• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.258-263
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• 2012

In this paper the Chemical Propulsion Subsystem of COMS is briefly explained and some telemetries acquired by a series operations of CPS during the Launch and Early Operation Phase of COMS are presented. The pressure and temperature of pressurant tank telemetries are compared with the results of the developed computer program. The changes in pressure are due to the two major phases. The first one is the initialization phases of CPS composed of the venting phase to vent the helium gas in the pipe network from the downstream of the propellant tanks to the thrusters for safety, the priming phase to fill the vented pipe network with oxidizer and fuel respectively and then the pressurization phase to pressurize the ullage of propellant tank to regulated pressure. And the other is the apogee engine firings in which COMS CPS is in the orbit raising phase to use helium as a pressurant to keep the pressure of propellant tank as the liquid apogee engine get fired until COMS reached to the target orbit. This program can be applicable to prepare basis design data of the next Geostationary Satellite CPS.

• KSBB Journal
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• v.23 no.6
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• pp.470-473
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• 2008

A pilot-plant biofilter ($1750\;m\;W{\times}2750\;mm\;L{\times}2000\;mm\;H$) packed with polyurethane foam ($20\;m\;W{\times}20\;mm\;L{\times}20\;mm\;H$) was installed in an pharmaceutical plant emitting gas streams containing n-hexane and alcohols. The biofilter was successfully operated for 74 days under highly fluctuating incoming concentrations at a residence time of 12.8-24.8 sec. Alcohols and n-hexane were removed by more than 90% from 5 and 20 days after start up, respectively. Malodor was also removed more than 95% from 20 days after start up.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1275-1284
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• 2022

This study provides an investigating the electrolyte reaction characteristics during thermal runaway of a lithium-ion battery(LIB). Dimethyl carbonate(DMC) is known as the main substance that makes up the electrolyte. The mono-molecular decomposition characteristics of DMC were derived through numerical analysis. Cobalt oxide can release oxygen under high temperature conditions. Also, DMC is converted to CH₄, H₂, CO, and CO₂. Especially, it was found that the decomposition of the DMC begins at a temperature range of 340-350℃, which dramatically increases the internal pressure of the LIB. In the by-products gases, the molar ratio of CO and CO₂ changed according to the molecular structure of DMC and temperature conditions. The correlation of the [CO]/[CO₂] ratio according to the temperature during thermal runaway was derived, and the characteristics of the reaction temperature could be estimated using the molar ratio as an indicator. In addition, the oxidation and decomposition characteristics of DMC according to the residence time for each temperature were estimated. When DMC is exposed to low temperature for a long time, both oxidation and decomposition may occur. There is possibility of not only increasing the internal pressure of the LIB, but also promoting thermal runaway. In this study, internal environment of LIB was identified and the reaction characteristics between the active materials of the cathode and electrolyte were investigated.

• Fire Science and Engineering
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• v.33 no.4
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• pp.59-69
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• 2019

The present article relates to an experimental study on fire risks due to overcharge and external heat of ESS lithium battery. According to the experimental results of overcharge, ignition occurred as combustible gas and smoke was slowly increased after occurrence of venting, and an explosive combustion form accompanied by flame eruption and sparks was displayed as charged energy is rapidly discharged in an instant. On the other hand, according to the experimental results of external heat, as a tremendous amount of combustible gas and smoke was ignited following being discharged after occurrence of vent, the charged energy itself was rapidly reduced due to the discharged energy so that a passive combustion form was observed when compared with overcharge after occurrence of flames. According the analysis results of fire damage characteristics, differences between external heat (External flame) could be found through visual and X-ray inspections. Namely, while inside electrode plate was completely destroyed and perforation of the electrode plate was observed in the case of overcharge, fire damage of the electrode plate was not severe maintaining the form in the case of external heat.

• Journal of the Korean Society of Radiology
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• v.8 no.4
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• pp.211-216
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• 2014

Radium is rock or soil of crust or uranium of building materials after radioactivity collapse process are created colorless and odorless inert gas that accrue well in sealed space like basement. It inflow to lung circulate respiratory organ and caused lung cancer because of deposition of lung or bronchial tubes. In this study, the air in the elementary school classroom nongdoeul tonkatsu place of measured values were compared using the calculated annual internal radiation exposure. La tonkatsu exposure measured in primary school classroom at least five schools when you close the windows in the average floor 0.56mSv 2 floors ground floor windows when opened 0.384mSv 048mSv 3 floors, 2 floor levels of the same three layers 0.31mSv 0.296mSv the human exposure to radon and radiation on the first floor of 3 floors above ground in a lot of exposure was moderate. When you close the window from the first floor up 0.384mSv 056mSv 3 floors with a minimum annual radiation exposure due to natural radiation in the 16 to 23.3 percent minimum 2.4mSv accounted for. When I opened the window to the maximum annual radiation exposure 2.4mSv 0.296mSv 0.31mSv least a minimum of 12.3 to 12.91% accounted for Results suggest that more than five chodeunghakgyoeun La tonkatsu domestic radon measurements conducted below regulatory requirements and internal exposure has also fall within the normal range. People The less the radiation exposure to the human body because it reduces the impact in the classroom in elementary school vent windows often reduced to the maximum radon concentration in the air, if called tonkatsu be able to reduce radiation exposure for the immune system is weak and elementary will be helpful to experiment more in the future for the school authorities called tonkatsu investigation is done to him if the action to establish a more secure school building facilities is thought would be helpful.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.145-156
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• 2012

