• Journal of Power Electronics
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• 제16권1호
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• pp.259-267
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• 2016

This paper presents a stand-alone variable speed constant frequency (VSCF) ship shaft generator system based on a brushless doubly-fed machine (BDFM). In this system, the output voltage amplitude and frequency of the BDFM are kept constant under a variable rotor speed and load by utilizing a well-designed current vector controller to regulate the control winding (CW) current. The control scheme is proposed, and the hardware design for the control system is developed. The proposed generator system is tested on a 325 TEU container vessel, and the test results show the good dynamic performance of the CW current vector controller and the whole control system. A harmonic analysis of the output voltage and a fuel consumption analysis of the generator system are also implemented. Finally, the total efficiency of the generator system is presented under different rotor speeds and load conditions.

• Structural Monitoring and Maintenance
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• 제9권2호
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• pp.107-127
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• 2022

Structural health monitoring (SHM) has been related to damage identification with either operational loads or other environmental loading playing a significant complimentary role in terms of structural safety. In this study, a non-parametric method of time frequency analysis on the measurement is used to address the time-frequency representation for modal parameter estimation and system damage identification of structure. The method employs the wavelet decomposition of dynamic data by using the modified complex Morlet wavelet with variable central frequency (MCMW+VCF). Through detail discussion on the selection of model parameter in wavelet analysis, the method is applied to study the dynamic response of both steel structure and reinforced concrete frame under white noise excitation as well as earthquake excitation from shaking table test. Application of the method to building earthquake response measurement is also examined. It is shown that by using the spectrogram generated from MCMW+VCF method, with suitable selected model parameter, one can clearly identify the time-varying modal frequency of the reinforced concrete structure under earthquake excitation. Discussions on the advantages and disadvantages of the method through field experiments are also presented.

• 한국지반환경공학회 논문집
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• 제24권12호
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• pp.61-67
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• 2023

도심지 지하에 위치하며 고온, 고압조건에서 운영되는 열수송관은 파손 시 인적, 경제적으로 대규모 피해가 발생할 수 있다. 파손을 사전에 예측하기 위해 기존 파손이력과 설비이력을 분석하여 파손빈도와 상관관계를 가지는 독립변수를 도출하고, 각 변수를 활용한 단순회귀분석 변형모델이 현장에 적용되고 있다. 다만, 모델에 적용되는 독립변수간 상관관계가 클수록 변수간 독립성이 훼손되어 모델의 신뢰성이 낮아진다. 본 연구에서는 상호 연관성을 가지는 것으로 판단되는 관경, 매설깊이, 감시시스템 절연레벨, 감지선의 단선 또는 단락의 독립성을 검정하여 파손빈도 추정모델에 적용하기 위해 필요한 변수간 결합 및 범주 설정 방안을 도출하였다. 독립성 검정을 위해 연속형 변수인 관경과 매설깊이는 각각 3개의 범주, 감시시스템 절연레벨은 2개의 범주로 변환하였으며, 범주형 변수인 감시시스템 감지선 상태는 범주를 그대로 2개로 유지하였다. 독립성 검정 결과, 관경과 매설깊이간, 감시시스템 절연레벨과 감지선의 단선 또는 단락간 유의확률이 유의수준(α = 0.05)보다 작아 상호간 상관관계가 큰 것으로 나타났다. 따라서 관경과 매설깊이를 하나의 변수로 결합하고 사전에 설정한 범주를 고려하여 결합 변수의 범주는 9개로 설정하였다. 감시시스템 절연레벨과 감지선의 단선 또는 단락 역시 하나의 변수로 결합하였으며, 감지선 상태가 단선 또는 단락인 경우 절연레벨값을 신뢰할 수 없으므로 결합 변수의 범주는 3개로 설정하였다.

• 가정과삶의질연구
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• 제16권4호
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• pp.83-83
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• 1998

The purpose of this study is to investigate interpersonal support, tension in lifechanges & satisfaction. The selected sample is composed of 387 housewives in ChongJoo city. SAS pc program was used for the statistical analysis of the data. Data was analyzed by frequency, F-test, percentage, mean, Duncan's Multiple Range Test, Pearson's correlation coefficient, Regression Analysis. Major findings as follows: 1)At wedding & funeral ceremony, kin networks of her parents & parents-in law side were variables to have influence on tension in life changes. And the number of social organization participated were a variable to have influence on the satisfaction. The age of couple, education of couple, duration of marriage, income, family lifecycle, the number of children, pattern of family were variables to influence tension in life changes, but were not variables to influence on the satisfaction. 2) At usual or wedding & funeral ceremony, kin networks of her parents side were variables to influence on instrumental & companionship support. And the number of friends was a variable to influence on companionship & informational support. The number of neighbors was a variable to influence on instrumental, companionship & informational support. The number of social organization participated was a variable to influence on companionship & emotional support. The age of couple, education of couple,income, duration of marriage, family life cycle, number of children, family size, family type were variables to influence on interpersonal support. 3)The relationship between tension and satisfaction in life changes was negative, and between instrumental support and satisfaction was negative also. But between companionship support and satisfaction was positive relationship and between tension of personal &social life and instrumental support was positive relationship. The relationship between tension of marriage life and companionship support was negative and between tension of family life and information support was negative relationships. The received companionship support was lower tension in life changes than not received it. But the received instrumental support was higher tension of personal & social life. The received companionship & informational support was higher satisfaction than not received them. But the received instrumental support was lower satisfaction than not received it. 4) Instrumental & companionship support, at usual kin network of her parents in taw side, at wedding & funeral ceremony kin network of her parents side,were variables to influence on tension in life changes. Instrumental, companionship& informational support, at wedding & funeral ceremony kin network of her parents side, were variables to influence on the satisfaction

