• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.127-138
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• 2016

Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

• The Korean Journal of Mycology
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• v.48 no.1
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• pp.15-27
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• 2020

In screening for antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) KCCM 40510 and Bacillus cereus KCTC 3624, NNIBRFG5039 was isolated from the air in Sangju-si, Gyeongsangbuk-do. Based on a high sequence similarity of the internal transcribed spacer (ITS) region, NNIBRFG5039 was determined to be closely related to Penicillium rubefaciens CBS 139145. The optimal media, initial pH, and temperature for mycelial growth and antimicrobial activity of P. rubefaciens NNIBRFG5039 were determined as follows: potato dextrose broth (PDB), pH 6.5, and 30℃, respectively. Under the optimal culture conditions, maximum mycelial growth (12.4 g L^-1) and antibacterial activity (7.5 mm zone of inhibition against MRSA KCCM 40510, and 5.0 mm zone of inhibition against B. cereus KCTC 3624) were observed in a 5 L stirred-tank fermenter. We also isolated the antimicrobial compound from an ethyl acetate fraction, and its chemical structure was identified as (S)-6-hydroxymellein (1) by ESI-MS, ¹H-NMR, and ¹³C-NMR. Consequently, the extract from P. rubefaciens NNIBRFG5039 may be used in functional materials for antimicrobial-related applications.

• Polymer(Korea)
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• v.25 no.1
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• pp.78-89
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• 2001

Morphological changes of unsaturated polyester/polyvinylacetate semi-IPN were studied while the phase separation and the cure reaction occurred in a competing fashion. The light scattering and thermal analysis techniques were used to investigate the phase separation rates and mechanical properties resultantly induced by molecular diffusion of thermoplastic polymer during the curing process of thermosetting polymer. The reaction activation energy was calculated by using Flynn-Wall method and the semi-IPN structure exhibited various phase-separation morphological characteristics. When PVAc composition was 10 wt%, the phase separation was not observed during the curing reaction, but the phase separation occurred in a similar fashion to nucleation and growth(NG) mechanism at room temperature. On the other hand, when PVAc composition was over 11.65 wt%, the phase separation was generated in the middle of the curing process. Consequently, the phase separation seemed to influence the curing reaction rate, which was also supported by the changing activation energy with conversion and PVAc composition. Finally, the total scattered intensity was measured at various temperature, and subsequently the diffusion rates of phase separation R(${\beta}m$) were evaluated.

• Membrane Journal
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• v.28 no.4
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• pp.252-259
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• 2018

An acidic, real metal-plating wastewater was treated by a fluidized bed membrane reactor introduced with granular activated carbon (GAC) as fluidized media. With GAC fluidization, there was no increase in suction pressure with time at each flux set-point applied. At neutral solution pH, much less fouling rate was observed than acidic pH under GAC fluidization. Higher solution pH resulted in the increase in particle size in metal-finishing wastewater, thus producing a less dense cake structure on membrane. More than 95% of chemical oxygen demand was observed from the fluidized bed membrane reactor under GAC fluidization. Total suspended solid concentration in membrane permeate was near zero. At the raw wastewater pH, no removal of copper and chromium by the fluidized bed membrane reactor was observed. As the pH was increased to 7.0, removal efficiency of copper and chromium was increased considerably to 99 and 94%, respectively. Regardless of solution pH tested, more than 95% of cyanide was removed possibly due to the strong adsorption of organic-cyanide complex on GAC in fluidized bed membrane reactor.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.97-106
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• 2009

It is known that the natural amethyst is changed to citrine after heat treatment. However, when all amethyst samples from Zambia were heat-treated in the temperature range of $350{\sim}380^{\circ}C$ for 1 hour, the result was that five out of eight samples were changed to citrine and all the rest of samples became rock crystal quartz. These differences in the color appearance seem to be influenced by the original colors contained in the amethyst before the heat treatment. The amethyst containing yellow color changed to citrine and the amethyst without containing yellow color changed to rock crystal quartz after the heat treatment. The results compared after the instrumental analysis on the difference of color change, it showed the differences of peak intensity in 3,400 $cm^{-1}$ and the existence and non-existence of peak at the range of 5,200${\sim}$5,400 $cm^{-1}$ in FTIR. It revealed the difference in the quantity of Cr which is a trace element in the WD-XRF analysis. The identical result in the FTIR spectra before and after the heat treatment reveals that the heat treatment did not cause any change in the main composing elements or crystal structure.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.131-139
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• 2016

Detailed knowledge on maskelynite, a glassy phase of plagioclase found in shocked meteorites and impact craters, is essential to understand a shock metamorphism. Here, we explore an inhomogeneous shock metamorphism in the lunar meteorite Mount DeWitt (DEW) 12007 with an aim to understand the formation mechanism of maskelynite. Most plagioclase grains in the DEW 12007 partially amorphized into maskelynite with a unidirectional orientation. Back-scattered electron (BSE) images of maskelynite show a remnant of planar deformation fracture possibly indicating that the maskelynite would be formed by solid-state transformation(i.e., diaplectic glass). Plagioclase with flow texture is also observed along the rim of maskelynite, which would be a result of recrystallization of melted plagioclase. Results of Raman experiments suggest that shock pressure for plagioclase and maskelynite in the DEW 12007 is approximately 5-32 GPa and 26-45 GPa, respectively. The difference in shock pressures between plagioclase and maskelynite can be originated from 1) external factors such as inhomogeneous shock pressure and/or 2) internal factors such as chemical composition and porosity of rock. Unfortunately, Raman spectroscopy has a limitation in revealing the detailed atomic structure of maskelynite such as development of six- or five-coordinated aluminum atom upon various shock pressure. Further studies using nuclear magnetic resonance spectroscopy are necessary to understand the formation mechanism of maskelynite under high pressure.

