• 보존과학연구
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• s.30
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• pp.125-136
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• 2009

Stone cultural heritages in Korea have a severe damages from chemical and biological weathering because most of them have been situated in outdoors without any suitable protection systems, and this in turn causes deformation and structural damage. To counteract these problems and increase durability, various kinds of conservation materials are used in the conservation and restoration treatments. However until now there are not many practical and technological experiments on this subject. This paper attempts quantitative evaluation of effectiveness about chemical of ethylsilicate based resin for sandstone in Yeongyang-gun. It takes a long time to evaluate durability and side effect after conservation materials treatment. So we use artificial weathering through freezing§ thawing experimental method. As a result of this experiment, porosity and absorptance increased, and elastic wave speed, elastic modules, unconfined compression strength and tensile strength decreased more than before. This study plans to make a scientific method study about weathering factor and mechanism, and to deduce correlation between artificial weathering and natural weathering.

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.3
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• pp.348-356
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• 2013

Denim washing is processed with different washing techniques such as stone washing, chemical washing, sand washing, and bio washing. Cellulase bio washing can meet environmental regulations that enhance and rectify problems associated with traditional decolorization techniques; however, stone washing needs to be added to the processing because it produces a low decolorization effect. There is also the problem of additional strength reduction. To prevent these problems, a new enzyme for bio washing is required. This study examines the optimum laccase treatment conditions on denim and evaluated the characteristics of laccase-treated denims to establish a database of eco-friendly new decolorization process on denim using a new laccase enzyme. The results show that the optimum conditions of laccase on denim are a pH of 4.0, $30^{\circ}C$, 7% (o.w.f.), and 6 hours in 10 mM of buffer concentration. UV absorbance and HPLC identified isatin coexist with anthranilic acid in solution after laccase treatment on denim. Results of the surface color, the surface morphology and the tensile strength indicate that laccase treatment shows an excellent decolorization effect without fiber damage. The wet cleaning fastness and the perspiration fastness also improved.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.5 no.2
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• pp.38-41
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• 1999

This study was carried out to investigate improvement of kraft paper sack mixed with recycled paper for sugars and assorted feeds. Four Plies of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) were taken place of two plies of kraft paper made from all pulp(basis weight : $98g/m^2$) and one ply of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) for sugar 30kg. Three Plies of kraft paper mixed with recycled paper(basis weight : $80g/m^2$) were taken place of two plies of kraft paper made from all pulp(basis weight $98g/m^2$) for sugar 15kg and assorted feed 25kg. Physical properties, tensile strength, internal tearing strength and bursting strength, were improved by exchanging kraft paper mixed with recycled paper for kraft paper from all pulp and so kraft paper sacks made from all pulp were no damage in handling. They had so high friction coefficient that there was no danger of collapse on pallet by slipperiness in transportation and handling. And they had high printability so disappearance of printing by the contact with other paper sack in transportation was not found.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.910-914
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• 2012

In constructing all kinds of equipment and steel structures, discontinuous areas such as weld defects formed in a welded structure tend to generate cracks that will result in damage. In this study, ATOS high-strength steel welding becomes important in butt welding where the tensile strength of the steel is over 80kg/$mm^2$. Structural discontinuities such as joints are more susceptible cracks in part due to their repeated loading and fatigue crack growth. The quality of parts produced depend or the shielded amounts of steel and on the skill of the welders in making strong welds. It is true that there are many factors that can be used to generate a lot of research in this area. However geometry and load conditions due to the combined effects with many issues could be solved through this study. Butt welding material at a plate thickness of 12t in ATOS 80 high-strength steel with a 4 pass, 20l/min, 24V/200A welder is good at making specimens with the quality shown in radiographic testing.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.117-125
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• 2013

PURPOSES : The purpose of this study is to evaluate of field application and laboratory performance of warm-mix asphalt (WMA) according to the dosage rate of organic-based WMA additive. METHODS: Three asphalt mixtures, i.e., hot mix asphalt (HMA), WMA with the dosage rate of 1.5%, WMA with the dosage rate of 1.0%, were sampled from the asphalt plant when the field trial project were constructed. With these mixtures, the laboratory testings were performed to evaluate the linear viscoelastic characteristics and the resistance to moisture, rutting and fatigue damage. RESULTS : From the laboratory test results, it was found that the WMA with the reduced dosage rate of additive would be comparable to HMA and WMA with the original dosage rate in terms of the dynamic modulus, tensile strength ratio, rutting resistance. However, the fatigue reisistance of WMA with the reduced dosage rate was slightly worse but it should be noted that the fatigue performance is necessarily predicted by combining the material properties and pavement structure. CONCLUSIONS: Through the field construction and laboratory testings, the dosage rate of organic-based WMA additive could be reduced from 1.5% to 1.0% without the significant decrease of compactability and laboratory performance. The long-term performance of the constructed pavement will be periodically monitored to support the findings from this study.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.397-401
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• 2015

