• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.49-57
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• 2023

The autogenous pressurization has been widely adopted for propulsion systems of next-generation reusable rockets due to its low cost and high reliability. The autogenous pressurization has a simple structure, but an understanding of the heat and mass transfer occurring inside the tank is essential. For this reason, a simulation test of the autogenous pressurization was conceived. The experiment equipment was constructed based on overseas pressurization test facilities cases and expert advice. Unlike the actual autogenous pressurization system, the propellant tank was insulated to exclude external influences. The pressurized gas supply line and the propellant pipe were separated. Using the manufactured autogenous pressure experiment equipment, it is possible to evaluate the condensation phenomenon of pressurants in cryogenic propellants, comparison of the efficiency of pressurization using helium and evaporated gas and the pressurization capacity according to the temperature of pressurant.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.229-237
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• 2009

A conventional way of backfilling has used sand or in-situ soil. It not only requires substantial amount of time and cost but also makes it particularly difficult to fill the bottom part and small cracks of a pipe. To address the problem with the conventional method of compaction, liquefied stabilized soil was proposed as an alternative because it reuses in-situ soil which can ensure sand supply while adjusting flowability and strength of the soil with design of mix proportion. With an aim to identify the mixing properties of liquefied stabilized soil depending on the organic content of in-situ soil, this study conducted indoor tests of material segregation, flowability, strength, and permeability by changing humic acid content of the soil. The results revealed that material segregation and flowability increased proportionally while strength decreased with the increased amount of humic acid. In the mean time, permeability of liquefied stabilized soil wasn't affected by organic content.

• Journal of Korea Water Resources Association
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• v.56 no.7
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• pp.451-460
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• 2023

In this study, the risk of red water and turbid water occurrence was analyzed by classifying it into detachment risk and deposition risk. First, risk factors for red water and turbid water were determined, and hydraulic analysis was conducted considering seasonal water consumption. The applied area was Cheongju City, and the risk analysis was conducted across 13 areas, and the areas with high deposition risk and high detachment risk were selected. The high risk of both detachment and deposition can be judged as an area with a very high probability of causing water quality problems. The areas with the highest deposition risk and detachment risk are the old towns of Nae deok1-dong and Yul1yang-dong, which are the oldest areas in Cheongju City with an age of more than 30 service years of pipe installation. By analyzing the risk of deposition and detachment, it will be possible to strengthen the maintenance function of the water supply network to provide the safe water to citizens and increase their confidence for tap water.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.285-292
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• 2023

As various accidents have occurred in underground spaces, we aim to improve the quality validation standards and methods as specified in the Regulations on Producing Integrated Map of Underground Spaces devised by the Ministry of Land, Infrastructure and Transport of the Republic of Korea for a high-quality integrated map of underground spaces. Specifically, we propose measures to improve the quality assurance of pipeline-type underground facilities, the so-called life lines given their importance for citizens' daily activities and their highest risk of accident among the 16 types of underground facilities. After implementing quality validation software based on the developed quality validation standards, the adequacy of the validation standards was demonstrated by testing using data from two-dimensional water supply facilities in some areas of Busan, Korea. This paper has great significance in that it has laid the foundation for reducing the time and manpower required for data quality inspection and improving data quality reliability by improving current quality validation standards and developing technologies that can automatically extract errors through software.

• Advances in concrete construction
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• v.16 no.1
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• pp.69-78
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• 2023

