• 방사성폐기물학회지
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• 제9권4호
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• pp.219-230
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• 2011

핵연료주기 분석 연구는 핵연료주기 단계에서 기술들을 분석하고 요건들을 도출하여 국가적 핵연료주기 정책 설정 및 추진을 체계적으로 수행하기 위한 연구이다. 시스템 분석 기술은 대상 시스템의 비교 분석 평가에 활용되며 핵연료주기를 대상으로 하는 경우 각 국가 또는 관심 범위에 따라 다양한 방법이 사용된다. 본 연구에서는 국내 선진 핵연료주기 개발을 위해 필요한 핵연료주기 분석 전략과 함께 이를 위해 사용될 수 있는 분석 기술들을 제시하였다. 핵연료주기 분석은 전략적으로 기술적 분석, 국내외 이해관계, 국가 에너지 프로그램과 연계되어야 한다. 이를 위해 다양한 핵연료주기를 비교하여 제시된 평가 지표에 따라 분석하는 연구는 트레이드 연구 방법을 적용하여 수행할 수 있다. 본 연구를 통한 조사 분석 결과 핵연료주기 분석 전략과 함께 방법적 측면에서 트레이드 연구가 선진 핵연료주기 도출에 활용될 수 있을 것으로 파악되었다. 트레이드 연구에 필수적인 평가지표를 선정하고 각 지표별 핵연료주기에 대한 정보를 얻기 위해서는 기술성숙도 분석 방법과 핵연료주기 시뮬레이터를 활용할 수 있을 것으로 제시하였다. 이들은 핵연료주기의 기술성, 경제성, 환경영향성 등을 비교 평가하여 기술개발을 위한 방향을 제시하고 체계적인 선진 핵연료주기 도출 및 실현에 기여할 것이다.

• 한국연소학회지
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• 제19권2호
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• pp.15-20
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• 2014

Environmental regulations are being reinforced for the solution of environmental pollution, that are global issues. Exhaust gas regulations of off-road engines also demand stepwise reduction emission from beginning of Tier 4 interim(2013). Characteristically, Tier 4 regulation apply the NRTC mode which is a transient cycle. And technical studies using NRTC mode are uncommon. In this study, for satisfy the Tier 4 final regulation on the NRTC mode, experimental study was conducted using a 3.4 L off-road engine. Fuel injection timing and injector hole number are chosen as parameters for investigation of combustion and exhaust gas characteristics on off-road diesel engine.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.412-420
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• 2003

This study describes the merits of PWM control of hydraulic system using high speed on-off valves. Generally, Electro-hydraulic valves can be classified into two classification: valves which are controlled by analog signal and which are controlled by digital. The former includes hydraulic servo valves and proportional valves which require A/D converters as interface to digital computer and too costly and sensitive to oil contamination because of complexity in structures. The latter includes high speed on-off valves which do not require A/D converters because they are normally operated in a pulse width modulation(PWM) method, and are low in price and robust to oil contamination because of their simple structures. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using 2/2way high speed on-off valves and to give a criterion for the stability of this system. The nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are simulated.

• 한국지진공학회논문집
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• 제26권4호
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• pp.157-164
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• 2022

The TMD has a simpler structure than other vibration control devices and shows excellent control performance for the standardized vibration occurring in the structure. However, when the vibration cycle of the structure coincides with the vibration cycle of the TMD due to the sudden external loads, the off-tuning occurs, which threatens the structure while increasing the vibration width of the TMD. Therefore, Electromagnetic Tuned Mass Damper (ETMD) was developed as a semi-active TMD that prevents off-tuning while exhibiting excellent control performance like TMD. To verify the control performance of the developed ETMD, the bending behavior control performance evaluation experiment using a simple beam bridge was performed. The experimental method compared the mutual control power by experimenting with the existing TMD method and the developed ETMD under nine excitation frequency conditions. As a result, it was confirmed that the control effect of ETMD was about 4.85% higher than that of TMD at 3.02Hz, which generates the maximum displacement in the simple beam bridge. Also, the off-tuning occurred in some excitation conditions when using TMD, although the off-tuning did not occur when using ETMD. Therefore, the excellent control performance of the ETMD developed in this study was verified.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.127-128
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• 2013

Off-gas power plant is a renewable energy power plant which generate electrical energy using the low calorie FOG and BFG as main fuel. This combined cycle power plant is comprised of gas turbines, gas compressors, steam turbines, generators, and auxiliary equipment such as gas mixer, mixing tank, and gas cooler. In this paper, a off-gas power plant and development of its several equipment using CFD are introduced.

