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Oh, Dohyeok,Ryu, Jae-Hyun,Oh, Sehee,Jeong, Hoejeong,Park, Jisung,Jeong, Rae-Dong,Kim, Wonsik,Cho, Jaeil The Korean Society of Plant Pathology 2018 Plant Pathology Journal Vol.34 No.3
Crop yield is critically related to the physiological responses and disease resistance of the crop, which could be strongly affected by high temperature conditions. We observed the changes in the growth of barley under higher than ambient air-temperature conditions using a temperature gradient field chamber (TGFC) during winter and spring. Before the stem extension stage of barley growth, Cladosporium sp. spontaneously appeared in the TGFC. The severity of disease became serious under warmer temperature conditions. Further, the stomata closed as the severity of the disease increased; however, stomatal conductance at the initial stage of disease was higher than that of the normal leaves. This was likely due to the Iwanov effect, which explains that stressed plants rapidly and transiently open their stomata before longer-term closure. In this study, we tested three optical methods: soil-plant analysis development (SPAD) chlorophyll index, photochemical reflectance index (PRI), and maximum quantum yield (Fv/Fm). These rapid evaluation methods have not been used in studies focusing on disease stress, although some studies have used these methods to monitor other stresses. These three indicative parameters revealed that diseased barley exhibited lower values of these parameters than normal, and with the increase in disease severity, these values declined further. Our results will be useful in efficient monitoring and evaluation of crop diseases under future warming conditions.
오지성(Jisung Oh),최지용(Jiyong Choi),박의용(Euiyong Park),조인현(Inhyun Cho) 한국추진공학회 2021 한국추진공학회 학술대회논문집 Vol.2021 No.5
한국형발사체 가속모터의 성능 검증을 위해 환경 시험을 수행하였다. 장기 저장용 모터 2기를 선정하여 진동, 충격, 온도 충격 시험을 통해 가속모터에 극한의 환경 조건을 가했다. 환경 시험 후, 비파괴 검사와 지상 연소 시험을 통해 가속모터의 성능을 검증하였으며, 최소 추력, 작동 시간, 점화 지연 시점에 대한 체계 요구 조건을 달성하였다. Environmental tests were carried out to verify the performance of the Korea Space Launch Vehicle Ullage Motor. Two long-term storage motors were selected. Extreme environmental conditions were applied to Ullage Motor through vibration, shock and temperature shock tests. After environmental testing, the performance of the Ullage Motor was verified by non-destructive testing, and ground combustion testing. System requirements for minimum thrust, operating time, and ignition latency were achieved.
오지성(Jisung Oh),이관주(Gwan Joo Lee),김수정(Sujeong Kim),김한준(Hanjoon Kim),박의용(Euiyong Park),권혁호(Hyukho Kwon),조인현(In-Hyun Cho) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5
KSLV-II 가속모터는 한국형발사체에 사용하는 단분리모터의 한 종류이며 역추진모터와 동시에 작동하여 단분리를 수행한다. 가속모터의 목표 성능에 맞는 내탄도 설계, 추진제 조성 적용, 연소관 및 경사형 노즐 설계를 수행하였다. 연소관 및 노즐의 소재로 티타늄 합금을 적용하였으며 알루미늄이 다량 함유된 추진제에 대한 내열 성능 확보를 위한 노즐 내열재 소재를 선정하였다. 지상연소시험을 수행하여 KSLV-II 요구조건에 맞는 가속모터의 연소 성능을 확보하였다. KSLV-II ullage motor is a type of the separation motor of Korea Space Launch Vehicle. Simultaneously operates with the retro Motor to perform the stage separation. The internal ballistics design, application of propellant composition, and the design of the combustion chamber and the canted nozzle were performed in accordance with the target performance of the ullage motor. Ti-6Al-4V alloy was applied to the combustion as material of chamber and nozzle. The heat resistant material of the nozzle was selected to ensure the heat resistance of the propellant containing a large amount of aluminum. And the combustion performance of the ullage motor satisfying the KSLV-II requirements was secured by performing the ground combustion test.
