• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.458-465
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• 2003

The main objective of the research is to develop a research code solving transient incompressible Navier-Stokes equation. In this research code, Adams-Bashforth method was applied to the convective terms of the navier stokes equation and the splitted equations were discretized spatially by finite element methods to solve the complex geometry problems easily. To reduce the divergence on the boundaries of pressure poisson equation due to the unsuitable pressure boundary conditions, multi step approximation pressure boundary conditions derived from the boundary linear momentum equations were used. Simulations of Lid Driven Flow and Flow over Cylinder were conducted to prove the accuracy by means of the comparison with results of the previous workers.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.107-109
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• 2003

전력계통의 과도 안정도 해석의 접근방법에는 SI(Simultaneous Implicit)법과 PE(Partitioned Explicit)법 두 가지방법을 사용해오고 있다. SI법에는 Trapezoidal법 등이 있고, PE법에는 Runge-Kutta법, Euler법등이 사용되고 있다. SI법인 Trapezoidal법은 PE법의 Runge-Kutta법 또는 Euler법에 비해 시간간격을 크게 해서 계산속도를 줄일 수 있다는 장점이 있지만, 정화도면에서는 신뢰한 수 없는 단점이 있다. 이 논문에서는 포물선 사법을 이용하여 Trapezoidal법의 정확도를 개선학 수 있는 방법을 제시하고 명확한 수학적 증명을 통해 타당성을 보여준다. 연속함수와 불연속함수에 대해서 Runge-Kutta법과 Trapezoidal법과 제안한 방법을 적용시켜서 제안한 방법의 정화함을 보여준다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.661-669
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• 1999

이 논문은 탄성지반위에 놓인 원호형 곡선보의 자유진동에 관한 연구이다. 회전관성 및 전단변형을 고려하여 두 개의 매개변수로 표현되는 탄성지반위에 놓인 원호형 곡선보의 자유진동을 지배하는 미분방정식을 유도하고, 이를 수치적분기법과 시행착오적 행렬값탐사법이 결합된 수치해석기법으로 해석하였다. 회전-회전, 회전-고정 및 고정-고정의 단부조건을 갖는 곡선보의 최저차모드 3개의 고유진동수를 산출하였다. 곡선보의 수평높이 지간길이비, Winkler 지반계수, 전단지반계수에 따른 고유진동수 변화를 분석하였으며, 회전관성 및 전단변형의 영향을 고찰하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.274-277
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• 2012

Large eddy simulation is applied to the turbulent flow and heat transfer in straight cooling passages with varying aspect ratio. The turbulent statistics of the flow and thermal quantities are calculated and the characteristics of Nusselt number are investigated. To scrutinize near-wall streamwise vortices, a conditional sampling technique is adopted. Clockwise and counter-clockwise rotating streamwise vortices are sampled and the probability density function of the vortex circulation Reynolds number and wall Nusselt number are calculated.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.103-114
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• 1992

A study result of buckling reliability is presented for the axially compressed imperfect elastic cylinder. Multi-mode analysis program is developed from Karman-Donnell Equation for the calculation of the buckling load of the cylindrical she1l. Geometric intial imperfection is approximated by double Fourier series of which coefficients are assumed random variables with jointly normal distribution characteristics. Crude Monte Carlo simulation technique is used to calculate the probabilistic failure properties of several cases with various imperfection Conditions.

