• 한국연소학회지
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• 제17권1호
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• pp.22-29
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• 2012

The detachment stability characteristics of syngas $H_2$/CO jet attached flames were studied. The flame stability was observed while varying the syngas fuel composition, coaxial nozzle diameter and fuel nozzle rim thickness. The detachment stability limit of the syngas single jet flame was found to decrease with increasing mole fraction of carbon monoxide in the fuel. In hydrogen jet flames with coaxial air, the flame detachment stability was found to be independent of the coaxial nozzle diameter. However, velocities of appearance of liftoff and blowout velocities of lifted flames have dependence. At lower fuel velocity range, the critical coaxial air velocity leading to flame detachment increases with increasing fuel jet velocity, whereas at higher fuel velocity range, it decreases. This increasing-decreasing non-monotonic trend appears for all $H_2$/CO syngas compositions (50/50~100/0% $H_2$/CO). To qualitatively understand the flame behavior near the nozzle rim, $OH^*$ chemiluminescence imaging was performed near the detachment limit conditions. For all fuel compositions, local extinction on the rim is observed at lower fuel velocities(increasing stability region), while local flame extinction downstream of the rim is observed at higher fuel velocities(decreasing stability region). Maximum values of the non-monotonic trends appear to be identical when the fuel jet velocity is normalized by the critical fuel velocity obtained in the single jet cases.

• 생태와환경
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• 제37권3호통권108호
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• pp.304-312
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• 2004

수 생태계 내에서 흔히 볼 수 있는 3영양단계 먹이사슬 구조를 이루는 종들이 밀도비 의존 모델로써 구현 될 때 외부 환경에 대해서 어떻게 반응하는지를 연구하였다. 환경 요인은 주기적 요인과 일반적 노이즈 두 부분으로 나누었다. 주기적 요인이 온도로써 대표되었을 때 온도변이를 바이어스와 주기로 나누었고, 기타 복합적인 노이즈는 가우스 분포로 나타내었다. 온도변이 바이어스 ${\varepsilon}$, 온도주기 ${\Omega}$, 및 가우스 노이즈 크기 ${\'{O}}$가 서로 결합하여 3영양단계 먹이사슬에서 개체군 멸절을 포함한 다양한 개체군 동태를 보여 주었다. 변수의 적절한 값에 따라 '안정된 제한 사이클'이나 '이상한 끌개'를 보여 주었으며, 전체적으로 개체군 동태는 환경 변수에 따라 민감하게 반응하였고, 포식자 및 최상위포식자 개체군의 멸절시간이 조절되었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.11-20
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• 1999

Acoustic pressure response and NO formation of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flame let in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such non-monotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. Acoustic pressure response in each regime is investigated based on the Rayleigh criterion. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted. Emission index of NO shows similar behaviors as to the peak-temperature variation with pressure.

• 생물정신의학
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• 제18권2호
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• pp.80-89
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• 2011

Pavlovian fear conditioning has been extensively studied for the understanding of neurobiological basis of memory and emotion. Pavlovian fear conditioning is an associative memory which forms when conditioned stimulus (CS) is paired with unconditioned stimulus (US) once or repeatedly. This behavioral model is also important for the understanding of anxiety disorders such as posttraumatic stress disorder. Here we describe the neural circuitry involved in fear conditioning and the molecular mechanisms underlying fear memory formation. During consolidation some memories fade out but other memories become stable and concrete. Emotion plays an important role in determining which memories will survive. Memory becomes unstable and editable again immediately after retrieval. It opens the possibility for us of modulating the established fear memory. It provides us with very efficient tools to improve the efficacy of cognitive-behavior therapy and other exposure-based therapy treating anxiety disorders.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.1-8
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• 1998

Waste combustion above a grate is the core process of incineration systems, stability of which should be guaranteed for emission minimization. However, complicated reactions and heat and mass transfer phenomena make understanding the process difficult. One dimensional bed combustor with a numerical combustion model is utilized to investigate the combustion process of the bed, using cubic wood particles as a simulated fuel. Bed combustion behavior is characterized with apparent flame propagation speed, which has close relationship with air supply rate and chemical and physical characteristics of the fuel. Base on the availability of oxygen, two distinct reaction zone is identified; the oxygen-limited and the reaction-limited zone leading to the extinction by excessive convection cooling. The numerical modeling shows good agreement with the experimental results. The transient bed combustion behavior of local temperature and oxygen consumption rate is adequately reproduced. The numerical model is extended to model the waste bed combustion of a commercial incineration plant, which shows meaningful results as well.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제4권3호
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• pp.131-133
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• 2023

