• 한국해양환경ㆍ에너지학회지
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• 제7권1호
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• pp.47-55
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• 2004

본 논문은 1998년부터 2002년까지 대한민국 홍도 해역에 설치된 파향파고계에서 계측된 파랑자료를 이용하여 홍도 해역 파랑의 통계적 특성을 살펴보았다. 파랑관측율과 평균파고, 평균주기, 파향을 하였다. 그리고 파고-주기결합분포표를 작성하였고, n년 반복주기 파고와 최대 파고의 주기를 추정하였다. 2000년과 2002년에 발생한 태풍 "프라피룬"과 "루사"에 의한 파랑의 특성을 파악하였다.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.519-526
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• 2006

For investigating the effect of fuel stratification on flame propagation, initial flame development and propagation were visualized under different axially stratified states in a port injection SI engine. Stratification was controlled by the combination of the port swirl ratio and injection timing. Experiments were performed in an optical single cylinder engine modified from a production engine and images were captured through the quartz window mounted in the piston by an intensified CCD camera. Firstly in this paper, the characteristics under no port-generated swirl condition, i.e. normal conventional case was studied. Under various stratified conditions, flame images were captured at the pre-set crank angles. These were averaged and processed to characterize the flames propagation. The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance, and mean absolute deviation of propagating direction. Results show that stratification state according to injection timing do not affect on the direction of flame propagation. The flame development and the initial flame stability are strongly dependent on the stratified conditions and the initial flame stability is closely related to the engine stability and lean misfire limit.

• 한국해양환경ㆍ에너지학회지
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• 제9권2호
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• pp.65-71
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• 2006

본 연구는 부산지역내에 어촌 및 어항을 방문하는 방문객과 어촌 및 어항개발에 직접적 또는 간접적으로 관련이 있는 지역주민을 대상으로 설문조사를 수행하였다. 설문 내용은 어촌 및 어항개발이 지역사회에 미치는 영향, 어촌 및 어항개발 시 고려/개선사항, 투자우선순위 어촌 및 어항 개발방향에 대한 것으로 초점을 두었다. 설문조사 결과를 바탕으로 향후 부산지역에서의 어촌 어항개발 방향을 모색하고자 하였다.

• Smart Structures and Systems
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• 제13권1호
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• pp.1-24
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• 2014

The present study deals with two dimensional electro-elastic analysis of a functionally graded piezoelectric (FGP) cylinder under internal pressure. Energy method and first order shear deformation theory (FSDT) are employed for this purpose. All mechanical and electrical properties except Poisson ratio are considered as a power function along the radial direction. The cylinder is subjected to uniform internal pressure. By supposing two dimensional displacement and electric potential fields along the radial and axial direction, the governing differential equations can be derived in terms of unknown electrical and mechanical functions. Homogeneous solution can be obtained by imposing the appropriate mechanical and electrical boundary conditions. This proposed solution has capability to solve the cylinder structure with arbitrary boundary conditions. The previous solutions have been proposed for the problem with simple boundary conditions (simply supported cylinder) by using the routine functions such as trigonometric functions. The axial distribution of the axial displacement, radial displacement and electric potential of the cylinder can be presented as the important results of this paper for various non homogeneous indexes. This paper evaluates the effect of a local support on the distribution of mechanical and electrical components. This investigation indicates that a support has important influence on the distribution of mechanical and electrical components rather than a cylinder with ignoring the effect of the supports. Obtained results using present method at regions that are adequate far from two ends of the cylinder can be compared with previous results (plane elasticity and one dimensional first order shear deformation theories).

• 한국지진공학회논문집
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• 제3권1호
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• pp.123-132
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• 1999

댐-호소 계의 지진응답해석에 있어서의 어려운 문제 중 하나는 댐 상류방향으로의 에너지 방사를 적절하게 처리하는 것이다 본 논문에서는 깊이가 일정한 호소 원역으로의 에너지 방사를 잘 모델링할 수 있는 전달경계를 제시하였다 개발된 방법에서 수면파의 영향을 고려하였으며 호소-지반의 상호작용을 근사적으로 표현할수 있는 흡수경계조건도 도입하였다 댐과 호소의 경계면이 지표면에 수직하고 호소의 깊이가 일정할 경우에는 제안된 전달경계를 댐체의 모델에 직접 연결할 수 있다 댐체는 선형탄성거동을 가정하여 유한요소로 모델링 하였다 얻어진 댐-호소 계의 운동방정식을 이용하여 댐의 지진응답특성을 조사하였다

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1417-1428
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• 2020

