• 전기학회논문지
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• 제67권12호
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• pp.1587-1594
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• 2018

In south korea, the government make a plan to generate the 20% of the total electrical power as renewable source like wind generation and solar generation. This plan will accelerate the increase of fault current with power industry's growth. As the increase of fault current, the superconducting fault current limiter (SFCL) has been studied. In case that the SFCL is applied in power system, it can cause the overcurrent relay (OCR)'s trip delay because of the reduced fault current. In this paper, the overcurrent relay with voltage component was suggested to improve the OCR's trip delay caused by the SFCL and compensational constant was introduced to have the trip time similar to the trip time of case without the SFCL. For conforming the effect of the suggested OCR with voltage component, the PSCAD/EMTDC simulation modeling and analysis were conducted. Through the simulation, it was conformed that the trip delay could be improved by using the suggested OCR and compensational constant.

• 전기학회논문지
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• 제65권2호
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• pp.269-278
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• 2016

In order to maintain customer voltages within allowable limit($220{\pm}13V$) as much as possible, tap operation strategy of SVR(Step Voltage Regulator) installed in distribution system is very important, considering the scheduled delay time(30 sec) of SVR. However, the compensation of BESS(Battery Energy Storage System) during the delay time of SVR is being required because the customer voltages in distribution system interconnected with PV(Photovoltaic) system have a difficultly to be kept within allowable limit. Therefore, this paper presents the optimal voltage stabilization method in distribution system by using coordination operation algorithm between BESS and SVR. It is confirmed that customer voltage in distribution system can be maintained within allowable limit($220{\pm}13V$).

• 한국유통학회지:유통연구
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• 제16권4호
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• pp.29-64
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• 2011

상품의 이용가능성은 소비자 욕구를 충족시킬 수 있는 중요한 점포 능력 중의 하나이다. 그러나 구매하고자 하는 상품이 없는 품절(stockouts)상황이 발생했을때 소비자는 구매의사 결정의 어려움에 직면하고 이러한 어려움은 소비자의 부정적인 반응, 예컨대 점포에 대한 불만족을 야기한다. 본 연구에서는 상품의 이용가능성 상설, 즉 품절상황에서의 소비자 대체선택행동을 이끌어 내는 결정요인들을 파악하여, 이러한 변수들이 품절에 대한 소비자반응과 행동에 어떠한 영향을 미치는가를 규명하고자 한다. 세부적으로 본 연구에서는 기존 연구들과 달리 구매환경의 상황적인 특성(예: 구매 긴급성, 당황정도), 점포 특성(예: 상품구색, 매장편의성), 소비자 특성(예: 브랜드애호도, 점포애호도) 등에 초점을 맞추어 이러한 요인들이 품절시 소비자반응(상품대체, 구매연기, 점포전환 등의 대체선택행동)에 미치는 영향을 실증적으로 밝히는 것을 목적으로 하였다. 특히 본 연구에서는 선행연구에 비해 상품구색, 전반적인 점포 가격 이미지 등의 점포특성 변수들을 추가적으로 고려하여 분석하였다. 이러한 연구목적을 달성하기 위하여 대형할인마트, 슈퍼마켓 등의 다양한 소매업태에서 품절상황을 경험하고 나오는 353명의 소비자들로부터 자료를 수집하여 다항로짓분석(multinomial logit analysis)을 이용하여 연구모형과 연구가설을 검증하였다. 소비자 선택행동에 대한 MNL 모델 추정결과 품절상황에서 상품대체, 구매연기, 점포전환 행동에 대해 구매의 긴급성, 당황 정도, 구매량, 사전 계획구매, 상품구색, 전반적 점포가격 이미지, 브랜드애호도, 점포애호도 요인들이 소비자 선택행동에 유의한 영향을 미치는 것으로 나타났다. 구체적으로 살펴보면, 품절상황시 소비자의 점포 내 상품대체행동을 이끄는 결정요인으로 구매의 긴급성, 당황정도, 구매량, 사전 계획구매, 상품구색의 다양성, 저렴한 점포가격이미지, 브랜드애호도, 점포애호도 등이 유의하였으며, 구매연기를 유도하는 결정요인으로 구매의 긴급성, 구매량, 브랜드애호도 등으로 판명되었다. 품절시 소비자가 다른 점포로 전환하게 하는 요인은 구매의 긴급성, 구매량, 사전 계획구매, 상품구색의 다양성, 저렴한 점포가격이미지, 브랜드애호도, 점포애호도 등으로 파악되었다. 마지막으로 품절시 점포 편의성과 판매원 서비스 요인들은 소비자 대체 행동에 유의한 영향을 주지 못하였다.

• Journal of applied mathematics & informatics
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• 제22권1_2호
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• pp.453-460
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• 2006

A discrete-time priority queueing system with place reservation discipline is studied, in which two different types of packets arrive according to batch geometric streams. It is assumed that there is a reserved place in the queue. Whenever a high-priority packet enters the queue, it will seize the reserved place and make a new reservation at the end of the queue. Low-priority arrivals take place at the end of the queue in the usual way. Using the probability generating function method, the joint distribution of system state and the delay distribution for each type are obtained.

• 한국통신학회논문지
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• 제41권10호
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• pp.1240-1243
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• 2016

In this paper, we analyze the queueing performance of cumulative distribution function (CDF)-based opportunistic scheduling over Nakagami-m Markov fading channels. We derive the formula for the average queueing delay and the queue length distribution by constructing a two-dimensional Markov chain. Using our formula, we investigate the queueing performance for various fading parameters.

