• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.291-291
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• 2021

모형이 갖는 불확실성의 정량화나 매개변수의 최적화는 계산시간의 기하급수적인 증가를 가져온다. 계산시간의 효율성을 극대화할 수 있는 기법으로 최근 대체모형이 개발되었으며, 다양한 분야에서 적용되고 있다. 그러나 대체모형은 훈련된 데이터 공간에서 크게 벗어난 극한 사상를 정확하게 모의하기는 어려운 단점이 있다. 본 연구는 이와 같은 대체모형의 단점을 개선할 수 있는 새로운 PCK(polynomial chaos-krigging) 기법을 제시한다. PCK는 PCE(polynomial chaos expansion) 기법과 OK(ordinary krigging) 기법을 결합한 것이며, PCK의 효과는 기존의 PCE 및 OK 모형의 결과와 비교하여 입증하였다. 본 연구의 분석 결과는 다음과 같다. (1) PCK는 더 적은 수의 훈련 샘플만으로도 원래 모형을 더 정확하게 대체할 수 있다. (2) 원래 훈련 샘플보다 약 3배 더 큰 극한사상을 모의했을 때, PCE와 OK는 예측이 실패하였지만, PCK의 예측은 정확하였다. (3) 민감도 분석 결과 PCK의 매개변수 특성과 거동이 PCE 및 OK보다 원래 모형의 특성과 거동에 더 일치한다. 본 연구에서는 3개의 대체모형의 결과를 원래모형의 결과와 비교하였으며 그 적용성을 극한강우에 대해 검토하였다. 일반적으로 훈련 샘플의 범위와 비슷한 강우사상에 대해서는 모든 대체모형의 결과가 우수하였으나, 훈련 샘플의 범위에서 벗어난 극한 사상의 모의는 PCK만 적용이 가능하였다. 제안된 대체모형은 극한사상의 예측에 있어 기존 대체모형보다 매우 향상된 정확도를 제공함을 확인할 수 있었다.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.81-88
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• 2018

The rainfall-runoff model made of sewer networks in the urban area is vast and complex, making it unsuitable for real-time urban flood forecasting. Therefore, the rainfall-runoff model is constructed and simplified using the sewer network of Daerim baisn. The network simplification process was composed of 5 steps based on cumulative drainage area and all parameters of SWMM were calculated using weighted area. Also, in order to estimate the optimal simplification range of the sewage network, runoff and flood analysis was carried out by 5 simplification ranges. As a result, the number of nodes, conduits and the simulation time were constantly reduced to 50~90% according to the simplification ranges. The runoff results of simplified models show the same result before the simplification. In the 2D flood analysis, as the simplification range increases by cumulative drainage area, the number of overflow nodes significantly decreased and the positions were changed, but similar flooding pattern was appeared. However, in the case of more than 6 ha cumulative drainage area, some inundation areas could not be occurred because of deleted nodes from upstream. As a result of comparing flood area and flood depth, it was analyzed that the flood result based on simplification range of 1 ha cumulative drainage area is most similar to the analysis result before simplification. It is expected that this study can be used as reliable data suitable for real-time urban flood forecasting by simplifying sewer network considering SWMM parameters.

• 대한핵의학회:학술대회논문집
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• 1997.05a
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• pp.176-176
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• 1997

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.425-428
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• 2001

본 논문에서 구현한 메쉬 편집기는 편집할 메쉬의 몇몇 점을 편집할 경우, 편집 정보가 그 점에 이웃한 점들에게도 영향을 미치게 되어, 편집 결과가 근사된 부드러운 곡면으로 표현하도록 하는 데 있다. 그러기 위해서는 3차원의 메쉬를 2차원 평면으로 매핑할 때, 매핑되는 원래의 메쉬의 모양이 크게 변형되지 않도록 하여야 하는데, 여기에 모양 유지 매개 변수화 방법을 사용하고 있다. 편집에 사용된 점의 편집 정보는 2차원 평면 다각형 안에 있는 서로 대응되는 점으로 매핑 되고, B-스플라인 보간으로 편집 정보는 2차 평면 안에 있는 다른 점들에게도 영향을 주게 된다. 이런 결과는 3차원 메쉬로 환원되어 부드럽게 근사된 곡면으로 표현된다.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.489-492
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• 2003

In this paper, we propose an iterative mixed norm image restoration algorithm using multi regularization parameters. A functional which combines the regularized l$_2$ norm functional and the regularized l$_4$ functional is proposed. The smoothness of each functional is determined by the regularization parameters. Also, a regularization parameter is used to determine the relative importance between the regularized l$_2$ functional and the regularized l$_4$ functional. An iterative algorithm is utilized for obtaining a solution and its convergence is analyzed.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.10-20
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• 2002

