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Journal of Magnesium and Alloys 2022年第9期10卷 2516-2533页

作者： Man Soo Joun Mohd Kaswandee Razali Jae Dong Yoo min cheol kim Jeong Muk Choi ReCAFT Gyeongsang National UniversityGraduate School of Mechanical and Aerospace EngineeringJinju 52828South Korea Gyeongsang National University Graduate School of Mechanical and Aerospace EngineeringJinju 52828South Korea MFRC Research CenterJinju 52818South Korea Jinhap Daejeon 34302South Korea

Here,we developed novel extended piecewise bilinear power law(C-m)models to describe flow stresses under broad ranges of strain,strain rate,and temperature for mechanical and metallurgical calculations during metal forming at elevated *** traditional C-m model is improved upon by formulating the material parameters C and m,defined at sample strains and temperatures as functions of the strain *** coefficients are described as a linear combination of the basis functions defined in piecewise patches of the sample strain and temperature domain.A comparison with traditional closed-form function flow models revealed that our approach using the extended piecewise bilinear C-m model is superior in terms of accuracy,ease of use,and adaptability;additionally,the extended C-m model was applicable to numerical analysis of mechanical,metallurgical,and microstructural ***,metallurgy-related values can be calculated directly from the flow stress *** the proposed model was developed for materials at elevated temperatures,it can be applied over a broad temperature range.

关键词： Flow stress Power law model Piecewise bilinear function Numerical analysis Microstructural prediction Peak strain

Ultra-flexible graphene/nylon/PDMS coaxial fiber-shaped multifunctional sensor

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Nano Research 2023年第4期16卷 5541-5547页

作者： Peddathimula Puneetha Siva Pratap Reddy Mallem Sung cheol Park Seoha kim Dong Hun Heo cheol min kim Jaesool Shim Sung Jin An Dong-Yeon Lee Kwi-Il Park Department of Robotics and Intelligent Machine Engineering/College of Mechanical and IT Engineering Yeungnam UniversityGyeongsan 38541Republic of Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Advanced Material Research Center Kumoh National Institute of TechnologyGumi 39177Republic of Korea School of Mechanical Engineering Yeungnam UniversityGyeongsan 38541Republic of Korea Department of Materials Science and Engineering Kumoh National Institute of TechnologyGumi 39177Republic of Korea

The development of flexible and wearable devices is mainly required for tactile sensing;as such devices can adapt to complicated nonuniform surfaces,they can be applied to the human ***,it remains necessary to simultaneously achieve small-scale,portable,and stable developments in such ***,this work aims at fabricating a novel,lightweight,ultra-flexible,and fiber-shaped coaxial structure with a diameter of 0.51 mm using polydimethylsiloxane/graphene/nylon material,based on piezoresistive and triboelectric *** piezoresistive-based robotic-hand-controlled sensor thus realized exhibits a response time of 120 ms and a fast recovery time of 55 ***,the piezoresistive-based sensors effectively feature whisker/joystick-guided behaviors and also sense the human finger *** to the triboelectric-based selfpowered nanogenerator behavior,the resulting sensor can convert mechanical motion into electrical energy,without adversely affecting human ***,this triboelectric-based human finger sensor can be operated under different bending modes at specific ***,this multifunctional sensor is cost-effective and suitable for various applications,including robotichand-controlled operations in medical surgery,whisker/joystick motions in lightweight drone technology,and navigation with highsensitivity components.

关键词： extremely lightweight ultra-flexible piezoresistive/triboelectric sensor human-machine whisker

Solution-flame hybrid synthesis of defect-enriched mesoporous CuO_(x) nanowires for enhanced electrochemical nitrate-to-ammonia production

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Journal of Energy Chemistry 2024年第12期99卷 475-483页

作者： Li Qu Sungkyu kim Runfa Tan Arumugam Sivanantham Seokgi kim Yoo Jae Jeong min cheol kim Seong Sik Shin Uk Sim In Sun Cho Department of Materials Science&Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Energy Systems Research Ajou UniversitySuwon 16499Republic of Korea Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 05006Republic of Korea Department of Chemistry Sookmyung Women's UniversitySeoul 04310Republic of Korea Department of Nano Engineering and Department of Nano Science and Technology SKKU Advanced Institute of Nanotechnology(SAINT)Sungkyunkwan UniversitySuwonRepublic of Kore SKKU Institute of Energy Science and Technology(SIEST) Sungkyunkwan UniversitySuwonRepublic of Kore School of Energy Technology Korea Institute of Energy Technology(KENTECH)Jeonnam 58217Republic of Korea

