• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.853-862
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• 2018

An adaptive cut-cell grid based 2D inundation analysis model, K-Flood, is developed in this study. Cut cell grid method divides a grid into a flow area and a non-flow area depending the characteristics of the flows. With adaptive mesh refinement technique cut cell method can represent complex flow area using relatively small number of cells. In recent years, the urban inundation modeling using high resolution and fine quality data is increasing to achieve more accurate flood analysis or flood forecasting. K-Flood has potential to simulate such complex urban inundation using efficient grid generation technique. A finite volume numerical scheme of second order accuracy for space and time was applied. For verification of K-Flood, 1) shockwave reflex simulation by circular cylinder, 2) urban flood experiment simulation, 3) Malpasset dam collapse simulation are performed and the results are compared with observed data and previous simulation results.

• Toxicological Research
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• v.18 no.3
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• pp.227-232
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• 2002

In order to find out the appropriate in vitro method for high correlation with in vivo, we com-pared the sensitivities of phototoxicity (PT) in vitro method between in human keratinocytes, HaCaT cells and in 3T3 fibroblast cells derived from Balb/c mice. Both cells were exposed to six known phototoxic chemicals : promethazine, neutral red, chlortetracycline, amiodarone, bithionol, 8-methoxypsoralen, or non-phototoxic chemical, ALS (ammonium laureth sulfate) and then irradiated with 5 J/$cm^2$ of UVA. Cell viability ($IC_{50}$ ) was measured by neutral red uptake (NRU) assay. The ratio of $IC_{50}$ value of chemicals in the presence and absence of UVA was determined by the cut-off value. The phototoxic potential of test chemicals in NRU assay was determined by measuring the photoirriation factor (PIF) with a cut-off value of 5. In both 3T3 and HaCaT cells, all known phototoxic chemicals were positive (over 5 of PIF value), except that bithionol was found to be non-phototoxic to HaCaT cells, and ALS, non-phototoxic chemical was negative. These results suggest that Balb/c 3T3 cell was more sensitive than HaCaT cell to predict phototoxicity potential.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.121-129
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• 2009

In this study, dam-break flows are simulated numerically by using an efficient and accurate Cartesian cut-cell mesh system. In the system, most of the computational domain is discretized by the Cartesian mesh, while peculiar grids are done by a cutcell mesh system. The governing equations are then solved by the finite volume method. An HLLC approximate Riemann solver and TVD-WAF method are employed to calculation of advection flux of the shallow-water equations. To validate the numerical model, the model is applied to some problems such as a steady flow convergence on an ideal bed, a steady flow over an irregular bathymetry, and a rectangular tank problem. The present model is finally applied to a simulation of dam-break flow on an experimental channel. The predicted water surface elevations are compared with available laboratory measurements. A very reasonable agreement is observed.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.1
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• pp.103-113
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• 2019

Motivation: Polymerized actin-based cytoskeletal structures are crucial in shape, dynamics, and resilience of a cell. For example, dynamical actin-containing ruffles are located at leading edges of cells and have a significant impact on cell motility. Other filamentous actin (F-actin) bundles, called stress fibers, are essential in cell attachment and detachment. For this reason, their mechanistic understanding provides crucial information to solve practical problems related to cell interactions with materials in tissue engineering. Detecting and counting actin-based structures in a cellular ensemble is a fundamental first step. In this research, we suggest a new method to characterize F-actin wrapping fibers from confocal fluorescence image stacks. As fluorescently labeled F-actin often envelope the fibers, we first propose to segment these fibers by diminishing an energy based on maximum flow and minimum cut algorithm. The actual actin is detected through the use of bilateral filtering followed by a thresholding step. Later, concave actin bundles are detected through a graph-based procedure that actually determines if the considered actin filament is enclosing the fiber.

