Control of Sudden Death of Entanglement by Transient Effects

We investigate the properties of entanglement between an isolated atom and a Jaynes-Cummings atom in the presence of transient effects. These effects are due to the modulation of the atom-field coupling whose explicit time-dependence is considered for the case of the linear sweep. We show that the sudden death of entanglement can be controlled by the transient effects. These effects can suppress the sudden death of entanglement in time.

TRANSIENT EFFECT OF A BOGER FLUID FLOWING AROUND A CONFINED CYLINDER

This paper is concerned with the numerical simulation of the transient effect of an inertialess Boger flow past a confined circular cylinder and the comparison of predictions with particle image velocimetry (PIV) measurements given by Shiang et al.. Dynamic simulation based on the Oldroyd-B constitutive model was carried out using a Lagrangian-Eulerian algorithm. The evolution of velocity field was obtained for the flow at two Deborah (De) numbers, i.e. De = 1.2 and 3.0. At low De, the flow reached steady state rapidly, and showed a symmetric flow regime. However, at high De, the time required to reach steady flow behind the cylinder increased significantly, and the distribution of the velocity field appears to be asymmetric with respect to the stagnation line. Fairly good agreement between the numerical results and the experimental observations is reported. It can be concluded that both the experimental measurements and the present simulations indicate that the elasticity of the polymeric flow strongly affect the flow regime of viscoelastic flow around a confined cylinder.

Analytical solution for a circular roadway considering the transient effect of excavation unloading

The rocks surrounding a roadway exhibit some special and complex phenomena with increasing depth of excavation in underground engineering.Quasi-static analysis cannot adequately explain these engineering problems.The computational model of a circular roadway considering the transient effect of excavation unloading is established for these problems.The time factor makes the solution of the problem difficult.Thus,the computational model is divided into a dynamic model and a static model.The Laplace integral transform and inverse transform are performed to solve the dynamic model and elasticity theory is used to analyze the static model.The results from an example show that circumferential stress increases and radial stress decreases with time.The stress difference becomes large gradually in this progress.The displacement increases with unloading time and decreases with the radial depth of surrounding rocks.It can be seen that the development trend of unloading and displacement is similar by comparing their rates.Finally,the results of ANSYS are used to verify the analytical solution.The contrast indicates that the laws of the two methods are basically in agreement.Thus,the analysis can provide a reference for further study.

Analyzing the transient effects of 60Co gamma rays in a CIS by Monte Carlo method

The objective of this work is to analyze the transient effects of ^60Co gamma rays in the CMOS image sensor (CIS) using the Monte Carlo method, based on Geant4. The track, energy spectrum, and angle of produced electrons when gamma rays traversed a silicon or silicon dioxide cube were calculated. A simplified model of a 500 × 500 CIS array was established, and the transient effects of gamma rays in the CIS were simulated. The raw images were captured when the CIS was irradiated by gamma rays. The experimental results were compared with the simulation results. The characteristics of the typical events induced by transient effects were analyzed.

Effect of the Transient Response in Si/Ge Parallelizing PN Junction

There are some new results about photovoltaic transient response in the new effect. We suggest a theoretical model to explain the effect reasonably. The theoretical calculation results agree with that in experiments.

Multi-Electron Effects in Attosecond Transient Absorption of CO Molecules

Using the fully propagated time-dependent Hartree–Fock method, we identify that both the dynamic core polarization and multiorbital contributions are important in the attosecond transient absorption of CO molecules.The dynamics of core electrons effectively modifies the behaviors of electrons in the highest occupied molecular orbital, resulting in the modulation of intensity and position of the absorption peaks. Depending on the alignment angles, different inner orbitals are identified to contribute, and even dominate the total absorption spectra. As a result, multi-electron fingerprints are encoded in the absorption spectra, which shed light on future applications of attosecond transient absorption in complex systems.

Simulation of continuous terahertz wave transient state thermal effects on static water

We report a numerical simulation of continuous terahertz beam induced transient thermal effects on static water. The terahertz wave used in this paper has a Gaussian beam profile. Based on the transient heat conduction equation, the finite element method （FEM） is utilized to calculate the temperature distribution. The simulation results show the dynamic process of temperature change in water during terahertz irradiation. After about 300 s, the temperature reaches a steady state with a water layer thickness of 5 mm and a beam radius of 0.25 mm. The highest temperature increase is 7 K/mW approximately. This work motivates further study on the interaction between terahertz wave and bio-tissue, which has a high water content.

