激光拉曼光谱法分析乙烯裂解气

研究建立了乙烯裂解气中6种主要组分H_2,CH_4,C_2H_4,C_2H_6,C_3H_6,C_3H_8的混合气体激光拉曼(Raman)分析法,可将分析时间缩短至约2 min,且无载气、色谱柱等消耗,在加快分析反馈的同时大大降低了仪器维护及使用费用。该方法采用指纹峰浓度曲线,通过筛选计量峰、扣除信号大于3倍信噪比(3 S/N)交叉干扰的修正方式,实现了混合气中6种目标组分的定量分析。在混合气体定量分析中,Raman分析法对H_2,C_2H_4,C_3H_6,C_3H_8的定量分析具有较好的测量精度,均小于2%;但对CH_4及C_2H_6的测量精度有待提高,表明所建立的Raman分析法需进一步优化完善。     

基于太阳漫射板的星上定标方法研究

基于太阳漫射板的星上定标方法是一种具有高精度、高频次、高效率等优点的独立定标方法,是目前提高我国遥感定标精度的重要手段之一。文章阐述了基于太阳漫射板的星上定标原理、方法及实现过程,建立了空间辐射标准,同时给出了星上反射率定标物理模型。分析定标物理模型发现,影响星上定标不确定度最主要的因素是太阳漫射板BRDF实时量值的确定。为此,首先介绍了星上定标时机的选择,根据所确定定标时机的太阳照明角度对太阳漫射板在实验室相应入射角度下的BRDF进行了测量。通过对太阳漫射板从制作完成到星上使用寿命终结整个过程中各阶段的BRDF量值的监测及修正,确保太阳漫射板定标时刻可为遥感器提供精确已知的辐射输入,实现遥感器全寿命期的高精度星上定标。最后,结合国内对定标模型中相关参数项测量的不确定度水平,按照测量不确定度B类评定的方法对基于太阳漫射板星上定标不确定度进行了预估,可实现星上反射率定标不确定度优于2.03%,绝对辐射定标方法不确定度优于2.04%。     

Solvation and aggregation of n,n'-dialkylimidazolium ionic liquids: a multinuclear NMR spectroscopy and molecular dynamics simulation study

The solvation and aggregation of the ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) in water and dimethylsulfoxide (DMSO) were examined by analysis of (1)H and (35/37)Cl chemical shift perturbations and molecular dynamics (MD) simulations. Evidence of aggregation of the IL n-butyl chains in aqueous environments at IL concentrations of 75-80 wt% was observed both in the NMR experiments and in the MD simulations. The studies also show that [C4mim]Cl behaves as a typical electrolyte in water, with both ions completely solvated at low concentrations. On the other hand, the data reveal that the interactions between the [C4mim](+) and Cl(-) ions strengthen as the DMSO content of the solutions increases, and IL-rich clusters persist in this solvent even at concentrations below 10 wt%. These results provide an experimentally supported atomistic explanation of the effects that these two solvents have on some of the macroscopic properties of [C4mim]Cl. The implications that these findings could have on the design of IL-based solvent systems are briefly discussed.     

Acetonitrile derivatives as carbonyl synthons. One-pot preparation of diheteroaryl ketones via a strategy of sequential SNAr substitution and oxidation

The anion of 2-aryl acetonitrile derivatives reacted with a variety of heteroaryl chlorides or bromides in an S(N)Ar manifold to afford intermediate anions which were susceptible to oxidation. The addition of sodium peroxide and aqueous NH(4)OAc solution effected oxidation to afford aryl heteroaryl ketones in good yields. Aryl acetonitrile derivatives are thus umpolung-type synthons of the corresponding aryl carbonyl functionality.     

