空间分辨漫反射的一阶散射参量灵敏度

以输运理论的P3近似为基础,推导了空间分辨漫反射的一阶散射参量灵敏度的解析表示,并进行了数值分析,比较了散射参量对P3近似和漫射近似漫反射的影响.结果表明:在距光源两个输运平均自由程以内,该灵敏度与相应于漫射近似的灵敏度差别较为明显;距离光源约四个输运平均自由程附近,该灵敏度等于零,并且与光源之距与相应于漫射近似情况也...     

基于最小二乘支持向量机回归的背景偏振光谱二向反射分布建模分析

详细分析了土壤背景偏振光谱二向反射分布函数与探测角及探测方位角之间关系.提出了基于最小二乘支持向量机回归的偏振光谱二向反射分布函数建模,将有限实验观测条件下测量得到的少数偏振光谱二向反射分布函数扩展到2π空间范围内任意入射及观测条件.通过模型结果和实验结果分析比较,表明该模型能很好地满足准确度要求.     

Inverse transient radiation analysis in one-dimensional non-homogeneous participating slabs using particle swarm optimization algorithms

Particle Swarm Optimization (PSO) algorithms, including standard PSO, Stochastic PSO, and Multi-Phase PSO, are applied to solve the time-domain inverse transient radiation problems in the present research. Time-resolved transmittance and reflectance signals of four different measuring models serve as the measurement data, which estimate absorption, scattering coefficients, and geometric position within one-dimensional non-homogeneous media by inverse simulation. To check retrieval performances and accuracies of PSO-based approaches, four different inverse transient radiation cases are investigated to deal with one homogeneous layer, two-layer, three-layer, and continuous non-homogenous media. The influences of different searching ranges, swarm sizes, and maximum fly velocities on the fitness function of PSO are discussed. Meanwhile, the effects of measurement errors on the reconstruction accuracy are also investigated. All the results confirm that radiative parameters could be estimated accurately with measurement noise using PSO-based approaches.     

激光辐照环境对金属材料反射特性的影响

 利用积分球绝对测量法,对在20 Pa真空缺氧、1 000 Pa空气,10⁵ Pa空气及1 000 Pa氧气环境下,1 064 nm波长连续激光辐照30CrMnSiA碳钢材料过程中的反射光信号进行了测量,得到了30CrMnSiA碳钢在4种辐照环境下的反射率和温度变化曲线。结果表明：在空气组分辐照环境的低压到10⁵ Pa范围内,材料初始反射率随压力增大而增大;在缺氧和富氧环境的激光辐照过程中,缺氧环境下材料反射率变化缓慢,且变化拐点温度高于富氧环境,富氧环境下材料被加热后的快速氧化反应有利于材料对激光能量的吸收;不同辐照环境（缺氧和富氧）相同材料温度条件下,材料反射率并不相同。     

生物组织的δ-P1近似漫反射光学模型

本文研究了生物组织的改进的δ-P₁近似漫反射光学模型,推导了含有等效光源一阶矩的双点源近似空间分辨漫反射解R_δ－P1(ρ).研究表明,考虑等效光源一阶矩的光学模型,较好地描述了具有强的前向散射特性和较大吸收系数的生物组织散射特性;与漫射近似下的漫反射率R_SDA(ρ)相比,新的光学模型能较好地描述光源附近的漫辐射强度分布,并且由于解析表达式中含有散射相函数的二阶参量γ,这对 关键词： 组织光学 1近似')" href="#">δ-P₁近似 等效光源 微区漫反射     

激光作用下环氧/硅树脂复合涂层的1.3μm反射特性研究

利用共轭反射计装置,开展了真空环境中激光作用下环氧/硅树脂双层结构复合涂层的1.3μm反射特性研究,测量得到了涂层反射率随样品背表面温度的变化曲线。通过有限元分析和界面热阻修正得到了反射率随涂层温度的变化关系,探讨了反射率随温度的变化机理。研究结果表明,红外连续激光损伤环氧/硅树脂复合涂层,主要表现为底漆热解引发的鼓包分层和面漆热解导致的烧蚀变色;常温下涂层对1.3μm激光的反射率约为0.80,激光辐照初始时变化不明显,鼓包前后出现波动,测量区涂层鼓包、烧蚀后反射率显著下降,最终保持在一个相对较低值;反射率变化与涂层热解过程、损伤方式密切相关,涂层对1.3μm激光的反射率变化存在3个特征温度,分别对应底漆热解、面漆热解和表面状态趋于稳定时的温度。     

