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Frontiers of Structural and Civil Engineering 2022年第4期16卷 506-514页

作者： Jinyoung YOON byoung il choi Jae Hong KIM Department of Structural Engineering Research Korea Institute of Civil Engineering and Building Technology(KICT)Goyang 10223Republic of Korea System Safety Research Department Korea Shipbuilding and Offshore EngineeringSeongnam 13591Republic of Korea Department of Civil and Environmental Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea

The cement dispersion performance of a polycarboxylate(PCE)-based superplasticizer is highly related to their adsorption behaviors as a function of *** study evaluated effects of PCEs on rheological properties of cementitious ***,characteristics of PCEs were characterized via permeation chromatography(GPC)and Fourier-transform infrared spectrometry(FT-IR).The adsorption behavior of single and blended PCEs on cementitious composites was identified using total organic carbon analyzer(TOC).Based on the measurement of PCE adsorption,the changes of rheological properties of cementitious materials as well as the number of dispersed cement particles were characterized using a rheometer and laser spectroscopy,*** experimental results support the systematic mechanism of PCE adsorption,cement dispersion,and the decrease in viscosity of cementitious materials.

关键词： adsorption polycarboxylate superplasticizer rheology dispersion

Correlation between hydration properties and electrochemical performances on Ln cation size effect in layered perovskite for protonic ceramic fuel cells

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Journal of Energy Chemistry 2024年第1期88卷 1-9,I0001页

作者： Inhyeok Cho Jiwon Yun Boseok Seong Junseok Kim Sun Hee choi Ho-il Ji Sihyuk choi Department of Mechanical Engineering Kumoh National Institute of TechnologyGumi 39177GyeongbukRepublic of Korea Department of Aeronautics Mechanical and Electronic Convergence EngineeringKumoh National Institute of TechnologyGumi 39177GyeongbukRepublic of Korea Center for Energy Materials Research Korea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Center for Hydrogen and Fuel Cell Research Clean Technology Research DivisionKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Department of Energy and Environmental Engineering University of Science and TechnologySeoul 02792Republic of Korea Nanomaterials Science and Engineering Korea University of Science and Technology(UST)KIST CampusSeoul 02792Republic of Korea

PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.

关键词： Protonic ceramic fuel cell Cathode Triple ionic and electronic conductor Hydration property Proton uptake Gibbs free energy

Tailoring local structures of atomically dispersed copper sites for highly selective CO_(2) electroreduction

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Carbon Energy 2024年第4期6卷 79-90页

作者： Kyung‐Jong Noh byoung Joon Park Ying Wang Yejung choi Sang‐Hoon You Yong‐Tae Kim Kug‐Seung Lee Jeong Woo Han Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Pohang Accelerator Laboratory(PAL) Beamline DivisionPohangGyeongbukRepublic of Korea

Atomically‐dispersed copper sites coordinated with nitrogen‐doped carbon(Cu–N–C)can provide novel possibilities to enable highly selective and active electrochemical CO_(2) reduction ***,the construction of optimal local electronic structures for nitrogen‐coordinated Cu sites(Cu–N_(4))on carbon remains ***,we synthesized the Cu–N–C catalysts with atomically‐dispersed edge‐hosted Cu–N_(4) sites(Cu–N_(4)C_(8))located in a micropore between two graphitic sheets via a facile method to control the concentration of metal ***‐hosted Cu–N_(4)C_(8) catalysts outperformed the previously reported M–N–C catalysts for CO_(2)‐to‐CO conversion,achieving a maximum CO Faradaic efficiency(FECO)of 96%,a CO current density of–8.97 mA cm^(–2) at–0.8 V versus reversible hydrogen electrode(RHE),and over FECO of 90%from–0.6 to–1.0 V versus *** studies revealed that the micropore of the graphitic layer in edge‐hosted Cu–N_(4)C_(8) sites causes the d‐orbital energy level of the Cu atom to shift upward,which in return decreases the occupancy of antibonding states in the*COOH *** research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions.

