瞬态积分浓度场的测量研究

根据污染扩散烟雾粒子的成像理论、粒子光散射原理和数字图像技术,建立了烟雾粒子非定常瞬态积分浓度与 其散射图像强度之间的数学关系,通过烟雾粒子散射图像强度的数字化分析和处理来定量测量非定常瞬态污染扩散相对 瞬态积分浓度场。并利用该方法对烟雾扩散的非定常瞬态积分浓度场进行了实际测量。     

环境风洞浓度场测量系统的检验试验

为了检验环境风洞浓度场测量系统的可行性和可靠性,以及对所设计的环境风洞浓度场测量系统的误差进行分析和研究,本文发展了一种通过定量加浓的方法来检验该测量系统。检验试验是在水中加入标准粒子,利用加入粒子的浓度不同来进行测量。试验结果表明对于所提出的基于数字图像的相对浓度场测量方法正确,设计的浓度场测量系统可行、合理.     

基于偏振门的动态光散射颗粒测量法的研究

为了解决动态光散射纳米颗粒测量技术无法测量高浓度颗粒粒径的难题,提出了一种基于偏振门的动态光散射测量法。从动态光散射和Mie理论出发,理论分析了在高浓度溶液下多重散射效应对散射光偏振态和颗粒粒度测量结果的影响。根据散射光偏振特点,结合偏振门检测技术,改进了传统的动态光散射光学系统。实验研究了在低浓度和高浓度溶液时,不同偏振角度下的散射光强和粒度测量值,完善了散射光的偏振理论。采用90°偏振门检偏,通过各种浓度下的实验,证明了方法的可行性。该方法较之目前同类方法具有原理和结构简单,系统易于维护的特点。     

光散射聚集速率测定中T矩阵方法的应用

聚集速率是评估胶体体系特性及稳定性的关键参数, 静态光散射和动态光散射则是测量聚集速率的两个重要方法. 然而, 用静态光散射和动态光散射测量聚集速率时, 需要知道有关单粒子和双粒子聚集体光散射特性的数据. 为此, 通常需要把动、静两种方法结合, 才能消去这个数据. 以前各种近似理论曾用来解决这个问题, 但因粒子尺寸和形状的限制, 结果并不理想. 而T矩阵方法可以不受粒子大小和形状的限制计算其光散射特性. 本工作用T矩阵方法直接计算静态光散射和动态光散射所必须的粒子散射特性, 并将该法得到的聚集速率与动静态光散射结合法得到的聚集速率进行了比较, 两者结果很接近. 本工作为简化静态光散射和动态光散射测量聚集速率, 扩展其应用范围开辟了新途径. 关键词： T矩阵')" href="#">T矩阵 光散射法 聚集速率     

后向动态光散射系统的像差分析与校正

针对后向动态光散射颗粒测量系统信噪比较低的问题,从光学系统的像差入手,采用Zemax对其进行了仿真和分析,并提出了校正方案。首先介绍了后向动态光散射颗粒测量系统的基本原理和光学系统,从校正像差的角度出发,采用Zemax对后向动态光散射系统进行仿真,并对其像差进行分析。然后根据仿真结果,提出了校正方案,采用Ze-max设计了方案中的参数,得出了理论上的校正结果。最后采用优化好的结果进行后向动态光实验,得到了实验数据。均值误差和重复性误差分别达到了1.52%和1.24%。满足国标均值误差和重复性误差小于2%的要求。     

应用CCD对浓度场的全场瞬时测量

基于数字图像处理技术和光学粒子散射理论 ,应用CCD研究设计了具有非接触不干扰、全场测量、测量区域大和低成本等特征的湍流瞬时浓度场的光学测量系统 ,并进行了实际测量 .与文献对比分析结果表明 ,该方法是可行的和有效的 .     

紫外双光束单波长硝酸根原位监测传感器系统的研究

水中硝酸根含量的实时监测是一个亟待解决的现实问题,为了满足硝酸根监测的实时性要求,避免采样、预处理等繁琐的步骤,提出了一种新型的原位监测硝酸根传感器系统的研究设计,介绍了系统的工作原理和构成,该仪器利用双光束单波长标准测量法,不仅能有效消除材料及粒子散射对测量的干扰,而且简化了设计结构。并用紫外分光光度计进行了模拟实验,实验证明,这种新型的传感器系统能够满足指定水域的硝酸根实时监测要求。     

多模光纤式动态光散射实验研究

介绍了多模光纤在动态光散射中的应用,搭建了基于多模光纤的动态光散射实验系统,并用该系统测量了单分散、多分散以及不同浓度的标准聚苯乙烯乳胶球悬浮液.结果表明,该系统可准确地测量浓度达4.5%的聚苯乙烯乳胶球溶液中悬浮颗粒的粒径分布.     

瞬时浓度场的激光片光测量研究

根据粒子的光散射、散斑成像理论,建立了两相流动粒子相对数量浓度与粒子散斑图像强度之间的线性关系, 通过数字图像分析和处理技术进行污染扩散相对瞬时全场浓度的测量。利用粒子散斑成像测量原理自行设计了大范围瞬时浓度场测量系统,并利用该系统对烟雾扩散的瞬时浓度场进行了实际测量。     

利用反射式圆光栅的振镜转角测量

为了实现振镜旋转角度的高精度测量,设计了一种利用反射式圆形衍射光栅的角度测量系统,对该系统的测量原理、测量过程、测量精度等进行了相应的设计、仿真与验证。设计与振镜同轴的反射镜,搭配反射式圆光栅以及光敏检测器件,利用反射式圆光栅产生的±1级衍射光干涉,把振镜转角位移量转化为干涉条纹光强的变化,以实现振镜转角的测量。实验结果表明:该测量系统能实现振镜±10°的角度测量,测量精度为10″。实现了振镜旋转角度的高精度测量,并且该装置结构紧凑,满足扫描振镜的小巧化设计需求。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.