• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.231-235
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• 2002

A theoretical and experimental study on the combustion process in a constant volume micro combustor is described. Unlike in a macro scale constant volume combustor, the heat loss to the wall plays a major role in flame propagation in a micro micro combustor. In order to analyze the effect of heat loss on combustion phenomena, pressure transition from ignition was measured. A number of cylindrical micro combustors with different diameter and depth were used for experiment to study the effect of length scales and shape factor. The diameter of combustor ranged from 7.5mm to 22.5 mm and the height of cylinder was from 1mm to 4mm. Initial pressure was also varied for the experiment. The diagnostic methods were severely limited due to the size of the apparatus and uncertainties of certain quantities to be measured in a small-scale environment. An analytical method to derive physical quantities that are essential for performance prediction from the pressure measurements is described.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.29-36
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• 2003

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of inhomogeneous charge methane-air mixture under several parameters. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to beneath 0.05m/s gradually at 3 seconds. Second mixture is accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the burn rate.

• 한국전산구조공학회논문집
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• 제12권3호
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• pp.475-484
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• 1999

압력절점은 요소의 균등한 압력증분을 1개의 자유도로 갖는 절점이며, 유한요소의 하중-변위 평형방정식에 체적과 압력의 관계를 추가하여 한계압력 이후에서도 체적변화에 따른 압력증분을 직접적으로 제저할 수 있는 절점이다. 본 연구에서는 철근콘크리트의 평면 구성 방정식과 적층정식화에 적용한 쉘 요소에 압력절점을 추가하고 해석시 체적을 제어함으로써 철근콘크리트 원통형 구조에 대해 파괴까지의 극한내압 능력을 해석할 수 있는 체적제어 비선형 해석기법을 개발하였다. 본 논문에서 제안한 해석기법을 이용하여 철근콘크리트 원통형 구조물에 대하여 비선형 해석을 수행하여 한계압력과 한계압력 이후의 구조물의 거동을 예측하였으며 실험결과와 비교 검증하였다.

• Computers and Concrete
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• 제8권3호
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• pp.357-369
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• 2011

In this study, effect of steel fibers on toughness and some mechanical properties of concrete were investigated. Hooked-end steel fibers were used in concrete samples with three volume fractions (${\nu}_f$) of 0.5%, 0.75% and 1% and for two aspect ratios (l/d) of 45 and 65. Compressive and flexural tensile strength and modulus of elasticity of concrete were determined for cylindrical, cubic and prismatic samples at the age of 7 and 28 days. The stress-strain curves of standard cylindrical specimens were studied to determine the effect of steel fibers on toughness of steel-fiber-reinforced concrete (SFRC). In addition, the relationship between compressive strength and the flexural tensile strength of SFRC were reported. Finally, a simple model was proposed to generate the stress-strain curves for SFRC based on strains corresponding to the peak compressive strength and 60% of peak compressive stress. The proposed model was shown to provide results in good correlation with the experimental results.

• 대한기계학회논문집
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• 제11권4호
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• pp.629-636
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• 1987

An experiment is carried out to study the surface-tension driven flow characteristics in a cylindrical liquid column heated from above (which is the low gravity floating zone simulated on earth) with varing the aspect ratio and diameter of the liquid column. Hexadecane, octadecane, silicon oil(10cs), FC-40 and water are used as the test liquids. The free surface shape varies sinusoidally for Ma>M $a_{cr}$ and its frequency is found to be the same as that of temperature oscillation. It is verified that the surface temperature profile changes from linear to S-shaped profile for Ma>M $a_{cr}$ . The frequency of temperature oscillation decreases with increasing liquid volume, while its level increases. M $a_{cr}$ decreases with increasing aspect ratio, and also decreases with increasing Prandtl number in the range of 25

• 한국공작기계학회논문집
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• 제10권1호
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• pp.65-70
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• 2001

The hear transfer mechanism initiating the friction welding is examined and a transient three dimensional heat conduc-tion model for the welding of two dissimilar cylindrical metal bars is investigated. The cylindrical metal bars are made of materials made of A2024 and SM 45C. Numerical simulations of heat flow are performed using the finite volume method. Respectively. Commercial FLUENT code is used in the heat flow simulation and maximum temperature and distribution of temperature are calculated. Temperature of friction welded joining face is compared with the temperature distribution measured by experiment and numerical simulation. The maximum temperature of friction welded joining face is lower than melting point of A2024-T6 aluminum alloy using insert metal. The temperature distribution of friction welded join- ing face with insert metal is more uniform than that of without inset metal.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1009-1014
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• 2001

A numerical investigation on nonlinear oscillations of gas in an axisymmetric resonant tube is presented. When a tube is oscillated at a resonant frequency, acoustic variables such as density, velocity, and pressure undergo very large perturbation, often described as nonlinear oscillation. In order to analyze these phenomena, axisymmetric 2-D nonlinear governing equations have been derived and solved numerically. Numerical simulations were accomplished for cylindrical, conical, and 1/2 cosine-shape tubes, which have same volume and length. For conical and 1/2 cosine-shape tubes, very large variation of pressures can be induced without shock formation except the cylindrical tube. In addition, the results well agree to those of 1-D simple model analysis.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1119-1125
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• 2009

The coupled fluid-structure interaction problem is analyzed using the theoretical method to investigate the coupled vibration characteristics of functionally graded material(FGM) cylindrical shells conveying an incompressible, inviscid fluid. Material properties are assumed to vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The steady flow of fluid is described by the classical potential flow theory. The motion of shell represented by the first order shear deformation theory(FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be taken into consideration by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with exiting results.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.81-90
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• 2004

A zonal embedded grid technique has been developed for computation of the two-dimensional Navier-Stokes equations with cylindrical coordinates. The fundamental idea of the zonal embedded grid technique is that the number of azimuthal grids can be made small near the origin of the coordinates so that the grid size is more uniformly distributed over the domain than with the conventional regular-grid system. The code developed using this technique combined with the explicit, finite-volume method was then applied to calculation of the spin-up flows within a semi-circular cylinder. It was shown that the numerical results were in good agreement with the experimental results both qualitatively and quantitatively.