http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Remote homoepitaxy of ZnO microrods across graphene layers
Jeong, Junseok,Min, Kyung-Ah,Shin, Dong Hoon,Yang, Woo Seok,Yoo, Jinkyoung,Lee, Sang Wook,Hong, Suklyun,Hong, Young Joon The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.48
<P>Two-dimensional atomic layered materials (2d-ALMs) are emerging candidates for use as epitaxial seed substrates for transferrable epilayers. However, the micrometer-sized domains of 2d-ALMs preclude their practical use in epitaxy because they cause crystallographically in-plane disordering of the overlayer. Ultrathin graphene can penetrate the electric dipole momentum from an underlying crystal layer to the graphene surface, which then drives it to crystallize the overlayer during the initial growth stage, thus resulting in substantial energy saving. This study demonstrates the remote homoepitaxy of ZnO microrods (MRs) on ZnO substrates across graphene layers <I>via</I> a hydrothermal method. Despite the presence of poly-domain graphene in between the ZnO substrate and ZnO MRs, the MRs were epitaxially grown on <I>a</I>- and <I>c</I>-plane ZnO substrates, whose in-plane alignments were homogeneous within the wafer's size. Transmission electron microscopy revealed a homoepitaxial relationship between the overlayer MRs and the substrate. Density-functional theory calculations suggested that the charge redistribution occurring near graphene induces the electric dipole formation, so the attracted adatoms led to the formation of the remote homoepitaxial overlayer. Due to a strong potential field caused by long-range charge transfer given from the substrate, even the use of bi-layer and tri-layer graphene resulted in remote homoepitaxial ZnO MRs. The effects of substrate crystal planes were also theoretically and empirically investigated. The ability of graphene, which can be released from the mother substrate without covalent bonds, was utilized to transfer the overlayer MR arrays. This method opens a way for producing well aligned, transferrable epitaxial nano/microstructure arrays while regenerating the substrate for cost-saving device manufacturing.</P>
A benchmark problem for the two- and three-dimensional Cahn–Hilliard equations
Jeong, Darae,Choi, Yongho,Kim, Junseok Elsevier 2018 Communications in nonlinear science & numerical si Vol.61 No.-
<P><B>Abstract</B></P> <P>This paper proposes a benchmark problem for the two- and three-dimensional Cahn–Hilliard (CH) equations, which describe the process of phase separation. The CH equation is highly nonlinear and an analytical solution does not exist except trivial solutions. Therefore, we have to approximate the CH equation numerically. To test the accuracy of a numerical scheme, we have to resort to convergence tests, which consist of consecutive relative errors or a very fine solution from the numerical scheme. For a fair convergence test, we provide benchmark problems which are of the shrinking annulus and spherical shell type. We show numerical results by using the explicit Euler’s scheme with a very fine time step size and also present a comparison test with Eyre’s convex splitting schemes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Benchmark problems are provided for the Cahn–Hilliard equations. </LI> <LI> Accurate numerical solutions are generated using a very fine step size. </LI> <LI> The proposed method can be applied to most of the numerical schemes. </LI> </UL> </P>
A Projection Method for the Conservative Discretizations of Parabolic Partial Differential Equations
Jeong, Darae,Kim, Junseok Springer-Verlag 2018 Journal of scientific computing Vol.75 No.1
<P>We present a projection method for the conservative discretizations of parabolic partial differential equations. When we solve a system of discrete equations arising from the finite difference discretization of the PDE, we can use iterative algorithms such as conjugate gradient, generalized minimum residual, and multigrid methods. An iterative method is a numerical approach that generates a sequence of improved approximate solutions for a system of equations. We repeat the iterative algorithm until a numerical solution is within a specified tolerance. Therefore, even though the discretization is conservative, the actual numerical solution obtained from an iterative method is not conservative. We propose a simple projection method which projects the non-conservative numerical solution into a conservative one by using the original scheme. Numerical experiments demonstrate the proposed scheme does not degrade the accuracy of the original numerical scheme and it preserves the conservative quantity within rounding errors.</P>
