• 설비공학논문집
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• 제22권12호
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• pp.873-880
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• 2010

The present study developed a computer simulation program to determine the optimum strategy and capacity of a micro combined heat and power(CHP) system. This simulation program considered a part-load electrical/thermal efficiency and transient response characteristics of CHP unit. The result obtained from the simulation was compared with the actual operation of 30 kW gas engine driven micro CHP system. It was found that the simulation could reproduce the daily operation behavior, such as operating hours and mean load factor, closely to the actual behavior of the system and could predict the amount of electrical/thermal output and fuel consumption with the error of less than 12%.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1064-1072
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• 2017

The power of controlled generators in microgrids randomly fluctuate because of the stochastic volatility of the outputs of photovoltaic systems and wind turbines as well as the load demands. To address and dispatch these stochastic factors for daily operations, a dynamic economic dispatch model with the goal of minimizing the generation cost is established via chance-constrained programming. A Monte Carlo simulation combined with particle swarm optimization algorithm is employed to optimize the model. The simulation results show that both the objective function and constraint condition have been tightened and that the operation costs have increased. A higher stability of the system corresponds to the higher operation costs of controlled generators. These operation costs also increase along with the confidence levels for the objective function and constraints.

• 디지털산업정보학회논문지
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• 제8권3호
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• pp.87-95
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• 2012

Up to now, industrial cranes play important roles as the effective machines to carry heavy loads in the manufacturing premise, in the construction field and so on. And, a crane is widely used not only to daily work but also to carry heavy materials efficiently in a construction site for prevention of accident. However, the crane operation is highly complicated even for experts. In this paper, we developed the content of the crane mounted on the controller. This content overload conditions in the operating environment for the crane operator to warn, and the operation of equipment has the capability to limit automatically. The content for crane controller is to alert the operator overload and to limit the operation of equipment for stabilizing capabilities. The content of the flexible algorithm is based on stabilizing controllers, PLC (Programmable Logic Controller) to connect for using the equipment and electrical control systems to ensure the safety of workers and to improve the ability to work possible.

• 한국위성정보통신학회논문지
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• 제8권2호
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• pp.80-87
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• 2013

통신, 해양, 기상의 세 분야 복합 임무를 수행하는 천리안위성(Communication Ocean Meteorological Satellite: COMS)은 정지궤도 동경 $128.2{\circ}$에서 2011년 4월부터 현재 정상 운영 임무를 수행하고 있다. 세 임무를 수행하기 위해 천리안위성에는 3가지 탑재체인 기상탑재체(Meteorological Imager: MI), 해양탑재체(Geostationary Ocean Color Imager: GOCI), 통신탑재체(Ka-band communication payload)가 실려 있다. 세 가지 임무 운영과 위성 유지 관리를 위해 위성 관제가 실시간 운영으로 수행된다. 위성 실시간 운영은 명령과 원격측정자료를 통해 위성과 직접 통신하는 업무이다. 본 논문에서는 천리안위성의 실시간 운영 특성으로 지상국 장비 구성과 일일, 주간, 월간, 계절별, 연간 운영 업무 특성을 논하였다. 천리안위성의 궤도상 시험(In-Orbit-Test: IOT) 말기와 정상 운영 첫 해가 포함되는 2011년의 1년간 운영 결과에 대한 토의를 통해 성공적인 실시간 운영 결과 확인도 제시하였다.

