• 한국주거학회논문집
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• 제16권4호
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• pp.65-71
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• 2005

The present study performed subjective evaluation experiments using slides and scale down models in order to propose guidelines for lighting environment desirable for each behavior in the house. The evaluation measure was composed of 20 mood items and 15 behavior items. As for experiment methods, the slide experiment used SD method, and the scale down model experiment used Scheffe's paired comparison. The results of this study are as follows. 1) Desirable lighting environment for working and talking is active atmosphere. 2) Lighting environment desirable far relaxation is to heighten lighting contrast using candescent lamps and local lights. In other words, active atmosphere, which is desirable for working and talking, is not desirable for relaxation. 3) Lighting for working requires bright illuminance and high color temperature(6000k). 4) Lighting for relaxation requires somewhat low brightness regardless of color temperature. If the light is bright it is better to use lamps of low color temperature. 5) for conversation, bright illuminance is more desirable than dark one, and the most adequate color temperature is 4000K.

• 한국세라믹학회지
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• 제33권4호
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• pp.379-384
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• 1996

The H2S sensing mechanism of CuO-SnO2 was confirmed by analyzing the electrical-resistance variation with temperature under an H2S atmosphere. While the resistance of CuO-SnO2 thick film at N2+H2S atmosphere was almost invariant with change in temperature it increased with increasing temperature for air +H2S atmos-phere. This behavior was analyzed using an equation derived from a basic assumption based on the H2S sensing mechanism proposed before. the experimental results are sufficiently explained with the equation derived which showed that the H2S sensing mechanism was reasonable. The equation also gave a detailed analysis and physical meaning to the behavior of the resistance variation with change in H2S concentration.

• 한국세라믹학회지
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• 제32권5호
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• pp.559-566
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• 1995

Alumina powder was coated with stearic acid and then mixed with isotactic polypropylene, atactic polypropylene as binders at 15$0^{\circ}C$ for 2 hours. The mixture was then injection molded at various mold temperatures using injection molding machine to investigate the effect of the molding temperature and debinding parameters on the formation of the defects. The molded specimens were debinded in both air and nitrogen atmospheres. Wicking and solvent methods were also used to enhance debinding efficiency. The specimens were prefired at 120$0^{\circ}C$ and then sintered at 150$0^{\circ}C$ for 3 hours. Various defects were formed at mold temoperature of 3$0^{\circ}C$, 6$0^{\circ}C$ and 10$0^{\circ}C$ and any noticeable defect was not formed at 85$^{\circ}C$. The density of green body increased with mold temperature. Debinding in air atmosphere was more effective than in nitrogen atmosphere. Results also proved that wicking and solvent treatments helped minimize the number of defects.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.97-100
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• 2001

This paper presents the characteristics of Ta-N thin-film strain gauges as high-temperature strain gauges, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4∼16 %)N$_2$). These films were annealed for 1 hour in 2x10$\^$-6/ Torr vaccum furnace range 500∼1000$^{\circ}C$. The optimized conditions of Ta-N thin-film strain gauges were annealing condition(900$^{\circ}C$, 1 hr.) in 8% N$_2$ gas flow ratio deposition atmosphere. Under optimum conditions, the Ta-N thin-films for strain gauges is obtained a high resistivity, $\rho$=768.93 ${\mu}$Ω cm, a low temperature coefficient of resistance, TCR=-84 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal gauge factor, GF=4.12.

• Advances in Energy Research
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• 제8권4호
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• pp.265-273
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• 2022

In this study, a product gas yield and carbon conversion were measured during the coal pyrolysis. The pyrolysis process occurred under two different atmospheres such as subcritical (45 bar, 10℃) and supercritical CO₂ condition (80 bar, 35℃). Under the same pressure (80 bar), the atmosphere temperature increased from 35℃ to 45℃ to further examine temperature effect on the pyrolysis at supercritical CO₂ condition. For all three cases, a power input supplied to heating wire placed below coal bed was controlled to make coal bed temperature constant. The phase change of CO₂ atmosphere and subsequent pyrolysis behaviors of coal bed were observed using high-resolution camcorder. The pressure and temperature in the reactor were controlled by a CO₂ pump and heater. Then, the coal bed was heated by wire heater to proceed the pyrolysis under supercritical CO₂ condition.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1317-1323
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• 2002

This paper describes the comparison of calculated effective stress with experimental one in austenitic heat resistant steels, STS310J1TB and STS310S with and without a small amount of Nb and N. Based on a solute atoms diffusion model, contribution from soluble nitrogen to the high-temperature strength was numerically examined for austenitic heat-resisting Fe-Cr-Ni-N(STS310J1TB) and Fe-Cr-Ni (STS310S) alloys. The solute atmosphere dragging stress of dislocation was calculated in optional dislocation velocity of STS310J1TB and STS310S at $650^{\circ}C$, $675^{\circ}C$ and $700^{\circ}C$. As a result of the numerical calculation, the solute atmosphere dragging stress of STS310J1TB was about 50 times larger than that of STS310S. When the temperature became high, the maximum value of solute atmosphere dragging stress was small and the velocity of moving dislocation was fast. From the relationship between the dislocation rate and the solute atmosphere dragging stress, the relation of both was proportional and the inclination is about 1 in the level with low velocity of moving dislocation. From above results, the mechanism of dislocation movement in STS310J1TB was the solute atmosphere dragging stress. The solute atmosphere dragging stress, which was calculated from the numerical calculation was close to the effect stress in stress relaxation tests.

