Computation of Scattering of Electromagnetic Waves from Absorbing Coating Using the Finite Difference Time Domain Method     

Yu Jihui Tang Cuifeng Huang Jian 《保鲜与加工》1998,(6):35-40

In this paper,we derive the necessary extension to the FD TD(finite difference time domain) method for absorbing coating of composite material.The scattering of electromagnetic waves(EW) from absorbing coating is considered,and the comparision of obtained results with exact analytic ones shows that the method used in this paper is correct and available.  相似文献   

HPLC-ELSD法测定啤酒糟酶解物中低聚木糖     

邓元元  胡超  兰时乐 《中国农学通报》2019,35(1):134-143

为建立啤酒糟酶解物中低聚木糖HPLC-ELSD检测方法,将啤酒糟酶解物用纯水提取,色谱柱为COSMOSIL Sugar-D分析柱(250 mm×4.6 mm,5μm),流动相为乙腈-水(69:31,V/V),流速为0.9 mL/min,柱温40℃,进样量3μL,Evaporator Temperature为78℃,载气流速为1.6 L/min,载气压力为0.5 MPa,采用峰面积外标法定量检测低聚木糖含量。结果表明,木二糖～木五糖分别在0.024～0.245 mg/mL质量浓度范围内呈良好的线性关系,检出限分别为0.0245、0.0245、0.02425、0.024 mg/mL,定量限分别为0.0907、0.0907、0.08981、0.8889 mg/mL,RSD分别为0.203%、0.224%、0.233%、0.252%,样品加标回收率为97.31%～99.83%。该方法具有灵敏度高、重复性好等优点,可用于啤酒糟酶解物中低聚木糖的检测。  相似文献   

基于4-苯基氨基硫脲的Hg2+共振瑞利散射分子受体的合成与研究     

张腊梅  鲍金欣  杨睿 《西南大学学报》2013,35(5)

设计合成了受体分子1,2-二(4-苯基氨基硫脲)乙烷(BPSE),采用1HNMR和13CNMR对分子结构进行了表征.考察了乙腈中受体分子BPSE的光学性质对金属离子的响应,结果发现受体分子BPSE对汞离子表现出显著的共振瑞利散射光谱(RRS)增强,其增强倍数可达550倍,检出限为3.7×10-7 mol/L,具有较高的选择性和灵敏度.同时受体分子可应用于乙腈与水的缓冲溶液中汞离子的识别.  相似文献   

基于近红外光谱多种预处理的胡杨叶片含水量预测对比     

王涛    白铁成    朱彩蝶  高贤强  邬欢欢 《西北林学院学报》2020,35(5):173-179

通过比较5种不同光谱预处理方法（MSC、SNV、VN、一阶导数、二阶导数）提取胡杨叶片近红外光谱信息,分别采用遗传算法(GA)和连续投影算法(SPA)筛选特征波段,建立并比较偏最小二乘回归(PLS)模型对水分含量的预测效果,研究了胡杨叶片水分含量与叶片光谱信息的关系。结果表明,基于5种预处理方法使用SPA-PLS回归模型预测的相关系数R分别为0.764 4、0.869 79、0.806 01、0.779 93、0.816 8;预测均方根误差(RMSEP)分别为0.017 87、0.014 491、0.018 547、0.020 228、0.018 089;所选取的特征波段个数分别为11、20、24、18、18,较GA-PLS选取的特征波段数少,且预测效果普遍优于GA-PLS,其中基于SNV的预测结果最好。研究表明,基于近红外光谱数据,SPA算法相比于GA算法具有更好的选择特征波长能力,并且SPA-PLS算法的回归预测结果普遍优于GA-PLS,采用SNV-SPA-PLS方法可实现胡杨叶片水分含量的快速检测。  相似文献   

Impact of pre-germination on amylopectin molecular structures,crystallinity, and thermal properties of pre-germinated brown rice starches     

