• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.183-189
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• 1998

A new computer simulation method for film growth, the kinetic Monte Carlo simulation in combination with the results obtained from molecular dynamics simulation for the transient process induced by deposited atoms, was developed. The behavior of energetic atom in Au/Au(100) thin film deposition was investigated by the method. The atomistic mechanism of energetic atom deposition that led to the smoothness enhancement and the relationship between the role of transient process and film growth mechanism were discussed. We found that energetic atoms cannot affect the film growth mode in layer-by-layer at high temperature. However, at temperature of film growth in 3-dimensional mode and in quasi-two-dimensional mode, energetic atoms can enhance the smoothness of film surface. The enhancement of smoothness is caused by the transient mobility of energetic atoms and the suppression for the formation of 3-dimensional islands.

• Proceedings of the Korean Society of Crop Science Conference
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• 2004.04a
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• pp.102-103
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• 2004

[ $\bigcirc$ ] In the growth simulation without changing of module with ORYZA2000, dry matter, LAI and leaf nitrogen content(FNLV) were estimated well under high nitrogen applicated condition, but overestimated under low nitrogen applicated condition. $\bigcirc$ Nitrogen stress factor on the SLA was introduced into ORYZA2000 because especially overestimated LAI under low nitrogen applicated condition was originated from SLA decrease with leaf nitrogen(FNLV) decrease. $\bigcirc$ In the growth simulation with modified SLA modified module, LAI was estimated well under even low nitrogen applicated condition, but dry matter was hardly changed compared with default. $\bigcirc$ Simulated plant nitrogen content and dry matter have no clear difference between modules, but compared with observed values, panicle weight(WSO) and rough rice yield(WRR14) were overestimated under high nitrogen applicated because of lodging, pest, disease and low nitrogen use efficiency.

• Journal of the Korea Society for Simulation
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• v.33 no.1
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• pp.1-17
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• 2024

Forest management is known to beneficially influence stand structure and wood production, yet quantitative understanding as well as an illustrative depiction of the effects of different management approaches on tree growth and stand dynamics are still scarce. Long-term management of beech forests must balance public interests with ecological aspects. Efficient forest management requires the reliable prediction of tree growth change. We aimed to develop a novel hybrid simulation approach, which realistically simulates short- as well as long-term effects of different forest management regimes commonly applied, but not limited, to German low mountain ranges, including near-natural forest management based on single-tree selection harvesting. The model basically consists of three modules for (a) natural seedling regeneration, (b) mortality adjustment, and (c) tree growth simulation. In our approach, an existing validated growth model was used to calculate single year tree growth, and expanded on by including in a newly developed simulation process using calibrated modules based on practical experience in forest management and advice from the local forest. We included the following different beech forest-management scenarios that are representative for German low mountain ranges to our simulation tool: (1) plantation, (2) continuous cover forestry, and (3) reserved forest. The simulation results show a robust consistency with expert knowledge as well as a great comparability with mid-term monitoring data, indicating a strong model performance. We successfully developed a hybrid simulation that realistically reflects different management strategies and tree growth in low mountain range. This study represents a basis for a new model calibration method, which has translational potential for further studies to develop reliable tailor-made models adjusted to local situations in beech forest management.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.588-595
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• 2009

The knowledge of grain growth of carbide particles is very important for manufacturing micrograined cemented carbides. In the present study, continuous and discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides is investigated using the Monte Carlo computer simulation technique. The Ostwald ripening process (solution/re-precipitation) and the grain boundary migration process are assumed in the simulation as the grain growth mechanism. The effects of liquid phase fraction, grain boundary energy and implanted coarse grain are examined. At higher liquid phase content, mass transfer via solid/liquid interfaces plays a major role in grain growth. Growth rate of the implanted grain was higher than that of the matrix grains through solution/re-precipitation and coalescence with neighboring grains. The results of these simulations qualitatively agree with experimental ones and suggest that distribution of liquid phase and carbide particle/carbide grain boundary energy as well as contamination by coarse grain are important factors controlling discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides. The contamination by coarse grains must by avoided in the manufacturing process of fine grain cemented carbides, especially with low Co.

