Synthesis and characterization of a novel ambipolar polymer semiconductor based on a fumaronitrile core as an electron‐withdrawing group

Two conjugated polymers containing stilbene and fumaronitrile moieties were synthesized to investigate their electronic properties by the existence of electron‐withdrawing cyano groups on a vinylene backbone. The cyclic voltammetry investigation and time‐dependent density functional theory calculations indicated that the cyano substituents lowered the lowest unoccupied molecular orbital (LUMO) energy level by about 0.65 and 0.63 eV, respectively. The lowering of the LUMO energy levels due to the electron‐withdrawing properties of the cyano substituents could enhance electron injection capability. Furthermore, bithiophene‐fumaronitrile (donor‐acceptor) intermolecular interaction facilitates the self‐assembly of the polymer chains. Organic field‐effect transistors (OFETs) based on PBTSB without the electron‐withdrawing group only exhibit hole transport, while OFETs based on PBTFN with cyano substituents exhibit ambipolar characteristics. The growth of PBTFN crystalline fibrils was observed with increasing annealing temperature, which enhanced hole and electron mobility. A complementary‐like inverter using PBTFN with ambipolar properties exhibited good symmetry with an inverting voltage nearly half that of the power supply with a gain of 9 at V_DD = 100 V. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

双降压式全桥逆变器非线性现象的研究

双降压式全桥逆变器具有无桥臂直通、输入直流电压利用率高、效率高、续流二极管可优化选取等优点,因而在高压输出场合得到广泛的应用.本文研究了双降压式全桥逆变器的分岔和混沌现象,建立了电流闭环比例控制下的二阶离散模型,得到了不同时间段内的频闪映射模型;通过折叠图和分岔图分析了不同比例系数k对于系统稳定性的影响,并搭建了Matlab/Simulink仿真模型,得到了电流闭环比例控制时电流iL的时域波形和相图轨迹,并在频域下分析了分岔和混沌对系统频谱的影响.同时,利用分岔图的方法分析了输入电压E、滤波电感L和开关周期T等外部参数变化时系统的非线性行为.研究结果表明,正确选择双降压式全桥逆变器的电路参数对于其稳定运行具有重要意义.     

All-Fiber Optical Signal Inversion Using Stimulated Raman Scattering

We propose a method for all-optical signal inversion by means of stimulated Raman scattering (SRS). The idea is based on the transference of energy from the logic state #x201C;1#x201D; to the second stokes and making the logic state #x201C;0#x201D; into logic state #x201C;1#x201D; by receiving energy from the pump through SRS. According to the numerical simulation, a continuous wave pump source of LOW at 1453 nm and a few hundred meters of highly nonlinear fiber are required to invert an input signal at 1555 nm. The optical signal is inverted with high on-off contrast ratio.     

Multirate Partitioned Runge-Kutta Methods

The coupling of subsystems in a hierarchical modelling approach leads to different time constants in the dynamical simulation of technical systems. Multirate schemes exploit the different time scales by using different time steps for the subsystems. The stiffness of the system or at least of some subsystems in chemical reaction kinetics or network analysis, for example, forbids the use of explicit integration schemes. To cope with stiff problems, we introduce multirate schemes based on partitioned Runge—Kutta methods which avoid the coupling between active and latent components based on interpolating and extrapolating state variables. Order conditions and test results for such a lower order MPRK method are presented.This revised version was published online in October 2005 with corrections to the Cover Date.     

