• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.34-38
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• 2005

Effects of pH level and slurry particle size on material removal rate and planarization of langasite single crystal wafer have been examined. Higher material removal rate was obtained with lower pH level slurries while the planarization was found to be determined by average particle size of colloidal silica slurries. Slurries containing 0.045 ㎛ amorphous silica particles showed the best polishing effect without any scratches on the surface. Effective particle number has a strong effect on the surface planarization and the removal rate, so that the lower effective particle numbers produced low removal rate but the better planarization results.

• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.73-79
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• 1997

This research was intended as an investigation of applying Reduced Pressure Evaporation as efficient treatment method for landfill leachate. According to the variance of time, temperature, pressure and pH in experiments, the properties of leachate treatment are follows. The removal efficiencies of COD, NH$_{3}$-N, TOC, Conductivity and SS on the basis of reaction time was 96.4%-97.5%, -1.4%-53.7%, 81.7%-89.0%, 92.0%-95.3% and 99.86%-99.97%, respectively. When the pH of Influent was 7.5, the pH of effluent was increased to 10-11 with time elapse. It is concluded that the orgin of pH increase may be ammonia. When the properties of concentrate were investigated at the concentration ratio 90%(V/V), concentration difficiency represented in the ratio of experimental value/calculated value had following orders ; COD>TOC>NH$_{3}$-N>Conductivity>SS. Concentrate had good precipitation because of additive thermal treatment in the process. When evaporation experiments with pH adjustment of 4.0, 6.0, 7.5, 9.0 and 10.0 were performed ; Acidic evaporation experiments(pH 4.0, 6.0) showed low removal efficiency(81.6, 87.6%) of COD and high removal efficiency (97.5%. 84.6%) of NH$_{3}$-N at initial evaporation. Basic evaporation(pH 9.0, 10.0) showed high removal efficiency (97.2%, 98.9%) of COD and very low removal efficiency (-7.4%, -27.2%) of NH$_{3}$-N at initial evaporation.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.2
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• pp.245-257
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• 1998

This study was performed to measure the changes of the mandibular movement and the masticatory muscular activities - anterior temporal and masseter muscle of both side - reflected by intentional increase of anterior guidance angie. For this study, 5 volunteers (3 males and 2 females with average age of 24.0) were selected. Each volunteer had Angle's classification I and did not have any missing tooth except third molar and any extensive restorations. Metallic guide plate was made at volunteer's working model fabricated by improved dental stone and cemented to the palatal surface of maxillary central incisor using resin cement(Panavia $21^{(R)}$) and then adjusted not to give any occlusal interferences at intercuspal position. The activity of masticatory muscles and the changes of mandibular movement were recorded by EMG and Sirognathograph in Biopak analysing system(Bioresearch Inc., Milwaukee, Wisconsin, USA). Measurement was done at before experiment, immediatley after placement, 1 week after placement, immediately after removal, and 1 week after removal. The results were as follows: 1. Moderate phonetic disturbance and mild headache were occured to 3 volunteers for 2 days after setting and 1 volunteer had positive reaction to percussion and slight midline diastema. But all of these clinical signs were diappeared 1 week after removal and the other volunteer did not have any special clinical sign. 2. In the EMG of the mandibular rest position, the mean value of anterior tempotal muscle was increased immediately after placement(p<0.01) and then decreased 1 week after placement(p<0.05) and increased 1 week after removal(p<0.05) but not recovered as before experiment. The mean value of masseter muscle was decreased during the experiment period. 3. In the EMG during mandibular protrusive movement, all muscular activity was decreased during the experiment period. Reduced activity was not recovered 1 week after removal(p<0.03). 4. During the habitual opening, anteroposterior movement of mandible was decreased immediately after placement(p<0.05) and then increased 1 week after placement but not statistically significant(p>0.1). Vertical movement was not shown significant difference during the experiment period(p>0.1). Lateral movement was decreased immediately after placement(p<0.05) and then increased 1 week after placement but not recovered as before experiment. The opening and closing velocity of mandible was shown minor changes but not statistically significant. 5. During the habitual opening, anteroposterior movement of mandible was decreased 1 week after placement(p<0.05) and then increased immediately after removal and recovered 1 week after removal as before experiment. Vertical movement was not shown significant changes. Lateral displacement of mandible was increased continuously and recovered 1 week after removal. Opening velocity was temporarily increased immediately after removal but recovered and closing velocity was not shown significant changes. 6. During the right side chewing, anteroposterior movement of mandible was increased immediately after removal but recovered and vertical movement was not shown statistically significant results. Lateral displacement and velocity of mandible were not shown significant results. 7. During the left side chewing, the changes of mandibular movement pattern were not shown statistically significant results.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.41-45
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• 1999

