• Molecules and Cells
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• v.28 no.5
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• pp.473-477
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• 2009

Previously, the 9-mer analog peptides, 9Pbw2 and 9Pbw4, were designed based on a defensin-like peptide, protaetiamycine isolated from Protaetia brevitarsis. In this study, antifungal effects of the analog peptides were investigated. The antifungal susceptibility testing exhibited that 9Pbw4 contained more potent antifungal activities than 9Pbw2. A PI influx assay confirmed the effects of the analog peptides and demonstrated that the peptides exerted their activity by a membrane-active mechanism, in an energy-independent manner. As the noteworthy potency of 9Pbw4, the mechanism(s) of 9Pbw4 were further investigated. The membrane studies, using rhodamine-labeled giant unilamellar vesicle (GUV) and fluorescein isothiocyanate (FITC)-dextran loaded liposome, suggested that the membrane-active mechanism of 9Pbw4 could have originated from the pore-forming action and the radii of pores was presumed to be anywhere from 1.8 nm to 3.3 nm. These results were confirmed by 3D-flow cytometric contour-plot analysis. The present study suggests a potential of 9Pbw4 as a novel antifungal peptide.

• Proceedings of the KAIS Fall Conference
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• 2011.12a
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• pp.200-203
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• 2011

A copper-based metal organic framework (MOF) named Cu-BTC, also known as HKUST-1, was synthesized by using a solvothermal method at various synthesis temperature, time and pressure. The obtained samples were characterized with Powder X-ray diffraction (XRD) for phase structure, scanning electron microscopy (SEM) for crystal structure, and nitrogen adsorption-desorption for pore textural structure. The Cu-BTC sample was also studied for $CO_2$ adsorption. The analysis results displayed that the sample synthesized at the condition of temperature: $120^{\circ}C$, synthesis time: 12 hours, pressure: 1 bar exhibited a good crystal structure with uniform size of octahedral particles. The BET data revealed a high surface area of 1741.7 $m^2g^{-1}$ and a pore volume of 0.7137 $cm^3g^{-1}$and exhibiteda maximum $CO_2$ adsorption capacity of 170 mg/g of the sorbent at $25^{\circ}C$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.213-214
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• 2009

A thin film hydroxyapatite (HA) films was deposited on anodized titanium by RF sputtering method. The anodized titanium enhanced the biocompatibility of the Ti and the bioactivity was improved further by the HA deposited on the anodized Ti. $TiO_2$ layer with $0.2{\sim}0.5{\mu}$ diameter pore size was formed on the Ti surface by anodization. Anodized $TiO_2$ layer analysis HA film deposited, oxide pore size and number decreased compared with non-HA deposited surface. The corrosion resistance of HA deposited/anodized Ti was higher than that of the non-treatment Ti alloy in Hank's solution, indicating better protective effect. From the results of cell culture using MTT assays, the best cell proliferation showed in HA deposited surface after anodization of Ti surfaces compared with another surface treatment.

• Journal of Powder Materials
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• v.29 no.1
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• pp.1-7
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• 2022

This study investigates the effect of process stopping and restarting on the microstructure and local nanoindentation properties of 316L stainless steel manufactured via selective laser melting (SLM). We find that stopping the SLM process midway, exposing the substrate to air having an oxygen concentration of 22% or more for 12 h, and subsequently restarting the process, makes little difference to the density of the restarted area (~ 99.8%) as compared to the previously melted area of the substrate below. While the microstructure and pore distribution near the stop/restart area changes, this modified process does not induce the development of unusual features, such as an inhomogeneous microstructure or irregular pore distribution in the substrate. An analysis of the stiffness and hardness values of the nano-indented steel also reveals very little change at the joint of the stop/restart area. Further, we discuss the possible and effective follow-up actions of stopping and subsequently restarting the SLM process.

• Membrane and Water Treatment
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• v.13 no.3
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• pp.129-137
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• 2022

In this study, the removal of Ciprofloxacin (CPX) from aqueous solutions was investigated by a new activated carbon adsorbent prepared from orange peel (ACOP) with chemical activation using ZnCl₂. The physicochemical properties of orange peel activated carbon were characterized by proximate and ultimate analysis, scanning electron microscopy, BET surface area determination and Fourier transformation infrared spectroscopic studies. According to Brunauer-Emmett-Teller isotherm and non-local-density functional theory, the cumulative surface area, pore volume and pore size of ACOP were determined as 1193 m² g^-1, 0.83 cc g^-1 and 12.7 Å, respectively. The effects of contact time, pH, temperature and ACOP dose on the batch adsorption of CPX were studied. Adsorption equilibrium data of CPX with ACOP were found to be compatible with both the Langmuir and Freundlich isotherms. CPX adsorption capacity of ACOP was calculated as 181.8 mg g^-1 using Langmuir isotherm. The CPX adsorption kinetics were found to be harmonious with the pseudo-second-order kinetic model. Conclusively, ACOP can be assessable as an effective adsorbent for the removal of ciprofloxacin (CPX) from aqueous solutions.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.497-508
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• 2022

