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Effect of Ca addition on the microstructure and mechanical properties of heat-treated Mg-6.0Zn-1.2Y-0.7Zr alloy

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Journal of Magnesium and Alloys 2021年第5期9卷 1636-1648页

作者： Young Gil Jung Wonseok Yang Yong Joo kim Shae.k.kim Young Ok Yoon Hyunkyu Lim Do Hyang kim Advanced Materials and Process R&D Department Korea Institute of Industrial Technology156Gaetbeol-roIncheon 21999Republic of Korea Department of Metallurgical Engineering Yonsei University50Yonsei-roSeoulSeodaemun-gu 03722Republic of Korea

In this study,the effects of Ca addition on the microstructure,thermal properties,and mechanical properties of a Mg-6.0Zn-1.2Y-0.7Zr(ZWk611)alloy at room temperature and 150℃ were *** an increase in the Ca content,the ignition resistance of the ZWk611 alloy improved and the grains became *** as-cast ZWk611 alloy consisted mainly of the dendriticα-Mg matrix and I-phase(Mg_(3)Zn_(6)Y)at the grain *** the other hand,theτ-(Ca_(2)Mg_(6)Zn_(3))and I-phases were formed in the Ca-added ZWk611 *** fraction of theτ-phase increased with an increase in the Ca *** the solid-solution treatment,these phases remained partially at the grain boundaries of the Ca-added ZWk611 alloys and an additional W-phase(Mg_(3)Zn_(3)Y)was *** phases remaining at the grain boundaries restricted the grain growth through the grain boundary pinning *** aging treatment resulted in the formation of MgZn'precipitates in theα-Mg matrix of the *** precipitates were more uniformly distributed in the Ca-added alloys than in the alloys without ***,the heat treatment-induced precipitation improved the tensile and creep properties of the t6-treated *** t6-treated ZWk611+0.7Ca alloy exhibited the best mechanical properties at room temperature and 150℃ among all the tested alloys.

关键词： Mg-Zn-Y alloys Heat-treatment Precipitate Mechanical properties thermal analysis

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乡镇学校体育教学现状及对策分析

黑河学院学报 2024年第3期15卷 78-80,125页

作者：万传琦 In Jae-kim 黑河学院黑龙江黑河164300 韩国湖西大学忠清南道牙山31499

我国拥有14亿多人口,其中将近4.77亿是农村人口,乡镇学校的体育教学是实现中国体育强国的关键所在,黑河市乡镇学校体育教学现状是各项目不均衡,极大限制了体育教学的全面性。影响体育教学不均衡的主要因素是教育政策、财政支持、师资力... 详细信息

我国拥有14亿多人口,其中将近4.77亿是农村人口,乡镇学校的体育教学是实现中国体育强国的关键所在,黑河市乡镇学校体育教学现状是各项目不均衡,极大限制了体育教学的全面性。影响体育教学不均衡的主要因素是教育政策、财政支持、师资力量及学生兴趣等,需要从管理、教师队伍、硬件设施等方面,贯彻全民健身下的学校体育教育,促进乡镇学校发展体育教育全面发展。

关键词：黑河市乡镇学校农村体育教学

Phase Formation and Magnetic Properties of Nanocomposite Nd-Fe-B Adjusted by Small Amount of Dy and Co

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Journal of Rare Earths 2004年第Z2期22卷 89-94页

作者： t S Jang t W Lim H S Aum D H Lee M B kim Division of Materials and Chemical Engineering Sun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Mechanical EngineeringSun Moon University 100 Kalsan LiTangjung MyonAsan CityChoongnam 336-708Korea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea

In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DtA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (tbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. this phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by Dy and/or Co. the 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. the grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. the grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were iHc=4.85 kOe, Br= 11.32 kG, (BH)max = 15.73 MGOe, and mr=0.73.

