• Journal of Soil and Groundwater Environment
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• v.11 no.5
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• pp.9-19
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• 2006

The accurate estimation of groundwater recharge is important for the proper management of groundwater systems. The widely used techniques of groundwater recharge estimation include water table fluctuation method, baseflow separation method, and annual water balance method. However, these methods can not represent the temporal-spatial variability of recharge resulting from climatic condition, land use, soil storage and hydrogeological heterogeneity because the methods are all based on the lumped concept and local scale problems. Therefore, the objective of this paper is to present an effective method for estimating groundwater recharge with spatial-temporal variability using the SWAT model which can represent the heterogeneity of the watershed. The SWAT model can simulate daily surface runoff, evapotranspiration, soil storage, recharge, and groundwater flow within the watershed. The model was applied to the Musimcheon watershed located in the upstream of Mihocheon watershed. Hydrological components were determined during the period from 2001 to 2004, and the validity of the results was tested by comparing the estimated runoff with the observed runoff at the outlet of the catchment. The results of temporal and spatial variations of groundwater recharge were presented here. This study suggests that variations in recharge can be significantly affected by subbasin slope as well as land use.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.156-162
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• 2010

When eccentric or inclined load acts on foundation of the port & harbor structures, partial safety factors of bearing capacity limit state were estimated using reliability analysis. Current Korean technical standards of port and harbor structures recommend to estimate the geotechnical bearing capacity using the simplified Bishop method. In practice, however, simple method of comparing ground reaction resistance with allowable bearing capacity has been mostly used by design engineers. While the simple method gives just one number fixed but somewhat convenient, it could not consider the uncertainty of soil properties depending on site by site. Thus, in this paper, partial safety factors for each design variable were determined so that designers do perform reliability-based level 1 design for bearing capacity limit state. For these, reliability index and their sensitivities were gained throughout the first order reliability method(FORM), and the variability of the random variables was also considered. In order to verify partial safety factors determined here, a comparison with foreign design codes was carried out and were found to be reasonable in practical design.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.305-317
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• 2019

The RMR and Q-system for characterizing rock mass and drilling core, and for estimating the support and reinforcement measures in mine galleries, tunnels and caverns have been widely used by engineers. SMR has been widely used in the rock mass classification for rock slope, but Q-Slope has been introduced into slopes since 2015. In the last ten years, a modified Q-system called Q-slope has been tested by the many authors for application to the benches in open pit mines and excavated road rock slopes. The results have shown that a simple correlation exists between Q-slope values and the long-term stable and unsupported slope angles. Just as RMR and Q have been used together in a tunnel or underground space and complemented by comparison, Q-Slope can be used in parallel with SMR. This paper introduces how to use Q-Slope which has not been announced in Korea and application examples of Pasir open pit coal mine in Indonesia.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.791-799
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• 2022

Among excursion and ferry boats, small boats with a length of less than 12 m are exempted from the stability standard according to the ship safety act. The boarding capacity of these small excursion and ferry boats is calculated by the seating area according to the excursion ship and ferry business act. Many excursion and ferry boats have installed deck structures such as awnings after launching. Therefore, this study attempted to analyze the cause of the accident by estimating the stability based on the case of an actual ferry boat capsizing accident. The analysis results indicated that passengers stood up to disembark at the same time while the boarding capacity was exceeded. However, even if the ferry boat complied with the boarding capacity, a possibility of capsize existed if the passengers on one side of the boat stood up. Therefore, the following were suggested to improve the safety: calculating the boarding capacity using the stability test and recommending the maximum total weight for the boarding capacity.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.3
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• pp.261-269
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• 1989

Agricultural activities in Chejudo require more specialized weather services in this region. The meteorological information available from the Korea Meteorological Service (KMS) is limited in its areal coverage because the KMS stations are located along the narrow band of coastal area. topoclimatological technique which makes use of empirical relationships between the topography and the weather can be applied to produce reasonable estimates of the climatic variables such as air temperature and precipitation over remote land area where routine observations are rare. Presentation of these estimates in a from of fine-mesh grid map can also be helpful to upgrade the quality of weather services in this region. Altitude values of the 250 m grid points were read from a 1: 25000 topographic map and the mean altitude, the mean slope, and the aspect of the slope were determined for each 1 km$^2$ land area from these altitude data. Daily minimum air temperature data were collected from 18 points in Chejudo during the winter period from November 1987 to February 1988. The data were grouped into 3 sets based on synoptic pressure pattern. Departures from the KMS observations were regressed to the topographical variables to delineate empirical relationships between the local minimum temperature under specific pressure patterns and the site topography. The selected regression equations were used to calculate the daily minimum temperature for each 1 km$^2$ land area under the specific pressure patterns. The outputs were presented in a fine-mesh grid map with a 6-level contour capability.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.3
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• pp.124-131
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• 2016

Baseline correction is very important due to influence on performance of spectral analysis in application of spectroscopy. Baseline is often estimated by parameter selection using visual inspection on analyte spectrum. It is a highly subjective procedure and can be tedious work especially with a large number of data. For these reasons, it is an objective and automatic procedure is necessary to select optimal parameter value for baseline correction. Asymmetrically reweighted penalized least squares (arPLS) based on penalized least squares was proposed for baseline correction in our previous study. The method uses a new weighting scheme based on the generalized logistic function. In this study, we present an automatic selection of optimal parameter for baseline correction using arPLS. The method computes fitness and smoothness values of fitted baseline within available range of parameters and then selects optimal parameter when the sum of normalized fitness and smoothness gets minimum. According to the experimental results using simulated data with varying baselines, sloping, curved and doubly curved baseline, and real Raman spectra, we confirmed that the proposed method can be effectively applied to optimal parameter selection for baseline correction using arPLS.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.387-387
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• 2022