• 한국운동역학회지
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• 제20권3호
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• pp.303-310
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• 2010

The purpose of this study was (a)to compare electromyographic (EMG) activities and physiological variables on the development of fatigue induced by ergometer test, (b)to determine investigate the differences in the stage of fatigue between the electromyographic characteristics and physiological variables. Nine male university students who have no musculoskeletal disorder were recruited as the subjects. The electromyographic characteristics(peak IEMG, average IEMG, median frequency, mean edge frequency) and physiological variables(HR, RPE, blood lactate) were determined for each stage(15, 30, 45, 60 minutes, all out). For each dependent variable, one-way analysis of variance(ANOVA) with repeated measures and correlation analysis were performed to test if significant difference existed(p<.05). The results showed that peak IEMG, average IEMG from low extremity and physiological variables were significantly increased during the all-out stage. EMG parameters in VL, VM show significantly correlation with physiological variables during whole stages. This indicated that IEMG values may be proper parameters to determine muscle fatigue rather than physiological variables.

• 한국의류산업학회지
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• 제3권3호
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• pp.249-256
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• 2001

This study was to investigate difference across socioeconomic groups in factors of purchase intention of apparel in internet shopping mall and in satisfaction were internet shopping mall. A questionnaire was administered to collage students majoring in fashion design during May of 2001. Data was analyzed by using Factor analysis, T-test, one-way ANOVA, Duncan test, ${\chi}^2$-test. Factor analysis yield three factors of purchase intention, purchase stimulus, convenience and economic and rationality. Significant differences were found across levels of monthly pocket money and types of payment for purchase apparel of internet shopping mall purchase stimulus (factor 1). In convenience and economics (factor 2), differences were also significant across levels of purchase frequency, product price and payment ways of internet sopping mall. Significant difference was identified across sex type and levels of product price purchased in internet shopping mall (factor 3). Regarding internet shopping mall satisfaction, differences were significant across levels monthly pocket money and apparel purchase frequency of in internet shopping mall.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.647-653
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• 2009

Taguchi parameter design is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used SN (Signal to Noise) ratio to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. This paper describes the prediction technique of vehicle performance using parameter analysis to reduce man hour and test development period as well as to achieve stable NVH performance. Design engineer could efficiently decide the design variable using parameter analysis database in early design stage. These improvements can reduce the time needed to develop better vehicles.

• 한국위성정보통신학회논문지
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• 제3권1호
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• pp.1-7
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• 2008

본 논문에서는 통신위성시스템 탑재를 위한 Ku-Band 선형화 채널증폭기 비행모델의 설계와 제작된 결과를 고찰하였다. 정착된 모든 서브모듈, 즉 가변이득증폭기, 가변전압감쇠기, 그리고 전치왜곡 보상회로를 위한 브랜치 라인 결합기와 검출기는 Thin-Film Hybrid 작업으로 제작되었다. 제작된 모듈의 성능은 초고주파 회로분석 시뮬레이션 툴과 우주환경에서의 전기적인 성능시험을 통하여 검증하였다.

• 한국ITS학회 논문지
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• 제8권3호
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• pp.83-90
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• 2009

본 논문은 Ku-Band 선형화 채널증폭기를 위한 비행 모델의 설계 및 측정에 관한 것이다. 모든 MMICs, 가변이득증폭기, 가변전압감쇄기, 전치왜곡 보상회로를 위한 브랜치 라인 결합기와 검출기는 Thin-Film Hybrid 작업으로 제작되었다. 제작된 모듈의 성능은 초고주파 회로분석 시뮬레이션 틀과 우주환경에서의 전기적인 성능 시험을 통하여 검증하였다.

• 대한가정학회지
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• 제41권3호
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• pp.31-44
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• 2003

The purpose of this study is to investigate the difference of maternal parenting stress through early childhood between urban(Seoul and Incheon) and rural area(Iksan and Kimpo). The subjects were 286 unemployed mothers who have less than 5-year-old children. The statistics used for this data were frequency, percentile, t-test, ANOVA, and multiple regression. The finding from the present study certainly suggested that mother's level of self-differentiation, marital satisfaction, father's parenting support turned out to a significant variables on maternal parenting stress. Results of the regression analysis that the etiologic model of this study was more proper to urban than rural area, and father's parenting support is the most effective variable in predicting maternal parenting stress in both area. Implications based on this study are as follows ; parenting education programs to encourage for father's parenting support with be developed, and various empirical studies about maternal parenting stress in with area will be needed.