蜂蜜中果糖和葡萄糖近红外检测的差异性分析及优化研究

采集了来自全国20种单植物源和其它多植物源的101份的蜂蜜样品,分别运用傅立叶型近红外光谱仪采用光纤透反射(800～2500nm,2mm光程)和透射(800～1370nm,20mm光程)采集方式获得近红外光谱,来预测蜂蜜中结构和含量都很相近的果糖和葡萄糖含量。结果发现,两种测量方式下果糖、葡萄糖的预测准确度存在着较大的差异。为了分析这种差异产生的原因,采用支持向量机分析其非线性信息,采用遗传算法分析其特征波长,结果表明:这种差异主要来自两种糖分特征波长分布不同所导致。通过对两种糖分的检测方案进行优化,得出在利用近红外光谱技术检测蜂蜜中葡萄糖成分含量时应尽量采集短波区、长光程的光谱,或者对全谱区、短光程的光谱,进行特征波长的提取,避开水分的干扰,从而提高其预测精度;而对于果糖,则应尽量采集全谱区、短光程的光谱;采用常用线性定量建模方法PLSR就可以得到很好的预测模型,非线性的支持向量机模型未能明显提升模型性能。     

Structural Characterization and Retention Time Prediction for Components of Essential Oil of Meconopsis Integrifolia Flowers

A molecular structural characterization (MSC) method called reduced molecular electronegativity-distance vector (MEDVR) was used to describe the molecular structures of 55 components of meconopsis integrifolia flowers. By use of stepwise multiple regression (SMR) and partial least square (PLS) methods, a model with the correlation coefficient (R1) of 0.987 and the standard deviation (SD1) of 1.377 could be obtained. Then through multiple linear regression (MLR), another model with the correlation coefficient (R2) of 0.989 and standard deviation (SD2) of 1.395 could be constructed. Furthermore, in virtue of variable screening by the stepwise multiple regression technique (SMR), 8 vectors were selected to build up another model with its correlation coefficient (R3) and standard deviation (SD3) of 0.989 and 1.366, respectively. Then all the three models were evaluated by performing cross-validation with the leave-one-out (LOO) procedure, and the correlation coefficients (QCV) were 0.981, 0.976 and 0.979, respectively. The results show that the models constructed could provide estimation stability and favorable predictive ability.     

天然黄酮类化合物清除羟基自由基的活性研究

采用分光光度法测定了黑沙蒿中黄酮类化合物清除羟基自由基的能力,以IC50值作为评价指标,初步探讨了黄酮类化合物清除羟基自由基的活性与结构之间的关系,为开发利用黑沙蒿提供了科学依据.     

Modulation instability of an intense laser beam in an unmagnetized electron–positron–ion plasma

The modulation instability of an intense circularly polarized laser beam propagating in an unmagnetized, cold electron–positron–ion plasma is investigated. Adopting a generalized Karpman method, a three-dimensional nonlinear equation is shown to govern the laser field. Then the conditions for modulation instability and the temporal growth rate are obtained analytically. In order to compare with the usual electron–ion plasmas, the effect of positron concentration is considered. It is found that the increase in positron-to-electron density ratio shifts the instability region towards higher vertical wave numbers but does not cause displacement along the parallel wave number direction, and the growth rate increases as the positron-to-electron density ratio increases.     

计算波状表面半透明流体层光谱反射特性的光线分裂跟踪法

提出一种计算具有波状表面的半透明流体层光谱反射特性的光线分裂跟踪法.对平行入射和漫入射光谱分别采用正向和反向跟踪计算,实现了对光线的分裂跟踪.该方法计算思路简捷、速度快、需用内存小,对此类问题的求解有良好的适应性.算例结果表明,表面的波状弯曲降低了流体层对漫入射光谱的反射能力;但对平行入射光谱,呈现出两种相反的影响.     

