• Journal of Korean Society on Water Environment
• /
• v.32 no.6
• /
• pp.537-545
• /
• 2016

In order to cope with the new and strict government regulations for turbid water discharge from construction sites, this study tested whether synthetic fiber filters can replace conventional best management practices. The filter efficiency was about 10 to 60% with a varying filter depth of 5 to 15cm, presuming extreme storm flow conditions to be in the range of 800 to 1500m/day of filtration rates. Fiber filter acts exactly like a granular filter, i.e. the separation efficiency is directly and inversely proportional to filter depth and rate, respectively. Based on the operational data, we suggested the Log-Log design relationship, which can be used to determine the filter depth and area. Compared to the widely used gravel filter which treats the turbid water at the construction site, about 20% higher efficiency was obtained under similar operating conditions. Cleaning the filter through a simple hand-washing method at the time of break-through, achieved about 90% soil recovery.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.5
• /
• pp.677-684
• /
• 2006

Electro-flotation(EF), a novel sludge thickening method, could improve the dewaterability of activated sludge. The gas(microbubbles) generated during EF decreased the solid-liquid separation time below 1/5 of the time required for gravity sedimentation. In addition, over 90% of the sludge volume reduction could be achieved by EF although the settling characteristics of the sludge was very poor. The SRF(specific resistance to filtration) of the thickened sludge by EF was much lower than that of the sludge thickened by gravity sedimentation. The SRF of the thickened sludge decreased exponentially with increase of gas generation rate of the EF system. Gas generation rate could be controlled by varying the current density of the electrode. Degasing of the microbubbles by vigorous mixing of the thickened sludge layer deteriorated the dewaterability of the sludge. Therefore, it is obvious that the gas bubbles entrapped in the thickened sludge play a key role in the observed dewaterability improvement.

• Journal of Korean Society for Atmospheric Environment
• /
• v.13 no.5
• /
• pp.383-396
• /
• 1997

Numerical prediction of the pollutant dispersion over a two-dimensional hilly terrain is presented. The dispersion model used in the present work is based on the gradient diffusion theory and the finite-volume method on a non-orthogonal boundary-fitted grid system. The numerical model is validated by comparing the results with the available experimental data for the flat-floor dispersion within a turbulent boundary-layer. The numerical error analysis is performed based on the guideline of Kasibhatla et al.(1988) for the elevated-source dispersion in the flat-floor boundary layer having a power-law velocity and linear eddy-diffusivity profile. The influences of the two-dimensional hilly terrain on the dispersion from a continuously released source are numerically investigated by changing the emission locations and heights. It is found that the distributions of ground-level concentration are strongly influenced by the source location and the emission height. Hence, the terrain amplification factor is greatly enhanced when the pollutant source is located within a flow separation region. Dispersion from a source of short duration is also simulated and the duration time of the pollutant is compared at several downstream locations on a hilly terrain. The results of the numerical prediction are applied to the evaluation of environmental impacts due to the automobile exhausts at the seashore highway with a parallel mountain range.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.53 no.4
• /
• pp.404-412
• /
• 2017

A centrifugal cyclone dust collecting apparatus includes a hydro cyclone dust collecting apparatus for separating solid or liquid using liquid or suspension as a medium. In this study, the formation mechanism and improvement of air core and inner air layer were confirmed through Particle Image Velocimetry. These results showed that the modified experimental model was designed in the conventional method suitable for the separation of juvenile fish and eggs. The inlet speed of the multi-stage hydrocyclone dust collector, which can increase the inlet velocity and minimize floatage in the turbulence chamber, was increased from 0.15 to 0.30 m/s. As a result, the air core was stably formed, the inner air layer was increased with increasing speed. In addition, the dust collecting efficiency of egg and juvenile fish was 97.8% on average, It can infer that this system confirmed the ability to efficiently collect particles of $40{\mu}m$ or more.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.6
• /
• pp.128-140
• /
• 1997

A new super compact condenser(SCC), which has been developed recently is especially suitable for an alternative refrigerant HFC-134a due to its high performance and compactness. The SCC is composed of two pipe headers, baffles, narrow multi-rectangular channels, and louvered fin arrays. Alternating inlet and outlet by the inserted baffles in pipe headers guide refrigerant to and from the narrow multi-rectangular channels. Since the flow rate and its lengh are changed depending on the number and location of baffles, the corresponding pressure drop and heat transfer rate are changed. The present study aims to theoretically and experimentally investigate the effects of baffle location and its number on the pressure drop and thermal performance of the SCC with 40 multi-rectangular channels. The results show that the present method provides an acceptable prediction of pressure drop and heat transfer rate for a 4 pass SCC. However, the model significantly under predicts the performance of a 3 pass SCC, which may be attributed to the phase separation of refrigerant flowing through header pipes. Pressure drop is more signifi- cantly influenced than heat transfer rate by the baffle location.

• YAKHAK HOEJI
• /
• v.41 no.5
• /
• pp.607-614
• /
• 1997

Flurbiprofen- and flurbiprofen axetil-loaded microemulsions composed of soybean oil, poloxamer 407, glycerine and water were prepared by generator-type homgenizer and ultrasoni c probe system. The particle size of microemulsions was measured by the dynamic light scattering method. The pharmacokinetics and organ distribution of flurbiprofen were investigated after intravenous injection of flurbiprofen solution, flurbiprofen-loaded microemulsion and flurbiprofen axetil-loaded microemulsions equivalent to 10mg/kg of flurbiprofen to rats. Blood samples were collected from the anterior ciliary artery of rats for 24hr, and flurbiprofen in plasma and organs was analyzed by HPLC. Stable microemulsions were prepared. Even though there is a little change in droplet size just after the preparation, no creaming and no separation were occured during the storage period for 6 months at 4, 21, 37 and 45$^{\circ}C$. Pharmacokinetic parameters and organ distribution of flurbiprofen after intravenous injection of flurbiprofen- and flurbiprofen axetil-loaded microemulsions emulsified with poloxamer 407 were not significantly different from those of commercial lipid microemulsion emulsified with lecithin. Therefore, it is concluded that flurbiprofen- and flurbiprofen axetil-loaded microemulsion prepared with poloxamer 407 could be used as a parenteral formulation.

