• Journal of the Korean Geophysical Society
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• 제4권1호
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• pp.1-10
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• 2001

A number of tangible cultural properties have been left to suffering damage without any scientific conservation or maintenance. We conducted nondestructive geophysical explorations around the Western pagoda of the Iksan Mireuksa Temple for the purpose of preparing the counterplan of its conservation and maintenance and of utilizing the geophysical information for the design of repair. Geophysical image of the shallow subsurface around the construct resulting from electric resistivity, seismic refraction, and GPR methods carried out along 6 lines in the site was used to investigate the relationship between the foundation characteristics and the structural safety. Tilting of the pagoda southwest towards seems to result from the low resistivity zones found in the southwestern part. The GPR and seismic surveys revealed a boundary at depth of 3.3～3.5m dividing into two layers, compacted overlaid soil and the original ground. The boundary appears to dip southwest. The artificial layer as a foundation does not covers as much as the bottom area of the pagoda. This top soil dipping southwest seems to result in tilting of foundation southwestward towards. Our geophysical result suggests ground reinforcement in the western part of the survey area for the conservation of the construct.

• Journal of Adhesion and Interface
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• 제20권2호
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• pp.66-70
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• 2019

The surface of hydrophobic polypropylene (PP) fibers (spun-bonded fabric) was treated by an atmospheric plasma treatment method. These pre-treated hydrophilic PP fabrics were dip-coated in the aqueous poly(N-vinyl pyrrolidone) (PVP) solution. PVP layers on the surface of PP fiber were crosslinked by an irradiation of electron beam. The thickness of PVP hydrogels coated on the surface was easily controlled by changing the concentration of PVP in coating solution. The stepwise surface treatment, PVP coating, and hydrogel formation via electron beam irradiation were analyzed by the measurement of contact angle, scanning electron microscopy, and optical microscopy.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권1호
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• pp.1-8
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• 2019

Most of rotor resistance estimators utilizes Classical qd Model (CQDM) and Alternate qd Model (AQDM). The rotor resistance estimators based on both models were shown to provide an accurate rotor resistance estimate under conditions where flux is constant such as a field-oriented control (FOC) based induction motor drives. Under the conditions where flux is varying such as a Maximum torque per amp (MTPA) control, AQDM based rotor resistance estimator estimates actual rotor resistance accurately even in different operating points. However, CQDM based rotor resistance estimator has not been investigated and its performance is questionable under condition where flux level is varying. Thus, in this work, the performance of CQDM based rotor resistance estimator was investigated and made comparisons with AQDM based estimator under conditions where flux level is significantly varying such as in MTPA control based induction motor drives. Unlike AQDM based estimator, the laboratory results show that the CQDM based estimator underestimates actual rotor resistance and exhibits an undesirable dip in the estimates in different operating points.

• The Plant Pathology Journal
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• 제35권1호
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• pp.77-83
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• 2019

Chlorine dioxide ($ClO_2$) can be used as an alternative disinfectant for controlling fungal contamination during postharvest storage. In this study, we tested the in vitro and in vivo inhibitory effects of gaseous $ClO_2$ against Diaporthe batatas SP-d1, the causal agent of sweetpotato dry rot. In in vitro tests, spore suspensions of SP-d1 spread on acidified potato dextrose agar were treated with various $ClO_2$ concentrations (1-20 ppm) for 0-60 min. Fungal growth was significantly inhibited at 1 ppm of $ClO_2$ treatment for 30 min, and completely inhibited at 20 ppm. In in vivo tests, spore suspensions were drop-inoculated onto sweetpotato slices, followed by $ClO_2$ treatment with different concentrations and durations. Lesion diameters were not significantly different between the tested $ClO_2$ concentrations; however, lesion diameters significantly decreased upon increasing the exposure time. Similarly, fungal populations decreased at the tested $ClO_2$ concentrations over time. However, the sliced tissue itself hardened after 60-min $ClO_2$ treatments, especially at 20 ppm of $ClO_2$. When sweetpotato roots were dip-inoculated in spore suspensions for 10 min prior to treatment with 20 and 40 ppm of $ClO_2$ for 0-60 min, fungal populations decreased with increasing $ClO_2$ concentrations. Taken together, these results showed that gaseous $ClO_2$ could significantly inhibit D. batatas growth and dry rot development in sweetpotato. Overall, gaseous $ClO_2$ could be used to control this fungal disease during the postharvest storage of sweetpotato.

• The Plant Pathology Journal
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• 제35권5호
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• pp.437-444
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• 2019

Chlorine dioxide ($ClO_2$) has been widely used as an effective disinfectant to control fungal contamination during postharvest crop storage. In this study, Fusarium oxysporum f. sp. batatas SP-f6 from the black rot symptom of sweetpotato was isolated and identified using phylogenetic analysis of elongation factor 1-${\alpha}$ gene; we further examined the in vitro and in vivo inhibitory activities of $ClO_2$ gas against the fungus. In the in vitro medium tests, fungal population was significantly inhibited upon increasing the concentration and exposure time. In in vivo tests, spore suspensions were drop-inoculated onto sweetpotato slices, followed by treatment using various $ClO_2$ concentrations and treatment times to assess fungus-induced disease development in the slices. Lesion diameters decreased at the tested $ClO_2$ concentrations over time. When sweetpotato roots were dip-inoculated in spore suspensions prior to treatment with 20 and 40 ppm of $ClO_2$ for 0-60 min, fungal populations significantly decreased at the tested concentrations for 30-60 min. Taken together, these results showed that $ClO_2$ gas can effectively inhibit fungal growth and disease development caused by F. oxysporum f. sp. batatas on sweetpotato. Therefore, $ClO_2$ gas may be used as a sanitizer to control this fungus during postharvest storage of sweetpotato.

