• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.7-14
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• 2006

A Problem of low-velocity forced convection in a channel flow with heated wall is of practical importance and widely considered in the design of devices such as heat exchangers, and electronic equipments. Therefore, there is an urgent need for improving heat transfer performance of heated wall in the channel. In the present study, an oscillating vortex generator method is proposed to enhance the heat transfer in a channel. In this method, a rectangular bars are set in the upstream of heated region of the channel. The bars are forced to oscillate normal to the inflow, and then actively and largely generates transverse vortices behind the bars. As a result, this apparatus can enhance the heat transfer rates remarkably. Because of the interaction between the flow and oscillating bars, the variations of the flow and thermal fields become time-dependent state.

• Fire Science and Engineering
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• v.26 no.2
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• pp.1-10
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• 2012

While a performance based sprinkler design method has been widely used in UK and USA according to fire hazards of occupancies, Korean fire safety industry could not yet accept it due to nonstandardization on risk level of various occupancy. Even only two or three spray pattern sprinkler was produced in Korea fire safety industry, therefore, various spray pattern sprinklers have not yet introduced to major occupancies. Spray pattern sprinklers with one of two K value have been used in all occupancies in Korea Market. UK and USA's Fire industry should produced the spray sprinklers with various K-factors and protection area due to performance based sprinkler design requirement. Therefore the fire load density for main occupancies has been investigated in order to compare with installation standard in advanced countries. Eventually a lot of variations in orifice and K factors of standard heads were set up including special heads needed for high hazard areas such as large drop type, enlarged orifice type and early suppression fast response.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.76-81
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• 2013

In our former study, we proposed that the AC-Model might be applied to various conditions. And we also introduced the method for daylighting that it was possible to reduce discomfort glare and to improve visual impressions as the supplementary type and blind-control type on the compound lighting. The purpose of this study was to examine the relationship between physical elements and psychological evaluation of lighting space. The study was made using an full-size space, which were equipped with various luminaries. We investigated the relationship between subjective evaluation and characteristics of light distribution and showed the high correlation between the evaluation rating and luminance distribution over whole room.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.140-145
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• 2012

The purpose of this study is to understand the change of impression by comparing the uniformity lighting with the compound lighting. In previous study, we proposed a light controlling method to harmonize daylight from a window and artificial lights from a ceiling and obtained the results to support our method. We referred this method as the Adjusted Compound-Lighting Model (AC Model). The model claims that lighting in a room with a side-window are perceived as harmonious when the overall light distribution in the room is well approximated by a compound of lights from the window and the entire ceiling. The experiment is carried out with the scaled-models and mock-up spaces that were supposed to be an office space. One is lit by the uniform lighting and the other by the compound lighting in each experimental space. In order to present varying illuminance distributions, thetwo variables were used in this study. One was the ratio of thelight from the window and ceiling in the standard and evaluation box. The standard box was provided by the ratio of 20% to 40% from the window and 80% to 60% from the ceiling as two lighting ratio patterns [Wu20(=Cu80) and Wu40(=Cu60)]. And the evaluation box was provided by the light ratio of 0% to 40 from the window and 100% to 60% from the ceiling [Wcp0(=Ccp100), Wcp20(=Ccp80) and Wcp40(=Ccp60)]. The other variable was themean illuminance level in both boxes. Two level of mean illuminance (700lx and 300lx) were used in this experiment. Each lighting condition was established at equal horizontal mean illuminance level, held constant near 700lx or 300lx in both boxes. Both of them were similar in the shape of distribution when there were same ratios of lights from the window and the ceiling. Subjects were asked to evaluate the point of difference by semantic differential rating on their overall impression after comparing with two rooms. The results showed that the impressions of compound lighting were more positive score than that of uniformity lighting on the items of 'dim-bright', 'dislike-like', 'artificial-natural' and 'closed-open', and that there was no significant difference in impressions between two spaces on other items.

