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Editor's Letter

The World of Chinese 2024年第1期 1-1页

作者： sam Davies 不详

China is an education powerhouse. The country’s universities produced nearly 12 million graduates last year, while 18 million teachers in public schools prepared students for exams. But changes are afoot in this giant education sector. This issue’s cover story delves into new trends and strains impacting teachers, students, and universities.

关键词： while education Letter

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Frozen Joy

China Weekly 2024年第2期 63-63页

作者： sam Duckett 不详

As Christmas approached,Beijing was unexpectedly blessed with heavy *** be told,I went back and forth on whether to use the word“blessed”or“cursed,”but we can talk more about my Grinch-like nature later in the *** up in the drizzling streets of southeast England,a white Christmas was something I had only ever seen in *** to think of it,during my more than 10 years in Beijing,it's been somewhat of a rareoccurrence heretoo.

关键词： southeast Christmas something

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Dancing with a Star

China Weekly 2024年第7期 62-62页

作者： sam Duckett 不详

It was just an ordinary day in Beijing when I got a message from my daughter's kindergarten about an upcoming school dance *** first,I thought,"How delightful,I can't wait to see her perform!"To my dismay,I discovered... 详细信息

关键词： daughter dis ordinary

Particle-size-dependent upconversion luminescence of NaYF4:Yb,Er nanoparticles in organic solvents and water at different excitation power densities

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Nano Research 2018年第12期11卷 6360-6374页

作者： Marco Kraft Christian Würth Verena Muhr Thomas Hirsch Ute Resch-Genger Federal Institute for Matefiab Research and Testing (BAM) Division1.2BiophotonicsRichard-Willstaetter-Str.1112489BerlinGermany Institute of Analytical Chemistry Chemo-and BiosensorsUniversity of Regensburg93040RegensburgGermany

A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12–43 nm is presented utilizing steady-state and time-resolved fluorometry. Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by high-energy O–H and C–H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated population pathways of the 4F9/2 energy level of Er3+ were examined. Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels.

关键词： upconversion nanoparticle quenching diameter water cyclohexane

LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals

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Nano Research 2021年第3期14卷 797-806页

作者： Frederike Carl Leonie Birk Bettina Grauel Monica Pons Christian Würth Ute Resch-Genger Markus Haase Institute of Chemistry of New Materials Department Biology/ChemistryUniversity OsnabrueckBarbarastr.749076OsnabrueckGermany Division 1.2 Biophotonics Federal Institute for Materials Research and Testing(BAM)Richard-Willstaetter-Str.1112489BerlinGermany

We developed a procedure to prepare luminescent LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF_(4):Yb(Yb:YLF)and LiYF_(4):Yb,Er(Yb,Er:YLF)with identical doping *** the luminescence decay times of Yb^(3+)and Er^(3+)are known to be very sensitive to the presence of quenchers,the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell *** improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based ***,the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF_(4) shell ***,anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH−in the crystal lattice,known to quench the emission of Yb^(3+)*** power density(P)-dependent absolute measurements of the upconversion luminescence quantum yield(ΦUC)of LiYF_(4):Yb,Er/LiYF_(4) core/shell particles reveal a maximum value of 1.25%at P of 180 W·cm^(−2).Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes,theseΦUC values are the highest reported so far for LiYF_(4):18%Yb,2%Er/LiYF_(4) nanocrystals without additional *** improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF_(4) nanocrystals.

关键词： nanocrystal decay time luminescence LiYF_(4) quantum yield upconversion

高效钙钛矿基叠层太阳能电池的研究进展（英文）

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Science China Materials 2024年

作者：刘欣星陈龙于月何冬梅晒旭霞 sam Zhang 张正富冯晶易健宏陈江照 Faculty of Materials Science and Engineering Kunming University of Science and Technology School of Chemistry and Chemical Engineering/State Key Laboratory Incubation Base for Green Processing of Chemical Engineering Shihezi University Institute of Physical and Engineering Science/Faculty of Science Kunming University of Science and Technology School of Aeronautics Harbin Institute of Technology Zhengzhou Research Institute Harbin Institute of Technology

过去十年,钙钛矿太阳能电池(PSC)发展迅速,其光电转换效率从最初的3.8%提升至超过26%,接近单结太阳能电池的Shockley-Queisser (S-Q)极限.多结太阳能电池因其在减少热化损失和实现宽光谱吸收方面的巨大潜力,而受到广泛关注,有望突破S-Q...

过去十年,钙钛矿太阳能电池(PSC)发展迅速,其光电转换效率从最初的3.8%提升至超过26%,接近单结太阳能电池的Shockley-Queisser (S-Q)极限.多结太阳能电池因其在减少热化损失和实现宽光谱吸收方面的巨大潜力,而受到广泛关注,有望突破S-Q极限.金属卤化物钙钛矿材料具有宽带隙可调性,使其非常适合作为叠层太阳能电池(TSC)中的子电池材料.目前,中国隆基绿能科技股份有限公司的双结钙钛矿-硅叠层太阳能电池创造了34.6%的世界纪录效率,远超各子电池的单结效率.因此,基于钙钛矿的叠层太阳能电池被广泛认为是下一代太阳能行业的光伏产品.尽管效率取得了显著提高,但钙钛矿叠层太阳能电池的商业化应用仍面临若干挑战,例如钙钛矿材料的稳定性问题和大规模生产的难度.本综述总结了钙钛矿叠层太阳能电池的研究进展及优化策略,并指出了多结太阳能电池面临的关键问题.最后,本文提出了可能的解决方案,以推进钙钛矿叠层太阳能电池的发展.

