• 한국통신학회논문지
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• 제30권5A
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• pp.382-388
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• 2005

이동 통신 시스템이 발전함에 따라서 점점 더 대용량의 고속 데이터 전송을 할 수 있는 시스템이 필요하게 되었다. 이러한 시스템으로 주목을 받는 것이 OFDM (Orthogonal Frequency Division Multiplexing) 시스템이다. 그러나 OFDM 시스템에서는 ISI (Inter-Symbol Interference)의 영향을 줄이기 위해 보호구간 (Guard Interval)을 삽입하기 때문에 데이터 전송률과 대역폭 효율이 떨어지는 단점이 있다. 본 논문에서는 보호구간이 없는 OFDM 시스템의 성능을 향상시키는 기법을 제안한다. 우선 다중 경로 채널 환경에서 다중 경로 신호를 추정하여 수신된 신호에서 제거함으로써 간섭을 줄일 수 있는 PIC (Parallel Interference Cancellation) 기법에 대해서 살펴본다. 또한 인접 심볼 때문에 생기는 간섭성분에 대한 Cross-Correlation 행렬을 구하고 그것의 역행렬을 이용하여 전송된 신호를 추정하는 Pseudo-Decorrelator 방법을 사용한 성능 향상 기법을 제안한다. 컴퓨터 모의실험을 실시하여 제안된 시스템의 성능을 평가하고, 보호구간이 없는 OFDM 시스템과 PIC기법을 적용한 시스템의 성능과 비교한다.

• 한국물환경학회지
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• 제28권4호
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• pp.595-600
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• 2012

This study is to assess the application of SWAT-CUP(Soil and Water Assessment Tool-Calibration Uncertainty Programs) and to extend daily flow data from 8-day interval flow data which has been measured by Korean Ministry of Environment(MOE). Model sensitivity analysis and calibration were performed with sequential uncertainty fitting(SUIF-2), which is one of the programs interfaced with SWAT, in the package SWAT-CUP. The most sensitive parameters were SOL_K.sol, CH_N2.rte, CN2.mgt, SOL_BD.sol, ALPHA_BF.gw, ALPHA_BNK.rte, SOL_AWC.sol, CH_K2.rte, SFTMP.bsn, GW_DELAY.gw. Following the sensitivity analysis, SWAT-CUP calibration was carried out using 8-day interval flow data from January 2008 to December 2010. The results were then assessed based on the visual agreement and simulated flow plots and the performance statistics generated $R^2$ and NSE which are 0.71 and 0.61 respectively. Results of these statistics indicated that there was a good agreement between the observed and simulated flow. To extend daily flow data from 8-day interval flow data, parameters, which were estimated by SWAT-CUP, re-entered for SWAT model. As a result, the observed flow data were found to reflect the trend of simulated flow data. From these results, it is thought that this method could be used to provide daily flow data using 8-day interval flow data.

• Journal of applied mathematics & informatics
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• 제6권2호
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• pp.553-568
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• 1999

This paper is of concern to queueing analysis of the dynamic rate leaky bucket(LB) scheme in which the token generation interval changes according to the buffer state at a token generation epoch. Cell arrivals are assumed to follow a Markovian arrival process (MAP) which is weakly dense in the class of the stationary point processes. By using the embedded Markov chain method we obtain the probability distribution of the system state at a token generation epoch and an arbitrary time. Some simple numerical examples also are provided to show the effects of the proposed LB scheme.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.136.2-136.2
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• 2011

In this work, we analyzed correlations between life-cycle greenhouse gas (GHG) emissions and life-cycle cost of energy resources. Energy resources studied in this paper include coal, natural gas, nuclear power, hydropower, geothermal energy, wind power, solar thermal energy, and solar photovoltaic energy, and all of them are used to generate electricity. We calculated the mean values, ranges of maximum minus minimum values, and ranges of 90% confidence interval of life-cycle GHG emissions and life-cycle cost of each energy resource. Based on the values, we plotted them in two dimensional graphs to analyze a relationship and characteristics between GHG emissions and cost. Besides, to analyze the technical maturity, the GHG emissions and the range of minimum and maximum values were compared to each other. For the electric generation, energy resources are largely inverse proportional to the GHG emission and the corresponding cost.

