• Korean Membrane Journal
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• v.10 no.1
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• pp.13-19
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• 2008

Water softening is a very promising field for membranes and especially ultra low pressure membranes. Nanofiltration membranes based on pore-filling technology was prepared by using a new technique: the in-situ cross-linking. This route involves introducing a pre-formed polymer into the pores of a host membrane and then locking the polymer in the pores by in-situ cross-linking with an appropriate reagent. By this way, it is possible to make robust and competitive, pore-filled, anion-exchange membranes with excellent control over the properties of the incorporated gel without affecting the host membrane. In this paper, the possibilities of tuning such membranes for ultra low pressure water softening was examined by altering pore-filling chemistry (by changing cross-linking and aminating reagents). The results showed that tuning the chemistry of the pore-filling has important effects. In particularly, it had been shown that the correct selection of cross-linking reagent was not only essential to get pore-filled membranes but it could control their properties. Moreover, the aminating reagent could improve membrane performance. It was found that an increase in hydrophobicity could improve the Darcy permeability.

• Journal of Conservation Science
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• v.34 no.2
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• pp.129-135
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• 2018

Scientific investigation of cultural heritage can provide important information to understand the context of the object. To know the characteristics of the material is also an essential part of objects management and conservation. However, the identification and characterization of organic dyes used in archaeological and historical textiles are often limited by the restrictions in sampling. To cope with the difficulties, applications of high-performance techniques of surface analysis, such as Time of Flight-Secondary Ion Mass Spectra (TOF-SIMS) could be considered as a non or micro-destructive option. This study aims to examine the applicability of TOF-SIMS analysis to the detection of organic dyes from historical textiles. A group of silk fabrics dyed with vegetable dyes were artificially photo-aged to different degrees and analyzed with TOF-SIMS. Molecular and fragment ions from indigo were successfully detected from the aged samples; however, only some fragment ions were observed from gardenia and safflower dyed fabrics. Further studies with actual historical samples with extended examination scope would be necessary to assess the validity of this technique.

• Environmental Engineering Research
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• v.11 no.4
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• pp.173-180
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• 2006

Autotrophic nitrogen removal and its microbial community from a laboratory scale upflow anaerobic sludge bed reactor were characterized with dynamic behavior of nitrogen removal and sequencing result of molecular technique (DNA extraction, PCR and amplification of 16S rDNA), respectively. In the experiment treating inorganic wastewater, the anaerobic granular sludge from a full-scale UASB reactor treating industrial wastewater was inoculated as seed biomass. The operating results revealed that an addition of hydroxylamine would result in lithoautotrophic ammonium oxidation to nitrite/nitrate, and also hydrazine would play an important role for the success of sustainable nitrogen removal process. Total N and ammonium removal of 48% and 92% was observed, corresponding to nitrogen conversion of 0.023 g N/L-d. The reddish brown-colored granular sludge with a diameter of $1{\sim}2\;mm$ was observed at the lower part of sludge bed. The microbial characterization suggests that an anoxic ammonium oxidizer and an anoxic denitrifying autotrophic nitrifier contribute mainly to the nitrogen removal in the reactor. The results revealed the feasibility on development of high performance lithoautotrophic nitrogen removal process with its microbial granulation.

• Journal of Microbiology and Biotechnology
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• v.30 no.11
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• pp.1739-1749
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• 2020

