173581 research outputs found
Sort by
Syntheses of Na3V2(PO4)2O2F as a Cathode for Sodium Ion Battery Application
Full text link目前,合成Na3V2(PO4)2O2F(NVPF)材料的方法包括高温固相法、水热法、溶剂热法等,这些方法均不利于该材料的大规模工业化生产。本文开发了温和的低温共沉淀法合成NVPF材料,该材料首次放电容量为105.6 mAh·g-1,首次效率为90.16%。经过简单的热处理过程,可以有效去除由于液相合成带来的结晶水以及吸附在材料表面的羟基,同时还可以提高材料的结晶度,使得材料的首次放电容量提高到124.3 mAh·g-1,首次效率提高到96.06%。以热处理后的NVPF材料为正极,商业化硬碳为负极组装的全电池表现出了优异的循环性能和倍率性能,1C下循环1200次后容量保持率仍有94.6%,4C倍率下的放电容量仍有基准倍率(0.33 C)的86%。该方法有助于NVPF材料的大规模工业化生产。High-temperature solid-state method, hydro-thermal method and solvo-thermal method have been mainly employed to synthesize Na3V2(PO4)2O2F (NVPF) cathode materials. However, these methods are energy consuming and complicated, which is not applicable for a large scale industrial production. In this study, a rather low-temperature (70℃) co-precipitation strategy was proposed to synthesize NVPF cathode materials. The as-prepared NVPF cathode materials showed a spherical shape with a diameter of 400 ~ 500 nm, and exhibited a sodium storage of 105.6 mAh·g-1 and an efficiency of 90.06%. After a simple thermal process, the specific capacity of the material increased to 124.3 mAh·g-1, and the first cycle efficiency increased to 96.06%. More specifically, a series of experiments with different heat temperatures were done and the results revealed that the best electrochemical performance of NVPF cathode material was achieved with the heat treatment of 600℃ for 2 h under argon atmosphere. Techniques including XRD, SEM, FT-IR, TG-MS, and carbon content analysis and Rietveld analysis were used in order to figure out the effect of the thermal process. The results revealed that the heat treatment could remove the crystal water that led to many side reactions and lowered the cycle efficiency, remove the adsorbed hydroxyl resulted from liquid-phase synthesis, as well as increase the crystallinity of NVPF cathode materials and coated a tinny amount of carbon on the surface of the materials through the decomposition of the remained C2O42-, thus, improving the electrochemical performance of the NVPF cathode materials. Additionally, a full cell with a capacity of 24 mAh composed of a NVPF cathode and a commercial hard carbon anode was fabricated and tested. The cell exhibited an excellent cycle and rate performance. It remained 94.6% of its initial capacity after 1200 cycles at 1 C and 86% of the reference rate (0.33 C) capacity even at 4 C. Furthermore, this method is attractive to the large-scale industrial production of NVPF cathode materials.通讯作者:吴凯E-mail:[email protected]:KaiWuE-mail:[email protected]宁德时代新能源科技股份有限公司,福建 宁德 352106Ningde Contemporary Amperex Technology Co., Ltd., Ningde 352106, Fujian, Chin
On the Contacts and Variations of Inland-Min Dialects
No full text李如龙，厦门大学中文系教授、博士生导师。【中文摘要】内陆闽语范围包括今南平市的十个县市和三明市的八个县市，是明显有别于沿海闽语的两个区。内陆闽语与沿海闽语有五条重要语音差异，如来母字读s -、入声韵无塞尾;重要特征词有54条不同，如信（批）泥（涂）稀（猪)渠（他）。这些差异明显是与吴方言和赣客方言的接触造成的。深度的接触造成了浦城北半县闽语蜕变为吴语和原邵武府的闽语蜕变为赣语。中度的接触则有两种形态。一是造成部分系统性的变异，如闽北西片的建阳、武夷山一带,透定读h -，清从读th-。一是在一个县的范围之内形成“小通语”，例如闽语五区之间的尤溪县。除了这些颇具特色的情况之外，还形成了一些小方言岛、混合型方言和过渡型方言。
