• Nuclear Engineering and Technology
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• v.16 no.1
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• pp.11-17
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• 1984

Sample calculations were done for KORI-1 to develop a better understanding of what happens after very small LOCA ($\leq$0.05 ft$^2$). For a water-side break with the break size larger than 0.006 ft$^2$, fluid-loss through break exceeds the makeup. If the break size is larger than 0.008ft$^2$, decay heat can be completely removed through break. Based on these results, it was concluded that KORI-1 is fairly safe for the whole spectrum of sizes in very small LOCA. However, for the reactor with 900 MWe or 1200 MWe, a certain spectrum of sizes in very small LOCA should be carefully considered. In the accident sequence the transition from natural circulation to pool boiling or from pool boiling to natural circulation may be troublesome to the operator or in the safety analysis. Operator's intervention was discussed; primary pump shutoff, HPI pump shutoff, break isolation, and opening relief valve. It was proved that continuous operation of HPI pumps after shutdown will not threaten the integrity of the primary system.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.191-195
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• 2000

With the object of developing a non-gap choke core, effects of annealing in oxygen atmosphere on magnetic properties for Fe$_{78}$Si$_{9}$B$_{13}$ amorphous alloy were investigated. After annealing for 2 hrs at 440 $^{\circ}C$, optimum magnetic properties for choke core were obtained, where the effective permeability was 180 and was almost constant up to several MHz, and the decrease in permeability upon large DC bias current of 12 A or DC bias magnetic field of 8,000 A/m was very little. Moreover the AC magnetic loss was very low as compared to the conventional choke cores. Upon the optimum annealing, the magnetic hysteresis loop was inclined accompanying the increase of coercive force and the appearance of fine crystallites of $\alpha$-Fe phase. The good choke core properties was considered to be due to the suppression of domain boundary motion and domain refinement by the crystallites.

• Fire Science and Engineering
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• v.24 no.4
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• pp.69-78
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• 2010

In this study, Fire Hazards were evaluated through computer simulation using FDS program for an apartment fire accident. The results of fire simulation showed that the maximum heat release rate in the case of no sprinklers activation was 7,700 kW which was about 16 times of that in the case of sprinklers activation, 497 kW and there was a very high fire hazard due to the backdraft phenomenon when the door of fire room was forced to open. Regarding the hazard time of fire room temperature and detection time of detectors, available evacuation time was 32.5 seconds of minimum to 53.5 seconds of maximum. In the case of sprinklers activation, fire hazard in the apartment was showed to be very low due to the fire control by the spray cooling of sprinklers. This study shows that what a important function for fire safety is the activations of fire sprinkler system and emergency alarm system and what a large loss can cause if these systems don’t activate in fire accidents.

• Fire Science and Engineering
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• v.21 no.4
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• pp.44-51
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• 2007

Most of the Korea temples of cultural property are wooden buildings and easy combusted. They are often located in mountain area far away from the city. It is very difficult to approach the fight area. The putting out is very difficult in the initial fire time. And for protecting the cultural property in the long-term continuous fire source there are some restrictions in water source and suppression system. In this paper the initial putting out fire due to the forest fire and the protection of cultural property in the long-term continuous fire source were researched. The improved project about fire control facilities of the Korea cultural property was proposed. In the proposed project the facilities using Water mist which can reduce more loss than existing facilities using water are applied. In view of the topographic position the method of eliminating the energy of combustibles and wall for cutting off the heat in the fire control facilities are also mentioned.

• Journal of the Mineralogical Society of Korea
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• v.11 no.2
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• pp.85-96
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• 1998

The sericite ore is formed by the hydrothermal alteration of rhyodacitic welded tuff. The alteration zone of the host rock can be classified into four types based on the mineral assemblages ; sericite, quartz-sericite, silicified and propylite zone. The sericite ore mainly occurs as vein types and fault clay along the fault plane in the quartz-sericite zone. Mineral components of the sericite ore are mainly sericite with minor diaspore, corundum and pyrite. The sericitic porcelaineous ore is mainly composed of quartz and sericite. Accessory minerals are muscovite, diaspore, sphene, corundum, pyrite, iron-oxides and etc. The chemical compositions of K2O, Al2O3, and ignition loss in the sericite ore increase largely than that of the host rock, while the compositions of SiO2, Na2O and Fe2O3 decrease. XRD patterns of the heat-treated sericite ores show the formation of mullite at $1,200^{\circ}C$. and the diaspore-bearing sericite ore forms mullite and corundum at $1,200^{\circ}C$. The differential thermal analysis of the sericite ores show small endothermic peak at 645~668$^{\circ}C$. and the diaspore-bearing sericite ore shows a strong endothermic peak at $517^{\circ}C$. It indicates that the decomposition of diaspore appear at lower temperature than that of sericite. The thermal expansivity of the sericite ores show the similar pattern. The sericite ores show the thermal expansivity of 3.3~4.7% at 900$^{\circ}C$ and 0.39~0.75% at 1,20$0^{\circ}C$, respectively. DTA-TG curves of the sericite ores show closely relations with the thermal expansivity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.117-123
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• 1987

