• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.28-34
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• 2007

Recently, with the rapid growth of industry, environmental condition became worse. In addition to outdoor insulators in seashore are polluted due to salty wind. Also this pollution causes the flashover and failure of electric equipments. Especially the salt contaminant is one of the most representative pollutants, and known as the main source of the accident by contamination. As well known, the pollution has a close relation with meteorological factors such as wind velocity, wind direction, temperature, relative humidity, precipitation and so on. In this paper we have statistically analyzed the correlation between the pollution and the meteorological factors. The multiple regression analysis was used for the statistical analysis; daily measured equivalent salt deposit density(dependent variable) and the weather condition data(independent variable) were used. Also we have developed an expert program to predict the pollution deposit. A new prediction system using this program called SPPP(salt pollution prediction program) has been used to model accurately the relationship between ESDD with the meteorological factors.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.141-150
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• 2002

Numerical simulations based on the ALE finite element method are carried out to examine the aerodynamics of an oscillating circular cylinder when the separated shear flows around the cylinder are stimulated by periodic jet excitation with a shear layer instability frequency. The excitation is applied to the flows from two points on the cylinder surface. The numerical results showed that the excitation with a shear layer instability frequency can reduce the negative damping and thereby stabilize the aerodynamics of the oscillating cylinder. The change of the lift phase seems important in stabilizing the cylinder aerodynamics. The change of lift phase is caused by the merger of the vortices induced by the periodic excitation with a shear layer instability frequency, and the vortex merging comes from the high growth rate, the rapid increase of wave number and decrease of phase velocity for the periodic excitation in the separated shear flows.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.65.1-65.1
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• 2014

We present Palomar/SWIFT integral field spectroscopy of z~0.2 strong $H{\alpha}$ emitters identified in the Sloan Digital Sky Survey. The large Halpha equivalent widths as well as the huge specific star formation rates of these galaxies are comparable with that of z>4 Lyman break galaxies, thus understanding the gas kinematics and the distribution of massive stars in these systems will help to obtain a better understanding of high-redshift star forming environments and the growth of massive galaxies. We measure the velocity dispersion across the entire galaxy, estimate the number density and the spatial distribution of massive stars from the emission line morphologies. The role of minor mergers in powering star formation is investigated as an alternative to cold flow driven star formation.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.262-265
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• 2009

For the initially quiescent fluid layer, the principle of the exchange of stabilities for the Marangoni convection due to the impulsive temperature change is proven analytically. Under the linear stability theory, the temperature and vertical velocity disturbances are express as the liner combination of the orthogonal functions. It is shown that the growth rate of the temperature disturbance is the real function for all positive Marangoni numbers.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.204-210
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• 1998

A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength determined by the density difference between the burned and the unburned region. Volume expansion adjusts the flow field to accommodate the increased volume flow rate crossing the flame front. Test result predicted the measured velocity field qualitatively. The method was applied to study the interaction of vortex and premixed flame. Increased volume expansion did not change the initial growth rate of flame area. However, the residence time and flame surface area increased with higher expansion ratios.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.155-160
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• 2001

This paper describes a probabilistic fracture mechanics (PFM) analysis based on Monte Carlo (MC) simulation. In the analysis of CANDU pressure tube, it is necessary to perform the PFM analyses based on statistical consideration of flaw generation time. A depth and an aspect ratio of initial semi-elliptical surface crack, a fracture toughness value, delayed hydride cracking (DHC) velocity, and flaw generation time are assumed to be probabilistic variables. In all the analyses, degradation of fracture toughness due to neutron irradiation is considered. Also, the failure criteria considered are plastic collapse, unstable fracture and crack penetration. For the crack growth by DHC, the failure probability was evaluated in due consideration of flaw generation time.

• Journal of Mechanical Science and Technology
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• v.16 no.1
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• pp.116-124
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• 2002

In order to investigate the soot formation and oxidation processes, we employed the two variable approach and its source terms representing soot nucleation, coagulation, surface growth and oxidation. For the simulation of the taxi-symmetric turbulent reacting flows, the pressure-velocity coupling is handled by the pressure based finite volume method. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical models used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reacting flow field.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.591-596
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• 2001

Micron-size mechanical devices are becoming more prevalent, both in commercial applications and in scientific inquiry. Within the last decade, a dramatic increase in research activities has taken place, mostly due to the rapidly expanding growth of applications in areas of MEMS(Micro-Electro-Mechanical Systems), bioengineering, chemical systems, and advanced energy systems. In this study, we have described the effects of vortex viscosity variation on the flowfields in a micro-slot between rotating surfaces of revolution using a micropolar fluid theory. In order to solve this problem, we have used boundary layer equations and applied non-zero values of the microrotation vector on the wall. The results are compared with the corresponding flow problems for Newtonian fluid. Results show that the coefficient $\delta$ controls the main part of velocity ${\upsilon}_x$ and the coefficient M controls the main part of microrotation component ${\Omega}_{\theta}$.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.23-28
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• 1985

A model for degradation of $eta$-$Al_2O_3$ is derived from sress generated by Poiseuille pressure capillary effect and effulent flux in charging process of Na-S Battery. Critical current density for degradation increase with increasing the crack length and crack tip radius. radius 10-7cm and crack length 10-5cm Dependence of crack growth velocity on crack lengh is seperated two regions that is for a large crack length it is predominated by Poiseuille pressure and effulent fluex but in the case of small crack length it is controlled by capillary effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1669-1680
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• 1998

A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength assigned by the density difference between the burned and the unburned region. The present model provides good agreement with the experimental results. Including volume expansion, the flow field is adjusted to accommodate the increased volume flow rate which crossing the flame front and the result predicts the same behavior of measured velocity field qualitatively. The effect of increasing volume expansion does not change the initial growth rate of flame area but increase the residence time. Consequently this effect increases the maximum area of flame front. The flame propagation in varying flow field due to volume expansion provides a promising way to represent the wrinkled turbulent premixed flames in a numerically efficient manner.