• Microbiology and Biotechnology Letters
• /
• v.47 no.2
• /
• pp.259-268
• /
• 2019

In this study, the extracellular metalloprotease from Serratia marcescens PPB-26 was purified to homogeneity via ethanol fractionation and DEAE-cellulose column chromatography. Thus, a 3.8-fold purification was achieved with a 20% yield and specific activity of 76.2 U/mg. The purified protease was a 50-kDa monomer whose optimum pH and temperature for activity were 7.5 and $30^{\circ}C$ respectively; however, it was found to remain active in the 5-9 pH range and up to $40^{\circ}C$ for 6 h. The protease had a half-life of 15 days at $4^{\circ}C$, an optimum reaction time of 10 min, and an optimum substrate (casein) concentration of 0.25%. Furthermore, the Michaelis constant ($K_m$) and reaction velocity ($V_{max}$) of the protease were calculated to be 0.28% and $111.11{\mu}moles/(min{\cdot}mg)^{-1}$, respectively. The protease was stable when subjected to metal ions (2 mM), showing increased activity with most (especially $CoCl_2$ and $MgSO_4$ (30.54% increase)). It was also stable when exposed to oxidizing agents, bleaching agents, and detergents (5% v/v for 60 min). It retained 93% of its activity in non-ionic detergents (Tween-20, Tween-80, and Triton X-100). Moreover, wash performance analysis in commercial detergents (Ariel and Tide) showed that not only was the protease capable of protein stain removal, but also reduced cleaning time by 80% when added to detergents. Thus, the Serratia marcescens PPB-26 metalloprotease appears to be a promising new candidate as a laundry additive in the detergent industry.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.2
• /
• pp.42-54
• /
• 2021

The Aft-deck is being applied to the latest unmanned aircraft for the purpose of shielding the gas turbine exhaust plume or spreading jets to increase the mixing rate with the ambient air, thereby reducing the temperature of exhaust gases. In this study, we would like to find out how the performance of the nozzle is affected by the design variables of the Aft-deck. The design variables of aft-deck are selected as length, expansion angle and upper deck shape. The correlation between thrust and plume shielding rate with the length variable is presented. And the correlation between the thrust and the jet diffusion range is presented according to the expansion angle. In addition, the thrust increase effect is confirmed by the removal of the upper deck and the characteristics of transverse velocity vector determined mixing performance with external flow.

• Resources Recycling
• /
• v.30 no.4
• /
• pp.20-26
• /
• 2021

Solar grade silicon (SoG-Si) has been commercially supplied mainly from off-grade high-purity silicon manufactured for electronic-grade Si (EG-Si). Therefore, for wider application of solar cells, the development of a refining process at a considerably lower cost is required. The most cost-effective and direct approach for producing SoG-Si is to purify and upgrade metallurgical-grade Si (MG-Si). In this study, directional solidification of molten MG-Si was conducted in a high-frequency induction furnace to remove iron from molten Si. The experimental conditions and results were also discussed with respect to the effective segregation coefficient, Scheil equation, and Peclet number. The study showed that when the descent velocity of the specimen decreased, the macro segregations of impurities and ingot purities increased. These results were derived from the decrease in the effective segregation coefficient with the decrease in the rate of descent of the specimen.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.5
• /
• pp.767-774
• /
• 2022

In this paper raw spectrum data were analyzed to suggest the moving forward of performance evaluation and quality control of wind profilers of four manufacturers operating in South Korea. For the analysis, the profile of the spectrum averaged by season and the profile of four statistical values (minimum, average, median, and maximum) calculated by Power Spectrum Density (PSD) were used. The quality of spectrum data was the best for LAP-3000, followed by YKJ3, PCL-1300, and CLC-11-H. In Cheorwon and Chupungnyeong, where PCL-1300 was installed, the variability of the spectrum due to ground clutter and non-meteorological signals was large, so ground clutter removal and signal processing such as moving average and multi-peak were required. In Gunsan and Paju, where CLC-11-H was installed, DC (Direct Current) bias and propagation folding were found, so it is necessary to remove the DC bias and limit the effective altitude for observation.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.1
• /
• pp.106-113
• /
• 2023