This study was conducted to develop an automatic insulation system to reduce the heat loss through the wall of greenhouses during the nighttime in winter. A double covered model vinyl house was constructed, and blowers were used to fill or remove styrene pellets automatically the inside of the double-wall of the double covered vinyl house. The effects of insulation of the double covered vinyl house insulated with the styrene pellets were analyzed by comparing with the single covered vinyl house. The results obtained from this study can be summarized as follows : 1. The optimum thickness of the double-wall of the double covered vinyl house was found to be 5 to 10 cm. 2.When the outside temperature varied in the range of -8.3 to -1.5$^{\circ}C$ during the nighttime, the inside temperature of the double covered vinyl house insulated with the styrene pellets showed 7.7 to 11.7$^{\circ}C$ and the inside temperature of the single covered vinyl house showed -5.8 to 2.3$^{\circ}C$. Therefore, the effects of insulation of the double covered vinyl house insulated with the styrene pellets were confirmed to be excellent. 3. Also, the excessive increase of the inside temperature in the vinyl house was prevented by the shading effect of the double covered vinyl house insulated with the styrene pellets during the daytime. 4. When the outside temperature varied in the range of 17.7 to 30.0$^{\circ}C$ during the daytime, it was possible to keep the inside temperature at 30${\pm}$4$^{\circ}C$ in the double covered vinyl house by operating the insulation system. 5. The transmissivity of the double covered vinyl house with the styrene pellets removed was 52.4 % on the average.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.111-116
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• 1983

Temperature inversions are investigated by using the oceanographic data (1965-1979) obtained in the Southern Sea of Korea. The temperature inversions in winter occur about six times more frequently than those in sumner. In the west region of the Southern Sea, the inversions are found at any depth in winter. In the east region of the Southern Sea, however, they usually appear in surface layer in winter. Such inversion phenomena in winter can be explained by surface cooling effects associated with a net heat loss at the sea surface and a southward advection of surface cold water due to north-westerly monsoon. In summer the inversion layers are usually formed below the thermocline in the west region of the Southern Sea, and in surface layer in the east region. The former results from the mixing between the Tsushima Warm Current and the Yellow Sea Bottom Cold Water, and the latter is generated by an offshore flow of cold water near coast due to southwesterly wind.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.35-38
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• 2015

LEDs are considered to be an alternative for enhancement of energy efficiency, applied for numerous areas such as display, automotive headlight not only lights. Yellow phosphor is generally utilized with blue LEDs to generate WLED, $Y_3Al_{5}O_{12}:Ce^{3+}$ is typically used as the yellow phosphor. The phosphor, mixed with epoxy resin, has been used by being spread and hardened on the blue LED chip. This paste-based packaging gives rise to problems of degradation of phosphor by heat and decrease of luminous efficiency. Although phosphor plate is used instead of the epoxy-phosphor mixture to solve these problems, loss of luminous efficacy by total internal reflection inside the plate also should be solved. In this study, we coated the side of the plate with silver as one of the solution.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.159-169
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• 2010

A multiphysics model analysis including moisture transport, heat transfer and solid mechanics and experiments on the normal and light weight concrete were carried out in order to study the effect of preabsorbed water in the light weight aggregates on the drying and shrinkage characteristics of concrete. Consequently, with fixed water-cement ratio, loss of water content of normal and light weight concrete were compared and the results showed that the lightweight concrete lost less moist than the normal concrete in early age and long term which was by moist supply effect. Accordingly, shrinkage strain size and distribution of lightweight concrete were decreased, and shrinkage reducing effect was efficient in early age with water cement ratio 0.3 and in both early age, and long term with water cement ratio 0.5. The comparison of analysis results and exaperimental results indicate that characteristic values of moisture transport and the relation humidity and shrinkage strain from this study are resonable for application for other differential shrinkage analysis in lightweight concrete.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.609-615
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• 2011

A 5 kW class SOFC system for cogeneration power units was consisted of a hot box part and cold BOPs. High temperature components such as a stack, a fuel reformer, a catalytic combustor, and heat exchanges are arranged in the bot box considering their operating temperatures for the system efficiency. The hot box was made of ceramic boards for the thermal insulation. A 5 kW class SOFC stack was composed of 2 sub-modules and each module had 64 cells with $15{\times}15cm^2$ area and stainless steel interconnects. The 5 kW class SOFC system was operated with a hydrogen and a city gas. With a hydrogen, the total power of the stacks was about 7.1 kWDC and electrical efficiency was about 49.3% at 80 A. With a city gas, the total power of the stacks was about 5.7 $kW_{DC}$ and electrical efficiency was about 38.8% at 60 A. Under self-sustained operating condition, the system efficiency including a power conditioning loss and a consumed power by BOPs was about 30.2%.