• Fire Science and Engineering
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• v.17 no.3
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• pp.50-54
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• 2003

The backlayer phenomena of smoke in the road tunnel is evaluated through numerical experiments. A commercial code, PHOENICS is used to simulate smoke flow in the road tunnel. The independent and dependent variables are ventilation air velocity and the length of backlayer of smoke respectively. Hybrid scheme and $textsc{k}-\varepsilon$ turbulence model is adopted in the simulation process and mass residual is used as a convergence criterion. The experimental results say that the length of backlayer is reduced linearly with the increase of ventilating air velocity and that there is a critical air velocity which prevents from the onset of backlayering phenomena. One finds that there is a fresh air region near the bottom of tunnel which could make the passenger escape from the region polluted by smoke. These phenomena come from the severe vertical stratification of the smoke air mixture in the tunnel.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.381-388
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• 2000

The temperature and velocity fluctuations occurred by the baroclinic instability in the melt for Czochralski crystal growth method were experimentally investigated. Wood's metal, which has similar Pr number to the silicon melt, was used as the working fluid and azimuthal velocity was measured using incorporated magnet probe. The azimuthal velocities near the free surface are faster than velocities near the bottom and the rotational velocities near the model crystal become very fast. The results of measured temperature fluctuation as increasing rotation rate were shown that baroclinic instability occurred at the region of Ro<1.01, Ta>$9.63{\times}10^8$. In these region, the fluctuations of temperature and velocity have the same frequency.

• Composites Research
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• v.22 no.1
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• pp.1-8
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• 2009

In this paper low-velocity impact response and damage of composite laminates is analytically investigated. A modified displacement field of plate considering initially loaded in-plane strain is proposed. From the displacement field a finite element equation on structural behavior of composite laminate is newly induced and a computational program is coded. Numerical results using the FEM code is compared with the numerical ones from reference. Additional numerical analysis is performed on another impact condition and effect of initial in-plane load is reviewed. Potential delamination damage area in the first inter-ply surface from bottom of laminate is approximated and effect of initial in-plane load and impact condition is also reviewed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.63-71
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• 1992

A solution method is developed for computing the bed shear stress driven by combined wave and current flow on a natural mobile coastal beach. An empirical equation is introduced to determine the shape of ripples formed on the natural sandy beach. The model being based on the Prandtl's mixing length theory, the effect of arbitrarily-angled interaction is included in the estimation of current velocity reduction and all numerical integrations are expressed by explicit approximate equations to improve the computation speed. In addition the computed sediment transport rates were compared with the measured values reported in literature. using the refined bottom friction model considering the ripple formation.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.471-476
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• 2001

The characteristics of conjugated heat transfer in the inclined channel was experimentally investigated. The simulated module is attached to the bottom of the inclined channel and is heated with constant heat flux. The experimental parameters of this study are input power (Q = 3, 7W), inlet air velocity ($V_{i}=0.1{\sim}0.9m/s$) and inclined channel angle (${\varphi}=0{\sim}90^{\circ}$). The results show that input power was most effective parameter on the temperature differences between module and air. As the inclined channel angle increases, the temperatures of the module are increased. And we obtained the best condition on the conductive board when ${\varphi}=0^{\circ}$.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.144-150
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• 2000

In this paper, the formation of a corner cavity in the final stage of axisymmetric backward extrusion process is studied by means of upper bound analysis using kinematically admissible velocity. The quantitative relationships between corner cavity formation and process parameters are studied. And analytical results are compared with those of experiment to which plasticine is used. It is found that the analytical results agree well with experimental one. In addition, to restrict the formation of a corner cavity, driven container is applied to backward extrusion and the results are compared with those of FEM. The critical thickness of the bottom of the billet decreases with increase in reduction of area, and increases with decrease in friction. To prevent the formation of corner cavity, the concept of moving container was applied. Throughout this process, the occurrence of a corner cavity is delayed and forming limit area is enlarged.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.1-7
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• 2003

A common feature in the three-dimensional numerical model experiments of coastal discharge with simplifed model and idealized external forcings is investigated. The velocity fields due to the buoyancy and flow flux, are spreaded radiately and the surface velocites are much greater than homegeneous discharges. The coastal dischargd due to the Coriolis force and flow flux are shaped a anticyclical gyre (clockwise) and determined the scale of the gyre in the coastal zone, respectively. The bottom topography restricts a outward extention of the coastal fronts and it accelerates a southward flow.

• 한국해양학회지
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• v.9 no.2
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• pp.10-18
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• 1974

The cold water mass around the southeast coast of the Korean Peninsula is analyzed by using CSK data from 1966 through 1970. It is shown that this water mass flows down from the region offshore of Jukbyun to the area of Youngil Bay along the 100meter contour line of bottom topography. In ordinary summer conditions when the current velocity in the Korea Strait is usually above about 50cm/sec and the wind direction is southwest, the cold water ascends to the surface and makes the surface temperature gradient large, unless disturbed by a tropical cyclon. The bottom water of the Korea Strait is formed by the stratification after the Tsushima intermediate water and the Japan Sea intermediate water have been mixed. In winter the Tsushima intermediate water with high salinity sinks rapidly around the inlet of the Japan Sea and prevents the Japan Sea intemediate water from entering the Korea Strait.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.13-20
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• 1997

A fundamental study for the numerical scheme to simulate unsteady nonlinear waves by solving Euler equations is presented. First a conservation form and a non-conservation form of the Euler equations with a free surface fitted coordinate system are compared. Next, a time splitting fractional step method and an alternating direction implicit(ADI) method for the time integration are compared. For the comparative study, flow calculations around a bottom bump in a channel and a NACA 0012 hydrofoil in a flume are performed. The results show that the ADI method with a third order upwind differencing scheme is very efficient in reducing the computing time with keeping the accuracy, And, there is no distinct difference between two expression forms except that the non-conservative form shows faster wave propagating velocity than the conservation form. Some results are compared with experiments and show good agreement.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.449-454
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• 2003

The accurate mapping of the basement is one of the most crucial factors in construction of harbour facilities and bridges in the coastal areas. In shallow waters, the seismic reflection method often fails to image the basement geometry beneath the sediment cover in many cases. We present the result of a shallow marine seismic refraction survey using two ships, l2-channel hydrophone arrays deployed on the bottom and a borehole sparker or percussion powder as sources. Velocity structure could be computed by tomography algorithm since more than 6 different source points had been applied for one spread. The comparison of the results of the refraction survey with drilling logs demonstrates remarkable consistency in basement geometry. It thus appears that the refraction method in this study is an efficient and cost-effective way to investigate the basement structure in coastal area, river, and lake.