• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.160-166
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• 2018

The worldwide semi-conductor market has been growing for a long time. Manufacturing lines of semi-conductors need to handle several types of toxic gases. In particular, they need to be controlled accurately in real time. This type of toxic gas control system consists of many different kinds of parts, e.g., fittings, valves, tubes, filters, and regulators. These parts obviously need to be manufactured precisely and be corrosion resistant because they have to control high pressure gases for long periods without any leakage. For this, surface machining and hardening technologies of the metal block and metal gasket need to be studied. This type of study depends on various factors, such as geometric shapes, part materials, surface hardening method, and gas pressures. This paper presents strong concerns on a series of simulation processes regarding the differences between the inlet and outlet pressures considering several different fluid velocity, tube diameters, and V-angles. Indeed, this study will very helpful to determine the important design factors as well as precisely manufacture these parts. The EP (Electrolytic Polishing) process was used to obtain cleaner surfaces, and hardness tests were carried out after the EP process.

• Journal of the Korean Institute of Gas
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• v.21 no.1
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• pp.43-51
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• 2017

Recently, ammonia leak occurred frequently in the domestic refrigeration manufacturing facilities. Ammonia caused great damage to the environment and human health in the event of an accident as combustible gases and toxic gases. After considering the types of ammonia accidents of domestic refrigeration manufacturing facilities and selected accident scenarios and to analyze the risk analysis through Impact range estimates and frequency analysis and there was a need to establish measures to minimize accident damage. In this study, depending on the method of analysis quantitative risk assessment we analyzed the risk of the receiver tank of ammonia system. Scenario analysis conditions were set according to the 'Technical guidelines for the selection of accident scenario' under the chemicals control act and 'Guidelines for chemical process quantitative risk analysis' of center for chemical process safety. The risk estimates were utilized for consequence analysis and frequency analysis by SAFETI program of DNV, event tree analysis methodology and part count methodology. The individual risk of ammonia system was derived as 7.71E-04 / yr, social risk were derived as 1.17E-03 / yr. The derived risk was confirmed to apply as low as reasonably practicable of the national fire protection association and through risk calculation, it can be used as a way to minimize accidents ammonia leakage accident damage.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.262-270
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• 2021

Consumption of Liquefied Natural Gas (LNG) has increased due to environmental pollution; therefore, the need for LNG carriers can efficiently transport large quantities of LNG, is increased. In various types of LNG Cargo Containment System (CCS), Membrane-type MARK-III composed of composite materials is generally employed in the construction of an LNG carrier. Among composite materials in a Mark-III system, glass-fiber composites act as a secondary barrier to prevent the inner hull structure from leakage of LNG when the primary barrier is damaged. Nevertheless, several cases of damage to the secondary barriers have been reported and if damage occurs, LNG can flow into the inner hull structure, causing a brittle fracture. To prevent those problems, this study conducted the applicability assessment of composite material manufactured by bonding glass-fiber and aluminum with epoxy resin and increasing layer from three-ply (triplex) to five-ply (pentaplex). Tensile tests were performed in five temperature points (25, -20, -70, -120, and -170℃) considering temperature gradient in CCS. Scanning Electron Microscopy (SEM) and Coefficient of Thermal Expansion (CTE) analyses were carried out to evaluate the microstructure and thermos-mechanical properties of the pentaplex. The results showed epoxy resin and increasing layer number contributed to improving the mechanical properties over the whole temperature range.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.22-27
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• 2021

This paper is a purpose to study the failure examples for LPG vehicle. The first example, the researcher certified the incongruity phenomenon decreased engine power by ignition fire leakage because of spark plug threaded part damage assembling in cylinder head. The second example, the timing mark that accurately adjusting the camshaft and crankshaft position were twisted about 0.5 block each other. Finally, the researcher seeked the disharmony phenomenon as it couldn't set ignition timing. The third example, the researcher knew the failure phenomenon by interrupted the closing period for intake valve moving with air flow in the number 3 port of cylinder head as the foreign substance in cylinder head didn't remove. Therefore, the manager of a car has to thorough going inspect and the manufacture of a car must remove the cause of failure with quality assurance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.238-247
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• 2023