Polyphylla laticollis manchurica Semenov, 1900, is a critically endangered species in the Republic of Korea and is strictly protected as a Class I endangered species. Although this beetle species faces a threat of extinction, its ecological understanding is limited. Previous studies conducted on this species in the Republic of Korea have focused only on its taxonomy and mitochondrial genome sequences. Herein, we report an observation of the mating of adults of P. l. manchurica in June 2021, during an ongoing study on Korean beetles. This incidence was reported around light sources from newly constructed townhouses near Geumgang River. Larval habitats were observed along the river between April 2022 and March 2023. Particularly, two larvae were found inside the plant debris, and three were found under the roots of reeds. This study provides key information on the mating ecology of P. l. manchurica that can assist conservation efforts of this critically endangered species.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.295-298
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• 2006

메탄/질소-공기 저 신장율 대향류 확산화염에서 화염소화 거동과 에지화염의 진동불안정성에 대한 실험적 연구를 수행하였다. 특히, 저 신장율 화염에서 복사열손실 뿐만 아니라 측면전도 열손실이 현저해 진다. 각 전체 신장율에서 화염진동의 시작조건과 진동모드를 제안하였다. 화염길이는 측면 전도열손실과 밀접한 관계를 가지고 있으며 화염소화와 화염진동에 중대한 영향을 미친다. 저 신장율 에지화염의 진동모드는 성장모드, 감쇠모드 그리고 조화모드로 요약된다. 또한, 각 진동모드의 조건을 전체신장율과 희석제의 몰분율에 대한 안전화선도를 작성하였다.

• 비파괴검사학회지
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• 제13권4호
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• pp.9-17
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• 1994

초음파법은 종래의 금속재료는 물론 최근의 금속 복합재료등과 같은 신소재의 재료특성을 비파괴적으로 평가할 수 있는 일반적인 방법이다. 그러나 이와같은 재료들의 비파괴 특성 평가를 위해 초음파법을 적용시킬 경우 무엇보다도 재료 내부를 전파하는 탄성파의 전파특성에 대한 물리적 현상에 대한 이해가 필수적이다. 본 연구에서는 금속 복합재료의 제조공정에서 일반적으로 많이 발생되는 기지재와 강화재 사이의 계면 문제 및 기지재에 분포하는 강화재의 체적함유율의 변화등에 의한 유효 평면파의 다중 산란 특성을 SiC 입자강화 6061 알루미늄 복합재료에 대해 Lax의 준 결정 근사(quasi-crystalline approximation) 이론 및 소감정리 (extinction theorem)를 기초로 하여 이론적으로 해석하였다. 그 결과 SiC 입자 강화재의 체적 함유율의 변화에 대한 유효 평면파의 위상속도 및 감쇠의 주파수 의존 특성과 금속복합재료에 있어서의 기지재와 강화재 사이의 계면층의 탄성특성에 대한 위상속도의 변화 특성이 명확하게 규명되었다.

• 대한기계학회논문집B
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• 제25권4호
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• pp.540-545
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• 2001

Many previous researches on the premixed flame in a tube have treated the unsteady flame behaviors in which the shape, position and intensity of the flame varied, but more detail and fundamental research has been necessary. The flame stabilization condition in a tube, a unique steady state, and the unsteady behaviors, using the stabilization condition as an initial condition, were carried out in recent years. In this paper, propane-air premixed flame was stabilized in a tube and the flame behavior was observed when the mean velocity variation was imposed into the opposite direction of the initial mean velocity. The velocity variation is larger than the burning velocity and longer than the reaction time scale. During the period of the velocity variation flame is not extinguished. But after the period of the mean velocity variation the flame could be re-stabilized or be extinguished depending on the experimental conditions: equivalence ratio, period of velocity variation and magnitude of velocity variation. The extinction mechanisms were classified into the two cases, one is caused by the flame stretch in the shear layer near the wall, and the other is caused by the vortices and vortexes, which are generted by the acoustic waves.

• 대한원격탐사학회지
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• 제17권3호
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• pp.211-218
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• 2001

대기복사모델인 MODTRAN을 이용해 다목적실용위성 2호 탑재체인 Multispectral Camera (MSC)의 총복사량에 대한 계산을 수행하고 그 결과를 분석해 보았다. 모델 계산에서 4계절 조건을 모의실험하기 위해 1월 15일, 7월 15일 계산에 대해 중위도 동절기 및 하절기 모델대기를, 4월 15일, 10월 15일에 대해 US 표준대기를 각각 사용했다. 다목적실용위성 2호 궤도 조건과 각 계절에 대한 대표적인 태양천정각 (solar zenith angle)이 고려되었다. 시정거리는 대류권 에어로솔 소광계수 (tropospheric aerosol extinction)에 해당하는 50km가, 지표의 알베도는 맑은 날 지구 연평균 값에 해당하는 0.135가 가정되었다. MSC 계약서 값은 위 일반적 조건을 가정하고 얻은 모델 계산 총복사량보다 MSC 관측 파장대역 대부분에서 상당히 크다는 것을 알게 되었다. 또한 균일한 지표 알베도를 가정하고 얻은 모델 결과의 분광파장 특징이 MSC 계약서 값의 경향과 다름을 보였다. 이들 결과로부터 향후 획득될 MSC영상은 비교적 어두운 영상이 될 것으로 추론된다.