• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.22-26
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• 2010

Recently, due to the tremendous growth of media technology, demands of the aspheric glass lens which is a high-performance and miniaturized increase gradually. Generally, the aspheric glass lens is manufactured by Glass Molding Press (GMP) method using tungsten carbide (WC) mold core. In this study, the thermal deformation which was occurred by GMP process was analyzed and applied it to compensate the aspheric glass lens. The compensated lens was satisfied that can be applied to the actual specifications.

• Macromolecular Research
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• v.9 no.3
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• pp.143-149
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• 2001

Poly(aspartic acid), PASP, is a biodegradable, water-soluble polymer and offers a biodegradable alternative to polycarboxylates and other non-degradable water-soluble polymers. PASP one of poly (amino acid)s, possesses carboxylic acid pendant group in its repeating unit, which can be used for various further modification purposes. In this study we prepared high molecular weight polysuccinimide, as the precursor polymer for PASP, by thermal polycondensation ofL-aspartic acid in the presence of phosphoric acid. The polysuccinimide was hydrolyzed with 0.1 N sodium hydroxide, and then acidified to give PASP. High water-absorbent gels were produced by thermal crosslinking of freeze-dried mixture of partially-neutralized PASP and different amount of low moi. wt. PEG-diepoxide compounds in aqueous medium. The swelling behavior of the prepared gels from different size and composition of crosslinking reagent in different media was investigated and the results were discussed. This PASP-based hydrogel materials possessing inherent biodegradability, potential non-toxicity and biocompatibility, is expected to be used as a substrate for various biomedical applications as well as a general purpose super-absorbent polymer.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.232-239
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• 2011

Fabric fibrous filter has been used in various industrial applications owing to the low cost and wide generality. However, the basic properties of fabric materials often limit the practical utilization including hot gas cleaning. This study attempts to find new coatings of porous fibrous filter media in order to overcome its insufficient thermal resistance and durability. Teflon was one of the plausible chemicals to supplement the vulnerability against frequent external thermal impacts. A foaming agent composed of Teflon and some organic additives was tentatively coated on the glass fiber mat. The present test Teflon foam coated filter was fount to be useful for hot gas cleaning, up to $250^{\circ}C$-$300^{\circ}C$. Close examination using XPS(X-ray Photoelectron Spectroscopy) and Contact angle proved the binding interactions between carbon and fluorine, which implies coating stability. The PTFE/Glass foam coated filter consisted of more than 95% (C-F)n bond, and showed super-hydrophobic with good-oleophobic characteristics. The contact angle of liquid droplets on the filter surface enabled to find the filter wet-ability against liquid water or oil.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.352-359
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• 2003

The present study has been conducted for manufacturing MPCM (microencapsulated phase change material) slurry with in-situ polymerization and proving their applicabilities for tooling system. The surface of MPCM is composed of melamine, while tetradecane, paraffin wax, is centered in the MPCM. The produced capsules are observed by the optical microscope and SEM for superficial shapes. Their thermal properties are measured by DSC. Their size distributions are observed by FA particle analyzer. A narrow size distribution from 1 to 10 ${\mu}{\textrm}{m}$ with 5 ${\mu}{\textrm}{m}$ of average diameter was observed. Melting temperature was 6.7$^{\circ}C$. The durability of MPCM was tested with various types of pump such as centrifugal, peristaltic, and mono pumps. During 10000 cycles the fraction of broken capsules was smaller than 6% for the centrifugal and peristaltic pumps, while bigger value of 8% for the mono pump. A cooling system, which adopted MPCM slurry as a media for transporting cold thermal energy, was designed to investigate the performance of the MPCM. The discharging times of 10 and 20 wt% MPCM slurry were lasted up to 105 and 285 minutes longer, respectively, than the water cooling system.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.601-605
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• 1995

