Method of sensitivity improving in the non-dispersive infrared gas analysis system

A method of interference correction for improving the sensitivity of non-dispersive infrared (NDIR) gas analysis system is demonstrated. Based on the proposed method, the interference due to water vapor and carbon dioxide in the NDIR NO analyzer is corrected. After interference correction, the absorbance signal at the NO filter channel is only controlled by the absorption of NO, and the sensitivity of the analyzer is improved greatly. In the field experiment for pollution source emission monitoring, the concentration trend of NO monitored by NDIR analyzer is in good agreement with the differential optical absorption spectroscopy NO analyzer. Small variations of NO concentration can also be resolved, and the measuring correlation coefficient of the two analyzers is 94.28%.     

Modified adaptive algebraic tomographic reconstruction of gas distribution from incomplete projection by a two-wavelength absorption scheme

A modified adaptive algebraic reconstruction technique (MAART) with an auto-adjustment relaxation parameter and smoothness regularization is developed to reveal the tomographic reconstruction of H 2 O distribution in combustion from incomplete projections. Determinations of relaxation parameter and regularization factor are discussed with regard to the consideration of improvement in reconstruction and reduction of computational burden. A two-wavelength scheme from tunable diode laser absorption measurement, 7444.36 and 7185.59 cm 1 , is used to simplify the nonlinear solution problem for obtaining the tomographic distributions of concentration and temperature simultaneously. Results of calculations demonstrate that MAART can perform the reconstruction results more efficiently with little complex modification and much lower iterations as compared with the traditional algebraic reconstruction technique (ART) or simultaneous iterative reconstruction technique (SIRT) methods. The stability of the algorithm is studied by reconstruction from projections with random noise at different levels to demonstrate the dependence of reconstruction results on precise line-of-sight measurements.     

平面约束下金属铁磁条中平行抽运微波磁场的非稳定阈值研究

运用Landau-Lifshitz方程,边界处动态磁化强度由有效偶极边界条件约束,研究了无限长金属磁条中自旋波传播的特征,得到了该体系抽运微波磁场的阈值曲线以及色散曲线的解析式,揭示出自旋波激发谱与磁条宽度的具体关系.结果表明,平面约束下磁条的阈值曲线中出现了明显的扭结现象.并且随着磁条宽度的增加,其扭结数近似地呈指数形式增加,而最低扭结处两阈值的跳跃差值几乎呈反比形式变化. 关键词： Landau-Lifshitz方程 有效偶极边界条件 阈值曲线 色散曲线     

腔内型光电导太赫兹辐射产生器设计

提出了在飞秒锁模钛宝石激光器腔内产生太赫兹辐射的新设计方案,并给出了太赫兹产生器件的结构参数以及器件的设计原理.新设计的器件把光电导太赫兹偶极天线发射器与飞秒钛宝石激光器的可饱和Bragg反射镜结合在一起,不仅可以提高太赫兹辐射的产生效率,而且可以使飞秒钛宝石激光器自启动锁模.     

HL-2A装置改造方案磁流体平衡的数值模拟

对HL-2A装置的改造方案进行数值模拟,获得了放电初始阶段零场区域设计的最佳方案、等离子体限制器平衡位形、单零偏滤器平衡位形和双零偏滤器平衡位形以及从气体击穿到等离子体电流平顶的等离子体平衡位形的演化过程。计算结果表明,该装置设计方案能够满足装置预期的设计参数要求。     

多注毫米波行波管收集极的热设计

 为解决多注毫米波行波管收集极的散热问题,保障行波管工作可靠性与稳定性,利用 ANSYS 有限元软件模拟分析了收集极的传热特性,针对性地调整和优化了收集极相关参数与结构。研究结果表明：接触热阻是造成收集极具有较高温升的一个重要因素,由接触热阻所造成的温升约占收集极内外温度差的1/3;并不是第二电极与磁环接触宽度越宽所对应的收集极散热能力就越强,而是在一定工作条件下其散热能力存在极限值;对于绝缘陶瓷材料,应根据绝缘陶瓷的温度特性以及行波管的功率大小来进行选择;翼片式散热器是一种符合设计要求的理想散热结构。     

The transient scattering mechanism of dipole array with reflector

The transient backscattering mechanisms of a dipole array with reflector have been investigated from different aspects： time-domain, frequency-domain, and combined time-frequency domain, using 4 × 8 dipole arrays with reflector as an example. The data of scattering from the arrays under the incidence of Gaussian pulses are obtained by finite differential time domain method. The influences of the array structural parameters, incident wave parameters, and incident angles on the waveforms, spectrum, and time-frequency representations of the backscattered fields of the arrays are analysed and conclusions are drawn. From these characteristics and conclusions, it is possible to deduce the array structure inversely from the backscattered field.     

含有源频率选择表面可调复合吸波体

基于传输线等效理论,设计了含有源频率选择表面(active frequency selective surface,AFSS)的三层可调复合吸波体,第一层是表面层,为AFSS衬底;中间层是AFSS层,由频率选择表面(frequency selective surface,FSS)和PIN二极管阵列构成;第三层是介质层.反射率测量结果表明,通过调节PIN二极管阵列偏置电压可以动态调节吸波体反射特性,在偏置电压为5 V时,可获得最佳吸波性能,在5—15 GHz和5.3—13 GHz频段分别可获得-8 dB和- 关键词： 频率选择表面 复合吸波材料 反射率 PIN二极管     

有旋和无旋气固两相湍流的不同结构

了解有旋和无旋突扩气粒两相详细湍流结构对控制燃料-空气混合、火焰稳定以及燃烧污染物生成很重要.周力行等曾经对其中的两相时平均流场和湍流特性进行过雷诺平均的RANS模拟和测量的研究,但是BANS模拟不能给出详细的两相湍流的瞬态结构.本文建立了二阶矩两相亚网格尺度应力模型,对有旋和无旋同轴突扩气粒两相流动进行了双流体大涡模...     

基于实时Linux的极向场电源主控制系统的设计

为了满足极向场电源控制系统严苛的实时响应的要求,选择实时Linux系统作为系统平台,采用一个开放源代码的、基于C/C++的Eclipse可扩展的开发平台作为开发工具,完成极向场电源主控制系统的设计,实现了在一个控制周期内(1ms)对极向场电源系统的12套本地控制器的实时通信和实时控制。对极向场电源主控制系统的高速通信和实时控制、稳定可靠等关键问题给出了可行的实践性的解决方法。经实验测试,该设计运行稳定,能满足极向场电源控制系统的实时需求。