• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 추계종합학술대회 B
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• pp.112-115
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• 2008

본 논문에서는 AMBA 기반으로 사용될 수 있는 H.264용 High Profile IP를 제안한다. 설계된 모듈은 한 매크로 블록 당 최대 306 cycle내에 동작한다. 제안된 Encoder 구조를 검증하기 위하여 JM 13.2부터 reference C를 개발하였으며, reference C로부터 test vector를 추출하여 설계 된 회로를 검증하였다. 우리는 Hardware cost를 줄이기 위하여 plan mode를 제거하였고, SAD 계산 방법을 사용하여 Hardware cost와 cycle을 줄이는 방법을 채택하였다. 제안된 회로는 133MHz clock에서 동작하며, 합성결과 TSMC 0.18um 공정에 램 포함 25만 gate크기이다.

• 한국압력기기공학회 논문집
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• 제7권4호
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• pp.44-50
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• 2011

Turbulent mixing of hot and cold coolants is one of the possible causes of high cycle thermal fatigue in piping systems of nuclear power plants. A typical situation for such mixing appears in turbulent flow through a T-junction. Since the high cycle thermal fatigue caused by thermal striping was not considered in the piping fatigue design in several nuclear power plants, it is very important to evaluate the effect of thermal striping on the integrity of mixing tees. In the present work, before conducting detailed evaluation, three thermal striping evaluation methodology suggested by EPRI, JSME and NESC are analyzed. Then, a by-pass pipe connected to the shutdown cooling system heat exchanger is investigated by using these evaluation methodology. Consequently, the resulting thermal stresses and the fatigue life of the mixing tee are reviewed and compared to each other. Futhermore, the limitation of each methodology are also presented in this paper.

• Structural Engineering and Mechanics
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• 제40권6호
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• pp.847-866
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• 2011

The objective of this study was to experimentally investigate the bond-related tension stiffening behavior of flexural reinforced concrete (RC) beams made with lightweight aggregate concrete (LWAC) under various high-cycle fatigue loading conditions. Based on strain measurements of tensile steel in the RC beams, fatigue-induced degradation of tension stiffening effects was evaluated and was, compared to reinforced normal weight concrete (NWC) beams with equal concrete compressive strengths (40 MPa). According to applied load-mean steel strain relationships, the mean steel strain that developed under loading cycles was divided into elastic and plastic strain components. The experimental results showed that, in the high-cycle fatigue regime, the tension stiffening behavior of LWAC beams was different from that of NWC beams; LWAC beams had a lesser reduction in tension stiffening due to a better bond between steel and concrete. This was reflected in the stability of the elastic mean steel strains and in the higher degree of local plasticity that developed at the primary flexural cracks.

• 한국정보통신학회논문지
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• 제12권11호
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• pp.2045-2049
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• 2008

본 논문에서는 AMBA 기반으로 사용될 수 있는 H.264용 High Profile Intra Prediction을 구조를 제안한다. 설계된 모듈은 한 매크로 블록 당 최대 306 cycle내에 동작한다. 제안된 Encoder 구조를 검증하기 위하여 JM 13.2로부터 reference C를 개발하였으며, reference C로부터 test vector를 추출하여 설계된 회로를 검증하였다. 우리는 Hardware cost를 줄이기 위하여 plan mode를 제거 하였고, SAD 계산 방법과 8 pixel 병렬처리 등을 사용하여 Hardware cost와 cycle을 줄이는 방법을 채택하였다. 제안된 회로는 Full HD1080@fps 영상을 133MHz clock에서 동작시킬 수 있으며, 합성결과 TSMC 0.18um 공정에 램 포함 25만gate크기 이다.

• Journal of Power Electronics
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• 제19권2호
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• pp.454-462
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• 2019

When compared to traditional bridge-type inverters, the dual-buck inverter has a higher reliability due to the fact that its bridge legs do not have a shoot-through problem. In this paper, the working principle of the dual-buck inverter is analyzed. A comparison of the working modes under full-cycle and half-cycle control is discussed. With half-cycle control, the inverter can realize a higher efficiency. However, this results in current zero-crossing distortion. The corresponding control strategy of the dual-buck inverter is proposed in order to realize both high efficiency and low current harmonic distortion. In addition, the system stability is analyzed. Dead-time is unnecessary due to the advantages of the topology. Thus, the current harmonic distortion can be further reduced. An inverter with the proposed control strategy has the advantages of high reliability, high efficiency and low current harmonic distortion. Finally, simulation and experimental results are given to verify the theoretical analysis.

• 과학교육연구지
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• 제45권3호
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• pp.275-291
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• 2021

