• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.289-301
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• 2010

A structural model of the SNF(spent nuclear fuel) disposal canister for the PWR(pressurized water reactor) for about 10,000 years long term deposition at a 500m deep granitic bedrock repository has been developed through various structural safety evaluations. The SNF disposal baskets of this canister model have the array type of which four square cross section baskets stand parallel to each other and symmetrically with respect to the center of the canister section. However whether this developed structural model of the SNF disposal canister is best is not determinable yet, because the SNF disposal canister with this parallel array has a limitation in shortening the diameter for the weight reduction due to the shortest distance between the outer corner of the square section and the outer shell. Therefore, the structural safety evaluation of the SNF disposal canister with the rotated basket array which is also symmetric with respect to the canister center planes is very necessary. Even though such a canister model has not been found as yet in the literature, the structural analysis of the canister with the rotated basket array for the PWR is required for the comparative study of the structural safety of canister models. Hence, the structural analysis of the canister with the rotated basket array in which each basket is rotated with a certain amount of degrees around the center of the basket itself and arrayed symmetrically with respect to the center planes is carried out in this paper. The structural analysis result shows that the SNF disposal canister with the rotated basket array in which the SNF disposal basket is rotated as 30~35 degrees around the center of the basket itself is structurally more stable than the previously developed SNF disposal canister with the parallel basket array.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.979-986
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• 2010

This paper presents an algorithm for retrieving precise radar cross sections(RCS) of various trihedral corner reflectors (TCR) which are external calibrators of synthetic aperture radar(SAR) systems. The theoretical RCSs of the TCRs are computed based on the physical optics(PO), geometrical optics(GO), and physical theory of diffraction(PTD) techniques; that is, the RCS computation includes the single reflections(PO), double reflections(GO-PO), triple reflections(GO-GO-PO), and edge diffractions(PTD) from the TCR. At first, we acquire an SAR image of the area that five TCRs installed in, and then extract the RCS of the TCRs. The RCSs of the TCRs are extracted accurately from the SAR image by adding up the power spill, which is generated due to the radar IRF(Impulse Response Function), using a square window. We compare the extracted RCSs with the theoretical RCSs and analyze the difference between the theoretical and experimental RCSs of the TCR for various window sizes and various backscattering coefficient levels of the adjacent area. Finally, we propose the minimum size of the integration area and the maximum level of the backscattering coefficients for the adjacent area.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.130-137
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• 2017

Due to the economic growth and development of construction technology, a role of foundation to resist heavy loads has been increased. In this present study to improve the structural performance of reinforced concrete pile, the precast HPC pile reinforced with rebar and filling concrete was developed and the strength of pile was predicted based on the limit state design method. The safety of HPC pile strength was evaluated by comparing with the design values. The geometry of HPC pile is a decagon cross section with a maximum width of 500 mm and a minimum width of 475 mm, and the hollow head of pile thickness is 70 mm. The inner area of the hollow head part was made as the square ribbed shape presented in the limit state design code in order to achieve horizontal shear strength between pile concrete and filling concrete. From the shear test results, it was found that the stable shear strength were secured without abrupt failure until maximum load stage despite the shear cracks was found. Shear strength is 135% and 119% higher than that of design value calculated from limit state design code. The driving test results of HPC pile according to the presence of additional reinforcement showed the outstanding crack resistance against impact loads condition. From the bending test results the flexural load between PHC pile and HPC pile was 1.51 times and 1.48 times higher than that of the design flexural load of conventional PHC pile.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.49-56
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• 2001

The possibility of a noise reduction of piezoelectric single Panels is experimentally studied. Piezoelectric single panel is basically a plate structure on which piezoelectric patch with shunt circuit is mounted. The use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. Piezo-damping is implemented by using a newly proposed tuning method. This method is based on electrical impedance model and maximizing the dissipated energy at the shunt circuit. By measuring the electrical impedance at the piezoelectric patch bonded on a structure, an equivalent electrical model is constructed near the system resonance frequency. Resonant shunt circuit for piezoelectric shunt damping is composed of register and inductor in series, and they are determined by maximizing the dissipated energy throughout the circuit. The transmitted noise reduction performance of single Panel is tested on an acoustic tunnel. The tunnel is a tube with a square cross section and a loud speaker is mounted at one side of the tube as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across Panels is measured. By enabling the piezoelectric shunt damping noise reduction is achieved at the resonance frequencies as well. Piezoelectric single panel with piezoelectric shunt damping is a promising technology for noise reduction in a broadband frequency.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.41-46
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• 2011

