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991.
1.9-W flash-lamp-pumped solid-state 266-nm ultraviolet laser 总被引:1,自引:0,他引:1
Deep ultraviolet lasers have various applications in industries and scientific researches. For 266-nm ultra- violet (UV) laser generation, the good beam quality of 1064-nm laser and the elimination of gray-tracking effect of KTP crystal are two key factors. Using a dynamically stable resonator design, 1064-nm laser with an average power of 52 W is realized with repetition rate of 16 kHz. The measured M^2 factor characterizing the beam quality is 1.5. By the elimination of gray-tracking effect of KTP crystal, an 18-W green laser is realized with the M2 factor of 1.6. Using a BBO crystal for the fourth harmonic generation, a 1.9-W 266-nm UV laser is achieved. 相似文献
992.
Yu‐An Xiong Tai‐Ting Sha Qiang Pan Xian‐Jiang Song Shu‐Rong Miao Zheng‐Yin Jing Zi‐Jie Feng Yu‐Meng You Ren‐Gen Xiong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8949-8953
The X‐site ion in organic–inorganic hybrid ABX3 perovskites (OHPs) varies from halide ion to bridging linkers like HCOO?, N3?, NO2?, and CN?. However, no nitrite‐based OHP ferroelectrics have been reported so far. Now, based on non‐ferroelectric [(CH3)4N][Ni(NO2)3], through the combined methodologies of quasi‐spherical shape, hydrogen bonding functionality, and H/F substitution, we have successfully synthesized an OHP ferroelectric, [FMeTP][Ni(NO2)3] (FMeTP=N‐fluoromethyl tropine). As an unprecedented nitrite‐based OHP ferroelectric, the well‐designed [FMeTP][Ni(NO2)3] undergoes the ferroelectric phase transition at 400 K with an Aizu notation of 6/mmmFm, showing multiaxial ferroelectric characteristics. This work is a great step towards not only enriching the molecular ferroelectric families but also accelerating the potential practical applications. 相似文献
993.
An anionic multifunctional porous metal organic framework (MOF), [Cu2THBA(H2O)2] · (C3H7NO)12 · (H2O)10 ( 1 ) (H4THBA = p‐terphenyl‐3,2′′,3′′,5,5′′,5′′′‐ hexcarboxylic acid) with NbO‐type topology was synthesized and characterized. Due to multiple functional sites and suitable pore size, the desolvated compound 1a exhibits high separation selectivity for C2H2/CO2 of 30 and C2H2/CH4 of 131 at 1 kPa at room temperature. Compound 1 can also efficiently and completely separate methylene blue (MB+) molecules of low concentrations from aqueous solution in 12 h. 相似文献
994.
The first copper-catalyzed enantioselective addition of alcohols to imines was described. In the presence of 1?mol% Cu(OAc)2 complexed with chiral cyclohexane-based N,P-ligand L4, chiral isatin-derived N,O-aminals were obtained in excellent yields (93–99%) and good-to-excellent enantioselectivities (up to 93% ee) under mild conditions. 相似文献
995.
Guirong Su Sha Yang Yingda Jiang Jingtai Li Shuang Li Ji-Chang Ren Wei Liu 《Progress in Surface Science》2019,94(4):100561
Chemical reactions on surfaces play central roles in heterogeneous catalysis, and most reactions involve the formation and/or the cleavage of bonds. At present, density functional theory (DFT) has become the workhorse for computational investigation of reaction mechanisms, but its predictive power has been severely limited by the lack of appropriate exchange-correlation functionals. Here, we show that there are many cases where the chemical bonding and van der Waals (vdW) interactions both play a key role in chemical reactions on surfaces. After briefly introducing some DFT methods and basic theory in chemical reactions, we first demonstrate that DFT can help to understand the mechanisms of “classic” reactions that mainly dominated by covalent bonding and vdW forces, as exemplified in electrocatalytic reduction of CO2 and the fabrication of 2D materials on metal substrates. We next show that DFT calculations can help to uncover the tautomerization reactions of molecules on metal surfaces, wherein the hydrogen bonding and vdW forces would largely affect the reaction process. More importantly, we show that in some cases, the vdW interactions can become the decisive effect that determines the adsorption configuration, energy hierarchy, and the potential-energy surface of chemical reactions, yielding distinct pathways and products. Additionally, we highlight the importance of more realistic conditions, such as surface defects, finite coverage, and temperature effects, in accurate modeling of chemical reactions. Finally, we summarize some challenges in modeling catalysis, which include many-body dispersive correction, strong correlation effect, and non-adiabatic approximations. 相似文献
996.
锂离子二次电池用PVDF-HFP/PAMA共混物基聚合物电解质膜的研制 总被引:1,自引:0,他引:1
以丙烯腈(AN)、甲基丙烯酸甲酯(MMA)、丙烯醛(A)为单体,采用乳液聚合法制成一种共聚物———聚(丙烯腈 甲基丙烯酸甲酯 丙烯醛) (PAMA) .将PAMA作为第二共聚物与聚(偏氟乙烯 六氟丙烯) (PVDF -HFP)共混,并向反应体系中添加纳米级SiO2 ,充分混合后利用二次相转移法制得薄膜,并对所得薄膜的断面形貌、吸附性能、热性能、导电性能等进行了测试.研究发现,SiO2 的加入增大了膜中微孔体积,改善了微孔分布,且增大了电解液的吸附量;共聚物PAMA的组成影响薄膜的吸附性能,其中极性较大的丙烯醛单元和丙烯腈单元起着决定性作用;PAMA含量的增加使得共混膜吸附电解液量增加.制得共混膜的离子电导率达2 . 30×10 - 3S cm . 相似文献
997.
998.
离散光电成像系统因其不再具有平移不变特性,它的调制传递函数测试具有相当的复杂性和不稳定性。为提高光学系统调制传递函数测试的灵活性和可重复性,在基于统计光学和随机信号相关性理论的基础上,分析了离散型空间随机信号经线性光学系统成像后的物像相关性,提出了应用随机条纹靶来测定调制传递函数的方法。并给出了计算数据结果。该方法从统计意义上考虑了离散采样成像器件的采样场景相位的影响,大大提高了现场测试的灵活性和自动化程度,具有很好的应用前景。此方法同样适用于一般光学成像系统的调制传递函数测量。 相似文献
999.
1000.
随着现代信息技术的迅猛发展,声音、图像、视频等多种媒体在课程教学中广为应用,学生在任何时间、任何地点利用信息终端完成线上自主学习成为常态,课程教学的信息全媒体时代随之而来,全媒体对实验教学带来全新要求。本文在总结近年来仪器分析实验全媒体教学经验的基础上,开展全媒体时代背景下仪器分析实验的实践教学设计、资源库建设、新型教学模式构建、课堂教学考评、教学团队建设的研究,以期提高学生自主综合学习能力和高阶思维能力,提升仪器分析实验课程的教学效果,为深入开展全媒体教学改革提供参考。 相似文献