Simulated liquid waste containing 50 ppm cobalt ion was treated by precipitate flotation using the surfactant of sodium lauryl sulfate. The effects of initial cobalt ion concentration, pH, surfactant concentration, removal time, gas flow rate and foreign ions were estimated on removal efficiency. 35% $H_2O_2$ was added for pre-treatment stage before precipitate flotation. As the result of pre-treatment, optimum removal pH and the pH of treated water being discharged were lowed and optimum removal pH range was broadened. For the result of this experiment, 99.8% removal efficiency was obtained at the condition of 50ppm of initial cobalt ion concentration, pH 9.5, 70 mL/min of gas flow rate, and 30 min of removal time. Attraction between precipitate and surfactant was supposed to be influenced by solubility and chemical affinity among species in sloution as well as zeta potential. The influence of foreign ions such as, $NO_3{^-}$, ${SO_4}^{-2}$, $Na^+$, $Ca^{+2}$ on the removal efficiency was also observed. Removal efficiency by precipitate flotation containing 0.1 M of ${SO_4}^{-2}$ ion decreased to 90% due to the decrease of zeta potential and interruption of precipitation.

• Clean Technology
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• v.16 no.4
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• pp.258-264
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• 2010

This study estimated the possibility of phosphate removal characteristics to utilize EAF(electric arc furnace) slag as submarine cover material. The major phosphate removal mechanism was a certain formation of HAP precipitation occurred by the ionization reaction between $Ca^{2+}$ and $OH^-$, which were leached from the EAF Slag. Another phosphate removal mechanism was the adsortion of EAF slag surface. As a result of $PO_4{^-}-P$ removal characteristics using continuous column reactor, $PO_4{^-}-P$ concentration decreased rapidly after 3 days and 10 days later, it show under 0.5 ppm. The result as applied in real sea water, shows that the phosphate removal effects were 93~98% by the subaqueous sediment removal using the EAF slag. In conclusion, EAF slag is useful in $PO_4{^-}-P$ removal and control and it is possible to use without additional process like crush and selection.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.1
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• pp.71-78
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• 2006

The removal of protozoa in the coagulation process was evaluated under the different pH and turbidity using the jar test after the addition of polyaluminium chloride (PAC) as a coagulant. Two well-known protozoa of Cryptosporidium parvum and Giardia lamblia were tested at the same time with turbidity, the critical water quality parameter of the water treatment process. Both protozoa were removed about 1log (and up to 2log) at the optimum injection of PAC. The source water turbidity and pH affected the removal of protozoa and turbidity. At neutral and alkaline pH, 1.3-1.7log removal of protozoa for low turbid water with 5NTU, and 1.6-2.3log removal for high turbid water with 30NTU were achieved. However, at acidic pH, maximum 0.8-1.0log and 1.1-1.2log were removed for low and high turbid water, respectively, at the optimum PAC injection of 15mg/L. The relation of protozoa and turbidity removals were expressed as the 1st order equation (significantly positive relation) in the most of the tested conditions. In addition, the relation of protozoan removals with residual turbidity were also expressed the 1st order equation (significantly negative relation), although the significance of the equations were reduced at acidic pH. Therefore, residual turbidity could be a good index of efficient protozoan removal in the coagulation process, probably except at the low pH condition.

