• 한국산업정보학회논문지
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• 제26권1호
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• pp.55-65
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• 2021

본 연구에서는 폐쇄루프공급망 (Closed-loop supply chain: CLSC) 모델에서 역물류 (Reverse logistics: RL) 활동을 강화하기 위한 방법론을 개발한다. 이를 위해 RL 활동 중에서 주로 고려되는 설비 중의 하나인 회복센터(Recovery center: RC)의 활동을 강화한다. RC에서의 강화된 활동에 따라 고객으로부터 회수되는 사용 후 제품은 검사 및 회복과정을 거쳐 전방향물류 (Forward logistics: FL)에서 부품 혹은 제품으로 재사용된다. 강화된 RC 활동을 가진 CLSC 모델의 운영과정을 효율적으로 표현하기 위한 수리모델이 제시되며. 혼합유전알고리즘 (Hybrid genetic algorithm: HGA) 접근법을 이용해 제안된 수리모델이 이행된다. 수치실험에서는 두 개의 상이한 형태의 CLSC 모델이 제시되며, 본 연구에서 제안된 HGA 접근법과 기존의 연구에서 제안된 몇몇 접근법들의 수행도가 비교분석되었다. 비교분석결과 HGA가 기존의 접근법들 보다 더 우수한 수행도를 보여주었다. 또한 RC 활동의 검사 및 회복과정을 거친 부품 및 제품의 비율을 다양하게 조절함으로서 강화된 RC 활동을 가진 CLSC 모델의 유용성을 증명했다.

• 디지털융복합연구
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• 제20권5호
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• pp.211-220
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• 2022

본 연구는 폐쇄루프 공급망을 최적화하기 위한 녹색 폐쇄루프 공급망 네트워크(GCSN)를 제안한다. GCSN은 물류 유통과정에 투입되는 익스프레스 박스의 재활용에 중점을 두고 연구하였다. 이를 통해 물류공급망 작업의 표준화와 전자상거래 업체의 증가에 따른 익스프레스 박스의 사용의 가속화와 전자상거래 업계의 익스프레스 상자의 재활용을 통한 자원 낭비를 최소화하는 녹색공급망을 추진한다. GCSN은 유통흐름과 자원의 투입요소는 수학식으로 표현하며 LINGO를 사용하여 구현된다. 녹생 즉, 환경 보호의 관점에서 전자상거래 산업의 지속가능한 발전을 견인하는 유통의 과정이다. 또한 자원 부족에 따른 원자재 가격 상승에 대응하고 전자상거래 업체들의 친환경적으로 익스프레스 상자를 투입하는 전략의 필요성을 부각시켰다. 이와 같은 이유로 본 연구는 전자상거래 업체에서 사용하는 재활용이 가능한 익스프레스상자를 연구대상으로 하며, 공급망 네트워크에서 시설 위치와 할당문제도 통합적으로 고찰한다. 마지막으로 본 연구의 결론과 시사점을 도출하였다.

• 한국산업정보학회논문지
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• 제29권1호
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• pp.49-62
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• 2024

본 연구는 국내 모바일폰 산업을 위한 지속가능한 폐쇄루프 공급망 (Sustainable closed-loop supply chain: SCLSC) 네트워크 모델을 제안한다. 제안된 SCLSC 네트워크 모델의 지속 가능성을 위해 경제적, 환경적, 사회적 요인들이 각각 고려된다. 이들 세 가지 요인들은 SCLSC 네트워크 모델의 각 단계에서 고려되는 설비의 구축 및 운영으로부터 발생하는 총비용 최소화, CO₂ 방출 총량 최소화, 사회적 영향력 최대화를 목표로 한다. 이러한 목표들은 SCLSC 네트워크의 모델링 단계에서 각각 개별적인 목적함수로 고려되어야 하기 때문에 SCLSC 네트워크 모델은 다목적 최적화 문제로 간주할 수 있다. SCLSC 네트워크 모델은 수리모델을 사용하여 표현되며, 혼합형 메타휴리스틱 접근법을 수리모델에 적용하여 그 해를 구한다. 수치실험에서는 제안된 혼합형 메타휴리스틱 접근법의 수행도가 기존의 메타휴리스틱 접근법들의 수행도와 비교된다. 실험결과는 본 연구에서 제안된 혼합형 메타휴리스틱 접근법이 기존의 메타휴리스틱 접근법들과 비교하여 더 뛰어난 수행도를 보여주는 것을 알 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.15-17
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• 1996

In this paper, a modified microstep drive of PM step motor is presented. The open-loop drive of a step motor is attractive and widely accepted in applications of speed and position controls. However, the performance of the step motor is limited under the open-loop drive. The closed-loop control is advantages over the open-loop control not only in that step failure never occurs but that the motion is much quicker and smoother. However, a high resolution sensor is needed for detecting position and speed. The modified microstep drive is constructed as a microstep drive with speed feedback. The advantages of the proposed method is that the controller can be designed by a low resolution sensor and is simpler than other closed-loop controller. A concept of vector control is used for verifying the proposed scheme. Simulations show the performance of the proposed method and a comparison with a classic drive method.

• 한국태양에너지학회 논문집
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• 제22권2호
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• pp.39-47
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• 2002

The thermosyphon SDHWS and the loop type thermosyphon systems are widely used for domestic hot water system. The loop type thermosyphon is a circulation device for transferring the heat produced at the evaporator to the condenser area in the loop. In this study, the operating characteristics of various working fluids being used have been identified. The working fluids employed in the study were ethanol. water, and a binary mixture of ethanol and water. The volume of working fluid used in this study were 30%, 40%, 50%, 60% and 70% of evaporator volume. It is observed that, in the thermosyphon with low volume of working fluid, such as 30% or 40%, the fluid was dried out. The flow pattern and mechanism of the heat transfer were identified through this study. Flow patterns of the binary mixture working fluid were also investigated, and the patterns were recorded in the camera. The system parameters were calculated using the thermal performance data. Modelling of the system was carried out using PSTAR method and TRNSYS program.

• 설비공학논문집
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• 제29권3호
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• pp.119-126
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• 2017

Recently, ground source heat pump systems are being used in buildings for cooling and heating to reduce greenhouse gas and save energy. However, ground source heat pump systems mainly use the vertical closed-loop geothermal system design rather than the open-loop geothermal system design. This is due to a lack of knowledge and few research feasibility studies. In this research, a dynamic thermal analysis numerical simulation based on a standard house model was conducted for an open-loop geothermal system. Based on heating load analysis results, the life cycle costs of a standard house using an open two-well geothermal system were analyzed and compared with a vertical closed-loop geothermal system, and a diesel boiler. As a result, it was found that using an open two-well geothermal system shows economic return on investment after three years.

• 전기학회논문지
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• 제65권3호
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• pp.397-403
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• 2016

Generally, an electrical distribution configuration is a radial system with one-way current in a distribution management system (DMS). All feeders in a DMS have tie-switches to make radial system. Sometimes, DMS should change a tie-switch for operation. In that case, the tie-switch has to be closed first; then a switch is opened as another tie-switch in order to prevent blackout for customers. At the moment when the tie-switch is closed, distribution system is operated in a loop state, not radial. Before the loop operation, DMS operator has to check any expected events for stable distribution system operation; and the most important event is a mis-operation of a protection relay. In addition, DMS operator should check voltage profile violation but a calculation method of section voltages had not been used. Thus, this paper proposes a calculation method of section voltages at a loop operation in a DMS. The proposed calculation algorithm is verified by Matlap Simulink.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.117-119
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• 2004

An optimal flight motion simulator path generation method is proposed for hardware in the loop simulation of high maneuverable missile. The proposed method consists of open loop and closed loop path calculation algorithm based on the energy optimal control strategies. The optimal angle command is able to protect the simulator from high acceleration shock at initial control phase.

• 대한건축학회논문집:구조계
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• 제34권5호
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• pp.43-50
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• 2018

The temperature of underground water generally remains constant regardless of the season. therefore, it is possible to get plenty of energy if we use characteristics of underground water for both cooling and heating. This study evaluates efficiency of real size coaxial and U-tube type complex geothermal system which is combined with underground water well. This study also evaluates relative efficiency/adaptability through comparison with existing geothermal systems(vertical closed loop system, open loop system(SCW)). The heat exchange capacity of complex geothermal system according to temperature difference between circulating water and underground water shows very high significance by increasing proportionally. The temperature change of underground water according to injection energy, shows very high linear growth aspect as injection thermal volume heightens. As a result of evaluation of heat exchange volume between complex geothermal system and comparative geothermal system, coaxial type has 26.1 times greater efficiency than comparative vertical closed type and 2.8 times greater efficiency than SCW type. U-tube type has 26.5 tims greater efficiency than comparative vertical closed type and 2.8 times greater than SCW type as well. This means complex geothermal system has extremely outstanding performance.

• International Journal of Control, Automation, and Systems
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• 제4권6호
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• pp.689-696
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• 2006

This paper presents a new algorithm for the closed-loop $H_{\infty}$ composite control of weakly coupled bilinear systems with time-varying parameter uncertainties and exogenous disturbance using the successive Galerkin approximation(SGA). By using weak coupling theory, the robust $H_{\infty}$ control can be obtained from two reduced-order robust $H_{\infty}$ control problems in parallel. The $H_{\infty}$ control theory guarantees robust closed-loop performance but the resulting problem is difficult to solve for uncertain bilinear systems. In order to overcome the difficulties inherent in the $H_{\infty}$ control problem, two $H_{\infty}$ control laws are constructed in terms of the approximated solution to two independent Hamilton-Jacobi-Isaac equations using the SGA method. One of the purposes of this paper is to design a closed-loop parallel robust $H_{\infty}$ control law for the weakly coupled bilinear systems with parameter uncertainties using the SGA method. The other is to reduce the computational complexity when the SGA method is applied to the high order systems.