• Journal of Powder Materials
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• v.5 no.4
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• pp.324-328
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• 1998

This paper is aimed to study the computer simulation of sintering process for ceramics by Monte Carlo and molecular dynamics methods. Plural mechanisms of mass transfer were designed in the MC simulation of sintering process for micron size particles; the transfer of pore lattices for shrinkage and the transfer of solid lattices for grain growth ran in the calculation arrays. The MD simulation was performed in the case of nano size particles of ionic ceramics and showed the characteristic features in sintering process at atomic levels. The MC and MD simulations for sintering process are useful for microstructural design for ceramics.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.589-595
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• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.15-18
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• 2003

High purity single crystalline calcium fluoride ($CaF_2$) has excellent optical transmission characteristics down to deep UV and is therefore selected as the main optical material for the next generation of lithography apparatus operating at wavelength of 157 nm. The growth of large sized $CaF_2$ single crystals with the required properties for this optical application can be achieved only by optimizing the crystal growth process by the aid of numerical simulation. This needs especially a precise calculation of the heat transport and temperature distribution in the solid and liquid $CaF_2$ under crystal growth conditions. As $CaF_2$ is considered to be semitransparent, the internal radiative heat transfer in $CaF_2$ plays an decisive role in the simulation of the heat transport. On the other hand it is very difficult to obtain quantitative experimental data for evaluating numerical models as $CaF_2$ is extremely corrosive at high temperatures. In this work we present a newly developed experimental technique to perform temperature measurements in $CaF_2$-crystal as well as in the melt under conditions of crystal growth process. These experimental results are compared to calculated temperature data, which were obtained by using different numerical models concerning the internal heat transfer in semitransparent $CaF_2$. It will be shown, that an advanced model, which was developed by the authors, gives a much better agreement with experimental data as a standard model, which was taken from the literature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.4
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• pp.178-182
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• 2012

The grain growth is very important because of its great influence on the various materials properties. Therefore, in this study, the effects of anisotropic grain boundary energy on grain growth in 2-D have been investigated with a large scale phase field simulation model on PC. A $2000{\times}2000$ grid system and the initial number of grains of about 73,000 were used in the computer simulation. The anisotropic ratio of grain boundary energy, ${\sigma}_{max}/{\sigma}_{min}$, has been varied from 1 to 3. As the anisotropy increased, the grain growth exponent, n, increased from 2.05 to 2.37. The grain size distribution showed a central plateau in the isotropic case, and was changed into no central plateau and the increasing population of very small grains in the anisotropic case, resulting from slowly disappearing grains. Finally, simulated microstructures were compared according to anisotropy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.722-727
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• 2006

Bone fracture healing is one of the important topics in biomechanics, demanding computation simulations due to the difficulty of obtaining experimental or clinical results. In this study, we adopt the design space optimization method which was established by the authors as a tool for the simulation of bone growth using its evolutionary characteristics. As the mechanical stimulus, strain energy density is used. We assume that bone tissues over a threshold strain energy density will be differentiated and bone tissues below another threshold will be resorbed. Under compression and torsion as loadings, the filling process of the defect is well illustrated following the given mechanical criterion. It is shown that the design space optimization is an excellent tool for simulating the evolutionary process of bone growth, which has not been possible otherwise.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.28-34
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• 2006

A procedure of estimating failure probability is demonstrated for a pressurized pipe of CrMo steel used at $538^{\circ}C$. Probabilistic fracture mechanics were employed considering variations of pressure loading, material properties and geometry. Probability density functions of major material variables were determined by statistical analyses of implemented data obtained by previous experiments. Distributions of the major variables were reflected in Monte Carlo simulation and failure probability as a function of operating time was determined. The creep crack growth life assessed by conventional deterministic approach was shown to be conservative compared with those obtained by probabilistic one. Sensitivity analysis for each input variable was also conducted to understand the most influencing variables to the residual life analysis. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.