• Journal of Korean Society of Forest Science
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• v.103 no.3
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• pp.383-391
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• 2014

Long-term changes in the hydrological characteristics of a small forest watershed were examined using a master baseflow recession curve and the measured rainfall-runoff data from the experimental forest watershed in the measured years 2003-2011. The results of the study showed that the recession coefficient of direct runoff was lower than that of baseflow. In small forested watershed, the direct flow was lower than that of large scale watershed, flow due to its shorter period of occurrence. And baseflow was similar to large scale watershed's. A regression equation $y=0.7528e^{-0.022x}$($R^2=0.8938$, range 0.3~0.8 mm) was obtained using the master baseflow recession curve for the study period and the recession coefficient was calculated as K = 0.978. Changes between master baseflow recession curve and runoff showed great association and relevance such as increasing runoff was associated with the gentle slope of master baseflow recession curve and decreasing runoff was associated with the slope of master baseflow recession curve contrary. In the later years of the study period, the slope of the master baseflow recession curve appreciably became more gentle due to increases in baseflow. This suggests that the forested experimental watershed exhibit improved structural functioning of normal flood control and reduced occurrence of water shortage problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.174-177
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• 2007

In this paper the noise characteristics of metro train is investigated experimentally. It is primarily aimed at observing the squealing noise radiation of each wheel when the vehicle pass the curve sections. This will be used to understand the noise excitation mechanism at the contact area between squealing wheels and rails which induce squeal noise at curve sections. To identify the related key parameters and boundary conditions on-board monitorings of the noise, vibration of the wheel and bogie and displacement behaviour of the wheels and rails have been done. In this paper only noise measurement and results are discussed. From spectrogramms squeal noise due to creepage and noise due to flange contact of the wheels could be identified. At the moment of the curve passing the highest squeal levels are found on the front inner wheel. However since curve noise depends on variable factors more analyses will be followed to identify the squealing wheels and the noise excitation.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.578-582
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• 2005

In this study, the conceptual foundation and development process of the Antecedent soil Moisture Condition(AMC) in SCS runoff curve number method are reviewed. Although the runoff volume is very sensitive with AMC condition, the AMC class limits developed in SCS(1972) are used in rainfall-runoff analysis without careful consideration. Tn this study, following the SCS curve number development process, rainfall-runoff characteristics of the Jang-Pyung subbasin subject to the Pyung-Chang River basin are analyzed to evaluate the reasonability of the AMC class limits at present. The New AMC class limits are proposed by the sensitive analysis of the antecedent rainfall - curve number value. As a result, the classification value of AMC-I with II is 22mm of antecedent 5-day rainfall amount, and the classification of AMC-II with III is 117mm in growing season. When the New AMC class limits are applied to Jang-Pyung subbasin, AMC probability distribution shows that the AMC-II has increased remarkably even though the AMC-I has a little higher value. But the AMC-III has the smallest one. According to the conceptual basis of the curve number method, the AMC probability distribution, the New AMC class limits adopted, gives reasonable results.

• The Korean Journal of Applied Statistics
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• v.27 no.3
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• pp.445-459
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• 2014

As a certain job is repeatedly done by a worker, the outcome comparative to the effort to complete the job gets more remarkable. The outcome may be the time required and fraction defective. This phenomenon is referred to a learning-curve effect. We focus on the parametric modeling of the learning-curve effects on count data using a logistic cumulative distribution function and some probability mass functions such as a Poisson and negative binomial. We conduct various simulation scenarios to clarify the characteristics of the proposed model. We also consider a real application to compare the two discrete-type distribution functions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1782-1790
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• 2012

In this paper, a methodology to use load duration curve and the reactive power factor sensitivity of generation cost is proposed for analyzing the effects of load power factor effectively. A great deal of cases of power systems are classified into several patterns according to the characteristics using load duration curve, and the overall effects of load power factor are assessed by integrating the analysis results of load power factor in all the patterns. The reactive power sensitivity of generation cost and the integrated costs such as generation cost, investment cost, voltage variation penalty cost and CO2 emission cost are used for determining an appropriate load power factor. A systematic procedure for effective analysis of load power factor is presented. It is shown through the application to the practical power system of KEPCO(Korea Electric Power Corporation)that the effects of load power factor can be analyzed effectively using load duration curve and reactive power factor sensitivity.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.1
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• pp.22-30
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• 1999

This paper presents an efficient algorithm to estimate the maximum load level for heavily loaded power systems with the load-generation vector obtained by ELD (Economic Load Dispach) and/or short term load forecasting while utilizing the elliptic pattern of the P-e curve. It is well known the power flow equation in the rectangular corrdinate is jully quadratic. However, the coupling between e and f makes it difficult to take advantage of this quadratic characteristic. In this paper, the elliptic characteristics of P-e curve are illustrated and a simple technique is proposed to reflect the e-f coupling effects on the estimation of maximum loadability with theoretical analysis. An efficient estimation algorithm has been developed with the use of the elliptic properties of the P-e curve. The proposed algorithm is tested on IEEE 14 bus system, New England 39 bus system and IEEE 118 bus system, which shows that the maximum load level can be efficiently estimated with remarkable improvement in accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3573-3578
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• 2015

Transition curves are located between curve and straight section in railway. These transition curves are vulnerable to the ride comfort of passengers and safety of a vehicle because lateral acceleration, lateral jerk and roll velocity increase as curvature and cant change along the transition curves. In this paper, ride comfort on the transition curve was calculated on the basis of lateral acceleration and roll velocity measurements. The evaluation of ride comfort was conducted according to the methodology specified in European Standard. The distribution characteristics of the comfort index were investigated for the korean conventional line from the evaluation results. The influence of the curve radius and the vehicle speed on the ride comfort index was also investigated. Finally, the relationship between ride comfort and the rate of cant changes on transition curves was analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.17-26
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• 2021

It is challenging to estimate the fatigue life of construction equipment consisting of a welded joint using field structure test owing to the uncertainty of the S-N curve. IIW recommends different S-N curves for various welded joint types. However, there is no way to define an appropriate curve considering complex design shape and strain gauge characteristics. This paper proposes an equivalent S-N curve method based on the relationship between IIW effective notch stress and virtual stress using finite element analysis. Moreover, a case study was conducted for the excavator fuel tank. The proposed method is expected to enhance accuracy and consistency in calculating the fatigue life for the welded structure of construction equipment.

• Korean Journal of Social Welfare Studies
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• v.44 no.2
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• pp.169-199
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• 2013

This study has a purpose to analyze trajectories of life satisfaction of the elderly after their retirement and how the characteristics of individual, retirement and family relationship have an effect on the life satisfaction. This study has investigated the Korean elderly, who had been retired, using the data from three waves(1st wave(2005)~3rd wave(2009) of the Korean Retirement and Income Panel(KReIS). Data analysis has been used to identify the predictors of the intercept and slope related to the life satisfaction after retirement, focusing the trajectories of the life satisfaction after retirement and individual characteristics, retirement characteristics and family relationship with application of the growth curve model by Amos 20.0. First, the intercept of the life satisfaction after retirement was somewhat below average. Life satisfaction averagely increased little by little from 1st wave to 3rd wave. Second, by conducting the conditional growth curve model, the study revealed that the intercept of the life satisfaction after retirement is high on individual characteristics(sex, educational level, income, health status) and in retirement characteristics(voluntary retirement) and satisfaction with family relationship and married life). Furthermore, health status, voluntary retirement, and satisfaction with family relationship asserted the meaningful variables in the slope of life satisfaction after retirement.

• Journal of the military operations research society of Korea
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• v.8 no.1
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• pp.34-50
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• 1982