NUMERICAL MODEL OF THERMAL TRANSIENT EFFECT IN FIBER OPTIC GYRO

The sensitivity of the interferometric fiber optic gyro in the presence of time varying thermal gradients plays a key role in its performance. It is well known that this sensitivity is due to the difference of index changes between the points symmetrical with respect to the middle of the coil. In order to reduce this sensitivity, different winding patterns, such as quadrupolar winding, were introduced to keep the thermal environment of the symmetrical points. In this paper, a numerical model of the transient temperature distribution in the gyro was established. The temperature gradient of the coil was solved in conjugation with the nature convection heat transfer in the aperture between the coil and the case. Effects of the winding pattern and the design of its case were investigated to optimize the design of the interferometric fiber optic gyro.

New insight into the parasitic bipolar amplification effect in single event transient production

In this paper, a new method is proposed to study the mechanism of charge collection in single event transient （SET） production in 90 nm bulk complementary metal oxide semiconductor （CMOS） technology. We find that different from the case in the pMOSFET, the parasitic bipolar amplification effect （bipolar effect） in the balanced inverter does not exist in the nMOSFET after the ion striking. The influence of the suhstrate process on the bipolar effect is also studied in the pMOSFET. We find that the bipolar effect can be effectively mitigated by a buried deep P＋-well layer and can be removed by a buried SO2 layer.

Transient growth in Poiseuille-Rayleigh-Bénard flows of binary fluids with Soret effect

The transient growth due to non-normMity is investigated for the Poiseuille- Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = -0.1, it is found that a large transient growth can be obtained by the non-normal interaction of the two least-stable-modes, i.e., the upstream and downstream modes, which determine the linear critical boundary curves for small Reynolds numbers. The transient growth is so strong that the optimal energy amplification factor G（t） is up to 10^2 - 10^3. While for positive separation factors such as ψ = 0.1, the transient growth is weak with the order O（I） of the amplification factor, which can even be computed by the least-stable-mode. However, for both cases, the least-stable-mode can govern the long-term behavior of the amplification factor for large time. The results also show that large Reynolds numbers have stabilization effects for the maximum amplification within moderate wave number regions. Meanwhile, much small negative or large positive separation factors and large Rayleigh numbers can enlarge the maximum transient growth of the pure streamwise disturbance with the wavenumber α= 3.14. Moreover, the initial and evolutionary two-dimensional spatial patterns of the large transient growth for the pure streamwise disturbance are exhibited with a plot of the velocity vector, spanwise vorticity, temperature, and concentration field. The initial three-layer cell vorticity struc- ture is revealed. When the amplification factor reaches the maximum Gmax, it develops into one cell structure with large amplification for the vorticity strength.

应急供水多级泵意外停机水力过渡过程瞬态特性

应急供水多级泵的意外停机会引起系统性能参数的剧烈变化,严重威胁供水安全。为了探究多级泵停机水力过渡过程内部流场的瞬态效应,该研究建立了基于叶轮转动平衡方程的泵停机过程转速预测方法,数值模拟分析了意外停机过程中多级泵内部流动特性。研究结果表明:在意外停机过程中,多级泵分别经历水泵工况、制动工况、反转工况以及飞逸工况4个阶段,转速呈现先减小至0后沿负方向增大的趋势,最后稳定在飞逸转速-4210 r/min附近;流量呈现先减小至0后沿负方向增大的趋势,然后再沿正方向增大,最终稳定在飞逸流量-14.32 kg/s附近;扭矩呈现先减小再增加,最后减小并稳定在零点附近。泵内流量和转速的大小、方向不断变化引起叶轮流道内流体的流动分离和回流,伴随着涡的形成、发展和破碎等时空演变;熵产值的变化与多级泵内不稳定流动密切相关,由湍流耗散所带来的损失起主导作用,在达到飞逸工况后湍流耗散熵产占比约65.2%,能量损失主要发生在叶轮流道内,且制动工况中内流场的损失较大;多级泵首级流道内监测点压力变化最为剧烈,各级监测点的压力脉动系数波动幅值随着级数的增加呈减小趋势;压力脉动振幅主导频率与多级泵转速呈现正相关关系,主导分量对应于叶轮流道的叶片通过频率,且沿着流体流动方向压力脉动频率振幅逐渐增大,压力脉动的频率特性可以反应出意外停机过程中流量的不稳定变化。研究成果可为应急供水系统安全稳定运行提供理论指导。