The supply of microbiological risk-free water is essential to keep food safety and public hygiene. And removal, inactivation, and destruction of microorganisms in drinking water are key for ensuring safety in the food industry. Ultraviolet-C (UV-C) irradiation is an attractive method for efficient disinfection of water without generating toxicity and adversely affecting human health. In this study, the disinfection efficiencies of UV-C irradiation on Shigella flexneri (Gram negative) and Listeria monocytogenes (Gram positive) at various concentrations in drinking water were evaluated using a water purifier. Their morphological and physiological characteristics after UV-C irradiation were observed using fluorescence microscopy and flow cytometry combined with live/dead staining. UV-C irradiation (254 nm wavelength, irradiation dose: 40 mJ/cm²) at a water flow velocity of 3.4 L/min showed disinfection ability on both bacteria up to 10⁸ CFU/4 L. And flow cytometric analysis showed different physiological shift between S. flexneri and L. monocytogenes after UV-C irradiation, but no significant shift of morphology in both bacteria. In addition, each bacterium revealed different characteristics with time-course observation after UV-C irradiation: L. monocytogenes dramatically changed its physiological feature and seemed to reach maximum damage at 4 h and then recovered, whereas S. flexneri seemed to gradually die over time. This study revealed that UV-C irradiation of water purifiers is effective in disinfecting microbial contaminants in drinking water and provides basic information on bacterial features/responses after UV-C irradiation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.2
• /
• pp.56-63
• /
• 2018

The management of Combined Sewer Overflows(CSOs) and Separated Sewer Overflows(SSOs) discharge directly to the effluent system in an untreated state, which occurs when the facility capacity is exceeded due to heavy rain, has become an important issue in recent years as the heavy rain becomes a regular phenomenon. Despite the continuous development of filtration technology, targeting densely populated urban areas, CSOs are rarely applied. Therefore, this study was carried out to optimize the process to apply CSOs in a pilot-scale horizontal flow filtration system with a rope-type synthetic fiber. The research was carried out in two steps: a preliminary study using artificial samples and a field study using sewage. In the preliminary study using an artificial sample, head loss of the filter media itself was analyzed to be approximately 1.1cm, and the head loss was increased by approximately 0.1cm as the linear velocity was increased by 10m/hr. In addition, the SS removal efficiency was stable at 81.4%, the filtration duration was maintained for more than 6 hours, and the average recovery rate of 98% was obtained by air backwashing only. In the on-site evaluation using sewage, the filtration duration was approximately 2 hours and the average removal efficiency of 83.9% was obtained when belt screen (over 450 mesh) was applied as a pre-treatment process to prevent the premature clogging of filter media. To apply the filtration process to CSOs and SSOs, it was concluded that the combination with the pre-treatment process was important to reinforce the hydraulic dimension for the stable maintain of operation period, rather than efficiency. Compared to the dry season, the quality of incoming sewage was lower in the rainy season, which was attributed to the characteristics of the drainage area with higher sanitary sewerage. In addition, the difference in removal efficiency according to the influent quality of the wet season and dry season was small.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.4
• /
• pp.295-302
• /
• 2014

This study demonstrates a double-path CDI as an alternative of advanced wastewater treatment process. While the CDI typically consists of many pairs of electrodes connected in parallel, the new double-path CDI is designed to have series flow path by dividing the module into two stages. The CFD model showed that the double-path had uniform flow distribution with higher velocity and less dead zone compared with the single-path. However, the double-path was predicted to have higher pressure drop(0.7 bar) compared the single-path (0.4 bar). From the unit cell test, the highest TDS removal efficiencies of single- and double-path were up to 88% and 91%, respectively. The rate of increase in pressure drop with an increase of flow rate was higher in double-path than single-path. At 70 mL/min of flow rate, the pressure drop of double-path was 1.67 bar, which was two times higher than single-path. When the electrode spacing was increased from 100 to $200{\mu}m$, the pressure drop of double-path decreased from 1.67 to 0.87 bar, while there was little difference in TDS removal. When proto type double-path CDI was operated using sewage water, TDS, $NH_4{^+}$-N, $NO_3{^-}$-N and $PO_4{^{3-}}$-P removal efficiencies were up to 78%, 50%, 93% and 50%, respectively.

