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Molecular Dynamics Simulation for Grain Boundary Deformation under Tensile Loading Condition

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Journal of Materials Science & Technology 2001年第1期17卷 145-146页

作者： Kim, YS choi, DY Won, SY Kyungpook Natl Univ Dept Mech Engn Taegu South Korea Kyungpook Natl Univ Grad Sch Mech Engn Taegu South Korea

In this study, MD simulations have been performed to observe the behavior of a grain boundary in an alpha -Fe plate under 2-dimensional loading. In MD simulation, the acceleration of every molecule can be achieved from the potential energy and the force interacting between each molecule, and the integration of the motion equation by using Verlet method gives the displacement of each molecule. Initially, four alpha -Fe rectangular plates having different misorientation angles of grain boundary were modeled by using the Johnson potential and Morse potential. We compared the potential energy of the grain boundary system with that of the perfect structure model. Also, we could obtain the width of the grain boundary by investigating the local potential energy distribution. The tensile loading for each grain boundary models was applied and the behavior of grain boundary was studied. From this study it was clarified that in the case using Johnson potential, the obvious fracture mechanism occurs along the grain boundary, in the case of Morse potential, the diffusion of the grain boundary appears instead of the grain boundary fracture.

关键词： Simulation Molecular Dynamics Simulation for Grain Boundary Deformation under Tensile Loading Condition

Short-circuit Current Characteristics of Wind Generators

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电力系统自动化 2012年第8期36卷 110-114页

作者： Seung-Jae LEE Myeon-Song choi Department of Electrical Engineering Myongji University

To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is *** there are many researches on the issue,a clear agreement has not been reached so *** SCC characteristics for different wind generators are *** simulation is performed in the same system integrated with different kinds of wind generators,and their results are compared with those reported in IEEE *** detection possibility by overcurrent relay(OCR)is discussed based on the simulation results.

关键词：风力发电机组短路电流电流特性配电系统 PSCAD 过流继电器 IEEE 通过检测

IgSF11-mediated phosphorylation of pyruvate kinase M2 regulates osteoclast differentiation and prevents pathological bone loss

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Bone Research 2023年第1期11卷 215-227页

作者： Hyunsoo Kim Noriko Takegahara Yongwon choi Department of Pathology and Laboratory Medicine University of Pennsylvania Perelman School of MedicinePhiladelphiaPA19104USA

Osteoclasts are primary bone-resorbing cells,and receptor-activated NF-k B ligand(RANKL)stimulation is the key driver of osteoclast *** late-stage differentiation,osteoclasts become multinucleated and enlarged(so-called“maturation”),suggesting their need to adapt to changing metabolic demands and a substantial increase in ***,we demonstrate that immunoglobulin superfamily 11(Ig SF11),which is required for osteoclast differentiation through an association with the postsynaptic scaffolding protein PSD-95,regulates osteoclast differentiation by controlling the activity of pyruvate kinase M isoform2(PKM2).By using a system that directly induces the activation of Ig SF11 in a controlled manner,we identified PKM2 as a major Ig SF11-induced tyrosine-phosphorylated *** SF11 activates multiple Src family tyrosine kinases(SFKs),including c-Src,Fyn,and Hc K,which phosphorylate PKM2 and thereby inhibit PKM2 ***,Ig SF11-deficient cells show higher PKM2activity and defective osteoclast ***,inhibiting PKM2 activities with the specific inhibitor Shikonin rescues the impaired osteoclast differentiation in Ig SF11-deficient cells,and activating PKM2 with the specific activator TEPP46 suppresses osteoclast differentiation in wild-type ***,PKM2 activation further suppresses osteoclastic bone loss without affecting bone formation in *** together,these results show that Ig SF11 controls osteoclast differentiation through PKM2 activity,which is a metabolic switch necessary for optimal osteoclast maturation.

