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Populating ^(229m)Th via two-photon electronic bridge mechanism

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Nuclear Science and Techniques 2021年第6期32卷 45-53页

作者： Neng-Qiang Cai Guo-Qiang Zhang chang-Bo Fu Yu-Gang Ma Shanghai Tech University Shanghai 201210China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China Key Laboratory of Nuclear Physics and Ion-beam Application(moe) Institute of Modern PhysicsFudan UniversityShanghai 200433China

The isomer ^(229m)Th is the most promising candidate for clocks based on the nuclear transition because it has the lowest excitation energy of only 8.10±0.17 *** experiments and theories have focused on methods of triggering the transition between the ground state and isomeric state,among which the electronic bridge(EB)is one of the most *** this paper,we propose a new electronic bridge mechanism via two-photon excitation based on quantum optics for a two-level nuclear quantum *** long-lived 7 s1/2 electronic shell state of^(229m)Th^(3+),with a lifetime of approximately 0.6 s,is chosen as the initial state and the atomic shells(7 s-10 s)could be achieved as virtual states in a two-photon *** the virtual states return to the initial state 7 s1/2,there is a chance of triggering the nucleus 229Th^(3+),to its isomeric state ^(229m)Th ^(3+),via *** lasers at moderate intensity((10^(10)-10^(14))W/m^(2)),with photon energies near the optical range,are expected to populate the isomer at a saturated rate of approximately 10^(9) s^(-1),which is much higher than that due to other *** believe that this twophoton EB scheme can help in the development of nuclear clocks and deserves verification via a series of experiments with ordinary lasers in laboratories.

关键词： Electronic bridge ^(229)mTh Nuclear clocks Two-photon excitation

High-temperature deoxygenation-created highly porous graphitic carbon nanosheets for ultrahigh-rate supercapacitive energy storage

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Journal of Energy Chemistry 2022年第8期31卷 521-527,I0014页

作者： Xuan Wang Shanyong Chen chang Liu Yi Yu Mingjiang Xie Xuefeng Guo Key Lab of Mesoscopic Chemistry moe School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210093JiangsuChina Hubei Key Laboratory for Processing and Application of Catalytic Materials Huanggang Normal UniversityHuanggang 438000HubeiChina

Developing carbon-based supercapacitors with high rate capability is of great importance to meet the emerging demands for devices that requires high energy density as well as high power ***,it is hard to fabricate a nanocarbon with high electro-active surface area meanwhile maintaining superior conductivity to ensure the high rate capability since excellent conductivity is usually realized by high temperature graphitization,which would lead to the structural collapse and sintering resulting in low surface ***,we reported a highly porous graphitic carbon nanosheet with an unprecedented rate capability of 98%of its initial capacitance from 0.5 to 50 A/g for ultrahigh-rate supercapacitive energy *** hierarchical mesoporous carbon nanosheets(HMCN)were fabricated by a template induced catalytic graphitization approach,in which sheet-like Mg(OH)_(2) was employed as catalytic template in situ catalytically polymerizing of catechol and formaldehyde and catalytically graphitizing of the formed carbon *** the co-effect of template(avoiding the sintering)and the deoxygenation(creating the pores)during the high temperature graphitization process,the obtained HMCN material possesses nanosheet morphology with highly porous graphitic microstructure rich in mesoporosity,large in surface area(2316 m^(2)/g),large in pore volume(3.58 cm^(3)/g)and excellent in conductivity(109.8 S/cm).In 1.0 M TEABF_(4)/AN,HMCN exhibits superior supercapacitive performance including large energy density of 52.2 Wh/kg at high power density of 118 k W/kg,long-cycling stability and excellent rate capability,making HMCN a promising electrode material for supercapacitor devices.

关键词： Hierarchical mesoporosity Carbon nanosheet Spontaneous polymerization Supercapacitor

高频列车荷载作用下板式无砟轨道垂向应力衰减特性

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铁道建筑 2024年第9期64卷 22-28页

作者：王彬宇岳朝阳刘卫星王志璇徐畅赵坪锐西南交通大学高速铁路线路工程教育部重点实验室成都610031 西南交通大学土木工程学院成都610031

为了优化无砟轨道结构设计并为确定动力系数取值提供参考,以CRTSⅠ型板式无砟轨道为研究对象,采用LS-DYNA软件建立车辆-轨道耦合动力学模型,分析了不同速度级时车轮扁疤和焊缝激励下的轮轨垂向力时频特征,阐明了轮轨垂向力随车速的变化... 详细信息

