• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.261-268
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• 2004

Corrosion of reinforcement is the main cause of damage and early failure of reinforced concrete structures. The corrosion is mainly progressed by the chloride ingress. In this paper, an experimental study is executed to investigate the effect of concrete properties and testing methods on the coefficients of chloride diffusion. Also, it is surveyed the relationship between total chloride and free chloride in concrete. According to this experiment results, W/C ratio and testing method affect chloride diffusion coefficient of concrete. As W/C ratio is increased, diffusion coefficient in concrete is also increased. Diffusion coefficient obtained by each testing method show the different values, respectively. The model equation of diffusion coefficient with W/C ratio is proposed.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.75-81
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• 1999

This paper presents in the rrethod power demand estimated of consuming facility algorithm using orthogonal polynomial regression rmdel. Estimation rmdel presented can use mathematical rrethod consists. of extrapolation and correlation rrethod, Computation tirre and capacity of presented rmdel was rmre economic than multiple regression rrodel because low-order equation can use in the high-order equation without sorre correction, and vice-versa. Therefore this rmthed can be very usefulness rmthed in the power demand estimation Fourth-order rrodel was very good armng this rrodel that was coJTJp)Sed the estimation rmdel of second, third and fourth-order. Power demand estimated result of consuming facility using correlation rrethod was good in the percentage error of about 2[%1 Also It was to verify efficiency and awroPJiation the estimated rmdel that estimation percentage error was about 1[%] in the oower demand estimated result of 1997.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.43-52
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• 2003

Two methods which estimate manoeuvring derivatives in the model of hydrodynamic force and moment acting on a manoeuvring ship using sea trial data were compared. One is the widely used parameter estimation method by using the Extended Kalman Filter (EKF), which estimates state variables of linearized state space model at every instant after dealing with the coefficients as the augmented state variables. The other one is the Estimation-Before-Modeling (EBM) technique, so called the two-step method. In the first step, hydrodynamic force of which dynamic model is assumed the third-order Gauss-Markov process is estimated along with motion variables by the EKF and the modified Bryson-Frazier smoother. Then, in the next step, manoeuvring derivatives are identified through the regression analysis. If the exact structure of hydrodynamic force could be known, which was an ideal case, the EKF method would be regarded as being more superior compared to the EBM technique. However the EBM technique was more robust than the EKF method from a realistic point of view where the assumed model structure was slightly different from the real one.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.65-76
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• 2009

Little attention has been paid to Brazilian test for the estimation of uniaxial compressive strength and elastic modulus of rocks as an indirect method despite high availability of civil engineering parameters. This paper employed Brazilian test value to estimate two parameters of igneous rocks (granite, andesite, rhyolite) of Korea. High reliability of Brazilian test has been supported by the conclusions drawn from point load test and Schmidt hammer strike values. It has also been found that this method can be applied easily and rapidly to the estimation of uniaxial compressive strength and elastic modulus of rock cores when direct tests are not available.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1918-1923
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• 2009

결정질 암반에서 지하수의 수리적 특성을 파악하기 위해 수행되고 있는 수리시험 방법은 정률법, 정압법, 순간주입(회복)법 등 세 가지로 구분할 수 있다. 본 연구에서 다루는 정압주입시험 (Constant Head Injection Test, CHIT)은 위의 정압법의 한 종류로 토목공학, 지질공학 분야에서 대상 구간의 투수계수 추정을 위해 널리 쓰이는 수리 시험이며, 이는 단일 패커나 이중패커를 이용하여 시험 구간을 격리하고, 격리된 구간에 일정한 압력으로 물을 주입하여 주입되는 물의 양을 파악함으로써, 시험 구간의 수리전도도(Hydraulic conductivity)를 산출하는 전통적인 수리시험이다. 본 연구에서는 수치실험을 통해 시험 구간 및 주입 압력의 크기 등 인위적인 요인에 의해 도출되는 투수계수가 어떻게 달라지는지에 대해 평가해 보았다. 일반적으로 단열 암반에서 수행한 정압주입시험의 해석에 있어 매질을 균질, 등방성 다공질이라는 가정으로 구간별 투수량계수를 산출하기 때문에, 다공성 매질의 지하수 유동을 모사하는 MODFLOW를 수치모사 코드로서 이용하였다. 시험구간의 크기 및 주입압력에 대한 민감도 분석 결과, 시험구간의 크기에 상관없이 수치모의에서 입력한 수리전도도 값에 비해 낮은 수리전도도 값이 산출되었으며, 주입 압력이 클수록 산출되는 수리전도도 값이 매질의 수리전도도 값과 차이가 났다. 민감도 분석 결과 현장수리시험에서 정압 주입시험에 의한 구간별 수리전도도 산출함에 있어 시험구간의 크기와 주입 압력 값에 대하여 고려해야 한다고 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.235-244
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• 2021

