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Electrochemical partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni via coupled oxidation of an interfacing NiAl intermetallic compound for robust hydrogen evolution

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Journal of Energy Chemistry 2023年第7期82卷 560-571,I0012页

作者： Young Hwa Yun Kwangsoo Kim Changsoo Lee Byeong-Seon An ji hee kwon Sechan Lee MinJoong Kim Jongsu Seo Jong Hyeok Park Byung-Hyun Kim Hyun-Seok Cho Hydrogen Research Department Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Computational Science&Engineering Laboratory Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Analysis Center for Energy Research Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea

Ni-based porous electrocatalysts have been widely used in the hydrogen evolution reaction(HER)in alkaline water electrolysis,and the catalysts are produced by selective leaching of Al from Ni-Al *** is well known that chemical leaching of Ni-Al intermetallic compound(IMC)generates a high surface area in Ni(OH)_(2).However,the Ni(OH)_(2) produced by leaching the Ni-Al intermetallic compound retards the hydrogen evolution reaction,which is attributed to its weak hydrogen adsorption *** this study,we controlled the chemical state of Ni using plasma vapor deposition(PVD)followed by heat treatment,selective Al leaching,and electrochemical reduction.X-ray diffraction(XRD),scanning microscopy(SEM),transmission electron microscopy(TEM),and energy-dispersive X-ray spectroscopy(EDS)were used to confirm the phase evolution of the electrocatalysts during *** reveal that the heat-treated Ni-Al alloy with a thick Ni2Al3surface layer underwent selective Al leaching and produced biphasic interfaces comprising Ni(OH)_(2) and NiAl IMCs at the edges of the grains in the outermost surface *** oxidation of the interfacing NiAl IMCs facilitated the partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni in the grains during electrochemical reduction,as confirmed by X-ray photoelectron spectroscopy(XPS).An electrocatalyst containing partially reduced Ni(OH)_(2)/Ni exhibited an overpotential of 54 mV at 10 mA/cm^(2) in a half-cell measurement,and a cell voltage of 1.675 V at 0.4 A/cm2for single-cell operation.A combined experimental and theoretical study(density functional theory calculations)revealed that the superior HER activity was attributed to the presence of partially reduced metallic Ni with various defects and residual Al,which facilitated water adsorption,dissociation,and finally hydrogen evolution.

关键词： Raney nickel HERChemical leaching Intrinsic activity Partial reduction

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Aligned Ion Conduction Pathway of Polyrotaxane‑Based Electrolyte with Dispersed Hydrophobic Chains for Solid‑State Lithium–Oxygen Batteries

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Nano-Micro Letters 2025年第2期17卷 169-186页

作者： Bitgaram Kim Myeong‑Chang Sung Gwang‑hee Lee Byoungjoon Hwang Sojung Seo ji‑Hun Seo Dong‑Wan Kim Department of Materials Science and Engineering Korea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea School of Civil Environmental and Architectural EngineeringKorea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea Materials Science and Chemical Engineering Center Institute for Advanced Engineering(IAE)Yongin 17180Republic of Korea

A critical challenge hindering the practical application of lithium–oxygen batteries(LOBs)is the inevitable problems associated with liquid electrolytes,such as evaporation and safety *** study addresses these problems by proposing a modified polyrotaxane(mPR)-based solid polymer electrolyte(SPE)design that simultaneously mitigates solvent-related problems and improves ***-SPE exhibits high ion conductivity(2.8×10^(−3)S cm^(−1)at 25℃)through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain *** this mPR-SPE into solid-state LOBs resulted in stable potentials over 300 *** situ Raman spectroscopy reveals the presence of an LiO_(2)intermediate alongside Li_(2)O_(2)during oxygen *** situ X-ray diffraction confirm the ability of the SPE to hinder the permeation of oxygen and moisture,as demonstrated by the air permeability *** present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs.

关键词： Solid polymer electrolyte Lithium-oxygen batteries Polyrotaxane ion conductivity Hydrophobic chain

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Fabrication of 3D Printed PCL/PEG Polyblend Scaffold Using Rapid Prototyping System for Bone Tissue Engineering Application

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Journal of Bionic Engineering 2018年第3期15卷 435-442页

作者： Su A Park Sang jin Lee ji Min Seok Jun hee Lee Wan Doo Kim Il Keun kwon Department of Nature-Inspired Nanoconvergence Systems Korea Institute of Machinery and Materials 156 Gajeongbuk-ro Yuseong-gu Daejeon 34103 Republic of Korea Department of Dental Materials School of Dentistry Kyung Hee University 26 Kyungheedae-ro Dongdaemun-gu Seou102447 Republic of Korea

