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Collapse behavior evaluation of hybrid thin-walled member by stacking condition

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 135-140页

作者： kil-sung lee Hyeon-Kyeong SEO Yong-June YANG Woo-Chae HWANG Kwang-Hee IM In-Young YANG R&D Center Dacc LTD. 948-13 Dunsan-ri Bongdong-eup Wanju-gun Jeonbuk 565-902 Korea Departments of Advanced Parts and Materials Engineering Graduate School Chosun University Department of Automotive Engineering Woosuk University Departments of Mechanical Design Engineering Chosun University

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

关键词： collapse behavior aluminum and CFRP hybrid thin-walled member stacking condition

ULTRASONIC INFLUENCE OF POROSITY LEVEL ON CFRP COMPOSITE LAMINATES USING RAYLEIGH PROBE WAVES

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Acta Mechanica Solida Sinica 2008年第4期21卷 298-307页

作者： Je-Woong Park Do-Jung Kim Kwang-Hee Im Sang-Kyu Park David K.Hsu Adam H.Kite Sun-Kyu Kim kil-sung lee In-Young Yang Dept.of Naval Architecture and Ocean Eng. Chosun UniversityKwangju 501-759Korea Dept.of Automotive Eng. Woosuk UniversitySamrae-upWanju-kunChonbuk565-701Korea Center for Nondestructive Evaluation Iowa State UniversityAmesIowa 50011USA Division of Precision Mec.Eng. Chonbuk National UniversityJeonju 561-756Korea School of Mechanical Engineering Chosun UniversityKwangju 501-759Korea

It was found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites （damages, fiber orientation, low level porosity, ply waviness, and cracks）. Both the strength and stiffness depend on the fiber orientation and porosity volume in the composites. The porosity content of a composite structure is critical to the strength and performance of the structure in general. The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head- to-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. A free software package was utilized to process micrograph images of the test sample. The results from the image processing method were compared with existing data. Beam profile was characterized in unidirectional CFRP（carbon fiber reinforced plastics） using pitch-catch Rayleigh probes and the one-sided pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner.

关键词： ply-layup orientation unidirectional CFRP beam profile pitch-catch contact mode,porosity level

Experience of Mental Health Professionals Collaborating with Peer Supporters in a Community Mental Health Service Team

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International Journal of Mental Health Promotion 2024年第4期26卷 251-260页

作者： Sowon lee Boyoung Kim Chung kil Park College of Nursing Chonnam National UniversityGwangju61469South Korea College of Oriental Medicine Wonkwang UniversityIksan54538South Korea

This study explored how mental health professionals collaborate with peer supporters with mental disabilities in a community mental health *** January 19 to February 23,2021,three 60 min interviews were conducted with six mental health professionals working at a Korean community *** results were qualitatively analyzed and divided into four themes and eight *** four themes were the perceptions of and challenges in working with peer supporters with mental disabilities,conflict and confusion about working with peer supporters,forming partnerships with peer supporters,and policy support for peer supporters’job *** reported vague anxiety about working with a peer supporter and difficulties with the trial-and-error process of adjusting to the role as *** time,however,they realized that they needed to make an effort to develop meaningful relationships with peer supporters and mental health ***,through this study,we realized that there was a need to improve the system,such as building infrastructure for job stability for peer support workers and capacity building tailored to the mental *** peer supporters play various roles while working with mental health professionals,this study showed the possibility of mutual growth through communication and *** findings will help prepare systems necessary for collaboration between the two teams amidst the increasing institutionalization of peer support for mental disorders.

