• Particle and aerosol research
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• v.18 no.1
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• pp.9-21
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• 2022

In this study, a novel antiviral coating method for the air filtration system of subway station was investigated. Using dry aerosol coating process, we developed a high-performance antiviral air filter with spark discharger and carbon brush type ionizer. Silver nanoparticles were produced by a spark discharge generation system with ion injection system and were used as antiviral agents coated onto a medium grade air filter. The pressure drop, filtration efficiency, and antiviral ability of the filter against aerosolized MS2 virus particles as a surrogate of SARS-CoV-2 virus were tested with dust contamination. Dust contamination caused the increase of the filtration efficiency and pressure drop, while the antiviral agents (in this study, silver nanoparticles) coating did not have any significant effect on the filtration efficiency and pressure drop. Using these properties, we suggested a novel method to maximize the antiviral performance of the antiviral air filter that was contaminated by dust particles. Moreover theoretical analysis of antiviral ability with dust contamination and re-coated antiviral agents was carried out using a mathematical model to calculate the time-dependent antiviral effect of the filter under actual conditions of subway station. Our model can be used to apply on antiviral air filtration system of subway station for prevention of pandemic diffusion, and predict the life cycle of an antiviral filter.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.394-404
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• 2022

This study was conducted to optimize the amount of drip irrigation for Prunus×yedoensis Matsum., one of the major medium-sized landscaping trees used mainly for streetscapes and as ornamentals. The experiment was conducted in a container nursery, where we assessed the growth and physiological characteristics of 4- and 8-year-old seedlings watered at different rates (x) by a drip irrigation system. The relative growth rates (based on height and root collar diameter (RCD) measurements) were highest at 288 and 416 L/year/tree for the 4- and 8-year-old containerized seedlings, respectively. These age and treatment combinations also produced significantly different dry weight and seedling quality index values, indicating good growth. The two age groups had significantly different total root lengths, root diameters, and root volumes under these respective irrigation treatments. In addition, the 4-year-old containerized seedlings irrigated at 288 L/year/tree and the 8-year-old containerized seedlings irrigated at 416 L/year/tree had the highest activations in their chlorophyll contents. Overall, the results (differences in irrigation amounts affect the seedlings morphological relative growth, biomass growth, seedling quality, and physiological reaction) indicate that the optimal irrigation amounts for container-grown Prunus×yedoensis are 288 L/year/tree for 4-year-old (RCD class, 3cm) and 416 L/year/tree for 8-year-old (RCD class, 7 cm) containerized seedlings.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.307-312
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• 2023

In this study, a catalytic oxidation-heat recovery system was designed that can remove unreacted with a concentration of about 1% to 6% in the exhaust gas of hydrogen fuel cells and recover heat to ensure safety in the hydrogen economy. The safety system was devised by filling hydrogen oxidation catalysts at room temperature that can remove unreacted hydrogen without any energy source, and an exhaust-heat recovery device was integrated to efficiently recover the heat released from the oxidation reaction. Through CFD analysis, variations in pressure and fluid within the system were shown depending on the filling conditions of the hydrogen oxidation system. In addition, it was found that waste heat could be recovered by optimizing the temperature of the exhaust gas, flow rate, and pressure conditions within the heat recovery system and securing hot water above 40 ℃ by utilizing the exhaust gas oxidation heat source above 300 ℃. Through this study, it was possible to confirm the potential of utilizing hydrogen processes, which are applied in small to medium-sized systems such as hydrogen fuel cells, as a safety system by evaluating them at a pilot scale. Additionally, it could be a safety guideline for responding to unexpected hydrogen safety accidents through further pilot-scale studies.

• Journal of Life Science
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• v.33 no.6
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• pp.506-511
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• 2023

The purposes of this study were to isolate and characterize lactic acid bacteria with antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) from fermented food and to confirm the antibacterial activities of fermented rice products using the isolated lactic acid bacterium. Three bacteria, namely, Weissella sp. ISF-1, ISF-2, and ISF-3, were selected from fermented squid based on the 16S rRNA gene sequence. All three strains grew well in an MRS medium containing 5% (w/v) NaCl and showed antibacterial activity against Bacillus cereus, Staphylococcus aureus, and MRSA. Their growth was excellent at 0% ~ 5% (w/v) NaCl and relatively good up to 7% (w/v) NaCl. The initial pH of 8 was optimal for their growth, and good growth was also observed at pH 6, 7, and 9. The lyophilisates of the fermented rice using Weissella sp. ISF-1 showed antibacterial activities against B. cereus, S. aureus, and MRSA. We inferred that isolated lactic acid bacteria could be useful in the development of probiotics and biopreservatives for foods and in the treatment of MRSA and may increase the value of rice products.