Liquefied petroleum gas (LPG) is an attractive fuel for ships considering its current technology and economic viability. However, safety guidelines for LPG-fueled ships are still under development, and there have been no cases of applying LPG propulsion systems to small and medium-sized ships in Korea. The purpose of this study was to perform an objective risk assessment for the first marine LPG engine system and propose safe operational standards. First, hazard and operability (HAZOP) analysis was used to divide the engine system into five nodes, and 58 hazards were identified. To compensate for the subjectivity of qualitative evaluation using HAZOP analysis, fuzzy set theory was used, and additional risk factors, such as detectability and sensitivity, were included to compare the relative weights of the risk factors using a fuzzy analytical hierarchy process. As a result, among the five risk factors, those with a major impact on risk were determined to be the frequency and severity. Finally, the fuzzy technique for order of preference by similarity to ideal solution (TOPSIS) was applied to select the risk rank more precisely by considering the weights of the risk factors. The risk level was divided into 47 groups, and the major hazard during the operation of the engine system was found through the analysis to be gas leakage during maintenance of the LPG supply line. The technique proposed can be applied to various facilities, such as LPG supply systems, and can be utilized as a standard procedure for risk assessment in developing safety standards for LPG-powered ships.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.158-159
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• 2022

Due to the climate crisis, various environmental regulations including greenhouse gas reduction are in effect. This is not limited to any specific industry sector, but is affecting the entire industry worldwide. For this reason, the IMO and governments of each country are announcing strategies and policies related to the shipbuilding and shipping industries. The current regulations can be partially resolved through additional facilities such as scrubbers while using existing fossil fuels, but ultimately, the emission of greenhouse gases such as CO2 from the exhaust gases generated by ships must be restricted through energy conversion. To this end, it is necessary to develop fuels that can replace traditional fuels such as oil and natural gas. Among them, hydrogen is attracting attention as a clean energy that does not emit pollutants when used as a fuel. However, hydrogen has a wide explosive range and a fast dispersion speed, so research on this is necessary. Therefore, in this paper, when hydrogen leakage occurs in the fuel preparation room of a hydrogen-powered ship, the trend was analyzed and the ventilation characteristics were investigated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.964-970
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• 2023

As part of the International Maritime Organization ef orts to reduce greenhouse gas emissions, the maritime industry is exploring low-carbon fuels such as liquefied natural gas and methanol, as well as zero-carbon fuels such as hydrogen and ammonia, evaluating them as environmentally friendly alternatives. Particularly, ammonia has substantial operational experience as cargo on transport ships, and ammonia ship engines are expected to be available in the second half of 2024, making it relatively accessible for commercial use. However, overcoming the toxicity challenges associated with using ammonia as a fuel is imperative. Detection is possible at levels as low as 5 ppm through olfactory senses, and exposure to concentrations exceeding 300 ppm for more than 30 min can result in irreparable harm. Using the KORA program provided by the Chemical Safety Agency, an assessment of the potential risks arising from leaks during ammonia bunkering was conducted. A 1-min leak could lead to a 5 ppm impact within a radius of approximately 7.5 km, affecting key areas in Busan, a major city. Furthermore, the potentially lethal concentration of 300 ppm could have severe consequences in densely populated areas and schools near the bunkering site. Therefore, given the absence of regulations related to ammonia bunkering, the potential for widespread toxicity from even minor leaks highlights the requirement for the development of legislation. Establishing an integrated system involving local governments, fire departments, and environmental agencies is crucial for addressing the potential impacts and ensuring the safety of ammonia bunkering operations.

• Journal of Bio-Environment Control
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• v.20 no.3
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• pp.227-232
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• 2011

