• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1171-1173
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• 2003

There are two datasets to estimate the area-mean and time-mean precipitation rate. For one, an array of surface rain gauges represents a series of rods that have to the time axis of the volume. And another data is that of a remote sensing make periodic overpasses at a fixed interval such as radar. The problem of optimally combining data from surface rain gauge data and remote sensed data is considered. In order to combining remote sensed data with Automatic Weather Station (AWS), we use optimal weighting method, which is similar to the method of [2]. They had suggested optimal weights that minimized value of the mean square error. In this paper, optimal weight is evaluated for the cases such as Changma, summer Monsoon, Typhoon and orographic rain.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.106-108
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• 1987

Until now, inflow has been handled an independent log-normal random variable in the problem of planning the long-term operation of a multi-reservoir hydrothermal electric power generation system. This paper introduces the detail study for making rule curve by applying weekly time interval for handling inflows. The hydro system model consists of a set of reservoirs and ponds. Thermal units are modeld by one equivalent thermal unit. Objective is minimizing the total cost that the summation of the fuel cost of equivalent thermal unit at each time interval. For optimization, stochastic dynamic programming(SDP) algorithm using successive approximations is used.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.742-743
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• 2007

A maintenance plan of power system equipment reduces failure rate caused by equipment's age. To prevent unexpected failure, the maintenance is performed periodically according to the interval time. The more expansive equipment's scale is, the more the maintenance without considering costs sustains a economical loss. Hence, the maintenance's time and the cost must be considered when maintenance which is considering the reliability is implemented. In this paper, optimum maintenance interval is calculated by considering minimum maintenance cost of the equipment with the combined cycle units in Korea power systems.

• Korean Management Science Review
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• v.15 no.2
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• pp.143-152
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• 1998

This paper focuses on the determining the optimal replacement interval and the corresponding minimum cost of replacement for the renewal T-53 engine. It is assumed that sample failure data of T-53 engine are drawn from the mixed population, and then parameters of the failure distributions are estimated. On the basis of the above situation, the Multi-step Weibull distributions are estimated and then the optimal replacement time of T-53 engine is determined. This paper shows that if the replacement time is reduced to 2000 hours, the 2,217won of the replacement cost per unit time is only saved but also reliability of the T-53 engine is increased.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.795-803
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• 2015

Autoreclosure provides a means of improving power transmitting ability and system stability. Conventional reclosure adopts the fixed dead time interval strategy, where the reclosure is activated after a time delay to restore the system to normal as quickly as possible without regard to the system conditions. However, these simple techniques cannot provide optimal operating performance. This paper presents an adaptive autoreclosure algorithm including variable dead time, optimal reclosure, phase-by-phase reclosure and emergency extended equal-area criterion (EEEAC) algorithm in order to improve system stability. The reclosure algorithm performs the operations that are attuned to the power system conditions. The proposed adaptive reclosure algorithm is verified and tested using ATP/EMTP MODELS, and the simulation results show that the system oscillations are reduced and the transient stability is enhanced by employing the proposed adaptive reclosure algorithm.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.12
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• pp.698-704
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• 2003

Autoreclosure provides a mean of improving power transmitting ability and system stability. The conventional reclosure adopts the fixed dead time interval strategy, that is, the reclosure is activated after a time delay to restore the system to normal as quickly as possible without regard to the system conditions, however, these simple techniques cannot give the optimal operating performance. For this reason, various adaptive reclosure algorithms have been proposed recently, This paper presents an adaptive autoreclosure algorithm including the variable dead time, optimal reclosure, sequential reclosure and emergency extended equal-area criterion (EEAC) algorithm in order to improve the system stability. The reclosure algorithm performs out the operations that are attuned to the power system conditions. The proposed adaptive reclosure algorithm is verified and tested by using EMTP MODELS, and the simulation results show that the system oscillations are reduced and the transient stability is enhanced by employing the proposed adaptive reclosure algorithm.

