• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.533-542
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• 1999

In this study the flow characteristics of developing turbulent pulsating flows in a square-sec-tional 180。 curved duct are investigated experimentally. The experimental study of air flow in a square-sectional curved duct is carried out to measure axial velocity distribution secondary flow velocity profiles and wall shear stress distributions by using a Laser Doppler Velocimetry system with the data acquisition and processing system of Rotating Machinery Resolver (RMR) and PHASE software at the entrance region of the duct which is divided into 7 sections from the inlet(${{\o}}=0_{\circ}$) to the outlet (${{\o}}=180_{\circ}$) in $30_{\circ}$ intervals. The results obtained from the study are summarized as follows: (1) The time-averaged critical Dean number of turbulent pulsating flow(De ta, cr) is greater than $75{\omega}+$ It is understood that the critical Dean number and the critical Reynolds number are related to the dimensionless angular frequency in a curved duct. (2) Axial velocity profiles of turbulent pulsating flows are of an annular type similar to those of turbulent stead flows. (3) Secondary flows of trubulent pulsating flows are strong and complex at the entrance region. As velocity amplitudes(A1) become larger secondary flows become stronger. (4) Wall shear stress distributions of turbulent pulsating flows in a square-sectional $180_{\circ}$ curved duct are exposed variously in the outer wall and are stabilized in the inner wall without regard to the phase angle.

• International Commerce and Information Review
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• v.11 no.1
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• pp.157-176
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• 2009

This study analyzed the information factors which determine cash liquidity in Korean export-oriented companies. In this paper, cash liquidity means the ratio of the value of cash or cash equivalent to the asset value subtracted marketable securities value from total asset value. The empirical test shows that main information factors are the size of company, the growth opportunity of company, the volatility of operating cash flows and free cash flows, the credit yield spread of company, the debt ratio, the turnover ratio of cash flows and free cash flows, and the estimate of bankruptcy that amounts to the inverse number of Z score. In summary, the size of company, debt ratio, turnover ratio of cash flows and free cash flows, and Z-score have negative influence on the cash liquidity of Korean export-oriented companies. but the volatility of operating cash flows affect the cash liquidity positively.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.55.2-55.2
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• 2011

Many astrophysical high energy phenomena involve relativistic flows. We describe codes for adiabatic and isothermal flows in relativistic regimes. For adiabatic flows, we employ an equation of state (EOS) which is simple and yet approximates very closely the EOS of the single-component perfect gas. For isothermal flows, we use an EOS of constant sound speed. We present the eigenstructures of relativistic hydrodynamics which can be used to build numerical codes, and discuss the calculation of primitive variables from conservative ones for both adiabatic and isothermal flows. The shock tube tests show differences between the two flows.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.815-829
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• 2008

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and railway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched. Furthermore debris flows are very hard to predict. Flexible Ring net barriers are multi-functional mitigation devices commonly applied to rock fall or floating wood protection in floods, snow avalanches and also mud flows or granular debris flows, if properly dimensioned for the process or processes for which they are intended. Overtopping of the barriers by debris flows and sediment transport is possible, supporting the design concept that a series of barriers may be used to stop volumes of debris larger than are possible using only one barrier. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.

• Journal of the Chungcheong Mathematical Society
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• v.22 no.1
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• pp.73-80
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• 2009

This paper aims to study local and global structure of holomorphic flows on $\mathbb{C}^1$. At a singular point of a holomorphic flow, we locally sector the flow into parabolic or elliptic types. By the local structure of holomorphic flows, we classify all the possible types of topologies of $\omega$-limit sets.

• Journal of the Korean Mathematical Society
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• v.56 no.6
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• pp.1641-1654
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• 2019

In this paper we study the quasi-neutral limit of the compressible magnetohydrodynamic flows in the periodic domain ${\mathbb{T}}^3$ with the well-prepared initial data. We prove that the weak solution of the compressible magnetohydrodynamic flows governed by the Poisson equation converges to the strong solution of the compressible flow of magnetohydrodynamic flows as long as the latter exists.

• Honam Mathematical Journal
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• v.42 no.4
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• pp.769-780
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• 2020

In this paper, Fermi-Walker derivative for inextensible flows of curves are researched in 3-dimensional Galilean space G3. Firstly using Frenet and Darboux frame with the help of Fermi-Walker derivative a new approach for these flows are expressed, then some results are obtained for these flows to be Fermi-Walker transported in G3.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.592-593
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.778-779
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.780-781
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• 2005