• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.192-202
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• 1996

In Li0.4Ca0.05AlP0.5Si0.75O4.5 composition glass, glass-ceramic having a near 100% crystallinity after nucleation heat treatment of 74$0^{\circ}C$/2 h and crystallization heat treatment of 90$0^{\circ}C$/2 h and in-situ TiO2 whisker reinforced glass-ceramic after heat treatment of 105$0^{\circ}C$ for 20 h were fabricated with the addition of 4% TiO2 as a nucleating agent. With these materials a ball-on-disc type wear test was conducted in order to examine the effect of TiO2 whisker prepcipitation on ambient and high temperature wear properties of the glass-ceramic. Wear test results indicated that all specimens exhibited micro-fracture wear mechanism in ambient temperature. As temperature increased the wear rates of the materials were increased. However the in-situ TiO2 whisker reinforced glass-ceramic exhibited the lowest wear rate over the test temperature range. This resulted from the improvement of harness and fracture toughness of the material as the glass converted into the glass-ceramic followed by precipitation of TiO2 whiskers throughout the glass-ceramic matrix.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.517-522
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• 2005

A cold storage refrigerator using phase change material(PCM) has been developed and its performance test results are provided here. The inner temperature of the refrigerator is controlled with forced convection driven by a fan using a DC battery. At the first, to freeze all the PCM of the ambient temperature by a built-in refrigerating machine, it took about 8 and 10 hours respectively at the refrigerator and the freezer mode. Then, without external power supply, the inner temperature of the cold storage refrigerator has been maintained at $-18{\pm}1^{\circ}C$ during 14 hours at the freezer mode and maintained at $3{\pm}^{\circ}C$ during 34 hours at the refrigerator mode. Just after the end of its valid usage as a refrigerator or a freezer, it took about 6 hours to refreeze the PCM for its reuse. During the test, the ambient temperature was kept at $30^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.333-342
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• 1999

This research was performed to investigate how the basic glaze change affected colour development at high temperature with a stable colorant (spinel structure CoAl2O4 pigment) The compounded pigment which is widely used for porcelain was also tested for the basic glazes adaptability. The data from the test were recorded in a computer data-base program. Therefore could be easily used in the study related with a pottery field. CoO : Al2O3 system spinel pigment of barium glaze lime glaze zinc glaze lead glaze and talc glaze were chosen for this study. The colors of Cobalt blue bright blue, blue purple were seen at the wave lengths of 455-480nm at the firing temperature of 1250$^{\circ}C$. Stable color were obtained from lime glaze bar-ium glaze zinc glaze. All the information in the database were used to examine all the possible result of the test in the study of porcelain. When the test results database were examined in all temperature ranges the lack of adhesion with the pigment occurred at the temperature of 1150$^{\circ}C$. The lack of adhesion is seen due to vaporization of the lead glaze.

• Nuclear Engineering and Technology
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• v.37 no.6
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• pp.537-556
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• 2005

A primary-pipe rupture accident is one of the design-basis accidents of a High-Temperature Gas-cooled Reactor (HTGR). When the primary-pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. This paper describes an experiment and analysis of the air ingress phenomena and the method fur the prevention of air ingress into the reactor during the primary-pipe rupture accident. The numerical results are in good agreement with the experimental ones regarding the density of the gas mixture, the concentration of each gas species produced by the graphite oxidation reaction and the onset time of the natural circulation of air. A hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR) Is being designed to be able to produce hydrogen by themo-chemical iodine-Sulfur process, using a nuclear heat of 10 MW supplied by the HTTR. The HTTR hydrogen production system is first connected to a nuclear reactor in the world; hence a permeation test of hydrogen isotopes through heat exchanger is carried out to obtain detailed data for safety review and development of analytical codes. This paper also describes an overview of the hydrogen permeation test and permeability of hydrogen and deuterium of Hastelloy XR.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.53-59
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• 1996

To protect the damages or the disasters caused by overheating of industrial electric equipments or electric home appliances, a temperature sensitive thermal fuse is generally used in those equipments. Thermal fuses cutoff the current flow when the temperature of the electric equipments are abnormally overheated and over the certain temperature. Therefore thermal fuse is one of the most important elements in the sense of safety. Thermal fuses are classified into two types according to thermally sensitive materials, a low temperature melting alloy and an organic chemical compound. Domestic products of thermal fuses are now only with an organic chemical compound. Domestic products tested by using cutoff test and aging test etc. are satisfied UL specification. It's shown that the accuracy and the precision of the domestic products are as good as those of the overseas products obtained UL mark. However, some of domestic products show the reclosing problem which is mainly related the safety. This problem should be solved to make the reliable thermal fuses. In this paper, our Interest is to find out the causes of reclosing. In the comparison between thermally sensitive materials occurred reclosing and those occurred no reclosing, the test effects show that the characteristics of emitting heat and absorbing heat are different.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.916-919
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• 2003

