• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.1
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• pp.14-19
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• 2023

In summer, the natural ventilation performance for varying greenhouse width is very important in the glasshouses for year round cultivation. The effect of the side openings and greenhouse width on natural ventilation performance was analyzed by simulation. The necessary ventilation rate with different solar radiation transmittance increased significantly when the outside temperature grows higher. The necessary ventilation rate of 40% transmittance was about half of that of 90% transmittance. In consequence, shading effect on temperature control in greenhouse is significant in summer. When the total area of the openings for ventilation is constant, the maximum ventilation rate happens when the area of roof openings is equal to the area of side openings. This maximum ventilation rate is about 3 times of that of the greenhouse with roof openings and without side openings. Therefore, the side openings are advantageous to improve the natural ventilation in greenhouses. As the greenhouse width increases, the influence of side openings on the ventilation rate is becoming smaller. If the natural ventilation rate of the greenhouse with roof and side openings is to become double of that of the roof openings only, the width should be narrower than 38.4m for the Venlo type and 64m for Wide span type.

• Korean Journal of Remote Sensing
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• v.37 no.6_3
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• pp.1985-1999
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• 2021

The purpose of this study is to apply urban heat island reduction techniques(green roof, cool roof, and cool pavements using heat insulation paint or blocks) recommended by the Environmental Protection Agency (EPA) to our study area and determine their actual effects through a comparative analysis between land cover objects. To this end, the area of Mugye-ri, Jangyu-myeon, Gimhae, Gyeongsangnam-do was selected as a study area, and measurements were taken using a drone DJI Matrice 300 RTK, which was equipped with a thermal infrared sensor FLIR Vue Pro R and a visible spectrum sensor H20T 1/2.3" CMOS, 12 MP. A total of nine heat maps, land cover objects (711) as a control group, and heat island reduction technique-applied land covering objects (180) were extracted every 1 hour and 30 minutes from 7:15 am to 7:15 pm on July 27. After calculating the effect values for each of the 180 objects extracted, the effects of each technique were integrated. Through the analysis based on daytime hours, the effect of reducing heat islands was found to be 4.71℃ for cool roof; 3.40℃ for green roof; and 0.43℃ and -0.85℃ for cool pavements using heat insulation paint and blocks, respectively. Comparing the effect by time period, it was found that the heat island reduction effect of the techniques was highest at 13:00, which is near the culmination hour, on the imaging date. Between 13:00 and 14:30, the efficiency of temperature reduction changed, with -8.19℃ for cool roof, -5.56℃ for green roof, and -1.78℃ and -1.57℃ for cool pavements using heat insulation paint and blocks, respectively. This study was a case study that verified the effects of urban heat island reduction techniques through the use of high-resolution images taken with drones. In the future, it is considered that it will be possible to present case studies that directly utilize micro-satellites with high-precision spatial resolution.

• Geomechanics and Engineering
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• v.11 no.3
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• pp.401-420
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• 2016

The stability of deep coal roadways with large sections and thick top coal is a typical challenge in many coal mines in China. The innovative Universal Discrete Element Code (UDEC) trigon block is adopted to create a numerical model based on a case study at the Dongtan coal mine in China to better understand the failure mechanism and stability control mechanism of this kind of roadway. The failure process of an unsupported roadway is simulated, and the results suggest that the deformation of the roof is more serious than that of the sides and floor, especially in the center of the roof. The radial stress that is released is more intense than the tangential stress, while a large zone of relaxation appears around the roadway. The failure process begins from partial failure at roadway corners, and then propagates deeper into the roof and sides, finally resulting in large deformation in the roadway. A combined support system is proposed to support roadways based on an analysis of the simulation results. The numerical simulation and field monitoring suggest that the availability of this support method is feasible both in theory and practice, which can provide helpful references for research on the failure mechanisms and scientific support designing of engineering in deep coal mines.

• Geomechanics and Engineering
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• v.20 no.6
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• pp.485-495
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• 2020

Based on the movement characteristics of overlying strata with gangue backfilling, the compression test of gangue is designed. The deformation characterristics of gangue is obtained based on the different Talbot index. The deformation has a logarithmic growth trend, including sharp deformation stage, linear deformation stage, rheological stage, and the resistance to deformation changes in different stages. The more advantageous Talbot gradation index is obtained to control the surface subsidence. On the basis of similarity simulation test with gangue backfilling, the characteristics of roof failure and the evolution of the supporting force are analyzed. In the early stage of gangue backfilling, beam structure damage directly occurs at the roof, and the layer is separated from the overlying rock. As the working face advances, the crack arch of the basic roof is generated, and the separation layer is closed. Due to the supporting effect of filling gangue, the stress concentration in gangue backfilling stope is relatively mild. Based on the equivalent mining height model of gangue backfilling stope, the relationship between full ratio and mining height is obtained. It is necessary to ensure that the gradation of filling gangue meets the Talbot distribution of n=0.5, and the full ratio meets the protection grade requirements of surface buildings.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.120-128
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• 2015