Three-dimensional （3D） printing is a novel process used to manufacture bone tissue engineered scaffolds. This process allows for easy control of the architecture at the micro structure. However, the scaffold properties are typically limited in terms of cellular activity at the scaffold surface due to the printed materials properties. In this study, we developed a polycaprolactone （PCL） blended with polyethylene glycol （PEG） 3D printed scaffold using a rapid prototyping system. The manufactured scaffolds were then washed out to form small pores on the surface in order to improve the scaffolds hydrophilicity. We analyzed the resultant material by using Scanning Electron Microscopy （SEM）, water absorption, water contact angle, in vitro WST-1, and the Bradford assay. Additionally, cells incubated on the fabricated scaffolds were visualized by Confocal Laser Scanning Microscopy （CLSM）. The developed scaffolds exhibited small pores on the strand surface which served to increase hydrophilicity as well as improve cellular proliferation and increase total protein content. Our findings suggest that the presence of small pores on the scaffolds can be used as an effective tool for improving implant cellular interaction. This research indicates that these modified scaffolds can be considered useful for bone tissue engineering applications to improve human health.

关键词： polycaprolactone polyethylene glycol polyblend 3D printing porosity bone tissue engineering

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New Spam Filtering Method with Hadoop Tuning-Based MapReduce Naïve Bayes

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Computer Systems Science & Engineering 2023年第4期45卷 201-214页

作者： Keungyeup ji Youngmi kwon Department of Radio and Information Communications Engineering Chungnam National UniversityDaejeon34134Korea

As the importance of email increases,the amount of malicious email is also increasing,so the need for malicious email filtering is *** it is more economical to combine commodity hardware consisting of a medium server or PC with a virtual environment to use as a single server resource and filter malicious email using machine learning techniques,we used a Hadoop MapReduce framework and Naïve Bayes among machine learning methods for malicious email ***ïve Bayes was selected because it is one of the top machine learning methods(Support Vector Machine(SVM),Naïve Bayes,K-Nearest Neighbor(KNN),and Decision Tree)in terms of execution time and *** email was filtered with MapReduce programming using the Naïve Bayes technique,which is a supervised machine learning method,in a Hadoop framework with optimized performance and also with the Python program technique with the Naïve Bayes technique applied in a bare metal server environment with the Hadoop environment not *** to the results of a comparison of the accuracy and predictive error rates of the two methods,the Hadoop MapReduce Naïve Bayes method improved the accuracy of spam and ham email identification 1.11 times and the prediction error rate 14.13 times compared to the non-Hadoop Python Naïve Bayes method.

关键词： Hadoop hadoop distributed file system(HDFS) MapReduce configuration parameter malicious email filtering Naïve Bayes

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Graphical interface for motion editing using procedure visualization

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Science China(Information Sciences) 2011年第6期54卷 1227-1237页

作者： kwon ji-Yong LEE In-kwon Department of Computer Science Yonsei University

In this paper, we introduce an interface for motion editing that visualizes editing procedures. For intuitive understanding and construction of motion editing procedures, our system represents an editing element that produces modified motion from a given input motion as a graphical node, and enables user to construct a whole motion editing procedure by connecting the nodes with a few mouse interactions. The system provides both the 3D transform manipulator and the time-line slider for intuitive controlling of the parameters of each node. The user evaluation results show that our system is easy and intuitive to be used by users for editing of motion sequences.

关键词： motion editing procedural visualization graphical development environment animation system character animation

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On the Classification of Positive Quaternionic Khler Manifolds with b_4=1

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Acta Mathematica Sinica,English Series 2010年第5期26卷 875-884页

作者： jin Hong KIM hee kwon LEE Department of Mathematical Sciences Korea Advanced Institute of Science and Technology Guseong-dong

Let M be a positive quaternionic Kahler manifold of dimension 4m. We already showed that if the symmetry rank is greater than or equal to [m/2] ＋ 2 and the fourth Betti number b4 is equal to one, then M is isometric to HPm. The goal of this paper is to report that we can improve the lower bound of the symmetry rank by one for higher even-dimensional positive quaternionic Kahler manifolds. Namely, it is shown in this paper that if the symmetry rank of M with b4（M） = 1 is greater than or equal to m/2 ＋ 1 for m ≥ 10, then M is isometric to HPm. One of the main strategies of this paper is to apply a more delicate argument of Frankel type to positive quaternionic Kahler manifolds with certain symmetry rank.

关键词： positive quaternionic Kahler symmetry

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Influence of the preparation method on the catalytic activity of Mg-Al hydrotalcites as solid base catalysts

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Green Energy & Environment 2019年第3期4卷 287-292页

作者： Sungjae Park Dahye kwon ji Yeon Kang ji Chul Jung Department of Chemical Engineering Myongji University

Mg-Al hydrotalcites were synthesized using different preparation methods(a co-precipitation method, a urea method, and a simple one) to analyze their effect on the catalytic activity of these solid base catalysts. The method strongly affected the structure of their layers(e.g., the growth and stacking of the layers, and the type of intercalated anions) and, accordingly, their catalytic activity. The Mg-Al hydrotalcite prepared by co-precipitation showed the best catalytic performance in the isomerization of glucose into fructose, due to the small crystallite size and sand rose morphology enhancing the exposure of surface active sites to reactants.

