提高PLC系统的可靠性浅析

可编程控制器（PLC）作为新一代工业控制器因其具有体积小、功能强、煽程方法简单易学，容易实现过程控制而得到广泛应用。但是环境过于恶劣，电磁干扰特别强烈，或安装使用不当，保护程序设计不当，都不能保证PLC系统安全可靠的运行，因此在控制系统中采取一些有效措施是非常必要的。本文从可鳊程控制器的输入端来分析提高PLC控制系统可靠性，保证其稳定工作的一些需要注意的问题和对策。     

基于氧杂蒽结构可控官能化的荧光探针研究新进展

荧光分子探针技术在表达分子间识别行为及复杂生命和环境体系的内状态信息方面具有非常优异的性能,氧杂蒽及其衍生物螺连隐色体结构变化伴随的分子荧光变换模型,广泛且深入的应用于构建新型功能光敏探针分子.近年来此类探针的合成设计及功能化调控研究异常活跃,新的突破不断涌现.综述了新近基于氧杂蒽及其衍生物的荧光探针在金属阳离子、pH、阴离子识别检测方面的研究进展,并简要阐释了该类探针分子的构筑,识别检测机理以及探针在生物成像和环境监测等方面的应用.     

Transverse profile expansion and homogenization at target for the injector Scheme-Ⅰ test stand of China-ADS

For the injector Scheme-Ⅰ test stand of the China-ADS (Accelerator Driven subcritical System), a beam with the maximum power of 100 kW will be produced and transported to the beam dump. To solve the very high thermal load problem at the dump, two measures are taken to deal with the huge power density at the target. One is to enlarge the contact area between the beam and the target, and this is to be accomplished by expanding the beam profile at the target and using slanted target plates. The other is to produce a more homogenous beam profile at the target to minimize the maximum power density. Here the beam dump line is designed to meet the requirement of beam expansion and homogenization at 3 different energies (3.2 MeV, 5 MeV and 10 MeV), and the step-like field magnets are employed for the beam spot homogenization. Taking into account the fact that the space charge effects are very strong at such low beam energies, the simulations have included space charge effects and errors which show that the beam line can meet the requirements very well. In the meantime, the alternative beam design using standard multipole magnets is also presented.     

浅谈幼儿数学活动中集体与分组相结合的教学模式

在集体与分组相结合的数学教育活动课程模式中,教师注重的是引导、点拨和质疑,幼儿则着重在操作、发现和探索.教师在与幼儿的互动过程中,应找准指导的角度,做到"指导要精、点拨要准、材料要足、方法要巧",使幼儿在多层次、多形式的集体与分组相结合的教学活动中既轻松愉快又积极主动,从而发挥最佳的教育功效.     

虚拟机在计算机课程教学中的应用

虚拟机技术是利用真实物理计算机资源,模拟出可以运行不同操作系统与应用软件的多个计算机的技术。利用虚拟的多个计算机,可以在一台计算机上组建虚拟网络,可为"网络技术"、"信息安全"等基于网络的课程提供实验操作平台。同时,虚拟机在"硬件组装与维护"教学的实践操作中也有十分明显的作用。     

Soliton excitations and chaotic patterns for the (2+1)-dimensional Boiti-Leon-Pempinelli system

By improved projective equation approach and a linear variable separation approach, a new family of exact solutions of the (2+1)-dimensional Boiti-Leon-Pempinelli (BLP) system is derived. Based on the derived solitary wave solution, some dromion and solitoff excitations and chaotic behaviours are investigated.     

Transverse profile expansion and homogenization at target for the injector Scheme-I test stand of China-ADS

For the injector Scheme- test stand of the China-ADS(Accelerator Driven subcritical System), a beam with the maximum power of 100 k W will be produced and transported to the beam dump. To solve the very high thermal load problem at the dump, two measures are taken to deal with the huge power density at the target.One is to enlarge the contact area between the beam and the target, and this is to be accomplished by expanding the beam profile at the target and using slanted target plates. The other is to produce a more homogenous beam profile at the target to minimize the maximum power density. Here the beam dump line is designed to meet the requirement of beam expansion and homogenization at 3 different energies(3.2 Me V, 5 Me V and 10 Me V), and the step-like field magnets are employed for the beam spot homogenization. Taking into account the fact that the space charge effects are very strong at such low beam energies, the simulations have included space charge effects and errors which show that the beam line can meet the requirements very well. In the meantime, the alternative beam design using standard multipole magnets is also presented.     

