• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1115-1122
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• 2013

Recently the demands for traffic information tend to increase, and travel time might one of the most important traffic information. To effectively estimate exact travel time, highly reliable traffic data collection is required. BIS(Bus Information System) data would be useful for the estimation of the route travel time because BIS is collecting data for the bus travel time on the main road of the city on real-time basis. Traditionally use of BIS data has been limited to the realm of bus operating but it has not been used for a variety of traffic categories. Therefore, this study estimates a route travel time on road networks in urban areas on the basis of real-time data of BIS and then eventually constructs regression models. These models use an explanatory variable that corresponds to bus travel time excluding service time at the bus stop. The results show that the coefficient of determination for the constructed regression model is more than 0.950. As a result of T-test performance with assistance from collected data and estimated model values, it is likely that the model is statistically significant with a confidence level of 95%. It is generally found that the estimation for the exact travel time on real-time basis is plausible if the BIS data is used.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.745-750
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• 2004

The objective of this collaborative study was to establish a Korean standard of Japanese encephalitis (JE) vaccine (mouse brain-derived, formalin-inactivated) for potency assay. A candidate preparation proposed as a Korean standard was provided by GreenCross Vaccine, and six laboratories, including one national control laboratory and five manufacturers of JE vaccine, participated in the study. The potency of the candidate preparation and a reference standard obtained from Japan was estimated by mouse immunogenicity assay using the in vitro plaque reduction neutralization test (PRNT). The results of 72 assays conducted by the 6 laboratories showed that the overall mean potency estimate of the candidate preparation was 2.455 log median plaque reduction neutralization antibody titer per 0.5-ml dosage administered twice in mice at 7-day intervals, and that the mean potency ratio of the candidate preparation relative to the reference standard was 1.074. The potency estimates were quite variable among laboratories irrespective of the preparation. The variability of assays assessed by Z scores and coefficient of variation (CV) were in general within the level of acceptance (Z scores within $\pm3$ and $CV\;\leq\;15%$). Therefore, we concluded that the candidate preparation would be suitable as a national standard for testing the potency of JE vaccine (inactivated).

• Journal of Korean Society of Transportation
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• v.20 no.6
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• pp.45-56
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• 2002

In this research we estimated regional gross fixed capital stock of transport sector, such as road railroad, airport and seaport during 1968-1997 in Korea. We also compared our estimation results with those of Korea and Japan. As basic analytic method, we used the regional allocation method. To estimate regional gross fixed capital stock of transport sector, we used the basic data on national wealth surveys in 1997, regional land price index and regional facilities index in transport sectors. We used the most reasonable data in the process of estimation after reviewing the collected data In order to get the reasonable capital stock by regions. we chose the allocation index which can minimize the difference between the estimated result and the real regional capital stock in the process to allocate the total gross capital into the regions. Compared our results with those of other researches in Korea, estimates in our research project could be said more accurate than those.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.1
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• pp.83-93
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• 2020

East Asia, which includes China, Japan, Korea, and Mongolia, is highly impacted by hydroclimate extremes such drought, flood, and typhoon recent year. In 2017, more than 18.5 million hectares of crops have been damaged in China, and Korea has suffered economic losses as a result of severe drought. Satellite-derived rainfall products are becoming more accurate as space and time resolution become increasingly higher, and provide an alternative means of estimating ground-based rainfall. In this study, we verified the availability of rainfall products by comparing widely used satellite images such as Climate Hazards Groups InfraRed Precipitation with Station (CHIRPS), Global Precipitation Climatology Centre (GPCC), and Precipitation Estimation From Remotely Sensed Information Using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) with ground stations in East Asia. Also, the satellite-based rainfall products were used to calculate the Standardized Precipitation Index (SPI). The temporal resolution is based on monthly images and compared with the past 30 years data from 1989 to 2018. The comparison between rainfall data based on each satellite image products and the data from weather station-based weather data was shown by the coefficient of determination and showed more than 0.9. Each satellite-based rainfall data was used for each grid and applied to East Asia and South Korea. As a result of SPI analysis, the RMSE values of CHIRPS were 0.57, 0.53 and 0.47, and the MAE values of 0.46, 0.43 and 0.37 were better than other satellite products. This satellite-derived rainfall estimates offers important advantages in terms of spatial coverage, timeliness and cost efficiency compared to analysis for drought assessment with ground stations.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.318-329
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• 2011

This study focuses on enhancing the accuracy of consumption function of Korean natural gas for city gas. It is using time-series model with time-varying coefficients taking into account the recent abnormal temperature phenomenon and the changing gross domestic product (GDP) as important variables. This study estimates the cointegrating regression model for the long-run estimation and the error correction model for the short-run estimation. The consumption function of Korean natural gas is estimated to be influenced by the time-varying coefficients of GDP and temperature. Using the estimated time-series model with time-varying coefficients, this study forecasts the consumption of natural gas for city gas from July 2011 to December 2012. The consumption in 2011 would be 18,303 thousand tons, which is little different from the imported 18,681 thousand tons. The consumption of natural gas for city gas in 2012 is forecast to be 19,213 thousand tons. The consumption model of this study is needed to extend by considering the relative prices between natural gas and its substitutes, the scale of consumers and others.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.4
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• pp.232-237
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• 2010

