• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.860-865
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• 2006

The characteristics of flow field and turbulent mixing efficiency of SS in non-aerated contacting reactor are critical design parameters directly affecting on the efficiency of the overall process of wastewater treatment system. To this end, in this study numerical fluid dynamic calculation has been made to investigate the flow field and concentration distribution of SS in terms of specification(shape and dimension) of impeller and other operating conditions. As the first step, the performance of the computer program developed was successfully evaluated by the comparison of the typical flow field with the type of impeller with that appeared in open literature. Further, a series of parametric investigations are made in terms of interesting parameters such as the type and dimension of impeller, location, and number of impeller, etc. A number of useful conclusions obtained by numerical calculation are the superiority of mixing efficiency of pitched type than the flat one together with the visible increase of the overall mixing effect by the employment of the larger impeller and increase of the impeller number, etc.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.146-152
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• 2013

In this paper, we have proposed and experimentally demonstrated an intensity-based self-referencing fiber optic sensor. The proposed fiber optic sensor consists of a broadband light source (BLS), fiber Bragg grating (FBG), tunable Fabry-Perot (F-P) filter, and LabVIEW program. We define the measurement parameter (X) and the calibration parameter (${\beta}$) to determine the transfer function(H) of the self-referencing fiber optic sensor, and the validity of the theoretical analysis is confirmed by experiments. The self-referencing characteristic for the proposed system has been validated by showing that the measurement parameter (X) is invariant for BLS optical power attenuations of 0 dB, 3 dB, and 6 dB. Also, the measured result is irrelevant to the FBGs with different characteristics. This means that the proposed fiber optic sensor offers the flexibility for determining the FBGs needed for implementation. Experimental results for the proposed fiber optic sensor are in good agreement with a theoretical analysis for BLS optical power attenuations and for three FBG pairs with different characteristics. So, the proposed fiber optic sensor has several benefits, including the self-referencing characteristic and the flexibility to determine the FBGs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.67-75
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• 2019

The diaphragm used for CFT columns has a small amount of steel to be used, but has a disadvantage that welding is difficult and openings are required because the steel tube and four sides must be welded. The improved diaphragm to be examined in this study was cut into four corners by cutting the center hole for concrete filling. In the improved diaphragm, the width of the center hole is the same as that of the previous diaphragm, but the width of the diaphragm contacting the steel tube is reduced, thereby reducing the welding length by about 70% compared to the previous diaphragm. The in-plane strain of each specimen was analyzed when the same load was applied to the interior diaphragm through a simple tensile test. Using the general FEM program(ANSYS 19.2), the analysis was performed under the same conditions as the actual simple tensile test, and the load transfer between the improved diaphragm and the previous diaphragm was compared. When the width of the diaphragm is equal to or smaller than the flange width, stress is concentrated from the end of the diaphragm, and when the flange width is larger, stress is concentrated at the center.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.825-836
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• 2022

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.1-8
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• 2005

The quantity of light available for a space can be translated in term of the amount of energy savings through a process of a building energy simulation. To get significant energy savings in general illumination, the electric lighting system must be incorporated with a daylight - activated dimmer control. A prototype configuration of an once interior has been established and the integration between the building envelope and lighting and HVAC systems is evaluated based on computer modeling of a lighting control facility. First of all, an energy-efficient luminaire system is designed and the lighting analysis program, Lumen-Micro 2000 predicts the optimal layout of a conventional fluorescent lighting future to meet the designed lighting level and calculates unit power density, which translates the demanded met of electric lighting energy. A dimming control system integrated with the contribution of daylighting has been applied to the operating of the artificial lighting. Annual cooling load due to lighting and the projecting saving amount of cooling load due to daylighting under overcast diffuse sky m evaluated by computer software ENER-Win. In brief, the results from building energy simulation with measured daylight illumination levels and the performance of lighting control system indicate that daylighting can save over 70 percent of the required energy for general illumination in the perimeter zones through the year A 25[%] of electric energy for cooling and almost all off heating energy may be saved by dimming and turning off the luminaires in the perimeter zones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1576-1581
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• 2013

In the present study, the performance of a PF heat exchanger for heat pump dryer was investigated. Capacity and dehumidification amount of the PF heat exchangers(PF1, PF2, PF3) by different inclination angles($0^{\circ}$, $30^{\circ}$, $60^{\circ}$) were studied. Experimental conditions were an air velocity crossing to the heat exchanger(0.5m/s), an air dry-bulb temperature($60^{\circ}C$) and relative humidity(70%). The experimental results have shown that the performance of the inclined PF heat exchangers was better than that of the vertically installed one. PF3 showed better performance compared to PF1 and PF2 due to the large pin pitch which are leading to more draining for dehumidified water. But, capacity and dehumidification amount of the PF heat exchanger at the inclination angles of $60^{\circ}$ was decreased due to pressure drop. Also, to predict the experimental data of the PF heat exchanger, the performance program was developed for the inclination angles of $0^{\circ}$. PF heat exchanger performance between experiment data and calculation data was satisfied within the maximum 2% for capacity and 3% for dehumidification amount.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.32-39
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• 2021