• Korean Journal of Environmental Agriculture
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• v.42 no.4
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• pp.259-268
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• 2023

Rhodococcus sp. 3-2 strain has been reported to degrade benzimidazole-based pesticides, such as benomyl and carbendazim. Therefore, this study aimed to optimize culture medium composition and culture conditions to achieve cost-effective and efficient large-scale production of the Rhodococcus sp. 3-2 strain. The study identified that the optimal media composition for mass culture comprised 0.5% glucose, 0.5% yeast extract, 0.15% NaCl, 0.5% K₂HPO₄, 0.5% sodium succinate, and 0.1% MgSO₄. Additionally, a microbial agent was developed using a 1.5-ton fermenter, with skim milk (20%), monosodium glutamate (15%), and vitamin C (2%) as key components. The storage stability of the microbial agent has been confirmed, with advantages of low temperature conservation, which helps to sustain efficacy for at least six months. We also assessed the benomyl degradation activity of the microbial agent within field soil. The results revealed an over 90% degradation rate when the concentration of viable cells exceeded 2.65 × 10⁶ CFU/g after a minimum of five weeks had elapsed. Based on these findings, Rhodococcus sp. 3-2 strain can be considered a cost-effective microbial agent with diverse agricultural applications.

• Journal of Mushroom
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• v.21 no.4
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• pp.261-265
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• 2023

We aimed to develop outstanding domestic varieties suitable for both columnar and cylindrical-shape substrates, aiming to replace foreign varieties. and bred a high-quality new strain named 'Charmjon', using genetic resources collected from Japan and China. The optimal cultivation temperature for Charmjon's mycelial growth was found to be 25℃, and its mycelial growth at 15℃ and 25℃ was superior to the control variety. In terms of mycelial growth characteristics based on the substrate, Charmjon exhibited excellent mycelial strength on PDA medium compared to the control variety. Through columnar and cylindrical-shape substrates cultivation, we assessed the quantity and morphological characteristics of the fruiting bodies. The results confirmed that Charmjon can be produced stably using both cultivation methods, and it showed higher yields and individual weights than the control variety. In addition, the color of the pileus was notably darker, and the shape of the pileus varied depending on the cultivation method. The test of genetic diversity revealed that Charmjon has distinct genetic characteristics compared to the control varieties.

• The Korean Journal of Pesticide Science
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• v.14 no.2
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• pp.148-156
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• 2010

S59-4 isolate was evaluated as a potential biocontrol agent using in vivo wounded garlic bulb assay. When the spore suspension ($10^5$ spores/$m\ell$) of Penicillium hirsutum was co-inoculated with cell suspension of S59-4 isolate on wounded garlics, the isolate showed high suppressive effect to disease development. The isolate was identified as Pantoea agglomerans S59-4(Pa59-4) through Biolog system. Furthermore, soaking garlic bulbs in the suspension of Pa59-4 significantly reduced garlic decay caused by P. hirsutum. The optimal concentration of Pa59-4 for controlling garlic blue mold was $10^7\sim10^8$ cfu/$m\ell$. And suppressive effect of Pa59-4 on garlic storage decay reduced as inoculation concentration of Penicillium hirsutum increased. In addition in order to investigate population dynamics of Pa59-4 on application site of garlic cloves, two antibiotic markers, pimaricin and vancomycin were selected. Bacterial density of Pa59-4 on the wounded garlic cloves increased continuously both under room temperature condition and low temperature condition until 30days after application of Pa59-4, meanwhile that of Pa59-4 on intact garlic cloves increased until 15days after application of Pa59-4 and thereafter decreased continuously. Two culture media for mass-production of Pa59-4, LB medium and TSB medium, were selected. By-product of bio-fungicide formulated by mixing white carbon and bacterial suspension of Pa59-4 suppressed by 40 to 50% garlic blue mold. Above results suggest that Pa59-4 be a promising control agent against garlic blue mold.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1086-1091
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• 1999

