• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.537-537
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• 2015

In recent decades, the independence and identical distribution (iid) assumption for extreme events has been shown to be invalid in many cases because long-term climate variability resulting from phenomena such as the Pacific decadal variability and El Nino-Southern Oscillation may induce varying meteorological systems such as persistent wet years and dry years. Therefore, in the current study we propose a new parameter estimation method for probability distribution models to more accurately predict the magnitude of future extreme events when the iid assumption of probability distributions for large-scale climate variability is not adequate. The proposed parameter estimation is based on a metaheuristic approach and is derived from the objective function of the rth power probability-weighted sum of observations in increasing order. The combination of two distributions, gamma and generalized extreme value (GEV), was fitted to the GEV distribution in a simulation study. In addition, a case study examining the annual hourly maximum precipitation of all stations in South Korea was performed to evaluate the performance of the proposed approach. The results of the simulation study and case study indicate that the proposed metaheuristic parameter estimation method is an effective alternative for accurately selecting the rth power when the iid assumption of extreme hydrometeorological events is not valid for large-scale climate variability. The maximum likelihood estimate is more accurate with a low mixing probability, and the probability-weighted moment method is a moderately effective option.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.499-499
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• 2018

Hydro-meteorological extremes are trivial in these days. Therefore, it is important to identify extreme hydrological events in advance to mitigate the damage due to the extreme events. In this context, exploring temporal distribution of sub-daily extreme rainfall at multiple rain gauges would informative to identify different states to describe severity of the disaster. This study proposehidden Markov chain model (HMM) based rainfall analysis tool to understand the temporal sub-daily rainfall patterns over South Korea. Hourly and daily rainfall data between 1961 and 2017 for 92 stations were used for the study. HMM was applied to daily rainfall series to identify an observed hidden state associated with rainfall frequency and intensity, and further utilized the estimated hidden states to derive a temporal distribution of daily extreme rainfall. Transition between states over time was clearly identified, because HMM obviously identifies the temporal dependence in the daily rainfall states. The proposed HMM was very useful tool to derive the temporal attributes of the daily rainfall in South Korea. Further, daily rainfall series were disaggregated into sub-daily rainfall sequences based on the temporal distribution of hourly rainfall data.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.158-158
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• 2019

Recent studies show the possibility of more frequent extreme events as a result of the changing climate. These weather extremes, such as excessive rainfall, result to debris flow, river overflow and urban flooding, which post a substantial threat to the community. Therefore, an effective flood model is a crucial tool in flood disaster mitigation. In recent years, a number of flood models has been established; however, the major challenge in developing effective and accurate inundation models is the inconvenience of running multiple models for separate conditions. Among the solutions in recent researches is the development of the combined 1D-2D flood modeling. The coupled 1D-2D river flood modeling allows channel flows to be represented in 1D and the overbank flow to be modeled over two-dimension. To test the efficiency of this approach, this research aims to assess the capability of HEC-RAS model's implementation of the combined 1D-2D hydraulic simulation of river overflow inundation, and compare with the results of GERIS and FLUMENS 2D flood model. Results show similar output to the flood models that had used different methods. This proves the applicability of the HEC-RAS 1D-2D coupling method as a powerful tool in simulating accurate inundation for flood events.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.47-52
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• 2004

In the design of scramjet intake for hypersonic flight, a variety of aerothermodynamics phenomena are encountered. These phenomena include blunt leading - edge effects, boundary layer development issues, transition, inviscid / viscous coupling, shock - shock interactions, shock / boundary - layer interactions, and flow profile effects. For intakes that are designed to operate within a narrow Mach number / altitude envelope, an understanding of a few of these phenomena might be required. In this work several predominant flowfield phenomena (viscous phenomena, boundary - layer separation, and combustor entrance profile) are discussed to investigate the performance of the intake at the altitude and angle of attack extremes of the HyShot flight experiment.

• Convergence Security Journal
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• v.17 no.5
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• pp.49-55
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• 2017

In case of security of IoT-based areas in ICBM industry, the anxiety about safety goes to extremes in public and national safety area, so that the demand for security service related to disaster/safety management is increasing. Like this, as a security service for safety, CCTVs are installed/operated for the purpose of maintenance of public order and crime prevention. Especially, as the recorded images are presented as crucial evidences of crimes, they are rapidly increasing. However, as adverse effects of CCTVs, it is highly possible to unintentionally leak personal information in the process of performing the original purpose, or to violate someone's privacy in case when such technologies are abused. Therefore, it would be necessary to have researches on the multilaterally-combined mechanism for the protection of image privacy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.116-121
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• 2019

The LVDT (Linear Variable Displacement Transducer) type sensor used for the existing ship's steering gear is simple on / off that does not perform proportional control operation to the control & unloading device. When the main spool is located at both extremes, It is reflected in the price by using an expensive sensor for import. In this paper, the Hall Effect Sensor is applied to Hydraulic Locking Alarm to analyze classification rules, structure, characteristics and operation principle of valves, and research on localization development in terms of cost reduction. The comparative analysis of the existing prototypes and the cause analysis of the problems were carried out, and the structural analysis showed satisfactory results within the allowable stress range. In addition, it was verified through experiments that the actual operation is realized by applying the actual developed product, and it was confirmed that the load on the maximum value exceeds the allowable maximum load even in the case of the universal tensile test in preparation for the departure of the rod casing.

