• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.129-137
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• 2000

This paper presents groundwater flow characteristics in discontinuous rock mass using fracture network program(NAPSAC) by statistical approach. Equivalent permeability coefficients are estimated from borehole data around Mabuk test tunnel site and fracture map on the arch of the tunnel. The reliability of fracture network model is obtained from determination of input data for statistical fracture network analysis from the real data(data of fracture network, data of hydraulic tests). The variation of permeability and mean anisotropic permeability coefficients are calculated from the realized model by increasing the size. As a result of analysis, a strong anisotropy of permeability is observed according to the direction of the fracture sets around the test tunnel.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.378-386
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• 2000

This paper presents groundwater flow characteristics in discontinuous rock mass using fracture network program(NAPSAC) by statistical approach. Equivalent permeability coefficients are estimated from borehole data around Mabuk test tunnel site and fracture map on the arch of the tunnel. The reliability of fracture network model is obtained from determination of input data for statistical fracture network analysis from the real data(data of fracture network, data of hydraulic tests). The variation of permeability and mean anisotropic permeability coefficients are calculated from the realized model by increasing the size. As a result of analysis, a strong anisotropy of permeability is observed according to the direction of the fracture sets around the test tunnel.

• Journal of the Korean Data and Information Science Society
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• v.20 no.2
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• pp.251-260
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• 2009

In this study, we propose a new estimation method based on autocovariance for selecting optimal estimators of the regression coefficients in the simple linear regression model. Although this method does not seem to be intuitively attractive, these estimators are unbiased for the corresponding regression coefficients. When the exploratory variable takes the equally spaced values between 0 and 1, under mild conditions which are satisfied when errors follow an autoregressive moving average model, we show that these estimators have asymptotically the same distributions as the least squares estimators. Additionally, under the same conditions as before, we provide a self-contained proof that these estimators converge in probability to the corresponding regression coefficients.

• Journal of Korea Water Resources Association
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• v.37 no.9
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• pp.759-769
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• 2004

This study proposes a new methodology to derive the areal reduction factor (ARF) using mixed probability density functions. Estimation of ARFs requires using the simultaneous rainfall data over the basin, which is rarely available in general. The new methodology Proposed in this study uses more available daily rainfall data during a given period, so the mixed probability density functions should be introduced to explain both the rainfall intermittency and variability. This study applied the mixed gamma distribution for the derivation of ARFs for the Keum river basin, and found that the new method is easier for application as well as it provides very comparable results.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.366-366
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• 2017

하천의 유량관측 자료는 지표수자원의 확보와 수공구조물의 설계를 위해 가장 기초적인 수문자료로써 정밀하고 지속적인 관측을 요구한다. 최근 유량 관측법은 접촉식 유속측정 방법의 단점을 보완한 전자파 표면유속계나 영상분석기법을 적용한 표면영상유속계(SIV)가 활용되고 있다. 이들 관측장비는 표면유속 관측법에 의해 유량을 측정하므로 보다 정밀한 유량자료를 확보하기 위해서는 측정 영역의 표면유속과 단면의 평균유속에 대한 해석이 필요하다. 이 연구에서는 제주도 남부지역에 위치한 강정천을 대상으로 2011년 7월부터 2015년 6월 까지 월 1~2회 현장관측한 ADCP 자료를 활용하여 Chiu(1987)가 제안한 2차원 유속분포식의 매개변수를 추정하여 정밀한 유량을 산정하였다. 또한 표면영상유속계(SIV)로 산정된 표면유속을 Chiu-2 차원 유속분포식에서 평균유속으로 환산하여 기존의 표면유속을 일률적으로 적용한 수심평균유속 환산계수인 0.85의 적용 값과 비교 분석하였다. 대상하천의 현장에서 72회 관측된 ADCP 자료를 활용하여 각각의 최대유속과 평균유속을 분석하고 엔트로피 계수(M)를 산정한 결과와 유속의 공간적 분포를 모델링하기 위해 제시되는 $_{urf}$를 산정하였으며, 산정된 계수 값을 이용하여 표면유속을 계산한 결과와 ADCP의 관측된 표면유속의 $^2$는 0.874로 나타났다. 이러한 결과는 Chiu-2차원 유속분포식을 연구대상하천에 적용하는 과정에서 추정되는 매개변수의 평균값 사용에 대한 타당성을 보여준다. 이 후 추정된 하천매개변수를 하천현장에 적용성 확인을 위해 강정천의 동일 관측지점에서 표면영상유속계(SIV)를 사용한 표면유속과 유량을 산정함과 동시에 ADCP에 의한 유속 및 유량과 비교 분석하였다. 표면영상유속계(SIV)로 분석된 유속 벡터를 Chiu-2차원 유속분포식에 적용하여 산정된 유량과 기존의 수심평균유속환산계수 0.85를 적용한 유량은 각각 $0.7171m^3/s$과 0$0.5758m^3/s$였다. ADCP 평균유량 $0.6664m^3/s$과의 오차율은 각각 7.63%, 13.64%로 나타나 Chiu-2차원 유속분포식을 적용한 유량이 수심평균유속환산계수 0.85를 적용한 유량에 비해 작은 오차율을 보였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.7-15
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• 2002