为了优化无砟轨道结构设计并为确定动力系数取值提供参考,以CRTSⅠ型板式无砟轨道为研究对象,采用LS-DYNA软件建立车辆-轨道耦合动力学模型,分析了不同速度级时车轮扁疤和焊缝激励下的轮轨垂向力时频特征,阐明了轮轨垂向力随车速的变化规律;进而分析了轨道结构垂向应力沿深度的变化规律,计算了轨道结构动力系数并揭示了动力系数沿轨道结构深度的变化规律。结果表明:车速在400 km/h内,车轮扁疤不平顺作用下轮轨垂向力主频大于500 Hz,而焊缝不平顺作用下轮轨垂向力存在两个主频,较高的主频大于500 Hz,较低的主频处于(49.9±10)Hz内;高频列车荷载下的轨道垂向应力沿着轨道结构深度衰减明显,轨道板底部的垂向应力约为轨道板顶部的15%,底座板底部的垂向应力约为轨道板顶部的4%;轨道结构动力系数沿轨道结构深度显著降低,在钢轨至轨道板之间衰减约40%,底座板底部动力系数比钢轨上减小约50%。建议适当降低高频列车荷载作用下无砟轨道设计和检算动力系数。

关键词：高速铁路无砟轨道动力衰减特性车轮扁疤不平顺焊缝不平顺垂向应力动力系数

A Compound Algorithm of Denoising Using Second-Order and Fourth-Order Partial Differential Equations

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Numerical Mathematics(Theory,Methods and Applications) 2009年第4期2卷 353-376页

作者： Qianshun chang Xuecheng Tai Lily Xing Institute of Applied Mathematics Academy of Mathematics and Systems Sciences Chinese Academy of Sciences Beijing China School of Physical and Mathematical Sciences Nanyang Technological University SPMS-04-01 21 Nanyang Link Singapore 637371 Department of Mathematics University of Bergen Johannes Brunsgate 12 5008 Bergen Norway

In this paper, we propose a compound algorithm for the image restoration. The algorithm is a convex combination of the ROF model and the LLT model with a parameter function 0. The numerical experiments demonstrate that our compound algorithm is efficient and preserves the main advantages of the two models. In particular, the errors of the compound algorithm in L2 norm between the exact images and corresponding restored images are the smallest among the three models. For images with strong noises, the restored images of the compound algorithm are the best in the corresponding restored images. The proposed algorithm combines the fixed point method, an improved AMG method and the Krylov acceleration. It is found that the combination of these methods is efficient and robust in the image restoration.

关键词： Algorithm of denoising image restoration total variation second-order functional.

Liquid Crystalline Microdroplets of Graphene Oxide via Microfluidics

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Chinese Journal of Polymer Science 2021年第12期39卷 1657-1664页

作者： Piao Ma Peng Li Ya Wang Dan chang Wei-Wei Gao Chao Gao moe Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringKey Laboratory of Adsorption and Separation Materials Technologies of Zhejiang ProvinceZhejiang UniversityHangzhou 310027China

Study of stable liquid crystal(LC)microdroplets is of great significance for LC dynamics in con fined space or at topological ***,the fabrication of LC microdroplets with diverse shape without ionic gelati on agents still remai ns challe nging due to the fluid ***,we utilize the microfluidic tech no logy to prepare graphe ne oxide(GO)LC microdroplets with various morphologies based on the anomalous rheological property of GO aqueous *** from LC of one-dimensional polymer,LC containing two-dimensional GO sheets exhibits considerable viscoelasticity and weak extensibility,resulting from the planar molecular conformation and the absence of intermolecular entangleme *** low exte risibility ensures that GO aqueous suspension is discretized into mono dispersed microdroplets rather than thin thread in the microfluidic *** large viscoelasticity and ultra-1 ong relaxation time of GO LC enable the diverse stable morphologies of *** droplet morphology is well con trolled from sphere to teardrop by modulati ng the competition between GO viscoelasticity and in terfacial ten *** two-dimensional GO LC featuri ng unique rheological property provides a novel system for the microfluidic field,and corresponding topological stability enriches the LC dyn amics and ope ns a new pathway for desig ning graphe ne-based materials.

关键词： Graphene oxide Liquid crystal Microdroplets Microfluidics

Selective laser melting of bulk immiscible alloy with enhanced strength:Heterogeneous microstructure and deformation mechanisms

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Journal of Materials Science & Technology 2022年第9期104卷 81-87页

作者： Shengfeng Zhou Min Xie changyi Wu Yanliang Yi Dongchu Chen Lai-chang Zhang moe Key Lab of Disaster Forecast and Control in Engineering Jinan UniversityGuangzhou 510632China School of Materials Science and Engineering Tianjin Polytechnic UniversityTianjin 300387China Department of Educational Science Hunan First Normal UniversityChangsha 410205China School of Materials Science and Energy Engineering Foshan UniversityFoshan 528225China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain ***,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu *** heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic ***,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.