《Journal of Cereal Science》2017

Ungerminated brown rice (UGBR) and pre-germinated brown rice (PGBR) obtained from different pre-germination durations were studied to investigate the changes in total starch contents of flour, amylopectin molecular structures, crystallinity, and thermal properties of starches as affected by pre-germination. Each paddy of three rice cultivars with different amylose contents (RD6, waxy; KDML105, low amylose; and RD31, high amylose) was soaked in water at 30°C for 12 h and incubated over different periods until the three stages of embryonic growth length (EGL) were achieved. The total starch contents of three-stage PGBR flour from all rice cultivars decreased when pre-germination durations were increased. The three-stage PGBR starches from the three rice cultivars had lower weight-average molecular weight (Mw) and number-average molecular weight (Mn) than UGBR starches. All starches from the three rice cultivars displayed an A-type X-ray diffraction pattern (XRD). Isolated UGBR starch from RD6 had the highest (31.33%) relative crystallinity (RC), while RD31 showed the lowest RC (26.79%). The slight increases in the RC of three-stage PGBR starches from three rice cultivars were found after pre-germination. Isolated PGBR starches from the three rice cultivars had higher gelatinization temperatures and enthalpy, but lower retrogradation enthalpy and %retrogradation than UGBR starches.  相似文献   

双极化SAR影像的分类研究     

崔建楠  邢立新  叶超  高志勇 《安徽农业科学》2015,(4):356-359

合成孔径雷达(SAR)遥感数据的穿透性,可以反应亚表层的结构信息等特点,对地表景观分类有特殊的作用.通SAR究地物后向散射和极化等特性,可以反映地物的粗糙度、含水量等特点,用于土地利用调查有很好的效果.文章重点研究了双极化SAR数据特性与数据处理,利用决策树分类、K-means分类方法对吉林西部松原地区进行土地利用分类,并与Landsat 8数据的分类结果进行对比分析.结果表明,基于地物极化特性的双极化雷达数据分类结果明显优于光学遥感影像.  相似文献   

北京沙尘天气期间气溶胶光学特性分析     

赵松林  邓梅  赵辉  廖柏林  王雪琦  李瑶  苏仲铭 《农业灾害研究》2020,10(2):80-83

利用全球地基气溶胶观测网(AERONET)资料,分析了北京地区2001—2013年沙尘天气期间气溶胶的光学特性。结果表明,北京沙尘天气期间受沙尘粒子的影响,气溶胶光学厚度值(AOD)较大,且随波长增大而减小,在波长440 nm处平均值约为1.2;气溶胶Angstrom波长指数97.62%都聚集在0.7以下,说明北京沙尘天气期间粒子较大;沙尘天气期间单次散射反照率随波长增加而增加,平均值约为0.93;复折射指数实部在波长675 nm处最大,平均约为1.55,虚部在440 nm处最大,平均值达到0.006;总的不对称因子平均值约为0.72;北京地区沙尘天气期间气溶胶粒子谱型呈双峰分布,且以粗模态粒子为主,其峰值随光学厚度的增大而增大,粗模态粒子的峰值半径平均约为2.6μm。这些参数对于深入研究沙尘气溶胶的辐射效应和气候效应都是必不可少的。  相似文献   

Impact of Experimental Factors in Soil Phosphorus Tests: Shaking Vessel,Filtration, and Centrifugation     

《Communications in Soil Science and Plant Analysis》2012,43(9-10):1610-1623

In the analysis of Mehlich III, deionized water (DI), Bray, and Olsen soil phosphorus (P) extractions, variations in shaking vessel, centrifugation, and filter paper result in different soil test P (STP) values. Of these factors, centrifugation and type of filtration were found to have the greatest impact on the results of water‐extractable P (WEP), that is, extraction with DI. Further spectrophotometric experiments demonstrated that centrifugation removed fine soil particles from the extract. Without the commonly used 0.45‐µm filters or centrifugation, these particles scatter the radiation of the spectrometer. During colorimetric analysis, this scattering of radiation will be perceived as absorption. This misperception results in a falsely high STP. In WEP analysis with only qualitative filtration, the scattering is very significant and appears to be due to limited aggregation of soil particles in the low ionic strength extract.  相似文献   

定位中心距超常变化下的钻夹具设计     

曾文华  张舒 《林业机械与木工设备》2012,(11):45-47

设计了一款用于通用小型汽油发动机下箱体加工时定位中心距超常变化下的钻夹具,该产品满足了生产要求并获国家发明专利.  相似文献   

多重光散射技术及其在农药制剂稳定性研究中的应用     

冯建国  张小军  何羽薇  陈光斌 《农药科学与管理》2014,35(12):56-59

多重光散射技术通过穿透力极强的近红外脉冲光源对样品扫描,快速、准确分析悬浮液、乳状液和泡沫液等体系的内部变化情况,有利于体系物理稳定性的研究,被广泛应用于食品、医药和石油等领域。随着交叉学科的快速发展,多重光散射技术在农药制剂加工中的应用越来越多,为农药水基化制剂的研究和开发提供了有效途径。  相似文献