• 한국수자원학회논문집
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• 제32권5호
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• pp.525-535
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• 1999

유역내의 수력 에너지자원과 수자원의 효율적 관리를 위하여 통합혼합정수계획법(combined mixed integer proguamming)을 사용한 최적 발전기 운영계획 모형을 개발하였다. 통합혼합정수계획법 모형은 기왕에 개발된 혼합정수계획법 모형에서 발생할 수 있는 모순을 해결하기 위하여 개발되었다. 또한, 조건부 제약조건과 택일 제약조건들을 선형계획법 모형에서 사용 할 수 있도록 수정하는 기법을 제안하였다. 미국 콜로라도강 하부유역에 통합혼합정수계획법을 적용한 경우를, 최적화 모형을 사용하지 않은 경우 및 혼합정수계획법을 사용한 경우와 비교한 결과, 최적화 기법을 사용하지 않은 경우보다 유역효율이 0.67% 증가하였고, 혼합정수계획법을 사용한 경우보다 유역효율이 1.53% 감소하였다. 통합혼합정수게획모형의 효율이 감소한 이유는 혼합정수계획법모형보다 전력요구량과의 허용오차를 감소시켰기 때문인 것으로 판단된다.

• 전기학회논문지
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• 제68권4호
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• pp.513-522
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• 2019

We calculate the benefit of distributed combined heat power generators from avoiding a transmission expansion cost by building distributed generators near electricity demand centers. We determine a transmission expansion plan by solving a mixed integer linear problem, where we modify capacities of existing transmission lines and build new transmission lines. We calculate the benefit by comparing the sum of generation and transmission expansion costs with or without distributed generators through two simulation frames. In the first frame, for the current demand, we substitute existing distributed generators for non-distributed generators and measure an additional cost to balance the generation and demand. In the second frame, for increased future demand, we compare the cost to invest only in distributed generators to the cost to invest only in non-distributed generators. As a result, we show that the distributed generators have at least 5.8 won/kWh of the benefit from avoiding the transmission expansion cost.

• 전기학회논문지
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• 제62권11호
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• pp.1610-1616
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• 2013

Recently, district heating and cooling (DHC) systems based on combined cycle generation (CCG) providers are increasing in Korea. Since characteristics of combined heat and power (CHP) generators and heat demands of providers, heat trading between DHC providers based on the economic viewpoint is required; the heat trading has been doing. In this paper, a mathematical model for optimal operation based on heat trading between DHC providers is proposed. Especially, start-up characteristic of CCG is included. The operation model is established by mixed integer linear programming (MILP).

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2003년도 추계학술대회 및 정기총회
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• pp.81-84
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• 2003

The ability to determine the optimal frequencies and offsets for independent and unrestricted ordering cycles for multiple items can be very valuable for managing storage capacity constrained facilities in a supply chain. The complexity of this problem has resulted in researchers focusing on more tractable surrogate problems that are special cases of the base problem. Murthy et al. (European Journal of Operation Research 2003) developed insights leading to solution of the original problem and present a heuristic for offsetting independent and unrestricted ordering cycles for items to minimize their joint storage requirements. However, their study cannot find optimal solution due to the Greedy Heuristic solution procedure. In this paper, we present a complete procedure to find the optimal solution for the model with a integer programming optimization approach and genetic algorithm. Numerical examples are included to compare each model with that of Murthy et at. Research of this type may prove useful in solving the more general problem of selecting order policies to minimize combined holding, ordering, and storage costs.

• KIEE International Transactions on Power Engineering
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• 제5A권4호
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• pp.311-321
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• 2005

A competitive generating company (GENCO) could maximize its payoff by optimizing its generation assets. This paper considers the GENCO's arbitrage problem using price-based unit commitment (PBUC). The GENCO could consider arbitrage opportunities in purchases from qualifying facilities (QFs) as well as simultaneous trades with spots markets for energy, ancillary services, emission, and fuel. Given forecasted hourly market prices for each market, the GENCO's generating asset arbitrage problem is formulated as a mixed integer program (MIP) and solved by a branch-and-cut algorithm. A GENCO with 54 thermal and 12 combined-cycle units is considered for analyzing the proposed formulation. The proposed case studies illustrate the significance of simultaneous arbitrage by applying PBUC to multi-commodity markets.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권8호
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• pp.2626-2646
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• 2014

This study presents a power and Physical Resource Blocks (PRBs) joint allocation algorithm to coordinate uplink (UL) interference in the device-to-device (D2D) underlaying Long Term Evolution-Advanced (LTE-A) networks. The objective is to find a mechanism to mitigate the UL interference between the two subsystems and maximize the weighted sum throughput as well. This optimization problem is formulated as a mixed integer nonlinear programming (MINLP) which is further decomposed into PRBs assignment and transmission power allocation. Specifically, the scenario of applying imperfect channel state information (CSI) is also taken into account in our study. Analysis reveals that the proposed PRBs allocation strategy is energy efficient and it suppresses the interference not only suffered by the LTE-A system but also to the D2D users. In another side, a low-complexity technique is proposed to obtain the optimal power allocation which resides in one of at most three feasible power vectors. Simulations show that the optimal power allocation combined with the proposed PRBs assignment achieves a higher weighted sum throughput as compared to traditional algorithms even when imperfect CSI is utilized.

