• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.113-117
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• 2003

In this study is investigated the various properties of concrete with the kinds of stabilizing agent of recycling water and solid content in order to suggest a practical use of recycling water According to the results. fluidity and air content varies slightly with the kinds of stabilizing agent and solid content, but does not make a big difference. Setting time does not differ remarkably from plain concrete at 2$0^{\circ}C$, but is shortened with an increase of solid content. Bleeding is reduced more largely in the case of S than in the case of R, and is not influenced by solid content. Compressive strength is equal or decreases in comparison with plain concrete at solid content of 1 and 5%, and shows the highest value at solid content of 3%. Length change by drying shrinkage is larger than plain concrete at solid content of 5%, and decreases at solid content of 1 and 3%. Therefore, it proves that the influence of the kinds of stabilizing agent is minute, and solid content is most effective at 3%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.87-96
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• 2008

Flow condensation heat transfer coefficients(HTCs) of R123 and R245fa are measured in a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed saturation temperature of $50\;{\pm}\;0.2\;^{\circ}C$ with mass fluxes of 50, 100, $150\;kg/m^2s$ and heat flux of $7.3{\sim}7.7\;kW/m^2$. Heat transfer data are obtained in the vapor quality range of $10{\sim}90%$. Test results show that the flow condensation HTCs of R245fa are overall 7.9% higher than those of R123 at all mass fluxes. The pressure drop of R245fa is smaller than that of R123 at the same heat flux. In conclusion, R245fa is a good candidate to replace ozone depleting R123 currently used in chillers from the view point heat transfer and environmental properties.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.29-43
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• 2017

This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber volume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five different fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl alcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated and tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiber-reinforced cementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to spall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the plain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local damage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact explosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of the macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.813-816
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• 2008

This study is an experimental study on the properties and efficiency of mold-prevention mortar and the results are summarized as following. The flow, compressive stress, and the drying shrinkage ratio of mold-prevention mortar was similar with plain, so it was shown that the mold-prevention does not influence physical effect specially. However, the mold-prevention mortar which even mixed with few mold, the mold-prevention capacity greatly increased. Also, the mold-prevention capacity of 1:4 ratio mortar was better than 1:2 ratio mortar.

• Journal of the Korean Society of Costume
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• v.51 no.7
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• pp.35-47
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• 2001

This is a research about the fabrics attached to the remains of the Okjeon old tomb which was built around the early 5th century to the mid of the 6th century. Most of the remains have one kind of fabric attached to them, but there are cases where different sorts of fabrics are attached, where one kind is attached in layers, and there are also cases where the layer is made of different types of fabrics. Although they are made of warps and wefts with no twists, there can be an S twist on the weft or on both the warp and weft, and only one Z twist can be seen. There are 81 fabrics of plain weaved, one of transformed plain weaved and five 4-end complex gauze in these remains. The sparsest plain weaved fabric has the density of 7.4 strands/cm, while the most dense fabric has the density of 148.2$\times$129.1 strands/cm and 0.046$\times$0.061/mm thickness in thread. All the fabrics observed by SEM are hemp except one silk.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.168-173
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• 2004

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decrease in 50-70% of the plain fatigue strength. This may be observed in aircraft, automobile and nuclear power plant used in special environment and various loading conditions. In the present study, the characteristics of the fretting fatigue are investigated using the two aluminum alloy(Al2024-T3511 and Al7050-T7451). Through the experiment, it is found that the fretting fatigue strength of the Al7050-T7451 alloy decreased about 50% from the plain fatigue strength, while the fretting fatigue strength of the Al2024-T3511 alloy decreased about 45%. The tire track was widely observed in fracture surface area of oblique crack which was induced by contact pressure. These results can be the basic data to the structural integrity evaluation of aluminum alloy subjected to fretting damage.