关键词： SF11 osteoclast impaired

Compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni bulk metallic glasses

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 318-322页

作者： Jihye An Hyunjune Yim choi-Yim Haein Department of Physics Sookmyung Women's University Department of Mechanical & System Design Engineering Hongik University

Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature （Tg） and crystallization temperature （Tx） were obtained for the alloys using differential scanning calorimetry （DSC） at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization temperature （△Tx=Tx-Tg） are measured with values ranging up to 33-55 K. The reduced glass transition temperature （Trg）, which is the ratio of the glass temperature to the liquidus temperature （T3, is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson＇s ratio were also given.

关键词： bulk metallic glasses (BMGs) quatemary alloys elastic constants glass-forming ability

Probabilistic seismic performance assessment of lap-spliced RC columns retrofitted by steel wrapping jackets

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 223-238页

作者： Eunsoo choi Heejung Youn Baik-Soon Cho Department of Civil Engineering Hongik University Department of Civil Engineering CTRCInje University

In this study, the seismic fragility curves of two reinforced concrete（RC） columns that were lap-spliced at the bottom and retrofitted with steel wrapping jackets were generated. Their seismic performance was probabilistically assessed in comparison to that of lap-spliced or continuous reinforcement RC columns. This study used two types of steel wrapping jackets, a full jacket and a split jacket. Analytical models of the four types of columns were developed based on the experimental results of the columns using Open SEES, which is effective in conducting nonlinear time history analyses. A suite of ten artificial ground motions, modified from recorded ground motions, was used to perform nonlinear time history analyses of the analytical models with scaling of the peak ground acceleration from 0.1 g to 1.0 g in increments of 0.1 g. The steel wrapping jackets did not increase the medians for yield（slight damage state） of the lap-spiced column and did not exceed the corresponding median of the continuous reinforcement column. However, the two steel jackets increased the medians for failure by 1.872 and 2.017 times, respectively, and exceeded the corresponding median of the continuous reinforcement column by 11.8% and 20.5%, respectively.

关键词： columns reinforcement reinforced exceed acceleration scaling median assessed split probabilistic

Evaluation of anti-tubercular activity of linolenic acid and conjugatedlinoleic acid as effective inhibitors against Mycobacterium tuberculosis

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Asian Pacific Journal of Tropical Medicine 2016年第2期9卷 121-125页

作者： Won Hyung choi Department of Biomedical Science and Department of Medical Zoology Kyung Hee University School of Medicine

Objective: To evaluate a new pharmacological activity/effect of linolenic acid(α- and γ-form) and conjugated-linoleic acid(CLA) causing antibacterial activity against Mycobacterium tuberculosis(Mtb). Methods: The anti-Mtb activity/effect of linolenic acid and CLA were determined using different anti-Mtb indicator methods such as resazurin microtiter assay(REMA) and MGIT 960 system assay. The Mtb was incubated with various concentrations(12.5–200) μg/m L of the compounds and anti-Mtb first-line drugs for 5 d in the REMA, and for 3 wk in MGIT 960 system assay. Results: Linolenic acid and CLA obviously indicated their anti-Mtb activity/effect by strongly inhibiting the growth/proliferation of Mtb in a dosedependent manner in the REMA and the MGIT 960 system assay. Interestingly, linolenic acid and CLA consistently induced anti-Mtb activity/effect by effectively inhibiting the growth/proliferation of Mtb in MGIT 960 system for 21 d with a single-treatment, and their minimum inhibitory concentrations were measured as 200 μg/m L respectively. Conclusions: These results demonstrate that linolenic acid and CLA not only have effective anti-Mtb activity/properties, but also induce the selective-anti-Mtb effects by strongly inhibiting and blocking the growth/proliferation of Mtb through a new pharmacological activity/action. Therefore, this study provides novel perspectives for the effective use of them and the potential that can be used as potent anti-Mtb candidate drugs, as well as suggests the advantage of reducing the cost and/or time for developing a new/substantive drug by effectively repurposing the existing drugs or compounds as one of new strategies for the global challenge of tuberculosis.