关键词： nanocomposite Nd-Fe-B magnetic properties remanence coercivity

Paleozoic tectonic evolution of the proto-korean Peninsula along the East Asian continental margin from detrital zircon U-Pb geochronology and Hf isotope geochemistry

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Geoscience Frontiers 2024年第1期15卷 97-117页

作者： Yirang Jang Sung Won kim Vinod O.Samuel Sanghoon kwon Seung-Ik Park M.Santosh keewook Yi Department of Earth and Environmental Sciences Chonnam National UniversityGwangju 61186Republic of Korea Geology Division Korea Institute of Geoscience and Mineral ResourcesDaejeon 34132Republic of Korea Department of Earth System Sciences Yonsei UniversitySeoul 03722Republic of Korea Department of Geology Kyungpook National UniversityDaegu 41566Republic of Korea School of Earth Sciences and Resources China University of Geosciences BeijingBeijing 100083China Department of Earth Science University of AdelaideAdelaide SA 5005Australia Yonsei Frontiers Lab Yonsei UniversitySeoul 03722Republic of Korea Division of Earth and Environmental Sciences Korea Basic Science InstituteChungbuk 28119Republic of Korea

Detrital zircon geochronology and Hf isotope analysis can be used for inferring provenance characteristics,and to evaluate the tectonic evolution of sedimentary basins and their link with regional *** Paleozoic sequences of the Okcheon Belt consist of the Lower Paleozoic Joseon and the Upper Paleozoic Pyeongan supergroups with Middle Paleozoic hiatus locally on top of the Neoproterozoic bimodal volcanic rocks,reflecting an intracontinental rift setting between the two basements(*** and Yeongnam massifs)at southern part of the korean *** detrital zircon U-Pb ages and Lu-Hf isotope results show that all these Paleozoic strata commonly have Paleoproterozoic and Paleozoic zircon ages with rare Meso-to Neoproterozoic *** individual zircon populations display following features,allowing estimation of their sedimentary provenances:(i)the Paleoproterozoic zircons(ca.1.85 Ga and 2.50 Ga)with similar ranges ofεHf(t)values are most common in the basement rocks of the korean Peninsula,and were sourced from both the Gyeonggi and Yeongnam massifs.(ii)the Meso-to Neoproterozoic zircons,preserved only in the Middle to Late Cambrian clastic sedimentary rocks within the carbonate sequences probably reflect proximal provenance.(iii)the youngest Paleozoic zircons of each formation,almost coincident with their deposition ages,suggest presence of syndepositional magmatism,indicating proximal magmatic sources during their deposition.(iv)the Cambrian-Ordovician zircons,from the Lower Paleozoic sequences,but rare in the successive Upper Paleozoic sequences,suggest a provenance change after the hiatus between the two sedimentary successions.(v)the Permian zircons showing differentεHf(t)values indicate that detrital sources were varied at that *** integrated results in our study suggest provenance variability linked to diverse tectonic environments,reflecting prolonged subduction-related crustal evolution of the proto-korean Peninsula during the Paleozo

关键词： Detrital zircon U-Pb and Hf isotopes Paleozoic metasedimentary rocks Okcheon Belt taebaeksan zone korean Peninsula

A Study of the Weak Shock Wave Propagating over a Porous Wall/Cavity System

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Journal of thermal Science 2005年第4期14卷 329-333页

作者： H.D.kim S.J.JUNG t.AOkI t.SEtOGUCHI School of Mechanical Engineering.Andong National University Songchun-dongAndong 760-746Korea Department of Energy and Environmental Engineering Kyushu University6-1Kasuga-kouenKasugaFukuoka 816-8580Japan Department of Mechanical Engineering Saga University1HonjoSaga 840-8502Japan

the present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity system is investigated with computational fluid dynamics. A total variation diminishing scheme is employed to solve the unsteady, two-dimensional, compressible, Navier-Stokes equations. the Mach number of an initial shock wave is changed in the range from 1.02 to 1.12. Several different types of porous wall/cavity systems are tested to investigate the passive control effects. the results show that wall pressure strongly fluctuates due to diffraction and reflection processes of the shock waves behind the incident shock wave. From the results, it is understood that for effective alleviation of tunnel impulse waves, the length of the perforated region should be sufficiently long.

关键词： compressible flow perforated wall railway tunnel shock wave.