• 대한산업공학회지
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• 제40권2호
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• pp.184-194
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• 2014

Numerous studies have been studied to provide an efficient solution for the Nurse Rostering Problem (NRP), most of which have suffered from its complexity arising from incorporating nurse's work shift and ability. The test-bed data for the NRP is released for the public Competition in 2010. This study suggests a new mixed integer programming for Nurse Rostering Problem and develops a hybrid approach, where a hierarchical decomposition and the corresponding optimization are combined. The computation experiment is performed to show that the suggested algorithms may give a better solution in various instances, compared to the one appeared in the literature.

• 대한교통학회지
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• 제19권5호
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• pp.99-108
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• 2001

본 논문은 유류저장탱크의 최적입지를 선정하기 위한 GIS와 OR 통합적용기법을 제시하며, P-Median heuristic method와 MIP method가 모두 유류저장탱크의 최적입지 선정 문제에 적용될 수 있음을 실증하였다. 또한, 두 접근 방식에 의해 확인된 결과들은 동일하였다. P-Median heuristic method와 MIP method 를 풀이하는데 필요한 최단거리 매트릭스를 계산해내 기 위해 GIS기반 도로망과 해운네트워크를 구축·결합하였으며, 두 접근방법을 통해 우리나라의 최적 유류저장탱크의 입지를 선정한 결과 권역별로 군산항, 여수항, 부산항, 옥계항이 선정되었다. 위와 같이, 본 연구를 통해 CIS와 P-Median heuristic method, MIP method의 적용은 실증되었으며, 유사한 연구 또한 GIS와 OR의 통합적용을 통해 수행될 수 있을 것이다.

• 전기학회논문지
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• 제63권1호
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• pp.18-26
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• 2014

A microgrid can play a significant role for enlargement of renewable energy sources and emission reduction because it is a network of small, distributed electrical power generators operated as a collective unit. In this paper, an application of optimization method to economical operation of a microgrid is studied. The microgrid to be studied here is composed of distributed generation system(DGS), battery systems and loads. The distributed generation systems include combined heat and power(CHP) and small generators such as diesel generators and the renewable energy generators such as photovoltaic(PV) systems, wind power systems. Both of thermal loads and electrical loads are included here as loads. Also the emissions trading scheme to be applied in near future, the cost of unit start-up and the operational characteristics of battery systems are considered as well as the probabilistic characteristics of the renewable energy generation and load. A mathematical equation for optimal operation of this system is modeled based on the mixed integer programming. It is shown that this optimization methodology can be effectively used for economical operation of a microgrid by the case studies.

• 정보처리학회논문지D
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• 제18D권5호
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• pp.371-384
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• 2011

본 논문은 운송비용과 탄소배출비용을 고려한 최적 운송수단 선정에 대한 물류의사결정 시스템을 설계하고자 한다. 기존 연구는 운송비용과 운송모드별 용량을 고려하여 최적의 운송수단을 선정하였으나, 온실가스 배출규제에 대응하기 위해 운송비용과 용량 뿐만 아니라 탄소배출비용을 통합적으로 고려하여 물류체계를 설계할 필요성이 높아지고 있다. 따라서 본 논문에서는 탄소배출을 고려한 우리나라의 복합운송에 대한 운송수단 선택과 비용과 CO2배출의 Trade-off관계에 대한 접점을 찾아 분석하고 향후 나아갈 방안에 대해 제시하고자 한다. 탄소배출비용을 고려한 최적 운송수단 의사결정 문제는 혼합정수계획 모형으로 모델링되었으며, 운송비용과 탄소배출비용 사이의 관계를 분석하기 위하여 서울-부산 간 컨테이너 운송에 있어서의 다양한 시나리오를 도출하였다. 각각의 시나리오는 개발된 의사결정 시스템을 통하여 분석되었으며, 분석결과 단위 이동 거리당 탄소배출량이 낮은 것으로 알려져 있는 해상운송과 같은 대량운송 수단이 경우에 따라 더 많은 탄소를 배출하는 것으로 나타났다. 대량운송 수단의 경우 항만이나 철도역까지의 트럭운송에서의 우회가 증가된 탄소 배출의 주요 원인이었다. 제안된 물류의사결정 시스템은 녹색물류 및 그린SCM에서의 탄소배출비용과 물류비용사이의 관계를 이해하는데 역할을 할 것으로 기대된다.