• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.853-861
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• 2015

In this study, FDM modelling with axisymmetry condition and interface element was verified whether it is reasonable to estimate compositive behavior of a piled raft foundation. To this end, the modelling validity of piled raft foundations was estimated by comparing and analyzing numerical analysis results and laboratory model test results. Also, load bearing ratio of a raft is analyzed by performing sensitivity analysis of foundation parameters with the actual field conditions. As a result of this study, correlation between bearing capacity and vertical displacement of numerical results turned out to be similar with that of a laboratory model test. In addition, ultimate bearing capacity of piled rafts and load bearing ratio of the raft is calculated to be similar in both cases. The load bearing ratio of the raft was also estimated to be in the range of 33% to 52% from the sensitivity analysis. The results were confirmed to be similar to the previous studies. Therefore, it can be inferred that piled rafts can be effectively modelled applying axisymmetry condition and interface element.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.47.2-47.2
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• 2013

We have performed a set of high-resolution simulations of nuclear star-forming ring that results in an inward gas migration from the galactic disk. Our simulations consider gas heating/cooling, star formation, and supernova feedback. The galactic potential was obtained from a snapshot of a 6.3 million particle simulation of a galactic disk at 1 Gyr, which manifests spiral arms and pseudo-bulge. The potential was modeled with a combination of 3-dimensional spherical (for the pseudo-bulge) and 2-dimensional cylindrical (for the disk) multipole expansion technique. With such a potential model, one can easily set up various realistic 3-dimensional potential models by slightly changing the expansion coefficients. We have performed a set of simulations with a few million gas particles covering the central ~6 kpc of the disk for different pseudo-bulge sizes and non-axisymmetry, and we report the dependence of the gas inflow rate, size of the star-forming ring, and star-formation rate in the ring on the size and strength of the non-axisymmetry in the bulge.

• Bulletin of the Korean Mathematical Society
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• v.58 no.3
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• pp.729-744
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• 2021

In this paper we prove global existence and uniqueness of axisymmetric strong solutions for the three dimensional electro-hydrodynamic model based on the coupled Navier-Stokes-Poisson-Nernst-Planck system in the exterior of a cylinder. The key ingredient is that we use the axisymmetry of functions to derive the L^p interpolation inequalities, which allows us to establish all kinds of a priori estimates for the velocity field and charged particles via several cancellation laws.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.769-774
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• 2013

Turbine blades and disc, which are one of the most important rotating parts of a gas turbine engine, are required to have highly efficient performance in order to minimize the total life cycle costs. Owing to these requirements, these components are exposed to severe conditions such as extreme turbine inlet temperatures, high compression ratios, and high speeds. To evaluate the structural integrity of a turbine disc under these conditions, material modeling and finite element analysis techniques are essential; furthermore, shape optimization is necessary for determining the optimal solution. This study aims to generate 2D finite element models of an axisymmetry model and a sector one and to perform thermal-structural coupled-field analysis and contact analysis. Structurally vulnerable areas such as the disc bore and disc-blade interface region are analyzed by a parametric study. Finally, an improved design is provided based on the results, and the necessity of elaborate shape optimization is confirmed.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.213-224
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• 2008

The pumping of coolant in a liquid metal fast reactor may be performed with an annular linear induction electro-magnetic (EM) pump. Linear induction pumps use a traveling magnetic field wave created by poly-phase currents, and the induced currents and their associated magnetic field generate a Lorentz force, whose effect can be the pumping of the liquid metal. The flow behaviors in the pump are very complex, including a time-varying Lorentz force and pressure pulsation, because an induction EM pump has time-varying magnetic fields and the induced convective currents that originate from the flow of the liquid metal. These phenomena lead to an instability problem in the pump arising from the changes of the generated Lorentz forces along the pump's geometry. Therefore, a magneto-hydro-dynamics (MHD) analysis is required for the design and operation of a linear induction EM pump. We have developed a time-harmonic 2-dimensional axisymmetry MHD analysis method based on the Maxwell equations. This paper describes the analysis and numerical method for obtaining solutions for some MHD parameters in an induction EM pump. Experimental test results obtained from an induction EM pump of CLIP-150 at the STC "Sintez," D.V. Efremov Institute of Electro-physical Apparatus in St. Petersburg were used to validate the method. In addition, we investigated some characteristics of a linear induction EM pump, such as the effect of the convective current and the double supply frequency (DSF) pressure pulsation. This simple model overestimated the convective eddy current generated from the sodium flow in the pump channel; however, it had a similar tendency for the measured data of the pump performance through a comparison with the experimental data. Considering its simplicity, it could be a base model for designing an EM pump and for evaluating the MHD flow in an EM pump.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.194-200
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• 2000

The sealing performance of an elastomeric O-ring seal using NBR and FFKM has been analyzed for the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry(grooved), are investigated using the finite element method. The analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to materials of NBR and FFKM and temperature of vaccum chamber.

• Tribology and Lubricants
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• v.19 no.1
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• pp.9-14
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• 2003

The sealing performance of an elastomeric O-ring using the double layered material has been analyzed fer the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring will occur when the pressure differential across the seal Just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of dovetail grooved geometry, are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to the ratio of diameter between the inner ring and the outer ring, and the temperature of vacuum chamber.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.349-356
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• 1986

For the extension of application in flash method measuring the thermophysical properties of materials, the heat diffusion equation with the heat transfer loss from front, rear, and circumferential surfaces of two layer cylinderical sample is mathematically analyzed by means of Green's function for axially symmetric pulse heating on the front of samples. The solutions are applied to determine the unknown thermal diffusivity of the two materials and analyzed the measurement error due to heat loss and finite pulse time effects.

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.119-126
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• 2009

A numerical analysis is performed to investigate the effect of rotation on the blood flow characteristics with four different angular velocities. The artery has a cylindrical shape with 50% stenosis rate symmetrically distributed at the middle. Blood flow is considered a non-Newtonian fluid. Using the Carreau model, we apply the pulsatile velocity profile at the inlet boundary. The period of the heart beat is one second. In comparison with no-rotation case, the flow recirculation zone (FRZ) contracts and its duration is reduced in axially rotating artery. Also wall shear stress is larger after the FRZ disappears. Although the geometry of artery is axisymmetry, the spiral wave and asymmetric flow occur clearly at the small rotation rate. It is caused that the flow is influenced by the effects of the rotation and the stenosis at same time.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.113-124
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• 1984

The dynamic response of vertically axisymmetric floating bodies is numerically calculated with corrections of Fenton's coefficient matrix. The computational effort required is considerably reduced due to axisymmetry of the bodies. Comparisons are made with the results of Hoffman's model tests of the discus buoy. In the near future, this study will be applied to calculate the dynamic response of large scale structures, located in the deep sea, i.e., tension leg platforms.