• KSBB Journal
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• v.24 no.5
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• pp.432-438
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• 2009

Here, we demonstrated simple nucleic acid, RNA, concentration method using polymer micro chip containing glass bead ($100\;{\mu}m$). Polymer micro chip was fabricated by PDMS ($1.5\;cm\;{\times}\;1.5\;cm$, $100\;{\mu}m$ in the height) including pillar structure ($160\;{\mu}m\;(I)\;{\times}\;80\;{\mu}m\;(w)\;{\times}\;100\;{\mu}m\;(h)$, gap size $50\;{\mu}m$) for blocking micro bead. RNA could be adsorbed on micro glass bead at low pH by hydrogen bonding whereas RNA was released at high pH by electrostatic force between silica surface and RNA. Amount of glass beads and flow rate were optimized in aspects of adsorption and desorption of RNA. Adsorption and desorption rate was measured with real time PCR. This concentrated RNA was applied to amplification micro chip in which NASBA (Nucleic Acid Sequence Based Amplification) was performed. As a result, E.coli O157 : H7 in the concentration of 10 c.f.u./10 mL was successfully detected by these serial processes (concentration and amplification) with polymer micro chips. It implies this simple concentration method using polymer micro chip can be directly applied to ultra sensitive method to measure viable bacteria and virus in clinical samples as well as environmental samples.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4660-4665
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• 2011

New precursors as a Li adsorbent, $Li_{1.6}(MnM)_{1.6}O_4$ (M=Cu, Ni, Co, Fe), were synthesized by hydrothermal method and their physicochemical properties were discussed. XRD and HRTEM results revealed that the original spinel structure was stabilized by cobalt-doping while Cu-, Ni- and Fe-doping led to structural changes. Such a structural stabilization by Cobalt-doping was maintained after lithium leaching by acid treatment. Li absorption efficiency from seawater was significantly enhanced by using the Cobalt-doped spinel manganese oxide, $Li_{1.6}[MnCo]_{1.6}O_4$, compared to the commercially available $Li_{1.33}Mn_{1.67}O_4$; the adsorbed amount of Li from 1g-adsorbent was 35 and 16 mg by $Li_{1.6}[MnCo]_{1.6}O_4$, and $Li_{1.33}Mn_{1.67}O_4$, respectively.

• Journal of the Korean association of regional geographers
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• v.5 no.1
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• pp.121-135
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• 1999

This study investigated the location conditions, spatial linkage structures, and firm specific problems of small firms of the Greater Cincinnati metropolitan area by sectors and by areal distribution. The major locational advantages were closeness to customers and suppliers followed by accessibility to inter-state highways. These results were supported by spatial linkage structures in which within-region linkages occupied a greater portions of linkage, showing the importance of small firms in the regional economy. The linkage patterns showed distance decay effect with high elasticity. While there were no significant differences of locational conditions and spatial linkage structures of small firms between core and peripheral area, a slight difference was identified among sectors. Chemical related manufacturing firms show different locational conditions and spatial linkage structure with weak within-local linkages. The main locational disadvantages were lack of qualified labor, undesirable neighborhood, heavy tax, and space shortage. Considering the biggest problems such as lack of qualified labor, difficulties in sales/marketing, low accessibility to financial resource, and technological inability, the inter-related cooperative business networks among firms and regional institutions, consulting companies, chamber of commerce, and universities are needed to stimulate regional economic development and survival of small firms.

• Journal of Conservation Science
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• v.27 no.4
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• pp.395-401
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• 2011

After pressurized impregnation treatment, which has been proposed as an effective conservation method for stone cultural property, was executed with methyl metacrylate (MMA), MMA-butyl acrylate (PMB73) mixture and MMA-vinyl trimethoxy silane (PMV5) co-monomer mixture, the physical-chemical properties on the sand stone and the granite impregnated were evaluated. Compared to the case of granite, the impregnation ratios of sand stone showed larger values in the range of 3.2 to 3.7 wt% and these were increased up to 32% when the decompression process was applied to autoclave. The physical properties of sand stone such as anti-moisture property, flexural strength, impact property and ultrasonic velocity were also higher values than those of granite, which can be interpreted by high impregnation ratio resulted in many void within sand stone. The impact failure energy was 1.22 J for PMMA, 1.84 J for PMB73, and 2.8 J for PMV5, respectively. Since the inorganic affinity of treatment agent is more effective than the molecular structure of acrylic agent, PMV5 improved inorganic property indicates the optimum impact property.