• Journal of Korean Society of Transportation
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• v.34 no.3
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• pp.222-233
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• 2016

Recently, mobile phone data was applied in travel demand modeling as a new source of dynamic population movement. This study is also aimed to estimate "occupancy population" during a given period of time within a given spatial region using mobile phone data. An occupancy population was defined as the number of people residing or moving within a given time and space. In case of Seoul Metropolitan area, we divided the area into a number of administrative districts as zones for analysis and estimated the occupancy population of each zone by mobile phone data collected by SK telecom Co., a wireless telecommunication provider in Korea. For the expansion of mobile phone data, a new concept of "communication probability" was introduced and applied in the estimation of occupancy population of each zone by the hour. We compared the estimated number with the daytime population and the daytime population index referred by the Statistics Korea. The results showed that a positive correlation existed between the estimated number and the statistical number by nationwide survey. It was concluded that mobile phone data could be more cost-effective sources than a conventional survey method to estimate the pattern of population movement by the hour or by the day.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.9
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• pp.629-640
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• 2014

In this study, the applicability of dynamic water quality model to TMDL system was examined, methods for setting of water quality goal and estimation of allocation loads were suggested and results of applying these methods were analyzed. HSPF model was applied for Miho stream basin as a dynamic water quality model. The model was calibrated using measurement data obtained in 2009~2010 and showed satisfactory performance in predicting daily variations of flow rate and BOD concentration. Methods for TMDL application were categorized into 3 cases; water quality management (1) considering low flow condition(Case I), (2) considering entire period of the year (Case II) and (3) considering the worst water quality condition (Case III). BOD water quality goals at the end of Miho stream watershed increased in the order of Case IICase I>Case III. If further researches on base precipitation and method for model input of nonpoint source pollutant were carried out, water quality could be managed more reasonably and scientifically by applying dynamic water quality model to TMDL. The result of this study is expected to be used as primary data for TMDL using dynamic water quality model.

• Journal of Radiation Protection and Research
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• v.22 no.3
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• pp.207-218
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• 1997

Purpose: The objective of this study is to develop an algorithm for estimation of tumor dose using measured transmission dose as a part of the development of on-line dosimetry system. Materials and Methods: Data of transmission dose were measured under various FS, Tp and PCD with a special water phantom for 6 MV and 10 MV X-ray. SCD (source-chamber distance) was set to 150 cm. Measurements were conducted with a 0.125 cc ion chamber. Results: Using measured data and regression analysis, two algorithms were developed for estimation of expected reading for measured data. Algorithm 1 consisted of the quadratic function of PCD and the tertiary function of AlP (area-perimeter ratio). Algorithm 2 consisted of the tertiary function of log(A/P)and the tertiary function of PCD. Algorithm 2 required less data set and was more accurate in comparing expected and observed dose. Conclusion: Using the algorithm developed, transmission dose can be estimated for any exposure condition, i.e. any given Tp, PCD and FS with high accuracy. To complete this algorithm, further developments are needed regarding the beam modifying device, the tissue inhomogeneity and the irregular body surface.

• Korean Journal of Construction Engineering and Management
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• v.16 no.1
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• pp.119-128
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• 2015

Domestic dominant method in subcontract cost estimate for comprehensive program management is estimation by referencing similar cases or relying on the experience and expertise of the engaged. However, this method is not reliable due to lack of accuracy, making it harder for clients to plan and budget the program. Since budget itself is roughly estimated, it becomes a source of cost rise in the course of management due to design modifications. Therefore, the client and service providers shall calculate more accurate service cost by applying objective and scientific method in order to minimize cost rise and cost related dispute. Traditional cases, in estimating program management cost, took Top-Down approach based on precedents and experience. On the contrary, this study will categorize management structure into phases and activities, issue WBS for each phase to estimated schedule and cost for each code, and take Bottom-UP approach. By taking this approach named ICEP (Integrated Cost Estimate based on Project), Set project typical model will be developed for service cost estimating, calculate cost by applying project-specific factors. Also, by analyzing progress data and allocated management cost to complement them, more efficient construction management will take shape based on program management cost standards which reflect project-specific features.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.392-400
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• 2001