Seafloor hydrothermal system occurs along the volcanic mid-ocean ridge, back-arc spreading center, and other submarine volcanic regions. The hydrothermal system is one of the fundamental processes controlling the transfer of energy and matter between crust/mantle and ocean; it forms hydrothermal vents where various deepsea biological communities are inhabited and precipitates metal sulfide deposits. Hydrothermal systems at convergence plate boundaries show diverse geochemical properties due to recycle of subducted material compared to simple systems at mid-ocean ridges. Sulfur isotopes can be used to evaluate such diversity in generation and evolution of hydrothermal system. In this paper, we review the sulfur isotope composition and geochemistry of hydrothermal precipitates sampled from several hydrothermal vents in the divergent plate boundaries in the western Pacific region. Both sulfide and sulfate minerals of the hydrothermal vents in the arc and backarc tectonic settings commonly show low sulfur isotope compositions, which can be attributed to input of magmatic $SO_2$ gas. Diversity in geochemistry of hydrothermal system suggests an active role of magma in the formation of seafloor hydrothermal system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.397-402
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• 2016

To produce adequate electricity in nuclear and thermal power plants, an optimal amount of steam should be supplied to a generator connected to high- and low-pressure steam turbines. A turbine output control device, which is a special steam valve employed to supply or interrupt the steam to the turbine, is operated using a hydraulic servo actuator. In power plants, the performance of servo actuators is degraded by the air generated from the hydraulic system, or causes frequent failures owing to an increase in the wear of the seal. This is due to the seal being burnt as generated heat using the produced compressed air. Some power plants have exhausted air using a fixed orifice, and thus they encounter power loss due to mass flow exhaust. Failures are generated in hydraulic pumps, electric motors, and valves, which are frequently operated. In this study, we perform modeling and analysis of the load-sensing air-exhaust valves, which can be passed through very fine flow under normal use conditions, and exhaust mass flow air at the beginning stage as with existing fixed orifices. Then, we propose a method to prevent failures due to the compressed air, and to ensure the control accuracy of hydraulic servo actuators.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.4
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• pp.468-475
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• 2019

An end-line flame arrester allows free venting in combination with flame protection for vertical vent applications. End-line flame arresters are employed in various fields, especially in shipping. In flame arresters, springs are essential parts because the spring load and the spring's elasticity determine the hood opening moment. In addition, the spring has to work under a high-temperature condition because of the burning gas flame. Therefore, it is necessary to analyze the mechanical load and elasticity of the spring when the flame starts to appear. Based on simulations of the working process of a specific end-line flame arrester, a thermal and structural analysis of the spring is performed. A three-dimensional model of a burned spring is built using computational fluid dynamics (CFD) simulation. Results of the CFD analysis are input into a finite element method simulation to analyze the spring structure. The research team focused on three cases of spring loads: 43, 93, and 56 kg, correspondingly, at 150 mm of spring deflection. Consequently, the spring load was reduced by 10 kg after 5 min under a $1,000^{\circ}C$ heat condition. The simulation results can be used to predict and estimate the spring's load and elasticity at the burning time variation. Moreover, the obtained outcome can provide the industry with references to optimize the design of the spring as well as that of the flame arrester.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.1
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• pp.19-27
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• 2012

The open-top chamber (OTC) system is designed for long term studies on the climate change impact on the major tree species and their community in Korea. In Korea Forest Research Institute (KFRI), the modified OTC system has been operating since September 2009. The OTC facility consists of six decagon chambers (10 meters in diameter by 7 meters high) with controlled gas concentration. In each chamber, a series of vertical vent pipes are installed to disperse carbon dioxide or normal air into the center of the chamber. The OTC is equipped with remote controlled computer system in order to maintain a stable and elevated concentration of carbon dioxide in the chamber throughout the experimental period. The experiment consisted of 4 treatments: two elevated $CO_2$ levels ($1.4{\times}$ and $1.8{\times}$ ambient $CO_2$) and two controls (inside and outdoors of the OTC). Average operational rate was the lowest (94.2%) in June 2010 but increased to 98% in July 2010 and was 100% during January to December 2011. In 2010~2011, $CO_2$ concentrations inside the OTCs reached the target programmed values, and have been maintained stable in 2011. In 2011, $CO_2$ concentrations of 106%, 100% and 94% of target values has been recorded in control OTC, $1.4{\times}$ $CO_2$-enriched OTC and $1.8{\times}$ $CO_2$-enriched OTC, respectively. With all OTC chambers, the difference between outside and inside temperatures was the highest ($1.2{\sim}2.0^{\circ}C$) at 10 am to 2 pm. Temperature difference between six OTC chambers was not detected. The relative humidity inside and outside the chambers was the same, with minor variations (0~1%). The system required the highest amount of $CO_2$ for operation in June, and consumed 11.33 and 17.04 ton in June 2010 and 2011, respectively.