In this paper, Residential roof top photovoltaic system with 9.9 kW design is proposed. The system composed of 200 Watts solar array 33 panels connecting in series 10 strings and parallels 3 strings which have maximum voltage and current are 350 V and 23.8 A. The 10 kW sinusoidal grid-connected inverter with window voltage about 270-350 is selected to convert and transfer DC Power to AC Power at PCC (Point of Common Coupling) of power system following to utility standard. However the impact of fluctuation and uncertainty of weather condition of PV may decrease the voltage stability and voltage collapse of power system. In order to solve this problem the energy storage such 120 V 1200 Ah battery bank and 30 kVAR capacitor are designed for voltage stability control. The other expensed for installing the system such battery charger, cable, accessories and maintenance cost are concerned. The economic analysis by using investment from money loan with interest about 7% and use own money which loss income of deposit about 3% are calculated as 671,844 and 547,044 for PV system with energy storage and non energy storage respectively. The solar energy from PV is about 101,616 Bath per year which evaluated by using the value of $5kWh/m^2/day$ from average peak sun hour (PSH) of the Thailand and 6.96 Bath/kWh of Feed in Tariff Incentive. The payback periods of four scenarios are proposed follow as i) PV system with energy storage and use loan money is 15 years ii) PV system with no energy storage and use loan money is 10 years iii) PV system with energy storage and use deposit money is 9 years iv) PV system with energy storage and use deposit money is 7 years. In addition, the other scenarios of economic analysis such no FIT support and other type of economic analysis such NPV and IRR are proposed in this paper.

• KIEAE Journal
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• v.16 no.1
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• pp.57-65
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• 2016

Purpose: The purpose of this study is to analyze the energy performance by applying new technologies for passive and active control. Method: We selected new technologies for passive and active control which are based on formal study by analyzing technology applied to the High-Performance Buildings in various countries. Also, we analyzed energy saving potential for each technologies by breakdown the result of the energy saving rates in detail. Result: For the wall and roof insulating methods, preceding studies showed that up to 21% energy could be saved by improving roof insulation and applying proper outside insulation compared to non-insulation. For the windows and glazing system, preceding studies showed that Low-E glazing system could save up to 11% energy compared to single glazing system. Studies about solar and daylighting controls revealed that effective daylighting dimming control could save 13% of energy compared to uncontrolled situation. Studies on DOAS (Dedicated Outdoor Air System) showed that about 23% energy could be saved compared to standard VAV system. Studies on the active chilled beam showed that about 25% energy could be saved compared to standard VAV system and studies of applying UFAD (Under Floor Air Distribution) could consume 31% less energy than applying overhead system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.11
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• pp.952-960
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• 2018

Recently, lots of remote sensing satellite require agility to collect more images within the limited time frame. To satisfy this kind of mission requirement, high torque actuator such as CMG is an essential element. In this study, 5Nm class small CMG developed by KARI is introduced to implement for an agile small satellite design. One of the singularity escape CMG steering law, Designated Direction Escape (DDE) method, which is a sort of modified version of Singular Direction Avoidance (SDA) method is summarized for its application on the numerical simulation of agile attitude control system design result. The performance of DDE method is demonstrated properly by escaping well known elliptic internal singularity successfully. 5Nm class small CMG cluster in a pyramid type as well as a roof type configuration is utilized to perform the numerical simulation and to demonstrate its agility design result for a small satellite. Simulation result shows the properness of 5Nm small CMG to a small agile satellite system. Also, the simulation result provides some valuable information that is important to CMG hardware design and manufacturing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.241-250
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• 2022

This paper addresses the Feasible Angular Momentum(FAM) chart that can be used as an indicator for maneuverability analysis of spacecraft installed with control moment gyros(CMGs). Recently, as the demands for high agility of spacecraft has been increasing in order to perform the space mission given to spacecraft more effectively, interest in CMGs, which is a high torque generator is increasing. However, since the CMG has a singularity problem that does not generate the control torque in the specific directions, in this paper, we consider the two pairs of parallel control moment gyros(TPCMGs) that follows the roof-type configuration. The Gimbal space was newly defined except for the space where singularity can be generated and the space where torque error is generated due to the hardware limits. The feasible angular momentum space is defined as a FAM chart, and it is very meaningful that it is possible to analyze the spacecraft's rotational maneuverability effectively by deriving the spacecraft's 3-axis parameters in the corresponding gimbal space mathematically.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.495-499
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• 2008

This study developed a determination method for a rainwater retention-pumping combination system for roof runoff control. The outflow and stored water volume in the rainwater system was simulated using a water balance equation. Its result is presented in the TPP (Tank capcity-Peak outflow-Pumping rate) curves for rainfall return periods. In a case study on reduction of the peak flow rate of 100-year return period to 5-year in Seoul, The range of pumping rate for $100m^2$ roof area is determined as $0{\sim}25{\ell}$/min. Additionally, retention volume of $8.5{\sim}10m^3$ can be combined with the pumping rate range. That is to say an effective combination of a retention-pumping system capacity can be determined from a system of $8.5m^3$ tank with $25{\ell}$/min to $10m^3$ tank without pump. Using the TPP curves, engineers can determine the effective combination range of retention & pumping system capacity. Furthermore, that can be helpful to decide a detail system capacity for field condition.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.1
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• pp.15-20
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• 2016

Recently, the u-IT applications for plants and livestock become larger and control of livestock farm environment has been used important in the field of industry. We implemented wireless sensor networks and farm environment automatic control system for applying to the breeding barn environment by calculating the THI index. First, we gathered environmental information like livestock object temperature, heart rate and momentum. And we also collected the farm environment data including temperature, humidity and illuminance for calculating the THI index. Then we provide accurate control action roof open and electric fan in of intelligent farm to keep the best state automatically by using collected data. We believed this technology can improve industrial competitiveness through the u-IT based smart integrated management system introduction for industry aversion and dairy industries labor shortages due to hard work and old ageing.