基于HJ-1-CCD数据的地表反射率反演与验证

环境一号卫星OCD相机(HJ-1-CCD)30m的空间分辨率在地物识别中具有潜在优势,然而由于缺少短波红外通道,利用暗像元法反演地表反射率较为困难.基于北京与珠三角地区的地物光谱试验,获得暗像元的植被指数与红、蓝波段反射率比值,构建基于辐射传输模型的大气校正算法.为了验证算法精度,将北京地区卫星反演值与实测的草坪、水体...     

The influence of various dielectric parameters on the reststrahlen region of SiC

The reststrahlen region of SiC is analysed with the goal of establishing the origin of different shapes of this band, by varying the dielectric parameters involved when simulating the reststrahlen region as obtained by infrared reflectance.     

Characterization of lead and lead leaching properties of lead glazed ceramics from the Solis Valley, Mexico, using inductively coupled plasma-mass spectrometry (ICP-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)

Ingestion of relatively small amounts of lead is now recognized to cause significant neurological and cognitive effects in humans. Large quantities may be fatal, yet lead poisoning, especially of children, is still a major public health concern in many parts of the world. In rural Mexican communities lead oxide (PbO) is added to ceramic glaze as a fluxing agent, lowering starting firing temperatures to 500 °C. The purpose of this study is to characterize the lead chemical forms in ceramic glazes from the Solis Valley, Mexico, to investigate lead leaching properties of these ceramics, and to demonstrate the applicability of lead isotope signatures as a means of tracing lead source origins. Ceramics were collected from the rural village of Santa Maria de Canchesda, State of Mexico, Mexico. Dried liquid glazes, post-fired glaze material, and pure PbO were analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). Results from DRIFT analysis indicate that PbO (1429 cm⁻¹ band) is the active form of lead found in liquid glazes and ceramics. Some shifting of 1429 cm⁻¹ PbO peak to lower wavenumbers occurs in post-fired ceramics, and this may be due to the formation of lead bisilicate during firing. Ceramics samples were leached in 0.02 M citric acid solution for 1 min, and leached lead concentrations were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Lead concentrations in these leachates varied from 0.4-80.4 μg ml⁻¹, while the control pottery from the US leached only 0.1 μg ml⁻¹ lead. Elemental distributions on glaze surfaces were identified by laser ablation (LA)-ICP-MS. Nitric acid extracts of soils, teeth, and ceramic glazes were analyzed for lead isotope ratios (²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb) using ICP-MS. Similarities of tooth and ceramic lead isotope ratios indicate that ceramics may be a substantial source of body lead burden in the Solis Valley. This study demonstrates the applicability of lead isotope ratios for lead source identification, and it identifies potential health risks from ceramic use induced lead toxicity within the Solis Valley.     

Determination of the Asymmetry Parameter and Scattering Coefficient of Turbid Media from Spatially Resolved Reflectance Measurements

We present a technique for determining the asymmetry parameter and scattering coefficient of turbid media from spatially resolved reflectance measurements. This technique will contribute to the development of medical applications in which it is necessary to predict the distribution and propagation of light in tissue. Based on Monte Carlo simulations, we derived correlations which relate the reduced scattering coefficient and the asymmetry parameter to the relative reflectance curve. Initial estimates of the optical properties are obtained from these correlations. Final values are obtained by adjusting the optical parameters and repeating the Monte Carlo simulations until the simulated reflectance pattern matches the measured reflectance pattern. Preliminary experimental results indicate that this technique can be used to determine the asymmetry parameter to within 10% and the reduced scattering coefficient to within 5%.