• 설비공학논문집
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• 제21권12호
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• pp.695-702
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• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• 한국가시화정보학회지
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• 제17권1호
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• pp.10-18
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• 2019

In this study, the temperature behavior of Pulsating Heat Pipe (PHP) according to the diameter change were studied by limiting the diameter change to only the evaporator. To investigate operation of PHP in various heat input, heat input power was increased from 10 to 120 W. The results show operation can be divided into 3 regimes by temperature behavior. Thermal resistance was increased before start-up and decreased with increasing heat input. At 110 W heat input, thermal conductivity of 2 mm PHP was 8 .times higher compare to thermal conductivity of copper. Further, to investigate details of temperature behavior in higher heat input, FFT analysis was conducted. Based on the results, when the deviation of peak frequency in each section is lowest, the thermal resistance has lowest value.

• 벤처창업연구
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• 제14권6호
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• pp.11-27
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• 2019

최근 국내 창업지원 정책은 스타트업 중심에서, 스케일업 중심으로 전환기를 맞고 있다. 제2벤처 '붐' 확산 전략(2019.3.6.)은 신규 벤처 투자 연 5조원 달성, 유니콘 기업 20개 창출, M&A 활성화와 역동적 회수 시장 조성을 발표하는 등 국내 스케일업 정책이 투자/금융 등 자금지원에만 집중되어 있는 것으로 확인되고 있다. 물론, 기업 성장을 위해서는 자금지원이 정책적으로 매우 중요한 것은 기존 연구를 통해 확인되고 있으나, 스케일업을 효과적으로 달성하기 위해서는 다양한 정책적 지원이 필요할 것으로 보인다. 이러한 한계를 극복하고자 본 연구는 미국, 영국 등 이미 스케일업 정책을 도입하여 운영 중인, 해외 선진국의 스케일업 지원정책을 문헌 등 자료를 분석하고, 이를 바탕으로 국내 스케일업 정책을 분석하여 효과적인 스케일업 정책을 수립할 수 있도록 시사점을 도출하고자 한다. 이를 통해 국정목표인 일자리 창출과 국가경제 성장에 효과적으로 기여할 수 있는 스케일업 지원 정책 수립에 시사점을 제공할 것으로 기대한다. 또한, 학술적으로는 국내외 스케일업에 대한 연구가 매우 부족한 실정으로, 이번 정책사례 비교연구를 통해서 시사점을 제안하여 향후 스케일업 관련 연구주제의 확장성 측면과 관련된 다양한 연구가 활성화 되는데 기여하고자 한다. 본 연구에서는 글로벌 정책사례로는 미국은 'ScaleUp America Initiative', EU는 'the Start-up and Scale-up Initiative' 정책, 영국은 'Scale Up Institute', 독일은 'German Accelerator', 프랑스는 '프렌치 테크(La French Tech)' 정책, 중국은 중관촌 등 스타트업의 핵심거점의 정책을 중심으로 문헌 등 자료조사를 통해 본 연구를 진행하였다.

• 전기학회논문지
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• 제65권6호
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• pp.979-986
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• 2016

At present, electric power industry around the world are being gradually changed to a new paradigm, such as electrical energy storage system, the wireless power transmission. Demand for ESS, the core technology of the new paradigm, has been growing worldwide. However, it is essential to estimate the optimal capacity of ESS facilities for frequency regulation because the benefit would be saturated in accordance with the investment moment and the increase of total invested capacity of ESS facilities. Hence, in this paper, the annual optimal mathematical investment model is proposed to estimate the optimal capacity and to establish investment plan of ESS facility for frequency regulation. The optimal mathematical investment model is newly established for each season, because the construction period is short and the operation effect for the load by seasons is different unlike previous the mathematical investment model. Additionally, the marginal operating cost is found by new mathematical operation model considering no-load cost and start-up cost as step functions improving the previous mathematical operation model. ESS optimal capacity is established by use value in use iterative methods. In this case, ESS facilities cost is used in terms of the value of the beginning of the year.