• Journal of the Korean GEO-environmental Society
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• 제20권11호
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• pp.5-10
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• 2019

For the development of long-wavelength responding photocatalyst, Ag was applied to commercial $TiO_2$ to produce $Ag/TiO_2$ photocatalyst. Moreover, micro-emulsion method was used in order to increase the efficiency of the photocatalyst by enhancing the dispersion of Ag. Physical properties of the manufactured catalyst were analyzed by scanning electron microscopy (SEM), field emission transmission electron microscopy (FE-TEM) and diffuse reflectance spectroscopy (DRS). For the catalytic performance measurement, RO 16 (Reactive Orange 16) removal was performed with 25 ppm RO 16 under UV-A (365 nm) irradiation. In addition, ball milling and dip-coating method were used to synthesize the photocatalyst for the comparison of the outcomes of using different synthesis methods. In addition, catalytic performance was improved by varying the Ag content and surfactant content. The highest catalytic performance was shown at $Ag/TiO_2$ synthesized by micro-emulsion method with 2 wt% of Ag content, and 0.5 g of the surfactant.

• Korean Journal of Metals and Materials
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• 제46권5호
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• pp.289-295
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• 2008

The effect of the alloy elements(Si/Mn) ratio on the coating quality including wettabilty with molten zinc, galvannealing kinetics and crater has been investigated in interstitial-free high strength steel(IFHSS) containing Si and Mn. When the Si/Mn ratio was below 0.75, IF-HSS exhibited a good wettability leading to a good galvannealed coating quality after annealing at $800^{\circ}C$ for 40s in $15%H_2-N_2$ mixed gas with dew point $-60^{\circ}C$. In contrast, the wettability and galvannealed coating quality were deteriorated in the Si/ Mn ratio above 0.75. It is shown that they have relevance to oxides forms by selective oxidation on the steel surface. The oxide particles dispersed on the steel surface with a surface coverage of below 40% resulted in good wettability and galvannealed coating quality. The oxide particle is mainly consisted of $Mn_2SiO_4$ with low contact angle in molten zinc. On the other hand, the continuous oxide layer on the steel surface, such as network- and film-type,caused to poor wettability and galvannealed coating quality. The coverage of oxide layer was above 80%, and its chemical species was $SiO_2$ with high contact angle in molten zinc. Consequently, the Si/Mn alloy ratio played an importance role in galvannealed coating quality of IF-HSS.

• Korean Journal of Metals and Materials
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• 제46권7호
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• pp.427-436
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• 2008

The effect of dewpoints on annealing behavior and coating characteristics such as wettability and galvannealing kinetics was studied by annealing 0.3wt%Si - 0.1~0.4wt% Mn added interstitial-free high strength steels(IF-HSS). The 0.3wt%Si-0.1wt%Mn steel exhibited good wettability with molten zinc and galvannealing kinetics after annealing when the dewpoint of $H_2-N_2$ mixed gas was above $-20^{\circ}C$. It is shown that the wettability and galvannealing kinetics are directly related to the coverage of the external(surface) oxide formed by selective oxidation during annealing. At $N_2-15%H_2$ annealing atmosphere, the increase of dewpoint results in a gradual transition from external to internal selective oxidation. The decrease of external oxidation of alloying elements with a concurrent increase of their subsurface enrichment in the substrate, showing a larger surface area that was free of oxide particles, contributed to the improved wettability and galvannealing kinetics. On the other hand, the corresponding wettability and galvannealing kinetics were deteriorated with the dewpoints below $-20^{\circ}C$. The continuous oxide layer of network and/or film type was formed on the steel surface, leading to the poor wettability and galvannealing kinetics. It causes a high contact angle between annealed surface and molten zinc and plays an interrupting role in interdiffusion of Zn and Fe during galvannealing process.

• Korean Journal of Metals and Materials
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• 제50권12호
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• pp.873-882
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• 2012

Dual Phase (DP) steel which has a soft ferrite phase and a hard martensite phase reveals both high strength and high ductility and has received increased attention for use in automotive applications. To conduct structural analysis to verify vehicle safety, highly credible experimental results are required. In this study, tensile tests were performed in a strain rate range from $10^{-4}/s$ to 300/s for Sink Roll-Less (SRL) hot-dip metal coated sheets. Collision properties were estimated through simulation by LS-DYNA using the stress-strain curve obtained from the tensile test. The simulation results were compared with the actual crash test results to confirm the credibility of the simulation. In addition, a tensile test and a crash test with 2% prestrain and a baking (PB) specimen were evaluated identically because automotive steel is used after forming and painting. The mechanical behaviors were improved with an increasing strain rate regardless of the PB treatment. Thus, plastic deformation with an appropriate strain rate is expected to result in better formability and crash characteristics than plastic deformation with a static strain rate. The ultimate tensile strength (UTS) and absorbed energy up to 10% strain were improved even though the total elongation decreased after PB treatment, The results of the experimental crash test and computer simulation were slightly different but generally, a similar propensity was seen.

• Journal of the Korean institute of surface engineering
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• 제53권6호
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• pp.293-299
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• 2020

The characteristics of the polycarbosilane (PCS)-based composite ceramic layer was studied by controlling the curing temperature. The stress at the interface of the graphite and SiOC composite layer was evaluated v ia finite element analysis. As a result, the tensile stress was released as the carbon ratio of the SiC decreases. In experiment, the SiOC layers were coated on the VDR graphite block by dip-coating process. It was revealed that the composition of Si and C was effectively adjusted depending on the curing temperature. As the solution-based process is employed, the surface roughness was reduced for the appropriate PCS curing temperature. Hence, it is expected that the cured SiOC layer can be utilized to reduce cracking and peeling of SiC ceramic composites on graphite mold by improving the interfacial stress and surface roughness.