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다목적 최적화 기법을 이용한 신재생에너지 기반 자립 에너지공급 시스템 설계 및 평가
이도현 ( Dohyun Lee ),한슬기 ( Seulki Han ),김지용 ( Jiyong Kim ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.3
본 연구에서는 다목적 최적화 기법을 이용하여 다양한 신재생에너지 자원 기반 통합 에너지 공급 시스템을 설계 및 평가 한다. 본 연구에서는 에너지 공급 시스템의 주요 구성요소로써 태양광 모듈, 풍력터빈 및 화석연료 기반 발전장치 등 에너지 생산 기술을 비롯하여 배터리와 인버터 등의 전력 에너지 저장 및 변환 장치 등도 포함한다. 특히, 6개의 한국 대표 지역을 선별하여 각 지역의 에너지 요구량 및 실제 신재생 에너지 자원 데이터를 기반으로 최적의 독립 통합 에너지 공급 시스템을 설계하였으며, 총 소요비용, 단위에너지비용 및 생애주기 이산화탄소 배출 분석 등, 다양한 지표를 이용하여 시스템의 경제성 및 환경성을 분석한다. 특히 다목적최적화 기법을 이용하여 최소 비용과 최소 이산화탄소 배출 등 두 목적함수를 동시에 만족하는 파레토 솔루션을 규명함으로써 신재생 자원 기반 독립 에너지 공급 시스템 설계의 가능성 및 효과를 정량적으로 분석하였다. 분석 결과, 신재생에너지 자원이 좋은 지역일수록 시스템 구축 비용 증가에 따른 이산화탄소 절감 효과가 높은 것으로 나타났다. 또한, 신재생에너지 자원 기반 에너지 공급 시스템의 전력 단가는 현재 기존 단가보다 평균 0.35~0.46 $/kWh높게 나타났으며, 이산화탄소 배출량의 경우 기존 배출량보다 470~490 gCO<sub>2</sub>/kWh정도의 저감효과를 보임을 분석하였다. This study aims to propose a new optimization-based approach for design and analysis of the stand-alone hybrid energy supply system using renewable energy sources (RES). In the energy supply system, we include multiple energy production technologies such as Photovoltaics (PV), Wind turbine, and fossil-fuel-based AC generator along with different types of energy storage and conversion technologies such as battery and inverter. We then select six different regions of Korea to represent various characteristics of different RES potentials and demand profiles. We finally designed and analyzed the optimal RES stand-alone energy supply system in the selected regions using multiobjective optimization (MOOP) technique, which includes two objective functions: the minimum cost and the minimum CO<sub>2</sub> emission. In addition, we discussed the feasibility and expecting benefits of the systems by comparing to conventional systems of Korea. As a result, the region of the highest RES potential showed the possibility to remarkably reduce CO<sub>2</sub> emissions compared to the conventional system. Besides, the levelized cost of electricity (LCOE) of the RES-based energy system is identified to be slightly higher than conventional energy system: 0.35 and 0.46 $/kWh, respectively. However, the total life-cycle emission of CO<sub>2</sub> (LCE<sub>CO2</sub>) can be reduced up to 470 gCO<sub>2</sub>/kWh from 490 gCO<sub>2</sub>/kWh of the conventional systems.
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Daehee Lee(이대희),Seulki Han(한슬기) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.10
[Purpose]The purpose of this study was to examine changes in muscle fatigue of the erector spinae, rectus abdominis, quadratus lumborum, and gluteus maximus muscles during repetitive lifting using the squat-to-lift and stoop-to-lift techniques. [Method] Participants were 17 healthy young students in their 20 s. The change in the median frequency of the surface electromyography signal was calculated between baseline and the fatigue trial, where fatigue was self-reported. [Results] A significant decrease in median frequency was identified for the quadratus lumborum and gluteus maximus muscles using the squat-to-lift technique (p < 0.05). [Conclusion] The squat-to-lift technique is associated with fatigue of the quadratus lumborum and gluteus maximus muscles and may not be preferable to the stoop-to-lift technique in all cases.
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Daehee Lee(이대희),Seulki Han(한슬기) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.11
This study aimed to investigate the effects of static stretching of the calf muscle on ankle position sense and dynamic balance ability following microwave diathermy. Participants were 28 healthy young students in their 20 s, who were divided into a microwave diathermy stretching group (MSG) and a stretching group (SG). A microwave was emitted to the calf muscle area to participants in the MSG. Static stretching was performed by standing on a quadriceps board for 15 minutes. The angle of the wedge was set to a range of 15–25°, representing a level of pain and discomfort allowed by the subjects. Before and after intervention, ankle dorsi-plantar flexion joint position sense (JPS) and dynamic balance ability were measured. The group source affected JPS error of dorsi-plantar flexion (p < 0.05) and JPS error increased with the SG more than the MSG. There was an increase in the dynamic balance score in both groups after the intervention compared to before the intervention. Microwave therapy prior to stretching can preserve JPS and balance ability, thereby reducing the risk of injuries from activities after stretching.
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Relationship between Hip Joint Position Sense and Balance Abilities
Daehee Lee(이대희),Seulki Han(한슬기) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.12
[Purpose] To investigate the correlation between joint position sense (JPS) during hip abduction and static/dynamic balance abilities. [Method] The study enrolled 22 healthy college undergraduates and a smartphone application known as Clinometer was used to measure JPS during hip abduction using the passive setting/active reproduction. Balance ability was measured at levels 12, 7, and 3 of the Biodex Balance System. The JPS error during hip abduction was correlated with balance ability in relation to sway level. [Results] Error in JPS during hip abduction was moderately correlated with all balance scores at all sway levels (r≥0.38, p≤0.04 for all), except for the anterior-posterior balance at levels 12 and 3 (r≤0.24, p≥0.30 for both). [Conclusion] A significant correlation existed between JPS during hip abduction and balance ability, regardless of sway level. Therefore, adequate sensory training of the hip joint is needed during balance training.
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Daehee Lee(이대희),Seulki Han(한슬기) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.3
[Objective] The objective of this study was to investigate the reliability of smartphone-based measurements of the upper body, thigh, and shin segmental angles, and the hip and knee joint angles when walking. [Method] The sample size of this study included eight young and healthy college students. In this study, smartphones were used to determine the changes in angles when the subjects walked with smartphones attached to their torso (upper body), thigh, and shin. The obtained angles represented segmental angles for the torso, thigh, and shin, and were later used to calculate hip and knee joint angles. Measurements were taken and then the test-retest method was used to evaluate the agreement between the test and retest results. [Results] According to the results, a very high reliability for the torso and shin segmental angles (ICC>0.75) and a high reliability for the thigh segmental angle and hip and knee joint angles (ICC>0.60) were displayed. [Conclusion] According to the results of this study, it was established that smartphones can be sufficiently used as devices for gait analysis.
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