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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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Evolution of microstructure and tensile properties of cold-drawn hyper-eutectoid steel wires during post-deformation annealing

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Journal of Materials Science & Technology 2020年第6期41卷 1-11页

作者： Majid Jafari Chan-Woo Bang Jong-Chan Han Kyeong-Min Kim seon-Hyeong Na Chan-Gyung Park byeong-Joo Lee Department of Materials Science and Engineering POSTECH Pohang 37673 South Korea

Manufacturing temperatures of severely cold-drawn hyper-eutectoid steel wires are sufficiently high to influence the mobility of dislocations and alloy elements,thereby affecting the materials’mechanical ***,we describe the evolution of microstructure and tensile strength of the as-drawn 3.45 GPa steel wire during post-deformation annealing for 30 min at 150-450℃.Annealing at 150℃raised the strength to 3.77 GPa by age-hardening through activation of dislocations pinning by carbon,while further temperature rising up to 450℃caused a severe loss of *** was proved that annealing at 300 and 450℃destabilizes the lamellar microstructure,promoting the formation of carbon-deficient(Fe,Mn,Cr)3 C-type cementite particles with preferentially rounded and partially faceted *** at 450℃yielded the accumulation of Mn and Cr at the ferrite/particle interfaces,and their concentrations at the interfaces were dependent on the interface structure;i.e.,lower concentrations at rounded interfaces(formed through capillarity–driven coarsening of the spheroidized cementite),and higher concentrations at faceted interfaces(that are initially existing in the as-drawn state).Our proof-of-principle observations,supported by thermodynamic calculations and kinetic assessments,provide a pathway for understanding the changes in microstructural and tensile properties during manufacturing of the hyper-eutectoid steel wires.

关键词： Three-dimensional atom probe(3DAP) High resolution transmission electron microscopy(HRTEM) Nano-grained low-carbon steel Annealing Tensile behavior

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Plasma Wall Potentials with Secondary Electron Emissions up to the Stable Space-Charge-Limited Condition

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Plasma Science and Technology 2013年第11期15卷 1093-1099页

作者： Jongho seon Ensang LEE School of Space Research Kyung Hee University Seocheon-dong Giheung-gu Yongin-si

Numerical solutions to floating plasma potentials for walls emitting secondary elec- trons are obtained for various surface materials. The calculations are made with plasma moment equations and the secondary electron emission coefficients, which were determined from recent laboratory experiments. The results estimate the wall potentials up to the physical conditions that allow stable plasma sheaths under the space-charge-limited condition. The materials often used in the laboratory, such as aluminum, silicon, boron, molybdenum, silicon dioxide, and alumina, are considered. The minimum wall potential before the onset of space-charge-limited emission is determined by the electron temperatures at which the effective secondary electron emission coefficient integrated over the velocity distributions is about 0.62. The corresponding potential is given by -eφ0 ,- 1.87kBT. The condition for space-charge-limited emission is newly found by numerically searching for all the stable sheaths. The new condition is -eφ0 - 0.95kBT, and this predicts a wall potential that is less negative than the previously found one. Calculation of the power dissipated to the wall for hydrogen plasmas shows that there is a large difference in terms of power dissipation among the considered materials in the temperature range 20-50 eV.

关键词： secondary electrons plasma sheath wall potential space-charge-limited emission

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A novel heterodimeric cytokine consisting of IL-17 and IL-17F regulates inflammatory responses

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Cell Research 2007年第5期17卷 435-440页

作者： seon Hee Chang Unit 906 Houston USA TX 77030 7455 Fannin Department of Immunology MD Anderson Cancer Center

CD4+ helper T (TH) cells play crucial roles in immune responses. Recently a novel subset of TH cells, termed TH,TH17 or inflammatory TH (THi), has been identified as critical mediators of tissue inflammation. These cells produceIL-17 (also called IL-17 A) and IL-17F, two most homologous cytokines sharing similar regulations. Here we reportthat when overexpressed in 293T cells, IL-17 and IL-17F form not only homodimers but also heterodimers, which wename as IL-17A/F. Fully differentiated mouse THi cells also naturally secrete IL-17A/F as well as IL-17 and IL-17Fhomodimeric cytokines. Recombinant IL-17A/F protein exhibits intermediate levels of potency in inducing IL-6 andKC (CXCL1) as compared to homodimeric cytokines. IL-17A/F regulation of IL-6 and KC expression is dependent onIL-17RA and TRAF6. Thus, IL-17A/F cytokine represents another mechanism whereby T cells regulate inflammatoryresponses and may serve as a novel target for treating various immune-mediated diseases.

