• Journal of the Society of Naval Architects of Korea
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• v.52 no.5
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• pp.407-417
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• 2015

For the more accurate prediction on manoeuvring performance of a ship at initial design phase, bare hull manoeuvring coefficients were estimated by RANS(Reynolds Averaged Navier-Stokes) based virtual captive model tests. Hydrodynamic forces and moment acting on the hull during static drift and harmonic oscillatory motions were computed with a commercial RANS code STAR-CCM+. Automatic and consistent mesh generation could be implemented by using macro functions of the code and user dependency could be greatly reduced. Computed forces and moments on KCS and KVLCC 1&2 were compared with the corresponding measurements from PMM(Planar Motion Mechanism) tests. Quite good agreement can be observed between the CFD and EFD results. Manoeuvring coefficients and IMO standard manoeuvres estimated from the computed data also showed reasonable agreement with those from the experimental data. Based on these results, we could confirm that the developed virtual captive manoeuvring model test process could be applied to evaluate manoeuvrability of a ship at the initial hull design phase.

• Journal of the Korean Applied Science and Technology
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• v.21 no.2
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• pp.132-139
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• 2004

Film forming behavior of monodispersed model composite latexes with particle size of 190 nm, which consist of n-butyl acrylate as a soft phase monomer and methyl methacrylate as a hard phase monomer with different morphology was examined. Five different types of model latexes were used in this study such as random copolymer particle, soft-core/hard-shell particle, hard-core/soft-shell particle, gradient type particle, and mixed type particle. The film forming behavior was evaluated using pseudo on-line measurements of the cumulative weight loss, the UV transmittance, and the tensile fracture energy. Each stages of film formation I, II were not sensitive to the morphology of model latexes, but stage-ill was largely dependent on the morphology of model latexes. The chain mobility of polymer which composed the shell component was found to dominantly determine the behavior of film forming stage-III.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.47-52
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• 2014

A simple RC circuit model of large-scale touch screen panels is developed and the frequency range of the RC model is analyzed. 2D EM simulation results of a single touch cell are cascaded for a 23 inch touch panel using a circuit simulator, and the shortest and longest channels of the full panel are modeled with a 5-element RC circuit. The 5-element RC circuit can model the touch screen panel upto 130 kHz with the channel phase error of $10^{\circ}$. 7-element RC circuit model is also proposed and the frequency range for the channel phase error of $10^{\circ}$ is extended to 200 kHz.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.46.2-46.2
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• 2019

We propose a deep learning model that can generate a waveform of coalescing binary black holes in merging and ring-down phases in less than one second with a graphics processing unit (GPU) as an approximant of gravitational waveforms. Up to date, numerical relativity has been accepted as the most adequate tool for the accurate prediction of merger phase of waveform, but it is known that it typically requires huge amount of computational costs. We present our method can generate the waveform with ~98% matching to that of the status-of-the-art waveform approximant, effective-one-body model calibrated to numerical relativity simulation and the time for the generation of ~1500 waveforms takes O(1) seconds. The validity of our model is also tested through the recovery of signal-to-noise ratio and the recovery of waveform parameters by injecting the generated waveforms into a public open noise data produced by LIGO. Our model is readily extendable to incorporate additional physics such as higher harmonics modes of the ring-down phase and eccentric encounters, since it only requires sufficient number of training data from numerical relativity simulations.

• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.41-46
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• 1987

When barium titanate was synthesized in soild-solid reaction the abnormal expansion occurred from 900$^{\circ}C$ to 1100$^{\circ}C$. The equi-molecular mixture of BaCO3 and TiO2 was sintered from 800$^{\circ}C$ to 1300$^{\circ}C$ on the condition of air, vacuum and CO2 atmosphere. After that the specimens were tested closely with XRD, Dilatometer, SEM and EDS. The result indicated that; 1. The crystal phase which was concerned with expansion of BaTiO3 was Ba2TiO4 as the intermediate crystal phase. 2. The formation of Ba2TiO4 was affected by the firing atmosphere. 3. The expansion occurred when BaTiO3 changed to Ba2TiO4 and pore also expanded by the expansion of BaTiO3 body just as the model of expansion.

• Journal of Distribution Science
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• v.13 no.1
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• pp.57-70
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• 2015