In this paper, we deal with a development of measurement system to apply the leakage rates test of primary containment in nuclear power plant. The measurement test about leakage rates in primary containment is one sort of test to prove safety of nuclear power plant. The parameters which are measured to calculate leakage rates are drybulb temperature, dew point temperature(or relative humidity), absolute pressure and flow. Overall, the measurement system consists of sensor module for data acquisition of the parameters, transfer module for wireless data communication and control module to control system and to calculate leakage rates. Because existing measurement systems are difficult to set in field, we pursued convenience of use, we applied wireless data communication and individual form module using battery. We also changed for the better in confidence. Recently, we are developing a drybulb temperature and a dew point temperature sensor module. We describe about function of developed measurement system, its standard and an plan for verification of measurement system.

• Journal of Welding and Joining
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• v.7 no.4
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• pp.30-37
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• 1989

Effect of heat treatment on mechanical properties of an overlay weldment was investigated. Over welding was carried out on the structural C-Mn mild steel substrate to take required test specimens. Shielded metal arc welding process with 13Cr-0.2Ni stick electrode was applied. The heat treatment temperatures and holding times were $450{\circ}C., 550{\circ}C., 650{\circ}C., 750{\circ}C., 850{\circ}C.$ and 0.5hr, 2hr, 10hr, respectively. Mechanical tests and microscopic inspection were also carried out to investigate welds soundness. Test results indicated that carbon migration was dominant near bonded zone. At temperature of around 650.deg. C, carburized layer and decarburized layer were formed remarkably along overlay welds region and C-Mn mild steel region, respectively. The wideth of these layers became wider with increasing heat treatment temperature and/or holding time at the elevated temperature, and this relationship agreed with Larson-Miller parameter. Side bending test results demonstrated that the crack free region of overlay welds could be deduced from the relationship between temperature and holding time.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.110-115
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• 2001

In this paper, a multiple comparison was proposed to minimize the amount of coolant. And new coolant level, called "low level", was suggested to show usefulness of multiple comparison for experiments. The amount of this levee is about 1/4 of conventional coolant amount-called "high level", and dry cutting is called "none level". Using these coolant levels, the cutting temperatures of each coolant level in turning process were analyzed by analysis of variance(ANOYA)-test and a multiple comparison. As the result of ANOVA-test, we have just known that the average of temperature of each coolant level is not equal. However by Tukey's HSD, one of multiple comparison. it was analyzed that the average of temperature of low level is similar to that of high levee and different from that of none level.erent from that of none level.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.235-241
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• 2005

Thermal creep properties of the advanced zirconium fuel claddings named by HANA alloys which were developed for high burn-up application were evaluated. The creep test of HANA cladding tubes was carried out by the internal pressurization method in temperature range from 350 to $400^{\circ}C$ and in the hoop stress range from 100 to 150 MPa. Creep tests were lasted up to 800 days, which showed the steady-state secondary creep rate. The creep resistance of HANA fuel claddings was affected by final annealing temperature and various factors, such as alloying element, applied stress and testing temperature. From the results the microstructure observation of the samples before and after creep test by using TEM, the dislocation density was increased in the sample of after creep test. The Sn as an alloying element was more effective in the creep resistance than other elements such as Nb, Fe, Cr and Cu due to solute hardening effect of Sn. In case of HANA fuel claddings, the improved creep resistance was obtained by the control of final heat treatment temperature as well as alloying element.

• Korean Journal of Metals and Materials
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• v.48 no.3
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• pp.210-217
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• 2010

The effects of cooling rate and onset time of fatigue test on hot ductility of plain carbon steels containing 0.06$\sim$0.8 wt.% carbon were investigated at various temperatures. The tensile tested specimen after fatigue strain during cooling showed higher hot ductility than the specimen fatigued and tensile-strained after cooling. With a decreasing cooling rate from solutionizing temperature to test temperature, hot ductility was increased in all temperature ranges, typically in the trough region, and the minimum point of ductility moved to a lower temperature. Also, the depth and width of the trough decreased with lowering the cooling rate.