关键词： Immiscible alloy Selective laser melting Heterogeneous microstructure Nanotwins Stacking faults

Intermarriage between amorphous and polycrystalline materials in perovskite solar cells:positive or not?

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Journal of Energy Chemistry 2022年第3期31卷 525-528,I0014页

作者： Ying Tan Xueqing chang Bing-Xin Lei Wu-Qiang Wu Key Laboratory of Bioinorganic and Synthetic Chemistry(moe) School of ChemistrySun Yat-sen UniversityGuangzhou 510006GuangdongChina Key Laboratory of Electrochemical Energy Storage and Energy Conversion of Hainan Province School of Chemistry and Chemical EngineeringHainan Normal UniversityHaikou 571158HainanChina

In recent few years,the research field of perovskite solar cells(PSCs)has witnessed an unprecedentedly rapid advancement in terms of skyrocketed power conversion efficiencies(PCEs)owing to the appealing optoelectronic... 详细信息

关键词： coefficient. perovskite amorphous

Emerging material platforms for integrated microcavity photonics

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Science China(Physics,Mechanics & Astronomy) 2022年第10期65卷 10-28页

作者： Jin Liu Fang Bo Lin chang Chun-Hua Dong Xin Ou Blake Regan Xiaoqin Shen Qinghai Song Baicheng Yao Wenfu Zhang chang-Ling Zou Yun-Feng Xiao State Key Laboratory of Optoelectronic Materials and Technologies School of PhysicsSun Yat-sen UniversityGuangzhou 510000China moe Key Laboratory of Weak-Light Nonlinear Photonics TEDA Institute of Applied Physics and School of PhysicsNankai UniversityTianjin 300071China State Key Laboratory of Advanced Optical Communications System and Networks School of ElectronicsPeking UniversityBeijing 100871China CAS Key Lab of Quantum Information University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Functional Material for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050China School of Mathematical and Physical Sciences University of Technology SydneyUltimo 2007Australia School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System Harbin Institute of TechnologyShenzhen 518055China Key Laboratory of Optical Fiber Sensing and Communications(Ministry of Education) University of Electronic Science and Technology of ChinaChengdu 611731China State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi’an 710119China State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics School of PhysicsPeking UniversityBeijing 100871China

Many breakthroughs in technologies are closely associated with the deep understanding and development of new material *** the main material used in microelectronics,Si also plays a leading role in the development of integrated *** indirect bandgap,absence ofχ(2)nonlinearity and the parasitic nonlinear absorptions at the telecom band of Si imposed technological bottlenecks for further improving the performances and expanding the functionalities of Si microcavities in which the circulating light intensity is dramatically *** past two decades have witnessed the burgeoning of the novel material platforms that are compatible with the complementary metal-oxide-semiconductor(COMS)*** particular,the unprecedented optical properties of the emerging materials in the thin film form have resulted in revolutionary progress in microcavity *** this review article,we summarize the recently developed material platforms for integrated photonics with the focus on chip-scale microcavity *** material characteristics,fabrication processes and device applications have been thoroughly discussed for the most widely used new material *** also discuss open challenges and opportunities in microcavity photonics,such as heterogeneous integrated devices,and provide an outlook for the future development of integrated microcavities.

关键词： microcavity integrated optics nonlinear optics

Electrochemical impedance spectroscopy study on the corrosion of the weld zone of 3Cr steel welded joints in CO_2 environments

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International Journal of Minerals,Metallurgy and Materials 2015年第5期22卷 500-508页

作者： Li-ning Xu Jin-yang Zhu Min-xu Lu Lei Zhang Wei chang Corrosion and Protection Center Key Laboratory for Environmental Fracture (MOE) Institute for Advanced Materials and Technology University of Science and Technology Beijing CNOOC Research Institute

The welded joints of 3Cr pipeline steel were fabricated with commercial welding wire using the gas tungsten arc welding （GTAW） technique. Potentiodynamic polarization curves, linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EIS）, scan- ning electron microscopy （SEM）, and energy-dispersive spectrometry （EDS） were used to investigate the corrosion resistance and the growth of a corrosion film on the weld zone （WZ）. The changes in electrochemical characteristics of the film were obtained through fitting of the EIS data. The results showed that the average corrosion rate of the WZ in CO2 environments first increased, then fluctuated, and finally de- creased gradually. The formation of the film on the WZ was divided into three stages： dynamic adsorption, incomplete-coverage layer forma- tion, and integral layer formation.

关键词： petroleum pipelines steel corrosion welded joints carbon dioxide electrochemical impedance spectroscopy