• Journal of Navigation and Port Research
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• v.43 no.6
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• pp.413-419
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• 2019

Traffic routes typically have heavy traffic. Especially, the entrance of the route has a high risk of accidents occurring because of ships entering and exiting the port. However, almost of studies have focused on the distribution of traffic on the route. Thus, studies on the distribution between ships for passing through the route are insufficient. The purpose of this study was to analysis the traffic in the Busan north port No.1 route for one week. Based on present traffic conditions, one gate line was settled on the route with an analysis of traffic conditions. Based on the analysis data, each optimal time probability distribution between ships was divided into inbound/outbound and traffic volume. An analysis of the optimal probability distribution, was applied to 31 probability distributions divided into bounded, unbounded, non-negative, and advanced probability distribution. The KS test was applied for identifying three major optimal time probability distributions. According to the KS test results, the Wakeby distribution is the best optimal time probability distribution on the designated route. Although the optimal time probability distribution for other transportation studies such as on vehicles on highways is a non-negative probability distribution, this distribution is an advanced probability distribution. Thus, the application of major probability distribution for using other transportation studies is not applicable to this study Additionally, the distance between ships in actual traffic surveys and the distance estimated by the optimal probability distribution were compared. As a result of the comparison, those distances were fairly similar. However, this study was conducted in only one major port. Thus, it is necessary to investigate the time between ships and calculate a traffic volume on varying routes in future studies.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.15-17
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• 2000

실시간 시스템에서 예상치 못한 오류 발생은 성능에 악영향을 미친다. 이를 예방하기 위하여 체크포인팅이라는 후방 에러복구기법을 이용하여 오류 발생시에도 예측 가능한 결과를 보장할 수 있다. 실시간 시스템에서의 체크포인팅은 비실시간 시스템과는 달리 시간제약성을 만족시켜야 하기 때문에 비실시간에는 최적인 체크포인팅 간겨곽는 다르게 고려 되어야 한다. 이런 체크포인트 간격에 따른 성능의 차이를 시뮬레이션을 통하여 확인하였고 결과를 분석하였다.

• Korean Journal of Veterinary Service
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• v.15 no.1
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• pp.1-6
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• 1992

A survey on the dosage optimal time for the bovine fascioliasis was carried out from Jan. 1987 to Dec. 1990. The results were summarized as follows ; 1. The mean infection rate was 27.7% (1,662 heads were infected out of 3,247 heads In 205 herds). A seasonal infection rate was winter (34.6%) >spring(32.5%) >summer(24.7%) > autumn(22.8%) 2. In the density of the fasciola spp. egg of infected bovine feces remarks 79.6% on the range below 10. 3. The density of fasciola spp. egg is not directly proportinal to the infection rate, and remarks on the range from 5 to 20. 4. In the herds dosed vermifuge the appearance of the fasciola spp. egg is as follows ; 1∼3 months show 3.8% and 4∼6 months 8.5% 5. The dosage optimal time for the bovine fasciliasis is as follows ; 1) According to the monthly infection rate the first dosage optimal time is Dec and Feb and the second-Jun and Aug. 2) In the herd dosed vermifuge the dosage optimal time is to dose twice by 60 days interval after 3∼4 months from previous dosage.

• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.61-70
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• 2005

The objective of this study was to analyze the smoke movement for the case of fire and to determine the interval between emergency exits in long tunnels. Based on Froude modeling, the 1/50 scaled model tunnel (20 m long) was constructed by acrylic tubes and tests were carried out systematically. From the strong relationship between CO propagation time and distance through the tunnel, it was found that the optimal escaping time was 6 minutes in case of 20MW fire. But, regarding passengers' psychological state under fire, another one minute of delay time should be considered. Therefore, the total escaping time should be estimated by 5 minutes. The interval between the emergency exits for vehicle passengers was calculated by 250 m with respect to the 5 minute of escaping time.