• Journal of KIISE:Software and Applications
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• v.33 no.8
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• pp.681-691
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• 2006

Clustering is one of widely used methods for grouping thousands of genes by their similarities of expression levels, so that it helps to analyze gene expression profiles. This method has been used for identifying the functions of genes. Fuzzy clustering method, which is one category of clustering, assigns one sample to multiple groups according to their degrees of membership. This method is more appropriate for analyzing gene expression profiles because single gene might involve multiple genetic functions. Clustering methods, however, have the problems that they are sensitive to initialization and can be trapped into local optima. To solve these problems, this paper proposes an evolutionary fuzzy clustering method, where adaptive a-cut based evaluation is used for the fitness evaluation to apply different criteria considering the characteristics of datasets to overcome the limitation of Bayesian validation method that applies the same criterion to all datasets. We have conducted experiments with SRBCT and yeast cell-cycle datasets and analyzed the results to confirm the usefulness of the proposed method.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.419-424
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• 2001

TCV(Temperature control valve by pressure compensation) controls temperature constantly, when it is sending steam or high temperature water to heating device of heat exchanger. For designing TCV, the ratio of piston and hole diameters is one of the important design parameters. Numerical analysis is carried out to elucidate the flow characteristics in the TCV with different port areas of cold and hot waters, using the k-$\epsilon$ turbulence model and Cartesian cut-cell method. Numerical results show that the exit flow rate is mainly affected by pressure distribution in the piston.

• Korean Journal of Computational Design and Engineering
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• v.13 no.6
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• pp.450-458
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• 2008

Recently, Cartesian grid approach has been popular to generate grid meshes for complex geometries in CFD (Computational Fluid Dynamics) because it is based on the non-body-fitted technique. This paper presents a method of an octree generation and boundary cell clipping using section curves for fast octree generation and elimination of redundant intersections between boundary cells and triangles from 3D triangular mesh. The proposed octree generation method uses 2D Scan-Converting line algorithm, and the clipping is done by parameterization of vertices from section curves. Experimental results provide octree generation time as well as Cut-cell clipping time of several models. The result shows that the proposed octree generation is fast and has linear relationship between grid generation time and the number of cut-cells.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.188-195
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• 2010

Green water load is an important parameter to be considered in designing a modern ship or offshore structures like FPSO and FSRU. In this research, a numerical simulation method for green water phenomenon is introduced. The Navier-Stokes equations and the continuity equation are used as governing equations. The equations are calculated using Finite Difference Method(FDM) in rectangular staggered grid system. To increase the numerical accuracy near the body, the Cartesian cut cell method is employed. The nonlinear free-surface during green water incident is defined by Marker-density method. The green waters on a box in regular waves are simulated. The simulation results are compared with other experimental and computational results for verification. To check the applicability to moving ship, the green water of the ship which is towed by uniform force in regular wave, is simulated. The ship is set free to heave and to surge.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1157-1166
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• 2021

In this study, a numerical sensitivity analysis was performed to determine the fire suppression time for a large number of water mist nozzles in a large fire compartment. Fire simulations were performed using FDS (Fire dynamics simulator) 6.5.2 under the same condition as the test scenario 5 of the International Maritime Organization (IMO) 1165 test protocol. The sensitivities of input parameters including cell size, extinguishing coefficient (EC), droplets per second (DPS), and peak heat release rate (HRR) of fuel were investigated in terms of the normalized HRR and temperature distribution in the compartment. A new method of determining the fire suppression time using FDS simulation was developed, based on the concept of the cut-off time by cut-off value (COV) of the heat release rate per unit volume (HRRPUV) and the cooling time by the HRR cooling time criteria value (CTCV). In addition, a method was developed to determine the average EC value for the simulation input, using the cooling time and cut-off time.

• Journal of Korea Water Resources Association
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• v.44 no.7
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• pp.511-522
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• 2011

Two-dimensional shallow water model based on the cut cell and the adaptive mesh refinement techniques is presented in this paper. These two mesh generation methods are combined to facilitate modeling of complex geometries. By using dynamically adaptive mesh, the model can achieve high resolution efficiently at the interface where flow changes rapidly. The HLLC Reimann solver and the MUSCL method are employed to calculate advection fluxes with numerical stability and precision. The model was applied to simulate the extreme urban flooding experiments performed by the IMPACT (Investigation of Extreme Flood Processes and Uncertainty) project. Simulation results were in good agreement with observed data, and transient flows as well as the impact of building structures on flood waves were calculated with accuracy. The cut cell method eased the model sensitivity to refinement. It can be concluded that the model is applicable to the urban flood simulation in case the effects of sewer and stormwater drainage system on flooding are relatively small like the dam brake.