闪光照相条件下相对质量吸收系数的测量

 介绍了闪光照相中X光传播规律的等效单能模型。针对闪光照相出光重复性差、能谱测量困难的特点提出了相对质量吸收系数的概念。阐述了闪光照相中相对质量吸收系数的测量原理和方法。在闪光照相实验设备上采用整条D～L曲线对钨材料相对质量吸收系数进行了测量，得到的实验结果为1.23，与数值模拟结果1.26符合较好。     

快中子照相中的点扩展函数计算

 快中子照相中，基于反冲核原理探测快中子的有机闪烁体平板是普遍采用的快中子辐射转换体。模拟了D-T中子垂直入射BC400闪烁体平板，计算了不同厚度平板闪烁体的点扩展函数，对14.1 MeV快中子照相中闪烁体固有分辨率随厚度的变化进行了研究。计算结果表明，在不考虑二次中子与闪烁体作用及背景噪声等情况时，点扩展函数几乎不依赖于闪烁体厚度。同时，计算还表明在一定的分辨率范围内，由于荧光收集效率的限制，闪烁体厚度增加并不会改善图像对比度。     

闪光Ⅰ号应用于X射线爆轰照相——研究金属射流的穿甲效应

闪光X射线照相技术是研究动载荷及其效应的重要测试手段,特别适用于研究物质在爆炸作用下的瞬变过程,本文介绍了闪光Ⅰ号加速器应用于X射线爆轰照相的基本状况,以及用于观察金属射流穿过高密度物质钨靶的实验技术。     

Unexpected valence bond isomerization of [1,2,4]triazolo[3,4-c][1,2,4]benzotriazines under flash vacuum pyrolytic (fvp) conditions

Flash vacuum pyrolysis (fvp) of some substituted [1,2,4]triazolo[3,4-c][1,2,4]benzotriazine derivatives (1a-d) has been studied between 450 and 600 °C. The only transformation observed up to 525 °C was the unexpected valence bond isomerization of the angularly fused starting compounds to the isomeric linearly fused [1,2,4]triazolo[4,3-b][1,2,4]benzotriazine derivatives (9a-d), whereas at higher temperatures fragmentation products such as aromatic nitriles were also formed. Kinetic measurements revealed negative entropies of activation in the isomerization process, which suggest a concerted ring closure reaction to an intermediate antiaromatic diazirine. Reversibiblity of the title isomerization reaction was also proved by FVP experiments.     

The preparation of 7-substituted norbornadiene-2,3-dicarboxylic anhydrides and an experimental and theoretical study of their reactivity

Four new substituted methano-bridged or heteroatom-bridged norbornadienomaleic anhydrides have been prepared and converted to sesquinorbornadiene anhydrides by reaction with cyclic 1,3-dienes. The versatility of parity reversal, in conjunction with N-substituent steric effects, has been used to produce all three possible stereoisomers of the N,O-sesquinorbornadiene anhydrides in separate, stereoselective cycloadditions. The anhydrides have been synthesized by cyclization of their diacids (in situ production) or by flash vacuum pyrolysis of their furan adducts (yielding crystalline products); further fragmentation occurs at these or higher temperatures to produce five-membered carbocyclic or heterocyclic anhydrides. Activation energies have been evaluated for the fragmentation and cycloaddition processes using DFT calculations (B3LYP/6-31G∗) and these calculations correctly predict, which reaction can be intercepted at the norbornadienomaleic anhydride stage and preferred stereochemistry of cycloadducts.     

Spatially resolved characterization of PEFCs using simultaneously neutron radiography and locally resolved impedance spectroscopy

A method for performing neutron radiography and locally resolved impedance spectroscopy simultaneously in situ in an operating polymer electrolyte fuel cell (PEFC) is presented. The new method provides concurrently spatially resolved information about the local cell performance, the locally limiting processes, and the liquid water distribution. Information about the impact of water on cell performance and limiting processes can be gained in situ on a local scale in an operating PEFC. The method was applied to a PEFC operated on pure H₂/O₂ in co-flow mode under low humidity operating conditions. The results show that in co-flow mode strong flooding and severe drying can occur at the very same time in different sections of a PEFC.     

Utilization of flash chromatography for the fractionation of coal derived liquids

Summary The suitability of flash chromatography for the fractionation of coal liquids in compound classes has been studied. TLC data obtained from standards were used for establishing the sequence, composition and volume of eluents in order to collect the main components of coal liquids in six fractions of increasing polarity. The method was tested by the fractionation of a SCG coal extract and separations were evaluated by TLC, SEC, and IR and NMR spectroscopy.     

Reaction of the carbonate radical with substituted anilines

Rate constants for the reaction of carbonate radical with aniline and some parasubstituted anilines have been determined by the flash photolysis technique. Using σ⁺ para values the rate constants at pH 8.5 correlate very well with the Hammett equation yielding ρ= − 1. The carbonate radical oxidises aniline giving the anilino radical. The products so formed have been identified through studies under conditions of continuous irradiation.     

微视频技术在基础化学实验教学中的实践应用

以高校基础化学实验"从海带中提取碘""三草酸合铁（Ⅲ）酸钾的制备"为例，分别探讨了微视频技术在化学基本操作实验和综合设计型实验中的具体应用；此外，举例说明利用Flash软件制作的虚拟微视频可以在仪器分析实验中清晰地再现仪器真实操作中的每一个步骤，弥补了学生在实验前无法实际操作仪器的不足。实践证明，微视频技术的应用，丰富了基础化学实验教学模式，增强了学生自主学习的能力和动手能力，提高了实验成功率和实验教学效果。