• Proceedings of the Korean Environmental Sciences Society Conference
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• 2000.05a
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• pp.206-207
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• 2000

고분자 담체의 경우 표면의 화학적 성질인 소수성과 물리적 성질인 표면거칠기는 미생물 부착과 관련이 있지만 두 요소 중, 표면거칠기의 영향이 더 크다고 볼 수 있으며 담체 표면의 소수성이 작고 표면거칠기가 클수록 혐기성 미생물이 잘 부착되었다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.1
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• pp.52-59
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• 2011

가계가공은 절삭 부위의 냉각작용과 윤활작용을 위해 절삭유를 많이 소모한다. 절삭유는 염소계의 극압첨가제 등이 함유되어 있어 작업자들에게 유독할 뿐만 아니라 대기의 오염을 초래하여 청정생산을 저해하게 되므로 이런 전통적인 방법은 작업자의 직업병으로부터 보호와 환경보호를 위하여 새로운 가공방법으로 변경되어야만 한다. MQL 기계가공 방법은 절삭유를 아주 소량 소모하므로 청정생산을 위한 대안으로 떠오르고 있지만 많은 작업자들이 이에 대한 기술적인 확신이 부족하여 이 방식의 사용을 주저하고 있다. 본 연구는 MQL 가공 방식에서 가공의 특성을 파악하여 표면거칠기에 영향을 미치는 인자와 범위를 찾고자 다양한 실험을 계획하고 그 결과를 분석하였다. 실험의 계획에서는 각 가공의 특성을 잘 나타낼 수 있는 인자와 수준을 선정하고, 다양한 상황의 결과를 분석하여 MQL 가공의 특성과 최적의 가공조건을 도출하였다. 본 연구의 실험 및 분석의 결과로서, 절삭 파라미터와 그의 수준이 가공특성을 잘 반영할 수 있도록 적절히 선택된다면 MQL 기계가공은 표면거칠기 향상 및 원가절감이나 환경보호 측면에서 절삭유 윤활방식을 대체하는 green manufacturing을 위한 대안이 될 수 있음을 보였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.2
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• pp.85-91
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• 2006

This study deals with the flow over a flat plate with repeated roughness elements of 2-dimensional rectangular shape, which can be applied into the study on the natural geographical roughness and the turbulent flow on roughened solid surface. Part 1 of the study showed that the ratio between the spacing and the height of roughness elements plays a crucial role in developing the flow pattern near wall surface. The present study complements the turbulence characteristics, the utilization of friction velocity as well as integral parameters. Results confirmed that k-type roughness(s/H=7 or 14) is certainly a more effective means than d-type roughness (s/H=3.5) in thickening the viscous region.

• The korean journal of orthodontics
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• v.36 no.5
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• pp.360-368
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• 2006

Objective: Surface characteristics of dental materials play an important role in bacterial adhesion. The purpose of this study was to investigate surface characteristics of 5 different light-cured orthodontic adhesives (1 fluoride-releasing composite, 3 non-fluoride-releasing composites, and f resin-modified glass ionomer). Methods: Surface roughness was measured using a confocal laser scanning microscope. Contact angle and surface free energy components were analyzed using the sessile drop method. Results: Surface roughness was significantly different between adhesives despite a relatively small variation (less than $0.05\;{\mu}m$). Lightbond and Monolok2 were rougher than Enlight and Transbond XT. There were also significant differences in contact angles and surface free energy components between adhesives. In particular, considerable differences in contact angles and surface free energy components were found between resin modified glass ionomer and the composites. Resin modified glass ionomer showed significantly smaller contact angles in 3 different probe liquids and had higher total surface free energy and stronger polarity, with notably stronger basic property than the composites. Conclusion: Resin modified glass ionomer may provide a more favourable environment for bacterial adhesion than composite adhesives.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.269-272
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• 2003

하천에 토사가 유입되는 가장 중요한 요인은 주변 지역의 사면에서의 토양의 침식작용이며 이러한 현상은 다양한 요인들에 의해 영향 (사면경사, 사면식생, 토양 입도, 사면거칠기 등)을 받지만 주로 물, 특히 강우에 의해 크게 좌우된다. 그러므로 정확한 강의 양과 강우 강도, 이에 따른 토양의 침식량을 정량화하는 것이 중요하다. 이번 연구에서는 이러한 다양한 조건에 따라 토양의 침식이 어떠한 특성을 갖고 발생하는지를 파악하고자 하였다. (중략)

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.2
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• pp.79-84
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• 2006

The present study deals with the flow over a flat plate with repeated roughness elements of 2-dimensional rectangular shape, which can be applied into the study on the natural geographical roughness and the turbulent flow on roughened solid surface. Experiment was performed using PIV technique in the circulating water channel. Results showed that the flow over roughness elements was characterized by the high shear flow emanating from top of roughness element and the recirculating region formed at the trough of two roughness elements. In general, the ratio between the spacing and the height of roughness elements plays a crucial role in developing the flow pattern near wall surface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.865-870
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• 2001

In this paper, we analyse the effect of phase noise from PLL frequency synthesizer on 64 QAM when detecting corrupted signals. To predict the phase noise of an oscillator very accurately, we assume that the oscillator is linearly time-varying when the input impulsive current to the oscillator is small. The performance of the detector which detects the corrupted signal by oscillator phase noise is compared with that when the detector is only affected by AWGN and then analyse how much the phase noise degrades the system performance for 64 QAM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.217-221
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• 2000

In this paper, we analyze the effect of phase noise from PLL frequency synthesizer on 64QAM when detecting the corrupted signals. To predict the phase noise of oscillator very accurately, we considered that oscillator has the linearly time-varying nature when the input impulsive torrent to oscillator is small. The performance which detects the corrupted signal by oscillator phase noise is compared with only affected by AWCN and then analyze how much it degrade system performance for 64QAM.

• Journal of the Korean Society for Railway
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• v.7 no.1
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• pp.14-19
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• 2004

The effect of surface damage on fatigue properties of catenary wires were investigated to estimate their service lift. As surface defects of the wires caused by surface corrosion increase, surface roughness gets worse, and as roughness increases, it is easy for moisture coming from rain and dew to be condensed around uneven parts of the surface. The condensed moisture causes a locally severe corrosion which leads to damage of the wires. Corrosion of catenaty wires can make their actual lifetime shorter than that originally designed. The amount of decrease was more prominent as environmental conditions became more corrosive. They are also vibrated with some amplitude everytime pantographs touch contact line. The frequent cyclic load on the wire may result in a fatigue fracture. Surface damage by corrosion can make formation of crack initiation at fatigue. In the present study, the fatigue life of the used wire was measured 35 to 50% compared with that of new one in average.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.22-27
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• 2004

Recently, environmental pollution has become a significant problem in industry and many researchers have investigated in order to preserve the environment. Environmentally conscious machining and technology have more important position in machining process, because cutting fluid has bad influence on the environment in milling process. This research is the experimental study on high speed machining of aluminum alloys through environmentally conscious machining. In this study, the surface roughness and chip appearance was investigated in the machining of aluminum alloys by dry machining, using cutting fluid and oil mist.