• 전자공학회논문지
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• 제51권7호
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• pp.71-81
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• 2014

본 논문에서는 삼차원 소자 시뮬레이터(Sentaurus)를 이용하여 tri-gate FinFET의 fin과 소스/드레인 구조의 변화에 따른 소자의 성능을 분석하였다. Fin의 구조가 사각형 구조에서 삼각형 구조로 변함에 따라, fin 단면의 전위 분포의 차이로 문턱 전압이 늘어나고, off-current가 72.23% 감소하고 gate 커패시턴스는 16.01% 감소하였다. 소스/드레인 epitaxy(epi) 구조 변화에 따른 성능을 분석하기 위해, epi를 fin 위에 성장시킨 경우(grown-on-fin)와 fin을 etch 시키고 성장시킨 경우(etched-fin)의 소자 성능을 비교했다. Fin과 소스/드레인 구조의 변화가 회로에 미치는 영향을 살펴보기 위해 Sentaurus의 mixed-mode 시뮬레이션 기능을 사용하여 3단 ring oscillator를 구현하여 시뮬레이션 하였고, energy-delay product를 계산하여 비교하였다. 삼각형 fin에 etched 소스/드레인 epi 구조의 소자가 가장 작은 ring oscillator delay와 energy-delay product을 보였다.

• Journal of Information Processing Systems
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• 제17권3호
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• pp.489-504
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• 2021

By distributing computing tasks among devices at the edge of networks, edge computing uses virtualization, distributed computing and parallel computing technologies to enable users dynamically obtain computing power, storage space and other services as needed. Applying edge computing architectures to Internet of Vehicles can effectively alleviate the contradiction among the large amount of computing, low delayed vehicle applications, and the limited and uneven resource distribution of vehicles. In this paper, a predictive offloading strategy based on the MEC load state is proposed, which not only considers reducing the delay of calculation results by the RSU multi-hop backhaul, but also reduces the queuing time of tasks at MEC servers. Firstly, the delay factor and the energy consumption factor are introduced according to the characteristics of tasks, and the cost of local execution and offloading to MEC servers for execution are defined. Then, from the perspective of vehicles, the delay preference factor and the energy consumption preference factor are introduced to define the cost of executing a computing task for another computing task. Furthermore, a mathematical optimization model for minimizing the power overhead is constructed with the constraints of time delay and power consumption. Additionally, the simulated annealing algorithm is utilized to solve the optimization model. The simulation results show that this strategy can effectively reduce the system power consumption by shortening the task execution delay. Finally, we can choose whether to offload computing tasks to MEC server for execution according to the size of two costs. This strategy not only meets the requirements of time delay and energy consumption, but also ensures the lowest cost.

• 산업경영시스템학회지
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• 제17권31호
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• pp.59-72
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• 1994

This paper deals with ordering policies of consumable goods which have large demand rates in a multi-level distribution system. The system we are concerned consists of one Central Distribution Center(CDC) and N non-identical Regional Distribution Centers(RDCs) which have different demand rates, minimum fillrates, leadtimes, etc. The customer demand on the RDC is stationary poisson and the RDCs demand on the CDC is superposition of Q-stage Erlang distributions. We approximate the RDCs and CDC demand distribution to nomal in order to enhance the efficiency of algorithm. The relevant costs include a fixed ordering cost and inventory holding cost, and backorder cost. The objective is to find a continuous-review ordering policy that minimizes the expected average costs under constraints of minimum fill rates of RDCs and maximum allowable mean delay of CDC. We developed an algorithm for determining the optimal ordering policies of the CDC and the RDCs. We verified and compared the performance of the algorithm through the simulation using the algorithm result as the input parameters.

• 전기학회논문지
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• 제58권9호
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• pp.1681-1688
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• 2009

This paper proposes a new fault restoration method which adopts the recloser as top agent to release the problems of the data concentration and fault processing delay of the existing DAS(distribution Automation System) under the ubiquitous distribution system. In proposed method, top agent collects the data based on the multi-casting communication with the tie switches of the interconnection point, and then selects a closed switch(tie switch) to transfer the sound outage load to other feeders based on the heuristic search strategy step by step until the load transfer work is finished. Here, a new heuristic rule is developed which can guarantee the relational load balancing and line loss from the collected voltage data. Finally, the several faults are simulated for typical multi-section and multi-interconnection distribution system to prove the effectiveness of the proposed strategy, in particular, for each simulation cases, the load balancing index and line loss index of the obtained solution from the proposed method is compared with those of all of feasible solutions.

• ETRI Journal
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• 제41권3호
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• pp.348-357
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• 2019

Fog radio access network (F-RAN) architectures provide markedly improved performance compared to conventional approaches. In this paper, an efficient genetic algorithm-based content distribution scheme is proposed that improves the throughput and reduces the transmission delay of a F-RAN. First, an F-RAN system model is presented that includes a certain number of randomly distributed fog access points (F-APs) that cache popular content from cloud and other sources. Second, the problem of efficient content distribution in F-RANs is described. Third, the details of the proposed optimal genetic algorithm-based content distribution scheme are presented. Finally, simulation results are presented that show the performance of the proposed algorithm rapidly approaches the optimal throughput. When compared with the performance of existing random and exhaustive algorithms, that of the proposed method is demonstrably superior.