关键词： Peer supporters mental health mental health professionals collaborating

Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

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Journal of Magnesium and Alloys 2024年第2期12卷 779-793页

作者： Sumi Jo Gyo Myeong lee Jong Un lee Young Min Kim sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Magnesium Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al *** extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air *** extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during *** to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser *** AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,***,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and *** bending,a macrocrack initiates on the outer surface of bending specimen in both *** AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 *** bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the *** bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relation

关键词： Mg–Al alloy Extrusion Bending Precipitation Microstructure

Enhanced prediction of anisotropic deformation behavior using machine learning with data augmentation

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Journal of Magnesium and Alloys 2024年第1期12卷 186-196页

作者： Sujeong Byun Jinyeong Yu Seho Cheon Seong Ho lee sung Hyuk Park Taekyung lee School of Mechanical Engineering Pusan National UniversityBusan 46241South Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566South Korea

Mg alloys possess an inherent plastic anisotropy owing to the selective activation of deformation mechanisms depending on the loading *** characteristic results in a diverse range of flow curves that vary with a deformation *** study proposes a novel approach for accurately predicting an anisotropic deformation behavior of wrought Mg alloys using machine learning(ML)with data *** developed model combines four key strategies from data science:learning the entire flow curves,generative adversarial networks(GAN),algorithm-driven hyperparameter tuning,and gated recurrent unit(GRU)*** proposed model,namely GAN-aided GRU,was extensively evaluated for various predictive scenarios,such as interpolation,extrapolation,and a limited dataset *** model exhibited significant predictability and improved generalizability for estimating the anisotropic compressive behavior of ZK60 Mg alloys under 11 annealing conditions and for three loading *** GAN-aided GRU results were superior to those of previous ML models and constitutive *** superior performance was attributed to hyperparameter optimization,GAN-based data augmentation,and the inherent predictivity of the GRU for *** a first attempt to employ ML techniques other than artificial neural networks,this study proposes a novel perspective on predicting the anisotropic deformation behaviors of wrought Mg alloys.

关键词： Plastic anisotropy Compression Annealing Machine learning Data augmentation

Comparison of commercial silicon-based anode materials for the design of a high-energy lithium-ion battery

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Nano Research 2024年第6期17卷 5270-5277页

作者： Minhong Choi Eunhan lee Jaekyung sung Namhyung Kim Minseong Ko Division of Convergence Materials Engineering Pukyong National UniversityBusan 48547Republic of Korea Department of Materials Engineering and Convergence Technology Gyeongsang National University501 Jinju-daeroJinju 52828Republic of Korea Department of Materials System Engineering Pukyong National UniversityBusan 48547Republic of Korea

Silicon(Si)is considered a potential alternative anode for next-generation Li-ion batteries owing to its high theoretical capacity and ***,the commercial use of Si anodes is hindered by their large volume expansion(~300%).Numerous efforts have been made to address this *** these efforts,Si-graphite co-utilization has attracted attention as a reasonable alternative for high-energy anodes.A comparative study of representative commercial Si-based materials,such as Si nanoparticles,Si suboxides,and Si−Graphite composites(SiGC),was conducted to characterize their overall performance in high-energy lithium-ion battery(LIB)design by incorporating conventional ***-Si was found to exhibit poor electrochemical performance,with severe volume expansion during *** suboxide provided excellent cycling stability in a full-cell evaluation with stable volume variation after 50 cycles,but had a large irreversible capacity and remarkable volume expansion during the first *** displayed a good initial Coulombic efficiency and the lowest volume change in the first cycle owing to the uniformly distributed nano-Si layer on graphite;however,its long-term cycling stability was relatively *** complement each disadvantage of Si suboxide and SiGC,a new combination of these Si-based anodes was suggested and a reasonable improvement in overall battery performance was successfully achieved.

关键词： silicon-based anode high-energy comparison lithium ion battery blended electrode

Strengthening mechanisms analysis and tailoring of bimodal grain structures for enhanced strength in CoCrFeMnNi high-entropy alloys

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Rare Metals 2024年第8期43卷 3893-3903页

作者： Jaesoung lee Seulgi Kim Taehyun Kwon Young II Kim Suyeon Kim sung Ho Song Bin lee Dongju lee Department of Urban Energyand Environmental EngineeringChungbuk National UniversityCheongju 28644Republic of Korea Division of Advanced Materials Engineering Kongju National UniversityChungnam 330-717Republic of Korea Department of Advanced Materials Engineering for Information and Electronics Integrated-Education Institute for Frontier Science and Technology(BK21 Four)Kyung Hee UniversityYongin17104Republic of Korea

