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Hong, Jaewoon,Balamurugan, Chandran,Im, Ha-Ni,Jeon, Sang-Yun,Yoo, Young-Sung,Song, Sun-Ju The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.3
<P>Ni-YSZ/YSZ/GDC/LSCF6428-GDC10 solid oxide cells were fabricated and investigated in high-temperature H2O/CO2 co-electrolysis using various inlet fuel compositions at 800 degrees C. Furthermore, to see the effect of infiltration on co-electrolysis, the precursor solution for a 10% gadolinium-doped ceria (GDC10) catalyst was dispersed into a fuel electrode backbone by a controlled urea/cation infiltration method. The influence of the inlet gas composition on the syngas product ratio was investigated by in-line gas chromatography. To understand the high-temperature H2O/CO2 co-electrolysis cell performance, electrochemical impedance spectroscopy (EIS) under open-circuit voltage and I-V characteristics, by the electrochemical reactions occurring at the electrodes of prepared solid oxide electrolysis cell (SOEC) were examined. When the inlet gas composition was N-2 63.5%, H-2 5%, CO2 11.5% and H2O 20% under electrolysis current density at -0.6 A cm(-2), the H-2/CO ratio of infiltrated cell was improved from 2.1 to 2.8 compared with the non-infiltrated cell. The thermodynamic factors determining the size, morphology and shape of the infiltrated particles were discussed. (C) The Author(s) 2018. Published by ECS.</P>
인지 라디오와 기존 라디오 시스템의 공존을 위한 인지적인 빔포밍 기법
김재운(Jaewoon Kim),김현욱(Hyunwook Kim),홍민기(Minki Hong),신요안(Yoan Shin) 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.3
본 논문에서는 인지 라디오 (Cognitive Radio; CR)와 기존 라디오 (Incumbent Radio; IR) 시스템의 공존을 위한 인지적인 빔포밍 (Cognitive Beamforming) 기법을 제안한다. 제안된 인지적인 빔포밍 기법은 스펙트럼 사용에 있어서 IR 시스템의 우선권을 보장하기 위해 동일한 시간에 동일한 주파수를 점유하고 있는 IR 시스템에게 아무런 간섭 영향도 일으켜서는 안 된다. 이와 더불어, 제안된 기법은 위 조건을 만족시키는 범위 내에서 CR 사용자에게는 최대 채널 이득을 제공할 수 있어야 한다. 이러한 목적을 위해, 제안된 기법은 추가적인 무선자원 소모없이 CR 사용자에게는 데이터 전송을 가능하게 하면서 IR 사용자에게는 아무런 간섭 영향도 일으켜서는 안 된다. 모의실험 결과, 제안된 기법을 사용할 경우 CR 사용자는 IR 사용자에게 간섭영향을 일으키지 않았으며, IR 시스템의 주파수 사용 우선권을 전혀 고려하지 않은 이상적인 빔포밍 시스템과 비교하여 CR사용자의 비트오율 (Bit Error Rate) 성능이 약간 열화됨을 확인하였다. In this paper, we propose a cognitive beamforming scheme for coexistence of CR (Cognitive Radio) and IR (Incumbent Radio) systems. In order to maintain the priority of the IR in spectrum utilization, the proposed cognitive beamforming scheme needs to have the CR not cause any interference to the IR systems occupying the same frequency band at the same time. In addition, the proposed scheme has to provide maximum channel gain to the CRU (CR User) in a boundary of satisfying the former criterion. For this purpose, the proposed scheme does not cause any interference to the IRU (IR User), while the CRU is served without additional radio resource consumption. From simulation, we confirmed that when using the proposed scheme the CRU does not interfere with the IRU and there is little bit error rate performance degradation of the CRU as compared to that of the ideal beamforming system which does not consider the IR priority.