• 한국생산제조학회지
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• 제8권4호
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• pp.112-122
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• 1999

In realistic control systems the nonlinear saturation attributes of the control actuator due to physical limitations should be taken into account This nonlinear saturation of actuators may cause not only deterioration of the control performance but also a large overshoot during start-up and shut-down. As the overshoot increases the system may become oscillatory unstable. in this paper the supervisor implementation which guarantees good performance for saturation operation and prevents reset wind up is presented, Moreover the sufficient conditions of the stability for saturated system using supervisory control with a dynamic controller are provided in the continuous-time and in the discrete-time domain Numerical example is illustrated to depict the efficiency of supervisory control for a typical satuaurated production-distribution system controlled by a discrete-time dynamic controller and to validate basic results by simulation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.76-83
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• 2000

Boundary lubrication condition arises in most lubricated systems, especially during motion reversals and start up phase of operation. In this work electric contact resistance variations with respect to sliding conditions under lubrication is investigated The motivation was to improve the understanding of the contact condition in the boundary lubrication regime. It is shown that electrical contact resistance is sensitive to sliding speed and surface condition of the specimens. Also, phenomena such as run-in during the initial phase of sliding and lubricant pile up near the sliding pin could be observed. The results of this work will aid in better understanding of the metal to metal contact condition in lubricated systems.

• 건설관리
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• 제13권6호
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• pp.41-45
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• 2012

Nowadays the Project Management is increasingly adapted into almost all the fields in business management processes among leading companies both in Korea and overseas. However its actual practices are rare to be found. Among the Project Life Cycle, this report covers the real cases of the PMBOK knowledge areas in NPP Architect Engineering. The areas of the Construction, Start-up and Operation will be exception of the cases. By way of analyzing the KEPCO ENC's Processes/Procedures/Systems and the ones in PMBOK Guide, this report will show the contents in the PMBOK Guide is rather practical than theoretical. Meanwhile, implications whether the conclusions of this report might be applied to other industries such as general construction, non-nuclear plants, etc. should be left behind to follow-up studies.

• 한국항공운항학회지
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• 제14권2호
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• pp.71-78
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• 2006

In this paper, it is described on the exportation trend and future development paradigm of the localized small aircraft which was recently developed four seated canard type aircraft for exportation purpose. Presently, even though the development of small aircraft is recessed, if we start development of the proper airplane models by integrating domestic power of industry-university-institute on the base of research experience from now on, we can go into the global market and take up the level of world top 10 makers without doubt. For successful operation of exportation system of small aircraft, it is needed to set up development strategy paradigm by forming consortium centering around the medium and small enterprises.

• Tribology and Lubricants
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• 제16권5호
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• pp.381-388
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• 2000

Boundary lubrication condition arises in most lubricated systems, especially during motion reversals and start up phase of operation. In this work electric contact resistance variations with respect to sliding conditions under lubrication is investigated. The motivation was to improve the understanding of the contact condition in the boundary lubrication regime. It is shown that electrical contact resistance is sensitive to sliding speed and surface condition of the specimens. Also, phenomena such as run-in during the initial phase of sliding and lubricant pile up near the sliding pin could be observed. The results of this work will aid in better understanding of the metal to metal contact condition in lubricated systems.

• 한국산학기술학회논문지
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• 제21권10호
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• pp.317-324
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• 2020

천연가스를 연료로 사용하는 복합화력발전소는 석탄화력 대비 기동 및 정지가 용이하고 오염물질의 배출에 대한 부하가 적어 국내 발전설비 중 차지하는 비중이 꾸준히 상승하고 있다. 그러나 복합화력발전소는 가스터빈의 기동초기 및 저부하 운전 영역에서 황연현상을 일으키는 이산화질소(NO2)의 농도가 높은 특성을 가지고 있어 민원의 원인이 되며, 이의 제어 기술로서 황연제거설비가 2000년대 중반에 개발되어 운영되어 지고 있었다. 하지만 이 기술은 가스터빈 냉간기동 조건에서 기동초기 약 10~20분 동안은 기화시스템의 예열이 충분하게 이루어 지지 않아 황연현상을 제어할 수가 없는 실정이었다. 이에 본 연구에서는 환원제를 기화기를 사용하지 않고 액상의 상태로 가스터빈 Exhaust Duct에 직접 분사하여 황연현상을 제어하는 기술의 도출을 위해 CFD 해석 및 실증시험을 수행하였다. 가스터빈 Exhaust Duct에 위치에 있는 Diffuser에 의해 Duct의 외곽으로 형성된 배기가스에 액상의 환원제를 직분사하는 방안으로 배기가스 조건에 따라 5가지 Case로 분류하여 CFD를 수행하였으며, 그 결과 5가지 Case 모두에서 RMS가 15%이하로 양호한 혼합도를 보였다. 이를 바탕으로 실증설비를 설치 및 시험을 실시한 결과, 기존 기상주입방식에서 제어할 수 없었던 기동 초기 약 10~20분 구간의 황연현상도 완벽하게 제어할 수 있었다.