• Korean Journal of Materials Research
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• v.28 no.4
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• pp.201-207
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• 2018

Infrared(IR) heating has many advantages, such as energy efficiency, reduced heating time, cleanliness, equipment compactness, high drying rate and easy automation. These features of IR heating provide widely industrial applications, such as surface heat treatment in semiconductor fabrication, thermoforming of polymers, drying and disinfection of food products, heating to metal forging, and drying of wet materials. In this study, the characteristics of a protected gold mirror were examined by spectrophotometer and the lifetime of the coating layers were evaluated by a cross-cutting method and salt spray test. The effects of manufacturing conditions on the protected gold mirror were seen and remedies for these effects were noted in order to improve the properties of the protected gold mirror in the drying process. The reflectance and lifetime of the protected gold mirror was influenced by manufacturing conditions, such as surface roughness and forming conditions of the anti-oxide layer, the adhesion layer, the reflecting layer and the protection layer. The results of this study showed that the protected gold mirror manufactured using a buffing method for pre-treatment resulted in the most effective reflectance. In addition, $Al_2O_3$ coating on an Al substrate as an anti-oxide layer was more effective than the anodizing process in the test of reflectance. Furthermore, the protected gold mirror manufactured by layers forming of various materials resulted in the most effective reflectance and lifetime when coated with $Al_2O_3$ as the anti-oxide layer, coated Cr as the adhesion layer, and coated $MgF_2$ as the protection layer.

• Journal of Soil and Groundwater Environment
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• v.18 no.6
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• pp.32-37
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• 2013

The scope of this study was to develop, design, and build an ex-situ remediation system of using the heating and water sparging treatment for the highly volatile DNAPL (Dense Non-Aqueous Phase Liquid) contaminated groundwater, and to conduct pilot testing at the site contaminated with DNAPL. The TCE (Trichloroethylene) removal was at the highest rate of 94.6% with the water sparging at $70^{\circ}C$ in the lab-scale test. The pilot-scale remediation system was developed, designed, and fabricated based on the results of the lab-scale test conducted. During the pilot-scale testing, DNAPL-contaminated groundwater was detained at heat exchanger for the certain period of time for pre-heating through the heat exchanger using the thermal energy supplied from the heater. The heating system supplies thermal energy to the preheated DNAPL-contaminated groundwater directly and its highly volatile TCE, $CCl_4$ (Carbontetrachloride), Chloroform are vaporized, and its vaporized and treated water is return edback to the heat exchanger. In the pilot testing the optimum condition of the HWSRS was when the water temperature at the $40^{\circ}C$ and operated with water sparging concurrently, and its TCE removal rate was 90%. The efficiency of the optimized HWSRS has been confirmed through the long-term performance evaluation process.

• Korean journal of food and cookery science
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• v.28 no.6
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• pp.655-663
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• 2012

This study was carried out response surface analysis for brown sauce optimization. Three factors of heating time (10, 20, 30, 40, and 50 min), the added gelatin content (0, 4, 8, 12, and 16%) and the added tomato paste amount (0, 6, 12, 18, and 24%) were encoded into 5 levels (-2, -1, 0, 1, 2). After the central synthesis plan was set up to produce samples in 16 pre-arranged conditions and the sensory tests were conducted, the investigation on optimum level of these factors was conducted. The scope of optimum conditions for extraction was established through reading the range of reaction surfaces superimposed between those representing sensory properties such as color, flavor, taste, viscosity and overall acceptability was established. In this study, it was found out that the scope of optimum conditions for brown sauce extraction was 30 min for heating time, 9.00% for gelatin content and 11.25% for tomato paste amount. The reliability test proved the mentioned scope to have a similar value to that of the estimated scope when compared to the experimental values which was observed through experiments conducted under the same conditions as applied to values predicted through RSM program, enabling the verification of the reliability of derived regression formula.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.34-35
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• 2013

In this study, the ultra high strength concrete which have 80, 130, 180MPa took the heat from 20℃ to 700℃ and the 0, 20% stress in normal condition's to evaluate stress-strain, residual compressive strength and thermal expansion deformation were evaluated. The heating speed of specimen was 0.77℃/min 20~50℃, 50℃ before the target temperature, and the other interval's heating speed was 1℃/min. As a result, the stress-strain curve of non-load specimen showed the liner behavior at high temperature when the specimen's strength increased more. If ultra high strength concrete got loads, its compressive strength tended to decrease different from the normal strength concrete. The thermal expansion deformation was expanded from a vitrification of quartz over 500℃. however, over the 600℃, it was shrinked because of the dehydration of the combined water.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.413-421
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• 2014

