• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.1-8
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• 2006

An experimental study was carried out in order to investigate the influence of Reynolds number on the near-wake of an oscillating airfoil. An NACA 0012 airfoil was sinusoidally pitched at the quarter chord point, and is oscillated over a range of instantaneous angles of attack of $\pm$6$^{\circ}$. An X-type hot-wire probe was employed to measure the near-wake of an oscillating airfoil, and the smoke-wire visualization technique was used to examine the flow properties of the boundary layer. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were 2.3${\times}10^4$, 3.3$\times$104 and 4.8${\times}10^4$, respectively. The frequency of airfoil oscillation was adjusted to fix a reduced frequency of K=0.1. The results show that the properties of the boundary layer and the near-wake can dramatically be distinguished in the range of Reynolds numbers between 2.3${\times}10^4$ and 3.3${\times}10^4$, on the other hand, it is similar in the cases of Re=3.3$\times$104 and 4.8$\times$104. This is caused by that the unsteady separation point is dramatically delayed in case of Re= 2.3${\times}10^4$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.1-9
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• 2018

Lambda wing type Unmanned Combat Aerial Vehicle(UCAV) which adopts Blended Wing Body(BWB) has relatively less drag and more stealth performance than conventional aircraft. However, Pitching moment is rapidly increased at a specific angle of attack affected by leading edge vortex due to leading edge sweep angle. Wind tunnel testing and numerical analysis were carried out with UCAV 1303 configuration on condition of 50 m/s of flow velocity, $-4^{\circ}{\sim}28^{\circ}$ of the range of angle-of-attack. The effect of wing twist for longitudinal stability at the various angles of attack was verified in this study. When negative twist is applied on the wing, Pitch-break was onset at higher angle of attack due to delayed flow separation on outboard of the wing. On the other hand, pitch-break was onset at lower angle of attack and lift-to-drag ratio was increased when positive twist is applied on the wing.

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.285-290
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• 2010

The nucleotide sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene of octopus groups collected from Muan, Taean, Yesu, Jeju in Korea and Youngsung, Daeryen in China were analyzed for the identification of species and populations. Six haplotypes were identified from the analyzed 60 individuals. All of the individuals (N = 10) from Jeju showed the A haplotype which was not observed from other groups, and could be classified as a distinct group. The analyzed groups could form two separate clade in MEGA4 analysis. The individuals from Muan, Taean, Yesu in Korea and Daeryen in China form a clase and the others from Jeju in Korea and Youngsung in China formed the other clade. The analysis of relationship among the groups showed the same results. Individuals belong to the group A (Muan, Taean, Yesu and Daeryen) showed closer relationship than individuals belong to the group B (Jeju and Youngsung). Although the CO1 universal primers used in this study was useful as a marker for species identification among Octopus, analysis of population was limited because of few variations in the partial sequences of CO1 analyzed in this study. However, it was possible to show the limited gene flow among the groups which is resulted from the spatial separation and differences in their habitats.

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

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.320-331
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• 2016

Linze-Donawitz gas (LDG) adjunctively produced in the steel mill contains over 60% of CO. Two processes that recover high purity CO from LDG were considered: COSORB and CO-Pressure swing adsorption (PSA). This study aimed to decide which one is more economically feasible than the other by techno-economic analysis (TEA). From the technical point of view of TEA, the process flow diagram (PFD) was constructed, the mass and energy balances were calculated, and the equipment type and size were determined in order to estimate the total capital investment (TCI) and the total production cost (TPC). From the economic point of view of TEA, economic performance such as return on investment (ROI) and payback period (PBP) was evaluated, and the sensitivity analysis was carried out to identify key factors influencing ROI and PBP. It was found that CO-PSA is more economically feasible due to higher ROI and lower PBP. The CO price highly influenced ROI and PBP.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.509-515
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• 1999

Lactic acid bacteria (LAB) fermented foods were prepared from egg white powder (EWP), casein and growth stimulating agents (GSA). The effects of GSA on acid production and growth of Lactobacillus were studied. The effects of GSA on sensory properties and viscosity of LAB fermented foods were also studied. Acid production by Lactobacillus was stimulated by addition of GSA (0.3% or 1%, W/V). Although stimulating effect differed among each GSA, some GSA increased the acidity up to the level of fermented milk. However, stimulating effect of GSA on viable cells was not noticeable. Acid production by L. acidophilus was generally higher than other Lactobacilli. The optimum concentration of GSA added to substrate was 1% (W/V). Sensory evaluation showed that the optimum fermentation time was 18hr. The sensory properties of GSA samples were evaluated as slightly lower than that of fermented milk because GSA samples showed whey separation and taste and smell of GSA. Apparent viscosity of GSA samples was significantly lower than that of fermented milk and control sample (p<0.05). There was no significant difference of apparent viscosity among GSA samples. GSA samples, fermented milk and control sample showed thixotropic flow characteristics.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.810-815
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• 2011