Magnetic properties of FeTaN and FeTaC films deposited by DC magnetron reactive sputter were investigated, and correlated with their microstructures. The optimum magnetic properties of Hc : 0.25 Oe, Bs : 14.5 kG, and ${\mu}'$ : 4000 (5MHz) are observed in the $Fe_{78.8}Ta_{8.5}N_{12.7}$ film, and Hc : 0.25 Oe, Bs : 14.5 kG, and ${\mu}'$ : 2700 (5MHz) in the $Fe_{75.6}Ta_{8.1}C_{16.3}$ film. In both FeTaN and FeTaC films with minimum grain size show the best soft magnetic properties. Thermal stability of the soft magnetic properties of FeTaN is found to be higher than FeTaC for similar compositons. TaN and TaC particles form to retard the growth of $\alpha$-Fe grains. TaN particles in FeTaN show higher efficiency in retarding the grain growth during heat treatments resulting the higher thermal stability, compared to TaC particles in FeTaC films.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.466-475
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• 2017

Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal-hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.454-454
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• 2022

Residents near the fire site are more anxious as they rely only on media information and the government's evacuation order due to the lack of information to understand the progress of the wildfire. Therefore, in the event of a wildfire, we try to understand the inconvenience of not being able to know the progress of the fire and solve it. This makes it possible to check the progress of wildfires and the spread of debris using the system interface (API) and weather data of the thermal infrared satellite image data (NASA FIRMS, Fire Information for Resource Management System), and finally, the purpose of this study. The results are provided through the Web including GIS-based visualization to provide decision-making reference information for evacuation in the event of a forest fire from the perspective of residents.

• Computers and Concrete
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• v.33 no.1
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• pp.91-102
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• 2024

Beam-shaped components commonly rotate along a fixed axis when massive mechanical structures like rotors, jet engine blades, motor turbines, and rotating railway crossings perform their functions. For these structures to be useful in real life, their mechanical behavior is essential. Therefore, this is the first article to use the modified shear deformation theory type hyperbolic sine functions theory and the FEM to study the static bending response of rotating functionally graded GPL-reinforced composite (FG-GPLRC) beams with initial geometrical deficiencies in thermal media. Graphene platelets (GPLs) in three different configurations are woven into the beam's composition to increase its strength. By comparing the numerical results with those of previously published studies, we can assess the robustness of the theory and mechanical model employed in this study. Parameter studies are performed to determine the effect of various geometric and physical variables, such as rotation speed and temperature, on the bending reactions of structures.

• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.169-182
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• 2015

Aeronautics engine cooling is one of the biggest problems that engineers have tried to solve since the beginning of human flight. Systems like radiators should solve this purpose and they have been studied extensively and various solutions have been found to aid the heat dissipation in the engine zone. Special interest has been given to air coolers in order to guide the air flow on engine and lower the high temperatures achieved by the engine in flow conditions. The aircraft companies need faster and faster tools to design their solutions so the development of tools that allow to quickly assess the effectiveness of an cooling system is appreciated. This paper tries to develop a methodology capable of providing such support to companies by means of some application examples. In this work the development of a new methodology for the analysis and the design of oil cooling systems for aerospace applications is presented. The aim is to speed up the simulation of the oil cooling devices in different operative conditions in order to establish the effectiveness and the critical aspects of these devices. Steady turbulent flow simulations are carried out considering the air as ideal-gas with a constant-averaged specific heat. The heat exchanger is simulated using porous media models. The numerical model is first tested on Piaggio P180 considering the pressure losses and temperature increases within the heat exchanger in the several operative data available for this device. In particular, thermal power transferred to cooling air is assumed equal to that nominal of real heat exchanger and the pressure losses are reproduced setting the viscous and internal resistance coefficients of the porous media numerical model. To account for turbulence, the k-${\omega}$ SST model is considered with Low- Re correction enabled. Some applications are then shown for this methodology while final results are shown in terms of pressure, temperature contours and streamlines.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.722-728
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• 1997

This study was investigated to find storage material of thermal energy storage system for a vehicle with the basic material of $Ba(OH)_2{\cdot}8H_2O$ and to test a feasibility of it. Experiment was investigated usability for long time and state change and thermal property after cycle with $Ba(OH)_2{\cdot}8H_2O$ and misxture doping additive to it. The result of this research indicated the mixture adding $Sr(OH)_2{\cdot}8H_2O$ to $Ba(OH)_2{\cdot}8H_2O$ have high feasibility as storage material for thermal energy storage system. This mixture did not exhibit the state change during 1300 cycles and the rate of decrease of heat realese energy was about 2%, relatively low value.