• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.17-24
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• 2003

A mathematical model of the hydrodynamic and heat transfer performances of two-phase flow (gas-liquid) in thin film region of micro channel is proposed. For the formulation of modeling, the flow of the vapor phase and the shear stress at the liquid-vapor interface are considered. In this work, disjoining pressure and capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted also. Using the model, the effects of the variations of channel height and heat flux on the flow and heat transfer characteristics are investigated. Results show that the influence of variation of vapor pressure on the liquid film flow is not negligible. The heat flux in thin-film region is the most important operation factor of micro cooler system.

• Knowledge Management Research
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• v.5 no.2
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• pp.25-51
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• 2004

The purpose of this study is to investigate the knowledge creating pattern of technology catching-up and pioneering phase in the new product development process. This paper first reviews the knowledge conversion, absorptive capability, learning orientation and the trigger of learning. The paper then presents the integrative model of knowledge creating. Based on the integrative model, in-depth case analysis was conducted on the new product development process in Phicom. As a result, the paper discuss that the pattern of absorptive capability building, knowledge conversion and knowledge transfer is different from technology catching-up and pioneering phase. Finally, the implications and limitations of the study are discussed.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.108.1-108.1
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• 2012

Previously we introduced ray-tracing based 3D optical earth system model for specular and scattering properties of all components of the system (i.e. clear-sky atmosphere, land surfaces and an ocean surface). In this study, we enhanced 3-dimensional atmospheric structure with vertical atmospheric profiles for multiple layer and cloud layers using Lambertian and Mie theory. Then the phase dependent disk averaged spectra are calculated. The main results, simulated phase dependent disk averaged spectra and light curves, are compared with the 7 bands(300~1000nm) light curves data of the Earth obtained from High Resolution Instrument(HRI) in Deep Impact spacecraft during Earth flyby in 2008. We note that the results are comparable with the observation.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.23-27
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• 2024

Underwater images are typically degraded due to color distortion, light absorption, scattering, and noise from artificial light sources. Restoration of these images is an essential task in many underwater applications. In this paper, we propose a two-phase deep learning-based method, Underwater Deep Curve Estimation (UWDCE), designed to effectively enhance the quality of underwater images. The first phase involves a white balancing and color correction technique to compensate for color imbalances. The second phase introduces a novel deep learning model, UWDCE, to learn the mapping between the color-corrected image and its best-fitting curve parameter maps. The model operates iteratively, applying light-enhancement curves to achieve better contrast and maintain pixel values within a normalized range. The results demonstrate the effectiveness of our method, producing higher-quality images compared to state-of-the-art methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.243-249
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• 2006

In this paper, the phase noise effects of OFDM transmission diversity systems were analyzed. Since OFDM communication system is very sensitive to phase noise, the system performance may degrade seriously due to the increase of subcarrier interferences and system noise. Therefore, The phase noise model was suggested and its distribution and power were varied to investigate the effects of phase noise on the system performance. The degree of the system performance degradation depends on the specific diversity structures of transmission systems. Here, the performances of OFDM systems with two and three antennas transmission diversity were analyzed and compared with that of systems without transmission diversity as the phase noise characteristics varied.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.864-867
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• 1995

Presented in the paper is a structured approach to modeling automated manufacturing system (AMS) in the form of an event graph. The proposed two-phase procedure for formal modeling is 1) reference modeling by schematic supervisory control modeling and 2) event graph transformation from supervisory control model. Also described is a formal model for a small-sized FMS in the form of an event graph.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.127-131
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• 2001

The effect of grain shape on the grain growth behavior of oxide system was investigated as afunction of liquid content during liquid phase sintering. As a model system, the solid grains of $Al_{2}O_{3}$ and MgO were selected during liquid phase sintering, i.e. faceted shape of $Al_{2}O_{3}$ in $CaAl_{2}Si_{2}O_{8}$ liquid phase and spherical shape of MgO in $CaMgSiO_{4}$ liquid phase. The average grain size of MgO with spherical shape was decreased with increasing the liquid phase content, whereas that of $Al_{2}O_{3}$ with faceted shape was independent of liquid phase content. In the case of $Al_{2}O_{3}$ grains with faceted shape, which interfaces are expected to be atomically flat, are likely to grow by the interfacial reaction controled process. Whereas, in the case of MgO grains with spherical shape, which interface are expected to be atomically rough, are likely to grow by the diffusion controlled process.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.3
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• pp.133-140
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• 2018

This paper is concerned with the 2-D micostructure generation for $Ni-A{\ell}_2O_3$ dual-phase composite materials and the numerical analysis of mechanical characteristic of hierarchical models of microstructure which are defined in terms of the scale of microstructure. The microstructures of dual-phase composite materials were generated by applying the mathematical RMDF(random morphology description functions) technique to a 2-D RVE of composite materials. And, the hierarchical models of microstructure were defined by the number of Gaussian points. Meanwhile, the volume fractions of metal and ceramic particles were set by adjusting the level of RMD functions. The microstructures which were generated by RMDF technique are definitely random even though the total number of Gaussian points is the same. The randomly generated microstructures were applied to a 2-D beam model, and the variation of normal and shear stresses to the scale of microstructure was numerically investigated. In addition, through the crack analyses, the influence of RMDF randomness and Gauss point number on the crack-tip stress is investigated.

• 한국해양학회지
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• v.28 no.2
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• pp.86-100
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• 1993

Three-dimensional baroclinic hydrodynamic model, BACHOM-3, is developed using ADI finite difference scheme. The model is applied to a uni-nodal standing wave in a rectagular basin. The model results for the surface elevation and velocities coincide with the analytical results. To verify the field applicability of the model and to investigate the flow patterns of the Suyoung Bay in Pusan, Korea, the model is applied to the bay. The numerically predicted velocity predicted velocity fields during spring tide at normal river flow are compared with field measurements, the comparisons show good agreement. A clockwise residual circulations at the first level (depth = 0∼2m) and the second level (depth=2∼5 m) of the central part of the bay occur, and the ebb flow is stronger than the flood flow. Computed velocity fields show that the phase difference of velocities between the surface layer and bottom layer occurs and the phase lag increases with height from the bottom. Then, the model is applied successfully for the computation of flow fields considering flood river flow and wind effects. When the wind is blowing toward the land from the sea, the flow patterns at the surface layer correspond with the wind direction, but the flow patterns at the near solid boundary of the lower layer show opposite currents to the wind direction.

• Journal of The Korean Astronomical Society
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• v.50 no.2
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• pp.21-27
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• 2017

The autoregressive method provides a univariate procedure to predict the future sunspot number (SSN) based on past record. The strength of this method lies in the possibility that from past data it yields the SSN in the future as a function of time. On the other hand, its major limitation comes from the intrinsic complexity of solar magnetic activity that may deviate from the linear stationary process assumption that is the basis of the autoregressive model. By analyzing the residual errors produced by the method, we have obtained the following conclusions: (1) the optimal duration of the past time for the forecast is found to be 8.5 years; (2) the standard error increases with prediction horizon and the errors are mostly systematic ones resulting from the incompleteness of the autoregressive model; (3) there is a tendency that the predicted value is underestimated in the activity rising phase, while it is overestimated in the declining phase; (5) the model prediction of a new Solar Cycle is fairly good when it is similar to the previous one, but is bad when the new cycle is much different from the previous one; (6) a reasonably good prediction of a new cycle can be made using the AR model 1.5 years after the start of the cycle. In addition, we predict the next cycle (Solar Cycle 25) will reach the peak in 2024 at the activity level similar to the current cycle.