• Korean Journal of Plant Resources
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• v.24 no.4
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• pp.343-350
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• 2011

A medicinal herb, Stevia rebaudiana Bertoni which is grown under physical stresses such as simulated microgravity, shaking, and low temperature for 4 days, showed fresh weight decrease of 3.6%, 21% and 8.7% compared with the respective control. On control plants, the radical scavenging value of DPPH represented 86% and 55%, respectively in the leaves and stems extracts. Relatively weak antioxidant activities of 22% and 27% were measured respectively in AA (ascorbic acid) and BHA (beta-hydroxyacetic acid) known as synthetic antioxidants. The radical scavenging effect of DPPH (2,2-diphenyl-1-picryl hydazal) in stevia plants under a simulated microgravity was observed to be consistently higher relative to the control, whereas those effects of shaking and low temperature treatments rapidly increased and then reduced after 6 hours in case of shaking process and 24 hours in case of low temperature treatment, which results had similar levels of scavenging effects to the control. The plants under simulated microgravity showed the highest level of activity with the value of 147% and the shaking and low temperature treatments showed the increases of SOD activity by 121% and 125%, respectively. From the above results, it is clarified that the simulated microgravity is more effective to the antioxidant activity than those of other abiotic stresses.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.3
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• pp.185-190
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• 1987

In order to study the preservation effect of $-3^{\circ}C$ partial freezing method, tile growth and biochemical activity of microorganisms and the changes of K-value in mackerel press juice were investigated at $0^{\circ}C,\;-3^{\circ}C$ supercooling (liquid phase) and $-3^{\circ}C$ freezing (solid phase). The results obtained in this paper were follows : 1) The growth and biochemical activity of microorganisms were reduced at $-3^{\circ}C$ supercooling than $0^{\circ}C$ in spite of the small variation in temperature. 2) There were no growth and biochemical activity of microorganisms at $-3^{\circ}C$ freezing (solid phase). 3) The difference in the K-value between $-3^{\circ}C$ supercooling and $-3^{\circ}C$ freezing was remarkable in spite of the same temperature.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.391-399
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• 2023

Recently, low-temperature pyrolysis technology has been studied as a recycling method for waste plastic. Low-temperature pyrolysis technology for waste plastic produces pyrolysis oil that can be used as an energy resource, but solid residue remains. Waste plastic pyrolysis residues are mostly landfilled due to their limited use. In this study, it is investigated that mixed waste plastic pyrolysis residues could be recycled into activated carbon. It was confirmed that the fixed carbon content of the residue was 33.69 % from proximate Analysis. Chemical activation was used to manufacture activated carbon. KOH was used as an activator. To investigate the effect of the mixing ratio of KOH and residue, samples were mixed at ratios of 0.5, 1.0, and 2.0. The mixed sample was chemically activated at an activation temperature of 800 ℃ for 1 hour. As a result of analyzing the characteristics of activated carbon through BET, it was confirmed that the specific surface area increased as the mixing ratio of KOH increased.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.251-262
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• 2022

We selected a cold-tolerant tea tree (Camellia sinensis L.) through reliable evaluation using a number of cold-tolerance indicators targeting tea tree cultivars such as "Chamnok," "Bohyang," "Sangnok," and "Myungnok" in response to climate change. We conducted a low-temperature damage investigation, "Chamnok" and "Bohyang" were damaged investigated with small amounts of green and bright green. "Sangnok" and "Myungnok" were damaged investigated red and dark red at -10℃. The extent of electrolyte leakage increased as the treatment temperature decreased in all cultivars. We predicted lethal temperatures through non-linear regression analysis, finding relatively higher tolerance to low temperature in "Chamnok" (-9.344℃) and "Bohyang" (- 8.883℃) than that in "Myungnok" (-8.092 ℃) and"Sangnok" (-7.632℃). "Bohyang" showed higher levels of antioxidant activity compared to other cultivars. The lipid peroxidation reaction revealed that "Sangnok" and "Myungnok" had higher MDA content than that of other cultivars when treated at low temperatures. Consequently, predictions of the lethal temperature through non-linear regression analysis of "Chamnok" and "Bohyang" were consistent with their tolerance to low-temperature damage, and antioxidant activity and lipid peroxidation reactions were likewise consistent. The results of this study can be used not only for evaluation and selection of cold-tolerance of tea trees in response to climate change, but also in the cultivation of cold-tolerant plants.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1264-1276
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• 2000

Light-off catalyst has been used for minimization of cold-start emissions. Improved cold-start performance of light-off catalyst needs the optimal design in terms of flow distribution, geometric surface area, precious metal loading, cell density and space velocity. In this study, these influential factors are numerically investigated using integrated numerical technique by considering not only 3-D fluid flow but also heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading of depositing high active catalyst at upstream of monolith is beneficial during warm-up period but its effect is severely deteriorated when the space velocity is above 100,000 $hr^{-1}$ To maximize light-off performance, this study suggests that 1) a light-off catalyst be designed double substrate type; 2) the substrate with high GSA and high PM loading at face be placed at the front monolith; and 3) the cell density of the rear monolith be lower to reduce the pressure drop.