关键词： MGIT 960 system Tuberculosis Drug susceptibility testing γ-linolenic acid

Enhanced photocatalytic degradation of lindane using metal–semiconductor Zn@ZnO and ZnO/Ag nanostructures

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Journal of Environmental Sciences 2018年第12期30卷 107-115页

作者： Hyeon Jin Jung Ravindranadh Koutavarapu Seulki Lee Ju Hyun Kim Hyun Chul choi Myong Yong choi Department of Chemistry (BK21+) and Research Institute of Natural Science Gyeongsang National University Department of Chemistry Chonnam National University

To achieve enhanced photocatalytic activity for the degradation of lindane, we prepared metal–semiconductor composite nanoparticles（NPs）. Zn@ZnO core–shell（CS） nanocomposites, calcined ZnO, and Ag-doped ZnO（ZnO/Ag） nanostructures were prepared using pulsed laser ablation in liquid, calcination, and photodeposition methods, respectively, without using surfactants or catalysts. The as-prepared catalysts were characterized by using X-ray diffraction（XRD）, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet–visible（UV–vis） spectroscopy, and photoluminescence spectroscopy. In addition, elemental analysis was performed by energy dispersive X-ray spectroscopy. The obtained XRD and morphology results indicated good dispersion of Zn and Ag NPs on the surface of the ZnO nanostructures. Investigation of the photocatalytic degradation of lindane under UV–vis irradiation showed that Zn@ZnO CS nanocomposites exhibit higher photocatalytic activity than the other prepared samples. The maximum degradation rate of lindane was 99.5% in 40 min using Zn@ZnO CS nanocomposites. The radical trapping experiments verified that the hydroxyl radical（·OH） was the main reactive species for the degradation of lindane.

关键词： Zn@ZnO ZnO/Ag Lindane Pulsed laser ablation in liquid Photocatalysis

Numerical analysis of thermal plasma scrubber for CF4 decomposition

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Plasma Science and Technology 2019年第6期21卷 9-14页

作者： J KO T H KIM S choi Department of Nuclear and Energy Engineering Jeju National University Jeju 63243 Republic of Korea Institute for Nuclear Science and Technology Jeju National University Jeju 63243 Republic of Korea

CF4 gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse *** must be removed or converted safely due to its extreme *** a CF4 decomposition system using a thermal plasma scrubber was commercialized,its removal efficiency is *** this work,a numerical analysis of CF4 decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition *** decomposition and recombination temperatures of CF4 were analyzed using thermodynamic equilibrium *** chemical reaction of CF4 decomposition into carbon and fluorine gas was considered in this numerical *** injection position and angle of the CF4 were controlled in order to enhance the decomposition *** vertical injection of CF4 near the torch exit improved the mixing of the CF4 with the thermal plasma *** addition,it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped *** a result,it is revealed that the CF4 injection location and the reactor configuration are the most important factors in improving the decomposition rate.

关键词： numerical simulation decomposition CF4 thermal plasma scrubber

Reaction mechanism and additional lithium storage of mesoporous MnO_(2) anode in Li batteries

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Journal of Energy Chemistry 2021年第2期30卷 276-284,I0010页

作者： Jaesang Yoon Woosung choi Taewhan Kim Hyunwoo Kim Yun Seok choi Ji Man Kim Won-Sub Yoon Department of Energy Science Sungkyunkwan UniversitySuwon 16419South Korea Department of Chemistry Sungkyunkwan UniversitySuwon 16419South Korea

Nanostructured transition metal oxides,employed as anode materials for lithium-ion batteries,exhibit a higher capacity than the theoretical capacity based on the conversion *** date,the reasons behind this phenomenon are *** the one-step evolution of anode material for lithium-ion batteries,it is essential to understand the lithium storage reaction mechanism of the anode ***,we provide a detailed report on the lithium storage and release mechanism of MnO2,using synchrotron-based X-ray techniques.X-ray diffraction and X-ray absorption spectroscopy results indicate that during the first discharge,MnO2 is reduced in the order of MnO2→LixMnO2(1

关键词： Mesoporous MnO_(2) Reaction mechanism Electrolyte-derived surface layer Synchrotron-based X-ray techniques Anode Li battery