• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.481-486
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• 2021

In a hypersonic vehicle to solve the heat problem generated during flight, a cooling technology is being developed which uses the endothermic effect that appears during the decomposition reaction of the mounted fuel. In this study, the decomposition reaction of n-dodecane fuel was performed using HZSM-5 as a catalyst, and the catalyst was coated on metal foam to maximize the endothermic effect of the catalytic decomposition reaction and suppress coke formation. The reactor was a stainless steel flow reactor with a outer diameter of 1.27 cm, and the reaction temperature was 550 ℃, the reaction pressure was 4 MPa, and the flow rate was 12 ml per minute. As a result of the catalytic decomposition reaction using a catalyst coated with HZSM-5 on the metal foam, the heat sink was 2887 kJ/kg as a maximum, the gas phase conversion rate was 34%, and the amount of coke produced on the metal foam decreased by about 56% as the catalyst was coated compared to the uncoated catalyst.

• Korean Journal of Agricultural Science
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• v.17 no.1
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• pp.45-51
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• 1990

This study was conducted to obtain basic data for the design of cooling system by the test of engine performance of the power tiller being used widely in the rural area. Among the various factors affecting engine performance, the flow rate of cooling water was considered as the major factor in this study. Motoring loss, output, fuel consumption ratio, torque, heat absorption of cooling water, and thermal efficiency were measured and analyzed based on three flow rates of cooling water such as 15, 20, and $25{\ell}/min$. The results obtained were as follows : 1. Motoring loss of the engine was 1.371 kW at 2,200 rpm., and mechanical efficiency was 79.1% at rated output level. 2. Output power of the engine increased with the flow rate of cooling water increased. 3. BSFC was 282.9g/kW-h at the flow rate of $20{\ell}/min$, and the temperature of cooling water at outlet was $80.9^{\circ}C$. 4. There was a little variation of torque of the engine depending on the flow rate of cooling water. 5. Absorption of heat by cooling water was increased with the increase of flow rate. 6. The highest thermal efficiency of 32.3% at the flow rate of $20{\ell}/min$ was observed.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.4
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• pp.27-32
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• 2011

Tin nanoparticles were synthesized at room temperature by a compulsive reduction reaction using tin(II) acetate and tin(II) chloride precursors. When an identical amount (0.015 g) of polyvinyl pyrrolidone (PVP) was added, it was concluded that the probability of abnormally big particles forming increased with an increase in PVP molecular weight, resulting in the wide distribution of Sn nanoparticles. Differential scanning calorimetry measurements were carried out using diethylene glycol solution containing synthesized tin nanoparticles. When the population of specific particles with sizes below 35 nm was adequate, the melting point depression peaks of tin nanoparticles corresponding to the specific size were observed besides an evaporation endothermic peak of DEG during the first heating. Because DEG was evaporated and tin nanoparticles in contact became molten and coarsened during the first heating, a melting peak of bulk tin was only observed at $232^{\circ}C$ during the second heating.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.122-125
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• 1973

A study on the endothermic peak of transformation of the pyrolusite was made by using differential thermal curves for analytical reproducibility, and it was done in quantity on range from 50 mg to 450 mg of pyrolusite species. The separation of ${\alpha}-MnO_2$ peak was impossible due to the overlapping between $\alpha$ and pyrolusite peaks, and the pyrolusite was determined among the species, ${\gamma}-MnO_2$ and ${\delta}-MnO_2$, with an error ranging from $5{\%}$ to $10{\%}$.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.239-246
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• 2021

Characteristics of hydrodynamics and heat absorption by gas in a directly-irradiated fluidized bed particle receiver (50 mm-ID X 150 mm high) of SiC particles have been determined. Solid holdups of SiC particles show almost constant values with increasing gas velocity. Fine SiC particles (SiC II; dp=52 ㎛, ρs=2992 kg/㎥) showed low values of relative standard deviation of pressure drop across bed but high solids holdups in the freeboard region compared to coarse SiC particles (SiC I; dp=123 ㎛, ρs=3015 kg/㎥). The SiC II exhibited higher values of temperature difference normalized by irradiance due to the effect of additional solar heat absorption and heat transfer to the gas by the particles entrained in the freeboard region in addition to the efficient thermal diffusion of the solar heat received at bed surface. Heat absorption rate and efficiency increased with increasing the gas velocity and fluidization number. The SiC II showed maximum heat absorption rate of 17.8 W and thermal efficiency of 14.8%, which are about 33% higher than those of SiC I within the experimental gas velocity range.