关键词： inflammation IL-17 T cells

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EXPLICIT BOUNDS OF EIGENVALUES FOR STIFFNESS MATRICES BY QUADRATIC HIERARCHICAL BASIS METHOD)

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Journal of Computational Mathematics 2003年第2期21卷 113-124页

作者： Sang Dong KIM byeong Chun SHIN Department of Mathematics Kyungpook National UniversityTaegu 702-701KoreaDepartment of MathematicsChonnam National UniversityGwangju 500-757Korea

The bounds for the eigenvalues of the stiffness matrices in the finite element discretization corresponding to Lu := - u' with zero boundary conditions by quadratic hierarchical basis are shown explicitly. The condition number of the resulting system behaves like O(1/h) where h is the mesh size. We also analyze a main diagonal preconditioner of the stiffness matrix which reduces the condition number of the preconditioned system to O(1).

关键词： hierarchical basis multilevel

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Hydrodynamics and modeling of a ventilated supercavitating body in transition phase

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Journal of Hydrodynamics 2015年第5期27卷 763-772页

作者： KIM seon-Hong KIM Nakwan Department of Naval Architecture and Ocean Engineering Seoul National University

Compared to other underwater vehicles, supercavitating vehicles can attain a high speed because they eliminate drag by creating a large cavity, thus establishing the so-called ＂supercavitating condition.＂ Such a cavity is difficult to develop under normal conditions, hence, ventilation is used to attain the supercavitating condition in the initial phase of flight. In this paper, we focus on the hydrodynamic characteristics of a ventilated supercavitating vehicle. First, dynamic modeling of the supercavitating vehicle is performed to calculate the hydrodynamic force/moment acting on the vehicle for a given size of cavity. We then define the relationship between the ventilation rate and the cavitation number based on an air entrainment model of the ventilated cavity. Numerical simulations were performed to analyze the physical feasibility and characteristics of the modeling. The results show that the cavity length/radius increases with the ventilation rate, proving that ventilation can be used to attain the supercavitating condition.

关键词： entilated supercavity hydrodynamical modeling supercavitating body transition phase cavity closure mode dynamics modeling

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CHEBYSHEV WEIGHTED NORM LEAST-SQUARES SPECTRAL METHODS FOR THE ELLIPTIC PROBLEM

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Journal of Computational Mathematics 2006年第4期24卷 451-462页

作者： Sang Dong Kim byeong Chun Shin Department of Mathematics Kyungpook National University Taegu 702-701 Korea Department of Mathematics Chonnam National University Kwangju 500-757 Korea

We develop and analyze a first-order system least-squares spectral method for the second-order elhptic boundary value problem with variable coefficients. We first analyze the Chebyshev weighted norm least-squares functional defined by the sum of the Lw^2- and Hw^-1- norm of the residual equations and then we eplace the negative norm by the discrete negative norm and analyze the discrete Chebyshev weighted least-squares method. The spectral convergence is derived for the proposed method. We also present various numerical experiments. The Legendre weighted least-squares method can be easily developed by following this paper.

关键词： Least-squares methods Spectral method Negative norm.

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Quality of Service Improvement with Optimal Software-Defined Networking Controller and Control Plane Clustering

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Computers, Materials & Continua 2021年第4期67卷 849-875页

作者： Jehad Ali byeong-hee Roh Department of Computer Engineering and Department of AI Convergence Network Suwon16499Korea

The controller is indispensable in software-defined networking(SDN).With several features,controllers monitor the network and respond promptly to dynamic *** performance affects the quality-of-service(QoS)in *** controller supports a set of ***,the support of the features may be more prominent in one ***,a single controller leads to performance,single-point-of-failure(SPOF),and scalability *** overcome this,a controller with an optimum feature set must be available for ***,a cluster of optimum feature set controllers will overcome an SPOF and improve the QoS in ***,leveraging an analytical network process(ANP),we rank SDN controllers regarding their supporting features and create a hierarchical control plane based cluster(HCPC)of the highly ranked controller computed using the ANP,evaluating their performance for the OS3E *** results demonstrated in Mininet reveal that a HCPC environment with an optimum controller achieves an improved ***,the experimental results validated in Mininet show that our proposed approach surpasses the existing distributed controller clustering(DCC)schemes in terms of several performance metrics i.e.,delay,jitter,throughput,load balancing,scalability and CPU(central processing unit)utilization.