We investigated experimentally the properties of dust explosion through lycopodium particle clouds in a duct to provide the fundamental knowledge. Propagating dust flames in the vertical duct of 120 cm height and 12 cm square cross-section were observed by digital video camera and flame front is visualized using by PIV(Particle Image Velocimetry) system. As the result, when the same average dust concentration existed in the vertical duct, downward flame propagation was faster than the upward flame propagation, its rate increased with dust concentration in 300g/$m^3$. Post flames were caused by the ignition of unburned particles which flowed into the rear region of flame from passage between flame and duct wall, and they generated regardless of duct condition. Also, it was found that appearance frequency of post flames during dust flame propagations increased with the increase of dust concentration.

• Korean Journal of Remote Sensing
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• v.35 no.6_4
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• pp.1373-1389
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• 2019

KOMPSAT-5 is the first satellite in Korea equipped with X-band Synthetic Aperture Radar (SAR) instrument and has been operated since August 2013. KOMPSAT-5 is used to monitor the global environment according to its observation purpose and the availability of KOMPSAT-5 is also highlighted as the need of high resolution wind data for investigating the coastal region. However, the previous study for the validation of wind derived from KOMPSAT-5 showed that the accuracy is lower than that of other SAR satellites. Therefore, in this study, we developed the correction equation of normalized radar cross section (NRCS or backscattering coefficient) for improvement of wind from the KOMPSAT-5 and validated the effect of the equation using the in-situ measurement of ocean buoys. Theoretical estimated NRCS and observed NRCS from KOMPSAT-5 showed linear relationship with incidence angle. Before applying the correction equation, the accuracy of the estimated wind speed showed the relatively high root-mean-square errors (RMSE) of 2.89 m s^-1 and bias of -0.55 m s^-1. Such high errors were significantly reduced to the RMSE of 1.60 m s^-1 and bias of -0.38 m s^-1 after applying the correction equation. The improvement effect of the correction equation showed dependency relying on the range of incidence angle.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.5
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• pp.135-147
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• 2018

The objective of this study was to analyze the characteristics of combined 1D/2D inundation simulation of riverside farmland using the Hydrologic Engineering Center - River Analysis System (HEC-RAS). We compared and analyzed inundation simulation results between 1D and combined 1D/2D hydraulic simulation using HEC-RAS. Calibration and validation of stream stage were performed using three rainfall events. The coefficient of determination ($R^2$) and root mean square error (RMSE) between simulated and observed stream stage were 0.935 - 0.957 and 0.250 m - 0.283 m in calibration and validation, respectively. The inundation area showed no significant difference in 1D and combined 1D/2D simulation ($8.48km^2$ in 1D simulation, $8.75km^2$ in combined 1D/2D simulation). The average inundation depth by 1D simulation was 1.4 m deeper than combined 1D/2D simulation. In the lower inundation depth, the inundation area by combined 1D/2D simulation was larger than inundation area by 1D simulation. As the inundation depth increased, the inundation area by 1D simulation became wider. In the case of the 1D/2D combined simulation, low elevation areas along the river bank were inundated widely. Compared to 1D/2D combined simulation, the flood radius in some sections was longer in 1D simulation. In the 1D analysis, because the low altitude riverside farmlands are also assumed to stream, it is calculated that riverside farmlands have the same stage as the mainstream when the stream is overflowed. Therefore, the inundation area seems to be overestimated in those sections. In other regions, the inundation areas tend to be broken depending on overflow by each stream cross-section. In the case of river flooding, the overflow is expected to flow to the lower area depending on the terrain, such as the results of the combined 1D/2D simulation. It is concluded that the results of combined 1D/2D inundation simulation reflected the topographical characteristics of low-lying farmland.