【Abstract】Inland-Min dialects experienced maximum variation compared with other Min dialects，the main cause of which is their contact with Hakka，Gan and Wu dialects over a long period of time. This paper describes the distribution of inland-Min dialects and lists the main similarities and differences between inland and inshore Min dialects. It explains the qualitative change resulting from the close contact with Wu dialect in northern Pucheng county and Gan dialect in Shaowu city，and describes the system adjustment and the form of common language in certain areas caused by moderate exposure. This paper also discusses some outstanding problems in the study of Min dialects
新文科建设与中国经济学
Full text link洪永淼教授，1980-1985厦门大学物理学本科、硕士研究生；1985-1988厦门大学政治经济学硕士；1988-1993美国加州大学圣地亚哥校区经济学博士；1993-2020美国康奈尔大学经济学与国际研究讲席教授、统计学教授；2002-2005清华大学经济管理学院特聘教授；2020至今中科院数学与系统科学研究院特聘研究员、中科院大学经济与管理学院特聘教授；2005-2020厦门大学王亚南经济研究院创院院长内容摘要：新文科的时代背景；新文科背景下经济学科内涵；新文科背景下经济学与人文社会科学人才培养；总结
Electrochemical Surface-Enhanced Raman Spectroscopic Studies on Nickel Ultramicroelectrode
Full text link镍（Ni）电极在电化学中应用广泛。原位表征Ni电极表面的吸附物种有益于帮助理解电极反应历程、指导发展高效电催化剂。应用超微电极作为工作电极的电化学表面增强拉曼光谱技术结合了超微电极表面的传质特性和分子水平的高灵敏度表征,是研究Ni电化学的有力手段。本文所述的研究工作通过在金（Au）超微电极表面电吸附具有SERS活性的Au纳米粒子并恒电流沉积金属Ni薄层,制备并表征了具有SERS活性的Ni超微电极。在氢氧化钠溶液中的循环伏安实验和以4-甲基苯硫酚分子作为探针分子的SERS实验结果表明,沉积速率和沉积电量是影响超微电极表面Ni的覆盖度和SERS活性的关键因素。在吸附了直径为55 nm Au纳米粒子的、直径为10 μm Au的超微电极表面,以100 μA·cm-2电流密度电沉积厚度约为5个原子层Ni的条件下,可获得Ni覆盖完好的、具有最强SERS活性的Ni超微电极。Nickel (Ni) electrodes are widely used in electrochemical researches. Understanding electrochemical processes on Ni electrodes through in-situ characterization of adsorbed species on their surfaces is helpful for rational optimization and application of Ni electrochemistry. Microelectrochemical surface-enhanced Raman spectroscopy (μEC-SERS) combines the mass transfer feature of ultramicroelectrode with high-sensitivity characterizations of molecular structures, which is a powerful method for studying Ni electrochemistry on polarization and non-equilibrium conditions. The key point of performing μEC-SERS is to make a SERS-active Ni ultramicroelectrode. Here, we demonstrate a method of preparing a SERS-active Ni ultramicroelectrode through electrochemical deposition of several atomic layers of metallic Ni onto a SERS-active gold (Au) ultramicroelectrode. Firstly, a SERS-active Au ultramicroelectrode was made through electrochemical adsorption of Au nanoparticles. A smooth polycrystalline Au ultramicroelectrode with a diameter of 10 μm was made by sealing a Au wire into a glassy tube. The Au nanoparticles of 55 nm in diameter were adsorbed from Au sol onto the Au ultramicroelectrode under an electrochemical polarization at 1.8 V. The scanning electron microscopic (SEM) images showed that Au nanoparticles aggregated on surface. On the prepared Au ultramicroelectrode adsorbed by Au nanoparticles, a thin and compact Ni layer was deposited by using galvanostatic method in 5 mmol·L-1 Ni(NO3)2 electrolyte. The thickness of Ni layer was controlled via the charge. The voltammograms of the prepared SERS-active Ni ultramicroelectrode in 0.1 mol·L-1 NaOH showed the characters of polycrystalline Ni electrode. Since the SERS activity decreased as a result of the increase in the thickness of Ni layer, the SERS measurements of 4-methylthiophenol in air were carried out for evaluating SERS activity. The comparisons in the