• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.223-232
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• 2003

The co-precipitation method is applied to synthesize the cathode material Li[L $i_{x}$M $n_{1-x-y}$C $r_{y}$ ] $O_2$ for lithium rechargeable batteries at $650^{\circ}C$ (CR650) and 8$50^{\circ}C$ (CR850), respectively. Rietveld indices indicate that $R_{wp}$ with respect to $R_{exp}$ ( $R_{wp}$/ $R_{exp}$) are 9.2%/10.1% for CR650 and 15.9%/9.76% for CR850, respectively. $R_{B}$ and S (GofF) shows 10.9%, 8.54% and 1.9, 1.6, respectively. Rietveld structure refinement reveals that layer structure of LiMn $O_2$ (R3m) coexists with lower symmetry of Li[L $i_{1}$3/M $n_{2}$3/] $O_2$ (C2/c) due to superlattice ordering of Li and Mn in metal-transition containing layers. Unit-cell parameters are calculated as a=2.8520(2)$\AA$, c=14.248(2)$\AA$, V=100.40(l)$\AA^3$ for CR650, and a=2.8504(1)$\AA$, c=14.2371(7)$\AA$, V=100.179(8)$\AA^3$ for CR850. Final chemistry is obtained as Li[L $i_{0.35}$M $n_{0.56}$C $r_{0.09}$] $O_2$ (CR650) and Li[L $i_{0.27}$M $n_{0.61}$C $r_{0.13}$] $O_2$ (CR850), respectively.y...y..vely.y...y..

• Journal of Digital Contents Society
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• v.17 no.1
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• pp.51-57
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• 2016

Distributed Computing attempts to harness a massive computing power using a great numbers of idle PCs resource distributed linked to the internet and processes a variety of applications parallel way such as bio, climate, cryptology, and astronomy. In this paper, we develop internet-distributed computing environment, so that we can analyze High Resolution Rainfall Prediction application in meteorological field. For analyze the rainfall forecast in Korea peninsula, we used QPM(Quantitative Precipitation Model) that is a mesoscale forecasting model. It needs to a lot of time to construct model which consisted of 27KM grid spacing, also the efficiency is degraded. On the other hand, based on this model it is easy to understand the distribution of rainfall calculated in accordance with the detailed topography of the area represented by a small terrain model reflecting the effects 3km radius of detail and terrain can improve the computational efficiency. The model is broken down into detailed area greater the required parallelism and increases the number of compute nodes that efficiency is increased linearly.. This model is distributed divided in two sub-grid distributed units of work to be done in the domain of $20{\times}20$ is networked computing resources.

• The KIPS Transactions:PartA
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• v.14A no.7
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• pp.421-434
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• 2007

Among many other CG generated natural scenes, the representation of ocean surfaces is one of the most complicated and time-consuming problem because of its large extent and complex surface movement. We present a hybrid method to represent and animate unbound deep-water ocean surfaces by utilizing graphics processor as both simulation and rendering core. Our technique is mainly based on spectral approaches that generate a high-detailed height field using Fourier transform on a 2D regular grid. Additionally, we incorporate Gerstner model and generate low-detailed height field on a 2D projected grid in order to represent large waves and main structure of ocean surface. There is no interruption between CPU and GPU, and no need to transfer simulation results from the system memory to graphics hardware because the entire simulation and rending processes are done on graphics processor. As a result we can synthesize and render realistic water surfaces in real-time. Proposed techniques are readily adoptable to real-time applications such as computer games that have heavy work load on CPU but still demand plausible natural scenes.

• Composites Research
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• v.31 no.5
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• pp.251-259
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• 2018

In this paper, statistical volume element modeling method was developed for multi-scale progressive failure analysis of fiber reinforced composite materials. Big-size statistical volume elements (BSVEs) was considered to minimize the size effect in the micro-scale, by including as many fibers as possible. For that purpose, a mesh cutting method is suggested and adapted into the fiber model generator that creates finite element domain rapidly. The fiber defect model was also developed based on the experimental distribution of the fiber strength. The size effects from the local load sharing (LLS) are evaluated by increasing the fiber inclusion in the micro-scale model. Finally, continuum damage mechanics (CDM) model to the fiber direction was extracted from numerical analysis on BSVEs. And it was compared with strength prediction from typical representative volume element (RVE) model.

• Journal of the Korea Society of Computer and Information
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• v.17 no.9
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• pp.9-16
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• 2012

In this paper, we propose the two dimensional variable-length vector storage format which can be used for efficient storage of sparse matrix in the FEM (finite element method). The proposed storage format is the method storing only actual needed non-zero values of each row on upper triangular matrix with the total rows N, by using two dimensional variable-length vector instead of $N{\times}N$ large sparse matrix of entire equation of finite elements. This method only needs storage spaces of the number of minimum 1 to maximum 5 in 2D grid structure and the number of minimum 1 to maximum 14 in 3D grid structure of analysis target. The number doesn't excess two times although involving index number. From the experimental result, we can find out that the proposed storage format can reduce the memory space more effectively, as the total number of nodes increases, than the existing skyline storage format storing maximum column height.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1021-1029
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• 1992