An Effective MIMO–OFDM System for IEEE 802.22 WRAN Channels
Hyunwook Kim,Jaewoon Kim,Suckchel Yang,Minki Hong,Yoan Shin IEEE 2008 IEEE transactions on circuits and systems. a publi Vol.55 No.8
<P>We propose a closed-loop multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) transmission scheme appropriate for the IEEE 802.22 wireless regional area network (WRAN) channel environments. The proposed scheme utilizes the Grassmannian beamforming and an antenna selection algorithm to maintain bit-error-rate (BER) performance and to reduce feedback information. To further reduce the feedback information considering the channel property of the IEEE 802.22 WRAN, the proposed scheme employs an extension of the feedback period and subcarrier grouping. Simulation results in the IEEE 802.22 WRAN reference channel models indicate that the proposed MIMO-OFDM transmission scheme achieves superior BER performance and spectral efficiency than open-loop MIMO-OFDM system even considering the feedback overhead of the system.</P>
Plasma-sprayed gadolinium-doped ceria (GDC) for intermediate temperature solid electrolyte
Chanjin Son,Aman Bhardwaj,Jaewoon Hong,Jin-Wook Kim,Heung-Soo Moon,Hyo-Seop Noh,Sun-Ju Song 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.12
10 mol% gadolinium-doped cerium (IV) oxide was prepared by solid-state reaction route and deposited as a thick film usingthermal (plasma) spray technique. The phase development, microstructure and topography were characterized by X-raydiffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mechanical strength of thedeposited film was determined by pull-off adhesion test. The plasma-sprayed GDC was characterized for its electricalproperties by dc four-probe conductivity experiments. The maximum conductivity for plasma-sprayed GDC was found to be3.60 × 10−2 Scm−1, which was lesser than 2.25 × 10−1 Scm−1for the CIP-sintered GDC at 1000 oC and pO2= 0.21 atm. Thedecrease in the conductivity is attributed to the larger intergranular spaces and uneven networking observed in themicrostructure resulted in higher activation energy and low conductivity.
Balamurugan, C.,Son, Chanjin,Hong, Jaewoon,Song, Sun-Ju Elsevier 2018 Sensors and actuators. B Chemical Vol.262 No.-
<P><B>Abstract</B></P> <P>We have designed the solid-state electrochemical mixed potential type NiO and yttrium-stabilized zirconia (YSZ) composite based sensing electrode for selective detection of NO<SUB>x</SUB> at elevated temperatures. The planner NiO-YSZ composite sensing electrode could detect NO<SUB>x</SUB> even at 400 °C, with acceptable response/recovery rates. The change in emf values of the sensor varied linearly with NO<SUB>x</SUB> concentrations on a logarithmic scale in the range of 5–100 ppm. The response characteristic of the sensor was improved by modifying the surface with different vol% of pore former. As a result, obtained porous electrodes showed better response characteristics concerning speed and response owing to higher porosity. To improve response kinetics of porous NiO-YSZ electrode, NiO nanoparticles are infiltrated into an optimized NiO-YSZ sensing electrode surface by controlled urea/cation infiltration method. The experimental results demonstrated that NiO nanoparticles infiltrated NiO-YSZ sensor electrode reveal remarkably high emf response to NO<SUB>x</SUB> compared that of planar electrode, suggesting that NiO nanoparticles introduction can significantly enhance catalytic activity and electrochemical performance of NiO-YSZ electrode. Finally, the porosity effect of electrode subtracts (YSZ) with NO<SUB>x</SUB> gases response and recovery kinetics was examined under the optimum operating temperature at 400 °C. The sensing mechanism based on the mixed potential for the surface modified NiO-YSZ composite sensing electrode was discussed based on the obtained result of sensing characterizations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The detailed NO<SUB>x</SUB> gas sensing characteristics of NiO-YSZ based three different types of mixed potential sensing electrodes for the comparatively low operating temperature of 400 °C. </LI> <LI> Optimized NiO-YSZ electrode surface was modified by the addition of different vol% of pore former, it showed better response characteristics concerning speed and response. </LI> <LI> The NiO nanoparticles infiltrated NiO-YSZ sensing electrode shows a remarkably high emf variation to 100 ppm NO<SUB>x</SUB>, and it can detect a level as low as 3 ppm. </LI> <LI> The porosity effect of electrode subtracts (YSZ) with NO<SUB>x</SUB> gases response and recovery kinetics was also examined under the optimum operating temperature at 400 °C. </LI> </UL> </P>
Cognitive Radio와 Incumbent Radio의 공존을 위한 Cognitive Beamforming 기법
김현욱(Hyunwook Kim),김재운(Jaewoon Kim),홍민기(Minki Hong),신오순(Oh-Soon Shin),신요안(Yoan Shin) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.11
In this paper, we propose a cognitive beamforming scheme for coexistence of CR (Cognitive Radio) and IR (Incumbent Radio). The proposed cognitive beamforming does not cause any interference to the IRU (IR User), while the CRU (Cognitive Radio User) is served without additional radio resource consumption. Simulation results show that when using the proposed scheme the CRU does not interfere with the mu and there is IRU bit error rate performance degradation of the CRU as compared to that of the ideal beamforming system which does not consider the IR priority.
