• The Korean Journal of Applied Statistics
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• v.34 no.6
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• pp.889-904
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• 2021

This study is a follow-up study of Kang and Kim (2020). In this study, we derive the sample influence functions of the t-statistic which were not directly derived in previous researches. Throughout these results, we both mathematically examine the relationship between the empirical influence function and the sample influence function, and consider a method to approximate the sample influence function by the empirical influence function. Also, the validity of the relationship between an approximated sample influence function and the empirical influence function is verified by a simulation of a random sample of size 300 from normal distribution. As a result of the simulation, the relationship between the sample influence function which is derived from the t-statistic and the empirical influence function, and the method of approximating the sample influence function through the empirical influence function were verified. This research has significance in proposing both a method which reduces errors in approximation of the empirical influence function and an effective and practical method that evolves from previous research which approximates the sample influence function directly through the empirical influence function by constant revision.

• Fire Science and Engineering
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• v.16 no.2
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• pp.51-58
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• 2002

For Halon-1301 regulated by Montreal Protocol and $CO_2$as its alternatives, the empirical equations of density, viscosity, and enthalpy were correlated in terms of temperature. They were obtained by regression analysis from the experimental data in the literature. The empirical equation of density was expressed as compressibility factor by the second- order function of temperature. The empirical equation of viscosity was formulated as a power function, and a correction factor was considered to cover the wider range of temperature. Finally, heat capacity as well as enthalpy were well fitted by empirical form of the second-order temperature. The correlation coefficients of the empirical equations in this work were more than 0.99.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.4
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• pp.374-383
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• 2020

At ship design stage, the maneuverability is generally estimated based on the empirical formula or the computational fluid dynamic (CFD), which is one of the numerical simulation methods. Using the hydrodynamic derivatives derived through these methods can quantitatively estimate the maneuverability of target vessels and evaluate indirect maneuverability. Nevertheless, research on estimating maneuverability is insufficient for ships not subject to IMO maneuverability standard, especially fishing vessels, and even at the design stage, the empirical formula developed for merchant ships is applied without modification. An estimation error may occur due to the empirical formula derived from the regression analysis results of a model test if the empirical formula developed for merchant ships with different hull shapes is applied to fishing vessels without any modification. In this study, the modified empirical formula that can more accurately estimate the fishing vessel's maneuverability was derived by including the hull shape parameter of target fishing trawlers in the regression analysis process that derives Kijima et al. (1990) formula. As a result, the modified empirical formula showed an average estimation error of 6%, and the result improved the average error of 49% of Kijima et al. (1990) formula developed for merchant ships.

• Fire Science and Engineering
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• v.16 no.3
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• pp.16-25
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• 2002

For Freon-23, a conventional extinguished agent regulated by Montreal Protocol and HFC-227ea, its alternative, the empirical equations were correlated in terms of saturated pressure, density, viscosity, enthalpy and surface tension. They were obtained by regression analysis from the experimental data in the literature. The empirical equations of saturated pressure were expressed as the second and third order function of temperature. The empirical equation of density was expressed as compressibility factor and saturated pressure by a function of temperature. The empirical equation of viscosity was formulated as a power function. Heat capacities as well as enthalpies were well fitted by empirical form of the second-order temperature. Finally, surface tension simply has linear function form in terms of temperature.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.76.2-76.2
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• 2010

We present the final results of our study on the mass-loss rate of donor stars in cataclysmic variables (CVs). Observed donors are oversized in comparison with those of isolated single stars of the same mass, which is thought to be a consequence of the mass loss. Using the empirical mass-radius relation of CVs and the homologous approximation for changes in effective temperature T2, orbital period P, and luminosity of the donor with the stellar radius, we find the semi-empirical mass-loss rate M2dot of CVs as a function of P. The derived M2dot is at ~10-9.5-10-10 $M\odot$/yr and depends weakly on P when P > 90 min, while it declines very rapidly towards the minimum period when P < 90 min. The semi-empirical M2dot is significantly different from, and has a less-pronounced turnaround behavior with P than suggested by previous numerical models. The semi-empirical P-M2dot relation is consistent with the angular momentum loss due to gravitational wave emission, and strongly suggests that CV secondaries with 0.075 $M\odot$ < M2 < 0.2 $M\odot$ are less than 2 Gyrs old. When applied to selected eclipsing CVs, our semi-empirical mass-loss rates are in good agreement with the accretion rates derived from the effective temperatures T1 of white dwarfs. Based on the semi-empirical M2dot, SDSS 1501 and 1433 systems that were previously identified as post-bounce CVs have yet to reach the minimal period.

