激光羽烟透过率测试技术研究

为了准确评估固体推进剂的性能,研制了红外激光羽烟透过率测量系统。系统采用透射的方法:在发射端对激光信号采用内调制,由光学系统送入接收端,并将接收到的信号进行光电转换、信号处理和A/D转换后送入计算进行数据的处理和显示。现场测试结果表明该系统的精度、响应速度和稳定度达到设计要求。     

Topological probability and connection strength induced activity in complex neural networks

Recent experimental evidence suggests that some brain activities can be assigned to small-world networks. In this work, we investigate how the topological probability p and connection strength C affect the activities of discrete neural networks with small-world (SW) connections. Network elements are described by two-dimensional map neurons (2DMNs) with the values of parameters at which no activity occurs. It is found that when the value of p is smaller or larger, there are no active neurons in the network, no matter what the value of connection strength is; for a given appropriate connection strength, there is an intermediate range of topological probability where the activity of 2DMN network is induced and enhanced. On the other hand, for a given intermediate topological probability level, there exists an optimal value of connection strength such that the frequency of activity reaches its maximum. The possible mechanism behind the action of topological probability and connection strength is addressed based on the bifurcation method. Furthermore, the effects of noise and transmission delay on the activity of neural network are also studied.     

Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Material α-RuCl3

As one of the most promising Kitaev quantum-spin-liquid（QSL） candidates,α-RuCl₃ has received a great deal of attention.However,its ground state exhibits a long-range zigzag magnetic order,which defies the QSL phase.Nevertheless,the magnetic order is fragile and can be completely suppressed by applying an external magnetic field.Here,we explore the evolution of magnetic excitations of α-RuCl₃ under an in-plane magnetic field,by carrying out inelastic neutron scattering measu...     

Experimental and numerical analysis of the multi-recessed gate structure for microwave silicon carbide power MESFETs

This paper reports that multi-recessed gate 4H-SiC MESFETs (metal semiconductor filed effect transistors) with a gate periphery of 5-mm are fabricated and characterized. The multi-recessed region under the gate terminal is applied to improve the gate--drain breakdown voltage and to alleviate the trapping induced instabilities by moving the current path away from the surface of the device. The experimental results demonstrate that microwave output power density, power gain and power-added efficiency for multi-finger 5-mm gate periphery SiC MESFETs with multi-recessed gate structure are about 29%, 1.1dB and 7% higher than those of conventional devices fabricated in this work using the same process.     

基于FPGA的DBF多波束中频接收系统的设计与实现

数字波束形成(DBF)阵列能够充分利用阵列天线所获取的空间信息,通过信号处理技术使波束获得超分辨率和低旁瓣的性能,它由天线阵元、射频下变频模块、AD采样、中频接收系统及上位机控制器组成。对中频接收系统进行数字波束形成的具体方案进行讨论,对多路接收和AD量化一致性造成的各通道间失配提出了幅相校正的解决方案,详细分析了研制中的关键技术。实验结果表明所设计的DBF多波束中频接收系统可有效实现通道间失配的校正,并实现精确的波束赋形功能。     

二维光子晶体波导与单模平面介质波导间的喇叭波导接头

提出并优化了用于二维介质柱光子晶体波导与单模平面介质波导对接的基于分布布拉格反射波导的喇叭波导接头，提高了这两种波导之间的传输效率.二维时域有限差分仿真结果表明，在大部分光子晶体波导导模的频谱范围内，传输效率高于98％.传输效率最高可以达到99.85％. 关键词： 光子晶体波导 平面介质波导 时域有限差分     

High holding voltage SCR for robust electrostatic discharge protection

A novel silicon controlled rectifier(SCR) with high holding voltage(Vh) for electrostatic discharge(ESD) protection is proposed and investigated in this paper. The proposed SCR obtains high Vhby adding a long N+ layer(LN+) and a long P+ layer(LP+), which divide the conventional low voltage trigger silicon controlled rectifier(LVTSCR) into two SCRs(SCR1: P+/Nwell/Pwell/N+ and SCR2: P+/LN+/LP+/N+) with a shared emitter. Under the low ESD current(IESD), the two SCRs are turned on at the same time to induce the first snapback with high V_h(V_(h1)). As the IESDincreases, the SCR2 will be turned off because of its low current gain. Therefore, the IESDwill flow through the longer SCR1 path, bypassing SCR2, which induces the second snapback with high V_h(V_(h2)). The anti-latch-up ability of the proposed SCR for ESD protection is proved by a dynamic TLP-like(Transmission Line Pulse-like) simulation. An optimized V_(h2) of 7.4 V with a maximum failure current(I_(t2)) of 14.7 m A/μm is obtained by the simulation.     

Significant improvement of OLED efficiency and stability by doping both HTL and ETL with different dopant in heterojunction of polymer/small-molecules

This paper reports that the polymer/organic heterojunction doped light-emitting diodes using a novel poly-TPD as hole transport material and doping both hole transport layer and emitter layer with the highly fluorescent rubrene and DCJTB has been successfully fabricated. The basic structure of the heterostructure is PTPD/Alq₃. When hole transport layer and electron transport layer are doped simultaneously with different dopant, the electroluminescence quantum efficiencies are about 3 times greater than that of the undoped device. Compared with undoped device and conventional TPD/Alq₃ diode, the stability of the doping device is significantly improved. The process of emission for doped device may include carrier trapping as well as F\"{o}rster energy transfer.     

不连续导电模式DC-DC变换器的倍周期分岔机理研究

根据一般迭代映射的倍周期分岔定理,从数学上论证了电压型不连续导电模式(DCM) Boost和Buck变换器中倍周期分岔现象产生条件,由此揭示了DC-DC变换器中倍周期分岔现象发生的机理,完善了该类变换器倍周期分岔分析的理论和方法. 关键词： 倍周期分岔 迭代映射 Lyapunov 指数 施瓦茨导数     

含尺度效应的功能梯度三明治微梁振动、弯曲与屈曲特性研究

基于修正的应变梯度理论和精化的高阶剪切变形理论,提出了一种含尺度效应的功能梯度三明治微梁模型。功能梯度材料的等效弹性参数由Mori-Tanaka均匀化方法描述。针对微梁的高阶边值问题,融合微分求积和Gauss-Lobatto求积准则,建立了一种2节点18自由度的微分求积有限元。通过对比性研究,验证了理论及数值模型的有效性。最后,讨论了边界条件、材料尺度参数、功能梯度指数、长细比、各层厚度比等对功能梯度三明治微梁静动态特性的影响。结果表明,功能梯度三明治微梁的静力响应、振动频率、屈曲荷载以及模态均呈现出显著的尺度效应,所得结果有望为微机电系统中承载器件的设计提供数据积累和方法依据。