Nonlinear Transient and Distortion Analysis via Frequency Domain Volterra Series

This paper presents a novel approach for transient and distortion analyses for time-invariant and periodically time-varying mildly nonlinear analog circuits. Our method is based on a frequency domain Volterra series representation of nonlinear circuits. It computes the nonlinear responses using a nonlinear current method that recursively solves a series of linear Volterra circuits to obtain linear and higher-order responses of a nonlinear circuit. Unlike existing approaches, where Volterra circuits are solved mainly in the time domain, the new method solves the linear Volterra circuits directly in the frequency domain via an efficient graph-based technique, which can derive transfer functions for any large linear network efficiently. As a result, both frequency domain characteristics, like harmonic and intermodulation distortion, and time domain waveforms can be computed efficiently. The new algorithm takes advantage of identical Volterra circuits for second- and higher-order responses, which results in significant savings in driving the transfer functions. Experimental results for two circuits—a low-noise amplifier and a switching mixer—are obtained and compared with SPICE3 to validate the effectiveness of this method.     

施主型界面态引起槽栅PMOSFET性能退化的特征

基于流体动力学能量输运模型 ,对沟道杂质浓度不同的深亚微米槽栅和平面 PMOSFET中施主型界面态引起的器件特性的退化进行了研究 .研究结果表明同样浓度的界面态密度在槽栅器件中引起的器件特性的漂移远大于平面器件 ,且电子施主界面态密度对器件特性的影响远大于空穴界面态 .特别是沟道杂质浓度不同 ,界面态引起的器件特性的退化不同 .沟道掺杂浓度提高 ,同样的界面态密度造成的漏极特性漂移增大 .     

无人驾驶自转旋翼机高度控制

通过对无人驾驶自转旋翼机纵向通道的数学模型和机理分析,研究了旋翼机的高度控制策略,提出了一种以俯仰姿态控制和发动机推力控制为基本控制回路的高度控制方法,实现了自转旋翼机的定高控制和高度跟随控制.通过仿真验证,所提出的无人驾驶自转旋翼机高度控制方法具有较好的高度跟随特性.     

炮兵弹药动态消耗规律

应用系统动力学方法建立了基于兰切斯特平方律方程的弹药消耗SD模型,为了宏观认识炮兵弹药消耗规律,选用不同策略对模型参数进行了调整,并在Vensim平台上进行了仿真实验,得出了弹药消耗随兵力、损耗系数变化的关系和规律。实践证明,该方法研究弹药消耗规律,实用性强、可行性好,能够为指挥员科学决策提供有力的方法支撑。     

基于“北斗”的语音通讯传输

北斗卫星导航系统是我国自主研发且具有通信能力的区域性卫星导航系统,具有其他导航系统不具备的双向短报文通信功能。针对用户在抢险救灾等各种复杂环境中对语音通讯的需要,在北斗卫星导航系统短报文通信功能的基础上,设计一种可用于语音传输的系统。基于现有的北斗通信终端通过硬件扩展实现语音通信传输功能;通过语音压缩技术解决大量语音数据有效传输的问题。结合试验对语音数据进行分析,系统能顺利进行语音通信,语音质量达到预期效果。     

基于MoO3和Re-Bphen修饰有机太阳能电池性能的研究

有机太阳能电池(OSCs)的性能与材料及器件结构密切相关。以MoO3为阳极缓冲层,有机金属配合物Re-Bphen为阴极缓冲层,制备了结构为ITO/MoO3/CuPc/C60/Re-Bphen/Al的OSCs。在标准太阳光照条件下,当MoO3和Re-Bphen的厚分别为5nm和8nm时实现了器件的最佳性能,能量转换效率(PCE)和器件寿命均显著提高。结合器件结构,分析了工作机制。     

菱体型消色差延迟器的优化设计

通过对菱体型延迟器件进行优化设计,能够改善其消色差性。根据光在介质表面全反射时发生相变这一原理,分析了一个具有3个全内反射面的菱体型延迟器件,得出了相位延迟δ与全内反射角θ和相位延迟δ与介质折射率n的关系。通过对δ与θ和δ与n的关系分析,显示了扩大材料选择范围的可行性。结果表明,较大的全内反射角的选择有利于改善延迟器件的消色差性。     

Room-Temperature Metal-Catalyzed Ultrafast Gasification of Ultrathin Boron Flakes

The trivalent outer shell of boron renders this element electron-poor but chemically rich, exhibiting more than one dozen allotropes. Its 2D polymorph has been recently synthesized on metal substrates under ultrahigh vacuum and has attracted intense interest. However, probing its properties ex situ has been challenging due to the quality degradation—surface oxidation—that occurs upon exposure to ambient environments. Herein, this surface chemistry is investigated in regard to the air stability of ultrathin boron flakes on metals prepared by atmospheric-pressure chemical vapor deposition. The characteristic Volmer–Weber growth is recognized by the stacking of polygon-shaped, thin flakes as isolated islands. Significantly, the metal-catalyzed, ultrafast gasification of boron flakes at room temperature, exemplified by the complete, spontaneous vanishment of 200 nm-thick boron islands in 3 h is observed. A two-step mechanism, first oxygen-involved surface oxidation and then subsequent reactions with water forming a highly volatile boric acid layer, is unambiguously revealed by combined surface characterizations. The catalysis by metal substrates, corroborated by theoretical calculations, is attributed as the crucial cause of the unprecedented gasification. The concept of oxygen-free growth is thereby proposed for air-sensitive material growth by introducing in situ oxygen scavengers. These findings significantly expand the fundamental understanding of the surface chemistry of boron and pave the way for the chemical vapor deposition growth of hydrophobic materials.     

垂直腔面发射激光器中选择性氧化工艺稳定性研究

选择性氧化工艺已经成为制备高性能垂直腔面发射激光器(VCSEL)的关键技术,氧化后形成的氧化层提供了良好的电限制和折射率导引,但选择性氧化速率是呈线性规律还是抛物线规律仍存在很大的争议.在多种温度条件下,做了环形沟槽和环形分布孔的氧化实验,这是在垂直腔面发射激光器中采用的两种结构.实验结果表明,氧化窗口形状对氧化速率的影响也依赖温度条件,并对这种实验现象给出了定性解释.     

Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured. Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.