기존 홍수기시 댐 운영은 예측 강우와 실시간 관측 강우를 이용하여 댐 운영 모형을 수행하며, 예측 결과에 따라 의사결정 및 댐 운영을 실시하게 된다. 하지만 이 과정에서 반복적인 분석이 필요하며, 댐 운영 모형 수행자의 경험에 따라 예측 결과가 달라져서 반복작업에 대한 자동화, 모형 수행자에 따라 달라지지 않는 예측 결과의 일반화가 필요한 상황이다. 이에 댐 운영 모형에 AI 기법을 적용하여, 다양한 강우 상황에 따른 자동 예측 및 모형 결과의 일반화를 구현하고자 하였다. 이를 위해 수자원 분야에 적용된 국내외 129개 연구논문에서 사용된 딥러닝 기법의 활용성을 분석하였으며, 다양한 수자원 분야 AI 적용 사례 중에서 댐 운영 예측 모형에 적용한 사례는 없었지만 유사한 분야로는 장기 저수지 운영 예측과 댐 상·하류 수위, 유량 예측이 있었다. 수자원의 시계열 자료 활용을 위해서는 Long-Short Term Memory(LSTM) 기법의 적용 활용성이 높은 것으로 분석되었다. 댐 운영 모형에서 AI 적용은 2개 분야에서 진행하였다. 기존 강우관측소의 관측 강우를 활용하여 강우의 패턴분석을 수행하는 과정과, 강우에서 댐 유입량 산정시 매개변수 최적화 분야에 적용하였다. 강우 패턴분석에서는 유사한 표본끼리 묶음을 생성하는 K-means 클러스터링 알고리즘과 시계열 데이터의 유사도 분석 방법인 Dynamic Time Warping을 결합하여 적용하였다. 강우 패턴분석을 통해서 지점별로 월별, 태풍 및 장마기간에 가장 많이 관측되었던 강우 패턴을 제시하며, 이를 모형에서 직접적으로 활용할 수 있도록 구성하였다. 강우에서 댐 유입량을 산정시 활용되는 매개변수 최적화를 위해서는 3층의 Multi-Layer LSTM 기법과 경사하강법을 적용하였다. 매개변수 최적화에 적용되는 매개변수는 중권역별 8개이며, 매개변수 최적화 과정을 통해 산정되는 결과물은 실측값과 오차가 제일 적은 유량(유입량)이 된다. 댐 운영 모형에 AI 기법을 적용한 결과 기존 반복작업에 대한 자동화는 이뤘으며, 댐 운영에 따른 상·하류 제약사항 표출 기능을 추가하여 의사결정에 소요되는 시간도 많이 줄일 수 있었다. 하지만, 매개변수 최적화 부분에서 기존 댐운영 모형에 적용되어 있는 고전적인 매개변수 추정기법보다 추정시간이 오래 소요되며, 매개변수 추정결과의 일반화가 이뤄지지 않아 이 부분에 대한 추가적인 연구가 필요하다.

• Journal of the Korean Data and Information Science Society
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• v.7 no.1
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• pp.113-118
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• 1996

Principal component analysis(PCA) is an essential technique for data compression and feature extraction, and has been widely used in statistical data analysis, communication theory, pattern recognition, and image processing. Oja(1992) found that a linear neuron with constrained Hebbian learning rule can extract the principal component by using stochastic gradient ascent method. In practice real data often contain some outliers. These outliers will significantly deteriorate the performances of the PCA algorithms. In order to make PCA robust, Xu & Yuille(1995) applied statistical physics to the problem of robust principal component analysis(RPCA). Devlin et.al(1981) obtained principal components by using techniques such as M-estimation. The propose of this paper is to investigate from the statistical point of view how Xu & Yuille's(1995) RPCA works under the same simulation condition as in Devlin et.al(1981).

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.1
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• pp.71-75
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• 2001

Linear regression analyses between the electrical conductivity of the saturation-paste extract. ECe, and the electrical conductivity of the 1:5 soil extract, EC1:5, for different soils yielded different dilution factors, or slopes with significant $r^2$ values from 0.842 to 0.905. The dilution factor was inversely proportional to the cation exchange capacity of soil which reflected textural difference. The dilution factors recommended for different textural classes ranged from 6.44 for clay soil to 12.29 for sandy soil based on the CEC's of the textural classes among 350 surface soils recorded in the Taxonomical Classification of Korean Soils except volcanic ash derived soils. Though saturation percentage of the saturation-paste of the soils in this study, CEC should be taken into account for dilution factor between ECe and EC1:5, and the suggested dilution factors might be reasonable estimate for the soil textural classes.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.321-331
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• 2006

Recently, runoff characteristics of urban area are changing because of the increase of impervious area by rapidly increasing of population and industrialization, urbanization. It needs to extract the accurate topologic and hydrologic parameters of watershed in order to manage water resource efficiently. Thus, this study developed more precise input data and more improved parameter estimating procedures using GIS(Geographic Information System) and GA(Genetic Algorithm). For these purposes, XP-SWMM (EXPert-Storm Water Management Model) was used to simulate the urban runoff. The model was applied to An-Yang stream basin that is a typical Korean urban stream basin with several tributaries. The rules for parameter estimation were composed and applied based on quantity parameters that are investigated through the sensitivity analysis. GA algorithm is composed of these rules and facts. The conditions of urban flows are simulated using the rainfall-runoff data of the study area. The data of area, slope, width of each subcatchment and length, slope of each stream reach were acquired from topographic maps, and imperviousness rate, land use types, infiltration capacities of each subcatchment from land use maps, soil maps using GIS. Also we gave the management scheme of urbanization runoff using XP-SWMM. The parameters are estimated by GA from sensitivity analysis which is performed to analyze the runoff parameters.