• Journal of dental hygiene science
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• v.22 no.4
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• pp.199-205
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• 2022

Background: The use of dental floss is associated with a reduction in dental caries and periodontal disease. According to personal preference, not only thread type but also C type and Y type floss are used. Although the effectiveness of dental floss for removing dental plaque has been proven, plaque removal effect of C type and Y type floss has not been well reported. In this study, the plaque removal effect of C type and Y type floss compared to thread type floss was experimentally verified. Methods: Thread type, C type and Y type floss were used to remove dental plaque. Ten people in each flossing group participated, and by applying dental floss to the 6 incisors of the maxilla and mandible, the degree of dental plaque was analyzed by QLF-D. To evaluate the removal degree of dental plaque before and after flossing, Simple Plaque Score (SPS), Area R30, Area R70, and Area R120 score were measured. Results: In the analysis using the Area R30 fluorescence score of the QLF-D system, the degree of plaque removal according to the application of dental floss was effective in all the thread type (p=0.018), C-type (p=0.012), and Y-type (p=0.012) floss groups compared to before the application of the floss. Among them, C type floss was more effective in removing plaque than thread type and Y type floss. However, the plaque removal effect between the three floss types was not significantly different in ∆SPS (p=0.674), ∆Area R30 (p=0.726), ∆Area R70 (p=0.504), and ∆Area R120 scores (p=0.423). Conclusion: Thread type, C type, and Y type floss were all effective in removing dental plaque, but there was no significant difference in dental plaque removal effect according to the type of floss.

• Journal of Environmental Science International
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• v.24 no.1
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• pp.47-53
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• 2015

Removal characteristics of Cu(II) ions by solid-phase extractant immobilized D2EHPA and TBP in PVC were investigated. Cu(II) ion concentrations in the solution and removal capacity of Cu(II) ion according to operation time were compared. The lower the initial concentration of Cu(II) ion in aqueous solution was, the removal capacity of Cu(II) ion by solid-phase extractant was increased relatively. The bigger the initial concentration of Cu(II) ion was, the removal capacity of Cu(II) ion was increased relatively. The pseudo-second-order kinetics according to operation time was showed more satisfying results than the pseudo-first-order kinetics for the removal velocity of Cu(II) ion. The removal capacity of Cu(II) ion was 0.025 mg/g in aqueous solution of pH 2, but the removal capacity of Cu(II) ion was increased to 0.33 mg/g mg/g in aqueous solution of pH 4 according to increasing pH.

• Journal of Environmental Science International
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• v.30 no.1
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• pp.69-76
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• 2021

The purposes of this study were to evaluate the removal characteristics of COD, Ni, and P and to derive appropriate operating conditions for the plating wastewater according to NaOCl reaction time and pH operating conditions in the BPC unit process during the plating wastewater treatment process. As a results of evaluating the removal characteristics for raw wastewater by each BPC unit process, the removal efficiencies of COD, Ni and P in BPC 1-1 unit process were 72.8%, 99.1%, and 100.0%. Therefore, the proper reaction time of NaOCl was derived as 21.1 minutes. In order to maintain the +800 mV ORP and the reaction time of 20 minutes, the temporary injection and continuous injection of NaOCl in the BPC unit process were 13.7 mL and 18.7 mL, respectively. It was found that the temporary injection method of NaOCl reduced the chemical cost by 36.5% compared to the continuous injection method. Also, Ni showed the highest removal efficiency of 97.8% at pH 10.5. On the other hand, P showed a removal efficiency of 57.4% at pH 10.0.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.135-145
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• 2011

This study was conducted to analyze the cost effectiveness in line with total phosphorus standard enforcement of public sewage treatment facilities. The additional cost for the total phosphorus removal process was calculated to analyze the cost effectiveness of the advanced water purification process. The analysis results showed that the T-P removal by coagulation sedimentation was more efficient than the advanced water purification facilities in terms of facilities investment cost, and if the coagulation filteration was used for T-P removal, the activated carbon process among the advanced water purification techniques was more efficient in terms of facilities investment cost. In this study, the effects of the T-P removal process that will be additionally introduced according to the tightening of the effluent T-P standard were analyzed within a limit. The actual benefits of improved T-P concentration in the water source will provide diverse values, including the leisure water, environment improvement water, eco-system in the water source and industrial water, in addition to the advanced water purification.