• Environmental and Resource Economics Review
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• v.21 no.1
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• pp.93-127
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• 2012

We estimate how much KEPCO can save their loss and how much social welfare can be increased by applying the real-time pricing instead of current regulated retail price in the electricity market in order to analyze the problem of the regulated retail price which is fixed below the marginal cost. We estimate the demand functions of peak time and off-peak time in summer (June to August) and winter (December to February). We construct the supply function based on hourly step-wise linear marginal cost functions, too. We find that the increase of social welfare will be 67 billion won in summer if the fixed retail price is changed into the real-time pricing scheme. The total 705 billion won will be transferred from consumer surplus to producer surplus and the rest (67 billion won) will be saved from the reduction of deadweight loss among KEPCO's loss. In winter, the increase of social surplus will be 225 billion won and 1,174 billion won of KEPCO's loss will be transferred from consumer surplus. As a result, we conclude that the regulation of the retail price in the electricity market induces the social welfare loss and KEPCO suffers a huge loss.

• Korean Security Journal
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• no.39
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• pp.131-160
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• 2014

The radicalization of diaspora is a new phenomena that have been begun to emerge in the complex picture of terrorism. The existence of diaspora and its supports for violent terrorist activities have made the whole dynamic of terrorism more complicated and unpredictable. Therefore, this study attempts to understand the relationship between diaspora support and violent terrorist activities in the constellation of other significant correlates of violent terrorist activities discussed in the prior studies. In analyses, the author utilized a step wise regrssion analyses with a set of variable drawn from an emphatical data collected in Arab and Africa region. The data used in this study is called as "MAROB"(the Minorities at Risk Organizational Behavior), which is developed by START and Minority at Risk project and contains information terrorist groups in Middle-East and Africa region. Considering the significance of this new emergence of the link between diaspora and violent terrorist activities, and the challenging nature of conducting empirical studies on this topic, this study have great contributions on the development in the field of criminal justice as well as terrorism. Other contributions of this study, policy implications, and suggestions for future studies are further discussed in the discussion.

• Journal of Food Hygiene and Safety
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• v.24 no.1
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• pp.46-49
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• 2009

The desmutagenic activity of the water extract of Cassia tara L on the mutagenicity induced by 4-nitroquinoline 1-oxide (4-NQO) and N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG) was studied using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Cassia tara L. at concentration of $100{\mu}g$/assay were 27.5% and 40% against 4-NQO and MNNG. The water extract of Cassia tara L. was separated into methanol soluble and methanol insoluble parts. The methanol soluble part exhibited higher inhibition effects than the methanol insoluble part against the mutagenic activities of 4-NQO and MNNG. Step-wise fractionation of methanol soluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effects of 23.0 and 19.0% against mutagenicities of MNNG and 4NQO, respectively. The results clearly indicated that the water fraction showed much stronger antimutagenicity against MNNG than 4NQO. The inhibition rates of aqueous fraction of methanol-soluble from water extracted Cassia tara L. at concentrations of 1.0, 10, 100 and $250{\mu}g$/assay were 8.0%, 12.0%, 25.5% and 43.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activities induced by MNNG.

• Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.160-166
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• 2006