intensity of the band at 1077 cm-1 from the 4-methylthiophenol adsorbed on the ultramicroelectrode made by using 10 μA·cm-2, 50 μA·cm-2, 100 μA·cm-2, 500 μA·cm-2 and 1000 μA·cm-2 indicated that the rate and charge of deposition are key in determining the coverage status of Ni layer and the SERS activity. An optimized SERS activity on a compact Ni was obtained by electrodepositing 5 atomic layers of Ni at a current density of 100 μA·cm-2. To demonstrate the application of Ni ultramicroelectrode in the in-situ μEC-SERS measurement, the molecule of 4-methylthiophenol, employed as a probe, was adsorbed onto the prepared Ni ultramicroelectrode through spontaneous adsorption in the methanol solution of 4-methylthiophenol. The obtained SERS spectra showed characteristic bands of 4-methylthiophenol. In addition, stark effect of the bands was observed, indicating the successful application of Ni ultramicroelectrode in the in-situ μEC-SERS measurement.The preparation methodology of SERS-active ultramicroelectrode enables the in-situ μEC-SERS measurement on Ni under electrochemical polarization or non-equilibrium reaction conditions, which exhibits a good potential application in studying Ni electrochemistry.国家自然科学基金项目(21872094);国家自然科学基金项目(21991152);国家自然科学基金项目(21802057)通讯作者:黄逸凡E-mail:[email protected]:Yi-FanHuangE-mail:[email protected].上海科技大学物质科学与技术学院,上海 2012102.井冈山大学化学化工学院,江西 吉安 3430091. School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China2. College of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an 343009, Jiangxi, Chin
Deciphering the oxygen activation mechanism at the CuC site of particulate methane monooxygenase
No full text近日，化学化工学院王斌举教授课题组采用多尺度理论计算方法解析了微粒颗粒单加氧酶(pMMO)的催化循环机理。甲烷是仅次于二氧化碳的第二大温室气体，其温室效应是二氧化碳的84倍。然而，由于其结构的复杂性，实验对于微粒甲烷单加氧酶催化机理的研究，尤其是O2的活化机制及其相应的活性中间体的认识尚不清楚。王斌举课题组研究了在生理还原剂度洛喹诺醇 (DQH2) 作用下的pMMO的催化循环机理。相比于所有之前的理论计算，该理论研究不仅证实了CuC位点是O2活化的活性中心，而且揭示酚类辅助底物在氧气活化中的重要作用。该工作的计算模拟主要由王斌举教授课题组2019级博士生彭炜完成。【Abstract】The enzymatic oxidation of methane to methanol has been discovered in methanotrophs over 110 years ago. Nevertheless, the mechanism of action of particulate methane monooxygenase (pMMO) remains elusive, especially regarding O2 activation and the nature of the active species of the enzyme. Herein, we decipher the catalytic cycle of pMMO in the presence of the physiological reductant duroquinol (DQH2). We demonstrate that O2 activation is in fact initiated by a CuC(II)−DQH–species generated by deprotonation of DQH2. Our simulations capture the exclusive pathway for the sequential formation of the intermediates, CuC(II)−O2•–, CuC(II)−OOH–and H2O2, along the O2 reduction pathway. Further, H2O2 activation by CuC(II)−DQH–is initiated by dissociation of DQH•to yield CuC(I), followed by the CuC(I)-catalysed O−O homolysis, en-route to the formation of the CuC(II)−O•–species, which is responsible for C−H oxidations. These findings uncover the important roles of the phenol co substrate for O2 activation, and help resolving the enigmatic mechanism of pMMO.We thank Prof. Brian M. Hoffman for helpful discussions. B.W. is grateful for financial support from NSFC (nos. 21933009 and 22073077). S.S. thanks the Israel Science Foundation (ISF) for support (grant ISF 520/18).