This investigation delves into the adverse repercussions stemming from the impact of arsenic on steel pipes concealed within soil designated for rice cultivation. Simultaneously, the study aims to ascertain effective techniques for detecting arsenic in the soil and to provide strategies for mitigating the corrosion of steel pipes. The realm of nanotechnology presents promising avenues for addressing the intricate intersection of renewable energy, oil, and environmental pollution from a novel perspective. Nanostructured materials, characterized by distinct chemical and physical attributes, unveil novel pathways for pioneering materials that exert a substantial impact across diverse realms of food production, storage, packaging, and quality control. Within the scope of the food industry, the scope of nanotechnology encompasses processes, storage methodologies, packaging paradigms, and safeguards to ensure the safety of consumables. Of particular note, silver nanoparticles, in addition to their commendable antibacterial efficacy, boast anti-fungal and anti-inflammatory prowess, environmental compatibility, minimal irritability and allergenicity, resilience to microbial antagonism, thermal stability, and robustness. Confronting the pressing issue of arsenic contamination within both environmental settings and the food supply is of paramount importance to preserve public health and ecological equilibrium. In response, this study introduces detection kits predicated upon silver nanoparticles, providing an expeditious and economically feasible avenue for identifying arsenic concentrations ranging from 0.5 to 3 ppm within rice. Subsequent quantification employs Hydride Atomic Absorption Spectroscopy (HG-AAS), which features a detection threshold of 0.05 ㎍/l. A salient advantage inherent in the HG-AAS methodology lies in its capacity to segregate analytes from the sample matrix, thereby significantly reducing instances of spectral interference. Importantly, the presence of arsenic in the soil beneath rice cultivation establishes a causative link to steel pipe corrosion, with potential consequences extending to food contamination-an intricate facet embedded within the broader tapestry of renewable energy, oil, and environmental pollution.

• Journal of Hydrogen and New Energy
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• v.35 no.1
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• pp.34-39
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• 2024

Korea government is trying to supply liquid hydrogen from another country to domestic The research for liquid hydrogen transportation and liquefaction plant of hydrogen underway for several years, and empirical research is also planned in the future. Along with the development of liquid hydrogen transport ship/liquefaction plant technology, the development of liquid hydrogen reception base technology must be carried out. In this study, a concept level liquid hydrogen receiving terminal is constructed based on the process of the LNG receiving terminal. Based on this, a study is conducted on the development of analysis technology for the amount of BOG (pipe, tank) generated during cooldown and unloading in the liquid hydrogen unloading line (loading arm to storage tank). The research results are intended to be used as basic data for the design and liquid hydrogen receiving terminal in the future.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.17-23
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• 2024

Losses in domestic water supply due to leaks are very large, such as fractures and defects in pipelines. Therefore, preventive measures to prevent water leakage are necessary. We propose the development of a leakage detection sensor utilizing vibration sensors and present an optimal leakage detection algorithm leveraging artificial intelligence. Vibrational sound data acquired from water pipelines undergo a preprocessing stage using FFT (Fast Fourier Transform), followed by leakage classification using an optimized tree-based boosting algorithm. Applying this method to approximately 260,000 experimental data points from various real-world scenarios resulted in a 97% accuracy, a 4% improvement over existing SVM(Support Vector Machine) methods. The processing speed also increased approximately 80 times, confirming its suitability for edge device applications.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.59-67
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• 1995

This study was conducted to develope the automatic insulation system which control inside temperature of the greenhouse. For this purpose, the double- wall greenhouse and system which could automatically supply and discharge styrene pellets were constructed and abrasion of the pellets, blower ability, insulating property, transmittance and shading effect were analyzed by the experiments. The results obtained from this study can be summarized as follows : 1. It took an hour and fifteen minutes to supply and discharge about 2㎥ pellets in the experimental greenhouse. However, it is possible to reduce the operation time by proper selection of the blower and exhaust port, and by proper control of the supply and return pipe. 2. It was founded that the indirect delivery way was more profitable than the direct one in the supply and return of pellets. 3. When the transmittance was measured between 10 a.m. and 3 p.m., the average light transmissivity rate was 67%. 4. In winter nighttime, the inside temperature of the double- wall greenhouse with out the pellets was higher than the outside temperature by 3.4$^{\circ}C$ on an average. However, the inside temperature of the double - wall greenhouse with insulated area 73% was higher than the outside by one 6.6$^{\circ}C$ on an average, and the inside temperature of the greenhouse with insulated area 100% was higher than outside one by 13.5$^{\circ}C$ on an average. Therefore, it was proved that the insulating ability of the double - wall greenhouse in nighttime was excellent. 5. When the outside temperature was 36.9$^{\circ}C$ on an average, the inside temperature of the double- wail greenhouse with insulated area 100% was 3$0^{\circ}C$ on an average. As the inside temperature was lower than the outside one by 7$^{\circ}C$ on an average, we could know that the shading effects of the double- wall greenhouse were excellent in summer daytime.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.371-377
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• 2013