关键词： atomic local structure density functional theory electrochemical CO_(2)reduction metal nitrogen‐doped carbon single‐atom catalyst

Artificial optoelectronic synapse based on spatiotemporal irradiation to source-sharing circuitry of synaptic phototransistors

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InfoMat 2024年第2期6卷 131-141页

作者： Seungho Song Changsoon choi Jongtae Ahn Je-Jun Lee Jisu Jang byoung-Soo Yu Jung Pyo Hong Yong-Sang Ryu Yong-Hoon Kim Do Kyung Hwang Center for Opto-Electronic Materials and Devices Post-Silicon Semiconductor InstituteKorea Institute of Science and Technology(KIST)SeoulRepublic of Korea School of Advanced Materials Science and Engineering Sungkyunkwan UniversitySuwonRepublic of Korea Center for Spintronics Post-Silicon Semiconductor InstituteKorea Institute of Science and Technology(KIST)SeoulRepublic of Korea Division of Nanoscience&Technology KIST SchoolUniversity of Science and Technology(UST)SeoulRepublic of Korea School of Biomedical Engineering Korea UniversitySeoulRepublic of Korea KU-KIST Graduate School of Converging Science and Technology Korea UniversitySeoulRepublic of Korea

To overcome the intrinsic inefficiency of the von Neumann architecture,neuromorphic devices that perform analog vector–matrix multiplication have been highlighted for achieving power-and time-efficient data *** particular,artificial synapses,of which conductance should be programmed to represent the synaptic weights of the artificial neural network,have been intensively researched to realize neuromorphic ***,inspired by excitatory and inhibitory synapses,we develop an artificial optoelectronic synapse that shows both potentiation and depression characteristics triggered only by optical *** design of the artificial optoelectronic synapse,in which excitatory and inhibitory synaptic phototransistors are serially connected,enables these characteristics by spatiotemporally irradiating the phototransistor channels with optical ***,a negative synaptic weight can be realized without the need for electronic components such as *** such attributes,the artificial optoelectronic synapse is demonstrated to classify three digits with a high recognition rate(98.3%)and perform image preprocessing via analog vector-matrix multiplication.

关键词： amorphous oxide semiconductor analog processing artificial synapse neuromorphic optoelectronics

Development of vehicle-recognition method on water surfaces using LiDAR data:SPD^(2)(spherically stratified point projection with diameter and distance)

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Defence Technology（防务技术） 2024年第6期36卷 95-104页

作者： Eon-ho Lee Hyeon Jun Jeon Jinwoo choi Hyun-Taek choi Sejin Lee The Department of Mechanical Engineering Kongju National University1223-24 Cheonan-daeroCheonan 31080Republic of Korea Ocean System Engineering Research Division Korea Research Institute of Ships and Ocean Engineering(KRISO)Daejeon 34103Republic of Korea The Division of Mechanical&Automotive Engineering Kongju National University1223-24 Cheonan-daeroCheonan 31080Republic of Korea

Swarm robot systems are an important application of autonomous unmanned surface vehicles on water *** monitoring natural environments and conducting security activities within a certain range using a surface vehicle,the swarm robot system is more efficient than the operation of a single object as the former can reduce cost and save *** is necessary to detect adjacent surface obstacles robustly to operate a cluster of unmanned surface *** this purpose,a LiDAR(light detection and ranging)sensor is used as it can simultaneously obtain 3D information for all directions,relatively robustly and accurately,irrespective of the surrounding environmental *** the GPS(global-positioning-system)error range exists,obtaining measurements of the surface-vessel position can still ensure stability during platoon *** this study,a three-layer convolutional neural network is applied to classify types of surface *** aim of this approach is to redefine the sparse 3D point cloud data as 2D image data with a connotative meaning and subsequently utilize this transformed data for object classification ***,we have proposed a descriptor that converts the 3D point cloud data into 2D image *** use this descriptor effectively,it is necessary to perform a clustering operation that separates the point clouds for each *** developed voxel-based clustering for the point cloud ***,using the descriptor,3D point cloud data can be converted into a 2D feature image,and the converted 2D image is provided as an input value to the *** intend to verify the validity of the proposed 3D point cloud feature descriptor by using experimental data in the ***,we explore the feasibility of real-time object classification within this framework.

