• Journal of the Optical Society of Korea
• /
• 제16권1호
• /
• pp.13-16
• /
• 2012

We demonstrate an optical gate architecture using a single SOA to perform AND, OR and NOT logic functions. Simple reconfigurable all-optical logic operations are implemented using RZ modulated signals at 40 Gb/s. Contrast ratio and extinction ratio values have been analysed for the different types of logic gates. Maximum extinction ratio and contrast ratio achieved are 19dB and 17.2 dB respectively. Simple structure and potential for integration makes this architecture an interesting approach in photonic computing and optical signal processing.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
• /
• pp.143-145
• /
• 2015

A mesoscale channel was designed to observe the flame stabilization at low strain rate conditions (< $10s^{-1}$). At this condition, the behavior of partially premixed flame was explored by changing a channel size and the oxygen ratio in the oxidant. In this work, experiment is conducted for propane case and it was compared with methane case of previous one. Conclusively, it can be observed that the strain rate of flame extinction and starting point of oscillation were varied with oxygen ratio. Moreover we can understand the effects of enhanced oxygen ratio of oxidant and flame behavior at low strain rate conditions.

• 한국안전학회지
• /
• 제23권6호
• /
• pp.38-43
• /
• 2008

Significant portion of the fire accident is caused by some troubles in electric circuits. To prevent the fire induced by those electric trouble, some indications of electric fire need to be suitably detected at the first stage of the fire development. With this background, the characteristics of soot yielding of electric cables have been investigated using a light extinction method. In this study, a light scattering method was compared with the light extinction method. A slot-type premixed-flame combustor was traversed to bum three types of electric cables by compulsion, then the mass decrease rate and the soot densities were measured. According to the experimental results, the light scattering method is preferred to the light extinction method when the soot yield ratio is relatively small. Thus the former method is more suitable to detect the occurrence of an electric fire in a power distributer box.

• 대한기계학회논문집B
• /
• 제36권2호
• /
• pp.181-188
• /
• 2012

대향류확산화염의 화염소화에 있어서 에지화염 역할에 관한 실험적 연구가 진행되었다. 속도비, 버너직경, 그리고 버너간격을 변화시키며 수행된 실험에서 전체신장률에 따른 화염소화 임계질소몰분율의 그래프는 c-커브 형태로 나타났다. 고신장률화염에서는 화염소화 임계질소몰분율의 그래프가 하나의 곡선으로 일치하였으며, 화염이 일차원의 응답특성을 갖는 것을 확인하였다. 화염 소화는 바깥 에지화염이 반경방향으로의 진동 후에 화염 중심으로 수축하며 소화하는 영역, 진동 없이 화염중심으로 수축하며 소화하는 영역, 그리고 바깥 에지부분의 수축과 진동 없이 화염중심에 화염 구멍이 생기며 소화하는 영역으로 세 가지 모드로 나타났다. 화염 표면온도 측정과 에너지 방정식의 각항을 수치해석 한 결과를 토대로 에지화염부분에서의 반경방향 전도 열손실이 에지화염의 불안정을 야기한다는 것과 전도를 통한 열 공급뿐만 아니라 대류를 통한 열 공급도 바깥 에지화염의 안정화에 기여한다는 것을 보였다. 그리고 반경방향의 전도열손실이 수축하며 소화하는 메커니즘의 지배적인 역할을 함을 보였다.

• ETRI Journal
• /
• 제27권3호
• /
• pp.267-272
• /
• 2005

The transmission performance of optical labeling based on a combined frequency shift keying/amplitude shift keying (FSK/ASK) format is studied by numerical simulation. The simulation demonstrates that the bit-error ratio (BER) characteristic of an ASK signal is limited by the extinction ratio, received optical power, and dispersion, simultaneously. However, an FSK signal is mainly limited by the extinction ratio (ER) and received optical power when the peak spectrum, which is used to detect the FSK signal, is relatively narrow.

