基于光散射的火灾烟雾粒子激光图像探测技术研究

本文结合火灾探测领域的特点,分析了火灾烟雾粒子的光散射特性。通过与其他类型的光电感烟火灾烟雾探测技术的比较,阐述了基于光散射的火灾烟雾粒子激光图像探测技术的原理、特点和技术优势。     

光散射在烟尘探测中的应用

利用烟尘微粒对光的散射作用，通过测量散射光的强度，可以作为烟尘的传感信号，这种信号可用于火警初期的报警信号，进行火警探测，从而扩充了光散射现象的应用范围。     

烃类烟粒红外复折射率的测定与应用

测定了室温下烃类(乙炔、乙烷)烟粒的红外复折射率,并讨论了所获数据在测量烟浓度与烟粒大小分类、计算光谱吸收系数及在特定浓度与温度下评估烟雾辐射率方面的应用。     

Infrared Small Target Detection Using PPCA

Probabilistic PCA (PPCA) is an extension of PCA which reformulated PCA in a probabilistic framework. In this paper we propose a infrared small target detection algorithm using PPCA analogous to the face detection scheme using PCA, or known as “eigenface”. By computing the parameters of PPCA, we map the input vector from the image onto a subspace. After reconstructing the vector, the distance between the original vector and the reconstructed one will indicate the possibility of the input being a target. Experimental results show the effectiveness of this algorithm compared with other methods.     

一种可精确控制粒径的SiO2微球合成方法

用改进的种子法合成SiO₂微球. 微球生长过程中连续缓慢添加正硅酸乙酯,使用动态光散射法实时监控微球粒径的增长过程,调节正硅酸乙酯的添加,实现对粒径的精确控制. 为制备禁带位置位于1000 nm 的光子晶体,合成粒径为446 nm的SiO₂微球,微球粒径在4 h内从193 nm 增长到446 nm,远远快于传统种子法,微球粒径与目标粒径偏差为±5 nm. 制得的SiO₂微球被组装为光子晶体,其禁带位置恰好位于1000 nm.     

Resolving Concentrated Particle Size Mixtures Using Dynamic Light Scattering

Dynamic light scattering (DLS) is a technique used for measuring the size of molecules and particles undergoing Brownian motion by observing time‐dependent fluctuations in the intensity of scattered light. The measurement of samples using conventional DLS instrumentation is limited to low concentrations due to the onset of a phenomenon called multiple scattering. The problems of multiple scattering have been addressed in a light scattering instrument incorporating non‐ invasive backscatter optics (NIBS). This novel optic arrangement maximizes the detection of scattered light while maintaining signal quality and allows for measurements of turbid samples. This paper discusses the ability of backscatter detection to accurately determine particle sizes at 1 %w/v sample concentrations and demonstrates the correct resolution of different size populations using a series of latex standard mixtures with known volume ratios. The concentration of 1 %w/v is much higher than can be measured on conventional dynamic light scattering instruments.     

小粒子动态光散射信号的计算机模拟及分析

用计算机模拟了小粒子（０．００１μｍ～１μｍ）的动态光散射信号，并对其进行了分析，同时运用分形几何学（ＦｒａｃｔａｌＧｅｏｍｅｔｒｙ）的理论和概念，对信号的时间复杂性进行了分数维（ＦｒａｃｔａｌＤｉｍｅｎｓｉｏｎ）的计算，得出了它与粒子尺寸之间的关系。     

Fractal Character of Dynamic Light Scattering of Particles

Dynamic light scattering signals from particles, exhibit fractal characteristics. This feature can be used to determine the particle size. The use of the fractal dimension, as a quantitative method to analyze the properties of dynamic light scattering signals from submicron particles, is presented. The analysis is performed directly on the time‐resolved scattered intensity, and the Box Dimensions of light scattering signals of particles with diameters 100, 200, 500 and 1000 nm. The experimental results show that the fractal dimensions of light scattering signals correlate well with particle size. In the submicron size range, the smaller the particles, the larger their fractal dimensions. Compared with the PCS technique, only several hundreds of samples are required in the fractal method. Therefore, the data processing is easily accomplished. However, this method only provides the mean particle size, but not the particle size distribution.     

