• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.85-94
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• 2002

Overall objective of this study was to evaluate the electrochemical characteristics of fine soils during the electrokinetic(EK) remediation. Zeta potential of kaolinite as a function of solution pH and surfactant concentration was investigated to make a relationship with electroosmotic flow direction and rate. During the EK experiments, pH of pore solution, electroosmotic permeability($k_e$), electric conductivity($\delta_e$) and voltage distribution was measured, respectively, The point of zero charge(PZC) of kaolinite was estimated to be about 4.2 and the zeta potential of kaolinite above PZC was more negative as solution pH increased. Sorption of surfactants on the kaolinite altered the zeta potential of kaolinite. resulting from the variation of electrochemical characteristics of kaolinite surface. hs the EK experiment progressed, low pH was predominant over most of the kaolinite specimen and thus resulted in very low mass and charge flow. The $k_e$ and $\delta_e$ was also affected by the variation of voltage drop across the EK column with time. Results from this study implied that zeta potential of kaolinite affected by the pH variation of pore solution and voltage distribution in soil column played important role in the determination of mass and charge flow during EK process. It was also suggested that pH adjustment or addition of suitable sorbates could alter the electrochemical characteristics of soil surface and thus maintain high mass and charge flow rate with time.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.305-314
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• 1989

Effect of pH variation in starting solution for the making of hydroxyapatite powder was studied in relation to the sinterability of the powder and their mechanical properties of the sintered hydroxyapatite ceramics. The sinterability of hydroxyapatite powder prepared at different pH was found to be improved with increase in pH value of the starting solutions. Thus the powders prepared from the higher pH solutions including 10.5, 11.0 and 11.5 could be well densified almost upto theoretical density by firing for 1 hr at 1,00$0^{\circ}C$. But the powder based on pH 10 exhibited less sinterability even being fired at much higher temperature of 1,10$0^{\circ}C$, it gave only 90-95% of theoretical density. On the other hand the powder prepared on the lowest pH value 9.5 could not be well densified and it could obtain only 78% of theoretical density even by firing at 1,30$0^{\circ}C$ for 1hr. It was found that prismatic crystals of whitlockite were always included in the sintered bodies based on the lower pH values as a minority crystalline phase together with the major crystalline phase of hydroxyapatite and its inclusion might impair the sinterability of powder. However in the case of the higher pH, the powder contained only hydroxyapatite as a crystalline phase on sintering without any minorities. The sphere shape of crystals might help effectively the densification of the bodies. The best mechanical properties could be obtained from the body of pH 11 sintered at 1,10$0^{\circ}C$, which gave 99.5% of theoretical density, 662Kg/$\textrm{mm}^2$ of vickers hardness and 1,352Kg/$\textrm{cm}^2$ of diameteral compression strength.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.1
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• pp.96-101
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• 1998

Substrate inhibition of 2,4-dinitrophenol (DNP) degradation was investigated using activated sludge which had been adapted to mineralize DNP. DNP is a metabolic uncoupler, preventing cells from making energy for growth and it has been suggested that pH may be important in mitigating effects of uncouplers. After acclimation of the activated sludge, the effect of pH on toxicity of DNP at high concentration (75 mg/L) was investigated, over a pH range of 5 to 9. DNP inhibition was found to be strongly dependent on mixed liquor pH. The DNP degradation rate was highest in the pH range of 6.95 to 7.84; at pH 5.94 degradation of 75 mg/L DNP was significantly inhibited; at pH < 5.77, DNP degradation was completely inhibited after approximately 30% of the DNP was degraded. By comparison, no significant effect of pH variation in the same range was seen on glucose uptake by the activated sludge culture.

• Journal of Environmental Science International
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• v.5 no.5
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• pp.663-676
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• 1996

The analyzed results of observed precipitation and its pH in Kwangiu for 262 days from fan. 1, 1991 to Dec. 31, 1995 are as follows. The annual mean pH was 5.7, and the monthly mean pH values of January-May and November were less than 5.6 in Kwangiu. The ratio of acid rain for these periods was about 48.1%, almost half that of the total observed days. In March, the pH was 5.4 and the ratio of acid precipitation was 69%, an especially serious situation. In the spring, the pH value was 5.5, thus weakly acidic. The pH of precipitation tended to decrease with greater precipitation. The relation between persistent time and pH of precipitation is variable, but if the persistent time is long, the pH is constant and low. It is fortunate that there is an increasing trend of pH in interannual variation, but it is thought important that the amplitude of variation of pH in 1995 was high and the pH value was 4.1 in October and November. Because heavy and persistent precipitation effects the accumulation of acidity, more concern about acid rain is needed.

