• Composites Research
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• v.29 no.2
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• pp.79-84
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• 2016

An adhesive can be used to connect two different materials in structures. In comparing with other connecting methods, such as bolt, rivet, and hot melting, the adhesive does not need to use them. It leads to reduce the weight and decrease the stress concentration along the connecting line. This work studied the comparison of mechanical and interfacial properties of commonly-used two adhesives, acrylic type and bisphenol-A epoxy type. Tensile and flexural strength of neat adhesives were also compared. Lap shear test of two adhesives was deduced from the measurement of tensile and fatigue tests. After testing, the failure patterns of adhesive surfaces were observed by a microscope. Tensile strength and mechanical fatigue resistance at using bisphenol-A epoxy adhesive were better than acrylic adhesive. Also adding CNT reinforcement in epoxy adhesive can anticipate mechanical improvement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.965-975
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• 2014

Pretension PSC (Prestressed Concrete) members are subjected to a certain limit of size as they are generally produced in the off-site plant and transferred to the site due to the large scale of the product on system. In this study, a portable pretensioning production system has been developed, which allow us to apply the pretension method on site. Considering that a 50m span PSC girder using the pretension method requires a pressing device to endure a large jacking force, the portable pretension production system has to ensure safety against such a large pretension jacking force. In this study, the portable pretensioning system to produce a 50m span pretension girder was manufactured by using CFT (Concrete Filled steel Tube) members. In order to understand the stability of the system and the behavior of the elements, a static loading test was conducted and the stability of the proposed portable pretensioning production system was confirmed. The developed portable pretension system was applied to several construction sites and was investigated the problems on site. During the pretension girder and slab members that was producted by this pretension system in construction site, it has be found the several advantages such as simple fabrication processes, reduction of prestress-loss, and a decrease of 15% compared with the fabrcation cost of post-tension girder. After due consideration of the problems, this portable pretension system will be improved.

• Journal of fish pathology
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• v.30 no.1
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• pp.41-49
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• 2017

Probiotic principles can be applied in aquaculture for the purpose of growth and immunity stimulation, disease prevention and eventually better production performance. This study was to assess effects of combinations of microbes containing two Bacillus sp., plus one Lactobacillus sp. as the basal preparation (BSL-LAB), and additional Nitrosomonas sp. (nitrifying bacteria consortium, NBS) in olive flounder (Paralichthys olivaceus). The effects examined were growth parameters, hematologic parameters, innate immunity and pathogen challenge test. Fish were assigned to 4 treatments as Control (no probiotics), Group A (Bacillius and Lactobacillus to culture water), Group B (Bacillius and Lactobacillus both in water and feed), Group C (same as Group B with additional Nitrosomonas in feed). Fish were allocated to the above 4 groups, each group being composed of triplicate 30 fish, for a 7-week feeding in the laboratory. Positive effects were observed both in growth and pathogen sensitivity with all three probiotic combinations. Such effects were attributed to improved innate immune functions. This result indicates that the tested probiotic microbes are beneficial to olive flounder aquaculture.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.43-55
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• 2007

Gyeonggi-do has conducted bus management and service evaluation of bus operating company since 2005 under the law for promoting public transportation. The evaluation results are used for improving bus service, making policy, and estimating incentives to bus companies. A lot of cost and man-month are needed to evaluate bus management and service for bus operating company, and many companies are against the evaluation. Therefore, the effect analysis on evaluation system should be followed to maintain it. This research results in the evaluation system has positive effects through quantitative and qualitative analysis. The data of bus company's operation condition in 2005 and 2006 are used for a comparative analysis. From the survey result for the company, bus drivers, and administrators, it results that positive effects are predominant. The results of this research could be used for a shield against some criticism about appropriateness of the evaluation criteria and effectiveness of the evaluation system. For improving bus service, evaluation items and criteria could be added or adjusted based on this research.

• Food Science and Preservation
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• v.19 no.2
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• pp.216-222
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• 2012

The optimum annealing conditions of corn starch slurry were studied for RS4 type resistant starch production by phosphorylated cross-linking. When a corn starch slurry was cross-linked by using phosphate salts (STMP/STPP mixture) in the presence of 0.9%, 1.2% and 1.5% NaOH/st.ds, a high concentration of NaOH resulted in a rapid increase of the RS contents at the early reaction stage. However, similar RS contents were obtained after 12 h of cross-linking regardless of NaOH concentrations. The annealing treatment was conducted under various conditions such as pH between 2-10, temperature $40-60^{\circ}C$, time 0-14 h followed by phosphorylated cross-linking. The lower slurry pH was for the annealing treatment, the higher RS contents were obtained after cross-linking. When the slurry annealed for various period of time and temperature, a maximal amount of RS was formed after 2 h of annealing at $50^{\circ}C$ of annealing temperature of the starch slurry (pH 2.0). Therefore, an optimal annealing conditions at pH 2.0 and $50^{\circ}C$ for 2 h were proposed under the cross-linking conditions of sodium sulfate 10%/st.ds, NaOH 1.2%/st.ds and 12 h of the reaction time. The RS contents were linearly increased with the increase of phosphate salt addition. The RS4 prepared under the optimal conditions contained RS 72.3% and its phosphorus content was 0.36%/st.ds, which was below the limit (0.4%/st.ds) of modified starch by Korea Food Additives Code.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.485-488
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that mortar using recycled fine aggregate containing calcined gypsum has lowest compressive strength. It seems that low compressive strength is closely associated with the expansion of the specimen by excessive formation of ettringite.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.936-944
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• 2019

