Atomistic Simulation of Carbon Nanotube Field-Effect Transistors Using Non-Equilibrium Green’s Function Formalism

Carbon Nanotube (CNT) Electronics attracts much attention for both basic and applied research. We first review a previously developed atomistic simulator for ballistic carbon nanotube transistors [1]. A recent work shows that our modeling of electrostatics, quantum transport, and contacts is sufficient to describe experiment [2]. A self-consistent atomistic simulation for a CNTFET imposes significant computational challenges. In this paper, we show how to efficiently implement the atomistic simulation by using computational techniques for computing Green’s function, solving 3D Poisson equation, running parallel simulation, and improving convergence. A phenomenological model of metal/CNT contacts suitable for routine device simulation is also discussed in detail.     

Operational Analysis of a Quantum Dot Optically Gated Field-Effect Transistor as a Single-Photon Detector

We report on the operation of a novel single-photon detector, where a layer of self-assembled quantum dots (QDs) is used as an optically addressable floating gate in a GaAs/Al_0.2Ga_0.8As delta-doped field-effect transistor. Photogenerated holes charge the QDs, and subsequently, change the amount of current flowing through the channel by screening the internal gate field. The photoconductive gain associated with this process makes the structure extremely sensitive to light of the appropriate wavelength. We investigate the charge storage and resulting persistent photoconductivity by performing time-resolved measurements of the channel current and of the photoluminescence emitted from the QDs under laser illumination. In addition, we characterize the response of the detector, and investigate sources of photogenerated signals by using the Poisson statistics of laser light. The device exhibits time-gated, single-shot, single-photon sensitivity at a temperature of 4 K. It also exhibits a linear response, and detects photons absorbed in its dedicated absorption layer with an internal quantum efficiency (IQE) of up to (68 plusmn18)%. Given the noise of the detection system, the device is shown to operate with an IQE of (53 plusmn 11)% and dark counts of 0.003 counts per shot for a particular discriminator level.     

一种新型感应过电压数字仿真软件的开发

研究开发了一种输电线路杆塔雷电感应过电压数字仿真软件,该软件可用于计算雷击杆塔时感应过电压的幅值及波形,使得在防雷计算中,感应分量可以简单、合理地与注入分量进行波形叠加,进而求得更为准确的雷电过电压。改进了目前直接将两者的峰值电压进行叠加的方法。分别采用CoorayRubinatein方程计算得到的结果和工程实测结果对本仿真软件进行了验证,最终证明本仿真软件所得结果与实测数据具有很好的吻合度。     

功能化掺杂对交联环氧树脂/碳纳米管复合材料热力学性能影响的分子动力学模拟

为探究不同功能化碳纳米管掺杂对环氧树脂/碳纳米管复合材料热力学性能的影响,基于分子动力学模拟方法,建立掺杂功能化碳纳米管(CNT)的环氧树脂(EP)基纳米复合材料:纯环氧树脂模型及分别掺杂未功能化、氨基功能化、羧基功能化和羟基功能化的七种EP/CNT模型(其中,功能化CNT分别接枝4或8个官能团).基于上述模型,在LAMMPS下计算热扩散系数(热导率和比热容)、玻璃转化温度及力学性能.结果表明,掺杂碳纳米管的环氧树脂纳米复合材料的各性能都有不同程度的提升,掺杂接枝8个官能团碳纳米管的EP/CNT性能提升均明显高于掺杂接枝4个相对应官能团EP/CNT的性能.其中,EP/AFCNT8在热导率、热扩散系数及力学性能上提升最明显,整体热导率和热扩散系数分别提升了54.92％和67.30％;EP/HFCNT8具有最大玻璃转化温度,提升幅度为69.47K,EP/AFCNT8提升幅度仅次于EP/HFCNT8,为58.97K.在400K时,EP/CFCNT8具有体积模量和杨氏模量最明显的提升,分别为52.4％、35.5％;因为氨基与环氧基体的交联反应,EP/AFCNT8各模量整体上提升较为明显,可更好地保持良好的力学性能.     

铂掺杂单壁碳纳米管对新型环保气体CF3I典型分解产物吸附特性研究

环保型绝缘气体CF3I会在局部放电下发生分解并生成C2F6、I2、C2F5I、C2F4和CH3I等产物.为此,该文基于密度泛函(OFT)理论,构建和优化了Pt掺杂(8,0)单壁碳纳米管(Pt-SWCNT)及两种典型CF3I局部放电分解产物C2F6和CH3I的分子模型.在此基础上,计算和分析了C2F6和CH3I气体在Pt...     

同塔双回直流输电线路的感应电压仿真研究

随着对输电能力需求的扩大,同塔双回输电技术不仅在交流输电领域应用广泛,而且在直流输电领域也逐渐得到了应用。针对同塔双回直流输电线路之间电磁耦合带来的感应电压问题,采用雷电流仿真模型、杆塔多波阻抗模型和绝缘子先导闪络模型。并建立雷电绕击故障计算模型和接地故障计算模型,对不同运行电压、导线排列方式、土壤电阻率以及排列间距等对同塔双回直流输电线路感应电压的影响进行分析,以溪洛渡直流工程为参考．研究在不同运行方式、输送功率以及加装线路避雷器情况下,同塔双回线路间的电磁耦合特性。在对溪洛渡工程实例采用ATP—EMTP进行仿真的基础上,分别对雷电绕击和接地故障2种情形下的感应电压进行计算。比较并得出了影响线路间感应电压的主要因素。     

一种新型晶体管小功率UPS系列电源的研究

介绍了一种小功率UPS系统.着重分析了通过静态开关,用以使主电源和备用电源随时进行快速切换的锁相同步跟踪技术与理论,并对整体设计做了简要地阐述.     

