• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 가을 학술발표논문집 Vol.30 No.2 (3)
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• pp.175-177
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• 2003

본 논문에서는 직교 주파수 분할 다중화 전송방식(OFDM:Orthogonal Frequency Division Multiplexing)에서 비트 오류율(BER)과 시스템에서 사용할 수 있는 총 송신 파워가 제한된 상태에서 데이터 전송률을 최대화 시키는 기법을 제안한다. 제안한 기법은 미리 계산된 비트수별 신호대잡음비 임계값(threshold)과 부반송파의 신호대잡음비를 비교한 후 부반송파별 송신 파워를 최적화 시켜 비트를 할당한다. 이 기법은 송신 파워 및 비트를 할당하는 최적의 기법이라고 알려진 Hughes­Hartogs 기법과 거의 동일한 데이터 전송률을 가질 수 있으면서, 부반송파의 송신 파워 및 비트수를 할당하기 위해 필요한 반복작업을 줄일 수 있다.

• 산업경영시스템학회지
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• 제6권9호
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• pp.97-110
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• 1983

As the economic society develops very exceedingly, the gap of production and consumption elarges gradually. So the current function to connect them and the function to communicate are needed. I think the advertisement take the charge of this role. This advertisement is so essential to today's economic society that its power influences variably both the economic society and the consumers. The enterprisers, advertising owners stick to the maximization of profits and neglect the principle of true advertisements. They but tise not the information for the consumers to choose reasonably but the false, exaggerating advertisement and unfair manifestation very frequently, which is the main trouble in the current problems of consumption. Therefore, on the one hand, in this study from protecting the consumers not to be involved in the false, exaggerating advertisements, the establishment of advertising ethics as advertising owner's self-control is discussed. On the other hand, the legal control regulation in Korea, involving Japan and U.S.A. are analyzed. The cases of false, exaggerating advertisements and unfair manifestation in Korea are also demonstrated. Finally, the proposals to improve the advertisements are made from the Point of government, enterprisers, and consumers.

• 대한안전경영과학회지
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• 제8권3호
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• pp.125-141
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• 2006

If do not become whole optimization because enterprise's individual enterprise internal determinate improvement effort is associated with activity in enterprise SCM, competitive power can not but be extremely limited the result. Therefore, to spur in hidden cost's discovery and logistics' optimization is actuality. In this paper, as long as it is by logistics cost except empty driving if reverse logistics happens in distribution channel progressing, logistics reverse logistics' hidden cost through model that do minimization profit of logistics to look for plan that can do maximization try. Finally, is based on dual of distribution cost and profit of logistics and reverse logistics and achieves Pull, optimal system modeling that use Push system and gropes method of effective logistics cost.

• 한국지능시스템학회논문지
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• 제7권5호
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• pp.77-85
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• 1997

본 연구에서는 발전기 보수유지계획 수립을 위하여 퍼지 다목적함수를 이용한 새로은 방법을 제시한다. 보수유지 지연비용의 최소화의 발전기 공급예비력의 최대화를 퍼지 다목적함수로 삼았다. 퍼지론적인 환경을 갖는 보수유지계획의 최적점을 구하기 위하여 퍼지 다목적 정수계획법을 이용하였다. 본 연구의 중요 특성은 기존의 불확실성을 갖는 크리스프적인 제약조건을 퍼지제약으로 처리함으로써 보다 유연한 해를 구할 수 있다는 점이다. 모델계통에 대한 사례연구를 통하여 이번에 개발한 수법의 효용성을 보였다.

• 전기학회논문지P
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• 제65권3호
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• pp.151-157
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• 2016

This paper proposes the variable wind generation system based on the direct torque control(DTC)for the interior permanent magnet synchronous generator. The proposed system can achieve the MPPT control without wind speed in addition to the speed and position sensorless control as well as the conventional current control method. The DTC has several advantages such as simply system configuration, ease of the flux weakening control and the sensorless control. The experimental results show the performance of the proposed wind generation system.

