• The Korean Journal of Ecology
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• 제24권4호
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• pp.227-232
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• 2001

The biomass structure for three major components viz., the dominant grass, Chrysopogon zeylanicus Thw., the 'other grasses' and the'remaining species'and dry matter dynamics for total community were studied over a period of one year in an annual fire influenced subtropical humid grassland community in Western Ghats, India. The biomass of aboveground, belowground and litter compartments were high as in other humid grasslands and generally have positive correlation with rainfall, rainy days and relative humidity with the exception of litter parts. The above and belowground net primary productions (4,561 and 722 g/㎡, respectively) were also higher and were comparable with other humid tropical grasslands. The turnover of organic matter was rapid, Of the total input of 14.47 g/㎡ into the system, about 86.3% was allocated to above ground parts and 13.7% to below ground parts. The total disappearance was 2.56 g/㎡ and it was accounted to be 17.68% of the total output. The net surplus of dry matter (82.32%) in the post fire community indicates that the grassland was maintained in a seral stage. Hence it is suggested that prescribed burning may keep this ecosystem in a highly productive and seral stage.

• Journal of Ecology and Environment
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• 제38권3호
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• pp.281-291
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• 2015

To clarify the effects of forest fire on the carbon budget of a forest ecosystem, this study compared the seasonal variation of soil respiration, net primary production and net ecosystem production (NEP) over the year in unburned and burned Pinus densiflora forest areas. The annual net carbon storage (i.e., NPP) was $5.75t\;C\;ha^{-1}$ in the unburned site and $2.14t\;C\;ha^{-1}$ in the burned site in 2012. The temperature sensitivity of soil respiration (i.e., $Q_{10}$ value) was higher in the unburned site than in the burned site. The annual soil respiration rate was estimated by the exponential regression equation with the soil temperatures continuously measured at the soil depth of 10 cm. The estimated annual soil respiration and heterotrophic respiration (HR) rates were 8.66 and $4.50t\;C\;ha^{-1}yr^{-1}$ in the unburned site and 4.08 and $2.12t\;C\;ha^{-1}yr^{-1}$ in the burned site, respectively. The estimated annual NEP in the unburned and burned forest areas was found to be 1.25 and $0.02t\;C\;ha^{-1}yr^{-1}$, respectively. Our results indicate that the differences of carbon budget and cycling between both study sites are considerably correlated with the losses of living plant biomass, insufficient nutrients and low organic materials in the forest soil due to severe damages caused by the forest fire. The burned Pinus densiflora forest area requires at least 50 years to attain the natural conditions of the forest ecosystem prior to the forest fire.

• 방재기술
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• 통권11호
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• pp.23-30
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• 1991

For the prevent of fire accident or explosion disasters from inflammable gas and vapour, flame arresters are used in chemical equipment, oil tank or other similar installation. The flame arresters have been used mainly wire gauze type. Wire gauze type flame arrestes is affected several factors. We have know that the quenching ability has a great of difference the preference in accordance with flame velocity, direction of flame propagation and wire net of mesh and number of qauze and introduce examination result data quoated from the abroad.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.155-156
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• 2006

Developed and conducted a performance test of the Water mist system that is satisfied with the requirement of a fire test requiring Class 3 Engine Mock-up exceeding net volume $3,000m^3$ as per IMO's MSC/Circ. 668 Appendix B(Test method for fire testing equivalent water-based fire-extinguishing systems for machinery spaces of category A and cargo pump rooms).Even though fuel atomizing was continued for 15 sec. after stopping of the system according to the test method relating to the atomizing fire type, no fire was reignited. This result shows the excellence of the system. There was no damage to the contents of the system after the test.