A rational and straightforward method is introduced for developing continuum models of large platelike periodic lattice structures based on energy equivalence. The procedure for developing continuum plate models involves the use of existing well-defined finite element matrices for the easy calculation of strain and kinetic energies of a repeating cell, from which the reduced stiffness and mass matrices are obtained in terms of continuum degrees- of-freedom defined in this paper. The equivalent continuum plate properties are obtained from the direct comparison of the reduced matrices for continuum plate with those for lattice plate. The advantages of the present continuum method are that it may be applied to arbitrary lattice configurations and may give most diverse equivalent continuum plate properties including all kinds of coupling, while other methods may give only limited structural properties. To evaluate the continuum method developed in this paper, free vibration analyses for both of continuum and lattice plates are conducted. Numerical results show that the present continuum method gives very reliable structural and dynamic properties compared to other well-recognized methods.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.71-75
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• 2005

$La_{0.5}Ca_{0.5}MnO_3$ colossal magnetoresistance (CMR) powders and pellets were synthesized by sol-gel process. The structural changes were investigated by FT-IR, CP/MAS $^{13}C$ solid state NMR spectroscopy and XRD. The particle characterization, microstructure of sintered samples, and cation composition of gel powders were studied by FE-SEM/EDS, TEM and ICP-AES. The structure refinement reveals that $La_{0.5}Ca_{0.5}MnO_3$ has orthorhombic, perovskite type unit cell. The magnetic characterizations were identified through measurement of magnetic moment by VSM.

• Journal of Korean Neurosurgical Society
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• v.30 no.sup1
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• pp.159-164
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• 2001

Reduction cranioplasty is one of the treatment modality among many treatment options for macrocephaly with hydrocephalus. The most previous techniques of reduction cranioplasty have some disadvantages such as difficult airway maintenance, pressure sore due to modified prone position, severe venous infarct due to obstruction of venous blood flow and large amount of bleeding from the dissection of superior sagittal sinus to obtain bone fragment needed. A 28-month-old girl had extreme macrocephaly. She couldn't control head rotation and keep sitting position. The operation was performed at supine position with adequate exposure of entire calvarium and the hinge was made in occipital bone fragment that covered posterior part of superior sagittal sinus. Bleeding volume and the other complications were decreased and acceptable reduction was achieved with this method.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.145-145
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• 1999

La-Ca-Mn-O (LCMO) 박막에서 초거대 자기 저항 효과와 발견된 이후 자기 센서와 고밀도 자기 저장 매체로서 응용하기 위한 연구가 진행되고 있다. 그러나 현재 대부분의 증착은 타겟과 박막간의 조성의 일치를 위하여 PLD 방법을 이용하고 있으며 RF magnetron sputtering 법으로 증착한 예는 많이 보고되고 있지 않으며 특히 적층 성장시킨 예는 아직 보고되지 있지 않다. 또한 LCMO와의 낮은 격자 상수 불일치를 보이는 SrTiO3와 LaAlO3 기판에 LCMO 박막을 성장시킬 경우 LaAlO3의 경우 XRD rocking curve의 curve의 FWHM 값이 SrTiO3 상에 증착시킨 것의 10배 이상의 값을 보인다는 것은 주목할 만한 사실이다. RF magnetron sputtering 법을 이용하여 LaAlO3 기판상에 145nm MCMO 박막을 적층성장시켰다. XRD $ heta$-2$\theta$ scan을 통해 박막이 c-축 배향한 것을 확인할 수 있었으며 RBS 분석결과 4.98%의 minimumyield를 보였으며 이로부터 박막이 적층성장한 것을 확인할 수 있었다. LCMO (200) peak의 XRD $\theta$-rocking 결과 FWHM의 값은 0.311$^{\circ}$를 보였으나 2개의 피크가 존재하는 것을 볼 수 있었다. 따라서 기판의 (200) 피크를 XRD $\theta$-2$\theta$ scan에서 0.3$^{\circ}$ 간격으로 두 개의 피크를 관찰할 수 있었는데 이는 기판과 박막간의 stress로 인한 tetragonal distortion에 의한 것으로 알려져 있었다. 따라서 기판상에 박막이 어떤 식으로 적층 성장되었는지를 RBS를 이용하여 <001>과 <011> 방향으로 2MeV He++를 주입하여 0.1$^{\circ}$ 간격으로 틸팅을 해본 결과 <001> 방향에서는 1.12$^{\circ}$의 차이를 보였다. 이는 기판과의 compressive stress로 인해 c축 방향으로 늘어났으며 stress relaxed layer는 XRD 결과와는 달리 관찰할 수 없었다. 이러한 현상의 기판 자체의 twin 구조로 인한 것으로 생각된다. RBS 분석후 고분해능 XRD를 이용해 LCMO (200) peak의 $\theta$-rocking 결과 이제R지 laAlO3 상 증착한 LCMO의 값으로는 제일 작은 0.147$^{\circ}$를 나타내었다.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1069-1074
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• 2008

In this work, we made a study for the 3D SAM formation of octanethiol, decanethiol, and dodecanethiol on copper nanoparticles and we verified stability of the copper particle depending on the ratio of dodecanethiol to copper. The reaction was performed in a one-phase system under nitrogen atmosphere and the thiolated copper particles could be obtained by centrifugation. We could confirm that the nanoparticles consisted of a spherical shape of 3~6 nm from TEM images. FT-IR, XPS and TGA results showed that alkanethiols were chemisorbed via thiol group and the packing density of the alkanethiols on copper surface increased with the alkyl chain lengths. XRD patterns gave us useful information about superlattice formations. Finally, $Cu_2O$ was formed when the molar ratio of dodecanethiol to copper is less than unity and copper nanoparticles formed more compact 3D SAMs when the molar ratio of dodecanethiol to copper was 1.25.