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Hwang, Jiyong,Lee, Hoseong,Yi, Seonghoon Abingdon; Taylor & Francis Ltd 2016 PHILOSOPHICAL MAGAZINE Vol.96 No.24
<P>Fe-based amorphous ribbons with excellent soft magnetic properties and mechanical properties were prepared in the Fe-Si-P ternary system. Enhanced soft magnetic properties could be achieved through annealing treatment of the ribbons for 1h at 325 degrees C, which is far below the glass transition temperatures (462-474 degrees C). Icosahedral medium-range ordering with a size range of around 2nm occurred throughout the amorphous matrix during the low-temperature annealing treatment. The annealed ribbons exhibited improved magnetic saturation of over 185emu/g while maintaining good mechanical flexibility. During icosahedral ordering, the distance between the Fe atoms and the coordination number within the amorphous ribbon can be optimised for achieving high magnetic saturation. However, nanocrystallisation of the SiP and Fe2P transition phases embedded within the amorphous matrix occurred after the annealing treatment for 1h at 385 degrees C, which caused deterioration of the soft magnetic properties and mechanical flexibility of the ribbons. Therefore, the combination of high magnetic saturation and mechanical flexibility of the amorphous ribbons could be optimised through low-temperature annealing treatment without any nanocrystallisation.</P>
Jiyong Hwang,Hoseong Lee,Seonghoon Yi 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1
A novel nanocomposite structure comprising ~ 20-nm face-centered cubic Fe50Ni50nanocrystals embedded within an amorphousmatrix has been developed directly from a liquid alloy of Fe42Ni41.7C7Si4.5B3.9P0.9(at%) through melt-spinning. Graingrowth kinetics was significantly limited by the amorphous phase formed between nanocrystals. Glass forming elementsrejected from nanocrystals stabilize the amorphous phase restricting further growth of nanocrystals. The nanocompositeribbon exhibits excellent soft magnetic properties compared to those of the conventional micron-scale microstructuredFe50Ni50alloy known as 50 Permalloy. When the as-melt spun ribbon was heated to 600 °C, two exothermic events occurred. The formation of metastable C-rich Fe3Niand Si- and P-rich FeNi phases at low temperatures was confirmed by detailedtransmission electron microscopy analysis. The hard magnetic behaviors of these metastable phases were estimated basedon the hysteresis curve analysis results obtained from a ribbon heated to 600 °C. Through proper addition of glass-formingelements to FeNi-based alloys, nanocomposites with superior soft magnetic properties were effectively fabricated for massivepractical soft magnetic applications.
Single layer retarder with negative dispersion of birefringence and wide field-of-view
Hwang, Jiyong,Yang, Seungbin,Choi, Yu-Jin,Lee, Yumin,Jeong, Kwang-Un,Lee, Ji-Hoon The Optical Society 2016 Optics express Vol.24 No.17
<P>A single layer retarder possessing negative dispersion (ND) of birefringence as well as wide field-of-view (FOV) was long-term objective in optical science. We synthesized new guest reactive monomers with x-shape and mixed them with the host smectic reactive mesogen. The host-guest molecules formed two dimensionally self-organized nanostructure and showed both the ND of birefringence and wide FOV properties. We simulated the antireflection property of a circular polarizer using the optical properties of the retarder. The average reflectance of the retarder was 0.52% which was much smaller than that of the commercial single layer ND retarder 1.83%. (C) 2016 Optical Society of America</P>
섬유염색공정에서 컬러 매칭을 위해 수행되는 작업에 관한 연구
황지용(Jiyong-Hwang),오현우(Hyun-woo Oh) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6
This study investigated the dyeing process and problems of color matching of buyers order and dyed product in textile dyeing process. In addition, we investigated the conversion method of reflectance data to XYZ and Lab color space under the D65/10°light source using actual buyers order data, and calculated the color difference between the dyed product of each dyeing process and the buyers order.
Jiyong Woo,Belmonte, Attilio,Redolfi, Augusto,Hyunsang Hwang,Jurczak, Malgorzata,Goux, Ludovic IEEE 2016 IEEE electron device letters Vol.37 No.2
<P>In this letter, we experimentally investigate data retention in a copper (Cu)-based conductive bridge random-access memory device at a low current regime (10 mu A) in which retention is governed by factors other than just the conductive filament. Our findings show that the retention characteristics are determined by the local chemical potential of Cu between the conductive filament and its surrounding medium. Furthermore, the retention tendencies are described by the electrochemical reaction in accordance with the potential difference of Cu ions. Therefore, an appropriate quantity of Cu ions around the filament is important for achieving thermally reliable high and low resistance states over time.</P>
Radionuclide Transport Modeling in Excavation-Damaged Zone
Jiyong Lee,Weon Shik Han,Won Woo Yoon,Jeonghwan Hwang,Sanghoon Kwon 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Deep disposal facility for High-Level radioactive Waste (HLW) uses a multi-barrier system to prevent the leakage of radionuclide. As a part of the engineered barrier, bentonite is primarily considered as the main buffering material. This is due to the adsorption and swelling properties of the bentonite, which are expected to effectively impede leakage of the radionuclide. In many cases, adsorption is generally regarded as occurring only within the buffer zone. However, several research has been conducted to explore the possibility of bentonite intrusion into the Excavation- Damaged Zone (EDZ) generated during excavation processes, because of the swelling properties of the bentonite. Generally, for host rock near the deep disposal facility such as granite, groundwater flows through the fracture network. Therefore, analysis of the characteristics of the fracture network is essential for predicting the behavior of radionuclide in groundwater. Accordingly, the bentonite intrusion into the fracture network is critical for safety assessment of the deep disposal facility. To analyze this, hydro-geochemical model was established utilizing COMSOL Multiphysics and PHREEQC, observing changes of the behavior of U (VI) along fracture network due to the swelling of bentonite. Modeling was conducted with progressively changing intrusion depth of the bentonite. According to the results, the behavior of U (VI) exhibited significant changes depending on the connectivity of the fractures. Based on the distribution characteristics of the fracture network, heterogeneous groundwater flow was observed. U (VI) was transported through the preferential pathway, which indicates high connectivity, due to the rapid groundwater flow. Notably, when changing the intrusion depth of bentonite, significant differences in behavior of U (VI) were observed in the 0-20 cm case. In contrast, as the intrusion depth increased, it was observed that differences became less evident. These results indicate that changes in the properties of fracture network in EDZ due to the swelling of bentonite significantly influence the behavior of U (VI).
Jiyong Woo,Daeseok Lee,Euijun Cha,Sangheon Lee,Sangsu Park,Hyunsang Hwang IEEE 2013 IEEE electron device letters Vol.34 No.12
<P>In this letter, we discuss our technique for fabricating a vertically stacked ReRAM device composed of one selector and one resistor (1S-1R). We demonstrate that the nanoscale via-hole structure and 1-kb array architecture of selector device exhibit higher current density ( ~ 10<SUP>7</SUP> A/cm<SUP>2</SUP>) and reliability, and we introduce bipolar resistive switching element-a conductive-bridge RAM that can be stacked on top of the selector device. The resulting integrated 1S-1R device performs robust bipolar switching operations and significantly reduces the leakage current in cross-point applications.</P>