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Park, Jaeyeong,Choi, Sungyeol,Sohn, Sungjune,Kim, Kwang-Rag,Hwang, Il Soon The Electrochemical Society 2014 Journal of the Electrochemical Society Vol.161 No.3
<P>This study examines zirconium electrochemical redox behaviors in LiCl-KCl-ZrCl4 at 500 degrees C. Cyclic voltammetries are conducted with tungsten working and counter electrode. Four oxidation peaks and three reduction peaks are observed and redox reactions which could contribute to each peak are determined based on electrolysis results and peak height changes of cyclic voltammogram according to scan rates and ranges. Zr(IV) could be reduced into ZrCl when cathode potential is more negative than -1.1 V (vs. 1 wt% Ag/AgCl) and ZrCl would be reduced into Zr metal if cathode potential become more negative than -1.2 V. ZrCl and Zr metal could be oxidized into mainly Zr(IV) in LiCl-KCl-ZrCl4(1 wt%). Zr(II) could exist in the molten salt but the concentration might be small because heights of cyclic voltammogram peaks related to redox reactions of Zr(II) are relatively small. Based on cyclic voltammetry results, suggestions for the electrorefining of irradiated Zircaloy-4 cladding are proposed. High cathodic current density is preferred to recover zirconium as a metal state and low anodic current density is required to prevent dissolution of elements which are more reductive than zirconium. (C) 2013 The Electrochemical Society. All rights reserved.</P>
Park, Jihun,Kim, Joohee,Kim, Kukjoo,Kim, So-Yun,Cheong, Woon Hyung,Park, Kyeongmin,Song, Joo Hyeb,Namgoong, GyeongHo,Kim, Jae Joon,Heo, Jaeyeong,Bien, Franklin,Park, Jang-Ung The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.20
<P>Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the 'Internet of Things' area.</P>
Park, Jaeyeong,Kang, Minju,Sohn, Seok Su,Kim, Sang-Heon,Kim, Hyoung Seop,Kim, Nack J.,Lee, Sunghak Elsevier 2017 Materials science & engineering. properties, micro Vol.684 No.-
<P><B>Abstract</B></P> <P>As automotive steels require high impact resistance for absorbing impact energy upon vehicle body collision, detailed investigation of dynamic deformation behavior of TWinning Induced Plasticity (TWIP) steels is essentially needed. Here we show a plausible explanation of improving dynamic tensile properties by investigating deformation mechanisms using transmission electron microscopy and electron back-scatter diffraction analyses of interrupted tensile specimens. According to microstructural evolution results, slip mechanisms change from wavy slip to (planar+wavy) slip with increasing strain rate. With respect to twinning, the transition occurs from stacking faults to primary twins with increasing strain under quasi-static loading, while twinning becomes more activated under dynamic loading. Due to favorable effects of increased planar slip and twinning on tensile properties, the TWIP steel shows higher strength and similar ductility under dynamic loading. Our results demonstrate desirable applications of the TWIP steel to automotive steel sheets demanding excellent safety requirement of vehicle body.</P>
Park, Jeong Min,Moon, Jongun,Bae, Jae Wung,Jang, Min Ji,Park, Jaeyeong,Lee, Sunghak,Kim, Hyoung Seop Elsevier Sequoia 2018 Materials science & engineering Structural materia Vol.719 No.-
<P><B>Abstract</B></P> <P>In this work, the effects of strain rate on mechanical deformation and microstructural evolution of CoCrFeMnNi high-entropy alloy (HEA) under quasi-static and dynamic compression were investigated. The HEA exhibited high strain-rate sensitivity values (m = 0.028) of yield strength under quasi-static conditions. In particular, due to the viscous drag effect, the variation of yield strength with strain rate under dynamic compression was much larger than that under quasi-static compression. Microstructural analysis using electron backscatter diffraction shows profuse twinning under both conditions. The dynamically deformed specimens exhibited strongly localized deformation regions (i.e., adiabatic shear bands). The process of dynamic compressive behavior in this HEA is competitive between hardening by dislocation and twinning, and thermal softening. To analyze numerically the flow behavior of the HEA under dynamic conditions, the modified Johnson-Cook model considering adiabatic temperature rise was employed. The modified Johnson-Cook model offered good agreement with experimental results regarding dynamic flow curves of this HEA.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Park Jaeyeong,Kim Taehee,Muhammad Buhari Lawan,Ki Jang-Seu 한국미생물학회 2023 The journal of microbiology Vol.61 No.6
