• Journal of Microbiology and Biotechnology
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• 제8권1호
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• pp.53-60
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• 1998

This study examines the effect of pH, temperature, metal ion concentration and culture density on metal biosorption by the nuisance cyanobacterium Microcystis aeruginosa. Ni biosorption was higher at pH 9.2 than at neutral and acidic pH. In contrast the biosorption of Cu and Zn was maximum at pH 7.0. However, biosorption of Zn was difficult to measure at pH values 9.2 and 10.5, owing to the formation of insoluble complexes. All the test metals (Cu, Zn, and Ni) showed maximum biosorption rate at low culture densities of 40 mg dry wt $1^{-1}$. The biosorption of Cu, Zn, and Ni was maximum at $40^{\circ}C$. However, no worthwhile difference in Zn and Ni sorption was noticed at 4 and $29^{\circ}C$ as compared to $40^{\circ}C$. Of these three metals used Microcystis showed a greater binding capacity ($K_{f}$ value=0.84, Freundlich adsorbent capacity) and accelerated biosorption rate for Cu under various environmental conditions. Fitness of mathematical models on metal biosorption by Microcystis confirmed that the biological materials behave in the same way as physical materials. These results suggest that before using a biosorbent for metal recovery, the environmental requirements of the biosorbent must be ascertained.

• 대한기계학회논문집B
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• 제27권4호
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• pp.447-457
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• 2003

An experiment in a turbulent non-premixed flat flame was carried out in order to investigate the effect of swirl number on the flow and combustion characteristics. First. stream lines and velocity distribution in the flow field were obtained using PIV method. In contrast with the axial flow without swirl, highly swirled air induced stream lines along the burner tile. and backward flow was caused by recirculation in the center zone of the flow field. In the combustion. the flame with swirled air also became flat and stable along the burner tile with increment of the swirl number. Flame structure by measuring OH and CH radicals intensity and by calculating Damkohler number(Da) and turbulence Reynolds number(Re$_{T}$) was examined. It appeared to be comprised in the wrinkled laminar-flame regime. Backward flow by recirculation of the burned gas decreased the flame temperature and emissions concentrations as NO and CO. Consequently, the stable flat flame with low NO concentration was achieved.d.

• 센서학회지
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• 제25권3호
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• pp.218-222
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• 2016

Pure and V-doped NiO porous structures were prepared by the evaporation-induced surfactant assembly and subsequent pyrolysis of assembled structures, and their gas sensing characteristics were investigated. Pure NiO porous structures showed negligible gas responses (S=$R_g/R_a$, $R_g$: sensor resistance in analytic gas; $R_a$: sensor resistance in air) to 5 ppm trimethylamine (S=1.17) as well as other interfering gases such as ethanol, p-xylene, toluene, benzene and formaldehyde (S=1.02-1.13). In contrast, the V-doped NiO porous structures exhibited a high response and selectivity to 5 ppm trimethylamine (S=14.5) with low cross-responses to other interfering gases (S=4.0-8.7) at $350^{\circ}C$. The high gas response of V-doped NiO porous structures to trimethylamine was explained by electronic sensitization, that is, the increase in the chemoresistive variation due to the decrease in the hole concentration. The enhanced selectivity to trimethylamine was discussed in relation to the interaction between basic trimethylamine gas and acidic V catalysts.

• 한국식품영양학회지
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• 제27권5호
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• pp.914-920
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• 2014

This study was conducted on children from 10 community children centers located in northern Seoul. The quality factors of the food services of the community children centers were divided into five factors, including sanitation, food, environment, subsidiary service and staff. Analysis of the differences in the importance of factors and satisfaction with the food service quality indicated satisfaction to be higher than importance for in all the factors except 'environment'. In particular, of the food service qualities, significant differences were found between importance and satisfaction in relation to the attributes of 'food' and 'environment'. As a result of IPA of the food service qualities in community children centers, 'sanitation' was found to be in the maintenance area, 'environment' to be in the area of concentration, and the quality attributes of 'staff' and 'subsidiary service' were found to be in the low priority area. In contrast, the 'food' quality corresponded to the area of oversupply.

• Journal of Microbiology and Biotechnology
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• 제26권2호
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• pp.373-384
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• 2016

The membrane-aerated biofilm reactor (MABR) is a promising municipal wastewater treatment process. In this study, two cross-flow MABRs were constructed to explore the carbon and nitrogen removal performance and bacterial succession, along with changes of influent loading shock comprising flow velocity, COD, and NH₄-N concentrations. Redundancy analysis revealed that the function of high flow velocity was mainly embodied in facilitating contaminants diffusion and biosorption rather than the success of overall bacterial populations (p > 0.05). In contrast, the influent NH₄-N concentration contributed most to the variance of reactor efficiency and community structure (p < 0.05). Pyrosequencing results showed that Anaerolineae, and Beta- and Alphaproteobacteria were the dominant groups in biofilms for COD and NH₄-N removal. Among the identified genera, Nitrosomonas and Nitrospira were the main nitrifiers, and Hyphomicrobium, Hydrogenophaga, and Rhodobacter were the key denitrifiers. Meanwhile, principal component analysis indicated that bacterial shift in MABR was probably the combination of stochastic and deterministic processes.

