• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.290-293
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• 2002

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. However, most of these employ switching devices, such as FETs and the like. The absence of switching devices makes systems more tolerant to over-load, and brings low radio noise benefits. We propose a power factor connection scheme using a LC resonant in commercial frequency without switching devices. In this method, It makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence, the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh orders are much reduced. The result are confirmed by the theoretical and experimental implementations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1235-1237
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• 2003

For small capacity rectifier circuits as these for consumer electronics and appli capacitor input type rectifier circuits are gen used. Consequently. various harmonics gen within the power system become a serious pro Various studies of this effect have been pres previously. However. most of these employ swit devices, such as FETs and the like. The absen switching devices makes systems more toleran over -load, and brings low radio noise benefits propose a power factor correction scheme using resonant in commercial frequency without swit devices. In this method. It makes a sinusoidal by widening conduction period using the cu resonance in commercial frequency. Hence, harmonic characteristics can be significantly imp where the lower order harmonics. such as the and seventh orders are much reduced. The resu confirmed by the theoretical and experm implementations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2146-2148
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• 2003

This paper present a modified repetitive control scheme for an optical storage system to track a periodic reference signal with dynamic change in period. Periodic disturbances can be adequately attenuated using the concept of repetitive control, provided the period is know. An optical storage system supports various speeds. To deal with time varying periodic disturbances, an proposed repetitive controller is turned based on repetitive control to change sampling frequency to follow the change of reference Period. A modified repetitive control scheme is proposed and implement on experimental set up of a optical disk driver.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.616-624
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• 2015

Flashover of power transmission line insulators due to contamination is a major threat to the reliable operation of power system. This paper deals with the analysis of leakage current characteristics of polymeric insulator using S-Transform technique in order to develop a better diagnostic tool to identify the surface condition of outdoor polymeric insulators. In this work, experiments were carried out on 11 kV silicone rubber insulator under AC voltage at different pollution levels. Moving average technique was adopted to find the trend followed by LC peak at different relative humidity conditions. S-Transform was used to find the relationship between energy and frequency content of the leakage current signal with respect to increase in pollution level over a period of time. From the S-Transform time-frequency contour analysis, point of transition to severe arcing due to increase in pollution and its thershold limit were evaluated. Reported results show that the surface condition of insulators could be easily identified from the S-Transform time-frequency analysis of leakage current signals.

• 대한한의학회지
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• 제21권4호
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• pp.227-235
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• 2000

Background and Purpose : Medical and Neurological complications in patients with acute stroke may affect their prognosis including death rate, function and admission period. Some of these complications may be preventable. But few data exist regarding complications occurring in the first weeks. So we sought to observe the type, timing, and frequency of complications in hospitalized patients after stroke. Methods : We retrospectively examined the case notes of patients admitted in Won Kwang Oriental Medical Hospital after stroke. Two observers inspected the case notes using predifined diagnostic criteria and recorded the type, timing, and frequency of complications that occurred during the inpatient period. Results : Complications were recorded in 43 patients(82.7%). The most common medical complications were constipation(25.0%) and shoulder pain(21.2%). The most frequent serious medical problems were pulmonary infection(9.6%) and UTI(7.7%). The most common neurological complications were insomnia(34.6%) and dysphagia(23.7%). The most frequent serious medical problem was mental deterioration(7.7%). Conclusion : Complications after acute stroke are common. There were more medical complications than neurological complications. So we should compile much knowledge about medical complications and treat them actively. The differences between our study and previous studies are attributable to the different methods including patient selection and diagnostic criteria.

• ETRI Journal
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• 제37권2호
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• pp.273-282
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• 2015

Vehicle-to-grid presents a mechanism to meet the key requirements of an electric power system, using electric vehicles (EVs) when they are parked. The most economic ancillary service is that of frequency regulation, which imposes some constraints regarding the period and duration of time the vehicles have to be connected to the grid. The majority of research explores the profitability of the aggregator, while the perspective of the EV fleet owner, in terms of their need for usage of their fleet, remains neglected. In this paper, the optimal allocation of available vehicles on a day-ahead basis using queuing theory and fuzzy multi-criteria methodology has been determined. The proposed methodology is illustrated on the daily scheduling of EVs in an electricity distribution company.

