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Flexible and Robust Transmission for Physical Layer Signaling of ATSC 3.0
Hongsil Jeong,Kyung-Joong Kim,Seho Myung,Jong-Woong Shin,Jinwoo Kim,Sung-Ik Park,Sunhyoung Kwon,Yijun Shi,Sang-Hyo Kim IEEE 2016 IEEE transactions on broadcasting Vol.62 No.1
<P>The physical layer [layer-1 (L1)] signaling (L1 signaling) of Advanced Television Systems Committee (ATSC) 3.0 is studied. In the new digital broadcasting system, ATSC 3.0, L1 signaling is designed to be more efficient but still robust compared with preceding standards such as DVB-T2. We introduce the error protection scheme of ATSC 3.0 in detail. Especially advanced methods newly employed in ATSC 3.0 are investigated with regard to its purpose and benefit in comparison to conventional DVB-T2.</P>
ZrO<sub>2</sub>가 코디어라이트-뮬라이트 세라믹스의 기계적 강도 및 내열충격성에 미치는 영향
임진현,김시연,여동훈,신효순,정대용,Lim, Jin-Hyeon,Kim, Shi Yeon,Yeo, Dong-Hun,Shin, Hyo-Soon,Jeong, Dae-yong 한국재료학회 2018 한국재료학회지 Vol.28 No.12
Cordierite composed of an alumina-silica-magnesia compound has a low coefficient of thermal expansion(CTE) and excellent thermal shock resistance. It also has a low dielectric constant and high electrical insulation. However, due to low mechanical strength, it is limited for use in a ceramic heater. In this study, $ZrO_2$ is added to an 80 wt% cordierite-20 wt% mullite composition, and the effect of $ZrO_2$ addition on the mechanical strength and thermal shock resistance is investigated. With an increasing addition of $ZrO_2$, cordierite-mullite formed $ZrO_2$, $ZrSiO_4$ and spinel phases. With sintering conducted at $1400^{\circ}C$ with the addition of 5 wt% $ZrO_2$ to 80 wt% cordierite-20 wt% mullite, the most dense microstructure forms along with an excellent mechanical strength with a 3-point flexural strength of 238MPa. When this composition is quenched in water at ${\Delta}T=400^{\circ}C$, the 3-point flexural strength is maintained. Moreover, when this composition is cooled from $800^{\circ}C$ to air, the 3-point flexural strength is maintained even after 100 cycles. In addition, the CTE is measured as $3.00{\times}10^{-6}{\cdot}K^{-1}$ at $1000^{\circ}C$. Therefore, 80 wt% cordierite-20 wt% mullite with 5 wt% $ZrO_2$ is considered to be appropriate as material for a ceramic heater.
Cr<sub>2</sub>O<sub>3</sub>-MgO-Y<sub>2</sub>O<sub>3</sub> 첨가에 따른 뮬라이트 세라믹스의 기계적 성질
임진현,김시연,여동훈,신효순,정대용,Lim, Jin-Hyeon,Kim, Shi Yeon,Yeo, Dong-Hun,Shin, Hyo-Soon,Jeong, Dae-Yong 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.12
Mullite ($3Al_2O_3{\cdot}2SiO_2$) has emerged as a promising candidate for high-temperature structural materials due to its erosion resistance, chemical and thermal stabilities, relatively low thermal expansion coefficient, excellent thermal shock and creep resistances, and low dielectric constant. However, since the pure mullite sintering temperature is as high as $1,600{\sim}1,700^{\circ}C$, there is an increasing need for a sintering additive capable of improving the strength characteristics while lowering the sintering temperature. Herein we have tried to obtain the optimal sintering additive composition by adding MgO, $Cr_2O_3$, and $Y_2O_3$ to mullite, followed by sintering at $1,325{\sim}1,550^{\circ}C$ for 2 h. With additives of 2 wt% of MgO, 2 wt% of $Cr_2O_3$, 4 wt% of $Y_2O_3$, A density of $3.23g/cm^3$ was obtained for the sintered body at $1,350^{\circ}C$ upon using 2 wt% MgO, 2 wt% $Cr_2O_3$, and 4 wt% $Y_2O_3$ as additives. The three-point flexural strength of that was 275 MPa and the coefficient of thermal expansion (CTE) was $4.15ppm/^{\circ}C$.
