• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.187-193
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• 2011

In this report, We compared the actual test with the result of pow calculation and Resistance/Self-propulsion of the ship using STAR-CCM+ which is the commercial Reynolds Averaged Navier-Strokes(RANs) Solver. The calculation model was the KRISO Container Ship and 205K Bulk Carrier of Sungdong shipbuilding company. For this calculation, We used Realizable K-Epsilon model for flaw analysis, VOF method for the free surface creation, Moving Reference Frame method for reducing the POW calculation time, and Sliding Mesh method for Self-Propulsion analysis. Calculation of Resistance and Self-Propulsion includes the free-surface. And all calculations in this report were based on unstructured grids.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.111-114
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• 2004

CFD code that simulates stator-rotor interactions is developed applying parallel computing method. Modified Multi-Block Grid System which enhances perpendicularity in grid and is appropriate in parallel processing is introduced and Patched Algorithm is applied in sliding interface which is caused by movement of rotor. The experimental model in the turbo-machine is composed of 11 stators and 14 rotors. Analyses on two test cases which are one stator - one rotor model and three stators - four rotors model are performed. The results of the two cases have been compared with the experimental test data.

• Corrosion Science and Technology
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• v.5 no.1
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• pp.15-22
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• 2006

The introduction of two-grid inside a conventional process system produces a reactive coating deposition and increases metal ion ratio in the plasma, resulting in denser and smoother films. The corrosion behaviors of TiN coatings were investigated by electrochemical methods, such as potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in deaerated 3.5% NaCl solution. Electrochemical tests were used to evaluate the effect of microstructure on the corrosion behavior of TiN coatings exposed to a corrosive environment. The crystal structure of the coatings was examined by X-ray diffractometry (XRD) and the microstructure of the coatings was investigated by scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM). In the potentiodynamic polarization test and EIS measurement, the corrosion current density of TiN deposited by two grid-attached magnetron sputtering was lower than TiN deposited by conventional magnetron type and also presented higher Rct values during 240 h immersion time. It is attributed to the formation of a dense microstructure, which promotes the compactness of coatings and yields lower porosity.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.123-131
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• 2024

Plastic, the main material of FFF-type 3D printing, exhibits lower strength compared to metal. research aimed at increasing strength is needed for use in various industrial fields. This study analyzed three X-shape infill patterns(grid, lines, zigzag) with similar internal lattice structure. Moreover, tensile test considering weight and printing time was conducted based on the infill line multiplier and infill overlap percentage. The three X-shape infill patterns(grid, lines, zigzag) showed differences in nozzle paths, material usage and printing time. When infill line multiplier increased, there was a proportional increase in tensile strength/weight and tensile strength/printing time. In terms of infill overlap percentage, the grid pattern at 50% and the zigzag and lines patterns at 75% demonstrated the most efficient performance.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.2
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• pp.149-158
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• 2023

To predict the aerodynamic characteristics of the grid fins from subsonic to supersonic speeds, low fidelity SW as well as CFD SW were applied. VLM(Vortex Lattice Method) and SE(Shock-Expansion) method were used at subsonic and supersonic speed domain respectively for the rapid prediction of low fidelity SW. For 2 configurations of the grid fins, the CFD computations and tests using the trisonic wind tunnel were also performed to compare the results of the grid fins. The results of low fidelity SW, CFD SW and the wind tunnel tests data were agreed well each other. Through further research on the grid fins, the effective parameters of the grid fin configurations according to the speed regime will be investigated.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.2
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• pp.47-56
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• 2012