关键词： Quality-of-service software-defined networking controller hierarchical control plane clustering scalability

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Comparison of soil bacterial diversity and community composition between clear-cut logging and control sites in a temperate deciduous broad-leaved forest in Mt. Sambong, South Korea

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Journal of Forestry Research 2020年第6期31卷 2367-2375页

作者： byeong-Ju Lee Soo Hyung Eo Department of Forest Resources Kongju National UniversityYesanChungnam 32439Republic of Korea

Deforestation or clear-cut logging affects forest ecosystems,including soil microbial *** purpose of this study was to investigate the effects of clearcut logging on the soil bacterial community in a temperate deciduous broad-leaved forest on ***,South *** investigated the physicochemical characteristics and bacterial diversity of the soil in clear-cut logging and control *** available phosphorus(AP)level in soil was significantly lower in the clear-cut sites than in the control;however,the other physicochemical properties of soil were similar at the two *** examining the bacterial 16S rRNA gene using next-generation sequencing,we found that the number of bacterial taxa at the species and phylum level were similar at the control and clear-cut *** with the high resilience of bacterial communities and absence of change in the soil physicochemical properties—with the exception of AP—we found similar levels of bacterial diversity at the two *** most taxa showed similar composition ratios at the control and the clear-cut sites,some taxa such as Deltaproteobacteria,Ktedonobacteriales,Myxocccales,Polyangiaceae,Pedosphaera_f,and Solibacter showed differences after clear-cut *** conclude that AP was significantly associated with those bacterial taxa that showed differences in their composition ratios following clear-cut logging.

关键词： Forest soil Metagenomics Pyrosequencing Soil physicochemical characteristics

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Metabolomic and transcriptomic study to understand changes in metabolic and immune responses in steers under heat stress

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Animal Nutrition 2022年第4期11卷 87-101页

作者： Jun Sik Eom Da Som Park Sang Jin Lee Bon-Hee Gu Shin Ja Lee Sang-Suk Lee seon-Ho Kim byeong-Woo Kim Sung Sill Lee Myunghoo Kim Institute of Agriculture and Life Science Gyeongsang National UniversityJinju52828Republic of Korea Department of Animal Science College of Natural Resources&Life SciencePusan National UniversityMiryang50463Republic of Korea Life and Industry Convergence Research Institute Pusan National UniversityMiryang50463Republic of Korea University-Centered Labs Gyeongsang National UniversityJinju52828Republic of Korea Ruminant Nutrition and Anaerobe Laboratory Department of Animal Science and TechnologySunchon National UniversitySuncheon57922Republic of Korea Division of Applied Life Science(BK21) Gyeongsang National UniversityJinju52828Republic of Korea

Heat stress(HS)damages livestock by adversely affecting physiological and immunological ***,fundamental understanding of the metabolic and immunological mechanisms in animals under HS remains elusive,particularly in *** understand the changes on metabolic and immune responses in steers under HS condition,we performed RNA-sequencing and proton nuclear magnetic resonance spectroscopy-based metabolomics on HS-free(temperature humidity index[THI]value:64.92±0.56)and HS-exposed(THI value:79.13±0.56)Jersey steer(n=8,body weight:559.67±32.72 kg).This study clarifies the metabolic changes in 3 biofluids(rumen fluid,serum,and urine)and the immune responses observed in the peripheral blood mononuclear cells of HS-exposed *** integrated approach allowed the discovery of HS-sensitive metabolic and immunological *** metabolomic analysis indicated that HS-exposed steers showed potential HS biomarkers such as isocitrate,formate,creatine,and riboflavin(P<0.05).Among them,there were several integrative metabolic pathways between rumen fluid and ***,HS altered mRNA expression and immune-related signaling pathways.A meta-analysis revealed that HS decreased riboflavin metabolism and the expression of glyoxylate and dicarboxylate metabolism-related ***,metabolic pathways,such as the hypoxia-inducible factor-1 signaling pathway,were downregulated in immune cells by HS(P<0.05).These findings,along with the datasets of pathways and phenotypic differences as potential biomarkers in steers,can support more in-depth research to elucidate the interrelated metabolic and immunological *** would help suggest new strategies to ameliorate the effects of HS,including disease susceptibility and metabolic disorders,in Jersey steers.

关键词： Heat stress Jersey steer Metabolome Transcriptome Immunity Metabolism

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