Ship biofouling is one of the main vectors for the introduction and global spread of non-indigenous organisms. Diatoms were the early colonizers of ship hulls; however, their community composition on ships is poorly understood. Herein, we investigated the diatom community on the hull samples collected from two Korean research vessels Isabu (IRV) and Onnuri (ORV) on September 2 and November 10, 2021, respectively. IRV showed low cell density (345 cells/cm2) compared to ORV (778 cells/cm2). We morphologically identified more than 15 species of diatoms from the two research vessels (RVs). The microalgae in both RVs were identified as Amphora, Cymbella, Caloneis, Halamphora, Navicula, Nitzschia, and Plagiogramma. Of them, the genus Halamphora was found to be predominant. However, both RVs had a varied dominant species with a significant difference in body size; Halamphora oceanica dominated at IRV, and Halamphora sp. at ORV, respectively. Molecular cloning showed similar results to morphological analysis, in which Halamphora species dominated in both RVs. The hull-attached species were distinct from species found in the water column. These results revealed diatoms communities that are associated with ship hull-fouling at an early stage of biofilm formation. Moreover, ships arriving from different regions could show some variation in species composition on their hull surfaces, with the potential for nonindigenous species introduction.
Park Jaeyeong,Shin Eunkyoung,Yeom Ji-Hyun,Choi Younkyung,주민주,이민호,Kim Je Hyeong,Bae Jeehyeon,Lee Kangseok 한국미생물학회 2022 The journal of microbiology Vol.60 No.1
Acinetobacter baumannii causes multidrug resistance, leading to fatal infections in humans. In this study, we showed that Lys AB2 P3-His–a hexahistidine-tagged form of an antimicrobial peptide (AMP) loaded onto DNA aptamer-functionalized gold nanoparticles (AuNP-Apt)–can effectively inhibit A. baumannii infection in mice. When A. baumannii-infected mice were intraperitoneally injected with AuNP-Apt loaded with Lys AB2 P3-His, a marked reduction in A. baumannii colonization was observed in the mouse organs, leading to prominently increased survival time and rate of the mice compared to those of the control mice treated with AuNP-Apt or Lys AB2 P3-His only. This study shows that AMPs loaded onto AuNP-Apt could be an effective therapeutic tool against infections caused by multidrug-resistant pathogenic bacteria in humans.
Park, Jaeyeong,Choi, Sungyeol,Sohn, Sungjune,Hwang, Il Soon The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12
<P>To achieve a better understanding of Zircaloy-4 electrorefining in LiCl-KCl at 500 degrees C, redox behaviors of Zr, Sn, Cr, Fe and Co, were examined by cyclic voltammetry using tungsten working and counter electrode. Zr metal can be produced from Zr4+ through two step reduction and ZrCl is generated as an intermediate product. As ZrCl4 concentration decreases, ZrCl would be easily reduced into Zr metal. In addition, Zr2+ formation would be unlikely at low ZrCl4 concentration. The redox reactions of the other elements are much simpler than Zr. The reduction of Zr4+ into ZrCl was close to irreversible but the reduction reactions of the other elements are close to reversible. The diffusion coefficients and apparent reduction potentials were calculated using equations for a reversible or irreversible reaction. The diffusion coefficients are in the order of 10(-9) m(2)/s and Zr is less reductive than other elements. (C) 2017 The Electrochemical Society. All rights reserved.</P>