• Journal of Photoscience
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• 제12권1호
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• pp.33-39
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• 2005

Plants possess the ability to dissipate the excitation energy for the protection of photosynthetic apparatus from absorbed excess light. Heat dissipation is regulated by xanthophyll cycle in thylakoid membranes of chloroplasts. We investigated the mechanistic aspects of xanthophyll cycle-dependent photoprotection against low-temperature photoinhibition in plants. Using barley and rice as chilling-resistant species and sensitive ones, respectively, chilling-induced chlorophyll fluorescence quenching, composition of xanthophyll cycle pigments and mRNA expression of the zeaxanthin epoxidase were examined. Chilled barley plants exhibited little changes in chlorophyll fluorescence quenching either of photochemical or non-photochemical nature and in the photosynthetic electron transport, indicating low reduction state of PS II primary electron acceptor. In contrast to the barley, chilled rice showed a marked decline in those parameters mentioned above, indicating the increased reduction state of PS II primary electron acceptor. In addition, barley plants were shown to have a higher capacity to elevate the pool size of xanthophyll cycle pigments in response to cold stress compared to rice plants. Such species-dependent regulation of xanthophyll cycle activity was correlated with the gene expression level of cold-induced zeaxanthin epoxidase. Chilled rice plants depressed the gene expression of zeaxanthin epoxidase, whereas barley increased its expression in response to cold stress. We suggest that chilling-induced alterations in the pool size of xanthophyll cycle pigments related to its capacity would play an important role in regulating plant's sensitivity to chilling stress.

• 품질경영학회지
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• 제47권3호
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• pp.437-451
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• 2019

Purpose: The purpose of this study is to improve the quality of the PGM system by improving the structure and production process of slip-ring rotary joint for radar. Methods: The improvement measures for each cause are established through failure analysis of broken items. Specifically, changing in the housing to improve the heating system. Changing the transportation method to prevent damage to equipment during transport. Changing work process of the attenuator ring to prevent damage. etc. Results: The results of this study are as follows; improving the heating system reduces heat generated by the attenuator by about 7 degrees and obtain additional temperature margins. Reduction of defect rate because of adding X-band rotary joint run-out measurement test, ESS of slip-ring rotary joint and Transportation improvement(reinforced flight boxes, tube protection, etc). Getting stable VSWR values by improving work process of attenuator overheating due to a bad bonding process. Conclusion: Through this study, improvements were made to slip-ring rotary joint that failed repeatedly for various reasons. As a result of the application of the improvements, the same fault does not occur until now, so we can see that the quality of PGM has improved.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.344-349
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• 2018

본 논문은 의료용 시술에 사용되는 가이드 와이어의 테프론 코팅 장치의 주요 설계변수 설정방법에 대해 제안하였다. 제안된 장치는 가이드 와이어가 코팅 및 열처리 등을 연속적으로 수행하는 릴투릴(Reel to reel)방식으로 진행되도록 제작되었다. 이때 이송되는 가이드 와이어는 롤러 사이에서 진동을 하게 되고 이는 코팅 품질에 영향을 주게 된다. 따라서 본 논문에서는 길이방향으로 이송되는 가이드 와이어의 동역학 식을 제안하고 이를 바탕으로 이송 시 가이드 와이어의 진동 진폭이 최소화 될 수 있는 이송 속도 및 와이어를 지지하는 롤러의 간격을 설계하였다. 제안된 방법에 의해 제작된 코팅 장치를 바탕으로 의료용 가이드 와이어의 테프론 코팅을 진행하였다. 본 연구에서는 가이드 와이어의 코팅 두께 목표를 원주방향으로 $10{\mu}m$ 이내로 제작될 수 있도록 설정하였고 광학현미경을 사용하여 그 결과를 검토하였다.

• Korean Chemical Engineering Research
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• 제57권1호
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• pp.28-41
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• 2019

본 연구는 소듐냉각고속로 원형로 소듐-물 반응 압력완화계통의 성능 해석을 목적으로 한다. 증기발생기의 전열관 파단에 의한 대규모 물 누출 사고 발생 시, 증기발생기 전열관 내측의 물을 급수덤프탱크로 배출하고 전열관 외측의 소듐 및 반응생성물을 소듐덤프탱크로 배출 할 때 유체의 거동을 해석하여 계통 설계요건의 적절성을 평가하였다. 증기발생기 쉘 측의 액체와 중간열전달계통 내 소듐이 모두 배출되는데 소요되는 시간은 약 50초이고, 증기발생기 전열관 측의 급수가 모두 배출되는데 소요되는 시간은 약 2.5초로 계산되었다. 증기발생기와 중간열전달계통 내 유체가 덤프탱크로 배출되는 동안 전열관 측의 압력은 쉘 측의 압력보다 높게 유지되어 쉘 측의 소듐이 전열관 측으로 역류하는 현상은 없는 것으로 해석되었다. 본 연구의 결과는 SFR 원형로 소듐-물반응압력완화계통의 성능 평가에 대한 기초자료로 활용할 예정이다.