• 대한원격탐사학회지
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• 제39권5_3호
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• pp.979-995
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• 2023

산불은 예측이 어려운 재해이기 때문에 실시간 모니터링을 통해 빠르게 대응하는 것이 중요하며, 정지 궤도 위성 영상은 광역을 짧은 시간 간격으로 모니터링할 수 있어 산불 탐지 분야에 활발히 이용되고 있다. 기존의 위성 영상 기반 산불 탐지 알고리즘은 밝기 온도의 통계량 분석을 통한 임계값 기반으로 이상치를 탐지하는 방향으로 진행되어 왔다. 그러나 강도가 약한 산불을 탐지하기 어렵거나, 적절한 임계값 설정의 어려움으로 일반화 성능이 저하되는 한계점이 있어 최근에는 기계학습을 이용한 산불 탐지 알고리즘들이 제시되고 있다. 현재까지는 random forest, VanillaConvolutional neural network (CNN), U-net 구조 등의 비교적 간단한 기법이 적용되고 있다. 따라서, 본 연구에서는 정지궤도 위성인 Advanced Himawari Imager를 이용하여 동아시아와 호주를 대상으로 State of the Art (SOTA)딥러닝 기법을 적용한 산불 탐지 알고리즘을 개발하고자 하였다. SOTA 모델은 EfficientNet과 lion optimizer를 적용하여 개발하고, Vanilla CNN 구조를 사용한 모델과 산불 탐지 결과를 비교하였다. EfficientNet은 동아시아와 호주에서 0.88 및 0.83의 F1-score를 기록함으로써 CNN (동아시아: 0.83, 호주: 0.78)에 비해 뛰어난 성능을 입증하였다. EfficientNet에 불균형 문제 해결을 위한 weighted loss, equal sampling, image augmentation 기법 적용 시, 동아시아와 호주에서 각각 0.92와 0.84의 F1-score를 기록함으로써 적용 전(동아시아: 0.88, 호주: 0.83)에 비하여 성능이 향상되었음을 확인하였다. 본 연구를 통하여 제시된 SOTA 딥러닝 기법의 산불 탐지에의 적용 가능성과 딥러닝 모델의 성능 향상을 위해 고려해야 할 방향은 향후 산불탐지 분야에 대한 딥러닝 적용에 도움이 될 것으로 기대된다.

• 한국경영과학회지
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• 제30권4호
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• pp.99-115
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• 2005

For an analysis of the performance of a computer system, the minimum cycle time method has been widely used. The minimum cycle time method is a mathematical technique with which we can find the minimum duration time needed to fire all the transitions at least once and coming back to the Initial marking in a timed net. A timed net is a modified version of a Petri net where a transition is associated with a delay time. In the real world, an event is associated with a probability of occurrence. However, a timed net is not equipped with any facility of specifying probability of event occurrence. Therefore, the minimum cycle time method applied on a timed net can easily overlook probabilities of occurrences of events and yield a wrong result. We are proposing 'Timed Net with Probabilities of Choices' where a transition can be associated with both delay time and a probability of occurrence. We also introduce an algorithm for minimum cycle time analysis on a 'Timed Net with Probabilities of Choices'. As an example of application, we are performing an analysis of the location based service system using 'Timed Net with Probabilities of Choices'.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2941-2959
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• 2022

The fire brigade non-suppression probability model is a major factor that should be considered in evaluating fire-induced risk through fire probabilistic risk assessment (PRA), and also uncertainty is a critical consideration in support of risk-informed performance-based (RIPB) fire protection decision-making. This study developed an optimal integrated probabilistic fire brigade non-suppression model considering uncertainty of parameters based on the Bayesian Markov Chain Monte Carlo (MCMC) approach on electrical fire which is one of the most risk significant contributors. The result shows that the log-normal probability model with a location parameter (µ) of 2.063 and a scale parameter (σ) of 1.879 is best fitting to the actual fire experience data. It gives optimal model adequacy performance with Bayesian information criterion (BIC) of -1601.766, residual sum of squares (RSS) of 2.51E-04, and mean squared error (MSE) of 2.08E-06. This optimal log-normal model shows the better performance of the model adequacy than the exponential probability model suggested in the current fire PRA methodology, with a decrease of 17.3% in BIC, 85.3% in RSS, and 85.3% in MSE. The outcomes of this study are expected to contribute to the improvement and securement of fire PRA realism in the support of decision-making for RIPB fire protection programs.

