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Microstructure and heat resistance of Mg–Al–Zn alloys containing metastable phase
Kim, Jeong-Min,Park, Bong-Koo,Jun, Joong-Hwan,Shin, Keesam,Kim, Ki-Tae,Jung, Woon-Jae Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-
<P><B>Abstract</B></P><P>In this research microstructural studies have been made on cast specimens of AZ91 base alloys containing various amounts of Zn. As the amount of Zn addition increased up to 2%, any new Zn-containing phase did not appear while the Zn content in Mg<SUB>17</SUB>Al<SUB>12</SUB> phase continuously increased. A quasi-crystalline phase started to form at Mg<SUB>17</SUB>Al<SUB>12</SUB> phase when the added Zn content was about 3wt.%. The tensile strength and elongation of the alloys at 175°C were observed to increase significantly with increasing Zn content. The quasi-crystalline phase was found to be stable up to 300°C, based on scanning electron microscopy examinations of the specimens heated at different temperatures for 24h.</P>
Performance Evaluation of Textile-Based Electrodes and Motion Sensors for Smart Clothing
Gilsoo Cho,Keesam Jeong,Min Joo Paik,Youngeun Kwun,Moonsoo Sung IEEE 2011 IEEE SENSORS JOURNAL Vol.11 No.12
<P>Development of textile-based electrodes and motion sensors is one of the main issues of recent smart textile research utilizing electronic textiles. Electrocardiogram (ECG) electrodes have been developed by various textile technologies such as sputtering or electroless-plating on the fabric surfaces, and embroidering or knitting with stainless steel yarns. In addition, two types of motion sensors have also been developed using piezo-resistive textiles. They were fabricated by knitting and braiding. To examine the usability of the ECG electrode, waveforms of the conventional AgCl electrode, and the new electrodes developed in our lab were compared. It was found that electrodes using metallic embroidering are more efficient when its substrate was a metal blended fabric. The electrolessly Cu/Ni plated fabrics obtained the best conductivity in textile-based electrodes. The first motion-measuring textile-based sensor was used to predict and measure the changes in electric resistances that accompany the angle changes in the elbow joint. An advanced piezo-resistive textile by braiding showed more accurate resistance changes and also better durability. Changes in its electrical resistance were mapped to changes in its length extension. From the relationship between the extension and the electrical resistance, movement or posture of human body was detected.</P>
Development of the Hybrid Conjugated Polymer Solar Cell Based on GaN Quantum Dots
Kim, Minji,Shin, Min Jeong,Gwon, Dongoh,Ahn, Hyung Soo,Yi, Sam Nyung,Kim, Pan Seok,Yoon, Sung Cheol,Lee, Changjin,Park, Jungsik,Shin, Keesam,Ha, Dong Han,Sawaki, Nobuhiko IOP Publishing 2013 Japanese journal of applied physics Vol.52 No.1
심전도 자동진단을 위한 60Hz 전원잡음 제거 필터에 관한 연구
권혁제,정기삼,이명호,Kweon, Hyukje,Jeong, Keesam,Lee, Myoungho 대한의용생체공학회 1996 의공학회지 Vol.17 No.1
Diverse digital filters have been designed previously to eliminate powerline(AC) interference in the electrocardiouam. This paper describes filtering methods which have been developed recursive notch, adaptive, IEF(Incremental Estimation Filter) and proposes a new AIEF(Advanced Incremental Estimation Filter) method. The performances of these filters are compared on artificial signals as well as actual ECG signals with the aid of validated CSE(Common Standards for Quantitative Electrocardiowaphy). AC interference in this database is shown to exhibit two qualities especially relevant to filter design : considerable deviations from a nominal 60Hz frequency and substantial noise at higher harmonics.