小型大电感风力发电机电流型逆变器研究

小型大电感永磁风力发电机具有风速工作范围宽的特点,在此提出了一种适合该类发电机的低成本电流型并网逆变器的拓扑结构,并对该并网逆变器的控制策略进行了研究.建立了逆变器系统的PSIM仿真模型,仿真结果表明提出的电流型并网逆变器能够输出可并网的电流波形.搭建了基于dsPIC30F4011单片机的硬件实验平台,初步实验结果验证了所提出的电流型并网逆变器的可行性.     

1025t/h四角切圆锅炉OFA反切消旋数值模拟研究

利用数值计算软件对某台1025 t/h四角切圆锅炉进行了OFA与三次风联合反切以降低炉膛出口热偏差的模拟研究。研究结果表明:改造后,反切层以上炉内流场旋转逐渐减弱、相对切圆直径减小,但对炉内主气流的空气动力结构影响不大;反切削弱了水平烟道入口处的扭转残余,使烟气在水平烟道内分布更加均匀,水平烟道入口左右侧温差减小。采用OFA与三次风联合反切可以有效地降低水平烟道内的热偏差,保证锅炉的安全稳定运行。     

Simulation and Experimental Study of a Reactively Loaded PWM Converter as a Fast Source of Reactive Power

The question of eliminating distorted current waveforms from power networks by active power filters is investigated. If the active current is subtracted from the distorted current, the compensating equipment must be capable of generating the inverse of this difference. Addition of this compensating current to the distorted current then eliminates the distortion. This requires the capability to generate these currents with response times many times less than the fundamental power frequency cycle. This capability is presented by reactively loaded PWM converters. A system configuration with three single-phase PWM converters building a three-phase unit is investigated. The single-phase converter with PWM operation, inductive reactance as load, low-pass input filter, and representative system losses is simulated by state-space techniques. An experimental system of 1 kVA is also constructed for verification. Good correspondence between the simulation and experiment s shown. Starting up the system, compensating the system losses from the supply, and the influence of the control system on the compensating capabilities are investigated. It is concluded that a PWM converter with a reactive load can be used as a fast distortion compensator and that the present state of the art and future development of PWM converter technology will make this technique applicable at least up to 1 Mvar.     

Systematic Study of the Dopant-Dependent Properties of Electrically Programmable Fuses With Silicided Poly-Si Links Through a Series of I– V Measurements

Electrically programmable/writable fuses (e-fuses) with a Ni-silicided polycrystalline silicon narrow link and fabricated with four doping conditions were studied using two successive I-V measurements. The initial I-V sweeps can change e-fuses into targeted programmed states and display all of the programming processes where the currents change by many orders of magnitude. The second set of I-V curves can show stability and conduction in the programmed states for both bias polarities. Through the series of I-V measurements, the two-step programming with moderate blowing conditions could be reproduced and studied systematically. The programming processes of incompletely programmed states, before complete programming (CP), were found to be strongly dependent on the dopant conditions. The origin of the dopant dependency was considered within a simple electrical equivalent circuit model. At least two or three programmed states were identified among the completely programmed states in terms of the characteristic spreads of the final resistance and conduction behavior. The most distinctive currents after CP are similar to those in varistors. The stability of every programmed state is strongly dependent on the dopant conditions.     

含多回物理直流仿真装置的大电网数模混合仿真建模及研究

为了对特高压交直流复杂电网进行仿真研究,采用基于输电线贝瑞隆模型的功率连接接口技术,连接全数字实时仿真装置HYPERSIM和高压物理直流仿真装置,建立了相应的数模混合仿真系统平台。仿真试验基于2015水平年特高压规划电网,以华东直流多落点地区为研究对象,搭建了包含16回直流输电系统的模型,其中2回为物理直流仿真装置的大规模数模混合仿真试验模型。试验结果表明,华东直流多落点地区发生的交流系统短路故障,会引起多回落点华东直流发生换相失败,但不会发生连续的换相失败并进而闭锁,系统能够保持稳定。仿真结果表明物理直流仿真装置对数字侧故障响应正确,验证了数模混合仿真研究的有效性。     

Boost+变压器串/并联型LLC级联变换器研究

为满足高压,宽输入、输出低压,大电流、高功率密度直流模块电源的技术要求,设计了一种Boost+变压器串/并联型LLC级联高频直流变换器。该级联变换器的前级Boost闭环工作,实现输出稳压;后级LLC工作在定频、开环方式,实现电气隔离与降压。对该级联变换器的工作原理进行了分析;同时,对前级Boost电路参数和后级LLC谐振参数进行了优化设计。最后,实验验证了该级联变换器理论分析的正确性与可行性。