• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.557-567
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• 2020

The six current models for estimating pan coefficient were applied to test the applicability of models in Seoul, South Korea. The models are Cuenca's model, Snyder's model, Pereira et al.'s model, Allen et al.'s model, Orang's model, and Raghuwanshi and Wallender's model. The estimated pan coefficients were compared with measured one. The measured pan coefficient was obtained by using measured pan evaporation and FAO Penman-Monteith reference evapotranspiration. Estimated evaporation by using estimated pan coefficients was compared with measured one. Furthermore, model for estimating pan coefficient in Seoul was developed. When applying 6 current models for 10 m, 15 m and 20 m fetch distances, pan coefficient estimates from Snyder's model were most similar to measured pan coefficients for all fetch distances. On the other hand, pan coefficient estimates from Pereira et al.'s model were most different from measured one. Therefore, model for estimating pan coefficient in Seoul was developed by modifying Snyder's model. When applying developed model, estimated monthly average evaporation was 92.1 mm for 10 m, 15 m and 20 m fetch distances and measured one was 91.9 mm, indicating that evaporation estimate from developed model is closest to measured one, compared with those of current models.

• The Korean Journal of Applied Statistics
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• v.4 no.1
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• pp.33-45
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• 1991

In the analysis of changepoint model the situation where single observation is taken at each time point has been considered. In an effort to extend this to the general situation, we may consider the changepoint model with more than one observation at each time point. These tests are developed without assuming any particular form for the underlying distribution, we propose the one-sided and two-sided nonparametric tests by extending the tests that have been considered in the changepoint model with single observation at each time point and obtain their asymptotic null distributions. We compare the empirical powers among the extended changepoint tests under one-sided or two-sided alternatives. We also compare the powers of the extended changepoint tests with those of the original test via the Monte Carlo simulation.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.4
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• pp.273-278
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• 2008

This study was carried out in order to test unsaturated hydraulic conductivity estimation of van Genuchten's and Campbell's models using one-step outflow method through Tempe pressure cell. The undisturbed soil cores (columns) were taken from Ap1, B1 and C horizons of Songjeong series (the fine loamy, mesic family of Typic Hapludults). After the saturated hydraulic conductivity Ks of the cores was determined by constant head method, water outflow rate and retentivity of cores were measured in Tempe pressure cell. Fitted curves by models accorded to measured data except for both end of pressure range. In near-saturated condition, measured water retention characteristics showed a relatively better fitness with Campbell's model than van Genuchten's. The soil unsaturated conductivity estimated by Campbell's model was higher than by van Genuchten's. In Ap1 and B1 horizon, the soil unsaturated conductivities obtained by one-step outflow method went between van Genuchten's and Campbell's hydraulic functions, slightly closer to van Genuchten's. In C horizon, van Genuchten's model had better fitness with the one-step outflow data. Consequently, van Genuchten's model generally had better fitness with measured hydraulic conductivity than Campbell's model at the soil water potential range of -10~-75 kPa, especially in C1 horizon. In near-saturated condition, Campbell's model could be thought as relatively accurate hydraulic model, because of the better fitness of Campbell's model with soil water retention data than van Genuchten's model.

• The Journal of Society for e-Business Studies
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• v.15 no.2
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• pp.55-75
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• 2010

The primary purposes of this study are to find a proper model for government's selections of Mainbiz and present what are the better weights of the current indexes. We prepared three sets of models：first one using original 10 variables; second one using 9principally composed variables; third one using 7 principally composed variables. Among 3 models, the last one had higher explanation power than the other two models. Therefore, if index weights are adjusted according to the third newly developed model, the credibility in evaluating and selecting Mainbiz will be improved. When transforming the index weights and running the analysis, 5 variables(organization process, marketing management, management process, production-facility states, the level of forecasting) have more direct influences than other 4 variables(innovation strategies, knowledge management, achieving level, operational level) on selecting Main-biz.

• The Korean Journal of Applied Statistics
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• v.26 no.3
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• pp.511-520
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• 2013

Detection outliers and robust estimators are crucial in regression models with outliers. In such studies the focus is on detecting outliers and estimating the coefficients using leave-one-out. Our study introduces Rice estimator which is an error variance estimator without estimating the coefficients. In particular, we study a comparison of the statistical properties for Rice estimator with and without outliers in simple regression models.