This paper proposes an illuminant estimation algorithm that estimates the spectral power distribution of an incident light source from a single image. The proposed illumination recovery procedure has two phases. First, the surface spectral reflectances are recovered in the maximum achromatic region (MAR) which is the most achromatic and highly bright region of an image after removing partially the effect of illumination using a modified gray world algorithm. Here, the surface reflectances of MAR are estimated using the principal component analysis method along with a set of given 1269 Munsell samples. Second, the Population of reflected lights is determined with 1269 Munsell samples and a set of illuminations then the spectral distribution of re(looted lights of MAR is selected from the spectral database. That is, color differences are compared between the reflected lights of the MAR and the spectral database, which is the set of reflected lights built by the given set of Munsell samples and illuminants. Then the closest colors from the spectral database are selected. Finally, the illuminant of an image can be calculated dividing the average spectral distributions of reflected lights of MAR by the average surface reflectances of the MAR. In order to evaluate the proposed algorithm, experiments with artificial scenes, which are exposed to chromatic illuminants, were performed and the spectral distribution of estimated illumination and color difference are compared with results of the conventional method.

• The Korean Journal of Financial Management
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• v.26 no.4
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• pp.191-234
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• 2009

This study examined on the volatility feedback hypothesis through the use of threshold GARCH-in-Mean (GJR-GARCH-M) model developed by Glosten, Jaganathan, and Runkle (1993) in the stock markets of 14 emerging countries during the period of January, 1996 to May, 2009. On this study, I found successful evidences which can support the volatility feedback hypothesis through the following three estimation procedures. First, I found relatively strong positive relationship between the expected market risk premiums and their conditional standard deviations from the GARCH-M model in the basis of daily return on each representative stock market index, which is appropriate to investors' risk-averse preferences. Second, I can also identify the significant asymmetric time-varying volatility originated from the investors' differentiated reactions toward the unexpected market shocks by applying the GJR-GARCH-M model and further find the lasting positive risk aversion coefficient estimators. Third, I derived the negative signs of the regression coefficient of unpredicted volatility on the stock market return by re-applying the GJR-GARCH-M model after I controlled the positive effect of predicted volatility through including the conditional standard deviations from the previous GARCH-M model estimation as an independent explanatory variable in the re-applied new GJR-GARCH-M model. With these consecutive results, the volatility feedback effect was successfully tested to be effective also in the various emerging stock markets, although the leverage hypothesis turned out to be insufficient to be applied to another source of explaining the negative relationship between the unexpected volatility and the ex-post stock market return in the emerging countries in general.

• Journal of Radiation Protection and Research
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• v.38 no.1
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• pp.22-28
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• 2013

The skyshine effect is an essential and important phenomenon in the shielding design of the high energy accelerator. In this study, a new estimation method of neutron skyshine was proposed and was verified by comparison with existing methods. The effective dose of secondary neutrons and photons at the locations that was far away from high-energy electron accelerator was calculated using FLUKA and PHITS Monte Carlo code. The transport paths of secondary radiations to reach a long distance were classified as skyshine, direct, groundshine and multiple-shine. The contribution of each classified component to the total effective dose was evaluated. The neutrons produced from the thick copper target irradiated by 10 GeV electron beam was applied as a source term of this transport. In order to evaluate a groundshine effect, the composition of soil on the PAL-XFEL site was considered. At a relatively short distance less than 50 m from the accelerator tunnel, the direct and groundshine components mostly contributed to the total effective dose. The skyshine component was important at a long distance. The evaluated dose of neutron skyshine agreed better with the results using Rindi's formula, which was based on the experimental results at high energy electron accelerator. That also agreed with the estimated dose using the simple evaluation code, SHINE3, within about 20%. The total effective dose, including all components, was 10 times larger than the estimated doses using other methods for this comparison. The influence of multiple-shine path in this evaluation of the estimation method was investigated to be bigger than one of pure skyshine path.