$K^+-{\beta}/{\beta}"-Al_2O_3$ in the ternary system $K_2O-MgO-Al_2O_3$ was directly synthesized by solid state reaction. The phase formation and phase relation were carefully investigated in relation to starting composition, calcining temperature and time, and dispersion medium. The optimal synthetic condition was also examined for the formation of ${\beta}"-Al_2O_3$ phase with a maximum fraction. As a composition range, the mole ratio of $K_2O$ to $Al_2O_3$ was changed from 1:5 to 1:6.2 and the amount of MgO used as a stabilizer was varied from 4.2 wt % to 6.3 wt %. The calcining temperature was selected between $1000^{\circ}C$ and $1500^{\circ}C$. At $1000^{\circ}C$, the ${\beta}/{\beta}"-Al_2O_3$ phases began to form resulted from the combining of ${\alpha}-Al_2O_3$ and $KAlO_2$ and increased with temperature rising. All of ${\alpha}-Al_2O_3$ phase disappeared to be homogenized to the ${\beta}/{\beta}"-Al_2O_3$ phase at $1200^{\circ}C$. Near the temperature at $1300^{\circ}C$, the fraction of ${\beta}"-Al_2O_3$ phase showed a maximum value with the composition of $K_{1.67}Mg_{0.67}Al_{10.33}O_{17}$. At temperatures above $1300^{\circ}C$, the fraction of ${\beta}"-Al_2O_3$ phase decreased gradually owing to $K_2O$ loss caused by a high potassium vapor pressure, and the appropriate calcining time was about 5 hours. Acetone was more effective than distilled water as a dispersion medium for milling and mixing.

• Journal of Embryo Transfer
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• v.22 no.3
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• pp.155-160
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• 2007

During in vitro culture of mammalian oocytes and embryos, the cells are exposed to the risks that cause cell injury or death. Numerous studies have been reported that the cell injury may be induced by the action of free radicals generated by auto-oxidation. This study was undertaken to investigate the optimal culture condition system for in vitro culture of porcine embryos. We first evaluated the effect of culture media on the porcine embryo development. NCSU-23 and PZM-5, culture medium tested, were failed to produce significant difference on the rate of blastocyst formation. In NCSU-23, the developmental rate was slightly higher than that in PZM-5. During in vitro maturation (IVM), fertilizaton (IVF), and culture (IVC) under 5 or 20% oxygen ($O_2$), the rates of cleavage and development were insignificantly different from each other under our culture condition (20% $O_2$, in NCSU-23), the mean cell number per blastocyst was $40{\pm}10$. These results showed that medium and $O_2$ concentration had no significant effect on the development of porcine embryos.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.543-560
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• 2018

With the increased development in downtown underground space facilities that vertically cross under a railway at a shallow depth, the demand for non-open cut method is increasing. However, most construction sites still adopt the pipe roof method, where medium and large diameter steel pipes are pressed in to form a roof, enabling excavation of the inside space. Among the many factors that influence the loosening region and loads that occur while pressing in steel pipes, the size of the pipe has the largest impact, and this factor may correspond to the magnitude of load applied to the underground structure inside the steel pipe roof. The super equilibrium method (SEM) has been developed to minimize ground disturbance and loosening load, and uses small diameter pipes of approximately 114 mm instead of conventional medium and large diameter pipes. This small diameter steel pipe is called an SEM pile. After SEM piles are pressed in and the grouting reinforcement is constructed, a crossing structure is pressed in by using a hydraulic jack without ground subsidence or heaving. The SEM pile, which plays the role of timbering, is a fore-poling pile of approximately 5 m length that prevents ground collapse and supports surface load during excavation of toe part. The loosening region should be adequately calculated to estimate the spacing and construction length of the piles and stiffness of members. In this paper, we conducted a comparative analysis of calculations of loosening load that occurs during the press-in of SEM pile to obtain an optimal design of SEM. We analyzed the influence of factors in main theoretical and empirical formulas applied for calculating loosening regions, and carried out FEM analysis to see an appropriate loosening load to the SEM pile. In order to estimate the soil loosening caused by actual SEM-pile indentation and excavation, a steel pipe indentation reduction model test was conducted. Soil subsidence and soil loosening were investigated quantitatively according to soil/steel pipe (H/D).