Electrochemical nitrate reduction(ENR)is an economical and eco-friendly method for converting industrial wastewater into valuable ammonia under atmospheric *** main challenge lies in designing and developing highly durable ENR *** study introduces defect-rich mesoporous CuO_(x) nanowires electrocatalyst synthesized using a novel solution-flame(sol-flame)hybrid method to control mesoporosity and introduce surface defects,thereby enhancing the electrochemical nitrate-toammonia production *** found surface defects(oxygen vacancies and Cu^(+))and unique mesoporous nanowire structure composed of tightly interconnected *** sol-flamesynthesized CuO_(x) nanowires(sf-CuO NWs)achieved superior ammonia yield rate(0.51 mmol h^(-1)cm^(-2)),faradaic efficiency(97.3%),and selectivity(86.2%)in 1 M KOH electrolyte(2000 ppm nitrate).This performance surpasses that of non-porous and less-defective CuO NWs and is attributed to the increased surface area and rapid electron transport facilitated by the distinctive morphology and generated *** calculation further suggests oxygen vacancies enhance NO_(3)^(-)adsorption on the sf-CuO NWs’surface and mitigate the competing hydrogen evolution *** study outlines a strategic design and simple synthesis approach for nanowire electrocatalysts that boost the efficiency of electrochemical nitrate-to-ammonia conversion.

关键词： CuO nanowires Solution-flame Mesoporous Oxygen vacancy Electrochemical nitrate reduction Wastewater

Dual function of a high-contrast hydrophobic-hydrophilic coating for enhanced stability of perovskite solar cells in extremely humid environments

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Nano Research 2017年第11期10卷 3885-3895页

作者： Jin Sun Yoo Gill Sang Han Seongha Lee min cheol kim Mansoo Choi Hyun Suk Jung Jung-Kun Lee School of Advanced Materials Science amp Engineering Sungkyunkwan University Suwon 440-746 Republic of Korea Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Department of Mechanical and Aerospace Engineering Seoul National University Seoul 08826 Republic of Korea

In spite of a continuous increase in their power conversion efficiency （PCE） and an economically viable fabrication process,organic-inorganic perovskite solar cells （PSCs） pose a significant problem when used in practical applications：They show fast degradation of the PCE when exposed to very humid *** this study,the stability of PSCs under very humid conditions is greatly enhanced by coating the surface of the PSC devices with a multi-layer film consisting of ultrahydrophobic and relatively hydrophilic layers.A hydrophobic composite of poly（methyl methacrylate）（PMMA）,polyurethane （PU）,and SiO2 nanoparticles successfully retards the water molecules from very humid ***,the hydrophilic layer with moderately PMMA captures the residual moisture within the perovskite layer;subsequently,the perovskite layer *** dual function of the coating film keeps the PCE of PSCs at 17.3% for 180 min when exposed to over 95% humidity.

关键词： perovskite solar cell stability surface coating ultrahydrophobic self-recovery

High-throughput computational-experimental screening protocol for the discovery of bimetallic catalysts

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npj Computational Materials 2021年第1期7卷 1232-1241页

作者： Byung Chul Yeo Hyunji Nam Hyobin Nam min-cheol kim Hong Woo Lee Sung-Chul kim Sung Ok Won Donghun kim Kwan-Young Lee Seung Yong Lee Sang Soo Han Computational Science Research Center Korea Institute of Science and TechnologySeoulRepublic of Korea Department of Energy Resources Engineering Pukyong National UniversityBusanRepublic of Korea Materials Architecturing Research Center Korea Institute of Science and TechnologySeoulRepublic of Korea Department of Chemical and Biological Engineering Korea UniversitySeoulRepublic of Korea Department of Nanomaterials Science and Engineering Korea University of Science and TechnologyDaejeonRepublic of Korea Advanced Analysis Center Korea Institute of Science and TechnologySeoulRepublic of Korea

To accelerate the discovery of materials through computations and experiments,a well-established protocol closely bridging these methods is *** introduce a high-throughput screening protocol for the discovery of bimetallic catalysts that replace palladium(Pd),where the similarities in the electronic density of states patterns were employed as a screening *** first-principles calculations,we screened 4350 bimetallic alloy structures and proposed eight candidates expected to have catalytic performance comparable to that of *** experiments demonstrate that four bimetallic catalysts indeed exhibit catalytic properties comparable to those of ***,we discover a bimetallic(Ni-Pt)catalyst that has not yet been reported for H_(2)O_(2) direct *** particular,Ni_(61)Pt_(39) outperforms the prototypical Pd catalyst for the chemical reaction and exhibits a 9.5-fold enhancement in cost-normalized *** protocol provides an opportunity for the catalyst discovery for the replacement or reduction in the use of the platinum-group metals.