• 품질경영학회지
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• 제39권2호
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• pp.320-328
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• 2011

This research proposes comprehensive models for analyzing common cause failures (CCF) due to cumulative shocks and to assess system reliability under the CCF. The proposed cumulative shock models are based on the binomial failure rate (BFR) model. Six kinds of models are proposed so as to explain diverse cumulative shock phenomena. The models are composed of the initial failure probability, shape parameter, and the total shock number. Some parameters of the proposed models can not be explicitly estimated, so we adopt the Expectation-maximization (EM) algorithm in order to obtain the maximum likelihood estimator (MLE) for the parameters. By estimating the parameters for the cumulative shock models, the system reliability with CCF can be assessed sequentially according to the number of cumulative shocks. The result can be utilizes in dynamic probabilistic safety assessment (PSA), aging studies, or risk management for nuclear power plants. Replacement or maintenance policies can also be developed based on the proposed model.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(II)
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• pp.829-836
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• 2002

The paper presents a multi-objective genetic algorithm approach to the design of a water distribution network. The objectives considered are minimization of network cost and maximization of a reliability measure. In this study, a new reliability measure, called network resilience, is introduced. This measure mimics a designer's desire of providing excess power at nodes and designing reliable loops with practicable pipe diameters. The proposed method produces a set of Pareto-optimal solutions in the search space of cost and network resilience. Genetic algorithms are observed to be poor in handling constraints. To handle constraints in a better way, a constraint handling technique that does not require a penalty coefficient and applicable to water distribution systems is presented. The present model is applied to two example problems, which were widely reported. Pipe failure analysis carried out on some of the solutions obtained revealed that the network resilience based approach gave better results in terms of network reliability.

• ETRI Journal
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• 제41권3호
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• pp.298-307
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• 2019

This paper investigates the use of the inverse-free sparse Bayesian learning (SBL) approach for peak-to-average power ratio (PAPR) reduction in orthogonal frequency-division multiplexing (OFDM)-based multiuser massive multiple-input multiple-output (MIMO) systems. The Bayesian inference method employs a truncated Gaussian mixture prior for the sought-after low-PAPR signal. To learn the prior signal, associated hyperparameters and underlying statistical parameters, we use the variational expectation-maximization (EM) iterative algorithm. The matrix inversion involved in the expectation step (E-step) is averted by invoking a relaxed evidence lower bound (relaxed-ELBO). The resulting inverse-free SBL algorithm has a much lower complexity than the standard SBL algorithm. Numerical experiments confirm the substantial improvement over existing methods in terms of PAPR reduction for different MIMO configurations.

• 한국항공우주학회지
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• 제31권8호
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• pp.99-106
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• 2003

본 논문에서는 액체추진로켓용 터보펌프내 초음속 충동형 터빈의 공력성능 향상을 위해 기하학적 설계변수를 수치적으로 연구하였다. 터빈의 기하학적 설계변수는 아랫면, 윗면 원호반경, 입사각, 익단두께로 설정, 적절한 구속조건을 도입하였고 목적함수로는 최대파워를 채택하였다. 목적함수를 얻기 위해 2-D Navier-Stokes 방정식과 Chien의 k-$\varepsilon$ 난류 모델링을 수치적으로 계산하였다. 초기모델에서 이형 중앙부에 흐름박리를 볼 수 있었으나 개선된 익형에서 흐름박리는 제거되었다. 본 연구를 통해 약 3.2 %의 축 파워가 증대되었다.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1777-1788
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• 2017

This paper presents the design and dynamic analysis of a stand-alone microgrid with high penetration of renewable energy. The optimal sizing of various components in the microgrid is obtained considering two objectives: minimization of levelized cost of energy (LCOE) and maximization of renewable energy penetration. Integrating high renewable energy in stand-alone microgrid requires special considerations to assure stable dynamic performance, we therefore develop voltage and frequency control method by coordinating Battery Energy Storage System (BESS) and diesel generators. This approach was applied to the design and development of Gasa Island microgrid in South Korea. The microgrid consists of photovoltaic panels, wind turbines, lithium-ion batteries and diesel generators. The dynamic performance of the microgrid during different load and weather variations is verified by simulation studies. Results from the real microgrid were then presented and discussed. Our approach to the design and control of microgrid will offer some lessons in future microgrid design.