• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.211-218
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• 2022

Coal ash is being considered as a source of silica and alumina for cement clinker. The purpose of this study was to investigate the effect on cement clinker sintering by confirming the high-temperature microstructural change according to the firing temperature in the cement clinker sintering process of coal ash. In the coal ash used as a raw material for cement clinker, the shape change of the particle surface was confirmed from the sintering tem perature of 950 ℃. The shape of the coal ash disappeared from the sintering temperature higher than 1250 ℃. It was confirmed that the Al and Fe components of the coal ash were converted to the cement interstitial phase at a temperature higher than 1350 ℃. In addition, the clinker using a large amount of coal ash as a raw material showed a low content of Lime and a high content of Belite in the sintering tem perature range of 1150~1200 ℃. From this, it was confirmed that the formation of calcium silicate mineral proceeds more easily at the initial sintering temperature by the application of coal ash.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1930-1938
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• 1994

In this paper, the effects of temperature change on the impact of CFRP laminates was experimentally studied. Composite laminates used for this experiment are CFRP orthotropic laminated plates, which have two-interfaces$[0_6^{\circ}/90_7^{\circ}]_s$ and four-interfaces$[0_3^{\circ}/90_6^{\circ}/0_3^{\circ}]_s$. The interrelations between the impact energy vs. delamination area, the impact energy vs. residual bending strength, and the interlayer delamination area vs. the decrease of the residual flexural strength of carbon fiber epoxy composite laminates subjected to FOD(Foreign Object Damage) under high temperatures were experimentally observed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.3
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• pp.1-6
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• 2001

An analytical thermal model of HESG(higt efficiency speed grinding) is presented, in which the heat flux to workpiece in grinding zone is modeled as time dependent and moves along a slope decided by contact chord(approximation of con-tact arc). By matching the maximum surface temperature of workpiece derived from this model to the maximum surface temperature of grinding wheel composite as done in Lavins simple thermal model, the relation of maximum surface tem-perature and energy partition of workpiece to grinding speed is obtained. In high speed grinding, as wheel speed increases, energy partition decreases with no regard to table speed.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.378-384
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• 1998

We investigated the possibility of systemizing data for the colour gradation of classical ceramics by build-ing program and D-basing each data information in pottery field that has been fall behind in forming data be-cause of many variable and lacking of data system. In this study we manufactured $CoAl_2O_4$ stain that has stable spinel structure at high temperature and then mixed base glaze with stain for the additive per-centage of 0.5 , 1, 5, 10, 15 wt% In thie colouring of Lime base glaze with the wide ranged melting tem-perature the colour development of cobalt-blue sintered at $1250^{\circ}C$ is better than that of $1150^{\circ}C$ $1350^{\circ}C$ The experimental conditions and data are D-based simulated programming of computer. The result of -based data appeared to be more smoothed fusion-adherence in the Matt glaze range of Lime base glaze, The variation of colouring is not found when additive content of glaze is more than 5 wt% and the stable colour development of stain was shown at the content that RO, $R_2O$ percentage is high (the content that R2O3 per-centage is low)

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.440-446
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• 1999

This study is mainly concerned with the friction and wear properties for the specimens of crank shaft which are made of ductile cast iron. The friction and wear tests were carried out for the nor-malized ductile cast iron specimens and their properties were compared with each other at reheat-ing temperatures(550^{\circC,\; 600^{\circ}C,\; 650^{\circ}$) and in dry condition at different friction velocity(0.94 m/s 1.88m/s 2.83m/s) range. After austenized at $910^{\circ}C$ it is observed that the higher the reheating temperature is the hardness becomes decrease which is supposedly attributed to the fact that the amount of pearlite austenite matrix is rduced by reheating after normalizing and that as the reheating temperature goes up the pearlite generated is less and the interval between the pearlites were widened at last to make pearlite globular. At the low velocity the friction coefficient increase in the beginning and gets stabilized as the sliding distance increases. As the friction velocity grows the friction coefficient decreases suppos-edly since the abrasive wear is heavier at low velocity than at the high velocity as the friction tem-perature at low velocity is lower than at high velocity.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.3
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• pp.117-128
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• 2002