We explored the possibilities of using the freshwater rotifer Brachionus angularis as a live food for small fishes cultured in fresh- or brackish waters. Brachionus angularis were collected from a reservoir for isolation and laboratory culture. Length and width of the lorica were $102.3{\mu}m$ and $76.6{\mu}m$, respectively, and those of amictic eggs were $64.4{\mu}m\;and\;47.9{\mu}m$, respectively. When their growth rates were examined at six different temperatures, i.e., 15, 20, 25, 30, 35, and $40^{\circ}C$, the highest daily growth rate of 0.801 was observed at $35^{\circ}C$, and growth was lower with decreasing temperature. Adaptation to salinity change was evaluated with two different modes of salinity increase: step-wise elevation lasting for short durations of 5 to 30 min or a long duration of 24 h. With the short duration modes, no individuals survived salinity higher than 10 psu, and the number of live individuals did not increase throughout the experiment. However, in the 24-h elevation, the number of individuals increased when salinity was elevated by 1 to 2 psu per day for the first 2 or 3 days, while no increase in number occurred at salinity increments higher than 3 psu per day. In addition, to assess the effect of different diets, four single-component diets (Chlorella vulgaris, Nannochloris sp., baker's yeast, or dry yeast) and three combination diets (C. vulgaris + Nannochloris sp. + baker's yeast + dry yeast; C. vulgaris 70% + baker's yeast 30%; C. vulgaris 30% + baker's yeast 70%) were used. The specific growth rates of B. angularis fed combination diets were higher than those of rotifers fed any single-component diet, with the highest rate of 0.648 in B. angularis fed a mixture of C. vulgaris, Nannochloris sp., baker's yeast, and dry yeast, and the lowest rate of 0.200 in those fed dry yeast only. Our results indicate that the freshwater rotifer B. angularis can be used for seedling production of both freshwater and brackish-water fishes that require small (less than about $120{\mu}m$) live food during their early stages.

• Clean Technology
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• v.5 no.1
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• pp.78-85
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• 1999

In the Kimchi manufacturing industry that has recently been on its greatest growth, the rinsing process for salt-pickled Chinese cabbage in a brining step generates a vast amount of rinsing wastewater containing salts, colloids, and organics released from the raw material. In this study, the experimental method was developed to optimize the rinsing water consumption and thus to minimize the rinsing wastewater generation. The continuous counter-current rinsing basin in the actual plant was simulated through the lab-scale three batch-wise rinsing tanks. Rinsing efficiencies for the brined cabbage from the same brining tank were almost in the same level, whereas those varied substantially from source to source in the raw Chinese cabbage provided. When rinsing water used were decreased from 3.3 L/head to 2.7 L/head, no significant change was observed with respect to COD, turbidity, conductivity, $Na^+$, and $Cl^-$ concentrations in the extracted solution of the rinsed cabbage. However, the quality of the extracted solution was badly deteriorated as the amount of rinsing water used dropped down to below 2.7 L/head. The reduction of rinsing water up to 18% was proved to be possible without any negative effect on the quality of the product, Kimchi.

• Korean Journal of Child Education & Care
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• v.17 no.2
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• pp.99-114
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• 2017

This study investigated the affects of Parent-child interaction, peer interaction and teacher-child interaction on kindergartners' social competence, language and literacy Ability. Participants were 1203 children attending panel study on Korean children. It used the 'Social Competence Inventory', 'SECCYD', 'HEQ', 'PIPPS' and the 'Teacher-Child Relation Scale' in collection of data. Collected data were analyzed through the SPSS 18.0 program and pearson's correlation and step-wise multi regression analysis. Findings are as follows. First, there were positive correlations between children's social competence and parent-child interaction, peer interaction and teacher-child interaction. Second, there were positive correlations between children's language and literacy ability and peer interaction and teacher-child interaction. Third, Parent-child interaction, peer interaction were predictable variable affecting the young children's social competence. Fourth, peer interaction and teacher-child interaction were found to be predictable variables affecting the young children's language and literacy ability.

• Journal of Intelligence and Information Systems
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• v.18 no.1
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• pp.91-107
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• 2012

As the Internet becomes more popular, many people use it to communicate. With the increasing number of personal homepages, blogs, and social network services, people often expose their personal information online. Although the necessity of those services cannot be denied, we should be concerned about the negative aspects such as personal information leakage. Because it is impossible to review all of the past records posted by all of the people, an automatic personal information detection method is strongly required. This study proposes a method to detect or classify online documents that contain personal information by analyzing features that are common to personal information related documents and learning that information based on the Na$\ddot{i}$ve Bayes algorithm. To select the document classification algorithm, the Na$\ddot{i}$ve Bayes classification algorithm was compared with the Vector Space classification algorithm. The result showed that Na$\ddot{i}$ve Bayes reveals more excellent precision, recall, F-measure, and accuracy than Vector Space does. However, the measurement level of the Na$\ddot{i}$ve Bayes classification algorithm is still insufficient to apply to the real world. Lewis, a learning algorithm researcher, states that it is important to improve the quality of category features while applying learning algorithms to some specific domain. He proposes a way to incrementally add features that are dependent on related documents and in a step-wise manner. In another experiment, the algorithm learns the additional dependent features thereby reducing the noise of the features. As a result, the latter experiment shows better performance in terms of measurement than the former experiment does.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.58-66
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• 2017