While global solar radiation is an essential input variable in crop models, the observation stations are relatively sparse compared with other meteorological elements. Instead of using measured solar radiation, the Angstrom-Prescott model estimates have been widely used. Monthly data for solar radiation and sunshine duration are a convenient basis for deriving Angstrom-Prescott coefficients (a, b), but it is uncertain whether daily solar radiation could be estimated with a sufficient accuracy by the monthly data - derived coefficients. We derived the Angstrom-Prescott coefficients from the 25 years observed global solar radiation and sunshine duration data at 18 locations across South Korea. In order to figure out any improvements in estimating daily solar radiation by replacing monthly data with daily data, the coefficients (a, b) for each month were derived separately from daily data and monthly data. Local coefficients for eight validation sites were extracted from the spatially interpolated maps of the coefficients and used to estimate daily solar radiation from September 2008 to August 2009 when, pyranometers were operated at the same sites for validation purpose. Comparison with the measured radiation showed a better performance of the daily data - derived coefficients in estimating daily global solar radiation than the monthly data - derived coefficients, showing 9.3% decrease in the root mean square error (RMSE).

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.229-237
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• 2019

This study was conducted to estimate annual reference evapotranspiration (ET₀) for the agro-climatic zones for rice paddy fields in South Korea between 1980 and 2015. The daily ET₀ was estimated by applying the Penman-Monteith method to meteorological data from 61 weather stations provided by Korean Meteorological Administration (KMA). The average of annual ET₀ from 1980 to 2015 was 1334.1±33.89 mm. The ET₀ was the highest at the Southern Coastal Zone due to their higher air temperature and lower relative humidity. The ET₀ had significantly increased with 2.81 mm/yr for the whole zones over 36 years. However, the change rate of it was different among agro-climatic zones. The annual ET₀ highly increased in central zones and eastern coastal zones. In terms of correlation coefficient, the temporal change of the annual ET₀ was closely related to variations of four meteorological factors (i.e., mean, minimum temperatures, sunshine duration, and relative humidity). The results demonstrated that whole Korean agro-climatic zones have been undergoing a significant change in the annual ET₀ for the last 36 years. Understanding the spatial pattern and the long-term variation of the annual ET₀ associated with global warming would be useful to improve crop and water resource managements at each agro-climatic zone of South Korea.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.5
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• pp.385-392
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• 2013

The finite element method has become the most widely used method of structural analysis and recently, the method has often been applied to complex dynamic and nonlinear structural analyses problems. Even for these complex problems, where the responses are hard to predict, finite element analyses yield reliable results if appropriate element types and meshes are used. However, the dynamic and nonlinear behaviors of a structure often include large deformations in various portions of the structure and if the same mesh is used throughout the analysis, some elements may deform to shapes beyond the reliable limits; thus dynamically adapting finite element meshes are needed in order for the finite element analyses to be accurate. In addition, to satisfy the users requirement of quick real run time of finite element programs, the algorithms must be computationally efficient. This paper presents an adaptive finite element mesh generation scheme for dynamic analyses of structures that may adapt at each time step. Representative strain values are used for error estimates and combinations of the h-method(node movement) and the r-method(element division) are used for mesh refinements. A coefficient that depends on the shape of an element is used to limit overly distorted elements. A simple frame example shows the accuracy and computational efficiency of the scheme. The aim of the study is to outline the adaptive scheme and to demonstrate the potential use in general finite element analyses of dynamic and nonlinear structural problems commonly encountered.

• Journal of Korea Water Resources Association
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• v.35 no.2
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• pp.161-171
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• 2002

It has been known that the accurate estimates of 2-dimensional water quality model parameters are difficult for non-experts due to the complexity of theoretical background and input requirement and complicated inter-relationship between model Parameters. The main goal of this study is to Provide expert system for the optimal estimation of water quality model parameters, which is based on the development of chaining mechanism according to the sensitivity analysis of model parameter interactions and GUI interface system on ArcView Avenue. The selected study area is the 35.3- km main Han river starting from Paldang Dam site to the Point of Indo bridge and the tributary inflows including pollutant data are used for the system application and validation. The estimated main model parameters are 0.367 for transverse dispersion coefficient, 0.074 for and 0.162 for. It also shows that the simulated water quality constituents such as DO and BOD based on the estimated model parameters are well agreed with the observed ones. It can be concluded that the developed GIS-based expert system for water quality model parameter estimation and graphical representation of water quality analysis is useful for the scientific water quality management.

• Journal of the Economic Geographical Society of Korea
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• v.12 no.4
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• pp.627-644
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• 2009

In the knowledge-based economy highlighting the importance of human capital, there has been a growing interest in human capital externalities as a fundamental engine of growth and development of a region. The purpose of this study is to analyze human capital externalities using 3-level hierarchical linear model(3-HLM), decomposing determinants of wages into three levels involving workers(level-1) nested within firms(level-2) nested within regions(level-3). This study separately estimates the effect of the average education level on the wages by three different schooling groups on the assumption that the intensity of knowledge spillovers varies with each group's schooling level. The main results are as follows; First, the coefficient of the average education level of a region shows 0.044, indicating that one-year increase in the average level of schooling could increase average individual earnings by 4.4%. Secondly, the external effects of human capital on three different schooling groups are considerably different, raising less than high school graduates' wages by 3.0%, college graduates' wages by 4.7%, and graduate schools' wages by 11.8%, respectively. Thirdly, well educated workers are much more sensitive to the variation of the regional education level than less educated ones when we apply the shares of each schooling group as alternative measures for the average level of education. Such findings of this study draw an implication that local governments could speed up regional economic growth in the knowledge-based economy by not only raising total human capital stock in a region but building the close networks that promote productivity-enhancing human capital external effects.