太赫兹光谱结合特征谱区筛选算法在发动机润滑油含水量定量分析中应用研究

发动机润滑油是保障汽车发动机持久且稳定运转的基石,准确评定发动机润滑油各项性能指标是其在生产到使用全过程必不可少的步骤。发动机润滑油在一段时间的使用后会因为多种原因引起油品变质,发动机润滑油变质的指标可以用其中非磁性颗粒物浓度、金属屑含量、pH值、粘稠度、含水率等表述。关于发动机润滑油含水量的检测,传统的检测方法存在操作复杂,及时性差等缺点。太赫兹对水吸收强烈,适合用于对样品中微水含量的分析。通过透射式太赫兹时域光谱系统获得1.0～3.5 THz下的六种不同水含量的发动机润滑油的吸收系数谱线,对谱线进行Savitzky-Golay（SG）平滑去噪,剔除奇异样本后,采用Kennard-Stone算法划分样品集,尝试常规区间偏最小二乘法（iPLS）、向后区间偏最小二乘法（BiPLS）和联合区间偏最小二乘法（SiPLS）对其太赫兹时域光谱特征谱区间进行筛选,着重研究区间间隔数、PLS组件数、最佳主因子数和区间选择等因素对PLS模型属性的影响,并且对不同含水量的润滑油建模分析,对不同模型比较选优,建立最优定量分析模型。建模结果表示特征谱区筛选可以提高建模性能、降低模型复杂性,特征谱区筛选算法通过剔除发动机润滑油太赫兹吸收系数谱线中非线性或者无关变量的方式,使建模结果更好的表达吸收系数谱线与其含水量的关系。结果表明：采用BiPLS模型用于发电机润滑油中微量水含量的定量分析时建模效果最佳,模型区间数为26,入选区间为[18 10 4 3 8 12 5 11 24 13 16 21 2],主因子数为10,最优模型的交互验证均方根误差RMSECV为0.003 5,预测均方根误差RMSEP为0.004 6,校正集相关系数r为0.919 3,预测集相关系数r为0.865 7。由此可见,可以采用反向区间偏最小二乘法（BiPLS）用于发动机润滑油水含量的测定,且实验过程简单,建模计算速度快,效果理想,可以适用于非接触式油品含水量的定量分析。     

基于PCA的土壤Cd含量高光谱反演模型对比研究

土壤重金属污染对人类健康造成了极大的威胁,如何快速摸清土壤污染情况尤为重要。高光谱遥感具备光谱分辨率高,快速无损等优势,使其在土壤组分反演方面具有巨大的潜力。针对高光谱信息冗余及光谱变换对土壤镉（Cd）含量估算的影响进行分析,并利用变换前后的高光谱数据对比研究了不同高光谱模型对土壤Cd含量反演的性能。首先利用等离子体质谱法和FieldSpec4地物光谱仪收集了56组土壤样品的Cd含量和对应的高光谱曲线（350～2 500 nm）;为了弱化光谱测定中光亮变化和土壤表面凹凸对实验结果的影响,研究对高光谱数据进行倒数对数预处理;考虑到高光谱数据中存在大量的信息冗余,研究采用了主成分分析（PCA）对高光谱数据进行降维处理并最终保留了前12个主成分量作为特征变量。针对高光谱反演模型,研究选择了偏最小二乘（PLSR）、支持向量机（SVM）、人工神经网络（ANN）和随机森林（RF）四种回归模型建立PCA主成分与Cd含量之间的关系;最后,研究选取了决定系数（R2）、均方根误差（RMSE）和RPD三种精度评估指标评估回归模型的拟合精度,结果表明针对光谱采用PCA波段降维的方法处理后,选取的12个主成分对变化前后的光谱累计贡献率均达到99.99%,作为模型的输入变量,四种模型均具有一定的预测能力。无论光谱变换与否,PCA-RF反演模型的预测能力均为最好（R2分别为0.856和0.855,RPD均高达3.39）。利用PCA对高光谱数据降维处理可以有效降低高光谱数据冗余,有力的保证模型的预测能力。以PCA筛选出的主成分量可以作为模型极好的输入变量,以RF为基础的高光谱反演模型在反演土壤Cd含量时具有最佳效果,可为该区域及类似地区的土壤重金属污染物反演提供新的方法支撑。     

Determination of Chloride Content in Different Types of Cement Using Laser-Induced Breakdown Spectroscopy

The characterization and accurate determination of the chloride content in cement/concrete is very important for the assessment of the durability and safety of a concrete structure. The available analytical techniques are relatively expensive and time consuming. In this study, a laser-induced breakdown spectroscopy (LIBS) system was used for determination of elemental composition in three different types of cement samples. The plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm on the cement samples. The concentrations of different elements of significance for structural stability in cement samples were determined. The evaluation of the potential and the capabilities of LIBS as a rapid tool for characterization of cement samples is discussed. The optimum LIBS setup and experimental conditions to detect and measure chloride in building materials are reported. The LIBS results were compared with the results obtained using a standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP–ES). The limits of detection were determined, and calibration curves were measured. The results of this investigation indicate the reliability of LIBS to characterize different cement samples and to assess the chloride content in these cements.     