• Journal of the Korean Solar Energy Society
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• v.33 no.3
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• pp.99-106
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• 2013

Recently, high-thermal-conductivity graphene and carbon nanotube nanoparticles have attracted particularly close attention from researchers. In the present study, the thermal conductivity and viscosity properties of two kinds of graphene and carbon nanotube nanofluids added to distilled water - two graphenes and carbon nanotubes of differing size - were compared and analyzed. The thermal conductivities of the nanofluids, formulated in the usual manner by adding graphene and carbon nanotube to distilled water and subjecting the mixture to ultrasonic dispersion, were measured by the transient hot-wire method, and the viscosities were determined using a rotational digital viscometer. As a result, we concluded that the nanofluid of small particle diameter of graphene have outstanding properties as heat transfer media, due to their excellent thermal conductivity and viscosity, compared with the other nanofluid.

• Journal of the Korean Society of Costume
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• v.53 no.4
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• pp.131-148
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• 2003

Mural Painting of Koguryo Dynasty. root of Korean traditional pattern. has 5 types of pattern in its 24tombs: Fire pattern. Sun . Moon pattern, Flying angel pattern. Hill.Tree pattern, Holy animal bird Pattern. These patterns had developed specially in 3 regions that are Hwanghae-region, Pyongan-region, Jipan-region. from 4th-7th Century. A lot of fire pattern has found at Pyongan-region in 5th century. The ceiling right above 'Dori' frequently had the pattern. The pattern is organized in 'Kyoho' method. The sun.moon pattern was shown in Pyongan-region in 5th century. '3-leg bird'. representative of sun, and frog, representative of moon. were drawn in the pattern in 6th century, rabbit was added with frog in the pattern. Flying angel pattern had found most in Jipan region in 5th century. The pattern was not found in 4th century. Two types of the pattern are angels playing $$\mu$ical instruments and angels preying. The hill tree pattern was simple, antique, and immature in the beginning. the pattern had developed with real description as a landscape picture after the beginning. this pattern has been categorized as a landscape painting. Holy animal and bird patternn had placed in supporting rock between ceiling and floor with the mean of protection in after life These pattern, which were previously influenced by Chines culture, were developed with a base of Koguryo own tradition and supported establishment of a characterized Koguryo Cloture. This study will be a basic document for modern fashion industry of 21 century.

• Journal of Korean Society of Rural Planning
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• v.21 no.4
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• pp.157-165
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• 2015

The purpose of this study is on identifying charactreistics and management direction of complementary pond of Dalmaji village in Gangjin. Accordingly, this village was indicated as Experience and Resort village by Korean government. This study describes the construction background and characteristics and identifies species diversity and characteristics through field survey. For this, literature and field survey was performed. In field survey, vegetational survey was performed in Aug. of 2015. D(Dominant degree) and S(Sociability degree) was measured by Brown-Blanquet's method. The answer was searched from Myungsanron(明山論), a textbook of Fengsui(風水) in Joseon dynasty. Of these causes, it was considered that the representative one is a protection of fire and infectious disease because the Wolgak mountain is a fire mountain(火山) as a stone mountain in Fengsui. The results demonstrate decline of aquatic ecosystem because of neglect management. The total number of species was 24. Of the species, Zelkova serrata is a natural vegetation of this complementary forest. This is nominated as Lagerstroemia indica and Camellia japonica community. Species composition demonstrate the characteristics of Korean southern region as mixed forest of evergreen trees and deciduous ones which are indigenous plants. It was considered Juniperus chinensis KaizukaVariega in central round island was planted in Japanese colonial period and it have to be removed. It was considered that name of moon pond and moon island etc. projects the mind of village ancestors which are going to reach an ideal condition of moon. And management of quantity and depth of pond water was critical for restoration of disappearing lotus from related literature. Periodic management was needed for ecological structure and function improvement because of ecological disturbance by the invasive plants like Humulus japonicus.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.63-66
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• 2007