研究工作得到国家自然科学基金（批准号：22073077、21933009）的资助和支持
Sailing to the Ocean of Electrochemistry: the First Step of Experiment
No full text电化学是研究电能和化学能相互转化的规律的科学。电能和化学能之间的相互转换,是通过电极/电解质溶液表界面的结构变化和电荷转移反应来实现的。以电化学能源器件为例,前者为超级电容器,能量存储和释放主要通过界面双电层的表界面结构变化来实现;后者为化学电源,能量存储和释放主要通过电极活性物质的表界面化学反应来实现。所以,研究一个电化学体系时,主要关注两个问题,即表界面结构和表界面电荷转移反应。而表界面结构直接影响表界面电荷转移反应的性质,因此,从电化学实验的角度,表界面的构筑是至关重要的,包括电极的制备和表征、电极修饰材料的制备及组装、溶剂和支持电解质的选择和优化、电化学实验环境等等。本文旨在向广大电化学初学者讲述电化学实验的准备工作以及对实验现场数据的基本判断,帮助大家在实验中及时发现问题,及早采取措施,高效率地获取可信的实验数据。Electrochemistry is the science on the conversion between chemical energy and electric energy, which is realized by the structure change of the electrified surface and interface, and/or the surface and interfacial charge transfer reactions. Taking the electrochemical energy devices as example, the former is the supercapacitor where the energy storage and release are performed by the structure change of the electric double layer; the latter is the battery where the energy storage and release are performed by the redox reaction of the electrode active materials. When investigating an electrochemical system, we have to pay attentions on two issues: the surface and interfacial structures and the charge transfer reactions wherein, and the former has crucial effects on the properties of the latter. Thus, the design and construct of electrode surface and interface are essential in electrochemical experiments, including the preparation and characterization of electrode, the modification and assembly of composite electrode, the choice and optimization of solvent and supporting electrolyte, the experimental environment, etc. The purpose of this paper is to give an introduce on the preparations of electrochemical experiments and to help the juniors to judge the quality of experimental data. This would be helpful for the improvements of data reliability and work efficiency.国家自然科学基金项目(21827802);国家自然科学基金项目(22021001)通讯作者:詹东平E-mail:[email protected]:Dong-PingZhanE-mail:[email protected].固体表面物理化学国家重点实验室,中国福建能源材料科学与技术创新实验室,电化学技术教育部工程研究中心,厦门大学化学化工学院化学系,福建 厦门 3610052.厦门大学航空航天学院机电工程系,福建 厦门 3610051. State Key Laboratory of Physical Chemistry of Solid Surfaces; Fujian Science & Technology Innovation Laboratory for Energy Materials of China; Engineering Research Center of Electrochemical Technologies of Ministry of Education; Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen 361005, Fujian, China2. Department of Mechanical and Electrical Engineering, School of Aerospace Engineering, Xiamen University, Xiamen 361005, Fujian, Chin
On the Modernization of Fiscal and Tax Governance with Chinese Characteristics
No full text邓力平，厦门大学经济学院/厦门国家会计学院教授、博士生导师，经济学博士；陈丽，厦门大学经济学院博士研究生。【中文摘要】进入新时代以来,与国家治理体系和治理能力现代化进程相同步，中国特色社会主义财税在治国理政中的定位和职能得到明确提升。以党的十九届五中全会精神为引领，锚定“十四五”规划和二O三五年远景目标,在理解把握国家治理现代化时代内涵的大背景下研究中国特色财税治理现代化的理论与实践问题。社会主义现代化国家新征程对财税治理现代化提出了特定要求，应站在统筹内外两个大局的高度把握财税治理新方向、展现财税治理新作为，以中国特色财税治理现代化为国家治理现代化提供基础与支柱作用。
【Abstract】In sync with the goal of modernizing Chinas system and capacity for governance,the role of socialist finance and tax with Chinese characteristics in national governance has clearly been improved in the new era. Guided by the spirit of the 5th Plenary Session of the 19th CPC Central Committee, and focusing on the 14th Five-Year Plan and the Long - Term Objectives through the Year 2035,it is necessary to study the theoretical and practical issues of the modernization of fiscal and tax governance with Chinese characteristics, especially in the new journey of building a modern socialist country. It is emphasized that we should grasp the new role of fiscal and tax governance in coordinating internal and external situations,and provide the foundation and pillar for the modernization of national governance