• 공업화학
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• 제32권4호
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• pp.442-448
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• 2021

고분자전해질 연료전지에서 분리판 유로 형상은 유체 공급과 물 및 열 확산, 접촉 저항 등에 영향을 주는 중요한 요소이다. 본 연구에서는 25 cm² 단위 전지를 이용하여 공기극에 구리폼을 적용한 분리판을 이용하여 연료전지 성능 평가를 수행하였다. 압력과 상대습도 조건에 대한 영향을 분극 곡선과 전기화학적 임피던스 분광법을 이용하여 분석하였다. 구리폼의 ohmic 저항이 높아 사형유로형상 보다 연료전지 성능은 낮았지만, 다공성 구조로 인한 균일한 연료 분포로 활성화 손실과 물질전달 손실이 적은 것을 확인하였다. 구리폼의 소수성이 높아 물 배출이 유리한 장점이 있지만, 저가습 조건에서는 사형유로에 비하여 전해질막 수화도가 낮은 것을 확인하였다. 다공성 금속 분리판은 균일한 압력 분포와 효과적인 수분 배출로 연료전지 성능을 개선할 수 있을 것으로 판단되며, 저항을 최소화할 수 있도록 금속폼의 물성에 대한 연구가 수행되어야 할 것이다.

• Current Photovoltaic Research
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• 제9권4호
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• pp.145-159
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• 2021

Light soaking (LS) stability in polymer solar cells (PSCs) has always been a challenge to achieve due to unstable photoactive layer-electrode interface. Especially, the electron transport layer (ETL) and photoactive layer interface limits the LS stability of PSCs. Herein, we have modified the most commonly used and robust zinc oxide (ZnO) ETL-interface using an organic dye molecule and a co-adsorbent. Power conversion efficiencies have been slightly improved but when these PSCs were subjected to long term LS stability chamber, equipped with heat and humidity (45℃ and 85% relative humidity), an outstanding stability in the case of ZnO/dye+co-adsorbent ETL containing devices have been achieved. The enhanced LS stability occurred due to the suppressed interfacial defects and robust contact between the ZnO and photoactive layer. Current density as well as fill factors have been retained after LS with the modified ETL as compared to un-modified ETL, owing to their higher charge collection efficiencies which originated from higher electron mobilities. Moreover, the existence of less traps (as observed from light intensity-open circuit voltage measurements and dark currents at -2V) are also found to be one of the reasons for enhanced LS stability in the current study. We conclude that the mitigation ETL-surface traps using an organic dye with a co-adsorbent is an effective and robust approach to enhance the LS stability in PSCs.

• BMB Reports
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• 제55권10호
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• pp.488-493
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• 2022

The specific pair of heat shock protein 70 (Hsp70) and Hsp40 constitutes an essential molecular chaperone system involved in numerous cellular processes, including the proper folding/refolding and transport of proteins. Hsp40 family members are characterized by the presence of a conserved J-domain (JD) that functions as a co-chaperone of Hsp70. Tumorous imaginal disc 1 (Tid1) is a tumor suppressor protein belonging to the DNAJA3 subfamily of Hsp40 and functions as a co-chaperone of the mitochondrial Hsp70, mortalin. In this work, we performed nuclear magnetic resonance spectroscopy to determine the solution structure of JD and its interaction with the glycine/phenylalanine-rich region (GF-motif) of human Tid1. Notably, Tid1-JD, whose conformation was consistent with that of the DNAJB1 JD, appeared to stably interact with its subsequent GF-motif region. Collectively with our sequence analysis, the present results demonstrate that the functional and regulatory mode of Tid1 resembles that of the DNAJB1 subfamily members rather than DNAJA1 or DNAJA2 subfamily proteins. Therefore, it is suggested that an allosteric interaction between mortalin and Tid1 is involved in the mitochondrial Hsp70/Hsp40 chaperone system.

• 신재생에너지
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• 제18권4호
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• pp.12-21
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• 2022

The pyrolysis characteristics of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) were analyzed numerically using a 1D plug flow reactor (PFR) model. A lumped kinetic model was selected to simplify the pyrolysis products as wax, oil, and gas. The simulation was performed in the 400-600℃ range, and the plastic pyrolysis and product generation characteristics with respect to time were compared at various temperatures. It was found that plastic pyrolysis accelerates rapidly as the temperature rises. The amounts of the pyrolysis products wax and oil increase and then decrease with time, whereas the amount of gas produced increases continuously. In LDPE pyrolysis, the pyrolysis time was longer than that observed for other plastics at a specified temperature, and the amount of wax generated was the greatest. The maximum mass fraction of oil was obtained in the order of HDPE, PP, and LDPE at a specified temperature, and it decreased with temperature. Although the 1D model adopted in this study has a limitation in that it does not include material transport and heat transfer phenomena, the qualitative results presented herein could provide base data regarding various types of plastic pyrolysis to predict the product characteristics. These results can in turn be used when designing pyrolysis reactors.

• 한국농공학회논문집
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• 제65권1호
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• pp.27-39
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• 2023

This study was to quantitatively evaluate periodic and maximum energy loads for broiler-standard design models by the Ministry of Agriculture, Food and Rural Affairs (2016). Building energy simulation method was used to compute heating and cooling loads of the designed broiler houses according to regional locations and insulation characteristics of wall and roof. It considered sensible and latent heat generation from broilers, dynamic operation of ventilation system according to environment variations. It was found that variation of periodic heating loads was relatively higher than that of periodic cooling loads according to thickness changes of wall and roof. Assuming that broiler was raised at every even-month, periodic heating and cooling loads were 6 and 18% lower, respectively than odd-month raising condition. When recommendation rules of insulation characteristics (wall and roof thickness) by the Ministry of Land, Infrastructure and Transport was adopted, periodic heating load of Jeju-si was 20.3% higher than national average values. Based on the BES computed periodic and maximum energy loads under the designed experimental condition, these results can contribute to reestablishing standard design of broiler houses, especially for insulation characteristics, and designing management strategies for efficient energy uses.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.49-55
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• 2023

This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.