CAS glass와 Yb<sub>2</sub>O<sub>3</sub>를 이용한 2차상의 형상 제어가 AlN 세라믹의 열전도도 및 기계적 특성에 미치는 영향
최동규,김시연,여동훈,신효순,정대용,Choi, Dong Kyu,Kim, Shi Yeon,Yeo, Dong Hun,Shin, Hyo Soon,Jeong, Dae Yong 한국분말재료학회 (*구 분말야금학회) 2020 한국분말재료학회지 (KPMI) Vol.27 No.6
We investigate the effects of Yb2O3 and calcium aluminosilicate (CAS) glass as sintering additives on the sintering behavior of AlN. The AlN specimens are sintered at temperatures between 1700℃ and 1900℃ for 2 h in a nitrogen atmosphere. When the Yb2O3 content is low (within 3 wt.%), an isolated shape of secondary phase is observed at the AlN grain boundary. In contrast, when 3 wt.% Yb2O3 and 1 wt.% CAS glass are added, a continuous secondary phase is formed at the AlN grain boundary. The thermal conductivity decreases when the CAS glass is added, but the sintering density does not decrease. In particular, when 10 wt.% Yb2O3 and 1 wt.% CAS glass are added to AlN, the flexural strength is the highest, at 463 MPa. These results are considered to be influenced by changes in the microstructure of the secondary phase of AlN.
HVPE 방법에 의한 금속 화합물 탄소체 기판 위의 GaN 성장
김지영,이강석,박민아,신민정,이삼녕,양민,안형수,유영문,김석환,이효석,강희신,전헌수,Kim, Ji Young,Lee, Gang Seok,Park, Min Ah,Shin, Min Jeong,Yi, Sam Nyung,Yang, Min,Ahn, Hyung Soo,Yu, Young Moon,Kim, Suck-Whan,Lee, Hyo Suk,Kang, Hee Shi 한국결정성장학회 2013 韓國結晶成長學會誌 Vol.23 No.5
GaN는 대표적인 III-V족 질화물반도체로 주로 값싸고 다루기 쉬운 사파이어 기판 위에 성장된다. 하지만 사파이어 기판은 부도체이며, GaN과의 격자부정합을 일으키고 열전도도 또한 낮은 기판으로 알려져 있다. 본 논문에서는 방열기능과 열 전기전도도가 뛰어난 금속 화합물 탄소체 기판 위에 poly GaN epilayer를 HVPE법으로 성장시켜보았다. 비정질의 금속 화합물 탄소체 기판위에 성장되는 GaN epilayer의 성장메카니즘을 관찰하였다. GaN epilayer의 성장을 위해 HCl과 $NH_3$를 흘려주었다. 성장하기 위해 source zone과 growth zone의 온도는 각각 $850^{\circ}C$와 $1090^{\circ}C$로 설정했다. 성장이 끝난 샘플은 SEM, EDS, XRD측정을 통해 분석하였다. The GaN layer was typical III-V nitride semiconductor and was grown on the sapphire substrate which cheap and convenient. However, sapphire substrate is non-conductivity, low thermal conductivity and has large lattice mismatch with the GaN layer. In this paper, the poly GaN epilayer was grown by HVPE on the metallic compound graphite substrate with good heat dissipation, high thermal and electrical conductivity. We tried to observe the growth mechanism of the GaN epilayer grown on the amorphous metallic compound graphite substrate. The HCl and $NH_3$ gas were flowed to grow the GaN epilayer. The temperature of source zone and growth zone in the HVPE system was set at $850^{\circ}C$ and $1090^{\circ}C$, respectively. The GaN epilayer grown on the metallic compound graphite substrate was observed by SEM, EDS, XRD measurement.