• 신재생에너지
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• 제10권1호
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• pp.6-19
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• 2014

Organic Rankine cycle (ORC) has been widely used to convert renewable energy such as solar energy, geothermal energy, or waste energy etc., to electric power. For a small scale output power less than 10 kW, turbo-expander is not widely used than positive displacement expander. However, the turbo-expander has merits that it can operate well at off-design points. Usually, the available thermal energy for a small scale ORC is not supplied continuously. So, the mass flowrate should be adjusted in the expander to maintain the cycle. In this study, nozzles was adopted as stator to control the mass flowrate, and radial-type turbine was used as expander. The turbine operated at partial admission. R245fa was adopted as working fluid, and supersonic nozzle was designed to get the supersonic flow at the nozzle exit. When the inlet operating condition of the working fluid was varied corresponding to the fluctuation of the available thermal energy, optimal operating condition was investigated at off-design due to the variation of mass flowrate.

• 한국환경보건학회지
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• 제47권4호
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• pp.320-329
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• 2021

Background: Smoking exposure may be objectively assessed through specific biomarkers. The most common biomarker for smoking is cotinine concentration in urine, and setting an optimal cut-off point can accurately classify smoking status. Such a cut-off point for Korean adolescents has never been studied. Objectives: The aim of this study was to determine a cut-off point for urinary cotinine concentration for the discrimination of smoking in adolescents. Methods: Participants were adolescents aged 13~18 years who participated in the third cycle of the Korean National Environmental Health Survey. We used urine samples to confirm the level of cotinine concentrations. Smoking status was determined by self-reported questionnaire. We identified the optimal cotinine cut-off point for discriminating smoking status using receiver operating characteristic curve analysis. Results: Of the 904 participants, 28 (3.1%) were smokers, among whom 20 (71.4%) were male. The median urinary cotinine concentrations in smokers was 218 ㎍/L (male: 215 ㎍/L, female: 303 ㎍/L), and that in non-smokers was 1.31 ㎍/L (male: 1.46 ㎍/L, female: 1.18 ㎍/L). We found significant differences in urinary cotinine concentration according to smoking status and sex (p<0.001). Urinary cotinine concentrations performed well for identifying smoking adolescents [area under the curve: 0.954 (male: 0.963, female: 0.908)]. The cut-off that optimally distinguished smokers from non-smokers was 39.85 ㎍/L (sensitivity: 89.3%, specificity: 97.4%). Male [39.85 ㎍/L (sensitivity: 90.0%, specificity: 94.9%)] had a different optimal cut-off point than female [26.26 ㎍/L (sensitivity: 87.5%, specificity: 99.6%)]. Conclusions: This study determined a cut-off point for urinary cotinine of 39.85 ㎍/L (male: 39.85 ㎍/L, female: 26.26 ㎍/L) to distinguish smokers from non-smokers in adolescents.

• 한국유체기계학회 논문집
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• 제19권6호
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• pp.34-42
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• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• 한국추진공학회지
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• 제24권5호
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• pp.77-83
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• 2020

본 논문에서 연소기 산화제 개폐밸브의 작동 특성 변화를 확인하기 위해 극저온 및 상온 작동 시험으로 이뤄진 밸브 내구성시험 내용과 함께 시험 결과를 소개하였다. 극저온 및 상온 내구성시험을 통해 밸브 작동 횟수와 상관없이 밸브의 작동 특성이 매우 안정적으로 유지되는 것을 확인하였다. 밸브 작동 특성을 대표하는 주요 압력 측정값과 마찰력 및 스프링 예측값이 밸브 내구성시험 내내 대략 최대 ±3% 이내 수준에서 동일하게 측정되었으며, 연소기 산화제 개폐밸브의 이와 같은 안정적인 밸브 작동 특성은 해당 밸브가 적용되는 엔진의 안정적인 시동 및 종료를 위한 중요한 역할을 할 수 있을 것으로 기대한다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.198-208
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• 1998

For the development of a gas turbine engine, repetitive calculation process to determine design point and off-design performance based on basic design requirements resulted from the market survey is necessary Due attention then, must be given that design process must be carried out within the mechanical limits satisfying conservation laws of mass, work as well as speed equilibrium between the components for maximum performance. It is the purpose of the present study to deal with technical particulars during design point and off-design process of gas turbine engine performance analysis for simple cycle as well as combined cycle.