This study was a descriptive correlational study investigating the mediating effects of resilience in the relationship between depression and rehabilitation motivation in middle-aged stroke patients. There was a total of 185 middle-aged patients aged 40 to 64 years, who were diagnosed with stroke at a university hospital and rehabilitated at three local hospitals located in S city and four hospitals in U city. The data were collected using a self-reported questionnaire between the 1st and 31st of December in 2016. The data were analyzed using t-test, ANOVA, Pearson's correlation coefficient, and step-wise causal method using SPSS/WIN 22.0 statistical program. To test the statistical significance of the mediation effect, PROCESS and bootstrapping were used. The mean age of the subjects were $56.26{\pm}6.37$ years. There were 70.3% male subjects, an average depression level was $21.21{\pm}7.09$, an average resilience was $25.52{\pm}9.63$, and rehabilitation motivation was $47.44{\pm}5.87$. Depression was negatively related to resilience and rehabilitation motivation. However, resilience and rehabilitation motivation have a static correlation. These results confirmed that resilience appears to be a complete mediating effect in the relationship between depression and rehabilitation motivation. Therefore, it is important to develop a resilience enhancement program to improve the motivation of rehabilitation for stroke patients.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.416-416
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• 2019

육상 담수는 대기중 이산화탄소($CO_2$) 배출의 중요한 발생원으로 주목되고 있다. 하천 및 강에서 대기중으로 배출되는 $CO_2$는 전 세계 탄소순환의 핵심요소이며, 대부분의 하천과 강은 $CO_2$로 과포화 되어있다. 세계적으로 하천 및 강의 $CO_2$ 배출량은 호수 및 저수지의 배출량보다 약 5배 많은 것으로 보고되고 있으나, 국내연구에서는 연구사례가 드물다. 따라서 본 연구의 목적은 낙동강 중하류에 위치해있는 강정고령보(GGW), 달성보(DSW), 합천창녕보(HCW), 창녕함안보(CHW)에서 발생되는 순 대기 배출 플럭스(Net Atmospheric Flux, NAF)의 동적 변동 특성을 분석하고, 데이터마이닝 기법을 적용하여 쉽게 수집할 수 있는 물리적 및 수질 변수로 $CO_2$ NAF를 추정하는데 사용할 수 있는 간략한 예측 모델을 개발하는데 있다. $CO_2$ NAF는 대기-수면 경계면에서의 $CO_2$ 부분압($pCO_2$)의 차에 기체전달속도를 곱하여 산정하였으며, 기체전달속도는 Cole and Caraco(1998)가 제안한 식을 사용하였다. 담수와 해수의 탄산염 시스템에서 열역학적 화학평형을 모두 고려한 $CO_2$SYS 프로그램을 사용하여 수중의 $pCO_2$를 산정하였고, $CO_2$ NAF는 Henry의 법칙과 Fick의 1차 확산법칙을 사용하여 계산하였다. $CO_2$ NAF의 시간적 변동성에 영향을 미치는 환경요인을 평가하기 위해서 상관분석, 주성분분석(Principal Component Analysis; PCA), 단계적다중회귀모델(Step-wise Multiple Linear Regression; SMLR), 랜덤포레스트(Random Forest; RF)방법을 사용하였다. SMLR 모델은 R package인 olsrr, RF 모델은 R package인 caret, randomForest를 이용하여 분석하였다. 연구 결과, 4개 보 상류 하천구간은 조류의 성장이 활발한 일부 기간을 제외한 대부분의 기간에서 $CO_2$를 대기로 배출하는 종속영양시스템(Heterotrophic system)을 보였다. $CO_2$ NAF의 중위값은 HCW에서 최소 $391.5mg-CO_2/m^2day$, DSW에서 최대 $1472.7mg-CO_2/m^2day$였다. 모든 보에서 NAF는 pH와 강한 음의 상관관계를 보였으며, $pCO_2$와 Chl-a도 음의 상관관계를 보였다. 이는 조류가 수중에서 $CO_2$를 소비하고 pH를 증가시키기 때문이다. PCA 분석 결과, NAF와 $pCO_2$가 높은 공분산을 보였으며, pH와 Chl-a는 반대 방향으로 군집되어 상관분석과 동일한 결과를 보였다. 이 연구를 통해 개발된 SMLR 모델과 RF 모델의 Adj. $R^2$ 값은 모든 보에서 0.77 이상으로 나왔으며, $pCO_2$ 측정 데이터가 없더라도 하천의 $CO_2$ NAF를 추정하는 방법으로 사용될 수 있을 것으로 평가된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.413-413
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• 2019

