建宁莲子挥发性风味化合物分析

目的 分析建宁莲子中的挥发性风味化合物。 方法 采用顶空固相微萃取-气相色谱-质谱联用技术(headspace solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS),结合热图分析和偏最小二乘-判别分析(Partial least squares Discriminant Analysis,PLS-DA)对莲子挥发性风味化合物进行鉴定及产品差异化分析。 结果 8款建宁莲子中一共鉴定出 93 种挥发性化合物,共有挥发性化合物23种。其中53 种为风味化合物,共有风味化合物17种,主要为醇类、酸类、烃类和杂环类。热图分析结果显示风味化合物被聚类成上、中、下3个区域,8款莲子可以被分为4类。基于 PLS-DA 模型的变量投影重要性(variable important in the projection,VIP)得分对 8款莲子风味化合物进行了判别分析,筛选出 13 种(VIP?1)标志风味化合物,其中双戊烯、己醇、异戊醇和苯乙醇是主要的差异化合物。 结论 研究表明,建宁莲子中风味化合物种类丰富,主要包括醇类、烃类、杂环类和醛类等。风味化合物结合热图与PLS-DA分析可用于莲子产品差异化分析,并为莲子工艺改进、产地区分和育种提供理论支撑和思路。     

Nondestructive determination of soluble solids content and pH in tomato juice using NIR transmittance spectroscopy

The potential of near-infrared (NIR) transmittance spectroscopy to nondestructively detect soluble solids content (SSC) and pH in tomato juices was investigated. A total of 200 tomato juice samples were used for NIR spectroscopy analysis at 800–2400 nm using an FT-NIR spectrometer. Multiplicative signal correction (MSC), and the first and second derivative were applied for pre-processing spectral data. The relationship between SSC, pH, and FT-NIR spectra of tomato juice were analyzed via partial least-squares (PLS) regression. PLS regression models were able to predict SSC and pH in tomato juices. The r _c, RMSEC, RMSEP, and RMSECV for SSC were 0.92, 0.0703°Brix, 0.150°Brix, and 0.138°Brix, respectively, whereas those values for pH were 0.90, 0.0333, 0.0316, and 0.0489, respectively. It is concluded that the combination of NIR transmittance spectroscopy and PLS methods can be used to provide a technique of convenient, versatile, and rapid analysis for SSC and pH in tomato juices.     

无效变量消除法在油菜籽芥酸近红外无损速测中的应用

探索改善油菜籽芥酸近红外预测模型准确度与精密度的方法,利用无效变量消除法（UVE）,对135个油菜籽样品近红外光谱信号进行筛选,并利用筛选后的光谱对油菜籽芥酸含量进行偏最小二乘法交叉验证。结果表明,UVE法筛选变量后建立的芥酸校正模型对未知样品预测结果的准确度和速度显著优于全波长参与建立的芥酸校正模型。散射校正加一阶导数对光谱预处理,UVE法筛选变量,偏最小二乘法交叉验证建立的校正模型效果最好,其预测值与标准值的相关系数R达到0.92,交叉验证预测均方差为2.2。因此,用UVE进行波长选择后建立的近红外模型,能准确快速地对油菜籽芥酸含量进行定量分析。     

Nondestructive Estimation of Fat Constituents of Sesame (Sesamum indicum L.) Seeds by Near‐Infrared Reflectance Spectroscopy

A rapid and efficient method for oil constituent estimation in intact sesame seeds was developed through near‐infrared reflectance spectroscopy (NIRS) and was used to evaluate a sesame germplasm collection conserved in China. A total of 342 samples were scanned by reflectance NIR in a range of 950–1650 nm, and the reference values for oil content and fatty acid (FA) profiles were measured by Soxhlet and gas chromatograph methods. Useful chemometric models were developed using partial least squares regression with full cross‐validation. The equations had low standard errors of cross‐validation, and high coefficient of determination of cross‐validation (R_c²) values (>0.8) except for stearic acid (0.794). In external validation, r² values of oil and FA composition equations ranged from 0.815 (arachidonic acid) to 0.877 (linoleic acid). The relative predictive determinant (RPD_v) values for all equations were more than 2.0. The whole‐seed NIR spectroscopy equations for oil content and FA profiles can be used for sesame seed quality rapid evaluation. The background information of the 4399 germplasm resources and accessions with high linoleic acid content identified in this study should be useful for developing new sesame cultivars with desirable FA compositions in future breeding programs.     

