• Computers and Concrete
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• 제1권3호
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• pp.285-302
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• 2004

A FE-(FE-HE)-BE procedure is presented for dynamic analysis of concrete arch dams. In this technique, dam body is discretized by solid finite elements, while the reservoir domain is considered by a combination of fluid finite elements and a three-dimensional fluid hyper-element. Furthermore, foundation rock domain is handled by three-dimensional boundary element formulation. Based on this method, a previously developed program is modified, and the response of Morrow Point arch dam is studied for various conditions. Moreover, the effects of canyon shape on response of dam, is also discussed.

• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.172-177
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• 2007

Wavelet transforms provide basis functions for time-frequency analysis and have properties that are particularly useful for the compression of analogue point on wave transient and disturbance power system signals. This paper evaluates the compression properties of the discrete wavelet transform using actual power system data. The results presented in the paper indicate that reduction ratios up to 10:1 with acceptable distortion are achievable. The paper discusses the application of the reduction method for expedient fault analysis and protection assessment.

• 한국환경과학회지
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• 제16권5호
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• pp.583-591
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• 2007

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years (2000-2003) data at Chuncheon. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for 2-4 hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1 m/s. Especially, about 42 % of foggy day fell on the calm($0{\sim}0.2m/s$) conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water sur-face temperature was calculated by using Water Quality River Reservoir System (WQRRS). In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• 대한기계학회논문집
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• 제16권5호
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• pp.910-923
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• 1992

본 연구에서는 가장 응용 빈도가 큰 크랭크-레버 4절 기구를 제작하고 강성과 유연성 두가지 베어링을 사용하여 연결봉과 레버의 중점의 변형률을 스트레인 게이지 로 측정하여 앞의 이론 논문에서 수행한 수치해석의 결과와 비교 검토하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.361-364
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• 2003

The safe operation and reliable maintenance of nuclear power plants is one of the most fundamental and important tasks. It is known that a loose part such as a disengaged and drifting metal inside of reactor coolant systems might lead to a serious damage because of their impact on the components of the coolant system. In order to estimate the impact position of a loose par, three accelerometers attached to the wall of the coolant system have been used. These accelerometers measure the vibration of the coolant system induced by loose part impact. In the conventional analysis system, the low pass filtered version of the vibration data was used for the estimation of the position of a loose part. It is often difficult to identify the initial point of the impact signal by using just a low passed time signal because the impact wave is dispersed during propagation into the sensor. In this paper, the impact signal is analysed by use of various time frequency methods including the short time Fourier transform(STFT), the wavelet transform, and the Wigner-Vill distribution for finding a convenient way to identify the starting point of a impact signal and their advantages and limits are discussed.

• Journal of Power Electronics
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• 제17권6호
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.

• 한국습지학회지
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• 제20권4호
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• pp.338-344
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• 2018

본 연구에서는 기후변화에 따른 극한 강우의 비정상성을 반영하기 위하여 GEV 분포의 3개 매개변수 중 위치매개변수를 공변량으로 적용하여, 지표면 기온(Surface air temperature, SAT) 및 이슬점 온도(Dew point temperature, DPT)을 고려한 비정상성 빈도해석이 실시된다. 부산 지점이 연구대상지점으로 선정되었으며, 5월부터 10월까지의 월 최대 일강수량을 이용하여 분석을 수행하였다. GEV 분포의 위치 매개변수를 위한 가장 적절한 공변량(기온과 이슬점 온도) 함수를 선택하기 위하여 다양한 모델을 구성하였으며, 구성된 모델 중 AIC(Akaike Information Criterion)가 가장 작은 모델을 최적 모델로 선정하였다. 분석 결과, exp(DPT)가 공변량인 비정상성 GEV 분포가 가장 적합한 것으로 나타났다. 선택된 모델을 이용하여 기후변화 시나리오에 따른 확률강우량의 영향을 분석하였으며, 부산지점의 경우 미래 이슬점 온도가 증가함에 따라 확률강우량이 증가할 가능성이 매우 높음을 살펴볼 수 있었다.

• 산업기술연구
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• 제16권
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• pp.139-145
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• 1996

Many of the bridge systems, including the girders and cross-beams, and concrete decks behave as the special othotropic plates. A method of calculating the natural frequency corresponding to the first mode of vibration of beam and tower structures with irregular cross-sections was developed and reported by D. H. Kim in 1974. Since 1989, The author has extended this method to Vibration analysis of two dimensional problems including composite laminates, and has reported at several conferenes. Frequently, the bridge floor panels are supported by girders and cross beams. Such panels as well as some of the building floor panels can be assumed as simple supported special orthotropic plates. In this paper, the result of application of simple method of vibration analysis developed by D. H. Kim, to the simply supported sandwich panels with point Mass/Masses is presented.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.435-440
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• 2006

In order to understand changes of water temperature for thermal discharge of Hadong power plant in Gwangyang and Jinju Bay, it was analyzed for temperature data of representative season by MEM(Maximum entropy method) that is one of the spectral analysises. And due to understand effect of thermal discharge at each point, analyzed spectral data showed reactive energy rate of reference point by calculating energy from 24 time period to height frequency zone. As a result of spectral analysis, it showed that there were 9 points which are largely effected, 7 points which will be estimated, 6 points which is difficult to estimate, 14 points which rarely effected by thermal discharge.

• 대한지역사회영양학회지
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• 제21권1호
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• pp.37-52
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• 2016

Objectives: This study was performed to develop an assessment tool for middle aged women's health status based on dietary patterns, which will have practical applications in the working field of health and hygiene, aiming at improving the middle aged women's quality of life through their health improvement. Methods: As a first step, a literature review was conducted and the original data of '2008~2009 Korea Health and Nutrition Examination Survey' were reanalyzed. This analysis identified 65 preliminary questions that may be relevant to the study. After verifying the content validity by experts, the 65 questions were reduced into 51 questions. In order to secure higher validity of the candidate items, verification of their clinical validity was conducted among women aged between 45 and 60 years. Finally, an assessment tool was developed by applying weight and scoring. Results: Selected 51 questions were used to verify clinical validity and the results showed that 20 questions were relevant, nine questions ('regular meal time', 'regular amount of meal', 'intake frequency of dairy products', 'intake frequency of fruits', 'intake frequency of meat products', 'intake frequency of high cholesterol foods', 'intake frequency of salty foods', 'appetite', 'eat breakfast everyday') were related to dietary life. Eleven other questions ('self-rated health status', 'deep sleep', 'smoking', 'frequency of drinking', 'stress levels', 'health-related fitness levels', 'pounding of the heart', 'strange feelings on the skin', 'interfere with daily life', 'menopause will bring you a chance to see the life in a different perspective', and 'body mass index') were selected as valid questions. For the response scale for each question, 5 point Likert scale was used to make total 100 point score. Conclusions: This study is the first attempt to develop a health status assessment tool for middle aged women based on their dietary patterns. We conclude that this tool is expected to be a useful and practical tool in the field.