• Journal of Digital Convergence
• /
• v.10 no.8
• /
• pp.201-210
• /
• 2012

Because sensing odor varies depending on each person, even if the odor is released in line with the legal emission permission concentration levels, it can still become a social issue if a civil complaint is made. The purpose of this research is to study the possibility of putting Mn-Cu metallic oxide catalysts into practical use to economically eliminate acetaldehyde which produces a odor in the industrial process. An optimal operating parameter to eliminate acetaldehyde was deduced through a performance evaluation in the research laboratory and the performance was verified by applying the parameter into an actual facility as an on-the-site experiment through a Scale-up of pilot size. The operating temperature of the metallic oxide catalysts researched so far was at the minimum close to $220^{\circ}C$, and the $220^{\circ}C$ elimination efficiency was 50% or below. However, having experimented by using a Mn-Cu metallic oxide catalyst in this research, optimum elimination efficiency showed when space velocity (GHSV) was equal to or below 6,000 $hr^{-1}$. The average elimination efficiency was 61.2% when the catalyst controlling temperature was $120^{\circ}C$, 93.3% when the catalyst controlling temperature was $160^{\circ}C$, and 94.9% when catalyst controlling temperature was $180^{\circ}C$, thereby reflecting high elimination efficiency. The specific surface area of the catalyst was $200m^2/g$ before use, however, was reduced to $47.162m^2/g$ after 24 months and therefore showed that despite the decrease in specific surface area as time passed, there was no significant influence on the performance. Having operated Mn-Cu metallic oxide catalyst systems for at least two years on a site where there was no inflow of toxins like sulfur compounds and acidic gases, we were able to confirm that elimination efficiency of at least 90% was maintained.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.1
• /
• pp.13-24
• /
• 1988

This paper is concentrated on the development of oxygen transfer system by U-tube deep shaft in biological fluidised bed process. The depth of the shaft is 32 m, it is composed of downcomer and riser. Not only flow pattern and oxygen transfer in the deep shaft but also oxygen limitation in biofilm and oxygen utilization in biological fluidised bed are investigated. In this investigation, driving force for liquid circulation in the deep shaft is affected by air injection depth and gas hold-up in downcomer. Flow pattern of the deep shaft is revealed to plug flow. When flow velocity in the deep shaft is maintained to 0.52 m/sec, $K_La$ value is peak at 25~30 m depth in riser. The efficiency of dissolved oxygen supply which passed from the deep shaft to biological fluidised bed is estimated to 56~81 % in the organic wastewater treatment using the deep shaft and when dissolved oxygen concentration is 9.2 mg/l and over, limiting factors of flux and substrate within biofilm are organic materials. Terefore, organic loadings could be increase without decreasing of BOD removal efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.2
• /
• pp.983-989
• /
• 2013

The current research reviewed the design conditions that would maximize the efficiency of the hybrid collector that combines in one unit "cyclone-inertial impaction-bag filter". The computational analysis for the shape of cyclone entry predicts that a design that installs the guide vane at the entry of the tangential type cyclone brings a high-rpm and powerful vortex, very effective in promoting the deflection of coarse particles from the streamline at the cyclone. As the lower part of the cyclone is venturi-shaped, however, a strong flow downward of 4 to 5 m/sec persists through the lower part of the hopper, revealing the likely reentrainment of collected dust. And the removal of the venturi at the lower part of the cyclone would solve the problem of the reentrainment of collected dust. The acceleration of the flow velocity through the adjustment of the gap of the collision baffle would increase the effect of collision, but as the interference with the dust separation is expected, the original design should be kept for the baffle.