Efficient synthesis of functionalized 2-pyridones by ytterbium chloride catalyzed tandem condensation

An efficient method was developed for the synthesis of arylidene heterobicyclic 3-cyano-2-pyridones via ytterbium chloride catalyzed tandem condensation of aromatic aldehydes,cyclic ketones,and cyanoacetamide.The conditions and scope of the reaction were investigated and a reaction mechanism was proposed.     

新农村建设背景下祠堂文化功能的演变

论述了古祠堂的文化及功能,并进一步研究了在社会主义新农村建设大背景的下祠堂文化功能,探讨了祠堂的社会教化意义,指出祠堂文化演进及其功能与"经济、政治、文化、社会"相通,有提高人之精神、兴发人之志气、开辟人之智慧之源的影响力。     

广义相对论效应下的Kerr场重力加速度

根据GR稳定场的Kerr度规,由引力场质点重力加速度的逆变分量推导Kerr场质点的重力加速度逆变分量的球坐标精确表示式.结果表明,Kerr场中质点的重力加速度不仅与场源的质量、单位质量的角动量及质点在场中的位置有关,而且与质点的速度有关,这正是GR效应在Kerr场中质点运动的反映.     

采用多分类器集成方法的带钢表面缺陷图像识别

现有带钢表面缺陷在线识别系统中单个分类器对部分缺陷识别率不高,并且对训练样本依赖性较大;针对这一问题,提出了一种基于并行多分类器集成技术的带钢缺陷图像识别方法.该方法选择LVQ神经网络、RBF神经网络和支持向量机作为基分类器,应用加权投票法对基分类器进行集成,从而实现基分类器能力互补.实验表明,采用多分类器集成的带钢表面缺陷图像识别方法可以更准确地对带钢常出现的边缘锯齿、焊缝、夹杂、抬头纹等缺陷进行识别,能够得到相当或优于任何单个分类器的分类精度,总体识别率达到96%以上.     

用分数维方法将心电图形加载患者参数数字化

本文首次提出了在心电图图形数字化过程中加载患者临床诊断信息的思想．我们借鉴分数维的处理方法,采用跟踪了三年的患者病历,以尽早发现心脏病变为目的,将患者临床诊断信息与心电图图形相结合,定义了一种把心电图转换成数据的新方法．该方法可克服由于心脏混沌造成的患者心电图的个体差异,便于使用计算机建立患者数据库及进行相应的数据分析．     

关于思想政治教育目的的确立依据及当代启示

思想政治教育的目的是思想政治教育中的一个根本性问题,它不仅为思想政治教育活动的开展提供基本依据和目标指向,而且为衡量和检验思想政治教育效果提供基本尺度。结合时代变迁对思想政治教育目的进行科学、合理的定位,对于保证思想政治教育的方向,促进人的自由全面发展具有重要意义。     

Missing Data Imputation for Traffic Flow Based on Improved Local Least Squares

Complete and reliable field traffic data is vital for the planning, design, and operation of urban traffic management systems. However, traffic data is often very incomplete in many traffic information systems, which hinders effective use of the data. Methods are needed for imputing missing traffic data to minimize the effect of incomplete data on the utilization. This paper presents an improved Local Least Squares (LLS) approach to impute the incomplete data. The LLS is an improved version of the K Nearest Neighbor (KNN) method. First, the missing traffic data is replaced by a row average of the known values. Then, the vector angle and Euclidean distance are used to select the nearest neighbors. Finally, a regression step is used to get weights of the nearest neighbors and the imputation results. Traffic flow volume collected in Beijing was analyzed to compare this approach with the Bayesian Principle Component Analysis (BPCA) imputation approach. Tests show that this approach provides slightly better performance than BPCA imputation to impute missing traffic data.     

Plasmonic Bloch oscillations and resonant Zener tunneling in subwavelength metal-dielectric-air waveguide superlattices

In this paper,we study the propagation properties of surface plasmon polaritons in plasmonic single-cavity superlattices and two-cavity superlattices which are composed of two kinds of alternately stacked subwavelength metal-dielectric-air waveguides with large dispersion.Theoretical predictions of plasmonic time-resolved Bloch oscillations existing in single-cavity superlat-tices and resonant Zener tunneling(ZT) occurring in two-cavity superlattices by the transfer matrix method(TMM) are well dem-onstrated by the numerical simulations on the propagation of SPPs pulse in the two kinds of superlattices by the finite-difference time-domain(FDTD) method.The two proposed superlattices can be conveniently fabricated by present nanotechnology,and the study may promote the realization of plasmonic BO and resonant ZT in nanoscale devices experimentally.     

纳米铁粉燃烧特性研究

通过对粒径为50,100,500和20×10~3nm铁粉的比表面积实验(BET法)、燃烧热值实验和热分析实验,得到不同粒径铁粉的表面微观结构、燃烧热值和失重曲线,分析粒径对比表面积、燃烧热值的影响,研究不同粒径铁粉在10,20,30和40 K/min升温速率下的燃烧特性参数和动力学参数.结果表明:粒径减小,铁粉比表面积和燃烧热值均增大,当粒径为50 nm时,燃烧热值最高,其值为6 792.1 J/g.粒径增大,着火点温度、最高燃烧速率对应温度、燃尽温度升高,燃尽时间延长;升温速率增大,相同粒径铁粉的着火温度、最大燃烧速率对应的温度和燃尽温度升高,纳米铁粉的最大燃烧速率增大,而微米铁粉的最大燃烧速率减小.随着粒径和升温速率的增大,活化能和指前因子都增大且存在互补偿效应.     

C6H5X·Y-（X，Y=F，Cl，Br，I）中氢键和卤键的理论研究

通过MP2／aug—cc—pVDZ理论方法计算研究了C6H5X·Y-（x,Y=F,Cl,Br,I）体系中的氢键和卤键．计算表明所有的卤代苯都能与卤素离子形成氢键相互作用,氢键强度顺序为：C6H,F〈C6H5C1〈C6H5Br〈C6H5I;F-〉Cl-〉Br-〉I-．C6H5Cl,C6H5Br,C6H5I能与卤素离子形成卤键相互作用,卤键强度顺序为：C6H5Cl〈C6H5Br〈C6H5I;F-〉Cl-〉Br-〉I-．分析结果可以发现体系中的卤键强度差异要大于氢键,说明在此体系中卤键具有比氢键更大的选择性．