• Journal of English Language & Literature
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• v.57 no.1
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• pp.3-25
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• 2011

As extremes of climate such as heavy storms, rainfalls, and droughts tend to be routine in recent years, global climate change becomes a serious concern not only for natural scientists but also for scholars of the human sciences. Efforts to tackle the anthropogenic climate change certainly require not only scientific knowledge about it but also a new sociocultural paradigm for valorizing and respecting nature in its own right. The huge casualties and mass destruction caused by recent climate disasters also remind us that nature has been an important factor to bring about changes in human history-a fact largely ignored in traditional history. This again validates the ecocritical request to prioritize place, physical setting, or the relationship characters hold with the natural world in understanding literary works. In this context this paper aims to demonstrate the importance of the meteorological vision in creating as well as understanding literary and cultural texts by examining such works as Shelley's "The Cloud," Byron's "Darkness," Keats's "To Autumn," all produced during the period of dramatic climate change including "the year without summer." It also briefly discusses Roland Emmerich's 2004 movie The Day after Tomorrow as a way of understanding recent cultural responses to the crisis of global warming.

• ALGAE
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• v.37 no.1
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• pp.33-47
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• 2022

Two new species of Pseudostaurosiropsis are described based on material collected from rivers in southern United States of America, P. californicus sp. nov. and P. elaboratus sp. nov. Both species have specific characters that set them apart from taxa currently ascribed to the genus. Pseudostaurosiropsis californicus sp. nov. has lanceolate valves with subrostrate, broadly rounded apices, an axial area at the same level as the virgae in internal and external views and both are at the same level as striae in external view, the spine tips are dentate and their growth is produced by filamentous extensions, and it has equal-sized apical pore fields on both valve extremes. On the other hand, P. elaboratus sp. nov. has heavily silicified valves, the virgae are slender than the striae in outer view and wider in inner view, it only has a single, externally occluded apical pore field on one valve extreme, and the spines have a solid core. All species within Pseudostaurosiropsis are contrasted with one another and unique features are described for each based on literature and newly collected image data from type material. The genus is reconsidered and two distinguishing features are recognized: rotae externally occluding the areolae and areolae that are funnel-shaped. These features are contrasted with those in other genera and additional published species that should be included in Pseudostaurosiropsis are discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.285-285
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• 2023

기후변화로 인한 변동성의 증가는 돌발 홍수, 홍수량 증가로 이외에도 강우 사상의 변화, 가뭄의 빈도 및 강도의 증대 등의 문제를 이어질 수 있다. 이러한 기후변화에 대응하기 위하여 기후변화 시나리오를 제시하고 이를 정책적으로 반영할 수 있도록 하고 있다. 기존 IPCC 5차 보고서에 활용한 RCP(Representative Concentration Pathway) 시나리오에서는 온실가스 농도변화만을 반영하고 있으나, 최근 IPCC 6차 보고서에서는 사회적인 노력과 경제적 구조 등 전반적인 기후정책, 사회 불균형 등을 고려한 SSP(Shared Socio-economic Pathways) 시나리오를 제시하였다. 본 연구에서는 2가지 기후변화 시나리오의 차이점과 유사점을 강수 중심으로 평가하였다. 기존의 RCP 시나리오에 비하여 극한 강우 사상의 변화를 비교 및 평가하기 위하여 CORDEX-EA에서 제공하는 지역기후모델(Regional Climate Model; RCM) 기반에 시나리오를 수집하여 극한기후지수를 산정하였다. 극한기후사상을 비교하기 위하여 WMO에서 활용하는 ETCCDI(Expert Team on Climate Change Detection and Indices) 지수 중 강우 관련 지수인 R10mm, RX1day, RX5day, RD95P, RD99P, SDII를 선정하여 시나리오 별로 결과를 비교하여 제시하였다. 또한, 기존의 연대기 기준의 평가방식에서 탈피하여 동일한 기온 상승 시점에 따라 변화를 확인하기 위한 분석절차를 수립하였다. 즉, 1.5℃, 2℃, 3℃ 및 4℃ 상승한 시점의 ETCCDI 지수를 산정하여 극한기후사상을 비교 및 평가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.113-113
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• 2023

기후변화로 인한 온도 상승이 대기 중 수분량을 증가시키면서 극한 강우가 전 세계적으로 빈번하게 발생하고 있으며, 이에 따라 대규모 홍수 피해가 지속적으로 초래되고 있다. 본 연구에서는 이러한 현상에 대응하기 위한 노력으로, 대기 연직 기둥 내 총 수분량을 나타내는 총가강수량(Total Precipitable Water, TPW)과 극한 강우사상(Extreme Precipitation, EP) 간의 연관성이 강우지속기간에 따라 어떻게 변하는지 분석하였다. 관측 및 재해석(reanalysis) 데이터를 활용하여 동시극한지수(Concurrent Extremes Index, CEI, 0~1, 1에 가까울수록 강한 연결)로 두 변수 간의 정량적 연결 강도를 살펴보았다. 분석 결과, CEI의 지속 시간에 따른 변동 경향성은 지역에 따라 상당한 차이를 보였다. 지중해와 중앙아시아와 같은 대부분의 중위도 지역에서는 강우의 지속 기간이 길어질수록 CEI 값이 급격히 감소하였다. 그러나 한반도를 포함한 동아시아 지역은 중위도임에도 불구하고 긴 지속 기간의 강우 사상에서도 높은 수준의 CEI 값을 유지하였다. 이러한 동아시아 지역의 경향성은 열대지역과 매우 유사하게 나타났으며, 이는 동아시아 지역의 극한 강우 증가가 기후변화의 직접적인 영향을 받을 수 있음을 시사한다.