• 한국농공학회논문집
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• 제65권5호
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• pp.37-49
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• 2023

The drought risk has been increasing recently due to climate change causing the extreme climate to be more frequent. In order to supply agricultural water stably under drought, it is necessary to operate an agricultural reservoir in response to drought. To this end, it is crucial to establish appropriate drought response operation rules considering weather conditions and reservoir status. In the reservoir operation simulation, the supply amount differs from the actual reservoir supply for many reasons, including maintaining water levels for supply and accommodating farmers' requests. So, for a more realistic reservoir operation simulation, it is necessary to reflect the reservoir operation rules of the actual water management site. Therefore, in this study, through a survey, the standards for limitation of agricultural water supply applied to agricultural reservoirs in Korea were investigated, and the criteria for drought response reservoir operation (DRO) were established based on the survey. Then, the DRO was applied to the irrigation period for nine subject reservoirs. The applicability was evaluated by comparing the DRO result to the operation result of HOMWRS (Hydrological Operation Model for Water Resources System). The reservoir drought index, storage rate, and daily supply were compared for evaluation. From the result, DRO showed more stable operation results in most cases against drought as it has fewer days of water supply limitation and a somewhat reservoir storage rate which can be utilized for prolonged drought.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2002년도 추계학술발표논문집
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• pp.141-144
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• 2002

Recently, the operation of power distribution systems has become more difficult because the peak demand load is increasing continuously and the daily load factor is getting worse and worse. Also, the consideration of deregulation and global environment in electric power industry is required. In order to overcome these problems, a study on the planning and operation in distribution systems of dispersed generating sources such as fuel cell systems, photovoltaic systems and wind power systems has been performed energetically. This study presents a method for determining an optimal operation strategy of dispersed co-generating sources, especially fuel cell systems, in the case of both only electric power supply and thermal supply as well as electric power supply. In other words, the optimal operation of these sources can be determined easily by the principle of equal incremental fuel cost and the thermal merits is evaluated quantitatively through Kuhn-Tucker's optimal conditions. In order to select the optimal locations of those sources, an priority method using the comparison of total cost at the peak load time interval is also presented. The validity of the proposed algorithms is demonstrated using a model system.

• 대한전기학회논문지:전력기술부문A
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• 제50권6호
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• pp.265-274
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• 2001

Recently, the operation of power systems has become more difficult because the peak demand load is increasing continuously and the daily load factor is getting worse and worse. Also, the consideration of deregulation and global environment in electric power industry is required. In order to overcome those problems, a study on the planning and operation in power systems of dispersed generating sources such as fuel cell systems, photovoltaic systems and wind power systems, has been performed energetically. This paper presents a method for determining an optimal operation strategy of dispersed co-generating sources, especially fuel cell generation systems, considering thermal supply as well as electric power supply. In other words, the optimal operation of those sources can be determined easily by the principle of equal incremental fuel cost and the thermal merit of those sources can be also evaluated quantitatively through Kuhn-Tucker's optimal conditions. In additions, an priority method using the comparison of total cost at the peak load time interval is presented in order ot select the optimal locations of those sources. The validity of the proposed algorithms is demonstrated using a model system.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.1403-1407
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• 2005

In order to analyze the water storage of the Daecheong dam after constructing the Yongdam dam situated in upstream, a daily cascaded simulation model for analyzing water storages in the Yongdam-Daecheong dams was developed. Operation scenarios of the Yongdam dam were selected to 8 cases with the combinations of downstream outflows and water supplies to the Jeonju region. Daily water storages in the Daecheong dam was analyzed daily by simulating from 1983 to 2004. The results are summarized as follows. Firstly, water supplies from the Daecheong dam were analyzed to amount $1,964.2Mm^3$ on a yearly average in case without the Yongdam dam. In case with the Yongdam dam, water supplies from the Daecheong dam were analyzed to amount $1,858.7\~1,927.3Mm^3$ in case with downstream outflow of $5\;m^3$ is, and were analyzed to amount $1,994.9\~2,017.8Mm^3$ in case with downstream outflow of $10\;m^3/s $. These values are compared to $1,649Mm^3$ applied in design. Secondly, reservoir use rate which was defined rate of water supply to effective water storage reached $241.3\% in case without the Yongdam dam. In case with the Yongdam dam, reservoir use rate reached $228.3\~236.8\% In case with downstream outflow of $5\;m^3/s$, and reached $245.1\~247.9\% in case with downstream outflow of $10\;m^3/s$. Thirdly, runoff rate which is defined rate of dam inflow to areal rainfall reached $57.3\% in case without the Yongdam dam. In case with the Yongdam dam, reservoir use rate reached $62.0\~68.4\% in case with downstream outflow of $5\;m^3/s$, and reached $64.1\~68.5\% in case with downstream outflow of $10\;m^3/s$. Fourth, in case with downstream outflow of $10\;m^3/s$ is from the Yongdam dam, appropriate water supply amounts to the Jeonju region were analyzed to only $0.50Mm^3/day$ from the daily simulation of water storages in the Yongdam dam. Comprehensively, water supply capacity of the Daecheong dam was analyzed to affect in small amounts in spite of the construction of the Yonsdam dam. It is effected to achieve the effective water management of the Yongdam dam and the Daecheong dam by using the developed cascaded model.

