• Journal of Korea Water Resources Association
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• v.49 no.10
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• pp.823-833
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• 2016

This study developed a trivariate Copula function based drought frequency analysis model to better evaluate the recent 2014~2015 drought event. The bivariate frequency analysis has been routinely used for the drought variables of interest (e.g. drought duration and severity). However, the recent drought patterns showed that the intensity can be regarded as an important factor which is being characterized by short duration and severe intensity. Thus, we used the trivariate Copula function approach to incorporate the trivariate drought characteristics into the drought frequency analysis. It was found that the return periods based on the trivariate frequency analysis are, in general, higher than the existing bivariate frequency analysis. In addition, this study concludes that the increase in drought frequency claimed by the Gumbel copula function has been overestimated compared to the Student t Copula function. In other words, the selection of copula functions is rather sensitive to the estimation of trivariate drought return periods at a given duration, magnitude and intensity.

• Journal of Korea Water Resources Association
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• v.48 no.12
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• pp.969-979
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• 2015

This study applied a probabilistic-based hidden Markov model (HMM) to better characterize drought patterns. In addition, a copula-based bivariate drought frequency analysis was employed to further investigate return periods of the current drought condition in year 2015. The obtained results revealed that western Kangwon area was generally more vulnerable to drought risk than eastern Kangwon area using the 40-year data. Imjin-river watershed including Cheorwon area was the most vulnerable area in terms of severe drought events. Four stations in Han-river watershed showed a joint return period exceeding 1,000 years associated with the drought duration and severity in 2014-2015. Especially, current drought status in Northern Han-river and Imjin-river watershed is most severe drought exceeding 100-year return period.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.9
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• pp.19-27
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• 2002

Characteristics of interconnect lines considering underlayer geometries of a silicon substrate and crossing metal lines are experimentally analyzed through elaborately devised patterns. In this work, test patterns for transmission lines having several kinds of underlayer geometries were devised, and the signal characteristics and responses are measured by S-parameter and time domain reflection meter (TDR). The patterns were designed and fabricated with a deep-submicron CMOS DRAM technology having 1 Tungsten and 2 Aluminum metals. From the analysis of measured results on the patterns, it is founded that the effects of underlayter line structures on line parameters (especially line capacitance and resistance) and signal distortions occurred from them cannot be negligible. The results provide useful and insightful understanding in the skew balance of package leads and global signal lines such as high-speed clock and data lines.

• Journal of Korea Trade
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• v.27 no.1
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• pp.139-158
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• 2023

Purpose - The study of co-movements between stock markets is a crucial area of finance and has recently received much interest in a variety of studies, especially in international finance. Stock market co-movements are a major phenomenon in financial markets, but they are not necessarily independent of the real market. Several studies support the idea that bilateral trade linkages significantly impact stock market correlations. Motivated by this perspective, this study investigates whether real market integration due to trade agreements brings about financial market integration in terms of stock market co-movement. Design/methodology - Over the 10 free trade agreements (FTAs) signed by the United States, using a dynamic conditional correlations (DCC) multivariate GARCH (MGRACH) model, we empirically measure the degree of integration by finding DCCs between the US market and the partner country's market. We then track how these correlations evolve over time and compare the results before and after trade agreements. Findings - According to the empirical results, there are positive return spillover effects from the US market to eight counterpart equity markets, except Jordan, Morocco, and Singapore. Especially Mexico, Canada, and Chile have large return spillover effects at the 1% significance level. All partner countries of FTAs generally have positive correlations with the US over the entire period, but the size and variance are somewhat different by country. Meanwhile, not all countries that signed trade agreements with the United States showed the same pattern of stock market co-movement after the agreement. Korea, Mexico, Chile, Colombia, Peru, and Singapore show increasing DCC patterns after trade agreements with the US. However, Canada, Australia, Bahrain, Jordan, and Morocco do not show different patterns before and after trade agreements in DCCs. These countries generally have the characteristic of relatively lower or higher co-movements in stock markets with the US before the signing of the FTAs. Originality/value - To our knowledge, few studies have directly examined the linkages between trade agreements and stock markets. Our approach is novel as it considers the problem of conditional heteroscedasticity and visualizes the change of correlations with time variations. Moreover, analyzing several trade agreements based on the United States enables the results of cross-country pairs to be compared. Hence, this study provides information on the degree of stock market integration with countries with which the United States has trade agreements, while simultaneously allowing us to track whether there have been changes in stock market integration patterns before and after trade agreements.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.2
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• pp.85-105
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• 1994

As an exploratory attempt, this study examined the correlates of different strategic groups in the Korean health food industry. Many prior studies believe that different entry mode such as entry timing and patterns, and different cognitive structure of top managers lead to the formation of different strategic groups in the same industry. Different strategic groups with different sources or mobility barriers are also expected to produce different level of economic performance. Multivariate statistical analyses of data from 32 firms in the Korean health food industry revealed the following results. i) There are four different strategic groups with different levels of mobility barriers in terms of firm size, scope of product/market domain, degree of forward and backward integration. ii) Differences in both entry timing and environmental perception of top managers are associated with different stratetic groups. However, the patterns of entry are not significantly different among four strategic groups. iii) Four strategic groups exhibit different level of economic performance in terms of sales growth rate and return on investment. Finally, this study tried to identify commonalities and differences among various strategic groups found in several industries in Korea. The results offered some implications to search for developing a useful theory of strategic groups in Korea.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.27-34
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• 2014