This study investigates the fire resistance properties of high strength concrete, around 60MPa class, designed with various admixture types and fiber content. Test showed that the increase of fiber content decreased the fluidity and slightly inclined the air content of fresh concrete. However, the fiber content in concrete did not affect the compressive strength. For the addition of admixture, specimens adding the shrinkage-reducing-agent (SR) indicated the strength value at 70MPa, which is followed by incorporating silica fume (SF) at 66MPa, the combination of expansive admixture (EA) and SR at 63MPa, only EA at 59MPa, blast furnace slag (BS) at 58MPa and fly ash (FA) at 50MPa in an order. After completing the fire test, all specimens adding 0.05vol.% of polypropylene fiber exhibited protection of spatting, except for the specimens incorporating loft of SF and incorporating 20% of SF with only SR and the combination of EP and SRA, respectively. Therefore the most effective result of this study was shown in the specimens incorporating love of FA and 30% of BS and incorporating 20% of SF with 5 % of EA. It is expected that this test results will be crucial references in near future to develope the spatting resistance method of high strength concrete.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.76-80
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• 2020

Background: To improve the measurement accuracy of liquid-scintillation counting for activity standardization, it is necessary to significantly reduce the background caused by thermal noise or after-pulses. We have therefore improved a movable 3 photomultiplier (3PM)-γ coincidence-counting method using the logical sum of three double coincidences for β events. Materials and Methods: We designed a new data-acquisition system in which β events are obtained by counting the logical sum of three double coincidences. The change in β-detection efficiency can be derived by moving three photomultiplier tubes sequentially from the liquid-scintillation vial. The validity of the method was investigated by activity measurement of ¹³⁴Cs calibrated at the Korea Research Institute of Standards and Science (KRISS) with 4π(PC)β-γ(NaI(Tl)) coincidence counting using a proportional counter (PC) for the β detector. Results and Discussion: Measurements were taken over 14 counting intervals for each liquidscintillation sample by displacing three photomultiplier tubes up to 45 mm from the sample. The dead time in each β- and γ-counting channel was adjusted to be a non-extending type of 20 ㎲. The background ranged about 1.2-3.3 s^-1, such that the contributions of thermal noise or after-pulses were negligible. As the β-detection unit was moved away from the sample, the β-detection efficiencies varied between 0.54 and 0.81. The result obtained by the method at the reference date was 396.3 ± 1.7 kBq/g. This is consistent with the KRISS-certified value of 396.0 ± 2.0 kBq/g within the uncertainty range. Conclusion: The movable 3PM-γ method developed in the present work not only succeeded in reducing background counts to negligible levels but enabled β-detection efficiency to be varied by a geometrical method to apply the efficiency extrapolation method. Compared with our earlier work shown in the study of Hwang et al. [2], the measurement accuracy has much improved. Consequently, the method developed in this study is an improved method suitable for activity standardization of β-γ emitters.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.1
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• pp.7-15
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• 2018

The submarine is an underwater weapon system which covertly attacks the enemy. Pressure hull of a submarine is a main system which has to have a capacity which can improve the survivability (e.g., protection of crews) from the high pressure and air pollution by a leakage of water, a fire caused by outside shock, explosion, and/or operational errors. In addition, pressure hull should keep the functional performance under the harsh environment. In this study, optimal design of submarine pressure hull is dealt with 7 case studies done by analytic method and then each result's adequacy is verified by numerical method such as Finite Element Analysis (FEA). For the structural analysis by FEM, material non-linearity and geometric non-linearity are considered. After FEA, the results by analytic method and numerical method are compared. Weight optimized pressure hull initial scantling methods are suggested such as a ratio with shell thickness, flange width, web height and/or relations with radius, yield strength and design pressure (DP). The suggested initial scantling formulae can reduce the pressure hull weight from 6% and 19%.