关键词： Mg-Al hydrotalcite Preparation method Base catalyst Glucose isomerization Fructose

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Tuning the base properties of Mg–Al hydrotalcite catalysts using their memory effect

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Journal of Energy Chemistry 2020年第7期29卷 229-236,I0008页

作者： Dahye kwon ji Yeon Kang Suna An Inchan Yang ji Chul Jung Department of Chemical Engineering Myongji UniversityYongin 17058Republic of Korea

Herein,the relationship between the structure and base properties of Mg–Al hydrotalcite catalysts was comprehensively investigated in relation to heat treatment and rehydration processes,which are well known as memory effects of *** structure of Mg–Al hydrotalcites changed from layered double hydroxide(LDH)to mixed metal oxide and subsequently to a spinel structure during heat treatment,and it was returned from mixed metal oxide to a LDH structure by *** on various characterizations,we successfully proposed a detailed mechanism of memory *** also confirmed that the Mg–Al hydrotalcites had weak or strong base sites and that their base properties could be systematically tuned by heat treatment and *** prepared Mg–Al hydrotalcites were applied to a model reaction,isomerization of glucose to fructose,as base *** the catalysts tested,the rehydrated Mg–Al hydrotalcite efficiently produced fructose due to its appropriate base and structure *** finally concluded that the base sites of Mg–Al hydrotalcites can be designed as desired by heat treatment and ***,through systematic design of the base sites of Mg–Al hydrotalcites,these can be promising catalysts for various heterogeneous reactions over base catalysts,giving excellent catalytic performances.

关键词： Mg–Al hydrotalcite Structure Base properties Heat treatment Rehydration

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Amine axial ligand-coordinated cobalt phthalocyanine-based catalyst for flow-type membraneless hydrogen peroxide fuel cell or enzymatic biofuel cell

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Journal of Energy Chemistry 2021年第7期30卷 463-471页

作者： heeyeon An Hyewon Jeon Jungyeon ji Yongchai kwon Yongjin Chung Department of Chemical and Biological Engineering Korea National University of Transportation50 Daehak-roChungjuChungbuk 27469Republic of Korea Graduate School of Energy and Environment Seoul National University of Science and Technology 232 Gongneung-roNowon-guSeoul 01811Republic of Korea Department of Chemical and Biomolecular Engineering Seoul National University of Science and Technology232 Gongneung-roNowon-guSeoul 01811Republic of Korea Department of ITÁEnergy Convergence(BK21 FOUR) Korea National University of Transportation50 Daehak-roChungjuChungbuk 27469Republic of Korea

In this study,an amine-coordinated cobalt phthalocyanine(CoPc)-based anodic catalyst was fabricated by a facile process,to enhance the performance of hydrogen peroxide fuel cells(HPFCs) and enzymatic biofuel cells(EBCs).For this purpose,polyethyleneimine(PEI) was added onto the reduced graphene oxide and CoPc composite(RGO/CoPc) to create abundant NH2 axial ligand groups,for anchoring the Co core within the *** to the PEI addition,the onset potential of the hydrogen peroxide oxidation reaction was shifted by 0.13 V in the negative direction(0.02 V) and the current density was improved by 1.92 times(1.297 mA cm^(-2)),compared to those for RGO/CoPc(0.15 V and 0.676 mA cm^(-2),respectively),due to the formation of donor-acceptor dyads and the prevention of CoPc from leaching *** biocatalyst using glucose oxidase(GOx)([RGO/CoPc]/PEI/GOx) showed a better onset potential and catalytic activity(0.15 V and 318.7 μA cm^(-2)) than comparable structures,as well as significantly improved operational durability and long-term *** is also attributed to PEI,which created a favorable microenvironment for the *** maximum power densities(MPDs) and open-circuit voltages(OCVs) obtained for HPFCs and EBCs using the suggested catalyst were 105.2±1.3 μW cm^(-2)(0.317±0.003 V) and 25.4±0.9 μW cm^(-2)(0.283±0.007 V),*** shows that the amine axial ligand effectively improves the performance of the actual driving HPFCs and EBCs.

关键词： Hydrogen peroxide fuel cell Enzymatic biofuel cell Amine axial ligand Hydrogen peroxide oxidation reaction Membraneless

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Thermal deformation of aluminum alloy casting materials for tire mold by numerical analysis

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中国有色金属学会会刊：英文版 2012年第S3期22卷 859-863页

作者： hee-Sung YOON Je-Se CHOI Yool-kwon OH Department of Advanced Parts and Materials Engineering Chosun University Department of Mechatronics Engineering Chosun University

Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically *** AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial *** temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature *** thermal deformation was closely related to the temperature difference between the surface and inside of the *** numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting ***,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.

关键词： thermal deformation finite element analysis AC7A casting material AC4C casting material

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