Purpose - Open source software has high utilization in most of the server market. The utilization of open source software is a global trend. Particularly, Internet infrastructure and platform software open source software development has increased rapidly. Since 2003, the Korean government has published open source software promotion policies and a supply promotion policy. The dynamism of the open source software market, the lack of relevant expertise, and the market transformation due to reasons such as changes in the relevant technology occur slowly in relation to adoption. Therefore, this study proposes an assessment model of services provided in an open source software service company. In this study, the service level of open source software companies is classified into an enterprise-level assessment area, the service level assessment area, and service area. The assessment model is developed from an on-site driven evaluation index and proposed evaluation framework; the evaluation procedures and evaluation methods are used to achieve the research objective, involving an impartial evaluation model implemented after pilot testing and validation. Research Design, data, and methodology - This study adopted an iteration development model to accommodate various requirements, and presented and validated the assessment model to address the situation of the open source software service company. Phase 1 - Theoretical background and literature review Phase 2 - Research on an evaluation index based on the open source software service company Phase 3 - Index improvement through expert validation Phase 4 - Finalizing an evaluation model reflecting additional requirements Based on the open source software adoption case study and latest technology trends, we developed an open source software service concept definition and classification of public service activities for open source software service companies. We also presented open source software service company service level measures by developing a service level factor analysis assessment. The Behavior-Structure-Evolution Evaluation Model (BSEM) proposed in this study consisted of a rating methodology for calculating the level that can be granted through the assessment and evaluation of an enterprise-level data model. An open source software service company's service comprises the service area and service domain, while the technology acceptance model comprises the service area, technical domain, technical sub-domain, and open source software name. Finally, the evaluation index comprises the evaluation group, category, and items. Results - Utilization of an open source software service level evaluation model For the development of an open source software service level evaluation model, common service providers need to standardize the quality of the service, so that surveys and expert workshops performed in open source software service companies can establish the evaluation criteria according to their qualitative differences. Conclusion - Based on this evaluation model's systematic evaluation process and monitoring, an open source software service adoption company can acquire reliable information for open source software adoption. Inducing the growth of open source software service companies will facilitate the development of the open source software industry.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.153-156
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• 2010

The effective thermal conductivity of two-phase materials such as unbonded silica sands saturated with a nanofluid was measured at high temperature using the transient thermal probe method. The nanofluid used in this study was a water-based mixture of 0.1 vol% $Al_2O_3$ nanoparticles with a diameter of 45 nm. The convection problem for fluids was prevented with this measurement method because the fluid was confined to within very small pore spaces. Based on the prediction model for unbonded sands, the thermal conductivities of the saturating nanofluid at high temperatures could be determined with the measured effective thermal conductivities for the two-phase material. In the results, increases in the thermal conductivity ratios of the nanofluid to pure water when temperatures were varied from $30^{\circ}$ to $80^{\circ}C$ were within the range of 4.87%~5.48%.

• Journal of the Korean earth science society
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• v.29 no.1
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• pp.60-77
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• 2008

We investigated the textbook model explaining a phase of the Moon and compared it with student models at the secondary levels in Korea. 20 high school students and 36 middle school students from suburb area participated in this study. Participants were interviewed to explain understandings about the cause of the Moon's phase with drawing their models. The results of this study showed that the textbooks now in use explain the phase of the Moon with one unique scientific model, while students displayed 6 different kinds of models including the scientific model. Furthermore the students tend to have comparatively scientific model modes as their grades increase and their scholastic ability levels become higher. Although the students have learned the Moon's phase in school, they still have alternative models because the textbook does not explain enough for the students to overcome their alternative conceptions. In the textbook, the model presented without explanation of the limitation of the model, so there can be a gap between the model in the textbooks and the models in the mind of students. With these findings, we propose complementary models for helping secondary school students to develop their understanding of moon phases.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.23-33
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• 1995

Geographic data which are difficult to handle by the characteristics of spatial variation and variety turned into a possibility to analyze with tlie computer-aided digital map and the use of Geographic Information System(GIS). The purpose of this study is to develop and apply a GIS application model (GISCELWAB) for the spatial simulation of surface runoff from a small watershed. This paper discribes the modeling procedure and the applicability of the cell water balance model (CELWAB) which calculates the water balance of a cell and simulates surface runoff of watershed simultaneously by the interaction of cells. The cell water balance model was developed to simulate the temporal and spatial storage depth and surface runoff of a watershed. The CELWAB model was constituted by Inflow-Outflow Calculator (JOC) which was developed to connect cell-to-cell transport mechanism automatically in this study. The CELWAB model requests detail data for each component of a cell hydrologic process. In this study, therefore, BANWOL watershed which have available field data was selected, and sensitivity for several model parameters was analyzed. The simulated results of surface runoff agreed well with the observed data for the rising phase of hydrograph except the recession phase. Each mean of relative errors for peak discharge and peak time was 0.21% and2.1 1% respectively. In sensitivity analysis of CELWAB , antecedent soil moisture condition(AMC) affected most largely the model.

• Journal of Power Electronics
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• v.17 no.2
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• pp.422-431
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• 2017

The equivalent circuit of a three-leg, four-wire voltage source converter (VSC) is derived using switching functions. Simulations and experiments are conducted (i) to investigate the effects of the zero sequence on VSCs when a three-phase imbalance exists and (ii) to use the consistency of simulations and laboratory experiments to validate the equivalent circuit. The impact of a three-phase imbalance on the VSC has yet to be fully investigated because of the lack of an equivalent circuit to show rigorously how the zero sequence currents flow through the VSC.