이 연구의 목적은 인간 활동의 영향을 고려하여 지구 시스템 내에서 물질 순환에 대한 중·고등학생들의 시스템 사고의 수준과 특성을 분석하는 것이다. 이를 위해 2015 개정 교육과정 분석을 통해 평가 문항을 개발하였으며, 시스템 사고를 적용하여 평가 루브릭을 개발하였다. 한국 지구과학 올림피아드에 참여한 중·고등학생을 연구 대상으로 하였다. 평가 문항을 이용하여 수집된 학생 응답을 평가 루브릭을 이용하여 시스템 사고 수준을 결정하였으며, 단어 분석을 이용하여 시스템 사고의 특성을 파악하였다. 이를 토대로 인간 활동의 영향을 고려한 교육과정 개선을 논의하였다. 연구 결과는 다음과 같다: 첫째, 대다수 중등학교 학생의 시스템 사고수준이 물질의 순환에 대한 시스템 요소를 확인하거나 분류하는 낮은 수준이었으며, 시스템 연관이나 경향의 일반화와 같은 높은 수준은 상대적으로 적은 비율인 것으로 나타났다. 물의 순환보다 탄소의 순환에서 학생들의 시스템 사고 수준이 높은 것으로 나타났다. 둘째, 물질 순환에 대한 시스템 사고의 특성은 물의 순환에서는 물을 주요 시스템 요소로 인지한 상태로 기권과 다른 시스템 요소 간에 주로 증발로 연관을 나타내고 있었다. 탄소의 순환에서는 이산화 탄소를 주요 시스템 요소로 간주하여 생물권과의 연관으로 광합성과 호흡을 표상하고 있었다. 셋째, 지구 시스템 내 물질의 순환에서 인간 활동의 영향을 고려한 교육을 위해서 기존의 지구 시스템에서 확장하여 사회-생태 시스템을 고려한 교육과정의 개선을 제언하였다.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1025-1032
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• 2010

Gas turbine compressor blades used in a combined cycle power plant are possibly damaged and fractured during their operation. There are two possible causes of the failure of compressor blades; one is a defect of material quality which can be detected through some microscopic inspections for the fracture section, the other is high cycle fatigue problem caused by vibration and can be diagnosed by carrying out dynamic characteristics analysis for the blades. In this paper, in order to determine the cause of the failure of compressor blades in a combined cycle power plant, examination of the fracture section and the propagation mechanism of the crack via stress analysis are performed. Dynamic characteristics analysis via FRF estimation is also performed to identify the cause of failure.

• 전기학회논문지
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• 제60권11호
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• pp.2176-2181
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• 2011

This paper estimates the life cycle cost(LCC) of a propulsion control system using the maintenance information in the high speed train(KTX-1). Life cycle costing is one of the most effective approaches for the cost analysis of long-life systems such as the KTX-1. Until now, most life cycle cost of the system has been studied as a whole system viewpoint. But in case of railway industry, LCC studies are needed on the subsystem like a propulsion control system because subsystems are developed continuously localization. This paper proposes the life cycle cost model which fitted to estimate life cycle cost (LCC) using maintenance information manual. As a result, LCC on propulsion control system increased moderately expect for periodical time when major parts are replaced at the same time. Results will be reflected in the development of domestic products.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.460-468
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• 2008

Recent activities on the scramjet and rocket-ramjet combined-cycle engine of Japan Aerospace Exploration Agency(JAXA) are herein presented. The scramjet engines and combined-cycle engines have been studied in the world and JAXA has also studied such the engines experimentally, numerically and conceptually. Based on the studies, 2 to 3 m long, hydrogen-fueled engine models were designed and tested at the Ramjet Engine Test Facility(RJTF) and the High Enthalpy Shock Tunnel(HIEST). A scramjet engine model was tested in Mach 10 to 14 flight condition at HIEST. A 3 m long scramjet engine model was designed to reduce a dissociation energy loss in a high temperature condition. Drag reduction by a tangential injection and two ways of a transverse fuel injection were examined. Combustor model tests at three operating modes of the combined-cycle engine were conducted, demonstrating the combustor operation and producing data for the engine design at each mode. Aerodynamic engine model tests were conducted in a transonic wind tunnel, demonstrating the engine operation in the ejector-jet mode. A 3 m long combined-cycle engine model has been tested in the ejector-jet mode and the ramjet mode since March 2007. Carbon composite material was examined for application to the engines. Production of the cooling channel on a nickel alloy plate succeeded by the electro-chemical etching.

• 소성∙가공
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• 제31권5호
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• pp.253-260
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• 2022

In this study, the microstructural characteristics of a high-speed-extruded Mg-5Bi-3Al (BA53) alloy and its tensile, compressive, and high-cycle fatigue properties are investigated. The BA53 alloy is successfully extruded at a die-exit speed of 16.6 m/min without any hot cracking using a large-scale extruder for mass production. The homogenized BA53 billet has a large grain size of ~900 ㎛ and it contains fine and coarse Mg₃Bi₂ particles. The extruded BA53 alloy has a fully recrystallized microstructure with an average grain size of 33.8 ㎛ owing to the occurrence of complete dynamic recrystallization during high-speed extrusion. In addition, the extruded BA53 alloy contains numerous fine lath-type Mg₃Bi₂ particles, which are formed through static precipitation during air cooling after exiting the extrusion die. The extruded BA53 alloy has a high tensile yield strength of 175.1 MPa and ultimate tensile strength of 244.4 MPa, which are mainly attributed to the relative fine grain size and numerous fine particles. The compressive yield strength (93.4 MPa) of the extruded BA53 alloy is lower than its tensile yield strength, resulting in a tension-compression yield asymmetry of 0.53. High-cycle fatigue test results reveal that the extruded BA53 alloy has a fatigue strength of 110 MPa and fatigue cracks initiate at the surface of fatigue test specimens, indicating that the Mg₃Bi₂ particles do not act as fatigue crack initiation sites. Furthermore, the extruded BA53 alloy exhibits a higher fatigue ratio of 0.45 than other commercial extruded Mg-Al-Zn-based alloys.