Lee, Myung Chul,Seonwoo, Hoon,Garg, Pankaj,Jang, Kyoung Je,Pandey, Shambhavi,Park, Sang Bae,Kim, Hong Bae,Lim, Jaewoon,Choung, Yun Hoon,Chung, Jong Hoon RSC Publications 2018 Biomaterials Science Vol.6 No.2
<P>Damage to the eardrum causes acute pain and can lead to chronic otitis media if it develops into chronic tympanic membrane (TM) perforations. Chronic TM perforations are usually treated with surgical methods such as tympanoplasty and myringoplasty. However, these surgeries are not only complicated and difficult but also cost a lot of money. Our research team developed chitosan patches (E-CPs) that release epidermal growth factor (EGF) as a patch therapy to replace surgical methods. However, there was a limitation in the healing ratio of the treatment compared to the surgical methods. In this study, we developed EGF and epidermal growth factor receptor (EGFR) gene-releasing polyethyleneimine (PEI)/chitosan patches (EErP-CPs) to increase the regeneration of TM perforations. The addition of PEI increased the adhesion and migration ability of TM cells on the patches. The simultaneous release of the EGF and the EGFR gene further enhanced TM cell proliferation, adhesion and migratory ability. It was confirmed that the EGF protein and EGFR gene were released for 30 days; however, EGF was released and increased TM cell viability almost immediately after treatment and EGFR took a minimum of 3 days before showing its effect on improved cell viability. It was also shown that EErP-CPs are more hydrophilic and have more positive charge than E-CP because of added amine groups from PEI. In conclusion, the developed EErP-CPs resulted in the improved healing of TM perforations and can potentially be applied to the regeneration of both chronic and acute tympanic membrane perforations.</P>
김동훈(Donghoon Kim),황준식(Joonsik Hwang),한상욱(Sangwook Han),배충식(Choongsik Bae),홍재웅(Jaewoon Hong),신상연(Sangyeon Shin) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
In recent years, there have been reports of erosion on the cylinder head water jacket from several vehicle manufacturers. This erosion may cause the deterioration in the cooling capacities of water jacket and furthermore raise serious damages to the engine. The main reason for this is widely known as repeating formation and collapse of bubbles caused by the heat transfer from the engine head to the water jacket. In this study, erosion and corrosion behavior of water jacket was investigated with a rectangular specimen under the high temperature condition, and the collapse pressure of bubbles on the specimen and approximated pit formation was calculated with OpenFOAM CFD package and the erosion model. As a result, increasing of pit area was validated with experimental data and collapse pressure of bubble was order of 10<SUP>10</SUP> Pa as mentioned by many references. It is expected that CFD method and erosion model can be used to predict water jacket design to protect erosion phenomena.
Establishment of the 2nd National Reference Standard for Diphtheria toxin in Korea
So Young Kim,Jinwoong Lee,Sol Jeon,Su Jung An,In yeong Hwang,Jae Hoon Moon,Jong Kwan Park,Taeseung Yang,Jaewoon Son,Daegeun Kim,Jeongwon Jang,Seulgi Park,Eun Ah Choi,Jin Kyu Kim,Jin Tae Hong,Jong Won 대한미생물학회 2021 Journal of Bacteriology and Virology Vol.51 No.1