一种基于专家理性预期的组合预测方法及应用

将多个单预测模型进行组合,是提高预测精度的有效途径.由专家理性预期对待选用的单预测模型从模型拟合、方法应用复杂性、适应性和时效性方面进行多指标综合评价,在此基础上,构建组合权重系数,给出了具有主客观信息集成特征的组合预测方法,将组合预测模型与单预测模型进行分析对比,对我国民用汽车的保有量进行了预测并给出了预测效果分析.模型预测效果分析显示,具有主客观信息集成特征的组合预测模型比单预测模型具有更强的适应性,预测精度大幅提高.     

Crystal Structures,Thermal Behaviors and Biological Activities of Acylhydrazone Compounds Containing Pyrazine Rings and Halogen Atoms

Three new kinds of acylhydrazone compounds(C_(12)H_(10)FN_5O·H_2O,1;C_(12)H_(10)Cl N_5O·2CH_3COOH,2;C_(12)H_(10)Br N_5O,3)were synthesized by the reaction of 2-amino-3-pyrazinecarbohydrazide(C_5H_7N_5O)with halogenated benzaldehyde(C_7H_5OX,X=F,Cl,Br).The structures of the three compounds were characterized by elemental analysis,~1H NMR,IR and X-ray diffraction.X-ray single-crystal diffraction presents that the three compounds all belong to triclinic system,P1 space group.Thermal gravity analyses show that three compounds have excellent thermal stabilities and all the thermal decomposition temperature of maximum weight loss was around 300°C.The interactions of the compounds with CT-DNA were investigated by UV-Vis spectrum,fluorescence spectrum and viscosity measurement.All the results suggest that three compounds could bind with CT-DNA through intercalation.The fluorescence spectrum was also used to study the interactions of three compounds with BSA.It was proved that all the compounds could quench the intrinsic fluorescence of BSA via a static quenching process.Compound 2 displays the strongest binding ability both in the reaction with CT-DNA or BSA.Antimicrobial test was carried on Escherichia coli,Staphylococcus aureus and Salmonella,and 2 is more effective against S.aureus.But in MTT assay,1 shows better cytotoxity activity against A549cells.     

Crystal Structures,ct-DNA/BSA Binding Properties and Antibacterial Activities of Halogenated Pyridyl Hydrazones

Three new halogenated pyridyl hydrazones, namely 4-chlorobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone(C(13)H9Cl2N3O, 3 a), 4-bromobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone(C(13)H9BrClN3O, 3 b) and 4-iodobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone(C(13)H9ClIN3O, 3 c), have been synthesized and characterized by elemental analysis, IR, 1 H NMR, and single-crystal X-ray diffraction. The X-ray diffraction analysis revealed that 3 a^3 c crystallize in monoclinic with space group Cc. The units of 3 a ~ 3 c were linked by intermolecular N–H...X(X = Cl, Br, I) hydrogen bonds into 2 D layered structures, which were further extended into 3 D networks by a series of π-π stacking interactions. Thermogravimetric analysis showed that all of them possessed higher thermal stabilities. The reactivities toward calf thymus DNA(ct-DNA) and bovine serum albumin(BSA) of 3 a^3 c were investigated by UV-vis and fluorescent spectroscopy as well as molecular docking simulation. Both theoretical and experimental results indicated that 3 a^3 c bound to ct-DNA in the mode of minor groove binding, and interacted with BSA through the hydrophobic cavity near TRP213. Besides, the orders of binding affinities of 3 a^3 c to ct-DNA and BSA were both 3 c > 3 b > 3 a, which were the same as that of antibacterial activities. Thus, the interactions of iodinated acylhydrazone with biological targets were stronger than that of chlorinated and brominated acylhydrazones, which provided a representative case for halogenation of lead compounds in rational drug design.