• Journal of the Korean association of regional geographers
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• v.22 no.1
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• pp.251-266
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• 2016

Intelligent interpolation methods such as dasymetric mapping are considered to be the best way to disaggregate zone-based population data by observing and utilizing the internal variation within each source zone. This research reviews the advantages and problems of the dasymetric mapping method, and presents a geographically weighted regression (GWR) based method to take into consideration the spatial heterogeneity of population density - land cover relationship. The locally adaptive intelligent interpolation method is able to make use of readily available ancillary information in the public domain without the need for additional data processing. In the case study, we use the preclassified National Land Cover Dataset 2011 to test the performance of the proposed method (i.e. the GWR-based multi-class dasymetric method) compared to four other popular population estimation methods (i.e. areal weighting interpolation, pycnophylactic interpolation, binary dasymetric method, and globally fitted ordinary least squares (OLS) based multi-class dasymetric method). The GWR-based multi-class dasymetric method outperforms all other methods. It is attributed to the fact that spatial heterogeneity is accounted for in the process of determining density parameters for land cover classes.

• Particle and aerosol research
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• v.16 no.1
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• pp.19-30
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• 2020

The organic carbon in the ambient particulate matter (PM) is divided into primary organic carbon (POC) and secondary organic carbon (SOC) by their formation way. To regulate PM effectively, the estimation of the amount of POC and SOC separately is one of important consideration. Since SOC cannot be measured directly, previous studies have evaluated determination of SOC by the EC tracer method. The EC tracer method is a method of estimating the SOC value from calculating the POC by determining (OC/EC)pri which is the ratio of the measured values of OC and EC from the primary combustion source. In this study, three different ways were applied to OC and EC concentrations in PM_2.5 measured at Seoul for determining (OC/EC)pri: 1) the minimum value of OC/EC ratio during the measurement period; 2) regression analysis of OC vs. EC to select the lower 5-20% OC/EC ratio; 3) determining the OC/EC ratio which has lowest correlation coefficient value (R²) between EC and SOC which is reported as minimum R squared method (MRS). Each (OC/EC)pri ratio of three ways are 0.35, 1.22, and 1.77, respectively from the 1 hourly data. We compared the (OC/EC)pri ratio from 1hourly data with 24 hourly data and revealed that (OC/EC)pri estimated from 24 hourly data had twice larger than 1hourly data due to the low time resolution of sampling. We finally confirmed that the most appropriate value of (OC/EC)pri is that calculated by a regression analysis of 1 hourly data and estimated SOC amounts at PM_2.5 of the Seoul atmosphere.

• Journal of Preventive Medicine and Public Health
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• v.30 no.2 s.57
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• pp.428-436
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• 1997

Objectives : The purpose of this paper is to estimate the completeness of the Korean Medical Insurance Data in childhood asthma. Methods : Capture-recapture method was used to estimate the prevalence of childhood asthma and case ascertainment rate(completeness) of Korean Medical Insurance Data using two source model, 'Korean Medical Insurance Committee Data (KMICD)' and 'Nationwide Study of Asthma and Allergies in Korean Children'. The asthma cases were restricted to those who were born from 1981 to 1989 and were identified by their Resident Register Number. Asthma cases in Korean Medical Insurance Data were defined as cases coded by ICD-9 493 and ICD-10 J45. In 'Nationwide Study of Asthma and Allergies in Korean Children', asthma cases were defined as the children who had been diagnosed asthma and had experienced symptoms of asthma during the past 12 months. The defined cases in two data sources were matched by 13 digits Resident Register Number. The numbers of matched patients in two data sources were 245 of 32,825 eligible total subjects. Chapman and Wittes' nearly unbiased estimation was used for capture-recapture analysis of two data sources. Results : Observed prevalence rate of childhood asthma was 5.3% and estimated prevalence rate by capture-recapture analysis was 11.6%. The highest prevalence rate was observed in 6-7 age group and the older the rate decreased. The completeness (the proportion of cases ascertained by KMICD to the total observed cases by two data sources) was 20.6%, and ranged form 10.8% to 28.8% by area. Conclusions : Invalid diagnosis of cases might overestimate the prevalence of child-hood asthma and might underestimate the completeness of Korean Medical Insurance Committee Data in this study.