

The phenomenon of the resonant activation （RA） of a particle over a fluctuating potential barrier with a four-value noise is investigated. It is shown that the mean first passage time （MFPT） displays six minima as the function of the transition rates γ1, γ2, γ3, γ4, γ5, and 76 of the four-value noise, respectively. In addition, the effect of other parameters of the system, such as the noise strength D of the additive Gaussian white noise and the parameter value a, b, c, and d of the four-value noise, on the RAs is also investigated.     

The Application of Superconducting Tunnel Junction Detectors to Astronomy

Detectors based on the superconducting-insulating-superconducting (SIS) junction long ago surpassed Schottky-diode semiconductor detectors as the most sensitive heterodyne mixers in the millimeter and submillimeter (far-infrared) wavelength range. Other novel superconducting device configurations have been applied as direct detectors. Though still in the early stages of development, and yet to find widespread application, they have demonstrated advantages over traditional semiconductor detectors in specialized situations. Exciting progress has been made in recent years in developing the superconducting tunnel junctions (STJ) as a photon detector for optical and near-optical wavelengths, where silicon CCD's are currently dominant. I examine some of the areas in which the properties of STJ detectors may best match the instrument capabilities that astronomical observations require, and discuss the implications of the intrinsic spectral resolution of the STJ. This capability will enable a significant increase in observing efficiency, once the technology matures, that should justify increased complexity of cryogenic systems, particularly for instruments to be used on the next generation of large ground-based telescopes.     

全铌超导Josephson结的EWB仿真模型

通过超低温实验直接测量了制备的全铌Josephson结的电压源驱动RCSJ模型的I-V特性曲线。建立了Josephson结在电路仿真软件EWB中的模型,极大的方便了Josephson结及相关电路的仿真研究。利用这一新模型对Josephson结的基本特性进行了较为系统的研究,包括RSJ模型和RCSJ模型的直流驱动I-V特性曲线。     

电力故障运行下磁偏置超导限流器超导限流单元的电-热特性分析与验证

本文的磁偏置高温超导故障限流器(SFCL)是一种新型超导限流器,在系统出现短路故障时,发生失超现象,产生高阻抗限制短路电流,达到一定时间后断开超导单元,再由双分裂电抗器二次限流.当短路电流消失后,自动快速恢复到无阻特性,然后重新合闸投入系统运行.在SFCL并网运行前,要对并网运行中出现相间短路等故障的暂态运行特性进行分析,了解并网运行时的状况.本文利用Matlab/Simulink构建了SFCL的仿真分析模型,包含超导限流单元的等效电路模型和热模型.该模型被接入一个由Matlab/Simulink构建的10 kV电力系统模型中,用来仿真SFCL的并网运行特性.仿真结果表明了SFCL在并网运行中的效果,以及相间短路故障下失超电阻、通过电流和超导限流单元温度的变化.同时,在中国国网辽宁电力虎石台对SFCL进行了并网运行试验,得到了相间短路故障下的暂态运行特性和失超恢复时间.本文的仿真分析和试验结果,证明了该SFCL样机具备10 kV并网能力,以及快速响应、逐级限流和快速恢复能力     

Theoretical Investigation of Coherent Enhancement for Resonant Two-Photon Transitions

We theoretically investigate the coherent enhancement of resonant two-photon transitions （TPT） in a three-level atomic system. The TPT can be coherently enhanced by modulating spectral amplitude due to eliminating the destructive interference, though partial laser energy losses. Maximal enhancement of TPT can be achieved by modulating spectral phase due to establishing completely constructive interference. Our research provides a theoretical basis for experimental investigation and appears to have potential application on coherent control in the complicated quantum system.     

Entropic Resonant Activation and StochasticResonance Driven by Non-Gaussian Noise

The transition rate and stochastic resonance (SR) of a Brownian particle moving in a confined system under the presence of entropic barriers are investigated when the system is driven by non-Gaussian noise. The explicit expressions of the transition rate and the spectral power amplification (SPA) are obtained, respectively. The effects of the parameter q indicating the departure from the Gaussian noise and the correlation timeτ of the non-Gaussian noise on the transition rate and the SPA are discussed. Research results show that: (i) The transition rate as a function of the noise strength exhibits a maximum. This maximum for transition rate identifies the phenomenon of entropic resonant activation (ERA), the parameter q and the noise correlation timeτ weaken the ERA of the system; (ii) The curves of SPA appear a transition from one peak to double-peak, and then to one peak again as the noise correlation timeτ of non-Gaussian noise increases.     

一种用于电阻型超导限流器新型结构的第二代高温超导带材

电阻型超导故障限流器(R-SFCL)结构简单、限流效果好等优点,在电力系统中具有广阔的应用前景.超导故障限流器的发展经历了实验级、配电级、输电级样机研制等阶段.随着超导限流器容量不断攀升,由于单根材料性能的限制,不可避免在系统中会采用大量的串并联方式.带材的临界电流和耐瞬态冲击能力决定着一个限流器在额定电流通流下和过流冲击下的并联支路数.带材的失超电阻决定着一个限流器在一定故障电流抑制率下的串联支路数.通过分析目前REBCO超导带材的参数和典型的限流器设计参数,发现了超导带材电流和耐过流冲击相差近3倍的关系.本文提出了一种宽的不锈钢封装窄的超导带结构,目的是让不锈钢的宽度与超导带材的宽度保持在3倍的关系,以贴合部分限流器的需求.经过测试,结果显示低成本新结构的超导带材瓶颈性能保有原结构带材的91.3%,成本下降一半,这对未来电阻型超导限流器成本的降低来说是一个非常好的选项.     

