• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.367-373
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• 2011

Mechanism of rapid mixing effect on chemical phosphorus removal is evaluated in this study. Assuming that chemical phosphorus removal is unaffected by mixing time, only rapid mixing intensity is evaluated. In order to find out the mechanism, it is hypothesized that rapid mixing affects the Al hydrolysis speciation, and that formation of more monomeric species ($Al^a$) results in better removal of phosphorus. According to a ferron assay, more $Al^a$ formed at higher mixing intensity than at lower intensity. Subsequent experiments revealed that better phosphorus removal was obtained at higher intensity than at lower intensity, in terms of the molar ratio of $Al_{added}/P_{removed}$. The proposed hypothesis was proved in this study. Chemical phosphorus removal is affected by rapid mixing intensity due to its effect on the Al hydrolysis speciation.

• Environmental Engineering Research
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• v.17 no.3
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• pp.151-156
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• 2012

This research described the magnetic method for the rapid removal of green algae in water. We modified the pH, cation concentration, and magnetic powder concentration to discover the best removal performance. In order to rapidly remove green algae from water, we added magnetic powder and chitosan into algae water to make a magnetic substance and this was extracted by a strong neodymium magnet. The optimized conditions were pH of 6.5-7.5, chitosan concentration of 10 mg/L, and magnetite powder concentration of less than 0.05%. A higher removing rate was observed when a higher amount of magnetite or chitosan was used, but the total amounts of phosphorus or nitrogen were not decreased.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.E
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• pp.1-8
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• 1999

Catalytic performance for NOx removal by Ga-incorporated silicates(Ga-silicate; Gallosilicate) with MFI type synthesized by the rapid crystallization method was reported in this study. NOx removal was investigated under the condition of O2 excess(10%), with various hydrocarbons of low concentrations. Effect of H2O(2%) addition was also considered. The result showd that the conversion from NOx to N2 was enhanced on the Ga-silicate compared with the Al-silicate. Furthermore, the performance for NOx conversion on the Ga-silicate increased with addition of water.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.559-571
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• 2006

The overall objective of this research was to find out the interrelation of coagulant and organic matter during rapid mixing process and to identify the change of organic matter by mixing condition and to evaluate the effect of coagulation pH. During the coagulation, substantial changes in dissolved organics must be occurred by coagulation due to the simultaneous formation of microflocs and NOM precipitates. Increase in the organic removal efficiency should be mainly caused by the removal of microflocs formed during coagulant injection. That is, during the mixing period, substantial amount of dissolved organics were transformed into microflocs due to the simultaneous formation of microflocs and NOM precipitates. The results also showed that 40 to 80% of dissolved organic matter was converted into particulate material after rapid mixing process of coagulation. During the rapid mixing period, for purewater, formation of dissolved Al(III) (monomer and polymer) constant by rapid mixing condition, but for raw water, the species of Al hydrolysis showed different result. During the rapid mixing period, for high coagulant dose, Al-ferron reaction increases rapidly. At A/D(Adsorption and Destabilization) and sweep condition, both $Al(OH)_3(s)$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

• Journal of Korean society of Dental Hygiene
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• v.18 no.3
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• pp.269-280
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• 2018

Objectives: The purpose of this study was to investigate the change in the posture of dental hygiene students and clinical dental hygienists when implementing dental scaling before and after posture correction training using the rapid upper limb assessment (RULA) method and 3D motion analysis. Methods: Thirty-two healthy volunteers performed dental scaling to remove artificial calculus on dental manikin. The movement and angle of the joints were verified by RULA and 3D motion analysis during the procedure. The subjects were also photographed for 1 minute during the procedure for 10 minutes while the calculus was removed. After the removal of the calculus, the subject and the instructor checked the video together. Posture correction training was conducted by the instructor so that the subject could perform the calculus removal operation in the correct posture. Artificial calculus of the adjacent teeth was then removed for the same period of time, and the change in posture was reviewed. Results: The total score of the posture change using RULA was $5.72{\pm}0.58$ before training and $4.31{\pm}0.10$ after training, showing a significant decrease after training (p<0.001), and upper arm, lower arm, wrist position, neck and waist position showed significant decrease after training. The three-dimensional motion analysis showed significant differences according to the criteria measured at all measurement sites except the left shoulder (p<0.05) Conclusions: It was confirmed through RULA and 3D motion analysis that postural correction training using calculus removal images was effective, and that correct postural education is essential to preventing musculoskeletal diseases caused by removal of calculus.