Amount of radiation exposure by seeing through fluoroscopy examination while is many patient exposure administration and unprepared misgovernment be. In this study, abdominal fluoroscopy during the scan, the dose and image quality change according to the use of grid and added filter optimized by measuring the test condition is proposed. Uses seeing through fluoroscopy examination equipment of Image Intensifier of Easy Diagnost Eleva (Philips), under tube type and uses Human phantom and measures average area dose according to grid insertion existence and nonexistence and added filter kind change. Measure sum of 29 organ dose and effective dose through PCXMC imagination simulation program and image J program through noise, SNR, image distortion was measured. Resolution, sharpness, and analyzed using the MTF curves. Fluorography the grid to insert the filter thickness and thickening and increased the average area dose and organ doses and effective dose. In the case of spot examination, when inserted grid, average area dose and organ dose and effective dose increased. Filter thickens the average area dose decreased, but the organ doses and effective dose were increased when use 0.2mmCu+1mmAl filter, decreased slightly. Noise and SNR measurements without inserting the gird, if you do not use the added filter was the lowest and when measure the distortion, 0.1mmCu+1mmAl filter was no difference of image quality in case insert grid was judged that when did not use occasion added filter that do not use grid, difference of image quality does not exist. Did not show a big difference, according to the grid and uses of the added filter sharpness, and resolution. Patient dose increases with factors that reduce the quality of the image so reckless grid and the use of the added filter when abdominal fluoroscopy examination should be cautious in using.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.477-486
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• 2010

This Study suggests security directions to reconstruct separate network of Smart Grid and information communication network as one communications system and implement Smart Grid integrated information communication network. In addition, it suggests prevention directions to prevent future cyber attacks by reorganizing network as the key three-stage network and separating TCP/IP four layers that consist of existing information communication network from Smart Grid. Moreover, it suggests the foundation for the study and the test by providing current problems of Smart Grid, weak points, and three security models. This study is meaningful to suggest development directions and situations as a technology of future-oriented electric industries, integrate attacks and preventions of TCP/IP Layers with Smart Grid, and seek for a new technology of Smart Grid and future tasks for Smart Grid information security.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.23-29
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• 2017

In this study, a post-correlation analysis for shaking table test of square water storage tank is presented for the use of advances in earthquake-resistant design of liquid storage tank. For this purpose, the ANSYS CFX program is selected for the CFD analysis. Sensitivity analysis for resonant sloshing motion in terms of grid size and turbulence model suggested that (1) horizontal grid size as well as vertical grid size is a key variable in the sloshing analysis, and (2) the SST turbulence model is best for the sloshing analysis. Finally, correlation analyses for a non-resonant harmonic input and scaled earthquake excitation of the El Centro (1940) NS component are carried out using the grid and turbulence model established through the post-correlation analysis for the resonant motion. As a result, sloshing time histories by the CFD analysis agreed very well with the test results.

• New & Renewable Energy
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• v.5 no.3
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• pp.4-12
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• 2009

The effect of change in DFIG (doubly-fed wind power generator) rotating speed and active power on the grid was analyzed to understand the characteristics of wind power using the wind power simulator connected to the grid at Gochang Power Quality Test Center. Electric power quality improvement devices (DVR, STATCOM, SSTS) and electric power quality disturbance application devices for 22.9 kV grid are equipped at Gochang Power Quality Test Center. Induction motor and VVVF inverter were used to emulate the blade of a wind power generator, and a simulator for Cage wound induction generator and DFIG was developed. The trial line were assumed to be 20 km and 40 km in length, and variable wind speed pattern was set using wind speed data from Ducjeokdo to verify the power characteristics of the wind power generator according to rotating speed.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.1
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• pp.59-65
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• 2013

The signal broadcast from a GPS satellite experiences code delay and carrier phase advance while passing through the ionosphere, which causes a signal error. Many ionosphere models have been studied to correct this ionospheric delay error. In this paper, the ionosphere modeling for the Korean Peninsula was carried out using a spherical harmonics based model. In contrast to the previous studies, we considered a real-time ionospheric delay correction model using fewer number of basis functions. The modeling performance was evaluated by comparing with a grid model. Total number of basis functions was set to be identical to the number of grid points in the grid model. The performance test was conducted using the GPS measurements collected from 5 reference stations during 24 hours. In the test result, the modeling residual error was smaller than that of the existing grid model. However, when the number of measurements was small and the measurements were not evenly distributed, the overall trend was found to be problematic. For improving this problem, we implemented the modeling with additional virtual measurements.