Since the structural temperature of a flight vehicle flying at high speed rises rapidly due to aerodynamic heating, it is necessary for optimum structural design to obtain proper material properties at high temperature by taking into account of its operational environment. For a special alloy, analysis data on strength change due to exposure time to high temperature are very limited, and most of them are for an exposure time longer than 30 minutes for long term operations. In this study, base and weld metal samples of Ti-6Al-4V alloy had been prepared and high temperature tensile tests with induction heating were performed, and then high temperature strength characteristics and strength recovery characteristics through cooling have been analyzed. Pre-tests to determine maximum heating rate were performed, and response characteristics for temperature control were confirmed. As a result, high temperature tensile strength appeared to be lower than that of room temperature, but it was higher than that of high temperature of 30 minite exposure listed in MMPDS. In strength recovery through cooling Ti-6Al-4V alloy has shown higher recovery rate compared with other alloys.

• Journal of Powder Materials
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• v.30 no.2
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• pp.116-122
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• 2023

Because magnets fabricated using Nd-Fe-B exhibit excellent magnetic properties, this novel material is used in various high-tech industries. However, because of the brittleness and low formability of Nd-Fe-B magnets, the design freedom of shapes for improving the performance is limited based on conventional tooling and postprocessing. Laser-powder bed fusion (L-PBF), the most famous additive manufacturing (AM) technique, has recently emerged as a novel process for producing geometrically complex shapes of Nd-Fe-B parts owing to its high precision and good spatial resolution. However, because of the repeated thermal shock applied to the materials during L-PBF, it is difficult to fabricate a dense Nd-Fe-B magnet. In this study, a high-density (>96%) Nd-Fe-B magnet is successfully fabricated by minimizing the thermal residual stress caused by substrate heating during L-PBF.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.330-341
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• 1999

An experimental study for the two types of burners used in the non-oxidizing direct fired furnaces of the heat treatment process for the cold rolled plate has been carried out to investigate the combustion characteristics and the oxidization of the surface of steel plate. A steep temperature gradient and entrainment of residual oxygen were found near the heating surface in the flame of the nozzle mixing burner which has strong swirl velocity component. It was concluded that the elimination of the residual oxygen and the increase of the temperature of combustion gas on the heating surface are needed to enhance the performance of the burners for application to the non-oxidizing direct fired furnaces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.695-703
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• 1998

The crack problem of continuous casting slab due to the thermal stresses during the reheating process is analyzed using FEM. In this study, the C(t)-integral is calculated. As a result, the values of the C(t)-integral decrease by increasing the initial temperature of the slab and decreasing total heat flux. And those decrease by decreasing the heat flux of pre-heating zone and increasing the heat flux of heating zone.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.4
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• pp.365-370
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• 2007

This paper studies an automation problem of a heating, a ventilating, and an air conditioning (HVAC) for the development of smart space. The HVAC system is described by the fuzzy system for the stability analysis and the controller design. The linear matrix inequalities (LMIs) conditions are derived for the stabilization problem of the closed-loop system under the analog control. Also, it is required to digitally redesign the pre-designed the analog HVAC control system in order to accomplish the remote control via web. It is shown the this digital redesign problem can be converted to the convex optimization problem with the LMI constraints. An example is provided to show the effectiveness of the proposed method.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.81-85
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• 2012

This work is related to study the thermal decomposition of 1,3,5-trinitro-1,3,5-triazacylohexane(RDX) by differential scanning calorimeter and thermo-gravimetry with Kissinger's & Iso-conversional method under nonisothermal conditions, with heating rate from 2 to $8^{\circ}C$/min or given heating rate. We calculated and compared activation energy with these two methods. Iso-conversional method is better than Kissinger's method to study decomposition mechanism. We also investigated activation energy and frequency factor by Kissinger's & Iso-conversional method with the influence of particle size. In case of single crystal, Cl-3(large crystal) has better thermal stability than Cl-5(small crystal). The activation energy increased according to the size of the particle size.