• 대한기계학회논문집
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• 제1권2호
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• pp.95-103
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• 1977

The expermental research was carried out to investigate the thermal performance of the locally manufactured radiators for 1300cc automobiles. The choice of .epsilon. value (the ratio of water tube surface area to the total heat transfer area ) resulted in remarkable difference in their performance including the Louver effect, the overrall heat tranfer coefficient and the heat dissipation capability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.109-110
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• 2008

전체송전용량은 열 안정도, 과도안정도, 전압안정도 등에 의하여 제한을 받게 되는데, 한전 전력시스템에서는 주로 전압안정도에 의하여 제한을 받는다. 현재에도 상당한 규모로 북상조류가 흐르고 있어서, 전력시스템의 안정도를 고려한 융통전력의 한계가 중요한 문제로 부각되고 있다. 본 논문에서는 평가선로 조류의 모선 전력 민감도를 활용하여 전체송전용량을 산정하는 기법이 IEEE 39 모선 테스트 시스템에 적용되며, 실제적으로 운용하고 있는 경제급전의 순서인 Merit order(우선 순위)를 적용하여 전체송전용량 산정을 하는 것과의 결과를 비교 검토한다.

• 에너지공학
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• 제24권1호
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• pp.42-50
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• 2015

신형 원전의 피동격납건물냉각계통(PCCS: Passive Containment Cooling System)을 구성하는 단일 전열관의 열제거 성능을 평가하기 위해, 비응축성 기체 존재 시 수직 튜브 외벽에서 발생하는 증기의 응축 열전달에 대한 실험을 수행하였다. 외경 40 mm, 길이 1.0 m의 전열관 외벽에서 증기-공기 혼합물의 평균 열전달계수를 측정하였으며, 압력 2-4 bar, 공기의 질량분율 0.1-0.7의 범위에서 실험데이터를 수집하였다. 이를 통해 압력과 비응축성기체의 농도가 응축 열전달계수에 미치는 영향을 평가하였다. 실험결과를 기존의 열전달모델인 Uchida와 Dehbi의 상관식과 비교하였으며, 이들 상관식은 실험결과에 비해 상대적으로 열전달계수를 낮게 예측함을 확인하였다.

• 한국응급구조학회지
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• 제26권2호
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• pp.73-85
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• 2022

Purpose: The purpose of this study is to understand currently active Korean paramedics' disaster response abilities, including immediate response, severity classification, patient treatment, and patient transfer, in a disaster situation with multiple casualties. Methods: A structured questionnaire consisting of a total of 25 questions was used, including 5 questions on the subject's general characteristics and 20 questions on disaster-related emergency response abilities. Results: Among the disaster response abilities of the participants, the patient transport ability scores were high and the cooperative support ability scores were low. In terms of general characteristics, there was a significant difference in age, and it was high in the 40s, and there was a significant positive correlation between each competency. Conclusion: These results suggest that there is an urgent need to develop a systematic and specialized educational system with components inside and outside fire departments related to multiple casualty disasters to improve overall abilities.

• Journal of Astronomy and Space Sciences
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• 제36권4호
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• pp.293-306
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• 2019

In this study, the observational arc-length effect on orbit determination (OD) for the Korea Pathfinder Lunar Orbiter (KPLO) in the Earth-Moon Transfer phase was investigated. For the OD, we employed a sequential estimation using the extended Kalman filter and a fixed-point smoother. The mission periods, comprised between the perigee maneuvers (PM) and the lunar orbit insertion (LOI) maneuver in a 3.5 phasing loop of the KPLO, was the primary target. The total period was divided into three phases: launch-PM1, PM1-PM3, and PM3-LOI. The Doppler and range data obtained from three tracking stations [included in the deep space network (DSN) and Korea Deep Space Antenna (KDSA)] were utilized for the OD. Six arc-length cases (24 hrs, 48 hrs, 60 hrs, 3 days, 4 days, and 5 days) were considered for the arc-length effect investigation. In order to evaluate the OD accuracy, we analyzed the position uncertainties, the precision of orbit overlaps, and the position differences between true and estimated trajectories. The maximum performance of 3-day OD approach was observed in the case of stable flight dynamics operations and robust navigation capability. This study provides a guideline for the flight dynamics operations of the KPLO in the trans-lunar phase.

• Tribology and Lubricants
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• 제27권6호
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• pp.293-301
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• 2011

Understanding of the tribological characteristics of polytetrafluoroethylen (PTFE) and ultra-high-molecular-weight polyethylene (UHMWPE) is crucial for their applications such as bearing and total joint replacement. In this work, the effect of the surface roughness of carbon steel on the tribological behaviors of PTFE and UHMWPE was experimentally investigated by using block-on-ring tribotester with friction force monitoring capability. It was found that that the amount of material transfer layers of PTFE formed on the carbon steel was significantly larger than those of UHMWPE, which was responsible the lower friction coefficient of PTFE. It was also concluded that the effect of surface roughness of carbon steel on the friction coefficient of UHMWPE was more significant than that of PTFE. For UHMWPE, it was found that the effect of surface roughness of counterface was varied with respect to applied normal force and sliding as well. Based on Archard's wear law, the wear coefficient of PTFE and UHMWPE was calculated to be $3{\times}10^{-5}$ ~ $8{\times}10^{-5}$ and $7{\times}10^{-6}$ ~ $2{\times}10^{-5}$, respectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.317-320
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• 2004

In this paper, it is analyzed a performance improvement of ACL Packet using turbo code scheme in bluetooth system. In order for segment to improve the transfer capability, the transmission of messages have been simulated using a fragmentation that begins with the total package and incremental fragmentation for each layer using the TCP to define the resultant packet size and the level of fragmentation for each proceeding layer. This turbo code scheme decreases transmission time of L2CAP baseband packets by sending packets. From the results, we were able to obtain packet transmission time, optimal TCP packet size, ACL(DM packet) in AWGN.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.199-201
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• 2005

This paper proposes a method to evaluate the TTC by considering uncertainty of weather. Impact of the contingency on the system performance could not be addressed in a deterministic way because of the random nature of the system equipment outage and the increase of outage probability according to weather condition. For this reasons, probabilistic approach is necessary to realize evaluation of TTC. This method uses a sequential MCS. In sequential simulation, the chronological behavior of the system is simulated by sampling sequence of the system operating states based on the probability distribution of the component state duration. Therefor, MCS is used to accomplish the probabilistic calculation of TTC with consideration of weather condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.223-225
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• 2005

This paper presents a scheme to solve the congestion problem using hybrid control with phase-shifting transformer(PST) and power generation in power systems. A good design of PST and power generation control can improve total transfer capability(TTC) in interconnected systems. This paper deals with an application of optimization technique for TTC calculation. The optimization method is used to maximize power flow of tic line subject to security constraints such as voltage magnitude and real power flow. The proposed method is applied to 10 machines 39 buses model systems to show its effectiveness.

• 한국정밀공학회지
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• 제18권11호
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• pp.155-160
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• 2001

To achieve high precision cutting as well as production capability in the machine tool, it is needed to develop excellent rigidity statically, dynamically and thermally as well. In order to predict the qualitative behavior of a machine tool, simultaneous analysis of mechanics and heat transfer is required. Generally, machine tool designers have solved designing problems based on partial estimation of the specified rigidity. This study clears the inter-relationship between therm, and propose multi-phase optimization of machine tool structure using a genetic algorithm. The multi-phase solution method is consists of a series of mechanical design problem. At this first phase of static design problem, multi-objective optimization for the purpose of minimization of the total weight and static compliance minimization is solved using the Pareto Genetic Algorithm.