• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.159-159
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• 2000

Initial growth mode of Nb on Cu(100) is studied by scanning tunneling microscopy (STM) and density functional theory. Nb/Cu is immiscible at room temperature, but isolated Nb atoms are expected to be incorporated up to the second layer by DFT. STM shows that Nb atoms mix with Cu atoms in the first layer at room temperature and diffuse into the second layer upon annealing. In the second layer, Nb/induced features are preferentially found at step edges and appear as bright dots surrounded by dark rings. Details of comparison between experiment and theory will be discussed.

• Journal of Ship and Ocean Technology
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• v.8 no.3
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• pp.8-17
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• 2004

A numerical method is developed for computing the free surface flows around a transom stern of a ship at a high Froude number. At high speed, the flow may be detached from the flat transom stern. In the limit of the high Froude number, the problem becomes a planning problem. In the present study, we make the finite-element computations for a transom stern flows around a wedge-shaped floating ship. The numerical method is based on the Hamilton's principle. The problem is formulated as an initial value problem with nonlinear free surface conditions. In the numerical procedures, the domain was discretized into a set of finite elements and the numerical quadrature was used for the functional equation. The time integrations of the nonlinear free surface condition are made iteratively at each time step. A set of large algebraic equations is solved by GMRES(Generalized Minimal RESidual, Saad and Schultz 1986) method which is proven very efficient. The computed results are compared with previous numerical results obtained by others.

• Steel and Composite Structures
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• v.38 no.3
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• pp.293-304
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• 2021

The aim of this paper is to analyze the nonlinear bending of functionally graded (FG) curved nanobeams reinforced by carbon nanotubes (CNTs) in thermal environment. Chen-Yao's surface elastic theory and geometric nonlinearity are also considered. The nanobeams are subjected to uniform loadings and placed on three-parameter substrates. The Euler-Lagrange equations are employed to deduce the equations of equilibrium. Then, the asymptotic solutions and boundary value problems are analytically determined by utilizing the two-step perturbation technique. Finally, the effects of the surface parameters, geometric factors, foundation stiffness, volume fraction, thermal effects and layout type of CNTs on the nonlinear bending of the nanobeams are discussed.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3495-3498
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• 2013

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.19-20
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• 2006

Two methods that can reduce reflectance in solar cells are surface texturing and anti-reflection coating. Wet chemical etching is a typical method that surface texturing of multi-crystalline silicon. Wet chemical etching methods are the acid texturization of saw damage on the surface of multi-crystalline silicon or double-step chemical etching after KOH saw damage removal too. These methods of surface texturing are realized by chemical etching in acid solutions HF-$HNO_3$-$H_2O$. In this solutions we can reduce reflectance spectra by simple process etching of multi-crystalline silicon surface. We have obtained reflectance of 27.19% m 400~1100nm from acidic chemical etching after KOH saw damage removal. This result is about 7% less than just saw damage removal substrate. The surface morphology observed by microscope and scanning electron microscopy (SEM).

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.612-615
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• 1996

In the continuous casting process, molten metal contacts the mold wall and the molten metal surface is subject to the mold oscillation. The mold oscillation results in the oscillation marks on the surface of solidified steel, which has undesirable effects on the quality of slabs. In order to reduce the oscillation marks by achieving soft contact of molten metal with the mold surface, alternating magnetic field is applied to the surface of molten metal. However, if the magnetic field strength becomes too strong, the melt flow induced by the magnetic field. causes the instability of the molten metal surface, which has also the bad influence on the slab quality. Therefore, it is very important to choose the optimal position of the inductor coil and the optimal level of electric power to minimize the surface defects. In the present work, as a first step toward the optimization problem of the process, numerical studies are performed to investigate the effects of coil position and the electric power level on the meniscus shape and the flow field. As numerical tools, the boundary integral equation method(BIEM) is used for the magnetic field analysis and the finite difference method (FDM) with orthogonal grid generation is used for the flow analysis.