• The Korean Journal of Air & Space Law and Policy
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• v.33 no.2
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• pp.267-290
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• 2018

This paper reviews and criticizes the EU Case of C-452/13, Germanwings GmbH v. Ronny Henning. Under this case, Ronny Henning later sued Lufthansa's budget carrier Germanwings after it refused to pay him 250 euros compensation for a delay he said totalled more than three hours. Germanwings, however, maintained his flight had arrived only two hours and 58 minutes behind schedule. In those circumstances, the following question to the European Court of Justice (ECJ) for a preliminary ruling: What time is relevant for the term time of arrival used in Articles 2, 5 and 7 of Regulation [No 261/2004]: (a) the time that the aircraft lands on the runway (touchdown); (b) the time that the aircraft reaches its parking position and the parking brakes are engaged or the chocks have been applied (in-block time); (c) the time that the aircraft door is opened; (d) a time defined by the parties in the context of party autonomy? ECJ says that the situation of passengers on a flight does not change substantially when their aircraft touches down on the runway at the destination airport, when that aircraft reaches its parking position and the parking brakes are engaged or when the chocks are applied, as the passengers continue to be subject, in the enclosed space in which they are sitting, to various constraints. Therefore, it is only when the passengers are permitted to leave the aircraft and the order is given to that effect to open the doors of the aircraft that the passengers may in principle resume their normal activities without being subject to those constraints. ECJ rules that it is apparent that Articles 2, 5 and 7 of Regulation No 261/2004 must be interpreted as meaning that the concept of 'arrival time', which is used to determine the length of the delay to which passengers on a flight have been subject, corresponds to the time at which at least one of the doors of the aircraft is opened, the assumption being that, at that moment, the passengers are permitted to leave the aircraft.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.142-150
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• 2003

Turbulent flows and related heat transfer in a square heated duct is investigated by a turbulence model and a large eddy simulation. The cooling channel of calorimeter is modeled to the square duct. The nonlinear k-ε-fμ model of Park et al. [3] is slightly modified and their explicit heat flux model is employed. The Reynolds number is varied in the range 4000≤Reｂ≤20000. The heat transfer is closely linked to the secondary flows which driven by the turbulent motion. Its magnitude is 1~3% of the mean streamwise velocity. The relation of Nu~Re0.8Pr0.34 is validated by comparing with the predicted Nu of k-ε-fμ model. Finally, the coherent structures and thermal fluctuations are scrutinized.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1358-1363
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• 2012

This paper deals with the analysis of high efficiency small antenna like superconductor antenna. The superconductor antenna is useful to low frequency range because surface resistance of superconductor increased with the rate of square of frequency. Thus, the used antenna increases in size. For such a reason, the role of the matching circuit is very important in small antenna. In this paper, low loss antenna included the optimal structure of matching circuit is analyzed by using quasi-static approximation. To verify the results of this paper, input impedance and radiation characteristics of this antenna have been evaluated.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.1-8
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• 2020

The aeroservoelastic analysis that deals with the interactions of the inertial, elastic, and aerodynamic forces and the influence of the control system have been performed. MSC Nastran was used for the free vibration analysis of the structure model as the pre-analysis. ZAERO was used to calculate the unsteady aerodynamic forces. The unsteady aerodynamic forces were verified by comparing with Doublet Hybrid Method. Karpel's Minimum-State Approximation method was used for approximation of the aerodynamic forces to the Laplace domain in the frequency domain. The aeroservoelastic state-space equation was obtained by combining the aeroelastic equation with the actuator dynamics. The analysis of aeroservoelastic stability concerning the elevator input of the high aspect ratio model was performed. The root-locus method and time-integration method were used for the analysis of aeroservoelastic in frequency and time domain.

• Tunnel and Underground Space
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• v.12 no.1
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• pp.31-36
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• 2002

This paper concerns smoke propagation in tunnel fires with various size of fire source. Experiments carried out in model tunnel and those results were compared with numerical results. The Froude scaling law was used to scale model tests for comparison with larger scale tests. In order to validate for numerical analysis, temperature distribution of predicted data was compared with measured data. Examining the temperature distribution, we found that smoke layer does not come down under 50% of tunnel heights for a short tunnel heights for a short tunnel firs without ventilation. Front velocity of smoke layer is proportional to the cube root of heat release rate. And it is in good agreement with existing empirical expression and numerical prediction. In a short tunnel fire, horizontal propagation of smoke layer is more important than vertical smoke movement for evacuation plan.