• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.2
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• pp.83-95
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• 2014

In this paper, we develop a portfolio selection model that can be used to invest in markets with margin requirements such as the foreign exchange market. An investment algorithm to implement the proposed portfolio selection model based on objective historical data is also presented. We further conduct empirical analysis on the performance of a hypothetical investment in the foreign exchange market, using the proposed portfolio selection model and investment algorithm. Using 7 currency pairs that recorded the highest trading volume in the foreign exchange market during the most recent 10 years, we compare the performance of 1) the Dollar Index, 2) a 1/N Portfolio which equally allocates capital to all N assets considered for investment, and 3) a hypothetical investment portfolio selected and managed according to the portfolio selection model and investment algorithm proposed in this paper. Performance is compared in terms of accumulated returns and Sharpe ratios for the 10-year period from January 2003 to December 2012. The results show that the hypothetical investment portfolio outperforms both benchmarks, with superior performance especially during the period following financial crisis. Overall, this paper suggests that a mathematical approach for selecting and managing an optimal investment portfolio based on objective data can achieve outstanding performance in the foreign exchange market.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.13-25
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• 2016

This paper analyses the impacts of the characteristics of policyholder and contract on the lapse of Voluntarily Insured Person in National Pension, using the recent lapse data from National Pension Service. The logistic regression model is used in examining lapse odds with several independent variables. The result demonstrates several hypotheses of the lapse behaviors. First, the lapse odds of men is lower than that of women. Second, the effect of age on lapse odds shows concave shave with the peak at 37. Third, insured period has a negative effect on lapse odds in entrants sample. Fourth, standard monthly income has little effect on lapse in either sample. Fifth, the lapse odds decreases as the expected benefit ratio increases. Sixth, 2013 pension bill resulted in the sharp increase of lapse odds and the effect was greater for entrants. Last but not least, spatial environment such as residence also affects the lapse behavior.

• Journal of Digital Convergence
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• v.16 no.10
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• pp.437-444
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• 2018

The purpose of this study is to comprehend the trend of digital experience centers' development direction and to find out the types of experiences, the characteristics of interaction and the attribute of contents by selecting 4 digital experience centers opened from 2008 to 2018. The types of digital experiences are operation, sensibility, reaction and induction based on precedent studies. The types of interaction are operation, touch and sensor. The attributes of contents are game, play and education. The result shows that the ratio of operation experiences is gradually higher. In the types of interaction, the trend is switching to operation and touch. The offer of experience activities by play type is getting higher. This study is intended to help create an empirical interaction of the content of the children's digital experience centers that will be deployed in the future.

• International Commerce and Information Review
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• v.13 no.1
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• pp.3-28
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• 2011

Recently marketing methods of small and medium exporting firms have changed from internet marketing using homepage, or e-catalogs, to search engine marketing. However, there is no specific proof of search engine marketing effectiveness. Therefore the purpose of this research is to explore marketing performance of search engine marketing(SEM) based on search engine optimization. In order to build an optimal SEM strategy, quantitative data are collected from the Google-analytics such as homepage visits, page views, and traffic source for three years. At the same time, this study has carried out a survey to measure the qualitative effectiveness. The result of this quantitative study suggests that the existing carryover effects and lag effects would be maintained through search engine optimization. Meanwhile, the qualitative survey shows that satisfaction and awareness of homepage have been improved after search engine optimization. This can support logically increase of homepage visiting ratio of quantitative analysis. Also exporting companies know very well, that traffic and page views have increased after search engine optimization.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.530-539
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• 2002

In designing the boundary confinement of shear walls, the current design provisions and recommendations are empirical and prescriptive; they specify a certain confinement length and details, regardless of the actual requirement of ductility Therefore, they are inappropriate to the performance based-design. The purpose of the present study is to develop a ductility design method that Is applicable to the performance based-design of shear wall. For the purpose, experimental studies were performed to investigate variations in the ductility of shear walls with the length of the boundary confinement. Five specimens modeling the compressive zone of cross sections with different confinement area were tested against eccentric vertical load. Through the experimental studies, strength, ductility, and failure mode of the compression zone were investigated. In addition, nonlinear numerical analyses for the overall cross-sections of shear wall were performed to investigate variations of the stress and strain profiles with the length of compression zone. On the basis of the experimental and numerical studies, a ductility design method for shear wall was developed. By using the proposed design method, for a given ductility demand, the area of lateral confinement and corresponding reinforcement ratio can be precisely determined so that the ductile behavior and economical design are assured.