Exopolysaccharide produced by the yeast Papiliotrema flavescens, isolated from wine grape berries of Champagne vineyard, was investigated for both chemical and functional characterization. SECMALLS and colorimetric assay analyses showed that the EPS is a high M_W heteropolymer (2.37 × 10⁶ g/mol) majorily consisting of mannose, glucose, xylose and glucuronic acid as monosaccharide constituents, with two substituents (sulphate and phosphate groups), and a minor protein moiety. Structural enchainment of these carbohydrates based on methylation, GC-MS and NMR analyses revealed a linear main backbone built up of α-(1 → 3)-D-mannopyranosyl residues on which are branched side chains consisting of a single β-D-glucopyranosyluronic acid residue and β-(1 → 2)-xylopyranoses (2-5 residues). Suggestion of some xylopyranose side chains containing a mannose residue at the nonreducing terminal end was also proposed. This is first report on EPSs from the grape P. flavescens yeast with such structural characteristics. Furthermore, investigations for valuating the application performance of these EPS in relation with their structural features were carried out in 8% alcohol experiment solutions. Very exceptional viscosifying and foaming properties were reported by comparison with commercial biopolymers such as Arabic, gellan and xanthan gums. The intrinsic properties of the natural biopolymer from this wild grape-associated P. flavescens yeast make it a potential candidate for use in various biotechnology applications.

• Environmental Engineering Research
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• v.24 no.4
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• pp.566-571
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• 2019

One-pot hydrothermal route was adopted to synthesize Al:BiVO₄, at 4 h and 8 h reaction durations, by adding 1% aluminiumoxide powder (w/v) to the precursors. The products were investigated using several characterization techniques that conform a significant morphological change and a decrease in bandgap energy of the materials upon Al modification of scheelite monoclinic bismuth vanadate matrix at both hydrothermal durations. Antibacterial experiments were performed against methicillin-resistant Staphylococcus aureus in visible light condition to harness the photoxidation property of Al-doped BiVO₄ and compare to that of unaltered BiVO₄. Minimum inhibitory concentration of the synthesized materials was identified. The results indicate that Al-doping on BiVO₄ has a significant effect on its photocatalytic antibacterial performance. Al:BiVO₄ synthesized at 8 h hydrothermal treatment parades excellent sunlight-driven photocatalysis compared to the one synthesized at 4 h.

• Composites Research
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• v.28 no.6
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• pp.402-407
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• 2015

It is well known that the polymer matrix composite materials have good specific strength, making them appropriate for use in transport vehicle. Since the property of composite materials can be obtained only after manufacturing parts, the property depends on greatly on the fabrication process, which is different from metallic system. Therefore, in order to use composite materials for aircraft, the certifying agency requires a robust database with extensive tests and proof of the process unlike metals. Recently developed material qualification methodology by NCAMP (National Center for Advanced Materials Performance) has been accepted by FAA and EASA and can be applied to type certificate reducing time and cost of developing a composite materials database for aircraft application. This paper summarizes a study to establish the composite materials database to apply the NCAMP methodology to composite materials characterization for composite aircraft and to provide the effective materials database through Aerospace Composite Materials Data Center to be approved by Korea Civil Aviation Certification Agency.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.473-479
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• 2018

Highly toxic gases such as hydrogen sulfide ($H_2S$), carbon dioxide ($CO_2$), and ammonia ($NH_3$) are generated by both nature and human activities and affect human health. In this research, activated carbon combined with $Ca(OH)_2$ and $CaCO_3$ (AC-CO and AC-CC, respectively) were fabricated and applied in absorbing toxic gases from air pollutants. Activated charcoal powder was compressed in the form of pellets and used in the designated conditions. The optimum operating conditions and material properties, such as adsorption capacity, effect of weight ratio of the mixture, and hardness, have been investigated after combining with the calcium derivative. The good performance exhibited in this study suggests that this material is expected to be an effective and economically viable adsorbent for $NH_3$, $CO_2$, and $H_2S$ removal from the air system.

• Journal of the Korean Society of Safety
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• v.26 no.6
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.693-700
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• 2016

Analyzing characteristics of spam text messages had limitations since spam datasets are typically difficult to obtain publicly and previous studies focused on spam email. Although existing studies, such as through the use of spam e-mail characterization and utilization of data mining techniques, there are limitations that influence is limited to high spam detection techniques using a single word character. In this paper, we reveal the characteristics of the spam SMS based on experiment and analysis from different perspectives and propose coward analysis based spam SMS detection scheme with a publicly disclosed spam SMS from the University of Singapore. With the extensive performance evaluations, we show false positive and false negative of the proposed method is less than 2%.