• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.29-33
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• 2022

Recently, development of a cryogenic fluids storage tank for storing or transporting liquid hydrogen is actively in progress. In cryogenic fluids storage tanks, hydrogen evaporates due to the extreme temperature difference inside and outside the tank. As the mass of the cryogenic fluids changes with continuous vaporization, the fluids level also changes. Therefore, there is need for a method of accurately measuring the level change in the storage tank. In the case of general cryogenic fluids, it is difficult to accurately measure the level because the dielectric constant is very low. As a method of measuring cryogenic fluids level with low dielectric constant, it can be used an Millimeter wave (MM wave) FMCW radar sensor. However, the signal sensitivity is very weak and the level accuracy is poor. In this paper, the signal sensitivity is improved by designing the horn lens antenna of the existing 80 GHz FMCW radar sensor. Horn lens antenna is fabricated by FDM/SLA type 3D printer according to horn and lens characteristics. The horn is used to increase the signal gain and the lens improves the signal straightness. This makes it possible to measure the level of cryogenic fluids with a low dielectric constant.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.66-72
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• 2022

The Mooney-Rivlin second order optimal strain energy function derived through uniaxial tensile test and analysis was applied to a gasket to confirm the internal stress and surface pressure generated during compression. The Taguchi method, a statistical technique, was used to design the optimum shape of the gasket, and through characteristic evaluation, the optimum shape of the gasket was obtained when the reference plane (T: 0.15 mm), contact surface (W: 1.00 mm), and curvature (R: 0.30 mm) were used. It was determined that the optimum shape yields a von Mises stress of 4.83 MPa, and the contact pressure stress is 20.14 MPa, which satisfies breakage and sealing requirements. In the future, we plan to manufacture a jig that can measure surface pressure to conduct comparative verification studies between the test results and analysis results.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.477-481
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• 2002

This paper reports on the development of micro power system component under way at Seoul National University. The need of micro power system is explained and components of micro power system are described. The developments of hydrogen-air micro combustor, micro igniter based poly-silicon heater and micro thruster are described. To manufacture 3-D micro structure the process that manufactures high aspect ratio structures has been developed and optimized. Design, fabrication, and experiment processes are introduced and technical challenges in each phase are described.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.29-39
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• 1998

It is well known for 410L ferritic stainless steel powder to applicate a sensor ring in anti-lock brake system of automobile, several studies, because of its excellent magnetic properties. This study was carried out In investigate the magnetic properties such as the maximum magnetic induction, coercivity and maximum permeability of the materials with functions of sintering density! time and temperature, and concluded as follows； 1. Sintering under the circumstances of hydrogen gas and tile temperature of $1250^{\circ}C$ for 60min. showed that nitrogen was increased, whereas carbon and oxygen decreased in quantities. 2. Both maximum magnetic induction value of 4700Gauss and permeability of 200 were obtained at the maximum sintering density of 6.89g/$cm^3$. Here, the properties showed a linear increasement with increasing the sintering density. 3. Coercivity sharply increased with incresing the sintering density and reached to 7.6Oe at the maximum sintering density of 6.89g/$cm^3$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.169-170
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• 2006

Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance-processing route has allowed the more consistent production of existing products, and has allowed enhanced properties, such as improved green strength and green density. This paper will review these processing changes along with the potential new products that are being developed utilizing this technology. These include high strength stainless steels such as duplex and dual phase as well as stainless steel powders used in high temperature applications such as diesel filters and fuel cells.

• The Journal of Korean Medicine
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• v.30 no.5
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• pp.146-156
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• 2009

