• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.06a
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• pp.107-114
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• 2000

Marine analysis was made to investigate the hydrodynamic effects of a Wing in Ground (WIG) by means of finite difference techniques. The air flow field around WIG is analyzed by the Marker & Cell (MAC) based method, and the interaction between WIG and the free surface are studied by showing pressure distributions above the free surface. In the latter part, computations are extended to make clear the flow characteristics of a high speed catamaran in the rang of Froude numbers 0.2 to 1.0 with a separation to length ratios of 0.2, 0.3 and 0.5. The Navier-Stokes solver is invoked in which the nonlinear free-surface boundary condition is applied. For the validation, computational results are compared with the experiments.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.175-176
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• 2011

Applying previous studies performed in the moisture transportation characteristics and shrinkage of lightweight concrete application of shrinkage reduction is to discuss. Applicability of shrinkage reduction effect of lightweight concrete applies for the analysis of PSC girder bridge beam placed on the construction site. Stress of the concrete bridge deck, rebar quantity is calculated by effective elastic modulus method and crack risk is assessed by moisture transport and differential shrinkage analysis. After approximately 10 days maximum tensile stress occurs 6MPa, similar to the case of normal concrete, a maximum tensile stress occurs 3MPa in lightweight concrete and comparing to normal concrete stress was reduced to approximately 50%. Normal and lightweight concrete crack index, respectively, is reduced 1.6 to 1.2, 1.2 to 0.9 in surface and boundary region. Therefore, reduction in shrinkage of concrete were able to confirm reduction of crack risk.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.109-114
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• 2002

Aging stabilities of the operating frequency of piezoelectric devices such as filter, oscillator and discriminator are very important. In this study it was studied aging stabilities of the length-extensional vibration mode of Pb(Zr$\_$y/Ti$\_$1-y/)O$_3$+x[wt%]Cr$_2$O$_3$ ceramics. PZT ceramics in Morphotropic phase boundary have higher aging rates of k$\_$31/ and resonant frequency than those in tetragonal phase or rhombohedral phase. Thermal aging moves the composition with maximum aging rate to Zr-rich side in Cr not added PZT system. Aging rate of resonant frequency of the ceramics with x=0.1, y=0.53 and x=0.3, y=0.53 increased by thermal aging.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1384-1386
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• 2001

In this paper, the structural and electrical properties of the $Sr_{1-x}Ca_xTiO_3$($0{\leq}x{\leq}0.2$)-based grain boundary layer ceramics were investigated by X-ray, SEM and V-I system. Increasing content of Ca, the average gram size and the lattice constant were decreased. The relative density of all specimens was > 96%. The 2nd phase formed by thermal diffusing from the surface lead to a very excellent electrical properties, that is, ${\varepsilon}_r$ > 50000, tan${\delta}$ < 0.05, $\Delta$C < ${\pm}$ 10%.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.140-145
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• 2000

The spectral method which is composed of an eigenfunction expansion of free modes in the wave number domain is used to produce two dimensional unsteady inviscid wave simulation such as progressive waves in a numerical pneumatic wave tank. A spatial and time dependent free surface elevation and the potential are calculated by integrating ODE derived from fully nonlinear kinematic and dynamic free surface boundary condition at each time step. The nonlinear characteristics in the waves by this method were notable as increasing wave steepness. This method is very useful and powerful in terms of saving computational time caused by rapid convergence exponentially with increasing number of nodes, even preserving accurate numerical results. Moreover, it will given us many possibilities to apply to naval and ocean engineering fields.

• Journal of Ocean Engineering and Technology
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• v.9 no.1
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• pp.22-35
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• 1995

A simplified numerical procedure have proposed to trace the dynamic behaviour of offshore tubulars subjected to lateral collision impacts. The local denting and overall bending deformation of the struck tubular are represented by a non-linear spring and an elastic visco-plastic beam respectively. In this method a temporal finite difference method and a spacial finite element method are employed. Using this method various boundary conditions are able to considered and their effects on the extent of damage can be quantified. The extent of damage due to collision can be obtained as results of the dynamic analysis. The predictions using the proposed method have been correlated with existing test results and then the reliability of the procedure has been substantiated. The characteristics of the dynamic response of tubulars under lateral impacts are compared for simply supported roller and fixed end conditions and their effects on the extent of damage are specfied.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.222-224
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• 2009

This paper presents an algorithm that extracts road lane's specific information by using HSI color information and performance enhancement of lane detection base on vision processing of drive assist. As a preprocessing for high speed lane detection, the optimal extraction of region of interest for lane boundary(ROI-LB) can be processed to reduction of detection region in which high speed processing is enabled and it also increases reliabilities by deleting edges those are misrecognized. Road lane is extracted with simultaneous processing of noise reduction and edge enhancement using the Laplacian filter, the reliability of feature extraction can be increased for various road lane patterns. Since noise can be removed by using saturation and brightness of HSI color model. Also it searches for the road lane's color information and extracts characteristics. The real road experimental results are presented to evaluate the effectiveness of the proposed method.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.101-108
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• 2000

Through numerical experiment using simplified OSU-1D PBL(Oregon State University One-Dimensional Planetary Boundary Layer) model and field measurement, we studied the impacts of vegetation canopy on heat island that was one of the characteristics of local climaate in urban area. it was found that if the fraction of vegetation was extended by 10 percent, the maximum air temperature and the maximum ground temperature can come down about 0.9${\circ}C$, 2.3${\circ}C$, respectively. Even though the field measurement was done under a little unstable atmospheric condition, the canopy air temperature was lower in the daytime, and higher at night than the air and ground temperature. This result suggests that the extention of vegetation canopy can bring about more pleasant local climate by causing the oasis, the shade and the blanket effect.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.76-80
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• 2001

Unsteady compressible Euler equation is solved and the high-order, high-resolution numerical solver, physical boundary condition, adaptive nonlinear artificial dissipation model and conformal mapping are applied to computation of steady transonic flow and unsteady acoustics. The acoustic characteristics of axi-symmetric duct and two dimensional straight/S channel are studied and the computation results shows good agreements with linear analysis. In transonic case, local time stepping and canceling-the-residual techniques are used for convergence acceleration. The aspect of flow and acoustics in S-channel and the Pattern of noise radiation is changed by inflow Mach no. and static pressure at fan-face.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.391-394
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• 2006

In this paper, the thermal lattice Boltzmann method(TLBM) proposed by Guo et al.(2002) is applied to analyze the forced convective flow and heat transfer of 2-D micro channel. Nonequilibrium extrapolation boundary condition is adopted to simulate the velocity and temperature behavior at wall boundaries. Numerical results obtained by the present study give a good prediction of the micro fluidic characteristics with thermal effects.