• Korean Journal of Materials Research
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• v.25 no.9
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• pp.480-486
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• 2015

$Pb_{1-x}MoO_4:Er^{3+}/Yb^{3+}$ phosphors with various doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at $900^{\circ}C$ for 16 h, exhibit a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, the $Pb_{0.7}MoO_4:Er_{0.1}Yb_{0.2}$ and $Pb_{0.5}MoO_4:Er_{0.05}Yb_{0.45}$ particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of $Pb_{1-x}MoO_4$ through the incorporation of the $Er^{3+}$ and $Yb^{3+}$ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the $MoO_{4-x}$ group.

• Journal of Digital Convergence
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• v.15 no.6
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• pp.339-344
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• 2017

In this study, microorganisms were isolated from nosocomial environment and are identified by biochemical analysis as the part of biochemical and technical convergence. Microorganisms were collected at intense care unit of general hospital located in Pyeongtak (2014.11.28. - 2014. 11. 30). Using a VITEK2 equipment of biochemical approaches, eleven microorganisms e.g., Micrococcus luteus (or M. lylae), Granulicatella adiacens (M. luteus or M. lylae), Staphylococcus caprae, Sphingomonas paucimobilis, Kocuria kristinae, G elegans, Aerococcus viridans (or Staphylococcus arlettae), Methylobacterium spp., Dermacoccus nishinomiyaensis (or Kytococcus sedentarius), Kocuria kristinae (or M. luteus, M. lylae), Pseudomonas oryzihabitans were identified. And then identified bacteria plates were applied with a plastic stick, so called with "FarmeTok (medistick/Puristic) to produce ClO2. ClO2-releasing plastic stick showed the very strong inhibition of bacterial growth with about 99.9%. There were no bacterial colonies on the ClO2-incubated plate. Taken together, it is suggested that chlorine dioxide should be very strong inhibitor to microorganisms of nosocomial infections.

• Polymer(Korea)
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• v.28 no.2
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• pp.111-120
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• 2004

The interaction between poly(diallyldimethylammonium chloride) (PDADMAC) of positive charge per repeating unit and anionic surfactant, sodium dodecyl sulfate (SDS) has been investigated by light scattering, turbidimetry and fluorescence. Chain behavior of PDADMAC in 0.3 M NaCl aqueous solution seems like neutral polymer chain In good solvent. By adding SDS into PDADMAC solution, strong attractive interaction develops between them, and can be described with two kinds of critical aggregation concentration(CAC). First, at [SDS]/]DADMAC] 0.06, intramolecular critical micellization of SDS occurs inside a single polymer chain. The maximum size of SDS-polymer complex is observed just before intramolecular CAC. Above intramolecular CAC, the size of this complex starts to shrink slowly due to involvement of polymer subchain in micelle. Second, intermolecular CAC is also observed at [SDS]/[DADMAC] 0.5 by means of turbidimetry. Strong aggregation of polymer chains decorated with many micelles occurs after the second CAC, and huge aggregates have formed.

• Journal of Microbiology and Biotechnology
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• v.28 no.8
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• pp.1282-1292
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• 2018

The exopolysaccharide (EPS) produced by Bacillus amyloliquefaciens GSBa-1 was isolated and purified by ethanol precipitation, and DEAE-cellulose and Sepharose CL-6B chromatographies. The molecular mass of the purified EPS was determined to be 54 kDa. Monosaccharide analysis showed that the EPS was composed of predominantly glucose, and it was further confirmed by NMR spectroscopy to be ${\alpha}-glucan$ that consisted of a trisaccharide repeating unit with possible presence of two ${\alpha}-(1{\rightarrow}3)$ and one ${\alpha}-(1{\rightarrow}6)$ glucosidic linkages. Microstructural analysis showed that the EPS appeared as ellipsoid or globose with a smooth surface. The EPS had a degradation temperature at $240^{\circ}C$. Furthermore, the EPS had strong DPPH and hydroxyl radical scavenging activities, and moderate superoxidant anion scavenging and metal ion-chelating activities. This is the first characterization of a glucan produced by B. amyloliquefaciens with strong antioxidant activity. The results of this study suggest the potential of the EPS from B. amyloliquefaciens GSBa-1 to serve as a natural antioxidant for application in functional products.

• The Journal of the Acoustical Society of Korea
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• v.31 no.8
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• pp.523-531
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• 2012

Recently, as a result of increasing concern about eco-friendly power, the demand for the power stations using environmentally friendly powers such as photovoltaic energy, wind force, tidal power, and tidal current has been increasing worldwide. Among these power stations tidal current power plant requires strong current generated by the topographic characteristics of the ocean floor. Uldolmok waterway producing very strong current is an ideal location for a tidal current power generation. However the occurrence of anthropogenic underwater noise generated by the tidal current power station may affect the marine environment. Therefore, it is necessary to evaluate the noise radiated from the station and predict the range influenced by the radiated noise. In this paper, the measurements of radiated noise spectrum level by the tidal current power station are presented, and the source level per unit area is estimated. Finally, the propagation properties of the radiated noise in the Uldolmok waterway is evaluated from the model simulation using the parabolic equation method, RAM.

