• Journal of Korea Water Resources Association
• /
• v.54 no.6
• /
• pp.443-452
• /
• 2021

The authors obtained the discrete hedging rule for a reservoir's water supply operation by applying mixed-integer programming to save more water by earlier rationing of water supply for a drought period. The 'water supply adjustment guide' is the current operational method applied to the multipurpose reservoirs, and it was derived by a simulation method. Applying the two rules to the Hapcheon multipurpose dam's reservoir simulations with the inflow record from 2003 to 2018, the water supply deficit occurred for the long drought from 2015 to 2018. Especially, the no water supply or intermittent water supply persisted for the second half of 2017. The water supply adjustment guide had the 'normal water supply recovery threshold on storage,' which resulted in the water supply being unavailable in July 2017; then, the water supply suspension occurred until January 2018, when the reservoir storage was greater than the normal water supply recovery threshold. Despite the storage increasing due to the inflow of water into the reservoir, the suspension occurrence needs to be improved in practice. The current water supply adjustment guide and the discrete hedging rule for a reservoir's water supply operation are useful and realistic as the reservoir operation guide, which shows the concept of reducing water supply during the drought phase as scientific figures. However, to improve the reservoir simulation results, which do not provide any or intermittent water for several months, it is necessary to increase the current water supply reduction for drought phases.

• Journal of the Korean Society for Railway
• /
• v.14 no.2
• /
• pp.167-173
• /
• 2011

This paper considers the problem of revising train departure time to reduce electric power consumption of mass rapid transit (MRT) railways. The motion of a train running between stations is divided into three phases: traction, coasting, and deceleration phases. The traction phase requires high electric power to operate MRT railways. In the coasting phase, the train moves stably by consuming little or no power. The deceleration phase is a braking mode and produces some electric power called regenerated brake power owing to inertia force for the train generated In the traction and coasting phases. The regenerative energy can be used by other accelerating trains within a specific range from the train and thereby the power consumptions of train can be reduced. We developed a mixed integer programming model to solve the problem. To validate the suggested model, a computational experiment was conducted using real data from Korea Metropolitan Subway.

• Industrial Engineering and Management Systems
• /
• v.12 no.4
• /
• pp.336-350
• /
• 2013

This paper proposes a mathematical modeling-based approach for assessing disaster effects and selecting suitable mitigation alternatives to provide humanitarian relief (HR) supplies, shelter, rescue services, and long-term services after a disaster event. Mitigation steps, such as arrangement of shelter and providing HR items (food, water, medicine, etc.) are the immediate requirements after a disaster. Since governments and non-governmental organizations (NGOs) providing humanitarian aid need to know the requirements of relief supplies and resources for collecting relief supplies, organizing and initiating mitigation steps, a quick assessment of the requirements is the precondition for effective disaster management. Based on satellite images from weather forecasting channels, an area/dimension of the disaster-affected zones and the extent of the overall damage may often be obtained. The proposed approach then estimates the requirements for HR supplies, supporting resources, and rescue services using the census and other government data. It then determines reliable transportation routes, optimum collection and distribution centers, alternatives for resource support, rescue services, and long-term help needed for the disaster-affected zones. A numerical example illustrates the applicability of the model in disaster mitigation planning.

• Journal of the Korea Society for Simulation
• /
• v.22 no.4
• /
• pp.149-156
• /
• 2013

In this research, we dealt with an optimization problem which aims to minimize total cost of resources usage and network routing in a smart node environment. Toward this, we briefly introduced technology trends in smart nodes, methods in resource optimization fields, economic effects of smart network and content delivery (or distribution) network (CDN). Moreover, based on CDN we proposed and implemented a mathematical (mixed integer) programming model to combine replica placement and requests distribution problem (RPRDP) and routing problem. Computational result of an example on RPRDP+Routing problem is also provided.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.945-949
• /
• 2004

These days there are so many scheduling systems or softwares. But only few scheduling systems have succeeded in the market. In spite of powerful engine and functions, those systems have difficulties to be applied in real processes. In real processes, there are various constraints caused by physical or systematical environments of plants. Those constraints are too many to be handled in the system. This problem makes it difficult for the system to represent the details of processes. In order to resolve this problem, we have developed a specialized scheduling system for a target process. The system could be developed by the experts for target process and researchers for scheduling. In this study, a scheduling system for PVC process has been developed as an MILP (Mixed integer linear programming) model and coded in $Fortran^{TM}$. The scheduling system has been applied to two processes, which have different characteristics. Simulation results indicate that the profit of the target process can be increased by about 5% by implementing the scheduling system.

• Journal of Information Technology Services
• /
• v.10 no.3
• /
• pp.49-59
• /
• 2011

A ship scheduling model is presented for the raw material transportation problem with yard storage constraints in a steel mill. The problem is formulated as 0, 1 mixed integer programming considering such constraints as loading port conditions, ship size and hold capacity, unloading conditions, and yard storage space. In addition, inventory related constraints including safety stock are taken into consideration to support the continuous operations of steel making process. The proposed model has been implemented and applied successfully to a real world problem, and its results show the improvement of performance compared to the traditional method. For example, the arrival dates of ships are determined satisfying the constraints. The total inventory level is minimized at the stock yard as a result. Also, the safety inventory level is always kept at the planning stage, and the standard deviation of total inventory level is reduced significantly. Further research is expected to develop efficient heuristics to have a better response time for even larger scale problems.

• Journal of Korean Society of Transportation
• /
• v.17 no.2
• /
• pp.127-135
• /
• 1999

Most existing progression bandwidth models maximize the single or multi weighted sum of bandwidths in the both directions to improve traffic mobility on an arterial, but they cannot be applied to general networks. Even though a few models formulating a looped network problem cannot be applied to networks have not loops. Also they have some defects in optimizing phase sequences. Therefore, the objective of this study is to develope a mathematical formulation of the synchronization problem for a general traffic network. The goal is achieved successfully by introducing the signal phasing for each movement and expanding the mixed integer linear programming of MAXBAND. The experiments indicate that the proposed model can formulate the general traffic network problem mere efficiently than any other model. In conclusion, this model may optimize signal time to smooth progression in the general networks.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.284-288
• /
• 2005

본 연구에서는 낙동강수계 일별 운영 계획 수립을 위한 저수지군 최적 연계운영 모형(CoMOM, Coordinated Multiple Reservoir Operating Model)을 개발하였다. 이를 위하여 동적 네트워크 흐름 모형을 기반으로 한 다중목적 혼합 정수 목표계획 모형 (MOMIGP, Multiple Objective Mixed Integer Goal-Programming)을 수립하였다. 이 모형은 월말 목표 수위 및 운영 제약 등을 목표 계획법으로 구성하였으며, 일별 운영의 특성을 고려하여 하도추적의 효과를 반영하였고, 선형화된 발전함수를 이용하여 발전량을 최대화 하도록 한 후 정확한 발전량을 사후에 산정하였다. 이와 같이 수립된 수학 모형을 GUI를 비롯한 프로그램(CoMOM)으로 개발하여 사용자가 편리하게 수행 할 수 있도록 하였다. 이 프로그램은 의사결정자의 운영 목표와 의도를 효과적으로 반영할 수 있도록 대화형 목표 계획법을 구현하였으며, 상충되는 여러 목적에 대하여 가능한 파래토(Pareto) 최적해를 제시하고 의사결정자가 가장 선호하는 해를 선택하도록 대화형 다중목적 계획법 CBITP(Convex hull of individual maxima Based Interactive Tchebycheff Procedure)를 활용하여 구현하였다. 한편 객체지항적 프로그램 기법을 활용하여 수계 내의 노드(저수지, 수요지, 발전소 등)를 추가 하거나 삭제 할 수 있도록 하여, 다른 수계로의 확장이 용이하도록 개발하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.89-93
• /
• 2009

홍수기에 집중되는 하천유출량을 갈수기에 적절히 활용하기 위한 대표적인 시설이 댐이다. 제한된 용수공급량을 적절히 분배해 용수수요량을 만족시키면서 미래 갈수기시 용수공급을 위한 댐 저류량을 조절하는 것이 댐 운영의 중요한 목적 중 하나이다. 본 연구에서는 댐 저류량에 따라 댐 계획방류량을 일정비율 줄여주는 Hedging Rule을 5단계로 적용하여 댐의 상시만수위 저류량에 대한 실제 저류량의 편차 절대치 합, 수요에 대한 용수공급 부족량의 합, 그리고 하천유지유량에 대한 하천유량 부족량의 합을 목적함수로 하여 혼합정수 선형계획법(MILP, Mixed Integer Linear Programming)으로 식을 구성하였다. 한강수계의 다목적댐인 충주, 횡성, 소양강 댐과 용수전용댐인 광동 댐, 그리고 발전용 댐이지만 비교적 큰 저류용량을 가진 화천 댐을 댐 연계 운영 대상으로 하여 수자원장기종합계획의 2003년 유출량 및 수요량 자료와 댐운영실무편람의 댐 계획방류량 자료를 10일 단위로 입력하여 GAMS/CPLEX를 이용해 최적화하였다. 그 결과 생공용수 수요량 99.99%, 농업용수 수요량 99.91%, 그리고 하천유지용수 수요량 99.24%를 충족시키면서, 댐 저류율이 66.54%에서 86.39%로 증가하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.292-296
• /
• 2009

우리나라의 용수공급체계는 주로 여름에 집중된 강우를 댐이나 저수지에 저류하였다가 연중고르게 사용자들에게 공급하는 방법을 취하고 있다. 이때 도시지역의 생활용수는 갈수기에도 가장먼저 공급되어져야하는 우선순위를 가지는 반면, 농업용수는 가장 우선적으로 그 사용을 제한받는다. 하지만, 도시화로 인해 도시의 하수처리장 배출수량은 지속적으로 증가하고 있으며, 그 처리수의 대부분은 하천으로 방류되어 유실되고 있다. 방류수 수질기준에 맞추어 방류되는 처리수는 대량방류로 인해 자주 하천에 수질문제를 야기하기도 한다. 그러나 실제로 하수처리장의 처리수는 갈수기에 매우 유용하게 사용될 수 있는 수원 중 하나이다. 그러므로 그 처리수의 재이용에 관한 연구를 적절히 수행한다면, 갈수기에도 농업용수사용의 제한을 최소화할 수 있을 것이다. 그러므로 본 연구에서는 처리수 재이용 모형을 혼합정수계획법으로 개발하고, 하수처리장 처리수의 농업용수나 공공용수로의 사용을 제안하였다. 개발된 처리수 재이용 모형에서는 하천으로 방류되던 처리수를 농업용수나 공공용수로 재사용하는 시스템을 구축한다는 가정 하에, 그 공사비를 최소화하는 것을 목적으로 하였다. 또한 관말의 최소유지압력 등 수리학적인 제약조건을 만족시키도록 설계하였으며, 이 때문에 야기되는 비선형성을 선형화하여 계산시간이 짧은 동시에 전역해에 가까운 해를 찾을 수 있도록 하였다. 개발된 모형은 가상의 처리수 재이용 모형에 적용되어 시스템의 설계자에게 갈수기 용수공급의 최적 대안을 제시해 줄 수 있는 가능성을 보였다.