基于KPCA和近红外光谱的鉴别玉米单倍体方法研究

玉米的单倍体鉴别技术对玉米单倍体育种技术非常重要。近红外光谱分析技术以其操作简便,可在线分析监测,速度快,无损,测试成本低等特点在农业领域备受关注,应用广泛。实验首先通过美国JDSU公司的近红外光谱仪采集由国家玉米改良中心提供的玉米种子单倍体、多倍体的近红外光谱数据,然后对获得的原始数据做平滑(smoothing)、一阶导(first derivative,FD)和矢量归一化(vector normalization,VN)预处理以消除其噪声影响,再采用核函数为高斯核函数(Gaussian kernel function)的核主成分分析(kernel principal components analysis, KPCA)的方法将玉米种子的近红外光谱数据映射到高维空间中,并对映射后的数据做非线性特征提取,然后应用支持向量机(support vector machines, SVM)对提取的玉米种子单倍体、多倍体光谱数据的非线性特征建立分类模型,最后输入测试数据进行玉米单倍体、多倍体的分类鉴别测试,预测玉米种子是否是单倍体。设计了两组对比试验,其正确识别率的平均值分别达到95%和93.57%。在该实验中, 基于KPCA的玉米单倍体识别算法的性能表现较好、识别率较高。通过两组对比实验,证明了玉米种子的近红外光谱数据更适于先将其映射于高维空间中进行特征提取,再对提取的特征进行建模、分类分析。该实验为玉米单倍体识别技术提供了新的思路和方法。     

Fabrication and electrochemical investigation of Li<Subscript>0.5</Subscript>TiO<Subscript>2</Subscript> as anode materials for lithium ion batteries

Hexagonal and cubic Li_0.5TiO₂ particles have been fabricated through magnesiothermic reduction of Li₂TiO₃ particles in a temperature range of 600 to 640 °C. The prolonged reduction time results in lattice transition from hexagonal to cubic structure of Li_0.5TiO₂. Their microstructures, valance state, chemical composition, as well as electrochemical performance as anode candidates for lithium ion batteries have been characterized and evaluated. The hexagonal Li_0.5TiO₂ exhibits better electrochemical activity compared with the cubic one. Further, the carbon-coated hexagonal Li_0.5TiO₂ displays improved electrochemical performance with initial reversible capacity of 176.6 mAh g^?1 and excellent cyclic behavior except capacity fading in the initial 10 cycles, which demonstrate a novel anode candidate for long lifetime lithium ion batteries.     

Facile preparation of ultrafine manganese dioxide nanowires on activated carbon paper with enhanced capacitance for supercapacitors

Ionics - In this paper, a structure with growing MnO2 nanowires (NWs) on activated carbon paper was designed and prepared using a simple hydrothermal method. Electrochemical measurements show that...     

Zn2+∶Yb3+∶LiNbO3晶体生长及光谱性能研究

采用提拉法成功生长了Zn2+(2mol;)单掺的同成分铌酸锂(Zn2+∶LiNbO3)晶体及Zn2+(6mol;)和Yb3+(1 mol;)双掺的同成分铌酸锂(Zn2∶Yb3+∶LiNbO3)晶体,晶体尺寸分别约为φ30 mm×40 mm和φ30 mm×50mm.测试了这两个晶体的XRD图谱并与标准图谱进行了比较.测量了Zn2∶LiNbO3和Zn2∶Yb3+∶LiNbO3晶体的红外透射光谱,OH-的振动吸收峰分别位于3484.2 cm-和3493.7 cm-1,表明Zn2+的掺杂浓度还都处在阈值以下.研究了Zn2+∶Yb3+∶LiNbO3晶体的室温吸收、发射光谱和荧光寿命特性,表明其是潜在的近红外激光增益介质,有望发展新型功能激光器件.     

典型单质炸药晶体结晶品质的显微拉曼光谱法评价分析

为了评价分析单质炸药晶体结晶品质,采用无损、快速的显微拉曼光谱分析技术,研究了单晶、纯度标准物质、工业品3种不同结晶品质奥克托金(HMX)5个拉曼特征峰统计规律.结果表明:随着晶体缺陷增多,拉曼特征峰半峰宽值(FWHM)随之增大,其相对标准偏差(RSD)亦增大.在此基础上,对未知结晶品质的3种黑索今(RDX)试样RDX-1、RDX-2、RDX-3进行相同条件的显微拉曼试验,并根据拉曼特征峰半峰宽值确定其结晶品质由高到低依次为RDX-1、RDX-2、RDX-3,和扫描电镜法品质评价分析结论一致.     

乙苯裂解机理和超临界压力下的动力学模拟

基于乙苯燃烧机理的去氧处理获得的乙苯裂解机理, 采用QRRK/MSC算法代码对小分子产物的高压裂解相关参数进行改进, 构建了高压条件下乙苯裂解的136个物种及626步反应的机理. 在超临界压力和高温条件下的动力学模拟表明, 乙苯裂解机理的气相分子产率和转化率的模拟结果与实验结果相吻合. 采用敏感度分析对机理的控速步骤进行验证, 考察了机理中的关键反应, 结果表明本机理能较好地预测高压实验结果, 可应用于超临界裂解换热的计算模拟.     

Weak order in averaging principle for stochastic wave equation with a fast oscillation

This article deals with the weak error in averaging principle for a stochastic wave equation on a bounded interval $[0,L]$, perturbed by an oscillating term arising as the solution of a stochastic reaction–diffusion equation evolving on the fast time scale. Under suitable conditions, it is proved that the rate of weak convergence of the original solution to the solution of the corresponding averaged equation is of order $1$ via an asymptotic expansion approach.     

一种多介质流体计算的三维非守恒型差分格式

Motivated by the need for three-dimensional methods for interface calculations we describe a 3D non-conservative difference scheme in Lagrange coordinates for calculating multi-component fluid dynamics, according to the thoughts of 2D non-conservative difference scheme and making use of difference method of characteristic and Upwind form. Furthermore, we give a three-dimensional numerical simulation of explosion in concrete, and the results of simulation are consistent with examination.     

聚合酶链式反应微芯片系统用于微量生物样品的快速扩增检测

基于MEMS微加工技术设计和制作了一种集成微加热器和温度传感器的聚合酶链式反应（PCR）微芯片。PCR微芯片结构通过有限元模拟验证分析。该芯片在PCR扩增过程中具有良好的制热效率和热传递均匀性。在微型温度控制电路装置下进行热循环反应,芯片的温度起伏小于1℃／s,升降温速度分别达到5℃／s和3℃／s,30个热循环耗时30min。此系统已经用于GUS基因的扩增检测,获得了良好的结果,极大的缩短了热循环的时间,可用于微量生物样品的快速扩增检测。     

La0.7-x(Sm,Er,Dy)xSr0.3MnO3体系的相分离和渗流相变

通过M-T曲线、M—H曲线、ESR曲线研究了La0.7-x(Sm,Er,Dy)xSr0．3MnO3体系的磁相变．从ESR信号显示,对Er和Dy掺杂在居里温度以上,顺磁相中分离出铁磁团簇,随温度降低呈现渗流相变．稀土锰氧化物的居里温度、宏观磁性和微观磁性不仅取决于A位稀土离子掺杂引起晶格的畸变,而且取决于A位离子掺杂引起的额外磁矩．