The design of a nuclear reactor core requires basic thermal-hydraulic information concerning the heat transfer regime at which onset of nucleate boiling (ONB) will occur, the pressure drop and flow rate through the reactor core, the temperature and power distributions in the reactor core, the departure from nucleate boiling (DNB), the condition for onset of flow instability (OFI), in addition to, the critical velocity beyond which the fuel elements will collapse. These values depend on coolant velocity, fuel element geometry, inlet temperature, flow direction and water column above the top of the reactor core. Enough safety margins to ONB, DNB and OFI must-emphasized. A heat transfer package is used for calculating convection heat transfer coefficient in single phase turbulent, transition and laminar regimes. The main objective of this paper is to study the possibility of power upgrading of WWR-S research reactor from 2 to 10 MW_th. This study presents a one-dimensional mathematical model (axial direction) for steady-state thermal-hydraulic design and analysis of the upgraded WWR-S reactor in which two types of plate fuel elements are employed. FOR-CONV computer program is developed for the needs of the power upgrading of WWR-S reactor up to 10 MW_th.

• E2M - 전기 전자와 첨단 소재
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• 제8권3호
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• pp.291-297
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• 1995

The InP crystals have been grown by modified synthesis solute diffusion (SSD) method and its properties have been investigated. The crystals have been grown by lowering the crucible quartz for growth in the furnace and crystal growth rate is 1.8mm/day. The lattice constant a. of the grown crystals is 5.867.angs.. Etch pits density along growth direction of crystal changes from 3.0*10.sup 3/cm$\^$-2/ of first freeze part to 6.7*10$\^$4/cm$\^$-2/ of last freeze part and the radial direction of wafer shows nearly uniform distribution. The resistivity and the carrier concentration of the grown crystals are 1.43*10$\^$-1/.ohm.-cm, 7.7*10$\^$15/cm$\^$-3/ at room temperature, respectively. In the photolurninescence at 10K, the radiation transitions are observed by the near band edge recombination, a pair recombination due to Si donor - Zn acceptor and its phonon replica in the InP. The activation energy by Zn diffusion in undoped n-InP crystals is 1.22eV.

• 임산에너지
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• 제18권1호
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• pp.1-5
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• 1999

잦나무 조림목의 유용한 이용과 적합한 용도개발을 위한 수간내 재질변동을 조사하였다. 수고방향(수고 약 20m중 0.3, 1.3, 2.3, 5.3m부위)의 가도관장, 가도관폭, 마이크로피크릴경사각, 압축강도를 측정하고, 그들의 변동에 관하여 Duncan의 다중검정법에 의하여 조사하였다. 그 결과 가도관장, 가도관폭 및 압축강도는 대체로 유의차를 보이지 않았으나 마이크로피브릴경각은 유의차를 나타냈다. 그러나 마이크로피브릴경각은 수고에 따라 높아지거나 또는 낮아지는 등 일정한 경향을 보이지는 않았다.

• 대한기계학회논문집B
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• 제20권9호
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• pp.2933-2943
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• 1996

A grating composed of elliptical cylinders (GEC), specially designed, is applicable to control of radiation heat transfer from a heated surface, as reported in our previous work. In this study, an analysis of radiation heat transfer is performed for a physical model in which the GEC is placed in front of a heated black-base surface and the major axes of the elliptical cylinders are inclined as a certain angle from the normal to the row of elliptical cylinders. Numerical solutions are obtained. Variations of the direction and the radiative energy concentration with slant angle of the major axis are shown for some parameters. It is verified that the GEC is able to widely change the direction of radiation heat transfer from the heated surface.

• 대한안전경영과학회지
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• 제16권3호
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• pp.443-450
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• 2014

The industrial accident rate has been steadily decreased by making all efforts for the prevention of accidents after enacting Occupational Health and Safety Act in 1981. However, ordinary typed industrial accidents still occur in small and medium sized enterprises(SME). Timely Technical Guidance(TTG) project of Korea Occupational Safety & Heath Agency(KOSHA) for SME's was initiated to visit and provide the analysis and control of industrial accidents by the staffs of KOSHA as soon as possible after accidents occurred. This study is conducted to analyze the questionnaire survey for employers, workers and TTG personnel of KOSHA with being evaluated positively whether the demonstration project of TTG has been executed consistently. However, it is suggested that the understanding of TTG project and legal support are necessary for the establishments, and the development of a variety data and lots of available contents is necessary to increase satisfaction of the TTG project. The accident rate of SME's which are employed less than 50 workers is expected to be largely decreased with applying the control and improvement over this study with maintaining and developing TTG technology.