关键词： synthesis catalyst bimetallic

Utilizing hybrid faradaic mechanism via catalytic and surface interactions for high-performance flexible energy storage system

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Journal of Energy Chemistry 2023年第8期83卷 541-548,I0013页

作者： Dong-Gyu Lee Hyeonggeun Choi Yeonsu Park min-cheol kim Jong Bae Park Suok Lee Younghyun Cho Wook Ahn A-Rang Jang Jung Inn Sohn John Hong Young-Woo Lee Department of Energy Engineering Soonchunhyang UniversityAsan 31538Republic of Korea Division of Physics and Semiconductor Science Dongguk University-SeoulSeoul 04620Republic of Korea Jeonju Centre Korea Basic Science InstituteJeonju 54907Republic of Korea Division of Electrical Electronic and Control EngineeringKongju National UniversityCheonan 31080Republic of Korea School of Materials Science and Engineering Kookmin UniversitySeoul 02707Republic of Korea

Improving the capacitance and energy density is a significant challenge while developing practical and flexible energy storage system(ESS).Redox mediators(RMs),as redox-active electrolyte additives,can provide additional energy storing capability via electrochemical faradaic contribution on electrodes for high-performance flexible ***,determining effective material combinations between electrodes and RMs is essential for maximizing surface faradaic redox reactions for energy-storage *** this study,an electrode-RM system comprising heterostructured hybrid(carbon fiber(CF)/MnO_(2)) faradaic electrodes and iodine RMs(I-RMs) in a redox-active electrolyte is *** CF/MnO_(2)with the 1-RMs(CF/MnO_(2)-I) induces dominant catalytic faradaic interaction with the I-RMs,significantly enhancing the surface faradaic kinetics and increasing the overall energy-storage *** CF/MnO_(2)-I ESSs show a 12.6-fold(or higher) increased volumetric energy density of 793.81 mWh L^(-1)at a current of 10 μA relative to ESSs using CF/MnO_(2)without I-RMs(CF/MnO_(2)).Moreover,the CF/MnO_(2)-I retains 93.1% of its initial capacitance after 10,000 cycles,validating the excellent ***,the flexibility of the ESSs is tested at different bending angles(180° to 0°),demonstrating its feasibility for flexible and high-wear ***,CF/MnO_(2)electrodes present a practical material combination for high-performance flexible energy-storage devices owing to the catalytic faradaic interaction with I-RMs.

关键词： Energy storage system Redox mediators Faradaic electrodes Catalytic interactions Mechanical stability

V_(2)O_(3)/VN electrocatalysts with coherent heterogeneous interfaces for selecting low-energy nitrogen reduction pathways

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SusMat 2024年第4期4卷 90-103页

作者： Tae-Yong An Chengkai Xia minyeong Je Hyunjung Lee Seulgi Ji min-cheol kim Subramani Surendran Mi-Kyung Han Jaehyoung Lim Dong-Kyu Lee Joon Young kim Tae-Hoon kim Heechae Choi Jung Kyu kim Uk Sim Hydrogen Energy Technology Laboratory Korea Institute of Energy Technology(KENTECH)NajuRepublic of Korea School of Chemical Engineering Sungkyunkwan University(SKKU)SuwonRepublic of Korea Materials&Chemistry Group Institute of Inorganic ChemistryUniversity of CologneCologneGermany Department of Polymer Engineering Graduate SchoolAlan G.MacDiarmid Energy Research Institute&School of Polymer Science and EngineeringChonnam National UniversityGwangjuRepublic of Korea Research Institute NEEL SciencesJeollanamdoRepublic of Korea Department of Materials Science and Engineering Chonnam National UniversityGwangjuRepublic of Korea Department of Chemistry Xi’an Jiaotong-Liverpool UniversitySuzhouChina

Electrochemical nitrogen reduction reaction(NRR)is a sustainable alterna-tive to the Haber-Bosch process for ammonia(NH3)***,the significant uphill energy in the multistep NRR pathway is a bottleneck for favorable serial *** overcome this challenge,we designed a vanadium oxide/nitride(V_(2)O_(3)/VN)hybrid electrocatalyst in which V_(2)O_(3)and VN coex-ist coherently at the heterogeneous *** single-phase V_(2)O_(3)and VN exhibit different surface catalytic kinetics for NRR,the V_(2)O_(3)/VN hybrid elec-trocatalyst can provide alternating reaction pathways,selecting a lower energy pathway for each material in the serial NRR *** a result,the ammo-nia yield of the V_(2)O_(3)/VN hybrid electrocatalyst was 219.6µg h^(-1)cm^(-2),and the Faradaic efficiency was 18.9%,which is much higher than that of single-phase VN,V_(2)O_(3),and VNxOy solid solution catalysts without *** functional theory calculations confirmed that the composition of these hybrid electrocatalysts allows NRR to proceed from a multistep reduction reaction to a low-energy reaction pathway through the migration and adsorption of interme-diate ***,the design of metal oxide/nitride hybrids with coherent heterointerfaces provides a novel strategy for synthesizing highly efficient elec-trochemical catalysts that induce steps favorable for the efficient low-energy progression of NRR.