Enhanced Archimedes Optimization Algorithm for Clustered Wireless Sensor Networks

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Computers, Materials & Continua 2022年第10期73卷 477-492页

作者： E.Laxmi Lydia t.M.Nithya k.Vijayalakshmi Jeya Prakash kadambaajan Gyanendra Prasad Joshi Sung Won kim Computer Science and Engineering Vignan’s Institute of Information Technology(Autonomous)Andhra Pradesh530049India Department of Computer Science and Engineering K.Ramakrishnan College of EngineeringTiruchirappalli621112India Department of Electronics&Communication Engineering Saveetha School of EngineeringSaveetha Institute of Medical and Technical SciencesChennai600025India Department of Electronics&Communication Engineering Kalasalingam Academy of Research and EducationKrishnankoil626128India Department of Computer Science and Engineering Sejong UniversitySeoul05006Korea Department of Information and Communication Engineering Yeungnam UniversityGyeongsan-siGyeongbuk-do38541Korea

Wireless sensor networks(WSN)encompass a set of inexpensive and battery powered sensor nodes,commonly employed for data gathering and tracking *** energy utilization of the nodes in WSN is essential to capture data effectively and transmit them to *** latest developments of energy efficient clustering techniques can be widely applied to accomplish energy efficiency in the *** this aspect,this paper presents an enhanced Archimedes optimization based cluster head selection(EAOA-CHS)approach for *** goal of the EAOA-CHS method is to optimally choose the CHs from the available nodes in WSN and then organize the nodes into a set of ***,the EAOA is derived by the incorporation of the chaotic map and pseudo-random ***,the EAOA-CHS technique determines a fitness function involving total energy consumption and lifetime of *** design of EAOA for CH election in the WSN depicts the novelty of *** order to exhibit the enhanced efficiency of EAOA-CHS technique,a set of simulations are applied on 3 distinct conditions dependent upon the place of base station(BS).the simulation results pointed out the better outcomes of the EAOA-CHS technique over the recent methods under all scenarios.

关键词： Wireless sensor network CH selection energy efficiency clustering lifetime

Dimensionality-driven metal to Mott insulator transition in two-dimensional 1t-taSe2

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National Science Review 2024年第3期11卷 108-118页

作者： Ning tian Zhe Huang Bo Gyu Jang Shuaifei Guo Ya-Jun Yan Jingjing Gao Yijun Yu Jinwoong Hwang Cenyao tang Meixiao Wang Xuan Luo Yu Ping Sun Zhongkai Liu Dong-Lai Feng Xianhui Chen Sung-kwan Mo Minjae kim Young-Woo Son Dawei Shen Wei Ruan Yuanbo Zhang State key Laboratory of Surface Physics New Cornerstone Science Laboratory and Department of PhysicsFudan University Shanghai Qi Zhi Institute Shanghai Research Center for Quantum Sciences Institute for Nanoelectronic Devices and Quantum Computing Fudan University Zhangjiang Fudan International Innovation Center Fudan University State key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology(SIMIT)Chinese Academy of Sciences School of Physical Science and technology ShanghaiTech University korea Institute for Advanced Study School of Emerging technology and Department of Physics University of Science and Technology of China Advanced Light Source Lawrence Berkeley National Laboratory Shanghaitech Laboratory for topological Physics key Laboratory of Materials Physics Institute of Solid State Physics Hefei Institutes of Physical ScienceChinese Academy of Sciences High Magnetic Field Laboratory Hefei Institutes of Physical Science Chinese Academy of Sciences Collaborative Innovation Centre of Advanced Microstructures Nanjing University Department of Physics University of Science and Technology of China and Key Laboratory of Strongly Coupled Quantum Matter Physics Chinese Academy of Sciences National Synchrotron Radiation Laboratory University of Science and Technology of China

two-dimensional materials represent a major frontier for research into exotic many-body quantum phenomena. In the extreme two-dimensional limit, electron-electron interaction often dominates over other electronic energy scales, leading to strongly correlated effects such as quantum spin liquid and unconventional *** dominance is conventionally attributed to the lack of electron screening in the third dimension. Here, we discover an intriguing metal to Mott insulator transition in 1t-taSe2that defies conventional wisdom. Specifically, we find that dimensionality crossover, instead of reduced screening, drives the transition in atomically thin 1t-taSe2. A dispersive band crossing the Fermi level is found to be responsible for the bulk metallicity in the material. Reducing the dimensionality,however, effectively quenches the kinetic energy of these initially itinerant electrons, and drives the material into a Mott insulating *** dimensionality-driven metal to Mott insulator transition resolves the long-standing dichotomy between metallic bulk and insulating surface of 1t-taSe2. Our work further reveals a new pathway for modulating two-dimensional materials that enables exploring strongly correlated systems across uncharted parameter space.

