• 대한기계학회논문집A
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• 제25권2호
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• pp.214-219
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• 2001

In this paper, the nonlinear behavior of ultrasonic wave in partially degraded material is considered. For this aim, FDM(finite difference method) model for the nonlinear wave equation was developed with the restriction to the 1-D longitudinal wave motion and how the partial degradation in material contributes to the detected nonlinear parameter was analyzed quantitatively. In order to verify the rightness of this simulation method, the relation between the detected nonlinear parameter and the continuous distribution of degradation obtained from simulation was compared with experiment results and the simulation and experiment results showed similar tendency. It can be known from simulation result that the degree of degradation, the range of degradation and the continuous distribution of degradation have strong correlation with the detected nonlinear parameter. As it was possible in these simulations that only special part is assumed as degraded one, the quantitative evaluation of partially degraded material may be obtained by using this method.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.21-38
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• 2003

The formulation of a new bridge-vehicle system using shell with eccentric beam elements has been introduced in a companion paper (Part I). The new system takes into account of the contribution of the twisting and pitching modes of vehicles to the bridge responses. It can also be used to study the dynamic transverse load distribution of a bridge. This paper presents a parametric study on the impact induced by one vehicle or multi-vehicle running across a bridge using the proposed model. Several parameters were considered as variables including the mass ratio, the speed parameter, the frequency ratio and the axle spacing parameter to investigate their effects on the impact factor. A total number of 189 cases were carried out in this parametric study. Within the realistic range of vehicle considered, the maximum impact factors could be 2.24, 1.78 and 1.49 for bridges with spans 10 m, 20 m and 30 m respectively.

• 한국농공학회논문집
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• 제54권5호
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• pp.141-153
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• 2012

In this study, we estimated probable precipitation amounts at the target year (2020, 2030, 2040) of 55 weather stations in Korea using the 24 hour annual maximum precipitation data from 1973 through 2009 which should be useful for management of agricultural reservoirs. Not only trend tests but also non-stationary tests were performed and non-stationary frequency analysis were conducted to all of 55 sites. Gumbel distribution was chosen and probability weighted moment method was used to estimate model parameters. The behavior of the mean of extreme precipitation data, scale parameter, and location parameter were analyzed. The probable precipitation amount at the target year was estimated by a non-stationary frequency analysis using the linear regression analysis for the mean of extreme precipitation data, scale parameter, and location parameter. Overall results demonstrated that the probable precipitation amounts using the non-stationary frequency analysis were overestimated. There were large increase of the probable precipitation amounts of middle part of Korea and decrease at several sites in Southern part. The non-stationary frequency analysis using a linear model should be applicable to relatively short projection periods.

• Journal of the Korean Data and Information Science Society
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• 제25권1호
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• pp.227-235
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• 2014

In this paper, we develop the noninformative priors for the scale parameter and the shape parameter in the log-logistic distribution. We developed the first and second order matching priors. It turns out that the second order matching prior matches the alternative coverage probabilities, and is a highest posterior density matching prior. Also we revealed that the derived reference prior is the second order matching prior for both parameters, but Jerffrey's prior is not a second order matching prior. We showed that the proposed reference prior matches the target coverage probabilities in a frequentist sense through simulation study, and an example based on real data is given.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.449-450
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• 2009

위그너 분포 함수 측정을 통하여 진행하는 laser beam의 상관함수와 진행 특성들을 연구하였다. 위그너 분포 함수는 진행하는 laser beam의 total degree of coherence, beam quality parameter, 그리고 근접장 및 원거리장의 정보들을 보여준다. 위그너 분포 함수를 이용하여 공간상관 함수와 방향상관 함수를 구할 수 있으며, 이를 Schmidt mode decomposition을 이용하여 분석하면 laser beam의 보다 여러가지 특성들을 분석 할 수 있다. 이렇게 분석된 eigenmode들은 진행하는 laser beam의 보다 정확한 coherence 특성을 이해하게 해준다.

• 설비공학논문집
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• 제16권6호
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• pp.546-555
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• 2004

With circular tube heated directly or indirectly placed in a cross flow, heat flows circumferentially by conduction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube. The circumferential heat flow affects the wall temperature distribution to such an extent that in some cases. The effects of circumferential wall heat conduction on local convective heat transfer is investigated. The wall heat conduction parameter which can be deduced from the governing energy equation should be used to express the effect of circumferential heat conduction. Two-dimensional temperature distribution is presented through the numerical analysis. The comparison of one-dimensional and two-dimensional solutions is demonstrated on graph of local Nusselt numbers.

• 응용통계연구
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• 제8권1호
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• pp.159-167
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• 1995

지수족(exponential family)에 속하면서 어떤 특별한 형태를 따르는 이산분포는 그 분포함수가 정의된 정수에 대한 단봉적 순열이다. 본 논문에서 그러한 분포함수의 모수에 대한 혼합형이 어떤 조건하에서 항상 단봉적 순열을 유지하는가에 대하여 연구하였다. 그 예로써 이항분포와 포아송분포 각각에 대한 최대모수구간을 구하여, 그 모수 구간안에서의 혼합형은 항상 단봉적임을 보였다.

• 한국농공학회지
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• 제32권E호
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• pp.20-32
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• 1990

Abstract This study was conducted to pursue the normalization of frequency distribution by making an approach to the coefficient of skewness to nearly zero through the Box-Cox transformation, to get probable flood flows can be calculated by means of the transformation equation which has been derivated by Box-Cox transformation in the annual maximum series of the applied watersheds. It has been concluded that Box-Cox transfromation is proved to be more efficient than logarithmic, square root and SMEMAX transformation which is based on the trigonometric solution of a right triangle whose three verteces repesent the smallest, median and largest observed values of a population in making the coefficient of skewness nearer to zero. Consequently it is shown that probable flood flows according to the return period based on Box-Cox transformation are closer to the observed data as compared to other methods including SMEMAX transformation and fitted probability distributions such as the three parameter lognormal and the type I extremal distribution for the applied watersheds.

• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2005년도 추계학술대회
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• pp.13-26
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• 2005

In this paper, we derive the approximate maximum likelihood estimators of the scale parameter and location parameter of the exponential distribution based on multiply Type-II censored samples. We compare the proposed estimators in the sense of the mean squared error for various censored samples. We also obtain the approximate maximum likelihood estimator (AMLE) of the reliability function by using the proposed estimators. And then we compare the proposed estimators in the sense of the mean squared error.

• Journal of the Korean Data and Information Science Society
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• 제18권4호
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• pp.1081-1091
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• 2007

In this paper, we derive the approximate maximum likelihood estimators of the scale parameter and location parameter in an exponentiated logistic distribution based on multiply Type-II censored samples. We compare the proposed estimators in the sense of the mean squared error for various censored samples. We also propose and compare the estimators of the reliability function by using the proposed estimators of the parameters.