Transport of Electron Pairs in a Superconducting Junction Device: Underdamped Case

Transport of electron pairs in a superconducting junction device in the underdamped case is investigated. It is shown that the capacitance of the junctions can slow the movement of the electron pairs and reduce the net voltage. It is also shown that, for the underdamped case and the overdamped case, the movement of the electron pairs in this superconducting junctions device has some similar features. By controlling the correlation between the additive and multiplicative noise, the flux can be reversed. In addition, if the additive noise strength (or the temperature T) is large enough, a reversal can also be induced.     

Technique for Calculating the Critical Current of Inhomogeneous Superconducting Films

Physics of the Solid State - A method for calculating the critical current of an inhomogeneous superconducting film (plate) in different external magnetic fields has been proposed. The...     

制冷机冷却型超导磁体系统用电流源保护控制系统的实现

随着超导技术和制冷技术的相互促进和共同发展 ,制冷机直接冷却的超导磁体系统已从概念设计走向实际应用。电流源保护控制系统是超导磁体系统的重要组成部分 ,其主要作用是为超导磁体系统提供稳定电流并实现可靠的保护控制。文中首先分析了制冷机冷却型超导磁体系统用电流源的工作过程及其特殊的控制和保护要求 ,然后设计了一个以单片机为核心的自动保护控制系统。     

用于限流器的Bi-2212超导筒的研制

采用部分熔化法在流氧气氛的旋转炉中 ,以 Ag箔为衬 ,成功制得直径 60 mm的 Bi- 2 2 1 2超导圆筒。加热初始粉到部分熔融状态 ,然后再冷却到 855℃以形成超导相 ,在富 N2 气氛下退火 ,并且从 70 0℃开始在纯 N2 气氛中冷却 ,这种工艺可以得到较好机械强度和外型的筒。XRD图象表明 Bi- 2 2 1 2筒中主要相为 Bi- 2 2 1 2超导相。 Bi- 2 2 1 2筒的临界电流密度为 1 0 0 Acm-2 ,Ic约为1 0 A     

Absorption Enhancement of Silicon Solar Cell in a Positive-Intrinsic-Negative Junction

Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative(PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory.We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.     

Resonant Charge Current in a Rashba Ring Induced by Spin-Dependent Potential

A on,dimensional ring subject to Rashba spin-orbit coupling is investigated. When it is attached to a lead with spin-dependent chemical potential, there will be charge current in the ring. The charge current response is resonantly maximized when the Fermi energy of the lead is equal to any energy level of the 1D ring. And if two probes are attached to the ring, the electric voltage between them creates sawtooth-like wave, which indicates the direction of the charge current. A ferromagnetic lead can also induce persistent charge current, which can be detected by magnetization intensity measurement.     

磁屏蔽感应型超导故障限流器的仿真研究

介绍了磁屏蔽感应型超导故障限流器 (SCFCL)的结构 ,分析了它的工作原理 ,并对一样机进行了仿真实验 ,获得了与该样机的实验近乎一致的结果。并通过仿真 ,研究了相关参数对限流效果的影响 ,从而为设计该 SCFCL提供了新的方法。     

超导故障限流器的数学模型研究

文中总结了几种超导故障限流器的模型。在数学模型的基础上 ,阐述了超导材料的温升、失超传播速度和临界电流密度对超导故障限流器性能的影响     

Influence of Intrinsic Decoherence on Entanglement of Superconducting Charge Qubit in a Resonant Cavity

Taking the intrinsic decoherence effect into account, we investigate the entanglement dynamics of a superconducting charge qubit in a single-mode optical cavity. Concurrence, as the measure of entanglement of the coupled field-junction system, is calculated. In comparison, we also consider the entanglement of the system by using the entanglement parameter based on the ratio between mutual entropy and partial Von-Neumann entropy to investigate how the intrinsic decoherence affects the entanglement of the coupling system. Our results show that the evolution of the entanglement parameter has the behaviour similar to the concurrence and it is thus the well measure of entanglement for the mixed state in such a coupling system.     

Analysis of Permissible Current Loads of Resistive Current Leads of Superconducting Magnetic Systems

Physics of Atomic Nuclei - This article discusses the issue of selection of material for resistive current leads of superconducting magnets. A wide range of their working modes has been considered....     

采用半导体激光器自身pn结特性测温的 半导体激光器恒温控制

温度对半导体激光器的发射波长有很大的影响,而很多应用都要求半导体激光器的发射波长是稳定的。针对使用测温元件作为温度传感器进行半导体激光器恒温控制中存在的温度误差,提出了以半导体激光器自身pn结作为温度检测元件进行半导体激光器恒温控制的方法,设计了半导体制冷器的驱动电路。该方法利用pn结的温度敏感特性,首先通过实际测量标定pn结的温度与其两端压降的对应关系,然后通过测量压降得出相应的实际温度。实验结果表明,采用该方法消除了使用温度传感器进行半导体激光器恒温控制中温度梯度造成的恒温误差,提高了测量速度,显著减小了超调量,消除了静差和波动。