• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.713-721
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• 2004

Variable air intake and variable exhaust nozzle of hypersonic engines are designed and tested in this study. Dimensions for variable geometry air intake, ram combustor and variable geometry exhaust nozzle are defined based on the requirements of a pre-cooled turbojet engine. Hypersonic Ramjet Engine is designed as a scaled test bed for each component. Actuation forces of moving parts for variable intake and variable nozzle are reduced by balancing the other force in the opposite direction. A demonstrator engine which includes variable intake and variable nozzle is designed and the components are fabricated. Composite material with silicone carbide is applied for high temperature parts under oxidation environment such as leading edge of the variable intake and combustor liner. Internal cooling structure is adopted for both moving and static parts of the variable nozzle. Pressure recovery and mass capture ratio of the variable intake at Mach 5 is obtained by a hypersonic wind tunnel test. Flow characteristics of the variable nozzle are obtained by a low temperature flow test. Wall temperature and heat flux of the nozzle at Mach 3 is obtained by a firing test. As results, the intake and the nozzle are proved to be used at designed pressure and temperature environment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.4
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• pp.503-509
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• 2021

Objectives: The utility of the system was analyzed by applying the smart safety technology system to the aging pipe rehabilitation facility construction classified as a confined space. Methods: Smart safety management system was applied to a site where the aging pipe rehabilitation work was in progress. The working environment was measured for 25 days, and the toxic gas saturation was analyzed according to the working time and working place. Results: Based on the measured results, two characteristic environmental changes in the confined space were confirmed. First, when working inside an aging pipe, the tendency of carbon dioxide saturation increases with working time and the number of workers. Second, oxygen decreases when working in a space away from the entrance. Conclusions: Various applications of smart safety technology have been confirmed based on the measured data, and this is expected to be useful for environmental characteristic analysis and safety management when applied to a confined space composed with various conditions in the future.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.364-372
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• 2023

The space reactor is the primary energy supply for future space vehicles and space stations. The radiator is one of the essential parts of a space reactor. Therefore, the research on radiators can improve the heat dissipation power, reduce the quality of radiators, and make the space reactor smaller. Based on MOOSE multi-physics numerical calculation platform, a simulation program for the combination of heat pipe and fin at the end of heat pipe radiator is developed. It is verified that the calculation result of this program is accurate and the calculation speed is fast. Analyze the heat transfer characteristics of the combination with heat pipe and fin, and obtain its internal temperature field. Based on the calculation results, the influence of structural parameters on the heat dissipation power is analyzed. The results show that when the fin width is 0.25 m, fin thickness is 0.002 m, condensing section length is 0.5425 m and heat pipe radius is 0.014 m, the power-mass ratio is the highest. When the temperature is 700K-900K, the heat dissipation power increases 41.12% for every 100K increase in the operating temperature. Smaller fin width and thinner fin thickness can improve the power-mass ratio and reduce the radiator quality.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.48-58
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• 2008

• Bulletin of the Korean Space Science Society
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• 1995.10a
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• pp.27-27
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• 1995

No Abstract, See Full Text

• Bulletin of the Korean Space Science Society
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• 1995.10a
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• pp.38-38
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• 1995

No Abstract, See Full Text

• Journal of the Korean Mathematical Society
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• v.46 no.3
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• pp.621-642
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• 2009

In this paper we give necessary and sufficient conditions that two Toeplitz operators with monomial symbols acting on the weighted Bergman space commute. We also present necessary and sufficient conditions for the hyponormality of Toeplitz operators with some special symbols on the weighted Bergman space. All the results are stated in terms of the Mellin transform of the symbol.

• East Asian mathematical journal
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• v.24 no.4
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• pp.359-368
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• 2008

The object of this paper is to establish a unique common fixed point theorem through weak compatibility for a sequence of self-maps satisfying a generalized contractive condition in a generalized Menger space. It improves and generalizes the result of Milovanovic-Arandelovic [2], Vasuki [10] and Sehgal and Bharucha-Reid [8]. All the results presented in this paper are new.

• The Bulletin of The Korean Astronomical Society
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• v.32 no.1
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• pp.34.2-34.2
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• 2007

• Communications of the Korean Mathematical Society
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• v.31 no.3
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• pp.647-656
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• 2016

In this paper, we define the generalized golden shaped hypersurfaces in Lorentz space forms. Based on the classification of proper semi-Riemannian hypersurfaces in semi-Riemannian real space forms, we obtain the whole families of the generalized golden shaped hypersurfaces in Lorentz space forms.