液体透镜的诞生和发展

本文介绍当今世界最先进的透镜成像系统——液体变焦透镜的诞生和发展.首先是哥伦比亚大学的反射式旋转液体透镜,可用作天文望远镜;透射式液体透镜从加州大学圣地亚哥分校的压力透镜,到Lucent公司的纯电力控制的液体—空气界面的透镜,再到Philips公司的方便操作的封闭式液—液界面透镜,最后到法国VariOptic公司的能自动调节光轴的改进型透镜,其中着重介绍了VariOptic的液体透镜.     

钽酸锂晶体的喇曼光谱及其方向色散的测定

为了测定钽酸锂铁电晶体异常声子的方向色散,我们找到一种较为满意的直角散射几何配置,制备了十个不同取向的样品,并为消除内反射光引起的附加散射,在样品表面上镀了增透膜,获得了波夫与光轴成不同夹角时的一系列寻常声子和异常声子的喇曼光谱.对这些喇曼光谱进行了识别,认定了四个A_1光学声子和九个E光学声子,确定了十三个异常声子方向色散支.由于全部异常声子的散射峰能始终一起出现在同一喇曼光谱中,使得异常声子方向色散的确定一目了然.最后用单轴晶体异常声子方向色散公式计算了异常声子的方向色散曲线,实验与理论计算相当符合.     

Pyrolysis Process of Plant Fibers北大核心CSCD

The natural plant fiber has a large molecular weight and complex structure and composition,and its thermal cracking products and the composition distribution are also more complex. The fast pyrolysiscomprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry（Py-GC×GC-TOF/MS）,thermogravimetry-Fourier transform infrared spectroscopy（TG-FT-IR）,and in situ Fourier transform infrared spectroscopy（in situ FT-IR）methods were used to study the thermal pyrolysis process of six different natural fibers. The distribution of thermal pyrolysis products of different fibers under different pyrolysis temperatures was investigated and the product form was fully discussed. The research results show that the products of fiber pyrolysis mainly include alcohols,aldehydes,ketones,acids,esters,hydrocarbons, dehydrated sugars and CO2,etc. The types of pyrolysis products of different natural plant fibers are obviously different,and the main product types obtained are all different. At the same time,the results of in situ infrared spectroscopy and mass spectrometry show that pyrolysis products are closely related to the pyrolysis temperature. The results of in situ infrared experiments show that when the pyrolysis temperature is lower than 100 °C,the adsorbed water on the surface of the fiber structure is desorbed,but the fiber structure does not change significantly. When the pyrolysis temperature range is 100~200 °C,the temperature has little effect toward the pyrolysis process. When the temperature exceeds 300 °C,the fiber pyrolysis reaction intensifies and the surface structure changes significantly,and the main products are aldehydes and ketones. © 2022, Science Press (China). All rights reserved.     

High-order harmonic generation of the cyclo[18]carbon molecule irradiated by circularly polarized laser pulse

High-order harmonic generation of the cyclo[18]carbon (C₁₈) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of the ring molecule C₆ H₆ having similar ionization potential, the C₁₈ molecule has higher efficiency and cutoff energy than C₆ H₆ with the same laser field parameters. Further researches indicate that the harmonic efficiency and cutoff energy of the C₁₈ molecule increase gradually with the increase of the laser intensity of the driving laser or decrease of the wavelength, both are larger than those of the C₆ H₆ molecule. Through the analysis of the time-dependent evolution of the electronic wave packets, it is also found that the higher efficiency of harmonic generation can be attributed to the larger spatial scale of the C₁₈ molecule, which leads to a greater chance for the ionized electrons from one atom to recombine with others of the parent molecule. Selecting the suitable driving laser pulse, it is demonstrated that high-order harmonic generation in the C₁₈ molecule has a wide range of applications in producing circularly polarized isolated attosecond pulse.     

光催化CO2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO₂引起的地球变暖和能源短缺已经成为一个严重的全球性问题. 利用太阳光和光催化材料将CO₂还原为碳氢燃料, 不仅可以减少空气中CO₂浓度, 降低温室效应的影响, 还可以提供碳氢燃料, 缓解能源短缺问题, 因此日益受到各国科学家的高度关注. 本文综述了光催化还原CO₂为碳氢燃料的研究进展, 介绍了光催化还原CO₂的反应机理, 并对现阶段报道的光催化还原CO₂材料体系进行了整理和分类, 包括TiO₂光催化材料, ABO₃型钙钛矿光催化材料, 尖晶石型光催化材料, 掺杂型光催化材料, 复合光催化材料, V、W、Ge、Ga基光催化材料及石墨烯基光催化材料. 评述了各种材料体系的特点及光催化性能的一些影响因素. 最后对光催化还原CO₂的研究前景进行了展望.     

用傅立叶变换拉曼光谱法测定乙醇浓度

激光拉曼光谱可以迅速准确的分析混合溶液的成分及比例,为溶液浓度检测提供了一种新的方法.以乙醇溶液为例,研究用拉曼光谱法分析溶液的浓度.     

碳纳米管晶格振动模及拉曼光谱的研究进展

本文介绍了碳纳米管的结构特征和晶格振动模的理论研究 ,综述了不同方法生长的多壁碳纳米管和单壁碳纳米管拉曼光谱的研究进展。另外 ,还简单描述了单壁碳纳米管的应用前景     

催化动力学光度法测定生物样品中的草酸

提出了一种经动力学光度法测定生物样品中草酸的方法。基于在硫酸介质中,草酸能有效地催化重铬酸钾氧化丁基罗丹明Ｂ褪色,当反应温度为６５℃、反应时间１２ｍｉｎ时,非催化反应溶液的吸光度Ａ０和催化反应溶液吸光度Ａ的ｌｎＡ０／Ａ值与草酸浓度在０．２０～１０．０８μｇ／ｍｌ之间存在良好线性关系。反应体系用高浓度ＮａＯＨ终止后室温下可稳定２ｈ以上。催化反应的表观活化能为１３．５３ｋｊ／ｍｏｌ。方法可直接用于菠菜     

高二学生掌握化学平衡命题的潜在类别分析和Apriori算法研究*

高中生对化学平衡的理解是重要且仍待深入探索的研究问题。潜在变量模型和数据挖掘有助于研究者从新角度了解学生的化学平衡概念学习情况。本研究使用自编的化学平衡命题测验,应用潜在类别分析和Apriori算法呈现722名高二年级学生对化学平衡命题的掌握情况。研究发现:(1)学生适合被分为3个组别,分别为高掌握水平组、中掌握水平组和低掌握水平组;(2)根据本研究设定的参数条件,未在高掌握水平组学生的作答中获得关联规则,在中掌握水平组和低掌握水平组学生的作答中获得了一些关联规则。潜在类别分析和Apriori算法可被用于化学概念学习和其他主题的研究。