• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.42-47
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• 1999

In this study, we adopt the point symmetric Gauss-Seidel relaxation algorithm to obtain the steady state solution of the Navier-Stokes equations for the thermal and chemical nonequilibrium flow of air. All of the inviscid, viscous flux Jacobians and thermochemical source Jacobians are included in the implicit part Numerical simulation is performed for the thermal and chemical nonequilibrium flow over blunt body and computational results are presented. The convergence history and CPU time of the present computation are compared with the LU-SGS scheme which employs the approximate Jacobians.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.413-416
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• 2009

The paper deals with the mechanical and electrical responses of submicrocrystalline Cu-3%Ag alloy as a function of strain imposed by equal-channel angular pressing. When inducing the effective strain of 12, the initial grain site of ${\sim}50{\mu}m$ is evidently reduced within the range of $0.2-0.3{\mu}m$ in size, having a reasonably equiaxed shape. The results of tension tests at room temperature exhibit that the tensile strength of the present alloy increases with increasing the amount of strain whereas losing electrical conductivity slightly. This phenomenon can be explained based on fine grained structure together with the non-equilibrium state of grain boundaries.

• Journal of Magnetics
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• v.3 no.1
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• pp.21-30
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• 1998

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media, due to large Kerr rotation angle in the wavelength of a blue laser beam. however, since multilayer structure, as well as amorphous structure, is a non-equilibrium state in terms of free energy and MO recording is a kind of thermal recording which is conducted aound Curie temperature (Tc) of the recording media, when the multilayer is used for the MO recording media, changes in the multilayer structure are occurred as the amorphous structure do. Therefore, the assessment of the structural stability in the Co/Pd multilayer is crucially important both for basic research and applications. As the parameter of the structural stability in this research, modulation amplitude and particle size of the Co/Pd multilayer are measured in terms of Ar sputtering pressure and heat treatment temperature. From the results of the research, we find out that the magnetic exchange energy in the structural changes of a magnetic multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Geomechanics and Engineering
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• v.6 no.6
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• pp.545-560
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• 2014

For slope stability analysis, an alternative to the classical limit equilibrium method (LEM) of slices is the shear strength reduction method (SRM), which can be integrated into finite element analysis or finite difference analysis. Recently, probabilistic analysis of earth slopes has been very attractive because it is capable to take the soil uncertainty into account. However, the SRM is less commonly extended to probabilistic framework compared to a variety of probabilistic LEM analysis of earth slopes. To overcome some limitations that hinder the development of probabilistic SRM stability analysis, a new procedure based on recursive algorithm FORM with sensitivity analysis in the space of original variables is proposed. It can be used to deal with correlated non-normal variables subjected to implicit limit state surface. Using the proposed approach, a probabilistic finite element analysis of the stability of an existing earth dam is carried out in this paper.

• Steel and Composite Structures
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• v.23 no.5
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• pp.597-610
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• 2017

This paper presents a mathematical model for fixed-end moments of I-sections with straight haunches for the general case (symmetrical and/or non-symmetrical) subjected to a concentrated load localized anywhere on beam taking into account the bending deformations and shear, which is the novelty of this research. The properties of the cross section of the beam vary along its axis "x", i.e., the flange width "b", the flange thickness "t", the web thickness "e" are constant and the height "d" varies along of the beam, this variation is linear type. The compatibility equations and equilibrium are used to solve such problems, and the deformations anywhere of beam are found by the virtual work principle through exact integrations using the software "Derive" to obtain some results. The traditional model takes into account only bending deformations, and others authors present tables considering the bending deformations and shear, but are restricted. A comparison between the traditional model and the proposed model is made to observe differences, and an example of structural analysis of a continuous highway bridge under live load is resolved. Besides the effectiveness and accuracy of the developed models, a significant advantage is that fixed-end moments are calculated for any cross section of the beam "I" using the mathematical formulas.

• Journal of Magnetics
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• v.2 no.4
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• pp.147-156
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• 1997

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media, due to a large Kerr rotation angle in the wavelength of a blue laser beam. However, since multilayer structure, as well as amorphous structure, is a non-equilibrium state in terms of free energy and a MO recording technology is a kind of thermal recording which is conducted around Curie temperature (Tc) of the recording media, when the Co/Pd mulilayer is used for the MO recording media, changes in the magnetic properties are occurred as the amorphous structure do. Therefore, the assessment of the magnetic properties in the Co/Pd multilayer during interdiffusion is crucially important both for basic research and applications. As the parameter of the magnetic properties in this research, saturation magnetization and perpendicular magnetic anisotropy energy of the Co/Pd multilayer are measured in terms of Ar sputtering pressure and heat treatment temperature. Form the results of the research, we find out that the magnetic exchange energy between Co and Pd sublayers strongly affects the changes in the magnetic properties of the Co/Pd multilayers during the interdiffusion in ferromagnetic state. This discovery will provide the understanding of the magnetic exchange energy in the Co/Pd multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Journal of ILASS-Korea
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• v.17 no.1
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• pp.14-19
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• 2012

The present study conducts experimental investigation on spreading and deposition characteristics of a $4.3{\mu}l$ de-ionized (DI) water droplet impacting upon aluminum (Al 6061) flat and textured surfaces. The micro-textured surface consisted the micro-hole arrays (hole diameter: $125{\mu}m$, hole depth: $125{\mu}m$) fabricated by the conventional micro-computer numerical control (${\mu}$-CNC) milling machine process. We examined the surface effect of texture area fraction ${\varphi}_s$ ranging from 0 to 0.57 and impact velocity of droplet ranging from 0.40 m/s to 1.45 m/s on spreading and deposition characteristics from captured images. We used a high-speed camera to capture sequential images for investigate spreading characteristics and the image sensor to capture image of final equilibrium deposition droplet for analyze spreading diameter and contact angle. We found that the deposition droplet on textured surfaces have different wetting states. When the impact velocity is low, the non-wetting state partially exists, whereas over 0.64 m/s of impact velocity, totally wetting state is more prominent due to the increase kinetic energy of impinging droplet.

• Advances in nano research
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• v.10 no.4
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• pp.339-347
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Advances in nano research
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• v.10 no.5
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• pp.471-479
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.176-180
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• 2002

During the last two decades the laser beam has progressed from a sophisticated laboratory apparatus to an adaptable and viable industrial tool. Especially, in its welding mode, the laser offers high travel speed, low distortion, and narrow fusion and heat-affected zones (HAZ). The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. Although high-power laser beams have been combined with the plasma from a gas tungsten arc (GTA) torch for use in welding as early as 1980, recent work at the Ohio State University has employed a low power laser beam to initiate, direct, and concentrate a gas tungsten arcs. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process known as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma (LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well focused melted spots.