• Journal of the Korean Data and Information Science Society
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• v.20 no.2
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• pp.293-299
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• 2009

In this article, we consider linear models such as regression, ARIMA (autoregressive integrated moving average), and regression+ARIMA (regression with ARIMA errors) for predicting hourly ozone concentration level in two areas of Daegu. Based on RASE(root average squared error), it is shown that the ARIMA is the best model in one area and that the regression+ARIMA model is the best in the other area. We further analyze the residuals from the optimal models, so that we might predict the ozone warning days where at least one of the hourly ozone concentration levels is over 120 ppb. Based on the training data in the years from 2000 to 2003, it is found that 35 ppb is a good cutoff value of residulas for predicting the ozone warning days. In on area of Daegu, our method predicts correctly one of two ozone warning days of 2004 as well as all of the remaining 364 non-warning days. In the other area, our methods predicts correctly all of one ozone warning days and 365 non-warning days of 2004.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.131-140
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• 1993

A new model which requires one branch of main curves for the model calibration is developed based on the assumption that the weighting factor accounting for the pore blockage effect against air entry, $P_a({\theta})$, in Mualem's Model III-1 has a linear relation to the dimensionless pore radius r. The proposed model simulates experimental data more accurately than existing models which require one branch of main curves for the model calibration. Previous study showed that Model III-1 is the most appropriate model among domain models which require two branches of main curves for the model calibration. In comparison of the proposed model with Model III-1, both simulate hysteresis curves with almost the same accuracy. The proposed model can be applied efficiently in analyzing the unsaturated flow.

• Journal of Intelligence and Information Systems
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• v.7 no.1
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• pp.17-25
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• 2001

Tree model is the most popular classification algorithm in data mining due to easy interpretation of the result. In CART(Breiman et al., 1984) and C4.5(Quinlan, 1993) which are representative of tree algorithms, the split fur classification proceeds to attain the homogeneous terminal nodes with respect to the composition of levels in target variable. But, fur instance, in the chum prediction modeling fur CRM(Customer Relationship management), the rate of churn is generally very low although we are interested in mining the churners. Thus it is difficult to get accurate prediction modes using tree model based on the traditional split rule, such as mini or deviance. Buja and Lee(1999) introduced a new split rule, one-sided purity for classifying minor interesting group. In this paper, we compared one-sided purity with traditional split rule, deviance analyzing churning vs. non-churning data of ISP company. Also reviewing the result of tree model based on one-sided purity with some simulated data, we discussed problems and researchable topics.

• The Korean Journal of Applied Statistics
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• v.26 no.3
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• pp.471-481
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• 2013

The current VaR Model based on J. P. Morgan's RiskMetrics has problem that actual loss exceeds VaR under unstable economic conditions because the current VaR Model can't re ect future economic conditions. In general, any corporation's stock price is determined by the rm's idiosyncratic factor as well as the common systematic factor that in uences all stocks in the portfolio. In this study, we propose an One-factor VaR Model for stock portfolio which is decomposed into the common systematic factor and the rm's idiosyncratic factor. We expect that the actual loss will not exceed VaR when the One-factor Model is implemented because the common systematic factor considering the future economic conditions is estimated. Also, we can allocate the stock portfolio to minimize the loss.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2409-2421
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• 2011

This paper will present hybrid tests to a one bay-one story steel frame structure under ground excitation. A structure used in this paper for hybrid test, to evaluate performance and behavior, is divided into two models; one is numerical model with one column element, and a truss or a beam element, the other is physical substructural model with one beam-column element. All tests considered one or three degrees of freedom to implement real-time hybrid test, and two control algorithms to control hardware are used; one using MATLAB/Simulink, the other using OpenSees, OpenFresco and xPCTarget. In addition, for real-time data communication between numerical and physical substructural models SCRAMNet was used. The results of hybrid tests were compared with one of numerical analysis of numerical model with fiber force-based beam-column elements using OpenSees. Real-time hybrid tests were implemented for the validation of control system with simple structure, and then it will be extended to hybrid test for higher nonlinear or complex structure later on.