• 대한수학회논문집
• /
• 제21권4호
• /
• pp.701-717
• /
• 2006

The positive coexistence of a simple food chain model with ratio-dependent functional response and cross-diffusion is discussed. Especially, when a cross-diffusion is small enough, the existence of positive solutions of the system concerned can be expected. The extinction conditions for all three interacting species and for one or two of three species are studied. Moreover, when a cross-diffusion is sufficiently large, the extinction of prey species with cross-diffusion interaction to predator occurs. The method employed is the comparison argument for elliptic problem and fixed point theory in a positive cone on a Banach space.

• 한국광학회지
• /
• 제31권2호
• /
• pp.71-80
• /
• 2020

본 논문에서는 상용 카메라를 이용하여 미세먼지의 소산계수를 측정하기 위한 새로운 방법을 제안하였다. 하나의 주어진 영상에서 같은 방향에 놓인 동일한 종류의 물체에 대한 3개 이상의 화소점의 밝기를 이용하여 소산계수를 측정하였다. 계산에 사용하기 위해 선택된 화소에 해당하는 물체는 카메라와의 거리를 알고 있는 것으로 선택하였다. 카메라를 이용하여 측정한 미세먼지의 소산계수와의 비교를 위하여 라이다를 이용하여 소산계수를 측정하였다. 최종적으로 카메라를 이용하여 측정한 미세먼지의 소산계수와 라이다를 이용한 그것에는 신뢰할 수 있는 상관관계를 얻었으며, 약 0.86 정도의 값을 보였다. 같은 방법으로 카메라의 R, G, B 3센서의 유효파장에서 소산계수를 얻을 수 있다는 것을 보였으며, 이러한 3파장에서의 소산계수를 통하여 하루 동안의 옹스트롱 지수(Angstrom exponent) 변화를 얻었는데, 이 값은 0.7~1.6 범위에 존재한다는 것을 알 수 있었다. 이러한 지수는 입자의 크기와 관련된 중요한 정보로 사용할 수 있다.

• 천문학회지
• /
• 제29권spc1호
• /
• pp.179-180
• /
• 1996

The aim of the paper is to analyse the extinction law in the giant H II region NGC 3603. The ratio R is found to be greater than 5.0. In front of the cluster the reddening law is found to be normal. We have obtained a distance of $\~$5.3 Kpc which is significantly smaller than those adopted so far.

• 한국연소학회지
• /
• 제13권4호
• /
• pp.26-36
• /
• 2008

Experimental study is conducted to identify the existence of a shrinking flame disk and to clarify its flame characteristics through the inspection of critical mole fraction at flame extinction and edge flame oscillation at low strain rate flames. Experiments are made as varying global strain rate, velocity ratio, and burner distance. The transition from a shrinking flame disk to a flame hole is verified through gradient measurements of maximum flame temperature. The evidence of edge flame oscillation in flame disk is also provided through numerical simulation in microgravity. It is found at low strain rate flame disks in normal gravity that buoyancy effects are importantly contributing to lateral heat loss to burner rim, and is proven through critical mole fraction at flame extinction, edge flame oscillation, and measurements of flame temperature gradient along flame disk surface.

• Transactions on Electrical and Electronic Materials
• /
• 제12권6호
• /
• pp.241-244
• /
• 2011

An isolator transmits light in the forward direction and blocks light from passing in the reverse direction. It is regarded an essential optical component in medical, industrial, and research lasers for blocking reflection beams that cause optical damage and noise. It is also used as a communicative light intensifier to expand the lifespan of devices and enhance transmission quality. This study analyzed the characteristics of the core components in the construction of a polarization-independent isolator, namely, the walk-off polarizer and the Faraday rotator. Measurement of the extinction ratio of the resultant walk-off polarizer revealed that the ratio between the vertical and horizontal rays was 1,050:1 with a laser output of 0.032 W and 1,010:1 with a laser output of 2.68 W, thus presenting ratios similar to 1,000:1. In addition, the walk-off polarizer and Faraday rotator constructed in this study were used to compare output changes according to changes in power of input light and to check the penetration ratio. Results from the study presented variations in output value according to changes in power of input light. However, the average penetration ratio remained relatively consistent (~81.4%).