Efficient 3D Volume Reconstruction from a Point Cloud Using a Phase-Field Method
Jeong, Darae,Li, Yibao,Lee, Heon Ju,Lee, Sang Min,Yang, Junxiang,Park, Seungwoo,Kim, Hyundong,Choi, Yongho,Kim, Junseok Hindawi Limited 2018 Mathematical problems in engineering Vol.2018 No.-
<P>We propose an explicit hybrid numerical method for the efficient 3D volume reconstruction from unorganized point clouds using a phase-field method. The proposed three-dimensional volume reconstruction algorithm is based on the 3D binary image segmentation method. First, we define a narrow band domain embedding the unorganized point cloud and an edge indicating function. Second, we define a good initial phase-field function which speeds up the computation significantly. Third, we use a recently developed explicit hybrid numerical method for solving the three-dimensional image segmentation model to obtain efficient volume reconstruction from point cloud data. In order to demonstrate the practical applicability of the proposed method, we perform various numerical experiments.</P>
Fast and accurate adaptive finite difference method for dendritic growth
Jeong, Darae,Kim, Junseok Elsevier 2019 Computer physics communications Vol.236 No.-
<P><B>Abstract</B></P> <P>We propose a fast and accurate adaptive numerical method for solving a phase-field model for dendritic growth. The phase-field model for dendritic growth consists of two equations. One is for capturing the interface between solid and melt. The other is for the temperature distribution. For the phase-field equation, we apply a hybrid explicit method on a time-dependent narrow-band domain, which is defined using the phase-field function. For the temperature equation, we apply the explicit Euler method on the whole computational domain. The novelties of the proposed numerical algorithm are that it is very simple and that it does not require the conventional complex adaptive data structures. Our numerical simulation results are consistent with previous results. Furthermore, the computational time required (CPU time) is shorter.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fast and accurate adaptive finite difference method is developed. </LI> <LI> The algorithm implementation is very simple. </LI> <LI> The proposed method can straightforwardly be extended to three-dimensional space. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
PATH AVERAGED OPTION VALUE CRITERIA FOR SELECTING BETTER OPTIONS
JUNSEOK KIM,MINHYUN YOO,HYEJU SON,SEUNGGYU LEE,MYEONG-HYEON KIM,YONGHO CHOI,DARAE JEONG,YOUNG ROCK KIM 한국산업응용수학회 2016 Journal of the Korean Society for Industrial and A Vol.20 No.2
In this paper, we propose an optimal choice scheme to determine the best option among comparable options whose current expectations are all the same under the condition that an investor has a confidence in the future value realization of underlying assets. For this purpose, we use a path-averaged option as our base instrument in which we calculate the time discounted value along the path and divide it by the number of time steps for a given expected path. First, we consider three European call options such as vanilla, cash-or-nothing, and asset-or-nothing as our comparable set of choice schemes. Next, we perform the experiments using historical data to prove the usefulness of our proposed scheme. The test suggests that the path-averaged option value is a good guideline to choose an optimal option.
SCHWARTZ P SURFACES FOR TISSUE SCAFFOLDS
Junseok KIM,Joong Yeon LIM,Seonggi KIM,Darae JEONG,Hyun Geun LEE,Dongsun LEE,Jaemin SHIN 한국산업응용수학회 2010 한국산업응용수학회 학술대회 논문집 Vol.5 No.2
Tissue scaffolds provide temporary mechanical support for tissue regeneration while shaping ingrowth tissues. Therefore tissue scaffolds should be biocompatible, biodegradable with appropriate porosity, pore structure, and pore distribution. The design of optimized tissue scaffolds based on the fundamental knowledge of its microstructure is an important issue. In this paper, we generate the Schwarz primitive (P) surface with various volume fractions and explore its use. The Schwarz primitive (P) surface enable the design of vary high surface-to-volume ratio structure with high porosity and mechanical properties.