• Membrane Journal
• /
• v.12 no.3
• /
• pp.143-150
• /
• 2002

Electrodialysis(ED) is a reliable and effective process for the separation and concentration of ionic compounds. However, commercial uses of ED are often hindered by the cost of the stack that mainly resulted from the ion-exchange membrane cost. In order to minimize the membrane cost, it is desired to operate ED at the highest practicable current density. In an actual ED system the high current operation is limited by the concentration polarization phenomenon. This article illustrates the transport phenomena of ions through ion exchange membranes using current-voltage relations as a characterizing method. Also recent studies on electroconvection and water-spitting phenomena caused by concentration polarization were reviewed.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1995.04a
• /
• pp.11-15
• /
• 1995

Polysulfone (PS) membranes were prepared by the phase inversion process using water or isopropanol as nonsolvent. The Flory-Huggins theory for a ternary system nonsolvent/solvent/polymer is applied to describe the thermodynamic equilibria of the components. The calculated ternary phase equilibria show that demixing of a PS binary solution with n-methylpyrrolidone (NMP) will be fast in a water coagulation bath and will be delayed in an isopropanol bath. The prepared membranes were characterized by SEM, gas adsorption-desorption measurement, and permeability test. The membrane, which is precipitated by fast demixing in a water bath, has nodular structures in the skin region and includes finger-like cavities in the sublayer. The membrane coagulated by isopropanol has a very dense and thick skin structure, which is formed by delayed demixing. The membrane coagulated by isopropanol showed considerably lower pore volume and surface area compared to that observed with water coagulation method. With dimethylformamide (DMF) as solvent and 2-3 wt% of water, the solution can show the liquid-liquid phase separation due to agglomation of the polymer-lean phase from the homogeneous solution. The membranes, which were coagulated near an equilibrium state, show the large (micron size) round pores in the whole membranes. The pores do not contribute the permeation characteristics.

• YAKHAK HOEJI
• /
• v.32 no.1
• /
• pp.26-39
• /
• 1988

Eudragit $RS^{\circledR}$ polymer was used as a wall material for the microencapsulation of aspirin by a phase separation method from chloroform-cyclohexane system with 5% polyisobutylene (PIB) in cyclohexane, and microcapsules obtained were evaluated by particle size analysis, scanning electron microscopy (SEM), drug release and drug stability test. With PIB as a coacervation inducing agent, smooth and tight microcapsules with less aggregation were obtained. Below 1 : 0.3 core-wall ratio, it was possible to coat individual particle. Variation of production conditions showed that increasing the proportion of wall material, particle size and wall thickness of microcapsules and the concentration of paraffin wax in cyclohexane as a sealant sustained drug release rates effectively. SEM confirmed that larger microcapsules after drug release did not rupture into smaller particles but contained a few small pores on the surface. Aspirin release from Eudragit $RS^{\circledR}$ coated microcapsules was independent of the pH of medium, and the mechanism of drug release from non-sealed and sealed microcapsules appeared to fit Higuchi matrix model kinetics. Aspirin in the mixture of aspirin microcapsules and sodium bicarbonate was by far more stable than that in the mixture of pure aspirin and sodium bicarbonate.

• Archives of Pharmacal Research
• /
• v.27 no.6
• /
• pp.619-623
• /
• 2004

Tissue factor (TF, tissue thromboplastin) is a membrane bound glycoprotein, which acceler-ates the blood clotting, activating both the intrinsic and the extrinsic pathways to serve as a cofactor for activated factor VII (Vila). The TF-factor Vila complex (TF/VIIa) proteolytically activates factors IX and X, which leads to the generation of thrombin and fibrin clots. In order to isolate TF inhibitors, by means of a bioassay-directed chromatographic separation technique, from the leaves of Eriobotrya japonica Lindley (Rosaceae), a known sesquiterpene glycoside (2) and ferulic acid (3) were isolated as inhibitors that were evaluated using a single-clotting assay method for determining TF activity. Another sesquiterpene glycoside (1) was also isolated but was inactive in the assay system. Compound 3 was yielded by alkaline hydrolysis of compound 2. The structures of compounds 1, 2, and 3 were identified by means of spectral analysis as $3-O-{\alph}-L-rhamnopyranosyl-(1{\rightarrow}4)-a-L-rhamnopyranosyl-(1{\rightarrow}2)-[{\alph}-L-rhamnopyrano-syl-(1{\rightarrow}6)]-{\beta}-D-glucopyranosyl nerolidol$ (1), $3-O-{\alph}-L-rhamnopyranosyl-(1{\rightarrow}4)-{\alph}-L-rhamnopyr-anosyl-(1{\rightarrow}2)-[{\alph}-L-(4-trans-feruloyl)-rhamnopyranosyl-(1{\rightarrow}6)]-{\beta}-D-glucopyranosyl$ nerolidol (2) and ferulic acid (3), respectively. Compounds 2 and 3 inhibited 50% of the TF activity at con-centrations of 2 and $369{\;}\mu\textrm{m}/TF$ units, respectively.