Concentrated water discharged from seawater desalination process contains a high concentration of $Na^+$ ion. Electrolysis was applied to synthesize NaOH solution from the highly concentrated NaCl solution. The effect of various operating parameters of composited laboratory-scale chlor-alkali (CA) membrane cell was investigated. The operating parameters such as membrane types (CIMS and Nafion membranes), pretreatment of the membrane, flow rate (73 mL/min~200 mL/min), initial $Na^+$ ion concentration (1.5 M, 3M and 5 M) and current (1.5A and 2A) were evaluated. It was observed that synthesis efficiency of NaOH solution with CIMS membrane was higher than that with Nafion membrane, but the durability of CIMS membrane on $Cl_2$ gas was poor. The synthesis efficiency of NaOH solution increased with increasing initial $Na^+$ ion concentration and current, while the efficiency decreased with increasing flow rate using Nafion membrane.

• KSBB Journal
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• v.20 no.1 s.90
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• pp.12-17
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• 2005

Despite a wide range of fatty acids in fish oil, its the usage are very limited owing to off-flavors and volatile compounds in the oil. A way to extract and remove volatile compounds was performed at a semi-flow extractor by using supercritical carbon dioxide $(SC-CO_2)$. Samples of the oil were treated at the conditions which ranged from $30\;to\;80^{\circ}C$ and from 80 to 200 bar with 10 mL/min flow rate of carbon dioxide. In the oil the volatile compounds were analyzed by gas chromatography. Before extraction with $SC-CO_2$ the oil sample was detected over 129 peaks but 99 compounds were identified. The results demonstrated that at $40^{\circ}C$ and 200 bar extraction condition the volatile compounds in the tuna fish oil were removed, except for 14 compounds identified after extraction and other $SC-CO_2$ extraction conditions reached to high reduction of the volatile compounds.

• Resources Recycling
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• v.7 no.3
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• pp.3-10
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• 1998

Simulated waste liquid containing 50 ppm cobalt ion was treated by adsorbing colloidal flotation using Fe(III) or Al(IlI) as flocclant and a sodium lamyl sulfate as a collector. Parameters such as pH, surfactant concentration, Fe(III) or Al(III) concentration, gas flow rate, etc., W앙e considered. The flotation with Fe(III) showed 99.8% removal efficiency of cohalt on the conditions of initial cobalt ion concentration 50 ppm, pH 9.5, gas flow rate 70 ml/min, and flotation time 30 min. When the waste solution, was treated with 35% $H_2O_2$ prior to adsorbing colloidal flotation, the optimal pH for removing cobalt shifted m to weak alkaline range and flotation could be applied in wider range of pH as compared to non-use of $H_2O_2$. Additional use of 20 ppm Al(III) after precipitation of 50 ppm Co(II) with 50 ppm Fe(III) made the optimal pH range for preferable flotation w wider. Foreign ions such as, $NO_3^-$, $SO_4^{2-}$, $Na^+$, $Ca^{2+}$ were adopted and their effects were observed. Of which sulfate ion was f found to be detrimental to removal of cob퍼t ion by flotation. Coprecipitation of Co ion with Fe(III) and Al(III) resulted in b better removal efficiency of cobalt IOn 피 the presence of sulfate ion.

• Resources Recycling
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• v.7 no.3
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• pp.11-16
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• 1998

Simulated waste liquid containing 50 ppm cobalt ion was t$\xi$sted by precipitate flotation using a sodium lauryl sulfate as a c collector. The effects of initial cobalt ion concentration, pH, surfactant concentration, flotation time, gas flow rate and foreign i ions on removal efficiency of cobalt ion were studied. Pretreatment of the waste liquid with 35% $H_2O_2$, prior to precipitate f flotation made shin of optimal flotation pH from the strong alkalinity to weak alkaline range and made a favorable flotation of c cobalt ion in wide range of pH. For the result of this experiment, 99.8% removal efficiency was obtained on the conditions of initial coball ion concentration 50 ppm, pH 9.5 gas flow rate 70 mllmin, flotation time 30 min. The simulate ion was fanned t to be the most harmful ion against removal of cobalt by precipitate flotation of the species which were tested The presence of 0.1 M of $SO_4^{2-}$ ion decreased remo,때 $\xi$폐iciency of cobalt to 90% while the cobalt were almost entirely removed in the a absence of sulfate ion.