• Nuclear Engineering and Technology
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• 제45권2호
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• pp.223-236
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• 2013

In the present study the behavior of fire and the residual strength of fire-ignited RC slabs are investigated by experimental tests and numerical simulations. The fire tests of RC slabs were carried out in a furnace using the ISO 834 standard fire. The load capacity of the cooled RC slabs that were not loaded during the fire tests was evaluated by additional 3 point bending tests. The influence of the proportion of PP (polypropylene) fibers in the RC slabs on the structural behavior of the RC slabs after the fire loading was investigated. The results of the fire tests showed that the maximum temperature of concrete with PP fiber was lower than that of concrete without PP fiber. As the concrete was heated, the ultimate compressive strength decreased and the ultimate strain increased. The load-deflection relations of RC slabs after fire loading were compared by using existing stress-strain-temperature models. The comparison between the numerical analysis and the experimental tests showed that some numerical analyses were reliable and therefore, can be applied to evaluate the ultimate load of RC slabs after fire loading. The ultimate load capacity after cooling down the RC slabs without PP fiber showed a considerable reduction from that of the RC slabs with PP fiber.

• 대한원격탐사학회지
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• 제38권6_1호
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• pp.1273-1283
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• 2022

최근 기후변화로 인해 중대형 산불이 빈번하게 발생하여 매년 인명 및 재산피해로 이어지고 있다. 원격탐사를 활용한 산불 피해지 모니터링 기법은 신속한 정보와 대규모 피해지의 객관적인 결과를 취득할 수 있다. 본 연구에서는 산불 피해지를 분류하기 위해 Sentinel-2의 분광대역, 정규식생지수(normalized difference vegetation index, NDVI), 정규수역지수(normalized difference water index, NDWI)를 활용하여 2022년 3월 발생한 강릉·동해 산불 피해지를 대상으로 U-net 기반 convolutional neural networks (CNNs) 딥러닝 모형을 모의하였다. 산불 피해지 분류 결과 강릉·동해 산불 피해지의 경우 97.3% (f₁=0.486, IoU=0.946)로 분류 정확도가 높았으나, 과적합(overfitting)의 가능성을 배제하기 어려워 울진·삼척 지역으로 동일한 모형을 적용하였다. 그 결과, 국립산림과학원에서 보고한 산불 피해 면적과의 중첩도가 74.4%로 확인되어 모형의 불확도를 고려하더라도 높은 수준의 정확도를 확인하였다. 본 연구는 농림위성과 유사한 분광대역을 선택적으로 사용하였으며, Sentinel-2 영상을 활용한 산불 피해지 분류가 정량적으로 가능함을 시사한다.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1571-1584
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• 2023

In this study, a numerical analysis was performed as part of an international joint research project to reproduce a real cable tray fire that occurred in the heater bay area of the turbine building of a nuclear power plant. A sensitivity analysis was performed on various input parameters to derive results consistent with the sprinkler activation time obtained from the fire event analysis. For all sensitive parameters, the normalized sprinkler activation time correlated well with the power function of the normalized sprinkler height. A correlation equation was developed to identify the sprinkler activation time at any location when determining the slope or fire growth rate under the conditions assuming a linear or t-squared heat release rate (HRR) time curve. Various cable fire growth assumptions were used to determine which assumption was better to provide the prediction coincident with the information given from the fire event analysis in terms of the sprinkler activation time and total energy generated from cables damaged by fire. In the comprehensive analysis of all the sensitive parameters, the standard deviation of the input parameters increased as the sprinkler height decreased. Within the range of the sensitivity parameter values given in this study, when considering all sprinkler heights, the standard deviation of the cable model change was the largest and that of the overhang position change was the smallest.