This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.98-102
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• 2012

These days, Uncooled IR Systems are more popular in the area of defense and aerospace than before. Uncooled IR Systems are widely used as core technology for making unmanned systems and detecting enemy objects during the day and night in the distance. Recently, researches on TEC-less IRFPA have been increased to minimize the power consumption and to make a smaller system than before. For this, it needs to find adequate NUC(Non-Uniformity Correction) coefficients as FPA(Focal Plane Array) temperature changes. In this paper, we propose a new NUC coefficient estimating technique, DCCE-LI(Dynamic Calibration Coefficients Estimation with Linear Interpolation), for TEC-less IRFPA. It is based on a linear interpolation method and it can estimate NUC coefficients in real-time. So, by testing and evaluating it with some IR images, we conclude that the quality of IR images using proposed method is better than applying static coefficients.

• The Journal of the Acoustical Society of Korea
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• v.17 no.3
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• pp.90-95
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• 1998

본 논문에서는 CHMM인 CDHMM과 ARHMM을 이용하여 화자적응화 하는 방법을 각각 연구하였다. CDHMM에서는 최대사후화확률 추정법에 의하여 각 상태마다 하나의 가 지를 이용하여 화자에 적응시킨다. 본 논문에서는 음성의 다양한 음향학적 특징을 표현하기 위하여 상태마다 여러 개의 가지를 갖는 방법을 제안하였다. 상태마다의 적절한 가지 수를 결정하기 위하여 각 상태에 속하는 프레임 수와 특징 벡터들의 분산행렬의 행렬식값을 이용 하였다. ARHMM에서는 특징벡터로 선형예측계수를 사용하기 때문에 최대사후화확률 추정 법을 사용할 수 없게 된다. 따라서 화자독립모델을 이용하여 적응화자에 대한 음성을 Viterbi 알고리듬으로 상태별로 분할한 후 k-means 알고리듬을 이용하여 각 상태마다 하나 의 가지를 갖는 모델로 적응시키는 방법을 제안하였다.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1047-1061
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• 2015

Stratified random sampling is a powerful sampling strategy to reduce variance of the estimators by incorporating useful auxiliary information to stratify the population. Sample allocation is the one of the important decisions in selecting a stratified random sample. There are two common methods, the proportional allocation and Neyman allocation if we could assume data collection cost for different observation units equal. Theoretically, Neyman allocation considering the size and standard deviation of each stratum, is known to be more effective than proportional allocation which incorporates only stratum size information. However, if the information on the standard deviation is inaccurate, the performance of Neyman allocation is in doubt. It has been pointed out that Neyman allocation is not suitable for multi-purpose sample survey that requires the estimation of several characteristics. In addition to sampling error, non-response error is another factor to evaluate sampling strategy that affects the statistical precision of the estimator. We propose new sample allocation methods using the available information about stratum response rates at the designing stage to improve stratified random sampling. The proposed methods are efficient when response rates differ considerably among strata. In particular, the method using population sizes and response rates improves the Neyman allocation in multi-purpose sample survey.