• Journal of Environmental Policy
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• v.8 no.3
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• pp.81-113
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• 2009

This study conducted a regulatory impact analysis regarding the introduction of the Korean version of REACH(Registration, Evaluation and Authorization of Chemicals). The direct cost of the Korean REACH is estimated at a total of 101 billion Korean won over the 11 year period. The cost includes pre-registration, testing, registration, Chemical Safety Assessment(CSA) and Chemical Safety Report(CSR), evaluation, and the authorization costs of 15,223 chemical substances produced and imported more than 1 ton per year in Korea in 2006. With regard to the benefit, the only public health benefit is included in the estimation. Based on the available foreign and domestic data, this study estimated that the economic values of public health benefits are in the range of 33.2~138.6 billion Korean won if only the savings of the National Health Expenditures are considered and it reaches 203.9~1,640.3 billion Korean won if the willingness to pay(WTP) for disease prevention is included. This study proved that the Korean REACH passed the cost/benefit criteria. The benefit-cost ratio of the Korean REACH, however, is estimated to be lower than its EU counterpart. Thus it is suggested that a rigorous study to reduce the costs to industry be required before the Korean government introduces the Korean REACH.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.19-19
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• 1991

Fracture of Al2O3 tubes for different loading path under combined tension/torsion was investigated. Macroscopic directions of crack propagation agreed well with the maximum principal stress criterion, independent of the loading path. However, fracture strength from the proportional loading test(τ/σ= constant) showed either strengthening or weakening compared to that from uniaxial tension, depending on the ratio τ/σ. The Weibull theory was capable to predict the strengthening of fracture strength in pure torsion, but not the weakening in the proportional loading condition. The strengthening or weakening of fracture strength in the proportional loading condition was explained by the effect of shear stresses in the plane of randomly oriented microdefects. Finally, a new empirical fracture criterion was proposed. This criterion is based on a mixed mode fracture criterion and experimental data for fracture of Al2O3 tubes under combined tension/torsion. The proposed fracture criterion agreed well with experimental data for both macroscopic directions of crack propagation and fracture strengths.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.41.1-41.1
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• 2016

We present the physical properties of KIC 6220497 exhibiting multiperiodic pulsations from the Kepler photometry. The light curve synthesis represents that the eclipsing system is a semi-detached Algol with a mass ratio of q=0.243, an orbital inclination of i=77.3 deg, and a temperature difference of ${\Delta}T=3,372K$, in which the detached primary component fills its Roche lobe by ~87% and is about 1.6 times larger than the lobe-filling secondary. To detect reliable pulsation frequencies, we analyzed separately the Kepler light curve at the interval of an orbital period. Multiple frequency analyses of the eclipse-subtracted light residuals reveal 32 frequencies in the range of $0.75-20.22d^{-1}$ with semi-amplitudes between 0.27 and 4.55 mmag. Among these, four frequencies ($f_1$, $f_2$, $f_5$, $f_7$) may be attributed to pulsation modes, while the other frequencies can be harmonic and combination terms. The pulsation constants of 0.16-0.33 d and the period ratios of $P_{pul}/P_{orb}=0.042-0.089$ indicate that the primary component is a ${\delta}$ Sct pulsating star in p modes and, thus, KIC 6220497 is an oscillating eclipsing Algol (oEA) star. The dominant pulsation period of about 0.1174 d is considerably longer than the values given by the empirical relations between the pulsational and orbital periods. The surface gravity of log $g_1=3.78$ is significantly smaller than those of the other oEA stars with similar orbital periods. The pulsation period and the surface gravity of the pulsating primary demonstrate that KIC 6220497 would be the more evolved EB, compared with normal oEA stars.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.41.2-41.2
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• 2016

The follow-up BVRI photometric observations of NSVS 1461538, which was discovered as an $Algol/{\beta}$ Lyr eclipsing variable by Hoffman, Harrison & McNamara (2009), were performed for three years from 2011 to 2013 by using the 61-cm telescope and CCD cameras of Sobaeksan Optical Astronomy Observatory (SOAO). New light curves have deep depths both of the primary and secondary eclipses, rounded shapes outside eclipses and a strong O'Connell effect, indicating that NSVS 1461538 is a typical W UMa close binary system rather than an $Algol/{\beta}$ Lyr type binary star. A period study with all the timings shows that the orbital period may vary in a sinusoidal way with a period of about 5.6 yr and a small semi-amplitude of about 0.008 d. The cyclical period variation was interpreted as a light-time effect due to a tertiary body with a minimum mass of $0.66M{\odot}$. The first photometric solution with the Wilson-Devinney binary model shows that the system is a W-subtype contact binary with the mass ratio ($q=m_c/m_h$) of 3.46, orbit inclination of 85.6 deg and fill-out factor of 30%. From the existing empirical relationship between parameters, the absolute dimension was estimated. The masses and radii of the component stars are $0.28M{\odot}$ and $0.71R{\odot}$ for the less massive but hotter primary star, respectively, and $0.96M{\odot}$ and $1.21R{\odot}$ for the more massive secondary, respectively. Possible evolution of the system is discussed in the mass-radius and the mass-luminosity planes.

• Journal of the Korean Geographical Society
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• v.51 no.3
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• pp.367-380
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• 2016

This study reviewed and compared methods for mapping aggregated low birth weight (LBW) and geographic variations in LBW in South Korea. Based on this review, we produced LBW maps in South Korea. Standardized mortality/morbidity ratios (SMRs) and crude mortality rates have been widely used for many years in epidemiological research. However, SMR-based maps are likely to be affected by sample size of unit area. Therefore, this study adopted a model-based approach using Bayesian estimates to reduce noisy variability in the SMR. By using a Bayesian model, we can calculate a statistically reliable RR values. We used the full Bayes estimator, as well as empirical Bayes estimators. As a result, variations in the two Bayes models were similar. The SMR-based statistics had the largest variation. The result maps can be used to identify regions with a high risk of LBW in South Korea.