• Advances in aircraft and spacecraft science
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• 제7권3호
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• pp.229-249
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• 2020

This paper is the logical follow-up of four papers by the author on the subject "aerodynamics in Mars atmosphere". The aim of the papers was to evaluate the influence of two Mars atmosphere models (NASA Glenn and GRAM-2001) on aerodynamics of a capsule (Pathfinder) entering the Mars atmosphere and also to verify the feasibility of evaluating experimentally the ambient density and the ambient pressure by means of the methods by McLaughlin and Cassanto respectively, therefore to correct the values provided by the models. The study was carried out computationally by means of: i) a code integrating the equations of dynamics of an entry capsule for the computation of the trajectories, ii) two Direct Simulation Monte Carlo (DSMC) codes for the solution of the 2-D, axial-symmetric and 3-D flow fields around the capsule in the altitude interval 50-100 km. The computations verified that the entry trajectories of Pathfinder from the two models, in terms of the Mach, Reynolds and Knudsen numbers, were very different. The aim of the present paper is to continue this study, considering other aerodynamic problems and then to provide a contribution to a long series of papers on the subject "aerodynamics in Mars atmosphere". More specifically, the present paper evaluated and quantified the effects from the two models of: i) chemical reactions on aerodynamic quantities in the shock layer, ii) surface temperature, therefore of the contribution of the re-emitted molecules, on local (pressure, skin friction, etc.) and on global (drag) quantities, iii) surface recombination reactions (catalyticity) on heat flux. The results verified that the models heavily influence the flow field (as per the shock wave structure) but, apart from the surface recombination reactions, the effects of the different conditions on aerodynamics of the capsule are negligible for both models and confirmed what already found in the previous paper that, because of the higher values of density from the NASA Glenn model, the effects on aerodynamics of a entry capsule are stronger than those computed by the GRAM-2001 model.

• 한국세라믹학회지
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• 제52권6호
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• pp.435-440
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• 2015

It is a challenge from an industrial point of view to fabricate silicon nitride substrates with high thermal conductivity and good mechanical properties for power devices from high-purity Si scrap powder by means of thick film processes such as tape casting. We characterize the residual carbon and oxygen content after the binder burnout followed by nitridation as a function of the temperature in the temperature range of $300^{\circ}C-700^{\circ}C$ and the atmosphere in a green tape sample which consists of high-purity Si powder and polymer binders such as polyvinyl butyral and dioctyl phthalate. The optimum condition of binder burnout is suggested in terms of the binder removal temperature and atmosphere. If considering nitridation, the burnout of the organic binder in air compared to that in a nitrogen atmosphere could offer an advantage when fabricating reaction-bonded $Si_3N_4$ substrates for power devices to enable low carbon and oxygen contents in green tape samples.

• 한국세라믹학회지
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• 제51권1호
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• pp.25-31
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• 2014

New green phosphor is synthesized by reducing $LiAlO_2:xEu^{3+}$ phosphors in a low pressure $H_2$ atmosphere. The $LiAlO_2:xEu^{3+}$ prepared by a solid state reaction method is reported as red phosphor. The effect of the reduction treatment on the $LiAlO_2:xEu^{3+}$ on the crystalline phase change and photoluminescence (PL) property are characterized. The reduced phosphor had a broad green light spectrum centered at 524 nm. The PL intensity of the reduced phosphor increased to a maximum at the reduction temperature of $1100^{\circ}C$. The PL intensity decreased with a further increase in the reduction temperature. The crystalline phase constituting the reduced phosphor varied with the temperature. A new crystalline phase $Li_2Al_4O_7$ was observed at $1100^{\circ}C$. The origin of the green-light emission is discussed in relation to the crystalline phase change.

• 한국전기전자재료학회논문지
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• 제11권1호
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• pp.41-47
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• 1998

The (Sr$_1$-\ulcorner.Ca\ulcorner)TiO$_3$(0.05 x 0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[$^{\circ}C$] in a reducing atmosphere($N_2$gas). After being fired in a reducing atmosphere, metal oxides(CuO) was painted on the both surface of the specimens to diffuse to the grain boundary. The capacitance changes slowly and almost linearly in the temperature region of -40~+85[$^{\circ}C$]. The capacitance characteristics appears a stable value within $\pm$10[%]. According to increase of the frequency as a functional of temperature, all specimens used in this study showed the dielectric relaxation, and the relaxation frequency was above 10\ulcorner[Hz]. The capacitance is almost unchanged below about 20[V] but it decrease slowly over 20[V]. The voltage-current characteristics of specimens observed in the temperature range of 25~125[$^{\circ}C$] as the current increased appears that it is due to space charge condensed to interface between grain and grain boundary.