• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.1
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• pp.62-67
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• 2003

An important aspect of the study of power system markets involves the assessment of strategic behavior of participants for maximizing their profits. In models of imperfect competition of a deregulated electricity system, the key task is to find the Nash equilibrium. In this paper, the bimatrix approach for finding Nash equilibria in electricity markets is investigated. This approach determines pure and mixed equilibria using the complementarity pivot algorithim. The mixed equilibrium in the matrix approach has the equal number of non-zero property. This property makes it difficult to reproduce a smooth continuous distribution for the mixed equilibrium. This paper proposes an algorithm for adjusting the quantization value of discretization to reconstruct a continuous distribution from a discrete one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1033-1043
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• 1999

We consider an improved multicarrier(MC) CDMA system that combines both DS-CDMA with a concatenated orthogonal/PN spreading sequence and MC modulation. This system incorporates the advantages of DS-CDMA with a concatenated sequence to achieve large user capacity and MC modulation technique to combat the effects of a multipath fading channel and intersymbol interference(ISI). Considering voice activity and imperfect sectorization, the system performance is analysed for the maximal ratio combiner(MRC) under a multicell, multiuser, and multipath Rayleigh/Rician fading channels. The performance of the system is improved much more for the single path fading channel compared to the multipath fading channel. Also the system is shown to have the more improved average bit error rate(BER) over the orthogonal MC-CDMA with the conventional PN sequence.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.49-54
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• 2009

One of the major challenges confronting a multiservice electric utility is the establishment of the right prices for its services. The key objectives of particular pricing schemes are reasonableness of company earnings, economic efficiency, the responsiveness of supply and of the allocation of sources to the desires of consumers, and maintenance of some degree of competition. This paper proposes a value-based pricing mechanism amenable to the current deregulation situation in electricity market allowing service differentiation. The proposed pricing mechanism can be implemented in a nodal auction model, and can also be applied to direct load control.

• Journal of Korean Institute of Industrial Engineers
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• v.15 no.1
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• pp.1-15
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• 1989

In the past few years, increasing numbers of automatic storage/retrieval system (AS/RS) using computer controlled storage/retrieval machine have been installed. This paper introduces two modeling approaches to determine the best operating policy for AS/RS : an M/G/1 queueing model and a computer simulation model. The operating policy consists of three elements. : the operation command cycle, the storage location method, and the operation dispatching rule. The analysis based on M/G/1 model is suitable for a quick and approximate evaluation, due to its inherent strict assumptions. The computer simulation can be used to perform a more realistic analysis. It is shown through the study that a significant improvement in the throughput and/or the space requirement can be expected by determining the best operating policy to a particular system. Most important, the computer simulation demonstrates its powerful capability in evaluating dynamic stochatic systems with imperfect information.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.2
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• pp.255-265
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• 1995

Due to advances in automated manufacturing systems and automatic inspection equipment, complete inspection has drown increased attention recently and has become a widespread practice. In a complete inspection plan all of the items are subject to acceptance inspection If an item fails to meet the predetermined specifications, it is rejected. In this paper, economic complete inspection plans are developed in situations where rejected items are reworked Complete inspections based on the performance variable of interest or a variable which is correlated with the performance variable are considered. Cost models are constructed which involve cost incurred by imperfect quality rework cast and quality inspection cost Methods of finding the optimal complete inspection plans are presented and numerical examples are given.

• Journal of Korean Institute of Industrial Engineers
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• v.40 no.2
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• pp.233-239
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• 2014

This paper presents an extended EMQ model which determines an optimal production run length in an deteriorating production process. The production process is subject to a random deterioration from an in-control state to an out-of-control state and thus producing some proportion of defective items. Defective items produced are re-processed in the rework process to convert them into non-defectives. Through the mathematical modeling, an optimal solution minimizing the average cost per unit time as well as minimum average cost are derived. Numerical experiment is carried out to examine the behavior of the proposed model depending on model parameters.

• Journal of the Korean Institute of Navigation
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• v.14 no.1
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• pp.39-55
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• 1990

Numerical model simulations are conducted for the evaluation of the water level variation in and out of the harbor due to the development and improvement of a harbor. The method used for the numerical analysis is the hybrid element method which includes energy dissipation due to imperfect reflection at the shore boundary and friction at the bottom. The model also includes the radiation condition on the open boundary by the analytic formulation and is applied to a real harbor, Guryongpo Harbor at the east coast of Korea. The result of experiment within the selected wave frequency band shows that the amplification factor out of the harbor is more than 2.0 at 32 sec period and strong responses near 20 sec, 25 sec, 54 sec periods in the harbor. Moreover, simulation results indicate that other longer wave periods affect to the variation of water level and horizontal water particle velocity exist. Thus, it seems to be necessary to modify the planform and the design of the harbor structures for the coming development.

• Information and Communications Magazine
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• v.17 no.5
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• pp.66-76
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• 2000

본 논문은 IS-95 CDMA 환경에서 수신 안테나 어레이로 입사되는 신호를 처리하여 최적의 빔패턴을 단말기로 제공해주는 새로운 적응 알고리즘인 그래디언트 온-오프(gradient on-off) 알고리즘을 제안한다. 본 제안 알고리즘의 수신 신호처리 계산량은 O(3N)으로 IS-95 CDMA 환경에서 범용 DSP(Digital Signal Processor)를 이용한 알고리즘 계산결과 수신신호의 실시간 처리가 가능한 것이 판명되었다. 제안한 그래디언트 온-오프 알고리즘을 이용하여 IS-95 CDMA 이동통신 환경하에서 시뮬레이션을 수행한 결과 8개의 안테나를 사용한 경우 단일 안테나보다 약 3-4배 정도 용량이 증가하였다. 또한 사용자간의 최대 파워치를 ${\pm}$2dB로한 불환전한(imperfect) power control 시에도 본 제안 알고리즘에 대한 성능에는 영향이 거의 없음을 확인하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.4
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• pp.199-204
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• 2005

In an electricity market with an imperfect competition, participants make plans of bidding and transaction strategies to maximize their own profits. The market price and the quantity are concerned with the operation reserve as well as the bidding system and demand curves in an electricity market. This paper presents a market model combined by an energy market and an operating reserve market. The competition of the generation producers in the combined market is formulated as a gaming of selecting bid parameters such as intersections and slopes in bid functions. The Nash Equilibrium(NE) is analyzed by using a hi-level optimization; maximization of Social Welfare(SW) and maximization of the producers' profits.

• Journal of Power Electronics
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• v.12 no.5
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• pp.689-698
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• 2012

This paper investigates the effects of applying different input current waveshapes on the performance of a continuous-conduction-mode (CCM) power-factor-correction (PFC) boost pre-regulator. It is found that the output voltage ripple of the pre-regulator can be reduced if the input current is modified to include controlled amount of higher order harmonics. This finding allows us to balance the performance of output regulation and the harmonic current emission when coming to the design of the pre-regulator. An experimental PFC boost pre-regulator prototype is constructed to verify the analysis and show the benefit of the pre-regulator operating with input current containing higher order harmonics.