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121.
采用斯托克斯(Stokes)矢量形式,推导出当无限窄的连续光束垂直入射到混浊介质表面时,后向单次漫散射米勒(Mueller)矩阵的解析表达式。基于米氏(Mie)散射模式,详细分析了单次散射米勒矩阵元素的分布模式,以及与介质粒子数密度,粒子尺寸参量之间的关系。研究表明:单次散射米勒矩阵的方位变化随粒子数密度的增加,逐渐消失,而矩阵元素m22,m33,m23,m32随粒子数密度的变化,具有更显著的方位变化特征。矩阵元素m22,m33在方位角=45°时的值随尺寸参量的变化有一定的规律性,当尺寸参量小于某一特征参量时,其值呈下降趋势,反之则呈波动上升趋势。当介质粒子数密度以及粒子尺寸参量改变时,米勒矩阵元素强度的径向分布模式不变,即在任何方位,强度随径向距离都近似成指数规律衰减,方位变化呈周期性。 相似文献
122.
The formation of complexes and disproportionation of nitrogen oxides (NO, N2O) on cationic forms of LTA, FAU, and MOR zeolites was investigated by diffuse-reflectance IR spectroscopy. N2O is adsorbed on the samples under study in the molecular form and the frequencies of the first overtone of the stretching vibrations ν10–2 and the combination bands of the stretching vibrations with other vibrational modes for N2O complexes with cationic sites in zeolites (ν30–1 + ν10–1, ν10–1 + δ0–2) are more significantly influenced by the nature of the zeolite. The presence of several IR bands in the region of 2400–2600 cm−1 (the ν10–1 + δ0–2 transitions) for different zeolite types was explained by the availability of different localization sites for cations in these zeolites. The frequencies in this region also depend on the nature of the cation (its charge and radius). The data can be explained by the specific geometry of the N2O complex formed, presumably two-point adsorption of N2O on a cation and a neighboring oxygen atom of the framework. Adsorption of CO or CH4 on the samples with preliminarily adsorbed N2O at 20–180 °C does not result in any oxidation of these molecules. NO+ and N2O3 species formed by disproportionation of NO are capable of oxidizing CO and CH4 molecules to CO2, whereas NOx is reduced simultaneously to N2 or N2O. The peculiarities in the behavior of cationic forms of different zeolites with respect to adsorbed nitrogen oxides determined by different density and localization of cations have been established. 相似文献
123.
Enikő Földes Zoltán Szabó Ákos Janecska Gábor Nagy Béla Pukánszky 《Macromolecular Symposia》2003,202(1):97-116
FT-IR spectra of ethylene homopolymers and ethylene/1-hexene copolymers polymerized under different conditions were studied by transmission and diffuse reflection (DRIFT) spectroscopy. The absorbance spectra of film samples were compared with the DRIFT spectra of powders ground from the films. For determining the concentration of the methyl and unsaturated (vinyl, vinylidene and trans-vinylene) groups of polyethylene powders the DRIFT spectra were calibrated by comparing the IR intensities of the corresponding bands measured by the two methods. The results proved that the effect of differences in scattering of the polymer powder originating from the irregularity of the top surface, as well as the size and shape of the particles can be eliminated by the use of a proper internal standard. Linear correlation was established between the logarithms of the normalized intensities measured in absorbance and Kubelka-Munk units. In the case of polyethylene the selection of the internal reference band affects significantly the accuracy of the calibration due to the difference in the refractive indices of the crystalline and amorphous phases. 相似文献
124.
REN Hongwu FANG Zujie 《Chinese Journal of Lasers》2000,9(5):469-474
1 Introduction Theinverse problemsinopticaltomography[1] areconcernedwithdeterminationofopticalpropertiessuchasabsorptioncoeficientsandscatteringcoefficientsfromsurfacemeasurementsofturbidmediairradiatedbylight.Therearelargeamountofsurfacemeasurementst… 相似文献
125.