• Clean Technology
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• v.18 no.4
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• pp.404-409
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• 2012

In this study, the effects of mixing intensity and coagulant dosages on the characteristics of floc growth for phosphorus removal were investigated. The experiments were conducted under Al/P molar ratio of 1.0, 1.5 and 2.0; rapid mixing intensity with G value of 100, 300, and 500 $s^{-1}$. The characteristics of floc growth were measured by flocculation index (FSI) and the removal efficiencies of phosphorus by using different size filters. The removal efficiencies of soluble phosphorus increased as Al/P molar ratio and rapid mixing intensity increased. However, the highest removal efficiencies of T-P were observed at G value of 300 $s^{-1}$. When Al/P molar ratio was lower than 1.0, the value of FSI at G value of 500 $s^{-1}$ was the largest. However, when Al/P ratio was larger than 1.0, the value of FSI at G value 300 $s^{-1}$ was the largest. Effects of mixing intensity and Al/P molar ratio on coagulation for phosphorus removal of synthetic and real wastewater effluent were observed to be similar.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.150-153
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• 2016

This study evaluates the efficacy of titanium tetrachloride ($TiCl_4$) on phosphorus (P) removal in synthetic wastewater. Jar test experiments were performed at various $TiCl_4$ concentration (0.25-0.59 mM), and intensities of slow (30-60 rpm) and rapid (100-250 rpm) mixings to determine the conditions at which P removal was most efficient. The P-removal efficiency was highest (about 99%) at $TiCl_4$ concentration $([TiCl_4])=0.39mM$ with rapid-mixing intensity=100 rpm and slow-mixing intensity=30 rpm. The slow-mixing intensity was more sensitive than the rapid-mixing intensity to the P removal efficiency when [$TiCl_4$] was low ($0.25{\leq}[TiCl_4]{\leq}0.27mM$).

• Journal of Plant Biology
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• v.37 no.3
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• pp.357-363
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• 1994

An expreiment with non-nodulating alfalfa (Medicago sativa L.) plants was designed to investigate the changes in protein contents and the activities of proteolytic enzymes during a regrowth period of 24 d. Shoot removal caused a depression of root growth and significantly reduced protein contents in roots. An initial decline of root proteins for the first 10 d was followed by a rapid recovery from d 11 to 24. The major increase of regrowing shoot weight occurred also from d 11. The activities of aminopeptidase and endoprotease slightly decreased in regrowing leaves, while protein contents remains stable after shoot removal. Roots exhibited source behaviour with a rapid increase of endoprotease activities for the first 10 d of regrowth; about a 370% increase over the initial level was observed. Increase in endoprotease activity in roots coincided with the time of protein remobilization after shoot removal, indicating the important role of endoproteases in protein degradation.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.731-741
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• 1997

Optimum design conditions of rapid mixing impellers for an effective Water Treatment Plant operation were experimentally studied by thorough examination of parameters, such as impeller type and detention time. which govern the removal efficiency of turbidity. It was found that the impeller type is one of the major parameters governing the economic power consumption and the efficiency of turbidity removal. The experimental results showed that not only the velocity gradient G but also a new design guide. so called mixing energy per unit volume of raw water, could be used as a design and operation guides for rapid mixing in W.T.P.

• 수도
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• v.23 no.6 s.81
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• pp.13-21
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• 1996