• International Journal of Highway Engineering
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• v.15 no.4
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• pp.65-73
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• 2013

PURPOSES : As a research to develop a cement treated base course for an airport pavement which can enhance its drainage, this paper investigated the strength, infiltration performance and durability of the pervious concrete with respect to maximum coarse aggregate sizes and compaction methods. METHODS : This study measured compressive strength, infiltration rate, continuous porosity and freeze-thaw resistance of pervious concrete specimens, which were fabricated with five different compaction methods and different maximum aggregate sizes. In addition, in order to reduce the usage of Portland cement content and to enhance environment-friendliness, a portion of the cement was replaced with Ground Granulated Blast Furnace Slag (GGBS). RESULTS: Compressive strength requirement, 5 MPa at 7 days, was met for all applied compaction methods and aggregate sizes, except for the case of self-compaction. Infiltration rate became increased as the size of aggregate increased. The measured continuous porosities varied with the different compaction methods but the variation was not significant. When GGBS was incorporated, the strength requirement was successfully satisfied and the resistance to freezing-thawing was also superior to the required limit. CONCLUSIONS: The infiltration rate increased as the maximum size of aggregate increased but considering construct ability and supply of course aggregate, its size is recommended to be 25mm. With the suggested mix proportions, the developed pervious concrete is expected to successfully meet requirements for strength, drainage and durability for cement treated base or subbase course of an airport pavement.

• Journal of the Economic Geographical Society of Korea
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• v.17 no.4
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• pp.660-674
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• 2014

This paper analyzes the social cohesion effects of creative industrial as a core role player of emerging new economic paradigm of the creative economy using the case of Seoul Metropolitan Area(SMA) that is a typical cluster of creative industries in Korea. This study reclassified the creative industries in a Korean context into 13 industries in 6 sectors. Based on this reclassification, the study found out that the spatial pattern of creative industries in SMA is spatially much differentiated in terms of specialization, which demands more differentiated cluster strategy with different policy mix. This paper also investigates the social cohesion effects of creative industries using structural equation modelling. It turns out that the growth of creative industries is likely to contribute to the regional development capacity and also to provide positive effects on various aspects of the social cohesion.

• Journal of the Speleological Society of Korea
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• v.59
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• pp.21-36
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• 1999

Most scholars calssify caves into natural resource, but caves possess values of natural and human resource, mix up the features of natural resources and human resources. Now, caves are distributed 260 in Korea. Seongryu Cave is showed in 1967 for the first time, till 1997 12 caves is opened to tourist. But since 1996 the 12 show caves of all is not launched the safety and environment-protection check-up adduced reason for IMF. Then caves must maintain environment of the normal temperature, humidity and dark. But the environment of caves are destroyed by tourism development. Thus to maintain environment of caves, it used to consider the counterplan as follows in restraint of the environmental change. Firstly, in case of development work to open caves, it must keep up with the prototype. Secondly, it must establish a freight depositary to prevent the influence of the caves's stain and damage due to tourist's objects. Thirdly, to maintain the normal temperature and humidity, it must install artificial poultice equipment of the inner parts of caves. Fourthly, in order to prevent the occurrence of $CO_2$, it must assessment of the optimum number of the greatest stayer. Fifthly, the control of closure for a given period of time is useful of the restoration to the cave's original state. Sixthly, by means of make narrow entrance, it should not influence the outer's air on the inner parts on caves. Seventhly, to keep the temperature of the inner part of caves, the lightening should be maintained moderately considering the convenience of a tour. Eightly, when water-proof cables for the lightening bulbs are connected each other, silicon tape is suitable and circuit breakers should be installed at the diverging points of the cables. Ninthly, the direction and angle of the lightening must be changed periodically to prevent green-pollution at the lightening spot. Lastly, when facilities and arrangements are equipped, corrosive materials should be excluded if circumstances allow.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.31-37
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• 2017

A synergistic effect was observed in the combination of nitrite and ethanolamines. Ethanolamine is one of the representative organic corrosion inhibitors and can be categorized as adsorption type. However, nitrosamines can form when amines mix with sodium nitrite. Since nitrosamine is a carcinogen, the co-addition of nitrite and ethanolamine will be not practical, and thus, a non-toxic combination of inhibitors shall be needed. In order to maximize the effect of monoethanolamine, we focused on the addition of molybdate. Molybdate has been used to alternate the addition of chromate, but it showed insufficient oxidizing power relative to corrosion inhibitors. This work evaluated the synergistic effect of the co-addition of molybdate and monoethanolamine, and its corrosion mechanism was elucidated. A high concentration of molybdate or monoethanolamine was needed to inhibit the corrosion of ductile cast iron in tap water, but in the case of the co-addition of molybdate and monoethanolamine, a synergistic effect was observed. This synergistic effect could be attributed to the molybdate that partly oxidizes the metallic surface and the monoethanolamine that is simultaneously adsorbed on the graphite surface. This adsorbed layer then acts as the barrier layer that mitigates galvanic corrosion between the graphite and the matrix.