Tailings fluidization (i.e., tailings behave as being fluidized) under cyclic loading is one concern during the construction of tailings dams, especially in the shallow tailings layers. The primary goal of this study is to evaluate the responses of tailings under cyclic loadings and the tailings potential for fluidization. A series of cyclic triaxial undrained and drained tests were performed on medium and dense tailings samples under various cyclic stress ratios (CSR). The results indicated that axial strain and excess pore water pressure accumulated over time due to cyclic loading. However, the accumulations were dependent on CSR values, densities, and drainage conditions. The fluidization potential analysis in this study was then evaluated based on the obtained cyclic axial strain and excess pore water pressure. As a result, tailings samples were stable (unfluidized) under small CSR values, and the critical CSR values, where the tailings fluidized, varied depending on the density of tailings samples. Tailings fluidization is triggered as cyclic stress ratios reach critical values. In this study, the critical CSR values were found to be 0.15 and 0.40 for medium and dense samples, respectively.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.53-62
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• 2023

The characteristics of unfrozen water content in frozen soils significantly impact the thermal, hydraulic, and mechanical behavior of the ground. A thorough analysis of the unfrozen water content characteristics of the target subsoil material is crucial for evaluating the stability of frozen ground. This study conducted indoor experiments to measure the freezing point and unfrozen water content of sandy soil while considering pore water salinity. Utilizing the experimental data, we introduced a novel empirical model to conveniently estimate the unfrozen water retention curve. Furthermore, the validity of the unfrozen water retention curve was assessed by comparing the experimental data with the results of a simulation model that utilized the proposed empirical model as input data.

• Journal of the Semiconductor & Display Technology
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• v.23 no.3
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• pp.96-101
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• 2024

In this study, we report on the joining of mullite ceramics using the reaction-bonded aluminum oxide method without applying any external pressure, in consideration of a possible multilayer ceramic substrate in semiconductor back-end process. For this purpose, Al/Al2O3/SiO2/Mullite powder mixture paste was applied to the joining surfaces between two parent mullite bodies of the same composition, and then sintered at 1,650 ℃ for 2 h in air, resulting in a dense and rigid mullite ceramic joints. Phase and microstructural analysis of the joined mullites showed that the reaction bonding by Al oxidation and thereafter mullite formation were completed during the heat treatment process. However, due to the difference in sintering behavior between the parent body and the joining layer, few pore of which size proportional to the joining layer thickness, were observed at some parts of the joining interface. The formation of the pore and its causes was discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.247-254
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• 2006

Online testing method is one of the numerical experiment methods using experimental information for a numerical analysis directly. The method has an advantage in that analysis can be conducted without using an idealized mechanical model, because mechanical properties are updated from element test for a numerical analysis in real time. The online testing method has mainly been used for the geotechnical seismic engineering, whose major target is sand. A testing method that may be applied to a consolidation problem has recently been developed and laboratory and field verifications have been tried. Although related research thus far has mainly used a method to update average reaction for a numerical analysis by positioning an element tests at the center of a consolidation layer, a weakness that accuracy of the analysis can be impaired as the thickness of the consolidation layer becomes more thicker has been pointed out regarding the method. To clarify the effectiveness and possible analysis scope of the online testing method in relation to the consolidation problem, we need to review the results by applying experiment conditions that may completely exclude such a factor. This research reviewed the results of the online consolidation test in terms of reproduction of the consolidation settlement and the dissipation of excess pore water pressure of a clay specimen by comparing the results of an online consolidation test and a separated-type consolidation test carried out under the same conditions. As a result, the online consolidation test reproduced the change of compressibility according effective stress of clay without a huge contradiction. In terms of the dissipation rate of excess pore water pressure, however, the online consolidation test was a little faster. In conclusion, experiment procedure needs to improve in a direction that hydraulic conductivity can be updated in real time so as to more precisely predict the dissipation of excess pore water pressure. Further research or improvement should be carried out with regard to the consolidation settlement after the end of the dissipation of excess pore water pressure.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.467-474
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• 2000

The application of Terzaghi's theory of consolidation for analysing the settlement of multi-layered soils is not strictly valid because the theory involves an assumption that the soil is homogeneous. The settlement of stratified soils with confined aquifer can be analysed using numerical techniques whereby the governing differential equation is replaced by 2-dimensional finite difference approximations. The problems of discontinuous layer interface are very important in the algorithm and programming for the analysis of multi-layered consolidation using a numerical analysis, finite difference method(F.D.M.). Better results can be obtained by the process for discontinuous layer interface, since it can help consolidation analysis to model the actual ground The purpose of this paper provides an efficient computer algorithm based on numerical analysis using finite difference method(F.D.M) which account for multi-layered soils with confined aquifer to determine the degree of consolidation and excess pore pressures relative to time and positions more realistically.