• The Journal of Korean Medical History
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• v.26 no.2
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• pp.135-148
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• 2013

This study analyzed surface-chemical transitions in manufacturing process of traditional acupuncture as proposed method by Dongeuibogam. The manufacturing process of traditional acupuncture from a used iron for a long time was divided by primary medicinal herbs treatment, secondary medicinal herbs treatment and tertiary treatment using by dog meat. The traditional acupuncture research process was measured according to the characteristics and changes of the specimens at each processing step of the manufacturing process. The following devices were used to Surface analysis. Scanning electron microscopy (SEM), Energy Dispersive Spectrometer (EDS), X-ray diffraction analyzer (XRD). As a result, medicinal herbs removed impurities on the surface and raised the antibacterial effect in the manufacturing process of traditional acupuncture. Furthermore, the ingredients of medicinal herbs were coated on the surface of the iron. Dog meat influenced to prevent surface corrosion, reduce friction when the acupuncture was inserted. Although the process empirically obtained, a glimpse of the wisdom of our ancestors was revealed. These ancestral wisdom can be expected to apply today, when used in manufacturing process of a modern stainless steel acupuncture to compensate for the defective part.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.49-52
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• 2009

We have investigated the effect of the surface roughness of TCO substrate on the characteristics of OLED (organic light emitting diodes) devices. In order to control the surface roughness of ITO thin films, we have processed photolithography and reactive ion etching. The micro-size patterned mask was used, and the etching depth was controlled by changing etching time. The surface morphology of the ITO thin film was observed by FESEM and atomic force microscopy (AFM). And then, organic materials and cathode electrode were sequentially deposited on the ITO thin films. Device structure was ITO/$\alpha$-NPD/DPVB/Alq3/LiF/Al. The DPVB was used as a blue emitting material. The electrical characteristics such as current density vs. voltage and luminescence vs. voltage of OLED devices were measured by using spectrometer (minolta CS-1000A). The current vs. voltage and luminance vs. voltage characteristics were systematically degraded with increasing surface roughness. Furthermore, the retention test clearly presented that the reliability of OLED devices was directly influenced with the surface roughness, which could be interpreted in terms of the concentration of the electric field on the weak and thin organic layers caused by the poor step coverage.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.145-155
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• 1998

A computer code has been developed for the computation of the viscous flow around a ship model with the free surface. In this code, the incompressible Reynolds-averaged Navier-Stokes equations are solved numerically by a finite difference method which employes second-order finite differences for the spatial discretization and a four-stage Runge-Kutta scheme for the temporal integration of the governing equations. For the turbulence closure, a modified version of the Baldwin-Lomax model is exploited. The location of the free surface is determined by solving the equation of the kinematic free-surface condition using the Lax-Wendroff scheme and the boundary-fitted grid is generated at each time step so that one of the grid surfaces always coincides with the free surface. An inviscid approximation of the dynamic free-surface boundary condition is applied as the boundary conditions for the velocity and pressure on the free surface. To validate the computational method and the computer code developed in the present study, the numerical computations are carried out for both Wigley parabolic hull and Series 60 $C_B=0.6$ ship model and the computational results are compared with the experimental data.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.3
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• pp.14-19
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• 2007

Rapid prototyping (RP) technology can fabricate any 3D physical model regardless of geometric complexity using the layered manufacturing (LM) process. Stereolithography (SL) is the best-known example of RP technology. In general, the surface quality of a raw SL-generated part is unsatisfactory for industrial purposes due to the step artefact created by the LM process. Despite of the increased number of applications for SL parts, this side effect limits their uses. In order to improve their surface quality, additional post-machining finishing, such as traditional grinding, is required, but post-machining is time consuming and can reduce the geometric accuracy of a part. Therefore, this study proposes a post-machining technology combining coating and grinding processes to improve the surface quality of SL parts. Paraffin wax and pulp are used as the coating and grinding materials. By grinding the coating wax only up to the boundary of the part, the surface smoothness can be improved without damaging the surface. Finally, moulding and casting experiments were performed to confirm the suitability of the SL parts finished using the proposed process with rapid tooling (RT) techniques.