关键词：

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利用择形分子筛异构化亚甲基二苯胺

Chinese Journal of Catalysis 2024年第7期62卷 124-130页

作者： sam Van Minnebruggen Ka Yan Cheung Trees De Baerdemaeker Niels Van Velthoven Matthias Degelin Galahad O’Rourke Hiroto Toyoda Andree Iemhoff Imke Muller Andrei-Nicolae Parvulescu Torsten Mattke Jens Ferbitz 吴勤明肖丰收 Toshiyuki Yokoi Nils Bottke Dirk De Vos 巴斯夫股份有限公司膜分离、吸附、催化和光谱学可持续解决方案中心(cMACS) 比利时巴斯夫股份有限公司研究组德国东京工业大学纳米空间催化研究所横滨日本浙江大学化学系浙江杭州310028

亚甲基二苯胺(MDA)被广泛用作生产聚氨酯和聚异氰脲酸酯的中间体.然而,当前MDA的生产工艺在控制(4,4’/(2,4’+2,2’))异构体比例方面还存在局限.其中,4,4’-MDA被认为是最有价值的异构体.尽管2,4'-MDA在市场上也有一定的需求,但如果能... 详细信息

亚甲基二苯胺(MDA)被广泛用作生产聚氨酯和聚异氰脲酸酯的中间体.然而,当前MDA的生产工艺在控制(4,4’/(2,4’+2,2’))异构体比例方面还存在局限.其中,4,4’-MDA被认为是最有价值的异构体.尽管2,4'-MDA在市场上也有一定的需求,但如果能将其有效地转化为4,4'-MDA,将能显著提升其附加值.本文在使用苯胺的条件下,利用β分子筛等催化剂,通过双分子机制,可以选择性地将2,4'-MDA异构化为4,4'-MDA.尽管实验显示,多种酸性沸石具有较高的异构化活性,但MCM-68(具有MSE拓扑结构)的催化性能尤为出色,它不仅展现出高异构化活性,而且具有很好的选择性.MCM-68主要催化2,4'-MDA异构化为4,4'-MDA,而2,2'-MDA和低聚物的形成则可以忽略不计.本文还深入探讨了该择形作用的原因,并详细研究了酸位置在MSE分子筛孔道限制中的关键作用.

关键词：铝分布多相催化异构化亚甲基二苯胺聚氨酯择形

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Influence of carbide ceramic reinforcements in improving tribological properties of A333 graded hybrid composites

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Defence Technology（防务技术） 2022年第7期18卷 1107-1123页

作者： Manu sam N.Radhika Department of Mechanical Engineering Amrita School of EngineeringCoimbatore641112Amrita Vishwa VidyapeethamIndia

Aluminium hybrid functionally graded metal matrix composites(FGMMCs),meet growing demands for supreme tribo-mechanical performance in automotive and aviation *** research experimentally compares the influence of carbide ceramics(B_(4)C,SiC,TiC)as reinforcements,in improving reciprocating tribology performance and mechanical strength of A333 hybrid composites against *** cylindrical samples of A333/6 wt%B_(4)C/4 wt%TiC and A333/6 wt%B_(4)C/4 wt%SiC hybrid FGMMCs were developed using horizontal centrifugal *** analysis on both composites revealed increasing ceramic gradient distribution towards outer composite *** rich zone of A333/B_(4)C/SiC hybrid FGMMC showed maximum micro-hardness(198.9 HV)and tensile strength(267.9 MPa).Elemental mapping confirmed effective distribution of ceramics and detected elemental composition of both *** rich layer of A333/B_(4)C/SiC hybrid FGMMC exhibited improved wear resistance in comparison with all three layers of A333/B_(4)C/TiC hybrid FGMMC and ***-body abrasion and tribo-chemical wear were the predominant mechanisms revealed for both composites during worn surface analysis.

关键词： Composites Functional Wear Carbide ceramics

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从云端到乡野在重庆刷新人生居住体验

城市地理 2024年第7期 78-83页

作者：田敏妤左小朵(图) minjie(图) 甜心爱溜达(图) sam_717(图) 无不详摄图网

在重庆这座繁忙的都市里,长江与嘉陵江交汇,澄江如练,烟景融融,山水变幻。奔流不息的江边,充满历史感的民国建筑述说着昔日繁华;闹市街巷的深处,绿意盎然的新艺术风酒店充满禅意;人们依地势构建房屋,不仅有高居峰巅的云上清舍,还有隐于... 详细信息

在重庆这座繁忙的都市里,长江与嘉陵江交汇,澄江如练,烟景融融,山水变幻。奔流不息的江边,充满历史感的民国建筑述说着昔日繁华;闹市街巷的深处,绿意盎然的新艺术风酒店充满禅意;人们依地势构建房屋,不仅有高居峰巅的云上清舍,还有隐于百年老村的心灵居所……“巫山七百里,巴水三回曲”,重庆这座“中国的君士坦丁堡”,因地形作为军事要塞的开拓历程已成历史,而长江航运带来的无尽繁荣,依旧在今日上演着新的传奇。

关键词：长江航运军事要塞民国建筑历史感君士坦丁堡

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