基于红外特征吸收法的烟草主流烟气中氨浓度检测系统

为了快速、 精确地从卷烟燃烧的主流烟气中求出氨的浓度信息,设计了基于红外吸收的检测系统。根据氨在中红外的特征吸收曲线,系统通过10.4 μm中红外固定波长激光器对准最强吸收峰波长位置。由红外探测阵列获取经被测主流烟气红外光的干涉条纹后,结合光谱数据库及光谱分析算法,由比尔朗伯定律求解主流烟气中的氨浓度。标准光谱数据选自NIST光谱数据库,结合对主流烟气中多种干扰气体的降噪处理,最终完成氨浓度信息的实时显示。实验采用UnicornTM固定波长激光器、 静态傅里叶变换干涉具、 标准抽吸引擎等,对五个不同品牌的卷烟进行测试。每个品牌随机抽取十支,分别采用传统的离子色谱法和本系统进行实验。结果显示,本系统的氨浓度检测与标准值基本一致,同时速度快、 抗干扰能力强。     

Using the T‐Matrix Method for Light Scattering Computations by Non‐axisymmetric Particles: Superellipsoids and Realistically Shaped Particles

Light scattering by non‐axisymmetric particles is commonly needed in particle characterization and other fields. After much work devoted to volume discretization methods to compute scattering by such particles, there is renewed interest in the T‐matrix method. We extended the null‐field method with discrete sources for T‐matrix computation and implemented the superellipsoid shape using an implicit equation. Additionally, a triangular surface patch model of a realistically shaped particle can be used for scattering computations. In this paper some exemplary results of scattering by non‐axisymmetric particles are presented.     

光复散射对消光法粒径测量的影响:复散射模型与数值模拟

复散射效应在光散射颗粒测量中不仅重要．且尚未得到很好解决。采用蒙特卡罗方法,对不同的光波长,颗粒浓度以及收接器条件下的光复散射进行了数值模拟．数值算法程序经与四通量模型进行对比验证,数值结果与单散射条件的郎伯-比尔模型进行比较．进而讨论了复散射效应对消光法颗粒粒径测量影响。表明复散射对消光法颗粒测量的影响不仅取决于颗粒系自身的浓度．而且接收器的几何尺寸和接收位置起着非常重要的作用,减小颗粒介质层厚度和减小光接收器接收面积．增大接收距离以及减小接收角都能减小复散射效应对消光法粒径测量的影响。     

硅微机械悬臂梁红外辐射热探测技术的研究

研究了利用镀膜硅微机械悬臂梁红外辐射热挠曲实现红外辐射探测的技术,建立了镀膜双层硅微悬臂梁红外辐射热挠曲的理论模型.并利用镀有二氧化硅膜层的硅微悬臂梁,在硅微悬臂梁根部制作热挠曲检测压敏电阻,用实验方法测试了硅微悬臂梁对红外辐射的响应规律,结果表明该镀膜硅微悬臂梁对顶端辐射激励的1.5 μm红外光的响应灵敏度可达 2.39 μV/mW.用计算机优化方法得到了硅微机械悬臂梁的最佳镀膜厚度比的规律,为进一步提高硅微悬臂梁红外探测的灵敏度提供了设计依据.     

White-light Detection for Nanoparticle Sizing with the TSI Ultrafine Condensation Particle Counter

Several of the most common methods for measuring nanoparticle size distributions employ the ultrafine condensation particle counter (UCPC) for detection purposes. Among these methods, the pulse height analysis (PHA) technique, in which the optical response of the UCPC detector is related to initial particle diameter in the 3–10nm range, prevails in applications where fast sampling is required or for which concentrations of nanoparticles are frequently very low. With the PHA technique, white light is required for particle illumination in order to obtain a monotonic relationship between initial particle diameter and optical response (pulse height). However, the popular, commercially available TSI Model 3025A UCPC employs a laser for particle detection. Here, we report on a novel white-light detection system developed for the 3025A UCPC that involves minimal alteration to the instrument and preserves normal counting operation. Performance is illustrated with pulse height spectra produced by differential mobility analyzer (DMA) – generated calibration aerosols in the 3–50nm range.     