This paper describes the smoke filling process of a fire field model based on a self-deve-loped SMEP (Smoke Movement Estimating Program) code to the simulation of fire induced flows in the two types of atrium space containing a ceiling heat flux. The SMEP using PISO algorithm solves conservation equations for mass, momentum, energy and species, together with those for the modified k-$\varepsilon$ turbulence model with buoyancy production term. Also it solves the radiation equation using the discrete ordinates method. Compressibility is assumed and the perfect gas law is used. Comparison of the calculated upper-layer average tempera-ture and smoke layer clear height with the zone models has shown reasonable agreement. The zone models used are the CFAST and the NBTC one-room. For atrium fires with ceiling glass the ceiling heat flux by solar heat causes a high smoke temperature near the ceiling. However, it has no effect on the smoke movement such as the smoke layer clear heights that are important in fire safety. In conclusion, the smoke layer clear heights that are important in evacuation activity except the early of a fire were not as sensitive as the smoke layer tem-perature to the nature of ceiling heat flux condition. Thus, a fire sensor in atrium with ceiling glass has to consider these phenomena.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.351-353
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• 2003

We present a retrieval scheme for the remote sensing of evapotranspiration (ET) over rice paddy. To perform the retrieval, high-resolution airborne imagery of multi-spectral visible and thermal infrared data, and ground-based meteorological measurements are utilized. Our ET retrieval scheme is based on the basic principal of surface energy budget, which is a result of balance in longwave and shortwave radiation, latent heat, sensible heat, and energy flux into the ground. To partition the latent and sensible heat fluxes of interest from the energy balance equation, three basic parameters are of most concern, including albedo, surface temperature, and normalized difference vegetation index (NDVI). The NDVI and albedo can be easily derived from the visible and near infrared spectral data, while the surface tem-perature can be determined through the analysis of the infrared data with the Stefan Boltzmann law. From the airborne imagery taken on 28 April 2003, we observe very good dry and wet pixels that can be easily corre-sponded to the radiation and evaporation controlled crite-ria, respectively, and, hence, for the further use in defin-ing the evaporative fraction needed to partition sensible and latent heat fluxes from the net energy flux. The de-rived ET is compared with the in situ measurements.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.123-130
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• 1997

In this study, (Sr.Pb.Ca)TiO3-Bi2O3.3TiO2(SPCT) systems were investigated to develop a new material which has a high dielectric constant, a low dielectric loss and a small TCC(Temperature Coefficient of Capa-citance), and are suitable for high voltage applications as a function of the additions of Bi2O3.3TiO2 from 5 mol.% to 9 mol.%. The result obtained from our investigation showed that up to 6 mol.% Bi2O3.3TiO ad-dition the dielectric constant increased and it deteriorated at higher concentrations with increasing amount of the acicular grains. As a result of some dopants (SiO2, Nb2O3, MnO2) addition to SPCT, the specimens with MnO2 showed good dielectric properties. The dielectric constant decreased, but the TCC was improved with the addition of MnO2 from 0.15 wt.% to 0.45 wt. %.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.703-714
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• 2007

The aim of this research is to evaluate the fire resistance of concrete-filled steel square tube columns (square CFT columns) under constant axial loads by numerical analysis. The authors examined the experimental results on the fire resistance of concrete-filled steel square tube columns without fire protection. As the materials of CFT columns, steel of SPSR 400 grade and concrete of 27.5MPa and 37.8MPa strengths were used. The significant parameters were determined, such as load ratio, cross-sectional dimensions, and concrete strength. Detailed analytical simulations of fire resistance and axial deformation showed good agreement with the experimental observations. Therefore, this numerical analysis exhibited a reasonable estimation of fire resistance of the square CFT column. Results of the numerical parametric studies showed that the fire resistance of the CFT columns increased with the decrease of the concrete strength and the increase of the cross-sectional dimensions about the constant axial load ratio ($N/N_c$).

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.195-201
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• 1997

The present paper describes the effect of dry mixed grinding on kaolinite-aluminum trihydroxide mixture with a planetary ball mill before sintering and its influence on mullite formation during sintering. The size reduction of the mixture is market in the early stage of grinding and the obtained fine particles agglomerate subsequently with an increase of grinding time. The crystal structure of the mixture is collapsed easily into an amorphous one by planetary ball milling, of which amount increases with an increase of grinding time. Only mullite phase except for anatase as an inherent impurity in kaolinite appeared in the sintered body of the mixtures with mixed grinding as relatively lower temperature 1523K, while corundum, cristobalite, and Al-Si spinel phases, besides mullite were formed in the sintered body of the mixture without mixed grinding. Therefore, the mixed grinding treatment is very effective to improve the homogeneous mixing and disp-ersion of the mixture of raw materials on a micro scale and to decrease the thermal decomposition tem-perature by crystal structure change of them so as to obatin direct preparation of mullite with high purity at relatively low temperature.