오지성(Jisung Oh),최지용(Jiyong Choi),박의용(Euiyong Park),조인현(Inhyun Cho) 한국추진공학회 2021 한국추진공학회 학술대회논문집 Vol.2021 No.5
한국형발사체 역추진모터의 성능 검증을 위해 환경 시험을 수행하였다. 장기 저장용 모터 2기를 선정하여 진동, 충격, 온도 충격 시험을 통해 역추진모터에 극한의 환경 조건을 가했다. 환경 시험 후, 비파괴 검사와 지상 연소 시험을 통해 역추진모터의 성능을 검증하였으며, 평균 추력, 작동 시간, 점화 지연 시점에 대한 체계 요구 조건을 달성하였다. Environmental tests were carried out to verify the performance of the Korea Space Launch Vehicle Retro Motor. Two long-term storage motors were selected. Extreme environmental conditions were applied to Retro Motor through vibration, shock and temperature shock tests. After environmental testing, the performance of the Retro Motor was verified by non-destructive testing, and ground combustion testing. System requirements for average thrust, operating time, and ignition latency were achieved.
Jisung Yoo,Won‑Mi Choi,Seok Su Sohn,Byeong‑Joo Lee,Gi‑Yong Kim,Hyungjun Kim,Won‑Doo Choi,Yong‑Jun Oh,Sunghak Lee 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
For maintaining high-performance turbo-charger housings at higher exhaust-gas temperatures, e.g., 1050 °C, a high-Ni(20 wt%)-containing austenitic steel (ASTM HK40 steel) has been actively modified. As a promising method, the solidsolutionhardening obtained from the V or Cu addition was utilized in this study. Five austenitic cast steels were made byadding V or Cu in the modified HK40 steel (N16 steel; 4%-Ni replacement by 4.6%-Mn), and the high-temperature propertyimprovement was explained by detailed microstructural evolutions coupled with thermodynamically calculated phase diagrams. The V- or Cu-added steels showed improvements in high-temperature properties over the N16 steel because the additionof V or Cu raised both austenite matrix hardness and volume fraction of M7C3carbide. Considering that only 3.6–4.8vol% of M7C3was present in the five austenitic cast steels, the strengths were affected more by the matrix hardness. Whenthe V or Cu content was quite high, however, the ferrite or Cu-coring is formed, thereby leading to the serious deteriorationof high-temperature properties. The V- or Cu-added steels within proper contents are applicable well to automotive turbochargerhousings requiring or emphasizing high-temperature tensile properties.
Jisung Yoo,Won‑Mi Choi,Byeong‑Joo Lee,Gi‑Yong Kim,Hyungjun Kim,Won‑Doo Choi,Yong‑Jun Oh,Sunghak Lee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10
In order to increase the exhaust-gas temperature of austenitic stainless cast steels used for turbo-charger-housings up to1050 °C, the more excellent high-temperature strength should be obtained because it works for keeping a sustainability ofthe housing shape. Three austenitic stainless cast steels were fabricated in this study by adding Nb into the Ni/Mn-replacedconventional ASTM HK40 steel, and their high-temperature strength was investigated in relation with the carbide formationand matrix strengthening. The 1-wt%-Nb-added steel showed the enhancement in high-temperature strength over thenon-Nb-added steel. This indicated that the Nb addition was effective on the strength improvement because it raised boththe fraction of thermally-stable hard MC-type carbides and the austenite-matrix hardness. However, the 1.5-wt%-Nb-addedsteel showed the lower high-temperature strength than the 1-wt%-Nb-added steel, although it contained the more MC carbides. The more MC carbides reduced the matrix hardness, enlarged the hardness difference between carbides and matrix,and deteriorated the high-temperature strength. Our results demonstrate that the strengthened matrix as well as populatedcarbides due to the Nb addition are desirable for further improving the high-temperature strength.
Yisok Oh,Jisung Geba Chang,Maxim Shoshany 한국전자파학회JEES 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.2
The first-order vector radiative transfer model (FVRTM) is modified mainly by examining the effects of leaf curvature of vegetation canopies, the higher-order multiple scattering among vegetation scattering particles, and the underlying-surface roughness for forward reflection on radar backscattering from farming fields at C- and X-bands. At first, we collected the backscattering coefficients measured by scatterometers and space-borne synthetic aperture radar (SAR), field-measured ground-truth data sets, and theoretical scattering models for radar backscattering from vegetation fields at microwaves. Then, these effects on the RTM were examined using the database at the C- and X-bands. Finally, an improved RTM was obtained by adjusting its parameters, mainly related with the leaf curvature, the higher-order multiple scattering, and the underlying-surface small-roughness characteristics, and its accuracy was verified by comparisons between the improved RTM and measurement data sets.