http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Cha, Pil-Ryung,Nam, Ho-Seok,Jeon, Dae-Yeong,Yoon, Jong Gyu 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.1
This study presents a simple and robust algorithm for the optimal design of the system with coupled complex transport phenomena: the transport phenomena comprise fluid flow, heat and mass transfer. The (1+1)-Evolution Strategy method is adopted as the optimization method. In order to analyze the transport phenomena in the complex geometry generated during the optimization procedure, the finite volume method with a boundary fitted curvilinear coordinate system is used. To confirm the validity of the present method, the optimal design for the inner shape of the simplified two-dimensional Submerged Entry Nozzle in the continuous slab caster is conducted. It is shown that the resulting design of the nozzle is consistent with the purpose and constraints of the design.
Mulli-Scale Simulation Study for Growth Dynamics of Irreversible Islands during Submonolayer Epitaxy
Cha, Pil-Ryung,Hong, Ki-Ha,Yoon, Jong-Kyu 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.2
Using empirical embedded atom method (EAM) potential, activation barriers of adatom diffusion on the surface, diffusion along the step edge, and island corner diffusion are calculated for metal (111) surface (Pt, Ag) and the behavior of those barriers is investigated with respect to lattice strain. Based on the calculated barriers, we perform the kinetic Monte Carlo simulation for monolayer island growth and for how the variation of the activation barriers with lattice strain changes the island growth. Results from this work show that the lattice strain transforms the island growth shape from <1 12> dendritic through random fractal to <112> dendritic at 100 K and from triangular through hexagonal to inverse triangular at 400 K.
( Pil Ryung Cha ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 ELECTRONIC MATERIALS LETTERS Vol.3 No.3
Through a linear stability analysis of the competition between step-step elastic interactions and the asymmetry of adatoms incorporated from the terraces to the step edges in step bunching instability, growth mode diagrams were proposed with respect to the homo-epitaxial growth and hetero-epitaxial growth under various operating conditions and material properties. The force monopoles at the steps and the interaction of the force monopoles induce the step bunching on the vicinal surface. In contrast, the kinetic asymmetry of the adatom incorporation at the steps prevents the step bunching instability. The growth mode on the vicinal surface is determined by the competition between the elastic step-step interactions and the Ehrlich-Schwoebel barrier.
A Phase Field Model for Electromigration-Induced Surface Evolution
Kim, Ji-Hee,Cha, Pil-Ryung,Yeon, Dong-Hee,Yoon, Jong-Kyu 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.3
In this study, a phase field model is presented to study the effects of electromigration on the surface evolution of single crystal Al metal interconnects. Two dimensional computer simulations are performed for the surface evolution of metal interconnects due to electromigration in various conditions, such as anisotropy in diffusivity, different initial void sizes, and different crystallographic directions compared to the direction of the ambient electric field. From the results of computer simulations, it may be seen that the types of anisotropy and the relative direction of the diffusivity are the decisive factors in motion and shape change. As the symmetry of anisotropy in diffusivity decreases, the void evolves into a more unstable shape. Moreover, the voids of the system with two-fold diffusion symmetry are most likely to evolve into slits when the crystallographic direction is toward a specific orientation compared to the direction of the ambient electric field.
Phase Field Model for the Dynamics of Steps and Islands on Crystal Surfaces
Yeon, dong-Hee,Cha, Pil-Ryung,Chung, Sang-Ik,Yoon, Jong-Kyu 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.1
Surface stress and lattice strain are the essential factors on the self-organization of a surface, because they affect remarkably adatom diffusion on surfaces and at step edges and induce the elastic interaction between the surface steps. In spite of the importance, their kinetic role on the growth dynamics of the step and the islands in thin film deposition is not yet fully understood. Therefore, in this work, a continuum model is presented, which considers both elastic and entropic interactions between the steps or the islands on the crystal surface and growth dynamics of the steps or the islands. The present model is based on the Ginzburg-Landau approach on phase transition and reduces to the Gibbs-Thompson equation at the step edges. In addition, the elastic field, which is generated by the surface force, is calculated using elastic surface Green function under the assumption that the atomic displacement field decays exponentially from the surface. Using the resulting atomic displacement, the elastic interaction between the surface steps is incorporated into the model. Through numerical simulations, it is shown that the elastic interaction between the steps in our model is in good agreement with previous theories and that the phase field model has the ability to solve the various phenomena of the step dynamics.
Ko, Kyung Jun,Cha, Pil Ryung,Park, Jong Tae,Kim, Jae Kwan,Hwang, Nong Moon Trans Tech Publications, Ltd. 2007 Materials science forum Vol.558 No.-
<P>Phase-field model (PFM) in multiple orientation fields was used to simulate the grain growth in three-dimensions (3-D) for isotropic and anisotropic grain boundary energy. In the simulation, the polycrystalline microstructure was described by a set of non-conserved order parameters and each order parameter describes each orientation of grains. For isotropic grain boundary energy, the simulation showed the microstructure evolution of normal grain growth. For anisotropic grain boundary energy, however, the simulation showed that certain grains which share a high fraction of low energy grain boundaries with other grains have a high probability to grow by wetting along triple junctions and can grow abnormally with a growth advantage of solid-state wetting. The PFM simulation shows the realistic microstructural evolution of island and peninsular grains during abnormal grain growth by solid-state wetting.</P>
수직-수평온도구배법에 의한 200 mm급 사파이어 단결정 성장의 전산모사 연구
김형중 ( Hyung Joong Kim ),차필령 ( Pil Ryung Cha ),김성균 ( Seong Gyoon Kim ),문성환 ( Sung Hwan Moon ),장계원 ( Gye Won Jang ),나복기 ( Bok Kee Na ),김준환 ( Jun Hwan Kim ),김동욱 ( Dong Uk Kim ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.1
A sapphire single crystal growth process by the Vertical-Horizontal Gradient Freezing (VHGF) method was studied by a numerical analysis technique. The heater power was controlled in order to follow the given arbitrary target heater temperature profile through the whole series of the process. Due to the influence of radiation heat transfer, the heater had spatial temperature deviation in spite of the fact that the heater power was imposed uniformly through its whole body. As a structural feature of the VHGF method, temperature at the lower part of crucible was lower than that at the upper part of crucible because it was cooler at the bottom of the furnace. Thus, the movement of the solid/liquid interface was driven in the bottom-to-top direction. (Received February 4, 2014)