In this paper, the nonlinear parameter estimation method using the estimated hysteresis of each structural members was studied for the purpose of efficient seismic damage prediction and estimation of MDOF nonlinear structural model in the shaking table test. The hysteresis of each structural members can be obtained by the conversion of measured response histories into relative motions of each structural members and member forces. These hysteresis can be used to evaluate various kinds of damage indices of each structural members. The MDOF nonlinear structural model for further analysis(re-analysis) can be easily reconstructed using estimated nonlinear structural parameters of each structural members. To demonstrate the proposed techniques, several numerical and experimental example analyses are carried out. The results indicate that the proposed method can be very useful to assess local seismic damages of structures.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.543-549
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• 2001

This research estimated stream discharges indirectly by hydraulic channel routing. Only stage data from three stage stations and river cross section data were used to estimate Manning roughness coefficients and to compute stream discharges. When the discharges were estimated a stage-stage set of conditions was used for upstream-downstream boundary conditions. The research used the data from the upper Mississippi River. The hydraulic channel routings were performed by DWOPER (operational dynamic wave model). The global optimization program of SCE-UA was used to improve the roughness coefficient estimation module of the modified Newton-Raphson method in DWOPER. The results from SCE-US were better. For the case study of a flood, most estimated discharges except a few show errors within 10%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1207-1212
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• 2015

In this paper, we propose three-dimensional (3D) visualization and recognition techniques of micro-objects under photon-starved conditions using photon counting integral imaging microscopy. To capture high resolution 2D images with different perspectives in the proposed method, we use Synthetic Aperture Integral Imaging (SAII). Poisson distribution which is mathematical model of photon counting imaging system is used to extract photons from the images. To estimate 3D images with 2D photon counting images, the statistical estimation is used. Therefore, 3D images can be obtained and visualized without any damage under photon-starved conditions. In addition, 3D object recognition can be implemented using nonlinear correlation filters. To prove the usefulness of our technique, we implemented the optical experiment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.581-587
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• 2011

Reliability estimation methods using attribute data are widely used in reliability evaluation of various systems such as nuclear energy plants, food and drug, and space launch vehicles. This paper shows sensitivity analysis and comparison results of reliability estimation methods including a parametric estimation method in open literature with respect to both sample size and sampling points of time. And ways to improve accuracy of each reliability estimation method were proposed from the sensitivity analysis results.

• The Korean Journal of Applied Statistics
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• v.18 no.1
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• pp.43-56
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• 2005

In this study, a robust estimation method for the first-order autocorrelation coefficient in the time series model following AR(l) process with additive outlier(AO) is investigated. We propose the L-type trimmed least squares estimation method using the preliminary estimator (PE) suggested by Rupport and Carroll (1980) in multiple regression model. In addition, using Mallows' weight function in order to down-weight the outlier of X-axis, the bounded-influence PE (BIPE) estimator is obtained and the mean squared error (MSE) performance of various estimators for autocorrelation coefficient are compared using Monte Carlo experiments. From the results of Monte-Carlo study, the efficiency of BIPE(LAD) estimator using the generalized-LAD to preliminary estimator performs well relative to other estimators.