基于模糊控制的VSVPWM中点电位平衡策略

针对中点钳位型(NPC)三电平逆变器存在的直流侧中点电位不平衡问题,提出了一种基于模糊控制 的中点电位平衡策略。该策略重新定义了虚拟空间矢量,使虚拟小矢量不引起中点电位波动,并在虚拟中矢量中 引入了对中点电位不平衡有抑制作用的控制因子 Q。同时,设计了由模糊控制器 A 和 B 构成的组合模糊控制器, 该控制器能够依据中点电位偏移情况调整控制因子 Q,实现对中点电位的闭环控制。仿真和实验结果表明,采用 该策略的 NPC 型三电平逆变器中点电位不平衡问题能得到有效改善。     

并联谐振变换器式电容器充电电源

针对采用串联谐振变换器电容器充电电源的不足,通过分析、改进并联谐振变换器拓扑,研制了基于并联谐振全桥变换器研制的10 kJ/s,100 kV电容器充电电源,变换器开关采用脉冲宽度调制技术,开关频率达40 kHz,电源的反馈控制电路基于数字信号处理全数字控制器。并给出了充电电源及主要部件高频高压变压器的设计注意事项、经验及实验结果。     

基于周期性扩频的单相H桥逆变器非线性现象的研究

将周期性扩频技术用于变换器中来抑制其电磁干扰和噪声已经得到了论证并被广泛的应用, 但却忽略了其中的非线性现象. 在分析了周期性扩频技术和单相SPWM-H桥正弦逆变器的精确频闪映射模型的基础上, 研究了采用周期性扩频技术的单相H桥正弦逆变器的分岔和混沌现象, 建立了H桥正弦逆变器扩频后的离散模型, 通过时域图、折叠图、分岔图及李雅亚普诺夫指数谱对其非线性现象进行了分析. 研究表明, 扩频后的H桥正弦逆变器在进入非线性区域后更容易进入混沌区, 并且周期扩频的频率会对系统产生初始分岔点的位置产生影响. 关键词： H桥逆变器 周期性扩频 分岔 混沌     

风冷冷冻柜中毛细管特性的试验研究

以某风冷冷冻柜为研究对象,分别从毛细管长度、制冷剂充注量、频率变化三个方面试验分析毛细管对制冷系统性能的影响。试验得出最佳毛细管长度为650mm;最佳充注量为1060g;系统高能效比的频率范围在20Hz～60Hz之间,对于在稳定工况下运行的机组,变频并不能起到很好的节能效果。通过标准毛细管和使用一定时间后的被测毛细管的对比分析,改变电流模拟分析系统启停,得到以库中央温度和冷凝器中央温度为代表的影响系统性能的变化曲线。实际运行中可通过监测库中央温度、冷凝器中央温度、压缩机吸气和排气温度、压缩机上下表面温度,与标准毛细管对比就可准确判断出系统运行状态是否正常。     

并联谐振变换器式电容器充电电源

针对采用串联谐振变换器电容器充电电源的不足,通过分析、改进并联谐振变换器拓扑,研制了基于并联谐振全桥变换器研制的10 kJ/s,100 kV电容器充电电源,变换器开关采用脉冲宽度调制技术,开关频率达40 kHz,电源的反馈控制电路基于数字信号处理全数字控制器。并给出了充电电源及主要部件高频高压变压器的设计注意事项、经验及实验结果。     

单相三电平H桥逆变器分岔现象的研究

三电平逆变器相较于传统的两电平逆变器具有输出电压谐波畸变率小、开关管电压应力小等优点,因而在大功率场合受到了越来越多的关注. 本文针对一种复合式单相三电平逆变器,对其中的分岔和混沌现象进行了深入的研究,建立了电流闭环比例控制下的一阶离散模型,得到了不同时间段内的频闪映射模型. 以比例系数k,负载电阻R,负载电感L及输入电压E为变化参数,研究了三电平逆变器的分岔现象：通过分岔图和李雅普诺夫指数谱分析了慢变尺度下比例系数、负载电感、负载电阻和输入电压对系统动态性能的影响;通过折叠图直观地观测到了快变尺度下不同比例系数、负载电感所导致的分岔过程. 最后搭建了Matlab/Simulink仿真模型,得到了电流闭环比例控制时电流i的时域波形,仿真结果与理论分析相一致. 研究表明,正确选择单相三电平逆变器的电路参数对于其稳定运行具有重要意义. 关键词： 三电平逆变器 频闪映射 分岔 混沌