• 대한전자공학회논문지
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• 제24권2호
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• pp.196-200
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• 1987

The following methods are proposed for implementing digital dual tone multi-frequency (DTMF) receiver: using infinite impulse response(IIR) digital filters, period-counting algorithm, discrete Fourier transform(DFT), and fast Fourier transform(FFT)[2]. The PARCOR(Partical Correlation) analysis method which has been widly used in the speech signal processing area is applied to the dual tone multi-frequency(DTMF) signal detection. This method is easy to implement digitally and stronger to digit simulation of speech than any other methods proposed up to date. Since sampling rate of 4KHz is used in the DTMF receiver for the detection of input DTMF signal originally sampled at 8KHz, it effects two times higher multiplexing efficiency.

• 대기
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• 제21권4호
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• pp.361-371
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• 2011

In this study, characteristics and trends of tropical night (TN) are investigated by using the KMA 14 observation data for the recent 50 years (1958-2007) over South Korea. The TN is defined as a day with a daily minimum temperature exceeds the absolute threshold temperature ($25^{\circ}C$), and the relative deviation from normal temperature, 95th percentile of all observed daily minimum temperature. Although the spatial distribution of TN occurrence depends on the choice of the definitions, the frequency of TN shows strong spatial and interannual variations with the minimum at high land area (Chupungnyeong and wet years) and maximum at southern coastal area and large city area (Jeju, Busan, Seoul, Daegu). Most of TN occurs in August (56%) and July (41%), and the duration date of TN is proportional to the frequency of TN without regard to the definition method. In general, increasing trends are found in the TN time series without regard to the analysis method, but the trends are clearly depending on the analysis period and geographic locations. Decreasing trends are prominent during the most of analysis period, especially until the mid of 1990, whereas strong increasing trends are found during recent 30 years (1988-2007), especially at Jeju, Ulsan, Daegu and Pohang. Also the severity of TN is significantly increased in recent years.

• 한국방재학회 논문집
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• 제2권3호
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• pp.89-99
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• 2002

본 연구에서는 가뭄빈도공식을 이용해서 목포지역의 가뭄을 평가하고자 하였으며, 이를 위해 Sharma(1997)가 제안한 가뭄빈도공식을 이용한 가뭄빈도해석을 실시하였다. 본 연구에서 적용된 가뭄빈도공식은 빈도계수법 형태인 연강수량 자료계열을 이용하였으며, 5년 가뭄빈도보다 큰 가뭄을 가뭄년으로 선정하고, 대상지역에 대한 과거 가뭄을 평가하였다. 이를 통해 목포지역의 가장 큰 가뭄은 1995년에 발생하였으며, 그 해의 연강수량은 613.2mm로서 30년 가뭄빈도에 해당됨을 알 수 있었다.

• 한국수자원학회논문집
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• 제48권12호
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• pp.969-979
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• 2015

본 연구에서는 가뭄의 특성분석에 유리하며, 확률론적 접근이 가능한 은닉 마코프 모델(HMM) 기반의 가뭄 분석 기법을 적용하였다. HMM 기반의 가뭄의 심도뿐만 아니라 지속시간을 동시에 평가할 수 있도록 코플라 함수 기반의 이변량 가뭄빈도해석 기법을 도입하여 우리나라의 2015년 가뭄 빈도를 평가하였다. 가뭄빈도분석 결과 최근 40년 자료를 기준으로 영동지방에 비해 영서지방이 전체적으로 가뭄이 발생할 경우 가뭄의 심도가 큰 것으로 평가되었다. 심한가뭄의 발생 비율의 경우에 철원의 경우 10%를 상회하는 등 임진강 유역에서 상대적으로 심한가뭄의 발생비율이 크다는 것을 확인할 수 있었다. 한강유역 일부지점에서는 2014/2015년의 가뭄 지속기간 및 심도의 결합재현기간이 1,000년이 넘는 가뭄이 발생하고 있는 것으로 평가되었다. 특히 북한강 및 임진강 유역에 심한 가뭄이 발생하고 있으며 전반적으로 100년 이상의 기왕최대가뭄을 나타내고 있는 것으로 판단되었다.