The CoCrFeMnNi high-entropy alloys(HEAs)with a(face-centered cubic) FCC structure has garnered considerable attention for its exceptional ductility and strain hardening ***,its yield strength is insufficient for structural *** this study,strengthening mechanisms in these HEAs were investigated to gain insight into the mechanical properties according to alloy powder ***,we present a novel approach to achieve both high strength and high ductility through the creation of a bimodal structure consisting of both coarse and fine grains via gas atomization and spark plasma sintering processes.A bimodally structured HEA prepared with a mass ratio of 2:8 between coarse particles(75-106 μm) and fine particles(≤25 μm)yielded optimal results,with a strength of 491.95 MPa and elongation of 19.64%.This strength value represents an~41% increase compared with the sample that displayed a fine single microstructure(347.08 MPa for yield strength).The strength enhancement was attributed to the prevention of plastic deformation initiation from the fine particles during *** innovative approach to the creation of HEAs with bimodal structures shows promise for various applications,such as structural components that require a combination of high strength and high ductility.

关键词： High-entropy alloys CrCoFeMoNi Bimodal Gas atomization Mechanical properties

Catalpa bignonioides extract improves exercise performance through regulation of growth and metabolism in skeletal muscles

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Asian Pacific Journal of Tropical Biomedicine 2024年第2期14卷 47-54页

作者： Hoibin Jeong Dong-joo lee sung-Pil Kwon SeonJu Park Song-Rae Kim Seung Hyun Kim Jae-Il Park Deug-chan lee Kyung-Min Choi WonWoo lee Ji-Won Park Bohyun Yun Su-Hyeon Cho kil-Nam Kim Seoul Center Korea Basic Science InstituteSeoul 02841Republic of Korea Chuncheon Center Korea Basic Science InstituteChuncheon 24341Republic of Korea Research&Development Center Chungdam CDC JNPharm LLC.Chuncheon 24341Republic of Korea Department of Biomedical Technology Kangwon National UniversityChuncheon 24341Republic of Korea Yonsei Institute of Pharmaceutical Sciences College of PharmacyYonsei UniversityIncheon 21983Republic of Korea Gwangju Center Korea Basic Science InstituteGwangju 61751Republic of Korea Honam National Institute of Biological Resources 99Gohadoan-gilMokpo-siJeollanam-do58762Republic of Korea Department of Bio-analysis Science University of Science&TechnologyDaejeon34113Republic of Korea

Objective:To evaluate the effects of Catalpa bignonioides fruit extract on the promotion of muscle growth and muscular capacity in vitro and in ***:Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide *** proliferation was assessed using a 5-bromo-2’-deoxyuridine(BrdU)assay *** blot analysis was performed to determine the protein expressions of related *** effects of Catalpa bignonioides extract were investigated in mice using the treadmill exhaustion test and whole-limb grip strength *** composition analysis was performed using high-performance liquid chromatography(HPLC).Results:Catalpa bignonioides extract increased the proliferation of C2C12 mouse myoblasts by activating the Akt/mTOR signaling *** also induced metabolic changes,increasing the number of mitochondria and glucose metabolism by phosphorylating adenosine monophosphate-activated protein *** an in vivo study,the extract-treated mice showed improved motor abilities,such as muscular endurance and grip ***,HPLC analysis showed that vanillic acid may be the main component of the Catalpa bignonioides extract that enhanced muscle ***:Catalpa bignonioides improves exercise performance through regulation of growth and metabolism in skeletal muscles,suggesting its potential as an effective natural agent for improving muscular strength.

关键词： Catalpa bignonioides Skeletal muscle Cell proliferation Mitochondria Energy metabolism C2C12

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(Science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun Kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa lee Joong Wook lee Jae Hee sung Seong Ku lee Ki-Yong Kim Advanced Photonics Research Institute GISTGwangju61005Korea Department of Physics and Optoelectronics Convergence Research Center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangju61005Korea Institute for Research in Electronics and Applied Physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched