• 한국철도학회논문집
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• 제12권6호
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• pp.878-886
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• 2009

본 논문에서는 열차 운전시 최적의 에너지 효율을 얻기 위해서 GA(Genetic Algorithm)를 이용하여 열차 속도 프로파일을 생성하는 최적 알고리즘을 제시하고 시뮬레이션을 통해 유효성을 보였다. 역간의 열차 운전 모드를 최대 역행, 타행, 최대 제동으로 간략화 시키고 타행지점을 조절하여 열차 운전시 소비되는 에너지를 최소화 시키는 방식을 기본으로 하여, 정해진 거리의 두 역간을 정해진 운전시간 내에 도달하기 위하여 목표 운전시간을 이용하여 적합도(Fitness) 함수를 설정한 후, GA 알고리즘을 적용하여 역간 거리와 목표 운전시간의 두 제한요소를 모두 만족시키는 타행 지점들을 결정하였다. 시뮬레이션 결과 두 제한 요소들을 만족하는 타행 지점이 여러 개가 존재함을 확인하였고, 각 타행지점들에 따른 소비 에너지를 도출하여 에너지 소비량이 가장 적은 타행지점을 선정하여 최종적인 열차속도 프로파일을 결정하였다. 시뮬레이션을 위해 Simulink를 이용하여 열차성능 시뮬레이션 블록들과 GA 블록들을 설계하였다.

• Steel and Composite Structures
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• 제51권2호
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• pp.173-183
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• 2024

This study investigates a new seismic retrofit system that utilizes rotational friction dampers and axial springs. The retrofit system involves a steel frame with rotational friction dampers (RFD) at beam-column joints and linear springs at the corners, providing energy dissipation and self-centering capabilities to existing structures. The axial spring acts as a self-centering mechanism that eliminates residual deformations, while the friction damper mitigates seismic damage. To evaluate the seismic performance of the proposed retrofit system, a series of cyclic loading tests were carried out on a steel beam-column subassembly equipped with the proposed devices. An analytical model was then developed to validate the experimental results. A performance point ratio (PPR) was presented to optimize the design parameters of the retrofit system, and a performance-based seismic design strategy was developed based on the PPR. The retrofit system's effectiveness and the presented performance-based design approach were evaluated through case study models, and the analysis results demonstrated that the developed retrofit system and the performance-based design procedure were effective in retrofitting structures for multi-level design objectives.

• 한국전자통신학회논문지
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• 제16권3호
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• pp.493-502
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• 2021

외부 환경변화에 적응하여 MPP를 추적할 수 있는 포복경 영양 번식(VPR; Vegetative Propagation by Runner) 최적화 알고리즘 기반 MPPT 알고리즘을 제시하였다. VPR 알고리즘은 영양기관을 기반으로 군집 이동 번식하는 식물 생태를 모방한 알고리즘으로 식물의 노화 및 부근(Rhizome)에 대한 주변탐색 절차를 수행하여 최적점 인근의 주변을 지속적으로 탐색할 수 있다. 따라서 VPR 기반 MPPT 알고리즘의 경우, MPPT 알고리즘이 수행되는 시점에 발생하는 외부 환경변화에 적응하여 최적점을 탐색할 수 있다. 본 논문에서는 다수의 모의실험을 통해 VPR 기반 MPPT 알고리즘의 성능을 분석하였다. 더불어 PSO(Particle Swarm Optimization) 기반 MPPT 알고리즘과 동일한 환경에서 성능 비교를 통해 성능의 우수성을 비교하였다.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.324-330
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• 2021

In recent years, polymer electrolyte membrane fuel cell (PEMFC) based cogeneration system has received more and more attention from energy researchers because beside electricity, the system also meets the residential thermal demand. However, the low-quality heat exited from PEMFC should be increased temperature before direct use or storage. This study proposes a method to utilize the heat exhausted from a 10 kW PEMFC by coupling a heat pump. Two different configuration using heat pump and a reference layout with heater are analyzed in term of thermal and total efficiency. The system coefficient of performance (COP) increases from 0.87 in layout with heaters to 1.26 and 1.29 in configuration with heat pump and cascade heat pump, respectively. Lastly, based on system performance result, another study in economics point of view is proposed.

• 신재생에너지
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• 제8권3호
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• pp.14-22
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• 2012

Performance of photovoltaic (PV) generator systems relies on its operating conditions. Maximum power extracted from PV generators depends strongly on solar irradiation, load impedance, and ambient temperature. A most maximum power point tracking (MPPT) algorithm is based on a perturb and observe method and an incremental conductance method. It is well known the latter is better in terms of dynamics and tracking characteristics under condition of rapidly changing solar irradiation. However, in case of digital implementation, the latter has some error for determining a maximum power point. This paper presents a PID based MPPT algorithm for such PV systems. We use neural network technique for determining PID parameters by online learning approach. And we construct a boost converter to regulate the output voltage from PV generator system. Computer simulation is carried out to evaluate the proposed MPPT method and we accomplish comparative study with a perturb and observe based MPPT method to prove its superiority.

