• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.42-46
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• 2009

For understanding of high performance liquid rocket engine operating at high pressure, dynamic characteristics of liquid oxygen in a swirl injector operating at supercritical conditions has been numerically investigated. Turbulent numerical model is based on large eddy simulation and contains full conservation laws including Soave modification of Redlich-Kwong equation of state and Chung's model. Preconditioning method is applied to get an effective convergence rate. Numerical analysis results are compared with the one that ideal equation of state applied to. Differences of thermodynamic properties and mixing dynamics are investigated at liquid phase area inside injector and combustion chamber.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.919-921
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• 2015

The edge is widely utilized as a preconditioning process in order to simplify the images in several fields such as the object recognition and detection. The edge detection methods which are generally known include the methods of Sobel, Roberts and Laplacian. However, such current methods have an advantage that the implementation is simple but bring more less an insufficient result since they use the fixed weighting mask. Therefore, an algorithm using the modified morphology is proposed in order to supplement such problems of the current edge detection methods and obtain the excellent edge detection, and also a simulation using this algorithm is conducted to compare with such current methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.267-269
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• 2015

In the modern society, the images provide the most effective information in multi-devices and the edge includes important feature information in such images. This edge is used as an essential preconditioning process in several application fields and many studies have been carried out in order to obtain the excellent images. The methods of Sobel and Roberts which are generally known are simple to implement the images but bring more or less insufficient processing result. Thus, this paper proposed an edge detection algorithm using the area averaging of segmented mask in order to supplement the problems of the current methods and compared it with such current methods.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.205-205
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• 2005

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.551-553
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• 2002

The cubicle type GIS rated at 25.8kV has been designed and manufactured by Jinkwang E&C eacently with their own technologies and KERI's assistances. The C-GIS has been tested to check the design capability for reference before conducting the type test. The operating characteristics test, short time withstand current and peak withstand current test, basic short circuit test duty T60 for preconditioning test, cable charging current switching test, capacitor bank current switching test, basic short circuit test duty T100s and T100a, single phase earth fault test, double earth fault test has been conducted. The test results show that the design and the manufacturing of the C-GIS has an enough capability to pass through the type test except the occurrence of 2 NSDDs in the cable charging current switching test and the instability of opening time at the minimum operating voltage. The problems shown in the tests will be improved soon and the successful pass will be expected in the following type test.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.10-18
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• 2016

Numerical boundary conditions are as important as the governing equations when analyzing the fluid flows numerically. An explicit boundary condition method updates the solutions at the boundaries with extrapolation from the interior of the computational domain, while the implicit boundary condition method in conjunction with an implicit time integration method solves the solutions of the entire computational domain including the boundaries simultaneously. The implicit boundary condition method, therefore, is more robust than the explicit boundary condition method. In this paper, steady compressible 2-Dimensional Navier-Stokes solver is developed. We present the implicit boundary condition method coupled with LU-SGS(Lower Upper Symmetric Gauss Seidel) method. Also, the explicit boundary condition method is implemented for comparison. The preconditioning Navier-Stokes equations are solved on unstructured meshes. The numerical computations for a number of flows show that the implicit boundary condition method can give accurate solutions.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.258-270
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• 2020

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.148-151
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• 2003

Seeds of broomrape (Orobanche cernua) were exposed to 0, 25, 50, 75, and 100 mM NaCl solutions during their preconditioning period (14 days of moisture) under laboratory conditions and induced to germinate by synthetic germination stimulant (GR24). There was significant reduction in seed germination with increased salt concentration as shown in 35.2, 32.5, 23.6, 14.3, and 9.2% germination, respectively. Exposure of Orobanche cernua seeds to 0.0, 1.0, 1.25, and 1.5 M levels of NaCl for 9 hours resulted in 29.4, 21.3, 20.5, and 17.4% germination, respectively. Water preconditioned seeds showed Heavier protein profile bands of 6.5-14.2 KDa than those of dry seeds. Seeds treated with 0.75 M NaCl showed profile similar with that of water preconditioned ones, plus an extra band at 29-36 KDa. The protein profiles of 1.0 and 1.5 M NaCl treated seeds showed weaker bands with the absence of 29-36 KDa band.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.25-32
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• 2012

This work was devoted to compare two different cavitation models to study the dependency of model constants. The cavitation model of Merkle et al.(2006) and Kunz et al.(2000) were used for the present computational study. The cavitation models were coupled with the incompressible unsteady Reynolds-Averaged Navier-Stokes solver to indicate the vaporization and condensation processes. For this purpose, a preconditioning method was added as the pseudo-time term to solve the unsteady stiffness problems. For the validation of the numerical simulation, the computation was performed for the cavitating flow in a converging-diverging channel. The present results show that Merkle's cavitation model is independent to the model constants, and the higher numerical accuracy over Kunz's cavitation model.

• Journal of computational fluids engineering
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• v.19 no.2
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• pp.17-23
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• 2014

Cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency in devices, such as propellers, pump impellers, nozzles, injectors, torpedoes, etc. Thus, the cavitating flow simulation is of practical importance for many engineering systems. In the present work, a two-phase flow solver based on the homogeneous mixture model has been developed. The solver employs an implicit preconditioning, dual time stepping algorithm in curvilinear coordinates. The flow characteristics around Clark-Y hydrofoil were calculated and then validated by comparing with the experimental data. The lift and drag coefficients with changes of angle of attack and cavitation number were obtained. The results show that cavity length and lift, drag coefficient increase with increasing angle of attack.