• 한국응용과학기술학회지
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• 제33권4호
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• pp.788-794
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• 2016

Vinca alkaloids from plant Vinca minor have been investigated for their effects of tyrosinase inhibition, stimulation of ROS generation and increasement of cell migration activity. The methanolic crude extract and the water-soluble fraction exhibited $IC_{50}$ value of 3.1 mg/mL and 2.1 mg/mL. Vinca minor extract treatment significantly increased ROS levels in HaCaT cells, in a concentration-dependent manner. Treatments of Vinca minor extract led to increase wound closure when compared with non-treatment. Low dose (0.1% or 0.3%) of extracts have not significantly affected, compared with that in controls. By contrast, 0.5% extract have dramatic effect on wound healing activity of keratinocytes. Effects of Vinca minor extract in a filter-based cell mobility assay appear similar to that of wound closure assay, which suggests that the Vinca minor extract have wound healing effects on skin.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• Journal of Microbiology and Biotechnology
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• 제23권1호
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• pp.99-105
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• 2013

In this study, nitrous oxide ($N_2O$) emission was compared between the operations of two different sequencing batch reactors, conventional sequencing batch reactor (CNVSBR) and simultaneous nitrification and denitrification sequencing batch reactor (SND-SBR), using synthetic wastewater. The CNV-SBR consisted of anoxic (denitrification) and aerobic phases, whereas the SND-SBR consisted of a microaerobic (low dissolved oxygen concentration) phase, which was achieved by intermittent aeration for simultaneous nitrification and denitrification. The CNV-SBR emitted 3.9 mg of $N_2O$-N in the denitrification phase and 1.6 mg of $N_2O$-N in the nitrification phase, resulting in a total emission of 5.5mg from 432mg of $NH_4^+$-N input. In contrast, the SND-SBR emitted 26.2mg of $N_2O$-N under the microaerobic condition, which was about 5 times higher than the emission obtained with the CNV-SBR at the same $NH_4^+$-N input. From the $N_2O$ yield based on $NH_4^+$-N input, the microaerobic condition produced the highest yield (6.1%), followed by the anoxic (0.9%) and aerobic (0.4%) conditions. It is thought that an appropriate dissolved oxygen level is critical for reducing $N_2O$ emission during nitrification and denitrification at wastewater treatment plants.

• 한국농공학회논문집
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• 제63권3호
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• pp.35-45
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• 2021

Digestate or slurry produced from anaerobic digestion is mostly applied to crop lands for its disposal and recovering nutrients. However, minimizing nitrogen losses following field application of the digestate is important for maximizing the plant's nitrogen uptake and reducing environmental concerns. This study was conducted to assess the effects of three different biogas digestate application techniques (sawdust mixed with digestate (SSD), the hole application method (HA), and digestate injected in the soil (SD)) on nitrate leaching potential in the soil. A pot laboratory experiment was conducted at room temperature of 25 ± 2 ℃ for 107 days. The experimental results showed that sawdust application method turned out to be appropriate for quick immobilization of surplus N in the form of microbial biomass N, reflecting its lower total nitrogen and NH₄-N contents and low pH. The NH₄-N and total nitrogen fate in the soil fertilized with manure showed no statistically significant (p > 0.05) differences between the different methods applied during the incubation time under room temperature. In contrast, NO₃-N concentration indicates significant reduction in sawdust treatment (p < 0.05) compared to the control and other application methods. However, the soil sawdust mixed with digestate was more effective than the other methods, because of the cumulative labile carbon contents of the amendment, which implies soil net N immobilization.

• 무역학회지
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• 제44권6호
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• pp.217-230
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• 2019

This study investigates the impacts of international trade and foreign direct investment (FDI) on income distribution both nationally as well as provincially in Vietnam. This study uses panel data of 63 provinces in Vietnam for the period of 2008-2016 and a time series dataset from 1992 to 2016. We found the following results. First, the income distribution is significantly affected by per capita income. When we consider the Kuznets hypothesis, the intra-provincial income inequality of Vietnam's 63 provinces follows a regular U-shaped relationship. In contrast, the income distribution in Vietnam exhibits an inverted U-shaped relationship between the Gini coefficient and per capita income. Second, the inward FDI tends to reduce income gaps in each province through the employment of predominantly low-skilled workers. FDI, however, seems to increase income inequality throughout Vietnam. This result is potentially due to the strong concentration of FDI into a very few areas. Third, the effect of trade openness exhibits a decrease in inequality both within each province and in the whole country of Vietnam.