• ETRI Journal
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• 제45권6호
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• pp.996-1006
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• 2023

Renewable energy is promoted massively to overcome problems that fossil fuel power plants generate. One popular renewable energy type that offers easy installation is a photovoltaic (PV) system. However, the energy harvested through a PV system is not optimal because influenced by exposure to solar irradiance in the PV module, which is constantly changing caused by weather. The maximum power point tracking (MPPT) technique was developed to maximize the energy potential harvested from the PV system. This paper presents the MPPT technique, which is operated on a new high-gain voltage DC/DC converter that has never been tested before for the MPPT technique in PV systems. Fuzzy logic (FL) was used to operate the MPPT technique on the converter. Conventional and adaptive perturb and observe (P&O) techniques based on variables step size were also used to operate the MPPT. The performance generated by the FL algorithm outperformed conventional and variable step-size P&O. It is evident that the oscillation caused by the FL algorithm is more petite than variables step-size and conventional P&O. Furthermore, FL's tracking speed algorithm for tracking MPP is twice as fast as conventional P&O.

• 토지주택연구
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• 제4권4호
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• pp.407-415
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• 2013

2002년에 친환경건축물인증제도가 시행된 이후 많은 인증 수행에도 불구하고 이 제도의 효과분석이나 개선방안 노력이 저조하다. 특히 인증제도에서 에너지성능은 에너지절약설계기준에 있는 에너지성능지표(EPI)로 평가되지만 지금까지 지표에 대한 현황분석이 미비하여 개선에 어려움이 있다. 본 연구에서는 친환경 공동주택 인증단지를 대상으로 에너지성능지표간의 상관관계를 살펴보고 에너지성능지표의 각 부문별 에너지 기본 배점에 따른 점수 현황을 분석하여 지표 개선을 도모하였다. 친환경 공동주택 인증단지의 EPI 평균득점은 약 74.68점, 최소 63.40점, 최대 90점으로 편차가 큰 것으로 나타났다. 또한 인증지표 중에서 최고의 배점으로 편성된 에너지소비량의 경우, 최대 12점 배점에서 평균 7.04점으로 평균 수준에 머물고 있었다. 향후 에너지소비량 인증지표에서 등급구간의 강화 또는 산출식의 조정 등의 지표 개선이 필요하였다.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1182-1187
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• 2014

This paper proposes an energy management strategy and adaptive control for superconducting magnetic energy storage (SMES) in a distribution power system with a grid-connected photovoltaic (PV) farm. Application of the SMES system can decrease the output power fluctuations of PV system effectively. Also, it can control the real and reactive powers corresponding to the scheduled reference values with adequate converter capacity, which are required at a steady-state operating point. Therefore, the adaptive control strategy for SMES plays a key role in improving the system stability when the PV generation causes uncertain variations due to weather conditions. The performance of proposed energy management strategy and control method for the SMES is then evaluated with several case studies based on the PSCAD/EMTDC$^{(R)}$ simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.1076-1089
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• 2012

Home automation networks are good environments for merging sensor networks and consumer electronics technologies. It is very important to reduce the energy consumption of each sensor node because sensor nodes operate with limited power based on a battery that cannot be easily replaced. One of the primary mechanisms for achieving low energy operation in energy-constrained wireless sensor networks is the duty-cycle operation, but this operation has several problems. For example, unnecessary energy consumption occurs during synchronization between transmission schedules and sleep schedules. In addition, a low duty-cycle usually causes more performance degradation, if the network becomes congested. Therefore, an appropriate control scheme is required to solve these problems. In this paper, we propose UDC (Unsynchronized Duty-cycle Control), which prevents energy waste caused by unnecessary preamble transmission and avoids congestion using duty-cycle adjustment. In addition, the scheme adjusts the starting point of the duty-cycle in order to reduce sleep delay. Our simulation results show that UDC improves the reliability and energy efficiency while reducing the end-to-end delay of the unsynchronized duty-cycled MAC (Media Access Control) protocol in sensor-based home automation networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1116-1132
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• 2010

In this paper, a new forward error correction (FEC) protocol is proposed for point-to-multipoint satellite links. Link-layer error control protocols in point-to-multipoint satellite links impose several problems such as unreliability and receiver-heterogeneity. To resolve the problem of heterogeneous error rates at different receivers, the proposed scheme exploits multiple multicast channels to which each receiver tunes. The more channels a receiver tunes to, the more powerful error correcting capability it achieves. Based on its own channel condition, each receiver tunes to as many channels as it needs, which prevents from receiving unwanted parities. Furthermore, each receiver saves the decoding time, processing overhead, and processing energy. Performance evaluation shows that the proposed scheme guarantees the target PER while saving energy. The proposed technique is highly adaptive to the channel variation with respect to the throughput efficiency, and provides scalable PER and throughput efficiency.