Experimental verification of the parasitic bipolar amplification effect in PMOS single event transients

The contribution of parasitic bipolar amplification to SETs is experimentally verified using two P-hit target chains in the normal layout and in the special layout. For PMOSs in the normal layout, the single-event charge collection is composed of diffusion, drift, and the parasitic bipolar effect, while for PMOSs in the special layout, the parasitic bipolar junction transistor cannot turn on. Heavy ion experimental results show that PMOSs without parasitic bipolar amplification have a 21.4% decrease in the average SET pulse width and roughly a 40.2% reduction in the SET cross-section.

Transient simulation and analysis of current collapse due to trapping effects in AlGaN/GaN high-electron-mobility transistor

In this paper, two-dimensional （2D） transient simulations of an A1GaN/GaN high-electron-mobility transistor （HEMT） are carded out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current-voltage （l-V） curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I-V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of A1GaN/GaN HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of GaN-based devices.

SOI晶体管和电路的瞬时电离辐射效应研究

基于全介质隔离的绝缘硅(Silicon-on-insulator,SOI)器件与体硅器件的瞬时电离辐射效应存在差异,采用1 064 nm/12 ns激光装置开展了三种SOI晶体管的激光辐照试验,测试了不同激光能量下的晶体管光电流;采用脉冲γ射线辐射源开展了SOI集成电路的瞬时γ剂量率辐射试验,测试了不同剂量率条件下的电路功能、电参数和触发器链状态。研究表明:在相同激光能量条件和相同特征尺寸条件下,SOI晶体管的光电流峰值约为体硅晶体管的3.5%;SOI集成电路在1.0×10^(9)~4.2×10^(11) rad(Si)·s^(-1)的试验剂量率范围内无闭锁效应,但存在显著的翻转效应,表现为功能短暂中断、电流和电压波动以及大量触发器状态错误。翻转效应的主要原因包括晶体管本身的翻转和印刷电路板(Printed Circuit Board,PCB)板级电路的电压波动。

汽轮发电机转子绕组匝间短路故障恶化的影响因素研究

转子绕组匝间短路是大型同步发电机的常见故障,在发电机的电气故障中占据了较高的比例,也是影响机组安全运行的主要原因之一。本文针对转子绕组匝间短路伴随的局部过热问题,分别研究了短路点过渡电阻、短路点电流集束效应以及短路点的反复通断过程对其的影响。以一台300MW汽轮发电机为例,仿真获取了短路回路电流和功率损耗、短路点附近励磁电流密度以及被短路回路的暂态电压规律。本研究为确定转子绕组匝间短路故障的过热现象原因奠定了理论基础,也为进一步研究故障演化过程提供了分析思路。

不同能量质子辐照CMOS图像传感器的单粒子瞬态效应研究

针对空间环境宽能谱质子辐射导致的CMOS图像传感器单粒子效应问题,开展了不同能量质子辐照试验,研究了质子辐照导致CMOS图像传感器单粒子效应的异常现象、图像特征及参数性能变化规律。试验表明,质子辐照主要导致CMOS图像传感器出现明显的单粒子瞬态(single event transient,SET)效应现象,包括SET亮斑和亮线。通过对比不同条件下的试验结果,分析了质子能量、积分时间等变化对SET亮斑覆盖像素情况、信号水平的影响规律,并结合TCAD仿真工具,分析了SET亮斑的产生机制。研究结果表明:SET亮斑灰度水平和覆盖像素数目均随辐照质子能量增加而增大;SET亮斑覆盖像素最大灰度值、平均灰度值随CMOS图像传感器积分时间增加而增大,通过调节CMOS图像传感器的积分时间,可以明显改变SET亮斑的特征和器件成像性能;从TCAD软件仿真的微观物理过程获得了SET亮斑随积分时间变化的机制,支持了对试验结果的分析和判断。研究结果可为CMOS图像传感器空间辐射效应评估、抗辐射加固提供试验和理论参考。