하천과 호수에서 남조류의 이상 과잉증식 문제(이하 녹조문제)는 담수생태계의 생물다양성을 감소시키며, 음용수의 이취미 원인물질을 발생시켜 물 이용에 장해가 된다. 또한 독소를 생산하는 유해남조류가 대량 증식할 경우에는 가축이나 인간의 건강에 치명적 해를 끼치기도 한다. 그 동안 국내에서 녹조문제는 댐 저수지와 하구호와 같은 정체수역에서 간헐적으로 문제를 일으켰으나, 4대강사업(2010-2011)으로 16개의 보가 설치된 이후 낙동강, 금강, 영산강 등 대하천에서도 광범위하게 발생되고 있어 중요한 사회적 환경적 이슈로 대두되었다. 한편, 대하천에 설치된 보 구간에서 빈번히 발생하는 녹조현상의 원인에 대해서는 전 지구적 기온상승에 따른 기후변화의 영향이라는 주장과 유역으로부터 영양염류의 과도한 유입, 가뭄에 따른 유량감소, 보 설치에 따른 체류시간 증가 등 다양한 의견이 제시되고 있으나, 대상 유역과 수체의 특성에 따라 녹조 발생의 원인이 상이하거나 또는 다양한 요인이 복합적으로 작용하기 때문에 보편적 해석(universal interpretation)이 어려운 것이 현실이다. 따라서 각 수계별, 보별 녹조현상에 대한 정확한 원인분석과 효과적인 대책 마련을 위해서는 집중된 실험자료와 데이터마이닝 기법에 근거로 한 보다 과학적이고 객관적인 접근이 이루어져야 한다. 본 연구에서는 2012년 보 설치 이후 남조류에 의한 녹조현상이 빈번히 발생하고 있는 낙동강 4개보(강정고령보, 달성보, 합천창녕보, 창녕함안보)를 대상으로 집중적인 현장조사와 실험분석을 수행하고, 수집된 기상, 수문, 수질, 조류 자료에 대해 통계분석과 다양한 데이터모델링 기법을 적용하여 보별 남조류 우점 환경조건과 이를 제어하기 위한 주요 조절변수를 규명하는데 있다. 연구대상 보 별 수질과 식물플랑크톤의 정성 및 정량 실험은 2017년 5월부터 2018년 11월까지 2년에 걸쳐 실시하였으며, 남조류 세포수 밀도와 환경요인과의 상관성 분석을 실시하고, 단계적 다중회귀모델(Step-wise Multiple Linear Regressions, SMLR), 랜덤포레스트(Random Forests, RF) 모델과 재귀적 변수 제거 기법(Recursive Feature Elimination using Random Forest, RFE-RF)을 이용한 변수중요도 평가, 의사결정나무(Decision Tree, DT), 주성분분석(Principal Component Analysis, PCA) 기법 등 다양한 모수적 및 비모수적 데이터마이닝 결과를 바탕으로 각 보별 남 조류 우점 환경요인을 종합적으로 해석하였다.