• Korean Journal of Medicinal Crop Science
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• v.1 no.1
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• pp.49-57
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• 1993

Seedling of Aralia continentalis is more effective method rather than use of vegetative organ for mass propagation. However, lower germination rate is the main problem for seeding. In this study, we analyzed substances in aim to relate to germination process. The results indicated that longer period of stratification brought lower amount of phenolic compounds in the seeds and both promoting and inhibiting substances were at very low level or gradually disappeared.

• Food Science and Preservation
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• v.19 no.2
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• pp.178-184
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• 2012

The physiochemical property, nutrient composition, and functionality of apple juice sterilized at a low temperature (LT, $70^{\circ}C$, 30 min) or a high temperature (HT, $100^{\circ}C$, 20 min) were analyzed. The pH of the apple juice that was sterilized at LT (pH 4.72) was higher than that of the apple juice that was sterilized at HT (pH 4.57), and the acidity of the apple juice that was sterilized at HT (8.90%) was higher than that of the other sample. The sugar content of the two apple juice samples was 15 $^{\circ}Brix$, and the apple juice samples had high potassium, malic acid, and glutamic acid contents. The total polyphenol contents of the apple juice samples that were sterilized at LT and HT were 27.39 mg/100 mL and 23.24 mg/100 mL, respectively. The apple juice that was sterilized at LT had a significantly stronger DPPH radical scavenging activity than the apple juice that was sterilized at HT ($p$ <0.01), and the apple juice that was sterilized at LT had a lower hydroxyl radical scavenging activity level than the other apple juice. Finally, the apple juice that was sterilized at LT showed significantly stronger activities that inhibit enzyme-related oxidation than the apple juice that was sterilized at HT ($p$ <0.05).

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.204-204
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• 2016

다양한 형태의 대기압 저온 플라즈마 장치를 개발하고 특성을 연구하였다. 최근 대기압 저온 플라즈마를 의료 및 미용 분야에 적용하기 위한 연구가 활발하게 진행되고 있다. 본 연구에서는 대기압 플라즈마 장치의 생체 적용을 위해 전기적, 열적 피해가 없는 플라즈마 발생 장치를 개발하였다. 대기압 플라즈마 발생 장치는 크게 플라즈마 제트와 유전 격벽 방전(DBD) 플라즈마의 형태로 나눌 수 있다. 대기압 플라즈마 제트는 고압 전극의 역할을 하는 주사 바늘과 바늘을 감싸고 있는 유리관, 유리관의 외부에 위치하는 접지 전극의 구조로 되어 있다. 방전 기체는 방전이 용이한 불활성 가스가 주로 사용되지만, 필요에 따라 $N_2$나 Air같이 방전이 어려운 분자 및 혼합 기체도 사용 한다. 방전 기체에 따라 대기압 플라즈마 제트의 전극 구조를 다르게 적용하였으며, 각 구조에서의 플라즈마 방전 특성을 연구 하였다. 유전 격벽 방전 플라즈마 장치는 고압 전극과 접지 전극 사이에 유전체가 위치하는 구조이다. 방전 가스를 불어주지 않아도 대기중에서 방전이 가능하고, 구조가 간단하여 용도에 맞는 다양한 형태로 방전이 가능하다. 이러한 대기압 저온 플라즈마의 특성 연구를 바탕으로 전기적, 열적 피해가 없으며 사용자 편의성을 갖춘 다양한 형태의 대기압 플라즈마 장치를 개발 하였다. 본 연구를 통하여 대기압 저온 플라즈마 발생 장치의 개발과 활용 연구에 도움이 될 것으로 기대한다.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.317-322
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• 2005

[ $Pt/CeO_2$ ] 촉매에 Zr을 첨가하여 우수한 저온 수성가스전화반응의 활성을 가진 촉매를 만들었다. $Pt/ZrO_2-CeO_2$ 촉매는 $Pt/ZrO_2$나 $Pt/CeO_2$ 촉매에 비해 Ce와 Zr의 상호작용에 의한 시너지 효과로 인해 CO chemisorption으로 측정한 Pt area가 증가하고 담체에 Pt가 잘 분산되었다. 또한, Zr이 첨가된 $Pt/CeO_2$는 Ce의 redox 능력을 향상시켜 support의 reducibility를 향상시켰다. 담체에 고르게 잘 분산되고 support의 산소저장능력과 reducibility가 향상된 $3\;wt\%\;Pt/ZrO_2-CeO_2$ 촉매들은 반응물에 수소와 이산화탄소의 첨가 유무와 상관없이 $3\;wt\%\;Pt/ZrO_2$나 $3\;wt\%\;Pt/CeO_2$ 촉매보다 우수한 활성을 보였다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.207-209
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• 2005

현재 고정원에서 상용화 촉매로서 사용되는 V$_{2}$O$_{5}$/TiO$_{2}$계 촉매는 고온 영역에서 최적 활성반응을 보이나 NH$_{3}$의 산화반응으로 인해 NO$_{X}$의 제거효율을 낮추는 원인과 가열설비의 추가적인 설치에 따른 초기 투자비, 운전비용 상승 및 촉매 수명 단축 등의 경제적, 기술적인 문제점을 나타내고 있다. 본 연구에서는 저온 영역에서 높은 활성반응을 나타내는 촉매기술의 SCR적용시 배출가스 온도의 100$^{\circ}C$ 감소에 따른 동력비의 절감과 촉매 수명 연장, 경제적, 기술적인 문제점을 해결할 수 있을 것으로 사료된다.