• Laser Solutions
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• v.7 no.1
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• pp.29-36
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• 2004

The dynamics of laser-induced plasma/shock wave and the interaction with a surface in the laser shock cleaning process are analyzed by optical diagnostics. Shock wave is generated by a Q-switched Nd:YAG laser in air or with N$_2$, Ar, and He injection into the focal spot. The shock speed is measured by monitoring the photoacoustic probe-beam deflection signal under different conditions. In addition, nanosecond time-resolved images of shock wave propagation and interaction with the substrate are obtained by the laser-flash shadowgraphy. The results reveal the effect of various operation parameters of the laser shock cleaning process on shock wave intensity, energy-conversion efficiency, and flow characteristics. Discussions are made on the cleaning mechanisms based on the experimental observations.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.339-339
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• 2011

진공 플라즈마와 달리 개방된 공간에서 방전되는 대기압 플라즈마는 진공상태에서 수행되는 에칭, 증착 등의 복잡한 플라즈마 공정을 경제적이고 신속하게 수행할 수 있어, 최근 들어 연구가 활발히 진행 중이다. 이와 관련하여 He, Ar, $N_2$, $O_2$, Air 등의 여러 종류의 기체를 50 kHz 고전압에서 방전하여 대기 중에서 저온 플라즈마 공정이 가능한 아크젯 타입의 플라즈마 소스를 개발하였다. 개발된 플라즈마 소스에서는 입력전압, 기체유량, 노즐의 구조와 크기 등의 여러 운전변수에 따라 플라즈마의 방전특성이 변화되었다. 특히 본 연구에서는 아크젯의 플라즈마 발생부의 물질성분(SUS, Aluminum, Cupper)에 따른 플라즈마의 기체온도 및 전자여기 온도의 변화를 광방출분광법(OES)를 이용한 Synthetic spectrum method와 Boltzmann plot method을 통해 살펴보았다. 전압-전류 특성곡선, 시간분해 이미지 촬영법, 기체온도 측정법 등을 이용하여 발생된 플라즈마의 물리적인 특성을 분석하였다. 특히 물질의 성분에 따라 발생되는 플라즈마의 기체 및 전자여기 온도가 이차 전자 방출계수 및 물질의 전도도와의 상관관계가 있는지 연구가 진행 중이다.

• Horticultural Science & Technology
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• v.32 no.3
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• pp.346-352
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• 2014

This research was carried out to investigate the effect of supplemental lighting on stable productivity of paprika (Capsicum annuum L.) during low radiation period of winter season. The supplemental lighting sources used in this research were high pressure sodium (HPS) and lighting emitting plasma (LEP). Photosynthetic photon flux density (PPFD) emitted from both lamps decreased as vertical distance from lamp increased. The PPFD of LEP lamps were twice more than that of the HPS lamp per unit distance, but the rate of decreased PPFD of t he LEP per unit distance was higher than that of HPS lamp. And different degrees of PPFD between HPS and LEP lamps by horizontal distance had a smaller degree of difference than by vertical distance at the 100 cm away point. As daily average PPFD measured at the top of the plant under the supplemental lighting during January, the supplemental lighting significantly increased radiation. Radiation of HPS and LEP lighting was 137% and 315% higher than control (without supplemental lighting = sunlight). Air temperature in the top of the plant was not significant different among treatments. HPS and LEP lighting had no effect on increase of flower settings. Leaf length and width with LEP lighting was the longest, photosynthetic was higher than those of other treatments. Supplemental lighting treatments significant increased fruit length and diameter. Especially LEP lighting treatment had a greater effect on fruit length and diameter. In conclusion, LEP lighting treatment during low radiation period greatly affected growth and production of paprika. Further research will be required for the suitable application of LEP lighting in paprika production.