• Clean Technology
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• v.25 no.2
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• pp.147-152
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• 2019

Electrostatic precipitator that shows a good performance for the removal of particulate matter is important for controlling emissions from industrial facilities and power plants. The efficiency of the electrostatic precipitator on the removal of particulate matter is highly affected by the flow pattern inside the electrostatic precipitator. A number of studies have been conducted to obtain uniform flow distribution inside electrostatic precipitators. An electrostatic precipitator (ESP) with a length of 3.5 m and a height of 0.875 m was designed and installed in this study. The ESP included an inlet duct, diffuser, body, and contractor. Three perforated plates were installed in the diffuser of the ESP. Five pitot tubes were installed vertically and used to measure flow distribution in the cross section of the ESP body. Root mean square deviation value (RMS%) was used to examine the flow distribution inside the ESP when the perforated plates were installed in the diffuser. Flow distribution was also investigated in relation to the porosity of the perforated plate. The results showed that the perforated plates improved greatly the flow distribution inside the electrostatic precipitator. In addition, the most uniform flow distribution was found with 40%, 50%, and 50% porous perforated plates located from the inlet of the diffuser.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.95-104
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• 2007

This study was focused on the effect of concrete strength and lateral ties of concrete columns subjected to eccentric compressive loads. The twenty-four concrete columns with $200mm{\times}200mm$ square cross-section were tested. The main variables were concrete strength, spacing and configuration of lateral ties, and eccentricity ratios. From the experiment, the followings were investigated ; 1) In all cases, it was observed that the increase of concrete compressive strength led to the decrease of ductility. Also, as the eccentricity ratios increased, the effect of ductility enhancement by lateral ties decreased. 2) As the ties spacing decreased from 100mm to 30mm, the magnitude of axial load acting on the concrete column showed an enhancement of 1.1~1.2 times and the descending curve after a peak moment presented a smooth decline. 3) The high-strength concrete columns required a design of lateral ties to increase the volumetric ratios and density of tie spacing to sustain a proper strength and ductility. Accordingly, regardless of concrete strength, the current AIK design code to specify the maximum tie spacing of concrete columns was proven to lead to the poor strength and ductility for seismic design. Therefore, it is necessary to develop a new seismic design code that connects volumetric ratios and tie spacing of concrete columns with concrete strength.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.29 no.3
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• pp.116-123
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• 2011

This study investigates the characteristics(form, material, structure, method of construction, vegetation) and model of lotus pond in Joseon Royal Tombs for conservation and restoration. The objects of study are the lotus pond of Namyangju Gwangreung, Hyoreung, Gimpo Jangreung and Sungreung that are well-preserved and the record is remaining. The form is two plane types, square shaped include an island and square shaped. The pond is 7.5~81m in width and 6.5~45m in length and the island is 8~16m in diameter. The depth of water is 0.5~1.2m and the cross section form is narrow bottom and wide top. The material of shore protection is soil in Hyoreung, Gimpo Jangreung and Sungreung. The bottom is mud in all sites. I think that the main material of the lotus pond in Joseon Royal Tombs is soil. The lotus pond is built by soil bank in the structure and method of construction. The water supply and drainage are worked through the culvert. There are many kinds of plants in the lotus pond today, however I think that the model of vegetation of lotus pond in Joseon Royal Tombs is lotus the inside, pine tree, fir tree and flowers the around and pine tree the inside of island in compared the present and the old literature. In comparison with the lotus pond in Joseon Royal Tombs and the lotus pond in the Joseon palace, the material is the biggest difference. The main material is soil in Royal Tombs but isodomic in Royal Palace. I think that the difference of material in between two causes the difference of structure and method of construction. The Royal Tombs is valuable in architecture, landscape and esthetics, this study investigated the characteristics and model of lotus pond in Joseon Royal Tombs. I think that this study serves as a momentum to find a traditional technique in Royal water space and offer the foundation to plan in the contemporary water space.