본 논문에서는 바다의 자유표면에서 생성되는 항력에 대한 물리적 특성에 대한 연구가 기술되었다. 2차원 파장(Wave Field) 매개변수해석기법(Parametric Analyzing Technique)을 근거로 한 파경계층(Wave Boundary Layer : WBL)의 1차원 모델로서 항력계산과 파경계층의 특성을 추정하였으며 이론의 간략화(Simplifying)에 대한 연구에 주력하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.229-233
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• 2002

비트율 제어 기법은 일정한 양의 비트만을 사용하여 최상의 화질을 얻기 위한 것이다. 기 중에서 최적의 비트율 제어기법(Optimal Rate Control)은 실시간 전송이 필요 없는 응용 분야에서 사용하거나 또는 모델 기반 비트율 제어기법의 성능을 평가하기 위하여 사용되었다. 하지만 기존의 방법들을 저전송율 비디오 부호기에 적용하였을 때에는, 양자화 매개변수간의 의존관계 때문에 최적의 해를 구하지 못하는 문제점이 생겼다. 따라서, 본 논문에서는 라그랑제 비용함수를 사용한 비터비 알고리즘을 이용하여 저 전송율 비디오 부호기에 적용할 수 있는 최적의 비트율 제어기법을 제안할 것이다.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.203-215
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• 2012

The objective of this study is to develop a catchment hydrologic cycle assessment model which can assess the impact of urban development and designing water cycle improvement facilities. Developed model might contribute to minimize the damage caused by urban development and to establish sustainableurban environments. The existing conceptual lumped models have a potential limitation in their capacity to simulate the hydrologic impacts of land use changes and assess diverse urban design. The distributed physics-based models under active study are data demanding; and much time is required to gather and check input data; and the cost of setting up a simulation and computational demand are required. The Catchment Hydrologic Cycle Assessment Tool (hereinafter the CAT) is a water cycle analysis model based on physical parameters and it has a link-node model structure. The CAT model can assess the characteristics of the short/long-term changes in water cycles before and after urbanization in the catchment. It supports the effective design of water cycle improvement facilities by supplementing the strengths and weaknesses of existing conceptual parameter-based lumped hydrologic models and physical parameter-based distributed hydrologic models. the model was applied to Seolma-cheon catchment, also calibrated and validated using 6 years (2002~2007) hourly streamflow data in Jeonjeokbigyo station, and the Nash-Sutcliffe model efficiencies were 0.75 (2002~2004) and 0.89 (2005~2007).

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.9-16
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• 2005

This paper presents the use of an Artificial Neural Network (ANN) as a viable means of forecasting Inundation Damage Area (IDA) in many watersheds. In order to develop the forecasting model with various environmental factors, we selected 108 watershed areas in South Korea and collected 49 damage data sets from 1990 to 2000, of which each set is composed of 27 parameters including the IDA, rainfall amount, and land use. After successful training processes of the ANN, a good agreement (R=0.92) is obtained (under present conditions) between the measured values of the IDA and those predicted by the developed ANN using the remaining 26 data sets as input parameters. The results indicate that the inundation damage is affected by not only meteorological information such as the rainfall amount, but also various environmental characteristics of the watersheds. So, the ANN proves its present ability to predict the IDA caused by an event of complex factors in a specific watershed area using accumulated temporal-spatial information, and it also shows a potential capability to handle complex non-linear dynamic phenomena of environmental changes. In this light, the ANN can be further harnessed to estimate the importance of certain input parameters to an output (e.g., the IDA in this study), quantify the significance of parameters involved in pre-existing models, and contribute to the presumption, selection, and calibration of input parameters of conventional models.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.676-682
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• 2012

The objectives of this study focused on measuring chlorophyll fluorescence related to drought stress comparing some parameters. Almost parameters were declined although they were not significant on the basis of mean values of fluorescence of total leaf area. While the ratio of fluorescence intensity variable chlorophyll ($F_V$) to fluorescence intensity maximal chlorophyll ($F_M$) was not changed, the effective quantum yield of photochemical energy conversion in photosystemII (${\Phi}PSII$) and chlorophyll fluorescence decrease ratio ($R_{fd}$) were slightly reduced, indicating inhibition of the electron transport from quinone bind protein A ($Q_A$) to quinone bind protein B ($Q_B$). Some parameters such as non-photochemical quenching rate ($NPQ_{_-LSS}$) and coefficients of non-photochemical quenching of variable fluorescence (qN) in mid-zone of leaf and near petiole zone leaf were significantly enhanced within 4 days after drought stress, which can be used as physiological stress parameters. Decrease in ${\Phi}PSII$ could was significantly measured in all leaf zones. In conclusion, three parametric evidences for chlorophyll fluorescence responses such as ${\Phi}PSII$, NPQ, and qN insinuated the possibility of photophysiological indices under drought stress.