关键词： Object classification Clustering 3D point cloud data LiDAR(light detection and ranging) Surface vehicle

Synthetic brochosomes:Design,synthesis,and applications

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Nano Research 2024年第2期17卷 734-742页

作者： Lin Wang Jinsol choi Tak-Sing Wong Department of Mechanical Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA Materials Research Institute The Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Biomedical Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA

Brochosomes,which are nanoscopic buckyball-shaped granules produced by leafhoppers,are one of the most intricate structures discovered in *** functions of brochosomes have been proposed but only a few have been experimentally validated due to the challenge of fabricating their synthetic *** in micro-and nanofabrication have recently led to the emergence of synthetic brochosomes,opening up new possibilities for innovative *** review explores the early discovery of natural brochosomes and their geometrical features,followed by the recent progress in fabricating synthetic brochosomes and their *** on future applications and challenges in the scalable manufacturing of synthetic brochosomes are discussed.

关键词： synthetic brochosomes leafhopper antireflection superhydrophobicity surface-enhanced Raman scattering photocatalyst energy harvesting

Rapid monitoring of indoor airborne influenza and coronavirus with high air flowrate electrostatic sampling and PCR analysis

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Frontiers of Environmental Science & Engineering 2024年第7期18卷 73-85页

作者： Sanggwon An Sangsoo choi Hyeong Rae Kim Jungho Hwang School of Mechanical Engineering Yonsei UniversitySeoul 02876Republic of Korea Gas Metrology Group Korea Research Institute of Standards and Science(KRISS)Daejeon 34113Republic of Korea

The World Health Organization has raised concerns about the possibility of airborne transmission in enclosed and poorly ventilated ***,rapid monitoring of airborne viruses is necessary in multi-use facilities with dense ***,an electrostatic air sampler(250 L/min)was developed in this work to obtain indoor viral aerosol samples for analysis via the Polymerase Chain Reaction(PCR).Aerosol tests with H1N1 and HCoV-229E were performed to evaluate the sample collection *** analysis,along with another aerosol test,was conducted to evaluate the recovery of the virus particles collected by the *** laboratory tests,our electrostatic sampler obtained viral samples that were detectable by PCR under the simulated viral pandemic scenario(3000 RNA copies per cubic meter of air)within 40 *** resulting cycle threshold(C)values were 35.07 and 37.1 for H1N1 and HCoV-229E,*** the performance evaluation in the laboratory,field tests were conducted in a university classroom from October 28 to December 2,*** A and HCoV-229E were detected in two air samples,and the corresponding C,values were 35.3 and *** PCR results are similar to those obtained from laboratory tests,considering the simulatedviralpandemic scenario.

关键词： Airborne virus Electrostatic sampler Rapid monitoring Indoor environment Field test

Enhancing BiVO_(4)photoanode performance by insertion of an epitaxial BiFeO_(3)ferroelectric layer

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Journal of Energy Chemistry 2024年第2期89卷 71-78,I0003页

作者： Haejin Jang Yejoon Kim Hojoong choi Jiwoong Yang Yoonsung Jung Sungkyun choi Donghyeon Lee Ho Won Jang Sanghan Lee School of Materials Science and Engineering Gwangju Institute of Science and TechnologyGwangju 61005Republic of Korea Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea

BiVO_(4)(BVO)is a promising material as the photoanode for use in photoelectrochemical ***,the high charge recombination and slow charge transfer of the BVO have been obstacles to achieving satisfactory photoelectrochemical *** address this,various modifications have been attempted,including the use of ferroelectric *** materials can form a permanent polarization within the layer,enhancing the separation and transport of photo-excited electron-hole *** this study,we propose a novel approach by depositing an epitaxial BiFeO_(3)(BFO)thin film underneath the BVO thin film(BVO/BFO)to harness the ferroelectric property of *** self-polarization of the inserted BFO thin film simultaneously functions as a buffer layer to enhance charge transport and a hole-blocking layer to reduce charge *** a result,the BVO/BFO photoanodes showed more than 3.5 times higher photocurrent density(0.65 mA cm^(-2))at 1.23 V_(RHE)under the illumination compared to the bare BVO photoanodes(0.18 m A cm^(-2)),which is consistent with the increase of the applied bias photon-to-current conversion efficiencies(ABPE)and the result of electrochemical impedance spectroscopy(EIS)*** results can be attributed to the self-polarization exhibited by the inserted BFO thin film,which promoted the charge separation and transfer efficiency of the BVO photoanodes.

关键词： Photoelectrochemical Photoanode BiVO_(4) Ferroelectric materials BiFeO_(3)

Learning feature alignment and dual correlation for few‐shot image classification

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CAAI Transactions on Intelligence Technology 2024年第2期9卷 303-318页

作者： Xilang Huang Seon Han choi Department of Electronic and Electrical Engineering Ewha Womans UniversitySeoulSouth Korea Graduate Program in Smart Factory Ewha Womans UniversitySeoulSouth Korea

Few‐shot image classification is the task of classifying novel classes using extremely limited labelled *** perform classification using the limited samples,one solution is to learn the feature alignment(FA)information between the labelled and unlabelled sample *** FA methods use the feature mean as the class prototype and calculate the correlation between prototype and unlabelled features to learn an alignment ***,mean prototypes tend to degenerate informative features because spatial features at the same position may not be equally important for the final classification,leading to inaccurate correlation ***,the authors propose an effective intraclass FA strategy that aggregates semantically similar spatial features from an adaptive reference prototype in low‐dimensional feature space to obtain an informative prototype feature map for precise correlation ***,a dual correlation module to learn the hard and soft correlations was developed by the *** module combines the correlation information between the prototype and unlabelled features in both the original and learnable feature spaces,aiming to produce a comprehensive cross‐correlation between the prototypes and unlabelled *** both FA and cross‐attention modules,our model can maintain informative class features and capture important shared features for *** results on three few‐shot classification benchmarks show that the proposed method outperformed related methods and resulted in a 3%performance boost in the 1‐shot setting by inserting the proposed module into the related methods.

关键词： image classification machine learning metric learning

Modeling asymmetric fracture mechanics of Mg alloy wire in drawing process

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Journal of Magnesium and Alloys 2024年第5期12卷 2057-2069页

作者： Sunghoon choi Jongwon Shin Joung Sik Suh Dongchoul Kim Department of Mechanical Engineering Sogang UniversitySeoul04107Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

In this study,a numerical analysis was conducted on the ductile fracture of a 2-mm diameter Mg-1Zn-0.5Mn-0.5Sr-0.1Ca alloy wire during *** hexagonally close-packed crystal structure of Mg alloys causes asymmetric fracture behavior,especially in the compression *** aim of this study is to develop a comprehensive damage model for Mg alloy wire that accurately predicts ductile fracture,with a focus on the compression region.A novel experimental method was introduced to measure the ductile fracture of Mg alloy wires under different stress *** wire drawing process was simulated using the Generalized Incremental Stress-State dependent damage(GISSMO)Model and the Semi-Analytical Model for Polymers(SAMP)*** damage model's prediction and the experimental results were found to be in excellent agreement,especially in determining crack *** analysis established a safe zone diagram for die angle and reduction ratio,and experimental validation confirmed the feasibility of this *** proposed damage model can provide a practical and reliable analysis for optimizing the drawing process of Mg alloy wire.

关键词： Mg alloy Wire drawing Finite element method Damage model Safe zone diagram