In this study, analysed the characteristics of power drop and surface damage in solar cell through high temperature and humidity test in the 3 case of EVA(ethylene vinyl acetate) and 2 case ribbon thickness. The solar cells were tested during the 500hr in $85^{\circ}C$ temperature and 85% relative humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). Through the EL(Electroluminescence) shots, specimen's surface have partialy damaged. Before and after high humidity and high temperature test, ribbon thickness $200{\mu}m$ EVA1 case power drop rate was 8.463%, EVA2 case was 6.667%, EVA3 case was 6.373%. In the ribbon thickness $250{\mu}m$ EVA1 case power drop rate was 6.521%, EVA2 case was 8.517%, EVA3 case was 6.019%. EVA3 case was the lowest power and FF(fill factor) drop rate at the 2 case of ribbon thickness, because EVA3 is laerger than EVA1 and EVA2 in thickness, elongation and tensile strength.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.196-203
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• 2008

Durability of geosynthetics for soil reinforcement is accounted for creep and creep rupture, installation damage and weathering, chemical and biological degradation. Among these, the long-term creep properties have been considered as the most important factors which are directly related to the failure of geosynthetic-reinforced soil(GRS). However, the creep test methods and strain limits are too various to compare the test results with each other. The most widely used test methods are conventional creep test, time-temperature superposition and stepped isothermal method as accelerated creep tests. Recently developed design guidelines recommend that creep-rupture curve be used to determine the creep reduction factor($RF_{CR}$) which is a conservative approach. In this study, the different creep test methods were compared and the creep reduction factors were estimated at different creep strain limits of 10% of total creep strain and creep rupture. In order to minimize the impact of creep strain to the GRS structures, the various creep reduction factors using different creep test methods should be investigated and then the most appropriated one should be selected for incorporating into the design.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.114-115
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• 2019

When concrete is exposed to fire, the decomposition of Portland cement paste results in critical damage to the concrete structure of a building. Although the behavior of cement pastes after heating provides crucial information with respect to the reuse of the building exposed to fire, the recovery process of the damaged concrete structure has not yet been fully elucidated. In addition, research on appropriate additives such as carbon nanotube (CNT) has been increasing recently, however, investigation of CNT incorporated cement paste after decomposition of CNT by high temperature is not fully investigated. In this study, we investigated the physicochemical properties of CNT incorporated cement paste under different temperatures (200℃, 500℃ and 800℃). Also, the effects of different rehydration conditions (20℃ 60% RH and in water for different curing times) on the recovery of the paste were studied. The changes in tensile and compressive strength, surface observation of the specimens were characterized. In addition, the decomposition and formation of hydrates in the paste due to the heating process were studied using X-ray diffraction.

• Steel and Composite Structures
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• v.24 no.4
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• pp.467-479
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• 2017

The stud is one of the most frequently used shear connectors which are important to the steel-concrete composite action. The static and fatigue behavior of stud in the steel fiber reinforced concrete (SFRC) were particularly concerned in this study through the push-out tests and analysis. It was for the purpose of investigating and explaining a tendency proposed by the current existing researches that the SFRC may ameliorate the shear connector's mechanical performance, and thus contributing to the corresponding design practice. There were 20 test specimens in the tests and 8 models in the analysis. According to the test and analysis results, the SFRC had an obvious effect of restraining the concrete damage and improving the stud static performance when the compressive strength of the host concrete was relatively low. As to the fatigue aspect, the steel fibers in concrete also tended to improve the stud fatigue life, and the favorable tensile performance of SFRC may be the main reason. But such effect was found to vary with the fatigue load range. Moreover, the static and fatigue test results were compared with several design codes. Particularly, the fatigue life estimation of Eurocode 4 appeared to be less conservative than that of AASHTO, and to have higher safety redundancy than that of JSCE hybrid structure guideline.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.4
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• pp.525-531
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• 2007

The operating temperature has been increased to improve the efficiency of gas turbine. The most advanced Gas turbine is operated at above $1,500^{\circ}C$. Improvement in material and cooling method permit hot gas path component to run at increased temperature. But, the repair of blades which are developed with advanced manufacture technique is difficult to use normal welding. Most of gas turbine blades are made of precipitation harden nickel base superalloy, which is very hard to weld. Therefore, the employment of welding filler on blade is solid solution nickel base superalloy(Hastelloy X, Inconel 617). In this study, Tensile test in high temperature was conducted on welded GTD111DS with GTD111 to evaluate effect of variation of pre, post treatment. The result of this study showed that the specimen was treated with optimum pre and post treatment(preweld HT($1200^{\circ}C$), Post treatment($1100^{\circ}C$ HIP, $1200^{\circ}C$ + $1100^{\circ}C$ + $800^{\circ}C$ HT) is mush superior.