• 한국안전학회지
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• 제7권2호
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• pp.5-13
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• 1992

If zero-accident movement is to be successful, the objective goal period should be surely obtainable, and much more in our country where frequency rate of injury are remarkably fluc-tuating. However In our country, as far as we know, no method to establish a reasonable zero-accident goal period is guaranteed. In thls paper, a new establishing-method of reasonable goal period for individual industry with considering recent accident trend is presented. A mathematical model for industrial accidents generation was analyzed, and a stochastic process model for the accident generation inteual was formulated. This model could tell the accident generation rate in future by understanding the accident tendency through the time-series analysis and search for the distribution of numbers of accidents and accident interval. On the basis of this, the forecasting method of goal achievement probability by the size and the establishment method of reasonable goal period were developed.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1709-1718
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• 2017

This paper presents a hybrid stochastic deterministic multi-timescale scheduling (SDMS) approach for generation scheduling of a power grid. SDMS considers flexible resource options including conventional generation flexibility in a chance-constrained day-ahead scheduling optimization (DASO). The prime objective of the DASO is the minimization of the daily production cost in power systems with high penetration scenarios of variable generation. Furthermore, energy storage is scheduled in an hourly-ahead deterministic real-time scheduling optimization (RTSO). DASO simulation results are used as the base starting-point values in the hour-ahead online rolling RTSO with a 15-minute time interval. RTSO considers energy storage as another source of grid flexibility, to balance out the deviation between predicted and actual net load demand values. Numerical simulations, on the IEEE RTS test system with high wind penetration levels, indicate the effectiveness of the proposed SDMS framework for managing the grid flexibility to meet the net load demand, in both day-ahead and real-time timescales. Results also highlight the adequacy of the framework to adjust the scheduling, in real-time, to cope with large prediction errors of wind forecasting.

• KIEE International Transactions on Power Engineering
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• 제2A권3호
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• pp.83-88
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• 2002

An over current relay(OCR), one of the most frequently used protective devices, has time-current characteristics (TCC) to control its trip time according to the current level. It is because an appropriate operating time interval is necessary for coordination with other protective devices. A set of TCC curves of an OCR is, in general, given by the supplier from which a curve is selected by the operator. Therefore, in many cases, it is impossible to consider the operation condition of the given power system exactly. A novel concept of an OCR is suggested in this paper. The proposed OCR has an internal correction module so that it may produce the most adequate TCC curve according to the given protective information for coordination with other devices. With the generated TCC curve, a variety of operation and coordination conditions can be taken into consideration in an effective manner. The suggested OCR is applied to a simple test power system to show very promising results from a coordination point of view.

• 전기학회논문지
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• 제60권3호
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• pp.509-516
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• 2011

This paper studies a novel method to find the profit-maximizing Nash Equilibriums in allocating generation quantities with consideration of ramp-rates under competitive market environment. Each GenCo in a market participates in a game to maximize its profit through competitions and play a game with bidding strategies. In order to find the Nash equilibriums it is necessary to search the feasible combinations of GenCos' strategies which satisfy every participant's profit and no one wants various constraints. During the procedure to find Nash equilibriums, the payoff matrix can be simplified as eliminating the dominated strategies. in each time interval. Because of the ramp-rate, generator's physically or technically limits to increase or decrease outputs in its range, it can restrict the number of bidding strategies of each generator at the next stage. So in this paper, we found the Nash Equilibriums for multi-stage generation allocation game considering the ramp-rate limits of generators. In the case studies, we analyzed the generation allocation game for a 12-hour multi-stage and compared it with the results of dynamic economic dispatch. Both of the two cases were considered generator's ramp-rate effects.

• 전자공학회논문지
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• 제51권11호
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• pp.19-25
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• 2014

효과적인 블라인드 등화기 갱신을 위해, 등화 초기에 요구되는 빠른 수렴 속도와 정상상태에서 요구되는 낮은 오차 레벨을 만족하면서, 또한 등화 초기와 정상상태 간의 완만하면서도 가역적인 전환 특성을 가지는 적응 알고리즘을 제안한다. 제안 방법에서는 신호의 등화 상태를 구분하는 세 기준을 제시하고, 이 기준에 따라 세 오차 중 하나를 발생시키는 하이브리드 오차발생 알고리즘을 사용하여 등화기를 차등적으로 갱신한다. 이때 신호의 등화 상태를 판단하는 기준으로 신호 성상도 상의 신뢰구간을 이용하였으며, 등화기 출력이 놓이는 신뢰구간에 따라 오차를 다르게 발생시켜 등화기를 갱신함으로써 빠르게 그리고 낮은 오차 레벨에 수렴할 수 있음을 보였다. 제안 아이디어의 유용성을 검증하기 위해 모의실험을 통해 기존 방법의 성능과 비교하였다.

• 플랜트 저널
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• 제9권4호
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• pp.37-42
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• 2013

화력발전소와 같은 대규모 플랜트 설비는 복잡하여 고장이 발생할 경우 고장발생 설비, 시기 및 원인을 정확하게 파악하는 것이 쉽지 않기 때문에 무엇보다 고장을 사전에 예방하는 것이 중요하다. 최근 들어 정비업무에 대한 관점과 중요성이 점차 변화해 가고 있고 주기정비 방식에서 벗어나 상태기반 정비방식으로 발전되고 있다. 본 연구에서는 상태정비에 주안점을 두고 신뢰도중심정비 방법을 화력발전소, 특히 석탄취급설비에 적용하여 정비주기를 선정하고자 하였다.