考虑Gauss移动热源瞬态效应的传热结构拓扑优化

针对热源位置随时间发生变化的结构热传导问题,考虑Gauss移动热源进行瞬态热传导拓扑优化设计.分别以整个时间历程内传热结构散热弱度最小化与区域温度最大值最小化为设计目标,体积分数为约束条件,采用伴随变量法推导目标函数与约束条件的敏度信息,借助移动渐进线法更新设计变量,研究了不同Gauss热源移动路径与移动速度对拓扑优化结果的影响.结果表明,瞬态拓扑结构相较于稳态结果具有明显时变性,同时最佳传热构型受到热源加热时间和移动速度及路径的多重影响.

基于分数阶传输线模型的轨道电路暂态分析

为了准确分析暂态信号对ZPW-2000A型轨道电路的影响,考虑传输线中由集肤效应引起的频变损耗问题,建立轨道电路分数阶多导体传输线(Multi-conductor Transmission Line,MTL)模型,针对ZPW-2000A轨道电路高频损耗下暂态响应分析,提出在时域内对轨道电路接收端电压的求解方法.基于传输线理论建立轨道电路传输线系统模型,根据得到的模型建立分数阶传输线方程并对其进行求解.首先,在空间域上利用紧凑有限差分法(Compact Finite Difference Method,CFD)将轨道电路分数阶传输线模型的偏微分方程组离散为常微分方程组;其次,利用G-L分数阶定义将以上方程组转化为整数阶常微分方程组;最后,利用精细积分与递归卷积相结合的方法,得到传输线上每点的电压与电流响应.在双指数信号激励下,通过与状态变量法对比验证了该方法的准确性,两种求解方法的误差在7%以内,且本文方法耗时较短.分析了不同暂态信号输入下轨面过电压变化规律,发现信号频率越大,轨面过电压幅值越小;道床电阻越大,轨面过电压幅值越大且信号从衰减到稳定的时间越长.本文方法可以准确、高效地分析高频损耗下ZPW-2000A型轨道电路暂态响应.

电化学储能参与电网暂态功角稳定控制研究

针对电网传统紧急控制资源的日益匮乏,利用电化学储能功率控制的快速性与双向控制能力,研究将其应用于电网暂态功角稳定控制。首先推导了计及电化学储能的双机等值模型,基于扩展等面积定则分析了储能改善电网暂态稳定裕度的原理。其次,提出了一种考虑设备保护与系统保护动作时序差异的储能电站有效工作时长计算方法,改善了紧急控制储能的工作效率。提出了计及储能的基于性能代价比多类措施协调控制策略制定方法,兼顾紧急控制的安全性与经济性,为电网暂态紧急控制提供在线辅助决策支撑。进一步提出了储能电站全景监控系统架构,为实现储能电站与电网紧急控制系统的交互提供了技术实践思路。最后西北电网实际算例验证了所提方法的有效性与合理性。研究结论可为规模化储能与高比例新能源电网第二道防线的扩展与建设提供理论参考。

SiC MOSFET开关瞬态解析建模综述

在评估和优化半导体器件开关瞬态特性领域,解析模型因具有简单、直观、应用便捷等优点得到广泛研究。相较同等功率等级的硅基功率器件,碳化硅(silicon carbide,SiC)金属氧化物半导体场效应晶体管(metal-oxide-semiconductor field effect transistor,MOSFET)可以应用于更高开关速度,其开关瞬态特性更为复杂,开关瞬态解析建模也更加困难。该文总结现有的针对SiC MOSFET与二极管换流对的开关瞬态解析建模方法,在建模过程中依次引入各种简化假设,按照简化程度由低到高的顺序,梳理解析建模的逐步简化过程。通过对比,评估各模型的优缺点以及适用场合,对其中准确性、实用性都较强的分段线性模型进行详细介绍;之后,对开关瞬态建模中关键参数的建模方法进行总结与评价;最后,指出现有SiC MOSFET开关瞬态解析模型中存在的问题,并对其未来发展给出建议。