• Journal of Sericultural and Entomological Science
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• v.45 no.1
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• pp.58-65
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• 2003

This study was carried out to investigate the characteristics of the soluble sericins after degumming and after hydrolysis of insoluble sericin with various enzymes. Physical and chemical characteristics of the soluble sericins were also studied and pack test was conducted. Electro donating ability of the various sericins became higher as high＞low＞KP＞PP＞PA. In FT-IR analysis, the band of insoluble sericin at 3,285cm$\^$-1/ was shifted to the lower wavelengths in soluble sericins. The intensity of the amide II band was reduced and shifted to lower wavelengths as a result of hydrolysis. In DSC analysis, all sericins showed endothermic peaks around 200$^{\circ}C$ and insoluble sericin showed another peak at 250$^{\circ}C$. The endothermic peak of the insoluble sericin was found at higher temperature compared with those of the soluble sericins which showed at 300$^{\circ}C$. Whiteness of the various sericins became higher as low＞high＞PP＞PA＞PK＞IN and yellowness were PK＞PA＞PP＞low＞high. In pack test, the skin packed with the non-woven fabric treated with the various sericins was more smooth and less oily.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.421-429
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• 2011

Experimental and theoretical studies on cooling performance of two-channel thermoelectric air-cooling system in parallel flow are conducted. The effects of operating temperature to physical properties of thermoelectric module (TEM) are experimentally examined and used in the analysis of an air-cooling system considering thermal network and energy balance. The theoretical predicted temperature variation and cooling capacity are in good agreement with measured data, thereby validating analytic model. The heat absorbed rate increases with increasing the voltage input and decreasing thermal resistance of the system. The power consumption of TEM is linearly proportional to mean temperature differences due to variations of the physical properties on operation temperature of TEM. Furthermore thermal resistance of hot side has greater effects on cooling performance than that of cold side.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.94-100
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• 2013

In this paper, Machinery analysis was conducted, in order to predict highest exposure temperatures and the analyze fire damage in the case of fire on reinforced concrete structure. After analyzing differential thermal of reference materials in accordance with temperature of concrete reference core specimen, it turned out that powerful endothermic peak came resulting from evaporation of capillary water and get water untill $200^{\circ}C$, another endothermic peak came resulting from decomposition of calcium hydroxide at $520^{\circ}C$, and then mass of reference materials remarkably decreased due to endothermic reaction. Another powerful endothermic reaction came after decomposition of calcite at $720^{\circ}C$. After analyzing X-ray diffraction of reference materials in accordance with temperature of concrete reference core specimen, it turned out that calcium hydroxide existed until the temperature of $400^{\circ}C$, but CH almost disappeared and CaO appeared from $600^{\circ}C$. The production increased in proportion to the temperature. This is because that calcium hydroxide and calcite are decomposed and CaO is produced when the temperature of concrete increases with fire. It is estimated that calcium hydroxide and calcite are utterly decomposed and peak disappears, and peak of CaO is remarkably formed instead, at the temperature of $700-800^{\circ}C$.

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.4
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• pp.499-509
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• 1999

This study was carried out to investigate the effects of wearing disposable diaper with the endothermic agent on thermoregulatory response of infant. Five healthy female infants aged about 5 months were taken as a subject of this experiment. Experimental diapers were six kinds of disposable diaper constructed of nonwoven tissue, fluff pulp, super absorbent polymer, back sheet film, leg elastic, and 0g urea(A) 1g urea(B) , 2g urea(C), 3g urea (D), 4g urea(E) 5g, urea(F) respectively. Urea(98% or over purity) was used as an endothermic agent. Experiment was proceeded while infants were sleeping at 27.5$\pm$0.5$^{\circ}C$, 50$\pm$5% R.H, 0.04m/sec. Each disposable diaper's properties was tested. During the experiment rectal temperature skin temperature of 9 areas temperature inside the disposable diapers were measured, the results were as follows : 1) There was not significant difference among the diapers in absorption capacity retention capacity and rewet(p=0.05). The absorption under load was showed to A, B,

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.1
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• pp.30-38
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• 1993

In this study, the combustion characteristics in a pre-combustion chamber diesel engine was investigated with experimental conditions of marine engine load. The heat release analysis used was a single-zone single-chamber thermodynamic analysis based on pre-combustion chamber pressure-time data. Based on the results of this investigation, the following conclusions were reached: 1) Increasing the load, peak pressure was increased and position of P sub(max) was retarded in crank angle degrees. 2) Ignition delay time was almost constant without relating to the load and the heat values to form a combusitible mixture were decreased apparently with increasing the load. 3) In premixed-combustion mode, the pattern of heat release rate was resembled without relating to the load and premixed-combustion time was shortened with increasing the load. 4) Increasing the load, mass of premixed-burned fuel was increased slightly, but was invariable beyond a certain fuel-air ratio. 5) Increasing the load, premixed-burned fraction was decreased.