Recently, necessities of steel form for reinforced concrete beam and girder have been emphasized in building structures for the reduction of the construction period and the labor cost. SY Beam was developed for the these purposes and is roll-formed using thin steel plate. On this research, we tried to evaluate and verify the performance and behavior of SY Beam under construction loading stage as like pouring in situ concrete. For the standard shape of SY beam, structural modelling with various steel thicknesses has carried out using MIDAS GEN program. From results of modelling, the width and height of SY Beam were determined 600mm and 400mm respectively. For 3 SY Beams, the loading experiment was performed to measure vertical and horizontal displacement under stacking sand, concrete block, and bundle of rebar. As a result, the vertical deflection showed a tendency to decrease as the thickness increased. In the horizontal displacement, the trend according to the thickness was not clearly observed. From the evaluation on the loading experiment, it is considered that the SY Beam can secure both workability and structural safety. In particular, the SY Beam(1.2mm) hardly generates horizontal displacement, so it has excellent load-bearing capacity. So, we judged that the SY Beam with 1.2mm steel plate has excellent performance and consider to be immediately commercially available.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.5
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• pp.364-370
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• 2019

In this paper, an individual blade control (IBC) methodology is applied to find the best input scenario for vibratory hub loads reduction of XH-59A co-axial rotorcraft in high speed flight. A comprehensive aeromechanics analysis code CAMRAD II is employed to analyze the aircraft. A parametric study is conducted for optimum IBC inputs leading to the maximum vibration reduction. Numerical results demonstrate that up to 50% reduction in the hub vibration index is obtained for an IBC input at 3/rev frequency with the amplitude and phase angle of 0.5 deg. and 300 deg., respectively. The upper rotor exhibits as much as 6% more vibration reduction as compared to that of the lower rotor due to a clean inflow characteristic of the rotor. It is found that further vibration reduction gain is reached for IBC inputs with advancing-side only control. The hub vibration becomes reduced by up to 17% in reference to that with full rotor disk control. It is noted that the additional gain is obtained with significantly less power input with the advancing-side only control.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.605-615
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• 2021

Recently, to shorten construction periods and reduce labor costs, the need for a corrugated beam form in the RC structure is being emphasized. The purpose of this study is to evaluate the deformation performance of SY Beam, a newly developed corrugated beam form work, during concrete casting. The standard cross-sectional shape of SY Beam was determined by modeling the deck structure of various thicknesses using the MIDAS GEN program. As a result, the cross-sectional dimensions of the SY Beam were determined to be 400mm and 450mm in width and height, respectively. A total of three SY Beam specimens were fabricated using steel plate thicknesses of 0.8, 1.0, and 1.2mm. The load conditions applied during casting concrete at the actual site are reflected. The vertical and horizontal displacements of the SY beam were measured during concrete casting. As a result, the vertical displacement showed a tendency to decrease as the thickness increased. Considering both vertical and horizontal displacement, the case with steel plate thickness of 1.2mm is the safest and most immediately applicable to the field. In the future, to secure manufacturability, constructability, and economics, the optimum steel plate thickness should be derived, and additional analysis and experimental studies for 1.05, 1.1, and 1.15mm are required.

• Membrane Journal
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• v.33 no.6
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• pp.447-453
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• 2023

The performance of computer systems and the development of various computer simulation programs have made it possible to analyze chemical systems composed of more complex elements, and accordingly, research using molecular dynamics simulation is being actively conducted. Research on calculating the gas permeation characteristics of polymer membranes by molecular dynamics, which was previously conducted mainly through experiments, is receiving attention for gas barrier membranes used in food packaging and pharmaceuticals. Recently, there has been a report that a gas barrier effect appears when a coating film is made using silk fibroin, and in this study, a study was conducted using molecular dynamics simulation to confirm whether an oxygen barrier effect appears when a composite film is made using silk fibroin. We built a single model, calculated the gas permeation characteristics, and compared it with the experimental value to confirm that the model reflects the actual experimental results. Actual composite membrane models were then built and the gas movement path within the polymer was analyzed. As a result, oxygen molecules were found that they could not pass through and was blocked in the fibroin region. Therefore, the composite membrane with silk fibroin has excellent oxygen barrier property and is expected to be useful in food packaging, etc.