内灰化八面体核壳乳剂的制备方法对微晶结构与性能的影响

应用双注仪制备了碘含量1.5%的AgBrI乳剂,在一定温度,pAg和pH下将乳剂成熟到一定程度(D₀>5.0).用此乳剂做为核,采用二次乳化法包壳。本文主要研究了包壳时pH值,壳的组成,厚度对乳剂颗粒大小、形状、显影密度及离子电导的影响。结果表明:(1)当壳的组成为AgBrI时,随氯含量增加(分别为0、2.5、5、10%mol),核壳乳剂表显密度变化不大而内显密度上升;(2)包壳时随pH由低到高(pH为2、4、6、8),乳剂颗粒由小变大。颗粒形状由规整八面体变得棱角模糊,均匀度下降,表显密度由小变大,而内显密度由大变小;(3)在相同pH下包壳,随壳厚度的增加(壳与核卤化银的摩尔数比为:1:0.5,1:1,1:2,1:3)表显密度急剧下降,内显密度变化不大;(4)随包壳时pH增加,卤化银微晶的离子电导增大.     

Solution of the plane stress problems of strain-hardening materials described by power-law using the complex pseudo-stress function

In the present paper,the compatibility equation for the plane stress problems of power-law materials is transformed into a biharmonic equation by introducing the so-calledcomplex pseudo-stress function,which makes it possible to solve the elastic-plastic planestress problems of strain hardening materials described by power-law using the complexvariable function method like that in the linear elasticity theory.By using this generalmethod,the close-formed analytical solutions for the stress,strain and displacementcomponents of the plane stress problems’of power-law materials is deduced in the paper,which can also be used to solve the elasto-plastic plane stress problems of strain-hardeningmaterials other than that described by power-law.As an example,the problem of a power-law material infinite plate containing a circular hole under uniaxial tension is solved byusing this method,the results of which are compared with those of a known asymptoticanalytical solution obtained by the perturbation method.     

CS2在Ag-S键中的插入反应的研究(PPh3)2 Ag(S2CSBu^t)

白色的[Bu^tSAg]nPPh3溶于CS2中, 析出桔黄色晶体. 经X射线单晶结构分析其结构为(PPh3)2Ag(S2CSBu^t). 发现了一个CS2在Ag-S键中的插入反应. 此反应为可逆反应, 晶体在120-130℃失去CS2. 晶体属三斜晶系, 空间群P1,a=10.571(1), b=13.638(3), c=14.391(3)A, α=88.75(2), β=72.84(1), γ=80.58(1)°, V=1954.9A^3, Dc=1.36g/cm^3, Dm=1.36g/cm^3, Z=2. 3572个衍射点参与修正, R=0.045, Rw=0.043, Ag原子以变形四面体与硫代黄原酸配体Bu^tS-CS2的两个S原子及两个PPh3的P原子配位. 插入反应形成的CS3基团基本上共面, 其C-S键长比CS2中的键长明显加长, 而比单键的C-S键长要短, 并在红外光谱上出现特征吸收峰.     

近红外光谱法测定蜂蜜中主要成分的可行性研究

以153个单植物源和混合植物源蜂蜜样品为研究对象,使用３种近红外光谱仪(FT型、CCD型、PDA型)采集蜂蜜的透反射和透射光谱,并应用近红外定量分析技术进行蜂蜜中主要成分(水分含量、果糖含量、葡萄糖含量)的检测研究。用偏最小二乘回归(partial least square repression, PLSR)方法分别建立了蜂蜜水分含量、果糖含量、葡萄糖含量的近红外定量分析模型。结果表明,水分含量、果糖含量、葡萄糖含量的相关系数(r)分别达到0.978 5, 0.931 1和0.890 7,预测误差均方根(RMSEP)分别为0.410 8(%), 1.914 4(%)和2.531 9(%)。研究表明基于近红外光谱的蜂蜜主要成分快速无损检测准确度高,具有很高的实用价值。     

有限注意力下一类满意启发式决策的建模与理性分析

在决策者有限注意力下,现实生活中决策人的选择行为往往表现出一类“满意启发式”特征。基于个体决策者偏好的不完备性,借助方案集系列、考虑集等相关概念探讨了满意启发式决策规则的建模;论证了方案集系列可观与部分可观条件下一类满意决策函数的存在性,以及基于相关理性条件的理性特征,并结合顾客购买行为案例的仿真实验对所建立的满意决策模型进行了验证。仿真结果表明决策者在时间紧逼和信息不完整的情形下可以通过排除部分方案的方式保证以最大概率选到满意方案。研究结果可为现实生活中决策人在时间紧迫、信息缺失等情形下的选择提供一定的理论参考与指导,也可作为一类满意决策研究的理论基础。