To deduce the optical properties, the absorption coefficient SmUaand reduced scattering coefficient μ’s, of turbid medium, Lin et al. (Appl. Opt. 34 (1995) 2362) proposed an oblique incidence reflectometry in which the diffusion approximation was assumed. In this paper we propose an alternative method which does not assume the diffusion approximation but uses a Monte Carlo light propagation model. Two features are extracted from the diffuse reflectance distribution detected on the medium surface, and optical properties are then estimated by looking up the predetermined table generated by Monte Carlo simulations. The validity of the proposed method has been confirmed by computer simulations. 相似文献
126.
127.
Effects of Activation Atmospheres on Structure and Activity of Mo-based Catalyst for Synthesis of Higher Alcohols
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Ji-long Zhou Wei Xie Song Sun Li-li Ji Li-rong Zheng Chen Gao Jun Bao 《化学物理学报(中文版)》2016,29(4):467-473
Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H2, syngas (H2/CO=2/1), and pure CO. The catalysts structures were characterized by X-ray diffraction, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic performance for the higher alcohol synthesis from syngas was tested. The pure H2 treatment showed a high reduction capacity. The presence of a large amount of metallic Co0. and low valence state Moφ+ (0<φ<2) on the surface suggested a super activity for the CO dissociation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo4+ and Co2+. The syngas-reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H2 and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Moδ+ on the catalyst's surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols. 相似文献
128.
用人工神经网络-近红外光谱法测定冬虫夏草中的甘露醇 总被引:15,自引:0,他引:15
提出了用近红外漫反射光谱技术快速分析发酵冬虫夏草菌粉中甘露醇含量的新方法。采用比色法测定样品中的甘露醇,其含量范围为8.082%-14.548%。在7501.7-6097.8cm^-1与5453.7-4246.5cm^-1波段,分别采用PCR、PLSR和BP神经网络方法建立了样品近红外光谱的一阶微分光谱与其甘露醇含量之间的相关模型。BP神经网络模型的内部交叉验证误差均方根为0.475,预测误差均方根为0.608,均优于PCR和PLSR的处理结果。这表明,BP神经网络法对非线性检测对象具有较好的建模效果,可用于中药近红外光谱分析的非线性校正。 相似文献
129.
以滇重楼的根茎为实验材料,重楼甾体总皂甙的提取率为评价指标,运用L16(4^5)正交试验,考察了皂甙浸出过程中的浸泡时间、乙醇浓度、超声剂量、粗粉质量与浸泡用乙醇体积之比4个因素在4个水平下的工艺过程,筛选出了最佳提取工艺。实验结果表明:粗粉(0.45mm粒径)用30%的乙醇溶液浸泡36h后,超声30min,粗粉质量与(浸泡)乙醇的体积比1:15为最佳提取条仲,重楼甾体总皂甙的提取率为9.50%。以近红外漫反射光谱技术为在线监控手段,利用模式识别方法对AB-8树脂分离精制过程中的吸附、杂质洗脱和甾体总皂甙解吸洗脱等工艺过程进行了在线质量监控方法研究,建立了优化的质量可控的分离纯化方法。 相似文献
130.
烟草灰分、总挥发酸和总挥发碱的近红外光谱分析 总被引:2,自引:0,他引:2
应用偏最小二乘法(PLS)结合近红外光谱(NIR)对烟草灰分(ash)、总挥发酸(TVA)和总挥发碱(TVB)建立校正模型。烟草灰分、总挥发酸和总挥发碱模型相关系数分别为0.97312、0.96220和0.98050;均方预测残差(RMSECV)分别为0.41227、0.00688和0.09790;预测范围分别为1.74~31.31、0.0570~0.2336和0.042~1.136;通过对模型进行t-检验,在显著性水平大于0.05的条件下,其预测结果与行业标准方法的测定结果对比,结果令人满意。 相似文献