• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.24-30
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• 2006

Integrated cavity output spectroscopy(ICOS) is a simple, non-intrusive absorption measurement technique that can detect and quantify trace-level gas species. The spectral absorbance of a gas is quantified from the integrated optical output of the modulated high-finesse cavity containing the sample which is irradiated by a wavelength-swept laser source. We constructed an experimental setup by using a tunable single mode external cavity diode laser operating at the wavelength near 765 nm and a Fabry-Perot cavity with length modulation achieved by a piezoelectric transducer where one of the cavity mirrors sat on. In the experiment performed on minute oxygen gas at the wave-length near 764.5nm, we demonstrated the minimum detectable absorption of $8.45\times10^{-8}cm^{-1}$.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.44-49
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• 1997

액체금속로용 2차원적 연소 해석 코드 REBUS-2[1]에 횡방향 적분법 및 다항식 전개법에 기초한 3차원적 육방형 노달 방법을 결합하여, 3차원적 연소 해석 코드 REBUS-K를 개발하였다. REBUS-K는 3차원적 중성자속 분포 계산 및 미시적 연소 계산을 통해 노내 연소 해석을 수행하며, 또한 핵연료 방출/재배치 및 재장전, 재처리, 성형가공 등의 노외 주기 계산을 수행한다. 비평형주기 및 평형주기 해석을 수행하며, 평형주기 해석 시에는 지정된 제한 연소도 및 증배계수를 만족시키는 주기 길이와 장전 농축도를 탐색한다. 개발된 코드의 검증 계산을 450 MWt 액체금속로의 비평형주기 및 평형주기 문제에 대하여 수행하였으며, 계산 결과를 Argonne 연구소의 3차원적 연소 해석 코드 REBUS-3[2]의 결과와 비교하였다. 그 결과 원자로 증배계수, 출력 분포, 증식율, 연소도, 장전 핵연료의 농축도, 주기 길이 등의 연소 특성이 수렴 조건 이내에서 일치하였다.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.201-211
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• 2016

A method for estimating rock joint size distribution using contained traces length distribution from 3D cylindrical window survey was suggested. To reduce the numerical error, an improved technique was applied. The accuracy was verified by referring to Monte-Carlo simulation and it was found that the error can be decreased with suitable gamma values.

• Computational Structural Engineering
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• v.10 no.4
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• pp.177-184
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• 1997

In this paper, numerical methods are developed for solving the elastica of simple beams with variable-arc-length subjected to a point loading. The beam model is based on Bernoulli-Euler beam theory. The Runge-Kutta and Regula-Falsi methods, respectively, are used to solve the governing differential equations and to compute the beam's rotation at the left end of the beams. Extensive numerical results of the elastica responses, including deflected shapes, rotations of cross-section and bending moments, are presented in non-dimensional forms. The possible maximum values of the end rotation, deflection and bending moment are determined by analyzing the numerical data obtained in this study.

• Computational Structural Engineering
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• v.9 no.4
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• pp.189-198
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• 1996

The fracture behaviour of concrete gravity dam mainly due to uplift pressure acting at the crack face was studied. Triangular type and parabolic type distribution of the uplift pressure including uniform type were first considered in case of calculating stress intensity factor(SIF) by the surface integral method. Second, the directions of crack propagation according to the uplift pressure distribution were pursued by FRANC(FRacture ANalysis Code). Third, critical crack lengths according to the uplift pressure distribution under the overflow depth were calculated. The SIF values obtained from the surface integral method were compared with those by FRANC and relatively good agrements could be obtained between both of them. And it could be seen that the direction of crack propagation in case of triangular pressure distribution was a little benter to the dam base than the one by the uniform type. Maximum critical crack lengths under the overflow depth were obtained at about 2/5-1/2 of the dam height.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.1-8
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• 2023

Power transmission shafts in rotary wing aircraft use a hollow shaft to reduce weight. We can apply linear elastic fracture mechanics to predict crack propagation behavior. This paper predicted crack growth life of a hollow shaft with a circumferential through-type crack by finite element analysis. A 2D finite element model was created by applying a torsion and forming elements considering cracks. We defined the initial crack length and performed the finite element analysis by increasing the crack length to derive stress intensity factor at crack tips. We defined the length just prior to the stress intensity factor exceeding the fracture toughness as the crack limit length. We calculated the crack limit length using a handbook and numerically integrated the crack growth rate equation to derive growth life of each crack. The growth life of each crack was compared to verify the proposed finite element analysis method.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.759-764
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• 2001

Heat (mass) transfer characteristics have been investigated on the endwall of a large-scale linear turbine cascade passage under a combustor-level high free-stream turbulence with a large length scale. Local heat (mass) transfer coefficients are measured by using the naphthalene sublimation technique. The result shows that local heat (mass) transfer on the endwall is greatly enhanced in the central region of the turbine passage, but there is no noticeable change in the local heat (mass) transfer in the region suffering severe heat load. Under the high free-stream turbulence, the local heat (mass) transfer coefficient shows more uniform distribution and its average value across the whole endwall region is increased by 26% of that at low turbulence condition. The heat (mass) transfer data on the endwall strongly supports that well-organized vortices near the endwall tends to suffer an suppression by the high free-stream turbulence.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1600-1606
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• 2001

Resonant frequency in rectangular microstrip patch antenna on anisotropic substrates with airgap and superstrate are analyzed. Dyadic Green function is derived for selected anisotropic material by constitutive relation. From these results, integral equations of electric fields are formulated using Fourier transform in space region. The electric field integral equations are discretized into the matrix form by applying Galerkin\`s moment method. Sinusoidal functions are selected as basis functions because they resemble in the actual standing wave on the patch. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the resonant frequency in the variation of air gap, patch length and anisotropy ratio are presented and analysed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.982-988
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• 2005

An analytic solution of circular aperture antenna with a feed transition is presented using a hybrid method of generalized scattering matrices and integral transform. The method can give an analytic solution to antennas with integrated filters or mode converters, etc. Scattering matrices and integral transform techniques are combined to accommodate discontinuities connected between an aperture and a feed waveguide, and radiated field from the aperture. The method gives radiation fields as well as return losses of the antenna.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2423-2430
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• 1994

Several factors of the efficient combustion process are shape of combustion chamber, position of spark plug, turbulence flow and so on. the shape of combustion chamber and position of spark plug are constrained to geometrically, and then it could not make a change the shape easily. But the turlence flow in combustion chamber have a great influence on combustion phenomena, and which is much easier to control relatively. And since characteristics of turbulence flow would be very important to the stability of combustion and performances, This study is also essential to future engine-low emission and lean burn engine. This paper shows that the visualization of the turbulence flow of single cylinder engine by using 2way, $45^{\circ}$ inclined and 2 channel hot wire probe through the park plug hole. We also study the characteristics of turbulence flow by means of ensemble averaged mean velocity, turvulence intensity and integral length scale.