• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.167-174
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• 1994

The creep behavior and creep fracture of alumina at high temperature were investigated under four point flexural test. The steady-state creep behavior was observed at low bending stress and the primary creep until fracture was observed at high bending stress. The loading history of bending stress did not affect on the steady-stated creep rate. Intergranular fracture was dominant for fracture of alumina at room and high temperature. However, transgranular fracture was dominant on creep fracture of alumina under high temperature by nuclueation and growth of microcracks due to residual flaws or cavities in the material.

• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.543-551
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• 1994

The creep behavior and creep fracture of sintered alumina at high temperature were investigated under four point flexural test. Steady-state creep behavior was observed at low bending stress and primary creep until fracture was observed at hish bending stress. The loading history of bending stress did not affect on steady-state creep rate. Intergranular fracture was dominant for fracture of alumina at room and high temperature. However, transgranular fracture was dominant on creep of alumina under high temperature by nucleation and growth of microcracks due to residual flaws or cavities in the material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1091-1092
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• 2013

• Animal Systematics, Evolution and Diversity
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• v.17 no.2
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• pp.171-177
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• 2001

The life history of Obelia bicuspidata Clarke, 1975 (Hydrozoa, Campanulariidae) was studied in its habitats, Jak-yk Island, Korea and in the laboratory It grows mainly attaching to the under sides of small rocks immersed in muddy shores, or the shade surfaces of oyster shells. The hydoids liberate medusae. The medusa buds develope twice per year, during from March to June and from September to October The optimum water temperature for the hydroids is between 4$^{\circ}C$ and 8$^{\circ}C$ and at the temperature above 9$^{\circ}C$ the hydroids begin to degenerate. In August the surface water temperature is around $25^{\circ}C$ and the hydrothecae are all disappeared. The hydroids grow best during from February to May. The medusae are small, 0.3 mm high, 0.45 mm wide and require about 9 days at room temperature (about 2$0^{\circ}C$) for mature after releasing. Obelia bicuspidata turned out to be boreal species in this work.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2104-2125
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• 2021

This paper presents the verification and validation (V&V) of a calculation module for isotope inventory prediction to control the back-end cycle of spent nuclear fuel (SNF). The calculation method presented herein was implemented in a two-step code system of a lattice code STREAM and a nodal diffusion code RAST-K. STREAM generates a cross section and provides the number density information using branch/history depletion branch calculations, whereas RAST-K supplies the power history and three history indices (boron concentration, moderator temperature, and fuel temperature). As its primary feature, this method can directly consider three-dimensional core simulation conditions using history indices of the operating conditions. Therefore, this method reduces the computation time by avoiding a recalculation of the fuel depletion. The module for isotope inventory calculates the number densities using the Lagrange interpolation method and power history correction factors, which are applied to correct the effects of the decay and fission products generated at different power levels. To assess the reliability of the developed code system for back-end cycle analysis, validation study was performed with 58 measured samples of pressurized water reactor (PWR) SNF, and code-to-code comparison was conducted with STREAM-SNF, HELIOS-1.6 and SCALE 5.1. The V&V results presented that the developed code system can provide reasonable results with comparable confidence intervals. As a result, this paper successfully demonstrates that the isotope inventory prediction code system can be used for spent nuclear fuel analysis.

• ALGAE
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• v.20 no.4
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• pp.325-331
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• 2005

Populations of Campylaephora borealis (Nakamura) Seo, Cho et Boo and C. crassa (Okamura) Nakamura show a year-around occurrence of all life-history stages. Such a concurrency of life-history stages produces problems in recognizing species in the field. Here, we invesitgated the morphological variation and life-history stages of both species using a statistical character analysis. Life-history stage was correlated with the seawater temperature in C. borealis, whereas it was dependant on biomass in C. crassa. Thalli had dichotomous branches with adaxial branchlets. The statistics showed that the seasonal change in morphology of C. borealis was significantly different from that of C. crassa in seven qualitative characters and five quantitative characters (p < 0.001), although six quantitative features including tetrasporangial size were similar in both species. The morphological difference between the two species may be due to the annual variation of branchlet number and the variance of branch subangle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.652-660
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• 2003

T-history method, measuring heat-of-fusion of phase change material (PCM) in sealed tubes, has the advantages of a simple experimental device and no requirements in sampling process. However, a degree of supercooling used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion in the original method, which has been improved in order to predict better results by us. In the present study, the modified method was applied to a variety of PCM such as paraffin and lauric acid having very small or no supercooling with a satisfactory precision. Also the selection of inflection point and temperature measurement position was fumed out not to affect the accuracy of heat-of-fusion significantly. As a result, the method can provide an appropriate means to assess a new developed PCM by cycle test even if a very accurate value cannot be obtained.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.17-20
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• 2005

This paper reported the temperature history of concrete placed at deck plate slab under cold climate condition by varying with surface insulating type. No curing sheet and simple insulation curing including non-woven fabric, double layer bubble sheet, the combination of double layer bubble sheet and non-woven fabric dropped temperature below zero within 24 hours, which caused frost damage at early age. On the other hand, the combination of double layer bubble sheet and non-woven fabric and double layer bubble sheet and styrofoam maintained minimum temperature above $4^{\circ}C\;and\;8^{\circ}C$, respectively. Based on core test results compressive strength of concrete with the combination of double layer bubble sheet and non-woven fabric and double layer bubble sheet and styrofoam was higher than those with other curing method due to good insulation effect.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.67-71
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• 2008

The study analyzed on fire resistance of high strength concrete followed by thickness of fireproof plaster board and change of adhesive method. In spalling characteristics after fire resistance test, all four-side covering concretes were left out of testing screens. Thus, serious spalling was happened by exposing their internal reinforcing rods. in partial testing screens, spalling was happened till the internal concrete of main reinforcing rod. Only, temperature history didn't have special differences among changes of adhesive method. However, thickness of fireproof plaster board is very important. Namely, mock member reinforcing 25mm general adhesive + Bending was 583℃ in the highest temperature of surface part and 479℃ in the highest temperature of the main reinforcing rod, which was relatively good temperature history.

• Tribology and Lubricants
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• v.25 no.4
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• pp.207-216
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• 2009

Friction tests were carried out in order to investigate the effects of temperature on the friction and wear behaviors between a PMMA film and a fused silica lens using a microtribometer. The friction forces on the PMMA film were measured under atmospheric condition as the temperature of the film was increased from 300 K to 443 K. The contact area between the film and the lens was observed. The tribological characteristics of the film were significantly changed as the temperature increased. The changes were discussed with the change of the film state from glassy to viscous flow. In addition, the results showed that the friction behavior can be varied with the thermal history of the PMMA film. Residual solvent in the PMMA film could emerge to the PMMA surface due to an additional heating and the solvent on the film surface decreased the friction force.