一种用于电光开关的高速、高压电脉冲的产生

介绍了一种用于电光开关驱动源的高压超快电脉冲产生技术;电路采用级联的雪崩晶体管串和微波传输线结构,输出阻抗50Ω;在50Ω负载情况下,获得脉冲下降时间为1ns、幅度达到5kV、峰值电压为6.4 kV、幅度和半宽度稳定性优于2％、触发晃动为±15ps、触发延时为30 ns,脉冲峰值电流为128 A的高压高速大电流脉冲.     

低于13K的单级脉管制冷机性能研究

回热器是脉管制冷机的关键部件之一,其效率对脉管制冷机性能有很大影响。铅丸是常见的蓄冷材料,通常用于回热器的低温端。本文测试和分析了不同品质的国产铅丸和进口铅丸对单级G-M型脉管制冷机性能的影响。采用额定功率为6．0 kW的压缩机驱动,使用进口铅丸脉管制冷机最低制冷温度达12．9 K,这是当前单级脉管制冷机达到的最低制冷温度;40 K时的最大制冷量为57．4 W。使用国产铅丸最低制冷温度为13．6 K,40 K时的最大制冷量为55．9 W。本文对低温制冷机蓄冷材料选择具有一定的参考价值。     

Optical Glucose Monitoring Based on Femtosecond Two-Color Pulse Interferometry

We demonstrate the potential of femtosecond two-color pulse interferometry for in vitro optical glucose monitoring, by dispersion of the group refractive index in a glucose solution sample with respect to a red-color light and a blue-color light. By comparison with femtosecond one-color pulse interferometry, the basic performance of the present system with regard to sensitivity, quantitativeness, and tolerance to surrounding disturbances, is evaluated. The resulting accuracy and precision of glucose determination are 77 and 118mg/dl for 10-mm-sample-thickness, respectively. This near-common-path configuration of the two-color pulse light provides good stability to fluctuations of sample temperature, which is important in clinical applications. Considering the performance of femtosecond two-color pulse interferometry as an optical glucose sensor, a suitable measurement site for in vivo optical glucose monitoring is discussed.     

Role of ligands in the formation, phase stabilization, structural and magnetic properties of α-Fe2O3 nanoparticles

The electrochemical synthesis of alpha Fe₂O₃ nanoparticles was performed using quaternary ammonium salts viz. TPAB, TBAB and TOAB in an organic medium by optimizing current density and molar concentration of the ligand. The role of ligands in the formation of α phase, structure and magnetic properties was investigated in details. The effect of increasing chain length on the particle size confirmed that as the chain length increases from propyl to octyl, the particle size decreases. X-ray diffraction spectra of as prepared samples and TEM analysis confirmed the amorphous nature of iron oxide. TEM showed beads of iron oxide joined together with a size distribution in the range of 6–30 nm. The Mossbauer studies also support this observation that for the lowest particle size, the line width is broader which successively reduces with increase in particle size. Iron oxide capped with TOAB indicated superparamagnetic nature at room temperature. The resultant internal magnetic field of 506 mm/s due to hyperfine splitting clearly established the formation of α-Fe₂O₃ The infrared spectroscopy and pH measurements revealed the binding of tetra alkyl ligand with iron oxide. The IR spectra and the increase in basicity of as prepared samples confirmed the formation of hydrated iron oxide. Above 800°C the spectra indicated only iron oxide. Surface area obtained by BET method was 205 m²/g.     

光子晶体光纤超连续谱产生的实验研究

报道了利用掺钛蓝宝石飞秒激光器产生重复频率为80MHz,脉宽为10fs的超短激光脉冲在10cm长光子晶体光纤产生超连续谱的实验,获得展宽范围为450nm到1100nm的连续谱。实验中观察到孤子自频移和高阶孤子分裂现象,非孤子辐射与随后光谱向短波方向的拓展有密切关系。     

空间遥感相机长条反射镜组件的动力学特性分析

空间遥感相机长条反射镜较圆反射镜的整体刚度相差很大,整个组件在随火箭发射过程中因力学环境引起的自身位置改变导致面形的微小畸变从而对成像质量造成严重影响。因此,反射镜组件的设计就成为整个相机系统研制的重点与难点之一。对其进行科学、严谨的力学环境仿真是设计中的有效辅助手段。对某相机的长条反射镜组件动力学响应进行了较为深入的研究,借助MSC-patran,用有限元法进行了求解。获得了组件的动力学特性。     

光电经纬仪机电一体化耦合特性

区别于传统刚体控制模型,将结构动态设计方法与控制理论相结合,构建了光电经纬仪的柔性机电耦合控制模型,分析了该模型的结构基频、阻尼比等机械因素与控制带宽的耦合关系,并提出了光电经纬仪动态量化设计准则.实验表明:光电经纬仪结构谐振频率ω_n应尽可能地远大于系统谐振频率ω_r,至少满足ω_n≥3ω_r.该方法有效可行,可解决高精度大型经纬仪机电谐振问题,为设计快速响应、高跟踪精度的光电经纬仪提供了工程依据.     

基于Fibonacci序列准周期结构的小角度低通空间滤波器

利用常规材料构造了Fibonacci序列准周期结构,运用传输矩阵法研究了该结构的空间传输特性,并基于该结构优良的空间传输特性设计了小角度低通空间滤波器.数值模拟结果表明,该小角度空间滤波器的角域带宽可通过改变序列的结构类型和序列数来调谐,其调谐规律为:随着Fibonacci序列F(m,1)中m值的增加,对应空间滤波器的角域带宽减小;随着序列数的增大,对应角域带宽也减小.在调谐的基础上,还可通过改变构成准周期结构的介质折射率参量来精确调节其角域带宽.相比于基于超材料的小角度空间滤波器而言,基于Fibonacci序列的小角度空间滤波器制备更简单,且有望应用于新一代的高功率激光系统中.     

基于光纤光栅的冲击能检测

提出一种利用光纤光栅作为传感元构成传感阵列对冲击能进行检测的方法.通过搭建简易冲击系统装置,将光纤光栅应变传感器沿轴向对称粘贴于圆杆表面,对入射应力波能量进行检测.实验结果表明,两杆对心正冲击时入射应力波幅值最大,能量传递效率最高.通过分析频率域内的应力波信号可知,其能量主要集中在0~5 000Hz频率范围内.将入射应力波能量与冲杆动能进行对比,结果表明冲杆与圆杆传递能比在93%以上,基本满足冲击机械性能测试的需求.     

时域多模飞秒压缩光场测量中的本地光脉冲整形研究

基于飞秒脉冲的同步泵浦参量过程产生的多模时域飞秒压缩光场,由于其独特的优势,特别是可以享有单模光纤网络兼容,是实现可扩展量子计算及大容量量子通讯的良好光源。由于无法实现多模时域飞秒压缩光场的空间分离,目前对于多模时域飞秒压缩光场的测量,采用最为有效的平衡零拍探测。因此如何构造与时域飞秒压缩光场时域函数分布相同的本地光,是其中的关键内容,并直接影响测量效果。本文主要理论研究了本地脉冲光的时域整形方案,分析了系统参数对整形后的多模本地光的保真度以及系统调制效率的影响,并结合实验参数提出可能的解决办法。