高功率激光驱动器中小尺度自聚焦和空间噪声模型

建立了一套线性的近似分析方法, 研究高功率激光驱动器中强激光传输的小尺度自聚焦效应和空间相位噪声对光束传输和光束质量的影响, 给出了系统空间噪声强度、B积分值与光束近场调制对比度之间的定量关系. 研究表明为保证输出光束质量, 即近场调制对比度小于给定值, 系统内的噪声强度必须符合一定的谱分布.     

CDMA2000系统用高温超导线性相位滤波器的研制

针对第3代移动通信CDMA2000标准对高温超导滤波器提出的技术要求,设计了一种自均衡特性的高温超导线性相位滤波器,给出了线性相位滤波器的设计原理、拓扑结构、理论计算结果、耦合矩阵、等效电路、滤波器模拟仿真结果以及实际制作的高温超导滤波器测试曲线.设计的线性相位滤波器中心频率为830MHz,滤波器阶数为12阶,引入2个交叉耦合,滤波器实际测试曲线、模拟仿真结果、理论计算三者有很好的吻合,滤波器的带边陡度达37dB/MHz,60%带宽内的群时延波动小于±10ns.     

正则扰动下周期时变系数矩阵Sylvester表示的振荡器相位噪声分析方法

振荡器的相位噪声分析是通过扰动自激大信号状态方程, 导出周期时变小信号状态方程进行的. 在振荡器的时域稳态解上应用传统的正则扰动方法, 对周期时变系数Jacobi矩阵按照Sylvester定理进行分解, 在它的周期向量构成的空间上, 分析振荡器在扰动下能保持周期稳态的条件; 注入表示白噪声的频域伪正弦信号和时域δ相关信号, 应用随机微分方法, 揭示相位噪声的产生过程, 计算相位抖动; 应用调频的原理分析幂律谱和Lorentz谱的形成以及它们之间的关系, 并获得包含谐波的Lorentz功率谱. 以周期系数Jacobi矩阵为基础, 构造简单的计算Floquet指数和相位噪声的算法流程并给出简单实例. 最后指出振荡器相位噪声分析的难点和发展方向.     

基于AT89S52单片机的智能型快速调温电烙铁的研制

本文介绍了一种基于AT89S52单片机和热电偶的智能型快速调温电烙铁的研制,重点分析了温度测量,参数设定及电源供电电路的设计.该电烙铁克服了传统电烙铁存在的高温空烧、寿命短、不能自动断电、升温缓慢等缺陷,具有工作温度和保持温度可调、快速升温、自动睡眠和唤醒等功能.     

二次注入锁定低相噪光电振荡器及其稳定性控制电路的研制

首次提出采用二次注入锁定的方案来实现低相噪光电振荡器的设计,通过注入锁定长光纤环光电振荡器来实现单模、低相噪的振荡信号,并以之为二次注入源,注入锁定另一长光纤环光电振荡器,通过该方案进一步提高注入源稳定性,最终实现超低相噪的振荡信号.实验表明,通过一次注入锁定,X波段光电振荡器的相位噪声在10 kHz频偏由-121 dBc/Hz降低到-135 dBc/Hz,二次注入后下降到-146 dBc/Hz,目前国内无如此高指标报道,接近美国海军实验室报道指标.为推进光电振荡器走向实用阶段,基于锁相原理设计了一种新型的稳定性控制电路并进行了相关实验,验证了该电路的有效性.     

原子时频技术进展

概述了传统原子频标的现状,以及新型原子频标和国际原子时的研究进展。介绍了为适应高精度新型频标和国际原子时的比对需要而开展的远程时频传递技术。     

Forecasting High‐Frequency Risk Measures

This article proposes intraday high‐frequency risk (HFR) measures for market risk in the case of irregularly spaced high‐frequency data. In this context, we distinguish three concepts of value‐at‐risk (VaR): the total VaR, the marginal (or per‐time‐unit) VaR and the instantaneous VaR. Since the market risk is obviously related to the duration between two consecutive trades, these measures are completed with a duration risk measure, i.e. the time‐at‐risk (TaR). We propose a forecasting procedure for VaR and TaR for each trade or other market microstructure event. Subsequently, we perform a backtesting procedure specifically designed to assess the validity of the VaR and TaR forecasts on irregularly spaced data. The performance of the HFR measure is illustrated in an empirical application for two stocks (Bank of America and Microsoft) and an exchange‐traded fund based on Standard & Poor's 500 index. We show that the intraday HFR forecasts capture accurately the volatility and duration dynamics for these three assets. Copyright © 2015 John Wiley & Sons, Ltd.     

Frequency gradient in the autorhythmicity of the pyeloureteral pacemaker system

Summary The pacemaker properties of the various regions of isolated segments of the rabbit renal pelvis were examined. The results show that pacemaker frequency and waveform of contraction change significantly within the renal pelvis. The highest frequency was encountered at the fornix, while the ureteropelvic junction is lowest.This work was supported by NIH Grant No AM19366.     

Frequency gradient in the autorhythmicity of the pyeloureteral pacemaker system

The pacemaker properties of the various regions of isolated segments of the rabbit renal pelvis were examined. The results show that pacemaker frequency and waveform of contraction change significantly within the renal pelvis. The highest frequency was encountered at the fornix, while the ureteropelvic junction is lowest.     

硅基高频器件与SiGe外延技术

本文描述了应用于SiGe外延的分子束外延(MBE)、超高真空化学气相沉积(UHV／CVD)、常压化学气相沉积(APCVD)、快速热化学气相沉积(RTCVD)等几种工艺及这几种工艺中的常见问题，并介绍了近来这些SiGe外延技术的改进，最后从器件角度对以上几种工艺特性进行了比较。