Geometrical Form Factor Improvement for Receiving System of Infrared Lidar

Improvement of an infrared light detection and ranging (IR-lidar) system for a short range (0–1000 m) and with high resolution is studied to enhance a geometrical form factor. Theoretical modeling of Mie scattering echo signals agrees with the experimental results. Introduction of a lens in front of the detector is effective for increasing the geometrical form factor, and a significant improvement in the received signal intensity is achieved, especially for short-range measurements around 100 m. This is useful for the IR-lidar system with a detector diameter of less than 1 mm. In the theoretical model, a ray-tracing technique was applied and a transmitting laser beam with Gaussian profile was considered for better accuracy.     

火灾烟颗粒的分形结构形状模拟与光散射计算

针对火灾烟颗粒的形状特点，提出并建立火灾烟颗粒分形结构凝团的形状模型，并对烟颗粒扫描电镜(SEM)图像进行分析，获取分形结构模型中的单个凝团中基本颗粒个数、凝团分形维数、基本颗粒半径等参数.利用该模型对火灾烟颗粒的形状进行模拟的结果表明，该模型能够较好反映出烟颗粒的形貌特征.利用形状模型对火灾烟颗粒散射进行初步计算表明，在其他参数相同的情况下，相对于同体积的球形颗粒，分形凝团具有前向散射较弱，后向散射较强的特征.     

罗丹明6G缔合微粒共振散射光谱法测定过氧化氢

在0.020mol.L-1HCl-4.0×10-4mol.L-1KI-1.6×10-5mol.L-1Mo(Ⅵ)介质中,罗丹明6G(RhG)在540nm处有1个荧光峰,在540nm处有1个同步荧光峰。当有H2O2存在时,H2O2与过量的I-反应生成I3-,I3-与RhG形成缔合微粒,在320,400,595nm处产生3个共振散射(RS)峰;而在540nm处荧光峰猝灭。H2O2浓度在0.068~34μg.mL-1范围内与400nm波长处的共振散射光强度呈线性关系。据此建立了一个测定水中H2O2的共振散射光谱分析法。光谱研究结果表明,(RhG-I3)n缔合微粒和界面的形成是导致体系RS增强和荧光猝灭的根本原因。     

米氏理论的近似及在粒度测量中的应用

将夫琅禾费衍射理论与几何散射 (包括折射和反射 )相结合 ,给出平行光入射下圆形颗粒在前向大角度范围内的散射光强分布近似算法。由于考虑了衍射、折射和反射相互间的干涉效应和颗粒对光的吸收性 ,对于正常或非正常衍射状态下无因次参量α≥ 40的耗散颗粒 ,在前向 0°～ 60°散射之内 ,该方法对散射光强计算结果与米氏理论结果是吻合的。由于计算速度比米氏理论快 ,有效角度范围比夫琅禾费衍射理论宽 ,因而适合于大颗粒的前向光强计算。将这一计算方法应用到大角度采光时的激光粒度测量实验中 ,收到了良好的效果     

复杂成分内混合体光散射等效性分析的判据选取

使用离散偶极子近似算法DDSCAT7.1与米散射理论算法MIEV0研究复杂成分混合体等效性时, 由于两者为不同的原理和实现算法, 考察DDSCAT7.1和MIEV0所计算出的相同光学量的相对偏差将非常必要。通过比较两种算法所计算出的球形散射型粒子海盐和吸收型粒子含碳气溶胶的光学量的相对偏差, 结果表明: 两种算法所计算的非散射角函数光学量的相对偏差较小; 在瑞利散射区, 散射相矩阵分量M1和S21的相对偏差较小, 而M2和D21只在一定的散射角范围内相对偏差较小; 在米散射区, M1、M2、S21在有限的散射角范围内相对偏差较小, 而D21的相对偏差则普遍较大。在光散射等效性判据选取时, 非散射角函数光学量适合用来研究内混合体的等效性, 而散射相函数则不太适合用来研究内混合体等效性, 除非综合考虑粒子尺度参数以及选择合适的散射角等因素。在光散射技术中对粒子谱分布和折射率相当敏感的D21, 比较难以用在以两种方法为基础的内混合体等效性研究中。     

生物组织的可见光与近红外光散射模型

对生物组织光学模型尤其是光散射特性进行了研究, 发现可以利用等效粒子数密度的粒度分布更精确地了解生物组织的光散射性质。在夫琅和费衍射近似下, 散射系数和散射相函数可以由等效粒子数密度的粒度分布得到。基于粒子粒度光散射测量技术, 所得结果可给出一种新的可行的测量生物组织光学性质参数的方法。