• Journal of the Korea Society for Simulation
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• v.22 no.2
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• pp.93-100
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• 2013

Mixed model production system means that various products are manufactured alternately in a line, and it has become a popular system in the era of multi-product small-quantity production. However, in the mixed model production system using flow line, the unbalance among stations is not inevitable because the workloads of stations cannot be the same. Thus, flow line system has been replaced to cellular manufacturing system for reducing the loss of waiting due to the unbalance of stations. In this paper, we introduce the simulation case study of an automated welding line which produces the parts of excavator. The factory has considered replacing the mixed model flow line to the cellular manufacturing system based on FMC concept. The increase of production quantity is estimated about 26.7%, and the lead time is reduced more than 55%. Furthermore sensitivity analyses are conducted considering the changes of product-mix.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.637-645
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• 2017

Jeju Island is composed of irregular volcanic rock layers formed by several volcanic activities. Since structure such as the offshore wind turbine has to support considerably large over turning moment due to long distance from foundation to load point and relatively large horizontal load. Pile foundations are needed to economically support such structure even in the case of rock layer. Therefore, in this study, mechanical performances are estimated by mixing ratio of water, cement, and sand to figure out optimal mixing ration of filling material for pile penetrated to rocky layers, and outcomes of this study are compared and analyzed with results of other researches. In the same conditions, mechanical performances of the mortar (S/(S+C)=20~40%) are better than those of cement paste and soil cement. On the basis of major outcome of this study, appropriate range of mixing and a strengthening model are suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1101-1104
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• 2008

Recently, active researches are conducted on high performance concrete(HPC) exhibiting high strength and high fluidity. These researches are resulting in increased applications on real structures. In order to satisfy the required performances, HPC makes use of large quantities of binder and presents low water-cementitious material ratio. Such mixing is increasing significantly the autogenous shrinkage, which subsequently is likely to favor the potential development of cracks. Therefore, we investigated the effect of used materials and mix proportions on the shrinkage properties of HPC, and of the use of expansive additives and shrinkage reducing agents on the HPC. The autogenous shrinkage of HPC using blast furnace slag are tend to be increased, in some case have the potential development of cracks by only the autogenous shrinkage. Also the using method in combination with expansive additive and shrinkage reducing agent is more effective than the separately using method of that.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.1
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• pp.120-127
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• 2000

Deep-fat frying is a common cooking practice. There has been considerable concern regarding the mutagenic and carcinogenic potential of thermally oxidized oils. Studies on deep-fried foods so far have revealed not much on the mutagenicity of the oils in the foods. Therefore, in the present study, it was attempted to investigate the mutagenicity ofthe thermally oxidized safflower oil. Oil was heated in a home-fryer at a temperature of 180$\pm$3$^{\circ}C$ for 48 hours. Oil samples were taken at 0, 8, 16, 24, 32, 40 and 48 hours of heating, respectively. Each sample was used to study the changes in peroxide value (POV), acid value (AV), iodine value (IV), conjugated dienoic acid (CDA) content, %, and fatty acid composition. Another series of samples were fractionated into non-polar and polar fractions by column chromatography. The mutagenicity of the samples taken from the thermally oxidized oils, as well as the non-polar and polar fractions of the thermally oxidized oils, was investigated with the Ames test. The Ames test was carried out with and without metabolic activation. Bacterial tester strains used in the present study were the histidine auxotrophic strains of Salmonella typhimurium TA100, TA1535 and TA102 were used for the detection of base pair mutations, and TA98 and TA1537 for frame shift mutations. Each series of samples was dissolved in tetraphydrofuran (inhibitor-free) and tested at doses ranging from 0.05 to 5 mg/plate. None of the oil samples taken during the 48 hour oxidation period showed any mugagenic activity. This was the case, even after the activaton with 59 mix. Also, none of the polar and non-polar fractions showed any mutagenic activity on all the strains tested.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.673-676
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• 2008

Recent trends show an increased usage of 'colored concrete', a inorganic pigmented concrete mix, especially in small to large scale buildings. However, due to lack of regulations, current usage of colored concrete indicates a lack of consideration for safety factors and aesthetic aspects. Sometimes color pigmentation used in paints are inappropriately used in concrete, and in many cases the addition of coloring material is done without proper research into how structural characteristics of resulting concrete may have been affected. To resolve these issues, some construction sites apply ASTM or ACI regulations. However, such regulations incorporate elements that cannot be applied in Korea, which makes their domestic application impractical. In this paper, the primary aim is to determine to what extent the basic material characteristics of concrete is affected by the variety and quantity of different color pigments, and in so doing establish a foundation for future reference in case of construction projects involving the use of colored concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1532-1548
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• 2008

The tunnel type spillways is under construction to increasing water reservoir capacity in Dae-am dam. The tunnel outlet was planned to be made after installing slope stabilization system on natural slope there. Generally, the tunnel outlet is made perpendicularly to the slope, but in this case, it had to be made obliquely to the slope for not interrupting flow of river. Because of excavation in condition of natural slope caused to deflecting earth pressure, the outlet couldn't be made. So, artificial ground made with concrete that it was constructed in the outside of tunnel for producing the arching effect which enables to make a outlet. We were planned tunnel excavation was carried out after artificial ground made. Artificial ground made by poor mix concrete of which it was planned that the thickness was at least 3.0m height from outside of tunnel lining and 30cm of height per pouring. Spreading and compaction was planned utilized weight of 15 ton roller machine. In order to access of working truck, slope of artificial ground was designed 1:1.0 and applied 2% slope in upper pert of it for easily drainage of water. In addition to, upper pert of artificial ground was covered with soil, because of impaction of rock fall from upper slope was made minimum. The tunnel excavation of the artificial ground was designed application with special blasting method that it was Super Wedge and control blasting utilized with pre-percussion hole.