Poly(vinyl alcohol)/poly(vinyl chloride) composite polymer membranes for secondary zinc electrodes

A microporous composite polymer membrane composed of poly(vinyl alcohol) (PVA) and poly(vinyl chloride) (PVC), was prepared by a solution casting method and a partial dissolution process. The characteristic properties of microporous PVA/PVC composite polymer membranes containing 2.5-10 wt.% PVC polymers as fillers were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), capillary flow porometry (CFP), micro-Raman spectroscopy, dynamic mechanical analyzer (DMA) and the AC impedance method. The electrochemical properties of a secondary Zn electrode with the PVA/PVC composite polymer membrane were studied using the galvanostatic charge/discharge method. The PVA/PVC composite polymer membrane showed good thermal, mechanical and electrochemical properties. As a result, the PVA/PVC composite polymer membrane appears to be a good candidate for use on the secondary Zn electrodes.     

SO3体系中碘催化甲烷的选择性氧化反应

在SO3体系中,采用碘系列化合物作为催化剂进行甲烷部分氧化反应的研究.对催化剂进行筛选,考察反应工艺条件的影响,并对反应机理进行探讨.最终确定I2为最佳催化剂,反应的最优工艺条件为:催化剂0.099 mol·L-1,温度T=433K,初始压力P=4.0 MPa,搅拌速度500 r/min.该工艺条件下甲烷转化率可达63.57％,目的产物收率为52.6％,产物选择性82.74％.     

傅里叶变换近红外光谱法应用于聚乙烯树脂的正己烷提取物分析

采用偏最小二乘法(PLS),建立了傅里叶变换近红外漫反射光谱法检测聚乙烯树脂正己烷提取物的数学模型。分析过程选择了最佳光谱预处理方法、谱区范围及主因子数,并使用内部交叉验证对模型进行验证。实验结果表明,当选择最小-最大归一化的光谱预处理方法,谱区范围7 501.8～6 097.9 cm-1和5 025.6～4 597.5 cm-1,主因子数8时定量模型的准确度最好,决定系数(R2)和均方差(RMSECV)分别为0.988和0.416,近红外测定值与标准方法测定值基本一致。对297种牌号共1 251个进口聚乙烯树脂正己烷提取物项目的普查结果表明,聚乙烯树脂正己烷提取物项目的总体安全性较低,属于进口聚乙烯需重点关注的安全卫生项目。     

Determination of the Hydroxyl Value of Soybean Polyol by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy

A rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined by the official method of AOCS Tx 1a-66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares (PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions between 3,150 and 990 cm⁻¹ and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained by the AOCS standard method. A correlation coefficient of R ² = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer, the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation reaction.     

局部加载下中空夹层钢管混凝土的试验研究

对局部受压下的中空夹层钢管混凝土进行试验研究。分别对含内外两层钢管的14个圆形构件和15个方形试件进行试验,试验参数包含:空心率、顶端板厚度、局压面积比。结果表明:局部受压下中空夹层钢管混凝土呈现延性。各试验参数对局部受压中空夹层钢管混凝土短柱的性能和破坏模型有很大影响。最后,提出分析局部受压下中空夹层钢管混凝土承载力的简化计算模型。     

弯曲受力时中空管以及混凝土填充纤维复合管的有限元模型:部分填充优化和杆设计方法

非线性有限元模型的拓展与验证在相关的论文(Son J,Fam A.中空管以及混凝土填充纤维复合管的有限元模型:第一部分——抗弯模型拓展与验证)中已被用于研究部分填充混凝土纤维增强复合材料线杆的抗弯性能。为提高抗弯强度和稳定性,建议采用部分填充厚壁管来降低造价。对不同直径与厚度比以及不同分层结构的悬臂单杆进行混凝土部分填充长度优化。研究发现,当下列任意一种情况出现时,优化长度会减少:当直径与厚度比变小时;当纤维角度相对于弯曲管纵向轴夹角增加时;当弯曲管中纵向纤维减少时;当采用侧向分布荷载代替端部集中荷载时。建立了计算中空管和混凝土填充FRP管承载力矩的简单表达式,基于同时发生在中空管和混凝土填充管处的破坏,结合简单的设计方法体系来优化混凝土填充管的长度。同时提出了计算锥形线杆的程序。