关键词： two-dimensional materials 1t-taSe2 dimensionality crossover metal to Mott insulator transition

IL-17,a new kid on the block of tertiary lymphoid organs

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Cellular & Molecular Immunology 2012年第1期9卷 3-4页

作者： theresa t Lu Hajeong kim Xiaojing Ma Autoimmunity and Inflammation Program and Pediatric Rheumatology Hospital for Special SurgeryNew YorkNYUSA Department of Microbiology and Immunology Weill Cornell Medical CollegeNew YorkNYUSA

t ertiary lymphoid organs(tLOs)are structures that resemble lymph nodes that can be found in chronically inflamed tissues in a number of inflammatory *** can host ongoing immune responses that can potentially contribute to disease *** development of tLOs has been thought in large part to recapitulate the development of secondary lymphoid organs,but the regulation of tLO development has not been well *** a recent article in Nature Immunology,troy Randall and colleagues1 identify IL-17,a cytokine that contributes to the pathogenesis of a number of inflammatory diseases,as a novel critical player in tLO formation in inflamed *** can be found in the joints of patients with rheumatoid arthritis,in the inflamed salivary glands of patients with Sjogren’s syndrome,in the meninges of patients with multiple sclerosis,and in the lungs of patients with pulmonary inflammation or *** the lungs,induced bronchus-associated lymphoid tissues(iBALts)are tLOs that are located along the small airways.

关键词： organs lymphoid pathogenesis

Biofilm three-dimensional architecture influences in situ pH distribution pattern on the human enamel surface

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International Journal of Oral Science 2017年第2期9卷 74-79页

作者： Jin Xiao Anderson t Hara Dongyeop kim Domenick t Zero Hyun koo Geelsu Hwang Eastman Institute for Oral Health University of Rochester Medical Center Department of Cariology Operative Dentistry and Dental Public HealthOral Health Research InstituteIndiana University School of Dentistry Biofilm Research Laboratories Levy Center for Oral HealthDepartment of Orthodontics and Divisions of Pediatric Dentistry & Community Oral HealthSchool of Dental MedicineUniversity of Pennsylvania

to investigate how the biofilm three-dimensional(3D) architecture influences in situ pH distribution patterns on the enamel surface. Biofilms were formed on human tooth enamel in the presence of 1% sucrose or 0.5% glucose plus 0.5% fructose. At specific time points, biofilms were exposed to a neutral pH buffer to mimic the buffering of saliva and subsequently pulsed with 1% glucose to induce re-acidification. Simultaneous 3D pH mapping and architecture of intact biofilms was performed using two-photon confocal microscopy. the enamel surface and mineral content characteristics were examined successively via optical profilometry and microradiography analyses. Sucrose-mediated biofilm formation created spatial heterogeneities manifested by complex networks of bacterial clusters(microcolonies). Acidic regions(pHthe interior of microcolonies,which impedes rapid neutralization(taking more than 120 min for neutralization). Glucose exposure rapidly re-created the acidic niches, indicating formation of diffusion barriers associated with microcolonies structure. Enamel demineralization(white spots),rougher surface, deeper lesion and more mineral loss appeared to be associated with the localization of these bacterial clusters at the biofilm-enamel interface. Similar 3D architecture was observed in plaque-biofilms formed in vivo in the presence of sucrose. the formation of complex 3D architectures creates spatially heterogeneous acidic microenvironments in close proximity of enamel surface, which might correlate with the localized pattern of the onset of carious lesions(white spot like) on teeth.

关键词： biofilms demineralization dental caries exopolysaccharides microcolonies pH microenvironments plaque Streptococcus mutans