The government has been carrying out a project for supporting the rain shelter for hot pepper as part of measures stabilizing the demand and supply of hot pepper since 2012. However, the eaves height of single-span plastic greenhouses extensively used in farms is low, which are inappropriate for the rainproof cultivation of hot pepper. This study attempted to develop single-span plastic greenhouses which are structurally safe and have the dimensions suitable for the rainproof cultivation of hot pepper as well. The structure status of plastic greenhouses and restructuring wishes of 56 rainproof cultivation farms nationwide were investigated to set up the width and height of the plastic greenhouses. 53% of the plastic greenhouses currently in operation had a width of under 7 m and 64% of their eaves had a height of 1.5 m or less, which accounted for the highest rate. Mostly the width of 7.0 m was desired for the greenhouses and the height of 2.0 m for their eaves, so these values were chosen as the dimensions for the singlespan plastic greenhouses. After an analysis of their structural safety while changing the specifications of the rafter pipe in various ways, 5 kinds of models were suggested considering the frame ratio and installation costs. The 12-Pepper-1 model is a developed single-span plastic greenhouse for hot pepper in which a ${\emptyset}42.2{\times}2.1t$ rafter pipe is installed at an interval of 90cm and the models of 12-Pepper-2 through 5 are the other developed ones in which a ${\emptyset}31.8{\times}1.5t$ rafter pipe is installed at intervals of 60 cm, 70 cm, 80 cm and 90 cm, respectively. As a result of an analysis of economic feasibility of 12-Pepper-2 compared to 10-Single-3 in the notification of the Ministry for Food, Agriculture, Forestry and Fisheries, it turned out that there would be an increase in profits by about 1.2 million won based on one building of a greenhouse sized 672 $m^2$.

• Korean Journal of Agricultural Science
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• v.7 no.2
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• pp.103-108
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• 1980

In order to elucidate the source of bacterial contamination during processing U. H. T. milk and to ensure its hygienic control, bacterial numbers were determined each step of the processes on the milks, water, tanks and pipe lines, and environments. The results obtained were as follows. 1. The viable numbers of mesophilic bacteria were $1.2{\sim}1.9{\times}10^7/ml$ of milk in the storage tank and in pipe line connected to the preheater. These were decreased to $7.0{\times}10cells{\sim}3.4{\times}10^2cells/ml$ after preheating and homogenization, and to $1.0{\times}10cells/ml$ after sterilization, then increased up to $1.2{\times}10^2cells/ml$ after packing. 2. The numbers of thermophilic bacteria were $5.0{\times}10cells{\sim}1.0{\times}10^2cells/ml$ of milk before preheating ; $3.0{\sim}5.0{\times}10cells/ml$ after homogenization ; none in the sterilizer and surge tank ; and $1.0{\sim}8.0{\times}10cells/ml$ after packing. 3. The levels of psychrophilic bacteria were $1.0{\sim}3.7{\times}10^6cells/ml$ of milk before preheating ; $1.0{\sim}4.0{\times}10cells/ml$ after homogenization ; $1.0{\times}10cells/ml$ after sterilization ; and $2.0{\times}10cells{\sim}2.5{\times}10^2cells/ml$ after packing. 4. No coliform bacteria were detected after sterilization, while the level before preheating was $2.1{\times}10^4cells{\sim}6.5{\times}10^5cells/ml$ of milk. 5. The level of mesophiles was $3.0{\times}10cells{\sim}7.4{\times}10^2cells$ in the environmental air, water supply, and unfilled packs and bottles ; that of thermophiles $1.0{\sim}3.0{\times}10cells$ in the air and water ; that of psychrophiles $1.0{\times}10cells{\sim}1.0{\times}10^2cells$ in the air, water, packs and bottles ; however no coliform was detected.