The paper proposed a sizing method of an energy storage system(ESS) for peak shaving of high-speed railway substations based on load profile patterns of substations. A lithium based battery ESS was selected since it can produce high-power at high speed that peak shaving requires, and also takes up a relatively smaller space for installation. Adequate size of the ESS, minimum capacity which can technically meet a peak shaving target, was determined by collectively considering load patterns of a target substation, characteristics of the ESS to be installed, and optimal scheduling of the ESS. In case study, a local substation was considered to demonstrate the proposed sizing method. Also economic analysis with the determined size of ESS was performed to calculate electricity cost savings of the peak shaving ESS, and to offer pay-back period and return on investment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.1-8
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• 2011

In this paper, data transmission corrugated horn antenna for RF sensor satellite system and its radiation characteristic are presented. The proposed antenna is designed, fabricated and measured to obtain the maximum gain at ${\pm}60^{\circ}$ of its radiation patterns. The result of the proposed antenna is that the return loss is less than -15 dB and the gain is over 5 dBi at ${\pm}60^{\circ}$ of its radiation patterns. From these results, it is confirmed that the proposed can be used as data transmission corrugated horn antenna for RF sensor satellite system.

• Journal of the Korean Data and Information Science Society
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• v.27 no.3
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• pp.791-801
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• 2016

The purpose of this study is to examine factors affecting the intent of re-employment of inactive registered nurses. This study presents a secondary analysis of data collected in 'Nurse Turnover On-line Survey' by Korean Nurses Association and Korea Institute for Health and Social Affairs in 2014. The analysis shows that 70.9% of inactive RNs has an intent to return to practice, and most of them preferred 'flexible working options' (47.8%) or 'fixed day shifts' (43.3%) as a work pattern. Main reasons for resigning from their last job have been found to be 'high work intensity' (18.8%) and 'difficulties of night shifts' (16.7%). Inactive married RNs who have working histories in a general hospital or a long-term care hospital or have preferences for traditional shift works showed a stronger intent to return to practice than their reference group. Our study shows that, for inactive RNs to return to practice, it is recommendable to adopt various non-traditional working patterns, to make a staffing distribution considering the labor intensity and to develop education programs designed to increase RNs' professional satisfaction.

• Journal of Labour Economics
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• v.30 no.1
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• pp.1-30
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• 2007

Using the Korean Labor and Income Panel Study 2001 (KLIPS 2001), this paper examines gender differences in the return to education in Korea. On average, there is little difference in return to education between male and female workers. However, this paper provides evidence that the impact of education on wages is greater for female workers compared to that for male workers using three different estimation strategies. First, a simple cohort analysis shows that the estimated returns to education for male and female workers have different patterns by age cohort and this is the main reason we observe little gap in average returns to education between men and women. Second, we find that college degree has a significant impact on women's labor market outcomes, while there is little gain for men in terms of wage levels by having college degree. Finally, when controlling unobservable individual ability level with test scores, education has no significant impact on male workers' wage levels, while the impact of education on wages is considerably large for female workers. All three findings support that the impact of education on labor market outcomes is greater for female workers compared to that for male workers as many researchers have found in other OECD countries.

• The Korean Journal of Emergency Medical Services
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• v.11 no.2
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• pp.67-86
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• 2007

This study is about the drunken drivers' accident patterns and behavior and aims at providing basic data for developing measures to secure safety against accidents by drunken drivers and programs to cultivate good drinking habits. For this purpose, this study conducted a questionnaire of 800 persons over 20 years of age in the selected 20 companies with more than 30 employees in the 4 regions(Daegu, Masan, Changwon, and Jinhae) and analysed the 653 sheets except invalid ones among the returned 673 survey sheets in total(return rate 84.13%), and the researcher conducted a man-to-man interview with each subject from June 20th to July 31st 2006. The result are as the following. As the experience of causing an accident by drinking, the 79.1% of them had the experience, and in case of the subjects with excessive drinking over 4 times a year, the rate of the accident by drinking showed as high as 90.5%. As the patterns of accidents, in male subjects, violence(38.5%) and traffic accidents(37.1%) showed high, while in the female, hurts from falls and fall accidents(40.2%) were found be high. In case of the traffic accidents among the accidents by drinking, the rate of causing serious damage to the life was found to be 89.3%, so it showed that the traffic accidents caused by drinking were influencing on the life much. In conclusion, the drinking problem may be controlled by each individual's will, but without change of social environment and system around people, the problem can not be eradicated. Therefore there should be social infrastructure which can help people to actively live their life with exercises and hobbies, and in order to prevent the reoccurrence of a drink accident, and social structure in which there are education programs for drink accident causers and one can change the perception about drinking culture, should be formed.