• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.138-138
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• 2003

광대역 LiNbO$_3$ 광변조기의 초고속 광 변조 구현을 위해서는 RF/ optical 속도 정합 및 임피던스 매칭 조건 하에서 낮은 구동전압을 얻을 수 있는 ridge 구조의 제작이 필수적이며 이런 구조 제작하기 위해서는 식각 속도와 식각면 거칠기 식각 profile 및 식각 과정에서의 반응물의 감소 등과 같은 개선을 위한 연구가 필요하다. 본 연구에서는 LiNbO$_3$ 기판 위에 메탈 마스크를 형성한 후 비등방성 (anisotropic) 건식 식각 방법인 NLD (Neutral Loop Discharge)로 플라즈마 식각을 하였다. NLD plasma 식각은 1Pa 이하의 압력에서 낮은 전자 온도를 갖는 고밀도 플라즈마를 생성하고 이온 플라즈마를 형성하여 LiNbO$_3$ 표면의 원자와 분자를 이온충돌효과를 이용하여 물리적인 식각과 discharge로 형성된 레디칼 (radical)과의 상호작용에 의한 화학적 식각 메커니즘에 의한 방법으로 plasma에 의한 시편의 손상이 적으며 식각 속도가 또한 높은 것이 특징이다. 본 논문에서는 안테나 파워와 가스의 유량에 따른 LiNbO$_3$ 식각 profile 특성에 관하여 연구 하고자 한다.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.316-323
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• 1995

A vital step in magnetic tape manufacturing is the surface modification of polymer substrate prior to ink application. A critical element for good adhesion of magnetic ink on polymeric substrate is the ability to join ink in cost-effective manner. Corona discharging is one of the effective methods of modifying polymer surface to improve adhesion while maintaining the desirable properties of the film itself. Surface treatment by corona which is exposure of film surface to electron or ion bombardment, rather than mere exposure to active species, like atomic oxygen or ozone, can enhance adhesion by removing contaminant, electret, roughening surface, and/or introducing reactive chemical groups. Reactive neutrals, ions, electron and photons generated during the corona treatment interact simultaneously with polymers to alter surface chemical composition, wettability, and thus film adhesion. However, it is highly recommended that extensive chains scission be avoided because it can lead to side-effect by forming sticky matter, resulting in dropouts. This paper reviews principles of surface preparation of polymer substrate by corona discharging. In addition, the experimental section provides a description of parameter optimization on corona discharging treatment and its side-effect. Experimental results are discussed in terms of surface wetting as determined by contact angle measurements.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.839-845
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• 2011

We performed numerical simulations of freely propagating premixed flames at atmospheric pressure to investigate the influence of trifluoromethane on $CH_4/O_2/N_2$ flames under oxygen enrichment. Trifluoromethane significantly contributed toward a reduction in flame speed, the magnitude of which was larger in terms of the physical effect than the chemical effect. More trifluoromethane could be added and consumed on oxygen-enriched $CH_4/O_2/N_2$ flames. $CHF_3$ was decomposed primarily via $CF_3{\rightarrow}CF_2{\rightarrow}CF{\rightarrow}CF:O{\rightarrow}CO$ and $CHF_3+M{\rightarrow}CF_2+HF+M$ played an important role in oxygen-enhanced flames. When an inhibitor was added to oxygen-enriched flames, the position of the maximum concentration of active radicals was shifted to a relatively low temperature range, and the net rate of OH became higher than that of H.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.4
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• pp.447-452
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• 2007

This experiment was conducted to enhance the colored potatoes utilization and to determine the biological activity of colored potato extracts. In order to understand the factors responsible for the potent antioxidant and antihypertensive ability of colored potatoes, it has been evaluated for anti-oxidative activity using Fenton's reagent/ethyl linoleate system and for free radical scavenging activity using the 1,1-diphenyl-2-picryl hydrazyl free radical generating system. There were significant differences of antioxidant activities in $50{\mu}g/mL$ extracts treatment among different colored potatoes. About two-fold higher radical scavenging activity was found in 'Daegwan 1-102', 'Daegwan 1-104' and 'Jasim' compared to that in 'Superior'. Based on the flesh color tested, potatoes with purple tuber showed higher radical scavenging activity than red potatoes, while white potato showed the lowest radical scavenging activity. The ability of 80% ethanol extracts from colored potatoes to influence the inhibitory activity of angiotensin converting enzyme(ACE) and xanthine oxidase(XOase) has also been investigated. Expect 'Jasim', the high levels of inhibition activity of xanthine oxidase in two colored potatoes such as 'Daegwan 1-102' and 'Daegwan 1-104' were highly correlated to $IC_{50}$ values of ACE inhibition activity. The various therapeutic benefit claims in the new functional medicinal usage of colored potatoes ascribed to the phenolic compounds and anthocyanin. This result revealed that the extracts of colored potatoes are expected to be good candidate for development into source of free radical scavengers and anti-hypertentive agent.

• Journal of Life Science
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• v.19 no.11
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• pp.1629-1636
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• 2009

Pine trees (Pinus densiflora Sieb. et Zacc.) have been used as a traditional health-promoting medicinal food in Korea. This research was performed to determine the antioxidative and antibacterial activities, tyrosinase, nitric oxide synthesis, angiotensin converting enzyme (ACE), and xanthine oxidase inhibition effects of the pine bud ethanol extract (PBE). Antioxidative activities of PBE were measured by using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical scavenging activity and superoxide dismutase-like activity (SODA). DPPH radical scavenging and SOD-like activities of PBE were remarkably increased in a dose-dependent manner, and were about 88.9% and 47.9% at 1 mg/ml and 10 mg/ml, respectively. The xanthine oxidase and angiotensin converting enzyme activities were inhibited about 71.9% and 60.8% at 1 mg/ml and $100{\mu}g/ml$ of PBE, respectively. The tyrosinase inhibitory activities of PBE were slightly increased in a dose-dependent manner. The PBE showed strong antimicrobial activities on Escherichia coli (E. coli) and Vibrio paraheamolyticus. Stimulation of the macrophages RAW264.7 cells with lipopolysaccharide (LPS) resulted in increased production of nitric oxide (NO) in the medium. However, NO synthesis was reduced up to 54% by addition of PBE at $200{\mu}g/ml$. These results revealed that pine buds have a strong antioxidative and anti-inflammatory activity, and exhibit angiotensin converting enzyme and xanthine oxidase inhibitory activities. This suggests that pine buds have the greatest property as a source for natural health products.