脉冲压缩电路磁开关动态特性

提出在典型一阶磁脉冲压缩电路的基础上,测取磁芯在实际工作条件下的动态磁滞回线和饱和磁导率等磁参数,再根据所获得的动态参数指导磁开关设计,进行一阶磁压缩实验。实验选取国内外被广泛应用的非晶磁芯和纳米晶磁芯进行测试,根据实测动态磁参数设计磁开关。实测结果表明：用国产非晶磁芯做磁开关可得到上升沿73 ns、电压幅值28.3 kV、半高宽为503 ns的脉冲,用日本产的纳米晶磁芯做磁开关可得到上升沿30 ns、电压幅值28.4 kV、半高宽为193 ns的脉冲。     

20 MA/300 ns Marx型直接驱动Z箍缩脉冲源

基于金属外壳1.0 F/40 nH/100 kV的电容器和100 kV/200 kA气体开关,提出了电流20 MA、前沿300 ns Marx型直接驱动Z箍缩负载的脉冲功率源概念设想,共40路并联,每路为6个Marx并联驱动一条水介质传输线, Marx为18级串联。分析了关键单元（电容器和气体开关）的技术可行性,建立了PSpice电路模型,模拟计算了Marx建立时间分散性、水介质传输线阻抗对负载电流的影响,模拟结果表明：Marx建立时间分散性从10 ns增加到60 ns时,负载电流前沿从平均282 ns增加到287 ns,峰值从21.0 MA降低到19.8 MA,脉宽几乎不变;Marx建立时间分散性对负载电流的影响随着并联数目增加变小;采用4.2 等阻抗传输线,负载电流最大。     

非线性玻尔兹曼方程的傅里叶谱方法

玻尔兹曼方程作为空气动理学中最基本的方程之一,是连接微观牛顿力学和宏观连续介质力学的重要桥梁.该方程描述了一个由大量粒子组成的复杂系统的非平衡态时间演化:除了基本的输运项,其最重要的特性是粒子间的相互碰撞由一个高维,非局部且非线性的积分算子来描述,从而给玻尔兹曼方程的数值求解带来非常大的挑战.在过去的二十年间,基于傅里叶级数的谱方法成为了数值求解玻尔兹曼方程的一种很受欢迎且有效的确定性算法.这主要归功于谱方法的高精度及它可以被快速傅里叶变换加速的特质.本文将回顾玻尔兹曼方程的傅里叶谱方法,具体包括方法的导出,稳定性和收敛性分析,快速算法,以及在一大类基于碰撞的空气动理学方程中的推广.     

灵敏度控制思想在主动膜系设计中的快速实现算法

基于斜入射薄膜制备实践中镀膜误差对光谱性能的严重退化影响的认识,提出了一种基于灵敏度控制思想的主动膜系设计方法。在深入分析了镀膜中膜层结构参数误差的分布规律的基础上,运用膜系光谱系数关于膜层参数的导数计算的解析模型,建立了膜系灵敏度的定量计算模型和快速实现算法。以一45°入射高精度消偏振增透膜的设计实验为例,探讨了灵敏度控制思想在膜系设计中的可行性、快速性和有效性。结果表明,这一新型设计方法不会显著增加程序时间消耗,能获得具有良好可镀制性能的薄膜,对于正入射和宽角度入射膜同样适用,而且可以避免昂贵的失败试镀和采样,有助于缩短新薄膜的生产周期,特别是对于高精度斜入射薄膜的重复性制备具有重要意义。     

高压快速离化半导体开关及其脉冲压缩特性

介绍了全固态高压快速离化半导体开关(FID)的工作原理和半导体结构,实验研究了在不同外偏置电压下的输出脉冲幅度特性和脉宽压缩特性,并对实验研究结果进行分析。在50 Ω负载下,将一输入脉冲幅度1.7 kV 、脉宽4 μs、重频2 kHz高压脉冲,通过FID压缩成脉冲幅度1 985 V、脉宽90 ns、重频2 kHz的高压脉冲。     

Fast switching of vertically aligned negative liquid crystals by optically hidden relaxation

We propose a method for fast switching of vertically aligned (VA) negative liquid crystals (LCs) by hiding the relaxation process of LCs. During the turn-off process, a strong in-plane electric field is applied for a short duration of time instead of relying solely on the slow relaxation of LCs. The LC molecules are rotated to the transmission axis of one of the polarisers by the applied in-plane electric field, resulting in turn-off switching that is 5.8 times faster than that of a conventional VA cell. By applying an overdriving scheme, we experimentally obtained a total response time of 3.3 ms.     

Flash DSC crystallization study for blown film grade bimodal HDPE resins. I. Isothermal kinetics and its application of the blown film modeling

Isothermal ultra‐cooling crystallization tests were conducted on three blown film grade bimodal HDPE resins using an ultrafast scanning calorimeter, the Flash DSC. Isothermal tests were performed to study the regime transition, the thermal nucleation and the spherulitical growth using the Hoffman‐Lauritzen theory in a range between 90 °C and 116 °C. Temperature profile estimations using such data were in good agreement with actual blown film process data. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2425–2431     

Fluorescence Signal Enhancement Using Double Pass Cell Configurations

Abstract

A simple and reproducible method for increasing the sensitivity of fluorescence measurements by a factor of 2.0–2.5 is presented. Data are presented to explain: the deviation from the expected theoretical increase in sensitivity of 4.0; wavelength dependency and subsequent problems arising from enhanced inner filtering effects.     

A tin-containing liquid crystalline polymer with two glass temperatures

A tin-containing liquid crystalline side group polymer was synthesized and characterized. Two glass transitions were detected by calorimetric investigations. The X-ray pattern corresponds to a smectic C order of the side groups and a disordered isotropic main chain. Dielectric measurements show two relaxation ranges which are influenced by the glass transitions and a fast local process. The low frequency mechanism can be related to the reorientation of the side groups and the higher glass transition temperature. The second is connected with the α-relaxation of the main chain and freezes in at lower temperatures.     

一种基于Gauss von Mises分布模型的非线性量测更新方法

基于状态空间模型的许多传统滤波算法都基于Rn空间中的高斯分布模型,但当状态向量中包含角变量或方向变量时,难以达到理想的效果。针对J.T.Horwood等提出的nS?R流形上的Gauss Von Mises(GVM)多变量概率密度分布,扩展了狄拉克混合逼近方法,给出了联合分布的GVM逼近方法,推导了后验分布的GVM参数计算公式,设计了量测更新状态估计算法。将J.T.Horwood等的时间更新算法与所提出的量测更新算法相结合,可实现基于GVM分布的递推贝叶斯滤波器(GVMF)。仿真结果表明,当状态向量符合GVM概率分布模型时,GVMF对角变量的估计明显优于传统的扩展卡尔曼滤波器。