Objectives: The objective of this study was to investigate the antioxidant effects of manufactured Wen-pi-tang-Hab-Wu-ling-san (WHW$^{(R)}$) in vitro. Methods: WHW$^{(R)}$ was prepared by the pilot manufacture of WHW water extract from a GMP system appointed company. Antioxidative activities were determined by in vitro tests as follows: the scavenging activities of oxygen free radicals including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide anion, hydrogen peroxide and nitric oxide radicals, as well as ferrous ion chelating capacity and Trolox equivalent antioxidant capacity (TEAC). Results: WHW$^{(R)}$ significantly scavenged oxygen free radicals such as DPPH (IC$_{50}$=115.28 $\pm$ 0.25 $\mu$g/$m\ell$), superoxide anion (IC$_{50}$=8.56 $\pm$ 0.08 $\mu$g/$m\ell$), hydrogen peroxide (IC$_{50}$=240.36 $\pm$ 3.41 $\mu$g/$m\ell$) and nitric oxide (IC$_{50}$=162.28 $\pm$ 0.21 $\mu$g/$m\ell$) radicals. WHW$^{(R)}$ also showed ferrous ion chelating activity (IC$_{50}$=543.19 $\pm$ 4.85 $\mu$g/$m\ell$) and Trolox equivalent effects (IC$_{50}$=45.311 $\mu$g/$m\ell$) in TEAC and ORAC assay, respectively. Conclusion: This study demonstrates that WHW$^{(R)}$ has strong antioxidative properties through free radical scavenging activity. These data suggest that WHW$^{(R)}$ be used as an antioxidant agent.

• Applied Biological Chemistry
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• v.25 no.3
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• pp.166-172
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• 1982

The changes of hydrogen ton concentration, viscosity and free sugars in the water-soluble mucilage of Ulmus Coreana, Nakai root upon storage at 10^{\circ}C were studied. Hydrogen ion concentration in the mucilage changed $pH7{\rightarrow}pH4{\rightarrow}pH6$ or 7. The viscosity of mucilage decreased very slowly. The mucilage contained glucose and galacturonic acid. The hydrolyzed products of mucilage consisted of rhamnose, mannose, galactose, arabinose, xylose, glucose and galacturonic acid.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.204-211
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• 2006

The electrolyte in the solid oxide fuel cell must be dense enough to avoid gas leakage and thin enough to reduce the ohmic resistance. In order to manufacture the thin and dense electrolyte layer, 8 mol% $Y_2O_3$ stabilized-$ZrO_2$ (8YSZ) electrolyte layers were coated on the porous tubular substrate by the novel vacuum slurry dip-coating process. The effects of the slurry concentration, presintering temperature, and vacuum pressure on the thickness and the gas permeability of the coated electrolyte layers have been examined in the vacuum slurry coating process. The vacuum-coated electrolyte layers showed very low gas permeabilities and had thin thicknesses. The single cell with the vacuum-coated electrolyte layer indicated a good performance of $495\;mW/cm^2$, 0.7 V at $700^{\circ}C$. The experimental results show that the vacuum dip-coating process is an effective method to fabricate dense thin film on the porous tubular substrate.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.2
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• pp.5-18
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• 2023

As a result of the survey on the emission status of fluorine-based chemicals in Korea, 13 kinds of substances, including hydrogen fluoride (91%) and perfluorocarbons (5%), were emitted in workplaces. By regional groups, about 98% was emitted in the Gyeongbuk, Gyeonggi and Chungcheong regions, and about 98% in three sectors of industry related to manufacture of electronic parts, chemicals and non-metallic mineral products. The detection status of PFOS and PFOA in domestic main rivers was continuously detected in the Nakdong River, the Geum River and the Anseong Stream estuary with high fluorine-related chemical emissions, and four sites of PFOS and two sites of PFOA were detected for the first time in 2021. PFOS and PFOA were continuously detected in relatively high concentrations in the rivers where there were many semiconductor and display related sectors of industry.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.229-234
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• 2008

Korea Electric Power Corporation (KEPCO) has started the nation's first biogas-microturbine project in the city of Gongju as an effort to encourage the utilization of wasted biogas containing useful energy source in the form of $CH_4$. The goal of the project is to set up the biogas microturbine co-generation system for utilizing biogas as an energy source and improving the economics of the wastewater treatment plant. Wastewater treatment processes were investigated in depth to find improvement possibility. Changes in internal recirculation ratio and pre-treatment degree are needed to optimize plant operation and biogas production. Biogas pre-treatment system satisfies Capstone's fuel condition requirement with the test result of 99.9% and 90.2% of hydrogen sulphide and ammonia is removal performance. Installation of microturbine and manufacture of heat exchanger to warm anaerobic digester has been done successfully. Expected economic profit produced by the system is coming from energy saving including electricity 115,871kWh/year and heat contained in exhaust gas 579GJ/year.