质子辐照硼硅酸盐玻璃盖片的物理效应分析

作为航天器电源系统的重要组成部分,太阳电池需要更高的转换效率和可靠性以及更长的使用寿命。通过在太阳电池表面覆盖抗辐照玻璃盖片,可以增强太阳电池对粒子辐射的防护,延长太阳电池的服役寿命,使航天器获得可靠的能源供应。硼硅酸盐玻璃就是一种理想的太阳电池玻璃盖片材料。采用蒙特卡罗方法,结合SRIM软件模拟研究质子辐照硼硅酸盐玻璃的损伤物理机理。基于粒子与物质相互作用的理论以及基本公式,通过分析不同入射能量的质子在硼硅酸盐玻璃中的阻止本领、电离能损、位移能损、空位的产生情况,对辐照损伤的物理机制进行研究。结果表明：能量为30～120 keV的质子辐照损伤主要发生在硼硅酸盐玻璃表面;质子沉积、空位分布等均为Bragg峰型分布;电离能损是能量损失的主要部分,随入射能量的增加而增大,导致电子的电离和激发;位移能损在玻璃内部随能量降低而增大,导致硼、氧和硅等空位缺陷的产生;电离效应和缺陷的产生是硼硅酸盐玻璃色心形成的重要原因。     

Tin (IV) chloride-promoted one-pot synthesis of novel tacrine analogues

A facile synthesis of potential acetylcholinesterase (AChE) inhibitors, the tacrine analogues 3a-p, has been accomplished by direct cyclocondensation of 1-aryl-4-cyano-5-aminopyrazole with β-ketoesters using tin(IV) chloride as catalyst. The structures of all the compounds have been confirmed by IR, 1H- and 13C-NMR.     

Monte Carlo study of electron correlation functions for small molecules

A study is made of electron-electron correlation functions for use in trial wave functions for small molecules. New forms are proposed that have only a few variational parameters, and these parameters have physical meanings that are easily discerned. Total energies for H₂, LiH and Li₂ computed using these correlation functions are presented, and comparison is made with previous forms, including the Jastrow-Pade form often used in Monte Carlo studies. We further treat the possibility that correlation depends not only on the separation of a pair of electrons but also on the location of the electron pair relative to the nuclei — indicative of a density-dependent or many body correlation effect. Our results indicate that such a many-body correlation effect is weakly present.This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098     

Photoluminescence Property of Co3O4 Nanowires

Co3O4 nanowire arrays are fabricated by electrodeposition with following heat-treatment in atmosphere ambient. Photoluminescence is investigated at 295K. In the experiment, when increasing the excitation light wavelength from 260 nm to 360 nm, two kinds of emissions corresponding to the increasing excitation light wavelength are observed. One of them alters the excited emission position, another keeps its emission position. The distinct behaviour of excited emissions related to the increasing excitation wavelength indicates that the mechanism of them must be different. According to the experimental comparison and first-principle calculation, the two kinds of emissions are discussed.     

Yb3+/Tm3+共掺杂的钨酸镉纳米晶发光性能的研究

本文采用水热法制备了稀土离子Yb³⁺/Tm³⁺共掺杂的钨酸镉纳米晶。运用X-射线粉末衍射、场发射环境扫描电子显微镜和光谱分析对制备的样品的结构和发光性能进行了表征。根据XRD图谱可知, 钨酸镉为单斜晶系, 晶粒平均尺寸在28 nm左右。从ESEM图片可明显看出, 钨酸镉呈纳米棒结构, 直径在30 nm左右, 长径比在5~8之间。利用980 nm半导体激光器激发钨酸镉纳米晶得到样品的发射光谱, 存在一个较强的蓝光发射, 发光峰位于481 nm,对应于Tm³⁺的¹G₄→³H₆能级的跃迁, 分析了Tm³⁺/Yb³⁺离子共掺体系的发光机制。讨论了发光强度随稀土离子浓度的变化, 当Tm³⁺离子的掺杂浓度在2%, Yb³⁺/Tm³⁺物质的量浓度比为10:1时钨酸镉纳米晶的发光强度最强。根据泵浦功率与发光强度之间的关系, 可知处于481 nm的蓝光发射属于三光子过程, 由发光强度与掺杂浓度之间的双对数衰减曲线可知, 引起蓝光发射源于Tm³⁺的电偶极跃迁。     

高压隔离电参数测量的新方法

介绍了用铌酸锂(LiNbO₃)高速光强度调制器测量HL-2A装置ECRH系统高压隔离电参数的新方法,测量结果表明：隔离100kV高压的响应时间小于0.1μs,线性误差小于1%,并对器件存在的问题和实际应用的可行性进行了分析。