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.283-300
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• 2024

Machine learning (ML) models based on artificial neural network (ANN) and decision tree (DT) were developed for estimation of axial capacity of concrete columns reinforced with fiber reinforced polymer (FRP) bars. Between the design codes, the Canadian code provides better formulation compared to the Australian or American code. For empirical models based on elastic modulus of FRP, Hadhood et al. (2017) model performed best. Whereas for empirical models based on tensile strength of FRP, as well as all empirical models, Raza et al. (2021) was adjudged superior. However, compared to the empirical models, all ML models exhibited superior performance according to all five performance metrics considered. The performance of ANN and DT models were comparable in general. Under the present setup, inclusion of the transverse reinforcement information did not improve the accuracy of estimation with either ANN or DT. With selective use of inputs, and a much simpler ANN architecture (4-3-1) compared to that reported in literature (Raza et al. 2020: 6-11-11-1), marginal improvement in correlation could be achieved. The metrics for the best model from the study was a correlation of 0.94, absolute errors between 420 kN to 530 kN, and the range being 0.39 to 0.51 for relative errors. Though much superior performance could be obtained using ANN/DT models over empirical models, further work towards improving accuracy of the estimation is indicated before design of FRP reinforced concrete columns using ML may be considered for design codes.

• Journal of Korea Water Resources Association
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• v.46 no.2
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• pp.155-169
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• 2013

This study proposes proper forms of empirical formulas for the concentration time and storage coefficient based on their theoretical backgrounds and evaluates several existing empirical formulas by comparing them with the formula proposed in this study. Additionally, empirical formulas for the concentration time and storage coefficient of the Chungju Dam basin were derived using the forms proposed by considering their theoretical backgrounds, and compared with exiting empirical formulas. The results derived are summarized as follows. (1) The concentration time of a basin is proportional to the square of the main channel length, but inversely proportional to the channel slope, as the flood flow is generally turbulent. (2) The storage coefficient is proportional to the concentration time. (3) The comparison results with existing empirical formulas for the concentration time indicates that the empirical formulas like the Kirpich, Kraven (I), Kraven (II), California DoT, Kerby, SCS, and Morgali & Linsley are in line with the form proposed in this study. Among existing empirical formulas for the storage coefficient, the Clak, Russell, Sabol and Jung are found to be well matched to this study. (4) The application results to Chungju Dam basin indicates that among empirical formulas for the concentration time, the Jung, Yoon, Kraven (I), and Kraven (II) show relatively similar results to the observed in this study, but the Rziha shows abnormal results. Among the empirical formulas for the storage coefficient, the Yoon and Hong, Jung, Lee, and Yoon show somewhat reasonable results, but the Sabol shows abnormal results. In conclusion, the empirical formulas for the concentration time and storage coefficient developed in Korea are found to reflect the basin characteristics of Korea better.

• Journal of the Korean Data and Information Science Society
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• v.17 no.2
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• pp.291-300
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• 2006

In this research, the performance of widely used Bayesian estimators such as Bayes estimator, empirical Bayes estimator, constrained Bayes estimator and constrained empirical Bayes estimator are compared by means of a measurement under balanced loss function for the typical normal-normal situation. The proposed measurement is a weighted sum of the precisions of first and second moments. As a result, one can gets the criterion according to the size of prior variance against the population variance.

• Journal of the Korean Statistical Society
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• v.28 no.4
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• pp.435-441
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• 1999

A 'convergence in probability' rate of the empirical distributions and quantiles of linear processes is obtained. As an application of the limit theorems, a trimmed mean for the location of the linear process is considered. It is shown that the trimmed mean is asymptotically normal. A consistent estimator for the asymptotic variance of the trimmed mean is provided.

• Journal of the Korean Statistical Society
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• v.32 no.2
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• pp.175-191
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• 2003

An empirical Bayesian approach is discussed for estimation of characteristics from the two-way balanced rotation sampling design which includes U.S. Current Population Survey and Canadian Labor Force Survey as special cases. An empirical Bayesian estimator is derived for monthly effect under presence of two types of biases and correlations It is shown that the marginal distribution of observation provides more general correlation structure than that frequentist has assumed. Consistent estimators are derived for hyper-parameters in Normal priors.