• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.69
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• pp.133-143
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• 2001

가공조건은 가공비용과 시간을 줄이고 제품의 품질을 결정하는데 영향을 주는 주요 요인중의 하나이다. 본 논문에서는 밀링 공정을 위한 작업설계(Operation Planning) 시스템에서, 가공조건을 지속적으로 향상시키기 위한 새로운 방법론을 제안한다. 제안된 방법론은 밀링 작업에 대하여 (1) 퍼지 아트맵 신경회로망 모델에 의해 가공조건을 실시한 학습하고 (2) 교체 알고리즘이라 불리는 새로운 알고리즘을 포함한다. 제안된 교체 알고리즘은 기존의 학습 정보보다 효율적인 새로운 가공조건이 얻어졌을 때 이를 이용하여 기존의 학습 정보보다 효율적인 새로운 가공조건이 얻어졌을 때, 이를 이용하여 기존의 학습 정보를 대체하는 기능을 수행한다. 본 논문에서는 우선 작업설계 시스템의 전반적인 기능을 간략히 소개한 후 제안된 방법론에 의한 의사결정 과정을 자세히 기술한다. 또한, 다양한 시뮬레이션을 통하여 제안된 방법론의 의한 의사결정 과정을 자세히 기술한다. 또한, 다양한 시뮬레이션을 통하여 제안된 방법론의 성능을 예시하도록 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.39-48
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• 2020

Since the fire accident of ESS (energy storage system) occurred at Gochang KEPCO Power Testing Center in August 2017, 29 fire cases with significant property losses have occurred in Korea. Although the cause of fire accidents have not been identified precisely, it should be considered battery and PCS (power conditioning system) as well as unbalance issues in the distribution system. In particular, circulating currents in a neutral line of a grid-connected transformer, which can affect a magnetized current, may have a negative effect on the ESS with unintentional core saturation and surge voltages at the secondary side of the transformer. Therefore, this paper proposes the modeling of the distribution system, which was composed of a substation, grid-connected transformer, and customer loads using PSCAD/EMTDC S/W, to analyze the phenomena of circulating current and surge voltages of the transformer with unbalanced currents in the distribution system. This paper presents a countermeasure for a circulating current with the installation of NGR (neutral grounding resistor) in grid-connected transformer. From the simulation results, it is clear that exceeding the circulating current and surge voltage at the secondary side of the transformer can be one of the causes of fire accidents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5550-5558
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• 2015

Recently, fuel cell with high energy efficiency and low CO2 emission is energetically interconnected with power system. Especially, FCGS(Fuel Cell Generation System) which usually operates at high temperature, is being developed and installed in the form of large scale system. However, it is reported that power system disturbances related to surge, harmonic and EMI have caused several problems such as malfunction of protection device and damage of control device in the large scale FCGS. In order to solve these problems, this paper presents a modeling of operation characteristics of FCGS by PSCAD/EMTDC, ETAP, P-SIM software. And also, this paper proposes countermeasure algorithms to prevent power system disturbances. From the simulation results, it is confirmed that the proposed algorithm is useful method for the stable operation of large scale FCGS.

• The Journal of the Convergence on Culture Technology
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• v.7 no.2
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• pp.367-375
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• 2021

This study aimed to identify the knowledge structure of researches on 'untact' and derived implications for directions for the studies using text mining. The study included network analysis and topic modelling of keywords and abstracts from 171 thesis published until October 2020. Centrality analysis showed that 'untact' studies had been focused on service, usage, consumption, technology and online. From the topic modelling, 6 topics such as 'COVID-19 and socio-technological change', 'needs and utilization of education contents', 'technology and service for user convenience', 'product marketing and sales', 'service design of the company', 'influence factors of usage and consumption' were extracted. Keywords that connect each topic were technology, service, usage, consumption, needs and factor. Exploratory analysis of 'untact' researches using text mining provides useful results for development of 'untact' studies.

• Journal of Science Education
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• v.47 no.1
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• pp.37-51
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• 2023

This study explored the factors influencing major satisfaction and academic satisfaction of science education major students at the College of Education using machine learning models, random forest, gradient boosting model, and SHAP. Analysis results showed that the performance of the gradient boosting model was better than that of the random forest, but the difference was not large. Factors influencing major satisfaction include 'satisfaction with science teachers in high school corresponding to the subject of one's major', 'motivation for teaching job', and 'age'. Through the SHAP value, the influence of variables was identified, and the results were derived for the group as a whole and for individual analysis. The comprehensive and individual results could be complementary with each other. Based on the research results, implications for ways to support pre-service science teachers' major and academic satisfaction were proposed.