Group Theoretical Analysis of the v 1 (CO 3 2-) Vibration in Crystalline Calcium Carbonate

A group theoretical analysis, based on the correlation method, is presented for the symmetric stretch vibration of the carbonate ion in three crystalline forms of calcium carbonate: calcite, aragonite and vaterite. Numbers of Raman and infrared active components are calculated and compared with experimental data, including those from a recent Raman study of vaterite. It is shown that the splitting observed for v _l in vaterite is compatible with two of the proposed crystal structures for this compound.     

Combined effects of high pressure and sodium hydrogen carbonate treatment on pork ham: improvement of texture and palatability

In this study, the combined effects of high pressure and sodium hydrogen carbonate (NaHCO₃) treatment on the physical and chemical properties, and palatability of pork ham, a tough and under-utilized meat, were investigated. Assessment of meat properties with heat treatment, after exposure to NaHCO₃ and high pressure treatment, revealed an increase in water content, and decreased weight reduction and rupture stress. The free amino acid content of meat samples increased with NaHCO₃ and high pressure treatment. The effect of high pressure processing was especially notable at a pressure of 300 MPa. Sensory evaluation showed that meat subjected to high pressure processing after NaHCO₃ treatment was tender and juicy. In addition, the sample produced minimal residue in the mouth and was characterized by a good taste.     

纳豆菌细胞包埋材料的选择

以海藻酸钠（SA）和聚乙烯醇（PVA）为包埋材料，采用固定化细胞技术对纳豆菌生产纳豆激酶进行了研究。研究发现，在PVA中加入SA进行细胞包埋可获得渗透性能好强度高的固定化细胞，通过正交试验进一步确定：当PVA的浓度为11％，SA的浓度为1％，硼酸的浓度为5％，CaCl2的浓度为6％时，固定化细胞的强度最好，可反复使用6批次，活性也很高，产生的纳豆激酶酶活溶纤圈直径积达88mm^2／15μL。     

在甲烷氧化偶联反应中碱、碱土、稀土金属氧化物之间的相互作用 Ⅱ.掺CaO的La_2O_3和掺La_2O_3的CaO催化剂的催化性能

报导了非Li催化剂CaO-La_2O_3和La_2O_3-CaO的催化性能。甲烷氧化偶联反应的活性测试表明:以共沉淀方法制备的CaO-La_2O_3催化剂除了具有较好的C_2选择性外,其活性明显高于其它样品,而且适用于较大的空速条件(100000h~(-1)),是一个有应用前景的催化剂。但这类催化剂表现出明显的热点效应。用XRD,SEM等技术研究了相应催化剂体系的晶胞参数变化规律以及颗粒分散程度,并同其催化性能进行了关联。     

流化床煤气化炉内脱硫的研究Ⅰ．台式流化床煤气化的炉内脱硫试验

采用台式流化床煤气化装置，研究了影响炉内脱硫效率的因素。炉内脱硫对高硫煤特别有效，脱硫效率可达９０％以上。所采用的二种石灰石和一种白云石脱硫效率相近，按Ｃａ／Ｓ比比较则白云石稍好些。虽然脱硫效率随Ｃａ／Ｓ比增加而增加，但当Ｃａ／Ｓ比达到３后几乎不再增加。存在一个最佳脱硫操作温度。在非焙烧区，脱硫率随压力增加而下降，而在焙烧区脱硫率和压力几乎无关。测定了脱硫剂脱硫前后的孔容积分布，发现脱硫之后１～３０ｎｍ的孔容显著减少。     

Heat Content Asymptotics for Oblique Boundary Conditions

We consider the short-time heat content asymptotics for oblique boundary conditions. The first few coefficients in the asymptotic expansion are calculated.     

原子物理学课程的教学改革与实践

文章首先对原子物理学课程进行定位，指出原子物理学是普通物理的一部分，它属于近代物理，并概述了原子物理学课程的特点；文章接着对原子物理学课程的教学体系与教学内容的改革方面的一些重要问题分别进行了讨论；文章最后详述了原子物理学的教学改革与实践以及在教学中培养分析问题和解决问题的能力方面的尝试。