A Study of the Governance of Natural Land Resources in Illegal Farming in the Tang-Song Era
No full text陈明光，厦门大学人文学院历史系教授、博士生导师，历史学博士；靳小龙，厦门大学人文学院历史系助理教授,历史学博士；毛蕾，厦门大学人文学院历史系副教授， 历史学博士。【中文摘要】中国古代自然资源土地资产产权，可分为所有权、占有权、使用权、经营权、监管权等不同层面。唐朝国家对自然资源土地资产产权具有普遍性的管辖权和优先处理权。宋朝进一步将自然资源土地资产划归“系官田产”，或拨予、出卖给私人,或出佃收租。唐宋特别是南宋，国家治理盗耕种自然资源土地资产具有多方面的财政考虑，不仅表现为制定盗耕种自然资源土地资产若能补交租税就不予论处的政策法规，还表现在纠査逃税,直接增加中央财政专项收入，以及与地方财政争夺租税收人，与地方豪强争夺经济收益等方面。对宋朝治理盗耕种自然资源土地资产的效果，必须区分不同类型的自然资源土地资产和不同的博弈对象,分别加以考察和分析。
【Abstract】In traditional China，rights of natural land resources were divided into different levels ：ownership，possession，usage，operation，supervision，etc. In the Tang Dynasty，the government owned universal jurisdiction and priority rights of natural land resources. In the Song Dynasty，the government made further efforts to place rights of natural land resources under central administration，and to allot，sell or rent these rights to the populace. In the Tang-Song era，especially in the Southern Son Dynasty，out of consideration for greater government tax revenue，the central government formulated policies that people illegally farming natural land resources were not to be punished if only they would pay supplementary taxes. Moreover，the central government gained more special tax income by cracking down on tax evasion，and struggled for tax income against local governments and local tyrants. The effect of governing those illegally farmed natural land resources should be reviewed separately according to different types of natural land resources and different game targets.国家社会科学基金重大项目“中国古代财政体制变革与地方治理模式演变研究”（17ZDA175
Evolution of Lu Xun's Thought on Realistic Literature
No full text俞兆平，厦门大学中文系教授、博士生导师。【中文摘要】抱着启蒙主义、改良人生的宗旨投身文学的鲁迅，秉持的是现实主义文学观念。但学界在论述中多把它视为静止、孤立的形态,而忽略其不同历史时期的演变过程。具体而言:先是偏重于“科学实证”的写实主义阶段，鲁迅认同实证主义哲学的认知原则,追寻对客体对象精确、逼真的观察与反映;再是“在高的意义上的写实主义”阶段，他赞赏陀思妥夫斯基那种进入人的心理、探测人的灵魂深处善与恶的创作方法;后是“现实底理想主义”阶段，他接受了普列哈诺夫的“艺术也是社会现象”的马克思主义基本原理，接纳了卢那察尔斯基从历史发展总趋势的预测中来把握现 实真实——这一后来成为“社会主义的现实主义”的原则。
【Abstract】Lu Xun，who devoted himself to literature for enlightening and improving the life of the Chinese people，adhered to the thought of realistic literature. However，in academic circles，his thought of realistic literature was often described as a static and isolated form，and most scholars ignored the evolution of Lu Xun's thought in different historical periods. Specifically，there are three stages of Lu Xun's thought of realistic literature. Firstly，he emphasized the “scientific positivism” of Realism. He identified with the cognitive principles of positivist philosophy and pursued accurate and realistic observation and reflection of objects. Secondly，in the stage of “realism in a high sense”，he admired Dostovsky's creative method of entering the human's mind and detecting the good and evil in the soul of human beings. Thirdly，in the stage of “realistic idealism ”， he accepted Plekhanov's Marxism that “art is also a social phenomenon ”， and Lunacharsky's principle of grasping reality from the prediction of the general trend of historical development - this later became the principle of “socialist realism”