• Childhood Kidney Diseases
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• v.13 no.1
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• pp.49-55
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• 2009

Purpose : We aimed to compare the frequency of positive repeat urine cultures 48 hours after antimicrobial treatment between anatomically normal and abnormal urinary tract Infection (UTI) groups to determine the potential clinical usefulness of the tests. Methods : We reviewed medical records of 930 patients under age 14, who had been admitted for UTI at Gyeongsang National University Hospital from January 1, 1998 to August 1, 2008. The eligible patients were divided into two groups the anatomically normal UTI group and the anatomically abnormal UTI group. Statistical analyses were performed with variables consisting of the sex ratio, age distribution and the frequency of positive repeat urine cultures of each group. Results : The sex ratio of the anatomically normal UTI group was M:F=1.9:1, whereas that of the anatomically abnormal UTI group was M:F=3.5:1 (P=0.019). For age distribution, it was found that the mean age of the anatomically normal UTI group was $0.82{\pm}1.83$ years, whereas that of the anatomically abnormal UTI group was $1.18{\pm}2.57$ years (P=0.113). The frequency of positive repeat urine cultures in the anatomically normal UTI group was 3/279 (1.1%), whereas that of the anatomically abnormal UTI group was 1/90 (1.1%) (P=0.675). Conclusion : We conclude that performing a repeat urine culture is not justified in terms of clinical usefulness, and it is unreasonable to use the results as an index of therapeutic success. A follow-up urine culture is unnecessary in patients with both the anatomically normal and abnormal UTI group.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.12
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• pp.1732-1739
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• 2009

The purpose of this study was to analyze factors that influence consumption pattern of snacks of middle school students. The subjects of study were 607 middle school students (male: 316, female: 291) in Ilsan area. The subjects were surveyed by a self-administered questionnaire about anthropometrics, mother's employed status, parents' education level, and snack consumption pattern. Male students showed higher consumption in 'milk and milk products' (p<0.05), 'instant noodles' (p<0.01), and 'cereal' (p<0.05). In the other hand, female students showed higher consumption in 'biscuits, cookies' (p<0.01) and 'candy and chocolates' (p<0.01). Subjects in underweight group showed higher frequency in the consumption of 'biscuits, cookies' (p<0.05) and 'candy and chocolates' (p<0.001) compared with normal weight or overweight subjects. The subjects with mother not having a job showed higher consumption of snacks under controlling parents (p<0.001), and higher consumption in 'fruit and fruit juice' (p<0.05) and 'milk and milk products' (p<0.01) compared to the subjects with mother having a job. The subjects with parents having higher education level showed higher of consumption in 'fast food'. These results suggest that general characteristics of the subjects and characteristics of family environment may affect consumption pattern of snacks in middle school students.

• 재활복지
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• v.21 no.4
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• pp.33-57
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• 2017

The purpose of this study is to analyze factors that can affect the satisfaction with life of elderly with disabilities so as to provide measure for improving the quality of their lives. To that end, elderly with disabilities and 50 years or older were extracted from the raw data (2nd Wave, 1st Survey) of 2016 Panel Survey of Employment for the Disabled (or PSED), conducted by the Ministry of Employment and Labor and the Korea Employment Agency for the Disabled. And they were classified into those aging with disabilities (onset of a disability before 50 years) and those having disabilities with aging (onset of a disability after 50 years). The results of the analysis show factors affecting satisfaction with life were different in the two groups. Although awareness about employment, awareness about disability, levels of happiness, subjective socioeconomic standing, and financial problems were the common factors, health conditions and ability to function in daily life affected more those aging with disability, and employment status was more relevant to those having disability with aging. Based on these results, this study points out the need to take into account awareness about employment and disability when developing services for elderly with disabilities, to solve their financial problems, and to provide a collective approach to employment and health issues in order to improve the quality of their lives.

• The Korean Journal of Financial Management
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• v.24 no.4
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• pp.75-106
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• 2007

In this study, it is analyzed whether oil price plays a major role in the pricing return on Koran stock market and examined why the covariance risk between oil and return on stock is different in each industry. Firstly, this study explores whether the expected rate of return on stock is pricing due to global oil price factors as a function of risk premium by using a two-factor APT. Also, it is examined whether spill-over effects of oil price volatility affect the beta risk to oil price. Considering the asymmetry of oil price volatility, we use the GJR model. As a result, it shows that oil price is an independent pricing factor and oil price volatility transmits to stock return in only electricity and electrical equipment. Secondly, the two step-analyzing process is introduced to find why the covariance between oil price factor and stock return is different in each industry. The first step is to study whether beta risk exists in each industry by using two proxy variables like size and liquidity as control variables. The second step is to grasp the systematic relationship between the difference of liquidity and size and beta to oil price factor by using the panel-data model which can be analyzed efficiently using the cross-sectional data formed with time series. Through the analysis, we can argue that oil price factor is an independent pricing factor in only electricity and electrical equipment having the greatest market capitalization, and know that beta risk to oil price factor is a proxy of size in the other industries. According to the result of panel-data model, it is argued that the beta to oil price factor augments when market capitalization increases and this fact supports the first assertion. In conclusion, the expected rate of return of electricity and electrical equipment works as a function of risk premium to market portfolio and oil price, and the reason to make beta risk power differentiated in each industry attributes to the size.

• Journal of the Korean Society for Library and Information Science
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• v.42 no.2
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• pp.371-392
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• 2008

The books and circulation-related data in the Online Public Access Catalog System of the H-Public library were collected and analyzed in this paper. The methods which may be applied to the Customer Relationship Management in a public library based on the results were also suggested here. Collected data were 57,927 bibliographic data of books, 11,871 patron data and 27,145 circulation records. The type of collections. circulation frequencies, total number of circulated books, publication year, and use factor as relation factor from the analyzed data of circulation records were extracted. They were also analyzed, and verified by various statistical methods such as correlation coefficient, non-parametric method, etc.