He, Yinsheng,Yoo, Keun-Bong,Park, Joong Cheul,Lee, Byung-Ho,Yoon, Jeong-Bong,Kim, Jung-Gu,Shin, Keesam Elsevier 2018 Materials characterization Vol.142 No.-
<P><B>Abstract</B></P> <P>This study investigated the corrosion behavior and underline mechanisms of low alloy steels with a minor addition of 0.4 wt% Cu, 0.2 wt% Ni, 0.1 wt% Sb and 0.05 wt% Co developed for a flue gas desulfurization (FGD) system. Corrosion tests were carried out in an aggressive solution of 16.9 vol% H<SUB>2</SUB>SO<SUB>4</SUB> + 0.35 vol% HCl + Bal. H<SUB>2</SUB>O at 60 °C for up to 48 h. The experimental results revealed enrichment of the additional elements (Cu, Sb and Ni) in the corrosion layer, whose concentration increased with test time. As the concentrations of Cu increased, the crystallization and growth of the Cu particles (from several nm to 320 nm)) within the corrosion layer was accelerated. At the initial stage of the test, a continuous amorphous layer rich with the additional elements formed and covered the surface of the steel, which then gradually developed defects, pores and cracks, as the crystallization and growth of Cu particles with the elapse of time. The results indicated that the corrosion resistance of the low alloy steel depends on the existence form of Cu in the corrosion layer, i.e., as solute atoms or as nanoparticles strengthened the corrosion layer and increased corrosion resistance. As the coarsening of Cu particles weakened the corrosion layer and deteriorated the corrosion resistance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Corrosion mechanism of low alloy steels for flue gas desulfurization was studied. </LI> <LI> An amorphous corrosion layer enriched with Fe, O, S formed on the blank specimen. </LI> <LI> Added Cu concentrated, crystallized and grown to particles in corrosion layer. </LI> <LI> Corrosion resistance of the steels depended on the form of Cu in corrosion layer. </LI> <LI> Sb addition slows the crystallization and growth of Cu particles in corrosion layer. </LI> </UL> </P>
초초임계압 발전용 소재의 장시간 열처리에 따른 미세조직 변화와 기계적 특성의 상관관계 연구
주성욱,유정훈,신기삼,허성강,이재현,석진익,김정태,김병훈,Joo Sungwook,Yoo Junghoon,Shin Keesam,Hur Sung Kang,Lee Je-Hyun,Suk Jin Ik,Kim Jeong Tae,Kim Byung Hoon 한국재료학회 2005 한국재료학회지 Vol.15 No.1
For the good combination of high-temperature strength, toughness and creep property, $9-12\%$ chromium steels are often used for gas turbine compressors, steam turbine rotors, blade and casing. In this study, the correlation of microstructural evolution and mechanical properties was investigated fur the specimens heat-treated at 600, 650 and $700^{\circ}C$ for 1000, 3000 and 5000 hrs. The microstructure of as-received specimen was tempered martensite with a high dislocation density, small sub-grains and fine secondary phase such as $M_23C_6$. Aging for long-time at high temperature caused the growth of martensite lath and the decrease of dislocation density resulting in the decrease in strength. However, the evolution of secondary phases had influence on hardness, yield strength and impact property. In the group A specimen aged at $600^{\circ}C\;and\;650^{\circ}C$, Laves phase was observed. The Laves phase caused the increase of the hardness and the decrease of the impact property. In addition, the abrupt growth of secondary phases caused decrease of the impact property in both A and B group specimens.
Park, Jung Sik,Yang, Jun-Mo,Park, Kyung Jin,Park, Yun Chang,Yoo, Jung Ho,Jeong, Chil Seong,Park, Jucheol,He, Yinsheng,Shin, Keesam Oxford University Press 2014 Microscopy Vol.63 No.1
<P>Growing a GaN film on a patterned Al<SUB>2</SUB>O<SUB>3</SUB> substrate is one of the methods of reducing threading dislocations (TDs), which can significantly deteriorate the performance of GaN-based LEDs. In this study, the microstructural details of the GaN film grown on a cone-shaped patterned Al<SUB>2</SUB>O<SUB>3</SUB> substrate were investigated using high-resolution transmission electron microscopy and weak-beam dark-field techniques. Various defects such as misfit dislocations (MDs), recrystallized GaN (R-GaN) islands and nano-voids were observed on the patterned Al<SUB>2</SUB>O<SUB>3</SUB> surfaces, i.e. the flat surface (FS), the inclined surface (IS) and the top surface (TS), respectively. Especially, the crystallographic orientation of R-GaN between the GaN film and the inclined Al<SUB>2</SUB>O<SUB>3</SUB> substrate was identified as [Formula], [Formula]. In addition, a rotation by 9° between [Formula] and [Formula] and between [Formula] and [Formula] was found to reduce the lattice mismatch between the GaN film and the Al<SUB>2</SUB>O<SUB>3</SUB> substrate. Many TDs in the GaN film were observed on the FS and TS of Al<SUB>2</SUB>O<SUB>3</SUB>. However, few TDs were observed on the IS. Most of the TDs generated from the FS of Al<SUB>2</SUB>O<SUB>3</SUB> were bent to the inclined facet rather than propagating to the GaN surface, resulting in a reduction in the dislocation density. Most of the TDs generated from the TS of Al<SUB>2</SUB>O<SUB>3</SUB> were characterized as edge dislocations.</P>