Submarines, which have been called an invisible force, are strategic underwater weapon systems that perform missions such as anti-surface warfare, anti-submarine warfare, and high payoff target strikes with the advantage of underwater covertness. A submarine should be able to withstand the hydrostatic pressure of the deep sea. In this respect, the submarine pressure hull, as the main structural system to resist the external pressure corresponding to the submerged depth, should ensure the survivability from hazards and threats such as leakage, fires, shock, explosion, etc. To do this, the initial scantling of the submarine pressure hull must be calculated appropriately in the concept design phase. The shape of the aft transition ring varies according to its connection with the submarine aft end conical structure, pressure hull cylindrical part, and non-pressure hull of the submarine; the design of the aft transition ring should not only take into account stress flow and connectivity but also the cost increase due to the increased man-hours of its complex geometry. Therefore, trade-off studies based on the four different shapes of the aft transition ring are carried out considering both the review of the structural strength through nonlinear finite element analysis (FEA) and economic feasibility by reviewing the estimations of the manufacturing working days and material costs. Finally, the most rational structural aft transition ring shape for a submarine amongst four reviewed types was proposed.

• Korean Journal of Labor Studies
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• v.24 no.1
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• pp.157-196
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• 2018

This study analyzes non-standard workers' attitudes and behaviors towards standard workers' strikes using the case of a joint strike held by journalists at KBS and MBC in 2012. Tracing the process since 2008 by which a conservative government has tried to control the press and regular journalists have collectively resisted against it, we put our analytical focus on two major groups of freelance broadcast professionals: independent producers and writers in current affairs. Specifically, we examine 1) how they perceived and responded to a series of regular journalists' struggle to protect journalistic value, 2) how such perception of and response to regular journalists could be developed, and 3) how (de)solidarity could form and then deepened between freelance and regular journalists in the 2012 Media Strike. Our findings show that the ways in which regular journalists had controlled freelance journalists at work affected the relationship between class-based and occupation-based rationality freelance journalists held in their minds. Independent producers, who had developed a strong class-based rationality in response to the coercive input-output control, showed cynicism about regular journalists' strike pointing out their hypocrisy and contradiction. In contrast, freelance writers accommodated and joined the strike by regular workers in the spirit of solidarity based on occupational rationality which had developed from normative, process control. Our paper ends with theoretical and practical implications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.32-36
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• 2021

This study was investigated in carbon diffusion behavior of laser-carburized TiZrN coating layer and the changes of mechanical properties. The carbon paste was deposited on TiZrN coatings, and the laser was irradiated to carburize into the coatings. The XRD peak corresponding to the (111) plane shifted to a lower angle after the carburization, showing the lattice expansion by doped carbon. The decreased grain size implied the compression by the grain boundary diffusion of carbon. The XPS spectra for the bonding states of carbon was analyzed that carbon was substitute to nitrogen atoms in TiZrN, as carbide, through the thermal energy of laser. In addition, the combination of sp2 and sp3 hybridized bonds represented the formation of an amorphous carbon. The cross-sectional TEM image and the inverse FFT of the TiZrN coating after carburizing were observed as the wavy shape, confirming the amorphous phase located in grain boundaries. After the carburization, the hardness increased from 34.57 GPa to 38.24 GPa, and the friction coefficient decreased by 83 %. In particular, the ratio of hardness and elastic modulus (H/E) which is used as an index of the elastic recovery, increased from 0.11 to 0.15 and the wear rate improved by 65 %.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.27-35
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• 2004

Recalcitrant 4-t-Octylphenol used as a surfactant was subjected to the biodegradation with wood rot fungi, Basidioradulum molare and Schizopora paradoxa. Two fungi were grown in the culture medium containing various concentrations of 4-t-Octylphenol in order to investigate their resistance against 4-t-octylphenol Schizopora paradoxa was reached to the full growth within 14 incubation days in the concentration of more than 200 ppm of 4-t-Octylphenol, while Basidioradulum molare showed the inhibitory mycelium growth as the concentration was increased Schizopora paradoxa and Basidioradulum molare biodegraded 95% and 36% of initial concentration of 4-t-Octylphenol at first incubation day, respectively. However, the biodegradation capability reached to more than 95% after 3 incubation days. During the biodegradation of 4-t-Octylphenol, the activity of manganese dependent peroxidase was induced by the addition of 4-t-Octylphenol in the culture medium of Schizopora paradoxa, but that of laccase was maximal before the addition. The reduction of estrogenecity was assayed by MCF-7 cell proliferation test and measurement of pS2 mRNA expression. The level of pS2 mRNA was decreased down to the level of baseline at first incubation day. Also, estrogenecity of 4-t-Ocrylphenol completely disappeared after treatment with supernatant by Schizopora paradoxa and Basidioradulum molare from first incubation day of culture down to the levels of vehicle.