关键词： coherent heterogeneous interfaces green ammonia synthesis hybrid electrocatalyst low-energy progression nitrogen reduction reaction(NRR) vanadium oxide/nitride(V_(2)O_(3)/VN)

Influence of Bed Temperature on Heat Shrinkage Shape Error in FDM Additive Manufacturing of the ABS-Engineering Plastic

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World Journal of Engineering and Technology 2016年第3期4卷 186-192页

作者： Young-Hyu Choi cheol-min kim Hwan-Seock Jeong Jeong-Ho Youn Department of Mechanical Engineering Changwon National University Changwon Republic of Korea Department of Mechanical Design Changwon National University Changwon Republic of Korea Turf Grass Science Institute Hanul Inc. Hapcheon-Gun Republic of Korea

In case of manufacturing hexahedral ABS (Acrylonitrile Butadiene Styrene) plastic components using a FDM (Fused Deposition Modeling)-based 3D printer, undesirable shape errors occur in the product due to heat shrinkage. This paper experimentally ob-served the influence of the bed temperature change on the deformed shape errors of a hexahedral specimen of 100 × 50 × 50 mm3 produced by using a 3D printer. During printing work, the head nozzle temperature was kept at 240?C and the head speed was set at 50 mm/s. The chamber was enclosed with a PC-plate. 3D printing was conducted at four different bed temperatures;50?C, 70?C, 90?C, and 110?C. After the produced specimens naturally cooled down to room temperature, their deformed shape errors were measured. As a result, the higher the bed temperature, the lower the deformed shape errors of the specimens were. However, if the bed temperature had exceeded 120?C, laminating adhesion became poor. That seems to occur because of the material phase change and can make 3D printing work very hard as a consequence. Results of this study can be helpful to set optimum bed temperature condition in FDM additive manufacturing.

关键词： FDM Additive Manufacturing 3D Printing Heat Shrinkage Shape Error ABS

Available Power Analysis for Background Tasks on Ubiquitous Sensor and Actuator Networks

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Available Power Analysis for Background Tasks on Ubiquitous ...

Essentials of thoracic outlet syndrome:A narrative review

The second International Conference of Electrical and Electronics Engineering(ICEEE 2011)

作者： Junghoon Lee cheol min kim Ho-Young Kwak Jikwang Han Dept.of Computer Science and Statistics Jeju National University Dept.of Computer Education Jeju National University Dept.of Computer Engineering Jeju National University

This paper first presents the sensor data processing framework integrating a power consumption scheduler for control actions, and then analyzes the available power for background tasks which are continuously performed using the remaining power. As the scheduler is designed to reduce the peak load for the given task set, it can make flatter the consumption level of dynamic tasks activated by the event detection. The experiment result obtained from the prototype implementation reveals that the proposed scheme can improve the minimum available power by up to 17.9 %, compared with the Earliest scheduling scheme, having a smaller standard deviation over the slots included in a scheduling window. Hence, our framework can achieve cost savings as the sensor network can purchase a smaller amount of energy from a utility company and can be built with lower power transmission capability.

关键词： smart grid power consumption control peak reduction background task available power

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World Journal of Clinical Cases 2021年第21期9卷 5804-5811页

作者： min cheol Chang Du Hwan kim Department of Rehabilitation Medicine College of MedicineYeungnam UniversityDaegu 42415South Korea Department of Physical Medicine and Rehabilitation College of MedicineChung-Ang UniversitySeoul 06973South Korea

Thoracic outlet syndrome(TOS)is a group of diverse disorders involving compression of the nerves and/or blood vessels in the thoracic outlet *** results in pain,numbness,paresthesia,and motor weakness in the affected upper *** reviewed the pathophysiology,clinical evaluation,differential diagnoses,and treatment of *** is usually classified into three types,neurogenic,venous,and arterial,according to the primarily affected *** true neurogenic and disputed TOS are considered neurogenic *** identifying the causative lesions is complex,detailed history taking and thorough clinical investigation are *** and imaging studies are helpful for excluding other possible disorders and confirming the diagnosis of true neurogenic *** existence of a disputed TOS remains *** physicians tend to be skeptical about the existence of disputed TOS,but thoracic surgeons argue that disputed TOS is *** who encounter patients with TOS need to understand its key features to avoid misdiagnosis and provide appropriate treatment.

关键词： Brachial plexus Diagnosis Review Thoracic outlet syndrome Treatment Neuromuscular lesions