The processing techniques are need to use the non-marketable paprika fruit because paprika that is difficult crop for cultivation and produced easily non-marketable fruits, such as physiological disorder fruit, malformed fruit, and small size fruit. This study was carried out to investigate the proper active modified atmosphere packaging (MAP) condition for enhancing the storability of fresh-cut paprika fruit. The fresh-cut paprika (cv 'Score', seminis) put into $7cm{\times}0.7cm$ size and packed them in 20 g bags. The active MAP and vacuum treated paprika fruits were packaged with LLDPE/Nylon, EVOH, Tie film, and injected partial pressures of $CO_2$ and $O_2$, and $N_2$ in the packages immediately after sealing to treat active MAP. The ratio of $CO_2$, $O_2$, and $N_2$ of active MAP conditions were 0 : 20 : 80 (air), 5 : 5 : 90, 30 : 10 : 60, 10 : 70 : 20 and vacuum treatment did not contain any gas. The passive packaging treated paprika packaged with $40{\mu}m$ ceramic film. After 7 days of storage at $9^{\circ}C$, the fresh weight decreased less than 2% in all treatments, and showed lower in 5 : 5 : 90 ($CO_2:O_2:N_2$) active-MAP treatment and higher in vacuum treatment than other treatments. The $CO_2$ and $O_2$ concentration in packages did not change remarkably in active-MA treatments except 30 : 10 : 60 active-MAP treatment that showed sharply decreased $O_2$, concentration and increased $CO_2$ concentration at $1^{st}$ day of storage at $9^{\circ}C$. The ethylene concentration in package was the highest in 30 : 10 : 60 active-MAP treatment and the lowest in the passive MAP treatment that packaged with gas permeable film during $9^{\circ}C$ storage for 7 days. The 30 : 10 : 60 active-MAP treatments were not proper condition to storage fresh-cut paprika. The visual quality was maintained higher in 0 : 20 : 80 (air), 5 : 5 : 90, and 10 : 70 : 20 active MAP treatments and passive MAP treatment than others and the firmness, off-odor, and electrolyte leakage was investigated at 7th day of storage at $9^{\circ}C$. The 5 : 5 : 90 and 10 : 70 : 20 active-MAP treatment showed higher firmness and lower off-odor than other treatments after $7^{th}$ day of storage at $9^{\circ}C$. In addition, the electrolyte leakage was reduced less than 20% at 0 : 20 : 80 (air), 5 : 5 : 90, 10 : 70 : 20, and passive MA treatments. Therefore, 10 : 70 : 20 ($CO_2:O_2:N_2$) and 0 : 20 : 80 (air) might be recommended for proper active MAP conditions.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.754-762
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• 1995

Strontium titanate(SrTiO$_3$) thin film was prepared on Si substrates by RF magnetron sputtering for a high capacitance density required for the next generation of LSTs. The optimum deposition conditions for SrTiO$_3$thin film were investigated by controlling the deposition parameters. The crystallinity of films and the interface reactions between SrTO$_3$film and Si substrate were characterized by XRD and AES respectively. High quality films were obtained by using the mixed gas of Ar and $O_2$for sputtering. The films were deposited at various bias voltages to obtain the optimum conditions for a high quality file. The best crystallinity was obtained at film thickness of 300nm with the sputtering gas of Ar+20% $O_2$and the bias voltage of 100V. The barrier layer of Pt(100nm)/Ti(50nm) was very effective in avoiding the formation of SiO$_2$layer at the interface between SrTiO$_3$film and Si substrate. The capacitor with Au/SrTiO$_3$/Pt/Ti/SiO$_2$/Si structure was prepared to measure the electric and the dielectric properties. The highest capacitance and the lowest leakage current density were obtained by annealing at $600^{\circ}C$ for 2hrs. The typical specific capacitance was 6.4fF/$\textrm{cm}^2$, the relative dielectric constant was 217, and the leakage current density was about 2.0$\times$10$^{-8}$ A/$\textrm{cm}^2$ at the SrTiO$_3$film with the thickness of 300nm.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.199-203
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• 2000

$Ta_2_O5$ and $Sr_0.8Bi_2.4Ta_2O_9$ films were deposited on p-type Si(100) substrates by a rf-magnetron sputtering and the metal organic decomposition (MOD), respectively.The electrical characteristics of the $Pt/SBT/Ta_2O_5/Si$ structure were obtained as the functions of $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering and $Ta_2_O5$ thickness. And to certify the role of $Ta_2_O5$ as a buffer layer, the electrical characteristics of $Pt/SBT/Ta_2O_5/Si$ were compared. $Pt/SBT/Ta_2O_5/Si$ capacitor with 20% $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering did now show typical C-V curve of metal/ferroelectric/insulator/semiconductor (MFIS) structure. The capacitor with 20% $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering had the largest memory window. And the memory window was decreased as the $Ta_2_O5$ gas flow ratio during the $Ta_2_O5$ sputtering was increased to 40%, 60%. In the C-V characteristics of the $Pt/SBT/Ta_2O_5/Si$ capacitors with the different $Ta_2_O5$ thickness, the capacitor with 26nm thickness of $Ta_2_O5$ had the largest memory window. The C-V and leakage current characteristics of the Pt/SBT/Si structure were worse than those of $Pt/SBT/Ta_2O_5/Si$ structure. These results and Auger electron spectroscopy (AES) measurement showed that $Ta_2_O5$ films as a buffer layer tool a role to prevent from the formation of intermediate phase and interdiffusion between SBT and Si.