• 한국병원경영학회지
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• 제10권3호
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• pp.45-66
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• 2005

The purpose of this study was to analyze related factors affecting profitability on general hospitals(300-499 beds). The data were derived from survey by the Korean Hospital Association on 33 hospitals during 10 years (from 1993 to 2002). Profitability was measured by 3 ratios - net profit to total assets, normal profit to total assets and operating margin to gross revenue - as dependent variables. Independent variables were classified by general factors (ownership, number of bed, period of establishment, region), financial factors (total asset turnover, current ratio, liabilities to total assets, personnel costs per operation profit, material costs per operation profits), productivity index(number of daily patient per nurse), the score of quality assurance activity and the time lag score. Multiple regression model was used in this study. First, Number of bed, region was not statistically significant for profitability. But ownership was affect positively to normal profit to total assets and operating margin to gross revenue. Private hospitals had higher profitability than that of public hospitals Second, the score of quality assurance activity was not statistically significant to profitability. Third, Those hospitals having more daily patient per nurse had significantly higher profitability than the others. Fourth, Those hospitals having higher proportion in total asset turnover had significantly higher profitability than other hospitals. But liabilities to total assets and liquidity ratio had no difference to the profitability. Those hospitals having higher proportion in personnel costs and material costs per operation profits had significantly lower hospital profitability than others.

• 과학교육연구지
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• 제46권1호
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• pp.40-52
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• 2022

참여형 과학문화 확산의 일환으로 지속되어 온 생활과학교실은 효과적인 학교 밖 체험·탐구 활동으로서 과학의 대중화에 앞장서왔다. 그러나 최근의 코로나19 상황으로 생활과학교실 역시 비대면으로 전환하거나 대면-비대면 교육을 조합할 수밖에 없는 환경이 되었으며, 이러한 교육의 변화가 여전히 학생들의 과학에 대한 관심과 흥미를 제고하는데 효과적인지 검토가 필요한 시점이다. 이에 본 연구에서는 비대면 생활과학교실 프로그램에 참여한 초등학생들의 평소 관심 분야, 과학기술에 대한 인식, 과학에 대한 관심과 흥미, 과학적 역량이 어떻게 변화되는지 확인하고 학생과 학부모들의 인식 차이를 비교함으로써 비대면 생활과학교실의 교육 효과성을 제고하고 향후 운영 방안에 대해 모색하였다. 연구 결과 비대면 생활과학교실 프로그램 참여 이후 학생들은 과학기술 발전이나 미래기술, 환경오염, SNS에 대한 관심 등이 높아지고 게임에 대한 관심이 줄어드는 경향을 보였다. 또한 과학기술 활동에 대한 관심, 과학에 대한 흥미, 과학적 역량도 증가하여 비대면 생활과학교실의 교육 효과를 확인할 수 있었다. 이를 바탕으로 생활과학교실의 학습 주제와 내용 수준을 다양화하고 소외된 학습자들에게 비대면 과학 학습의 기회를 확대하며, 최신 미디어를 활용한 과학콘텐츠 개발과 공유가 필요함을 제언하였다.