• Phonetics and Speech Sciences
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• v.7 no.3
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• pp.37-44
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• 2015

This study investigated the effects of the age of Korean speakers, place of articulation, and phonation types on voice onset time (VOT) of stops. Twenty-five preschoolers, 25 schoolers, and 25 adults who had no history of speech and language impairment produced plosives in /VCV/ words in isolation. A three-way ($3{\times}3{\times}3$) mixed design was used with the age of speakers (preschoolers, schoolers, adults) as a between-subject factor, the place of articulation (bilabials, alveolars, velars) and phonation types (plain, tense, aspirated consonants) as a within-subject factor. The dependent measure was the VOT values. Results revealed that three main effects were statistically significant. Preschoolers exhibited longer VOTs than adults (p<.05). There were significant differences in VOTs among the place of articulation, showing that speakers had the longest VOTs for velars (velars > alvelars > bilabials) (all p<.05). In addition, the VOTs for aspirated consonants were longer than those for plain and tense consonants, and the differences were significant among three phonation types (aspirated > tense > plain) (all p<.05). The current results suggested that VOTs would be linked to age and development, and schoolers over the age of 11 years had achieved adult-like VOTs. Moreover, the place of articulation and phonation types in Korean stops showed marked factors in normal speakers' VOT patterns.

• Journal of Fisheries and Marine Sciences Education
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• v.4 no.1
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• pp.47-61
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• 1992

An experimental study was carried out to investigate the condensation performance for the horizontal cylindrical heat transfer tube with various fin attached using R-11 vapor. The heat transfer tube used in this study was supplied by SUNG HYUNG METAL CO., LTD. Four different types of heat transfer tubes (plain tube, SH-CYR tube, thermocor tube and thermoexcel tube) were used. Each tube was surrounded by circular acrylate tube, and R-11 gas heated by boiler flows into the acrylate tube. Cooling water counter-flows in heat transfer tubes. Heat transfer coefficient of the plain tube from measured data was compared with those of three other tubes. The results are summarized as follows: 1. As the cooling water temperature decreased, the liquid film of R-11 turned to droplet drop on the top surface of the horizontal tube. 2. Heat transfer coefficient calculated theoretically was higher than that obtained from the experimental data. 3. As far as the condensation concerns the thermocor tube is the highest, the SH-CYR tube is the second, and the thermoexcel tube is the third excluding the plain tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.2
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• pp.149-155
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• 2007

The row-by-row heat transfer characteristics of fin-and-tube heat exchangers were experimentally investigated. Three wavy fin samples having different rows (one, two and three) and one plain fin sample (three row) were tested for $600{\leq}Re_{D}{\leq}4,000$. The heat transfer data were obtained for individual rows, and the corresponding heat transfer coefficients were reduced from the data. Results showed that the heat transfer coefficients were strongly dependent on the tube row. The heat transfer coefficient decreased as the tube row increased. However, the row effect was different depending on the fin shape. For the wavy fin, the row effect significantly decreased as the Reynolds number increased, yielding approximately the same heat transfer coefficients at $Re_{D}{\approx}2,500$. For the plain fin, however, the row effect lasted for the whole Reynolds number range. The increased mixing of bulk flow by wavy channels appears to induce high heat transfer coefficient (accordingly diminishing row effect) at downstream rows. The heat transfer coefficients of individual rows were higher for heat exchangers having larger tube rows.

• Journal of the Speleological Society of Korea
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• no.68
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• pp.75-98
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• 2005

Korea physiographic province is divided into two provinces which is northern Chugaryung graben zone and southern Chugraryung graben zone. Northern Chugraryung is also divided in to Gema block and Kohan block, and southern Chugraryung dividedinto Han block, Yongnam basin and Honam plain. The above mentioned macro geomorophic units is divided, mainly on the geotectonics. The meso geomorphic units is divided, based upon the regional distribution of topographic characteristic that is plateaus, mountains, mountain range, basins and great plain etc. Micro geomorphic units id into a mountain, a hill, a plain, and a lowland, and then it is formed by selfreliant topographic unit. And micro topographic (fan, peneplain, delta, etc) dealt with a characteristics unit. In this article has a disregarded amallest scale that is included flood plait natural levee, back marsh and oxbow lake etc. Accordingly, it shows macro units are meso units are 5, meso units are 53, micro units are 299. A study method of physiographic provincs prefered to aufsteigende and abstergands methoy. How to organically combine topographic factors can be seen in regional distribution of the peculiar topographic characteristics, for charage teristic of topographic makes a study on the topographic of micro unit such understanding as aufsteigende method. At the same time, since it can be studied systematically from marco unit to micro unit like the absteigende methods, I used both methods. And this establishment of physiographic province based on the scientific method depend on the base map of climate classification. Geology, Soil, Biology. I feel confident that it will be used the basic map for land use map, land classification map, study of geomorphology of Korea. And will be used for study of a topographic standard data.