• Journal of Food Hygiene and Safety
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• v.9 no.4
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• pp.185-189
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• 1994

This study was to investigate time-dependent degradation process under various pH condition for organophosphorus(org-p) insecticides, namely Demeton-s-methyl, diazinon, Parathion, Phenthoate, and EPN in several waters. They were analysed by GC-FTD according to standard methods for the examination of water and wastewater. In pH=4, diazinon showed disappearance after 14 days in chromatogram. In pH=11, org-p insecticides were almost degradable after 7 days. In this condition, effect of pH on degradation process was greater than of light. In pH=7, org-p insecticides persisted residues after 112 days except Demeton-s-methyl. In BOD5 120, 250 ppm and domestic water, org-p insecticides showed also rapid degradation process.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1435-1438
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• 1994

The effects of Ge composition variation in $a-Si_{1-x}Ge_x:H$ alloy p-i-n solar cells on the physical properties and current density-voltage characteristics are analyzed by a new simulation modelling based on the update published experimental datas. The simulation modelling includes newly formulated density of gap density spectrum corresponding to Ge composition variation and utilizes the newly derived generation rate formulars which include the reflection coefficients and can apply to multijunction structures as well as single junction structure. The effects in $a-Si_{1-x}Ge_x:H$ single junction are analyzed through the efficiency, fill factor, open circuit voltage, short circuit current density, free carriers, trap carriers, electric field, generation rate and recombination rate. Based on the results analyzed in single junction structure, the applications to multiple junction structures are discussed and the optimal conditions reaching to a high performance are investigated.

• Journal of Convergence for Information Technology
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• v.12 no.3
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• pp.132-140
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• 2022

This study was conducted to identify the optimal lotion manufacturing conditions with decursin and decursinol angelate of Angelica gigas Nakai extraction. Lotion was confirmed that it had viscosity (5,208±112 cPs), assay (99.71±1.01%), and pH (5.62) for 3 months. The optimization of manufacturing conditions of mixing 4 for lotion formulation were made by 22+3 full factorial design. Mixing temperature (40-80℃) and mixing time (10-30 min) were used as independent variables with three responses(assay, pH, and weight variation) as critical quality attributes (CQAs). The model for assay and weight variation identified a proper fit having a determination coefficient of the regression equation (about 0.9) and a p-value less than 0.05. Estimated conditions for the optimal manufacturing process of lotion were 61.93℃ in mixing temperature and 15.85 min in mixing time. Predicted values at the mixing temperature (60℃) and mixing time (20 min) were 100.69% of assay, 5.57 of pH, and 98.07% of weight variation. In the verification of the actual measurement the obtained values showed 100.29±0.98% of assay, 5.57±0.02 of pH, and 98.27±0.89% of weight variation, respectively, in good agreement with predicted values.

• Restorative Dentistry and Endodontics
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• v.29 no.3
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• pp.249-266
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• 2004

The purpose of this study was to determine whether pH and time has any influence on the degradation behavior of composite restoration by analyzing the leached monomers of dental composites qualitatively and quantitatively after storage in acetate buffer solution as a function of time using high performance liquid chromatography (HPLC) / mass spectrometer. Materials and Methods：Three commercial composite restorative resin materials (Z-250, Heliomolar and Aeliteflo) with different matrix structure and filler composition were studied. Thirty specimens (7mm $diameter{\times}2mm$ thick) of each material were prepared. The cured materials were stored in acetate buffer solution at different pH (4, 7) for 1, 7 and 45days. As a reference, samples of unpolymerized composite materials of each product were treated with methanol (10mg/ml). Identification of the various compounds was achieved by comparison of their mass spectra with those of reference compound, with literature data. and by their fragmentation patterns. Data were analysed statistically using ANOVA and Duncan's test. Results：1. Amounts of leached TEGDMA in Aeliteflo were significantly larger than those of UDMA in Z-250 and Heliomolar at experimental conditions of different storage time and pH variation (p<0.001). 2. As to comparison of the amounts of leached monomers per sorage time, amounts of leached TEGDMA in Aeliteflo and UDMA in Z-250 and Heliomolar were increased in the pH 4 solution more significantly than in the pH 7 solution after 1day, 7days and 45days, respectively (p<0.001). 3. In total amounts of all the leached monomers with storage times, the overall amounts of pH 4 extracts were larger than those of pH 7 extracts for all resin groups, but there was no significant difference (p>0.05).

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.267.2-267.2
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• 2013

In the citrate reduction method of gold nanoparticle (AuNP) synthesis, pH of the reaction mixture can have a considerable impact on the size and size distribution of AuNPs. In this work, effects of pH variation upon the size and its distribution were examined systematically. As the initial pH was change from 5.5 to 10.5, it showed an optimal pH around 7.5. At this pH, both of the size and the size distribution showed their minimum values, which was verified by transmission electron microscopy and UV-vis spectroscopy. This occurrence of optimal pH was discussed with the results of in situ monitoring pH during the reaction of AuNP synthesis.

• Journal of Environmental Health Sciences
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• v.14 no.1
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• pp.47-53
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• 1988

This study was performed to investigate a seasonal and vertical variation of the nutrients, water temperature, pH, DO, BOD, COD in Sukchon lake from May 1985 to Jan. 1986. The results were as follows. 1. Vertical descent of water temperature was the remarkable situation on Jul. and difference between surface layer and bottom layer was 3.5$\circ$C. 2. The value of pH was average 8.0 in both lake. The value of pH in the winter was average 7.6, and Summer was average 8.3. 3. The contents of dissolved oxygen was the highest value (13.0mg/l in surface layer on Jan. and the lowest value (8.1mg/l in bottom layer on Ul. 4. The contents of PO$_4$-P, NH$_3$-N, NO$_3$-N and T-N were 0.03~O.17mg/l 0.12~0.34mg/l 0.36~0.91mg/l and 0.76~1.37mg/l respectively.