• BMB Reports
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• v.35 no.2
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• pp.143-154
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• 2002

The structural and functional aspects of ervatamin B were studied in solution. Ervatamin B belongs to the $\alpha+\beta$ class of proteins. The intrinsic fluorescence emission maximum of the enzyme was at 350 nm under neutral conditions, and at 355 nm under denaturing conditions. Between pH 1.0-2.5 the enzyme exists in a partially unfolded state with minimum or no tertiary structure, and no proteolytic activity. At still lower pH, the enzyme regains substantial secondary structure, which is predominantly $\beta$-sheet conformation and shows a strong binding to 8-anilino-1-napthalene-sulfonic acid (ANS). In the presence of salt, the enzyme attains a similar state directly from the native state. Under neutral conditions, the enzyme was stable in urea, while the guanidine hydrochloride (GuHCl) induced equilibrium unfolding was cooperative. The GuHCl induced unfolding transition curves at pH 3.0 and 4.0 were non-coincidental, indicating the presence of intermediates in the unfolding pathway. This was substantiated by strong ANS binding that was observed at low concentrations of GuHCl at both pH 3.0 and 4.0. The urea induced transition curves at pH 3.0 were, however, coincidental, but non-cooperative. This indicates that the different structural units of the enzyme unfold in steps through intermediates. This observation is further supported by two emission maxima in ANS binding assay during urea denaturation. Hence, denaturant induced equilibrium unfolding pathway of ervatamin B, which differs from the acid induced unfolding pathway, is not a simple two-state transition but involves intermediates which probably accumulate at different stages of protein folding and hence adds a new dimension to the unfolding pathway of plant proteases of the papain superfamily.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.85-94
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• 2012

This paper described a centrifuge study in order to investigate ground-underground hollow structure interaction-induced rocking behavior in liquefied ground. Uplift of the underground hollow structures is initiated due to liquefaction in sandy grounds when the ground is exposed to a strong shaking during earthquakes because the apparent unit weight of these structures is smaller than that of the liquefied soil. In order to evaluate the dynamic behavior of the underground hollow structure and the effects of original subsoil during the uplifting, model tests were performed by changing the relative density of the original subsoil and installing an acrylic box as a trench. The results of the present study show that rocking behavior of the underground hollow structure due to shear deformation of the surrounding subsoil or lateral movement from the original subsoil contributed to large magnitude of the uplift due to strong shaking.

• Journal of Adhesion and Interface
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• v.3 no.4
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• pp.44-52
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• 2002

Composite materials are created by combining two or more component to achieve desired properties which could not be obtained with the separate components. The use of reinforcing fillers, which can reduce material costs and improve certain properties, is increasing in thermoplastic polymer composites. Currently, various inorganic fillers such as talc, mica, clay, glass fiber and calcium carbonate are being incorporated into thermoplastic composites. Nevertheless, lignocellulose fibers have drawn attention due to their abundant availability, low cost and renewable nature. In recent, interest has grown in composites made from lignocellulose fiber in thermoplastic polymer matrices, particularly for low cost/high volume applications. In addition to high specific properties, lignocellulose fibers offer a number of benefits for lignocellulose fiber/thermoplastic polymer composites. These include low hardness, which minimize abrasion of the equipment during processing, relatively low density, biodegradability, and low cost on a unit-volume basis. In spite of the advantage mentioned above, the use of lignocellulose fibers in thermoplastic polymer composites has been plagued by difficulties in obtaining good dispersion and strong interfacial adhesion because lignocellulose fiber is hydrophilic and thermoplastic polymer is hydrophobic. The application of lignocellulose fibers as reinforcements in composite materials requires, just as for glass-fiber reinforced composites, a strong adhesion between the fiber and the matrix regardless of whether a traditional polymer matrix, a biodegradable polymer matrix or cement is used. Further this article gives a survey about physical and chemical treatment methods which improve the fiber matrix adhesion, their results and effects on the physical properties of composites. Coupling agents in lignocellulose fiber and polymer composites play a very important role in improving the compatibility and adhesion between polar lignocellulose fiber and non-polar polymeric matrices. In this article, we also review various kinds of coupling agent and interfacial mechanism or phenomena between lignocellulose fiber and thermoplastic polymer.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.605-611
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• 2014

$SrGd_{2-x}(MoO_4)_4:Er^{3+}/Yb^3$ phosphors with doping concentrations of $Er^{3+}$+ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) were successfully synthesized by the cyclic microwave-modified sol-gel method, and their upconversion mechanism and spectroscopic properties have been investigated in detail. Well-crystallized particles showed a fine and homogeneous morphology with grain sizes of $2-5{\mu}m$. Under excitation at 980 nm, $SrGd_{1.7}(MoO_4)_4:Er_{0.1}Yb_{0.2}$ and $SrGd_{1.5}(MoO_4)_4:Er_{0.05}Yb_{0.45}$ particles exhibited a strong 525-nm emission band, a weak 550-nm emission band in the green region, and a very weak 655-nm emission band in the red region. The Raman spectra of the doped particles indicated the domination of strong peaks at higher frequencies of 1023, 1092, and $1325cm^{-1}$ and at lower frequencies of 223, 2932, 365, 428, 538, and $594cm^{-1}$ induced by the incorporation of the $Er^{3+}$+ and $Yb^{3+}$+ elements into the $Gd^{3+}$ site in the crystal lattice, which resulted in the unit cell shrinkage accompanying a new phase formation of the $[MoO_4]^{2-}$ groups.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.51-59
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• 2002

This paper deals with the measurement and analysis of the induced voltages and magnetic fields caused by the operation of home appliances. The induced voltage and magnetic field measurement circuit used in this work consists of the induction coil, the operational preamplifier and the active integrator. Television set and monitors for personal computer cause strong magnetic fields rich in harmonics and high induced voltages by using the switching power suppliers. The strong magnetic field intensity and high induced voltage were created by 14" television set, and their values are 2.1 ［$\mu$Tp-p］and 140 ［mVp-p］at the distance of 0.4 ［m］, respectively. However, the induced voltage per unit magnetic field intensity was created by 17" monitor for personal computer and the measured data was approximately 560［mV/$\mu$T］at the same distance. distance.