• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.868-877
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• 2011

This paper presents a parallel computing methodology for polymer electrolyte fuel cells (PEFCs) and detailed simulation contours of a real-scale fuel cell. In this work, a three-dimensional two-phase PEFC model is applied to a large-scale 200 $cm^2$ fuel cell geometry that requires roughly 13.5 million grid points based on grid-independence study. For parallel computing, the large-scale computational domain is decomposed into 12 sub-domains and parallel simulations are carried out using 12 processors of 2.53 GHz Intel core i7 and 48GB RECC DDR3-1333. The work represents the first attempt to parallelize a two-phase PEFC code and illustrate two-phase contours in a representative industrial cell.

• Computers and Concrete
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• v.20 no.6
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• pp.627-634
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• 2017

Predicting the compressive strength of concrete is important to assess the load-carrying capacity of a structure. However, the use of blended cements to accrue the technical, economic and environmental benefits has increased the complexity of prediction models. Artificial Neural Networks (ANNs) have been used for predicting the compressive strength of ordinary Portland cement concrete, i.e., concrete produced without the addition of supplementary cementing materials. In this study, models to predict the compressive strength of blended cement concrete prepared with a natural pozzolan were developed using regression models and single- and 2-phase learning ANNs. Back-propagation (BP), Levenberg-Marquardt (LM) and Conjugate Gradient Descent (CGD) methods were used for training the ANNs. A 2-phase learning algorithm is proposed for the first time in this study for predictive modeling of the compressive strength of blended cement concrete. The output of these predictive models indicates that the use of a 2-phase learning algorithm will provide better results than the linear regression model or the traditional single-phase ANN models.

• Journal of Korea Soil Environment Society
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• v.5 no.1
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• pp.3-12
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• 2000

The multi-region model, to describe preferential flow, is an equation representing solute transport in soils by dividing soil into numerous pore groups and using the hydraulic properties of the soil. As the model partial differential equation (PDE) is solved numerically with finite difference methods. a modified equivalent partial differential equation(MEPDE) of the partial differential equation of the multi-region model is derived to analyze the accuracy and consistency of the solution of the model PDE and the Von Neumann method is used to analyze the stability of the finite difference scheme. The evaluation obtained from the MEPDE indicated that the finite difference scheme was found to be consistent with the model PDE and had the second order accuracy The stability analysis is performed to analyze the model PDE with the amplification ratio and the phase lag using the Von Neumann method. The amplification ratio of the finite difference scheme gave non-dissipative results with various Peclet numbers and yielded the most high values as the Peclet number was one. The phase lag showed that the frequency component of the finite difference scheme lagged the true solution. From the result of the stability analysis for the model PDE, it is analyzed that the model domain should be discretized in the range of Pe < 1.0 and Cr < 2.0 to obtain the more accurate solution.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.7-17
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• 1998

This study is to develop the consequence modeling methodology for quantitative prediction of the hazard distance(or toxic buffer distance) for two-phase flow continuous releases from the pressurized chlorine saturated liquid storage tank of the chemical plant facilities. The source term modeling was peformed by the refined analysis method based on USEPA's guideline and SuperChems model self-calculation, respectively. The hazard distance was predicted for STEL, IDLH and ERPGs(ERPG-2 and ERPG-3) concentrations being used as the toxic regultaion concentration in hazard estimation. To use as hazard estimation guideline for the establishment of the emergency response planning, the effects of source characteristics and meteorological vaiations on the hazard distance was especially considered for ERPG-2 concentration.

• Bulletin of the Korean Mathematical Society
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• v.41 no.2
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• pp.283-297
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• 2004

We have obtained a simplified model for the mush under the assumption of the temperature, the solid fraction and the vertical component of the velocity, depend on upward coordinate z only. We have found solutions in the asymptotical limit and solved numerically for the model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1301-1309
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• 1989

본 연구의 목적은 Lumley의 저항감소 모델을 사용하여 여러 부하도하에서 부유유동의 유동 특성을 관찰하는 것으로, 특히 저항감소가 일어날 때와 일어나지 않을 때의 유동특성을 알아 보고자 한다.

• 한국해양학회지
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• v.15 no.2
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• pp.112-122
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• 1980

A two-dimensional non-linear tidal model has been established to calculate the M$\_$2/ tide of Inchon Bay in the west coast of Korea. Cartesian coordinates are used for the derivation of the governing equations and account is taken of extensive drying boundaries (tidal flats) which are exposed at low tides. The tidal amplitudes and phases computed from the model agree well with those known from observation lying within bounds 5cm in amplitude and 5 in phase relative to the observed results. The work represents a further stage in the development including extensive sea measurements capable of application in various coastal engineering problems encountered in Inchon Bay area.

• Journal of KIBIM
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• v.5 no.2
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• pp.1-11
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• 2015

Despite a lot of research on BIM, there is no quantitative study to measure accurately the performance of BIM coordination service. Thus, this study suggested method to measure the performace of BIM coordination services, applying queueing models in the field of management science. To analyze queuing system of BIM coordination services, a group of BIM coordinator were selected. Through focus group interviews with experts were used in the analysis to derive mean arrival rate(${\lambda}$), mean service rate(${\mu}$) of BIM coordination services. Single-server queuing model(M/M/1), multiple server queuing model(M/M/s) is utilized for the BIM coordination services performance measurement in construction phase. This study has significant quantitative performance measurement approaches that can be utilized in the decision-making for the improvement of the BIM coordination services and to support the review of the alternatives accordingly. But There is a limit but it is difficult to take into account the increase or decrease of the cost of alternatives according to the review.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.962-975
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• 2020

The accurate segmentation of infant brain MR image into white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) is very important for early studying of brain growing patterns and morphological changes in neurodevelopmental disorders. Because of inherent myelination and maturation process, the WM and GM of babies (between 6 and 9 months of age) exhibit similar intensity levels in both T1-weighted (T1w) and T2-weighted (T2w) MR images in the isointense phase, which makes brain tissue segmentation very difficult. We propose a deep network architecture based on U-Net, called Triple Residual Multiscale Fully Convolutional Network (TRMFCN), whose structure exists three gates of input and inserts two blocks: residual multiscale block and concatenate block. We solved some difficulties and completed the segmentation task with the model. Our model outperforms the U-Net and some cutting-edge deep networks based on U-Net in evaluation of WM, GM and CSF. The data set we used for training and testing comes from iSeg-2017 challenge (http://iseg2017.web.unc.edu).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.682-686
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• 2015

The objective of this study is to validate the performance of the current $k-{\epsilon}$ turbulence model for a single-phase turbulent natural convection, which has been considered an important phenomenon in nuclear safety. As a result, the natural convection problems in the 2D and 3D cavities previously studied are calculated by using the ANSYS Fluent software. The present results show that the current $k-{\epsilon}$ turbulent model accounting for the buoyancy effect is in good agreement with the previous results for the natural convection problems in the 2D and 3D cavities although some improvements should be required to get better prediction.