• Restorative Dentistry and Endodontics
• /
• v.24 no.1
• /
• pp.156-165
• /
• 1999

The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength between new and old composites. Circular cavities prepared on the center of acrylic resin mold and the prepared cavities were filled with composite resin. They randomly assigned into control group and 8 groups according to the difference in surface treatments of old composites; Control group: no surface treatment, Group 1: surface treated with #120 SiC paper & bonding agent, Group 2: surface treated with #400 SiC paper & bonding agent, Group 3: surface treated with #120 SiC paper, 32% $H_3PO_4$ & bonding agent, Group 4: surface treated with #400 SiC paper, 32% $H_3PO_4$ & bonding agent, Group 5: surface treated with #120 SiC paper, primer & bonding agent, Group 6: surface treated with #400 SiC paper, primer & bonding agent, Group 7: surface treated with #120 SiC paper, 32% $H_3PO_4$, primer & bonding agent, Group 8: surface treated with #400 SiC paper, 32% $H_3PO_4$, primer & bonding agent. New composites were applicated on the old composites of experimental groups. The shear bond strengths for the experimental specimen were measured and the results were analyzed by using one way ANOVA. The observations of surface morphology after SiC paper roughening and debonded surface morphology after shear bond strength test were done by SEM. The results were as follows; 1. Shear bond strengths for specimens roughened with #120 SiC paper matching with the particle size of coarse diamond bur were significantly higher than those for the specimens with #400 SiC paper(P<0.05). By SEM, the surface of the specimens roughened with #120 SiC paper was more irregular than the specimens with #400 SiC paper. 2. Shear bond strengths for specimens treated with 32% $H_3PO_4$ etchant, primer, bonding resin were significantly higher than those for specimens treated with 32% $H_3PO_4$ and bonding resin(P<0.05). 3. Shear bond strengths for the specimens treated with 32% $H_3PO_4$ etchant and bonding resin were significantly higher than those for specimens treated with only bonding resin(P<0.05). There was no remarkable change of surface morphology after 32% $H_3PO_4$ etching. 4. It was possible to observe mixed fracture patterns (the cohesive fracture of old composite and the adhesive fracture between old and new composite) in the specimens roughened with #120 SiC paper, but almost adhesive fracture in the specimens roughened with #400 SiC paper.

• Journal of Environmental Science International
• /
• v.32 no.10
• /
• pp.731-739
• /
• 2023

In this study, lab-scale phosphorus coagulation/precipitation experiments were performed using three types of polyaluminum chloride (PAC) with different Al contents (10%, 12%, and 17%). The PO₄-P removal efficiencies at various operating conditions, such as initial PO₄-P concentration, initial pH, and Al/P molar ratio, were evaluated, and correlations among the operating factors affecting phosphorus coagulation/precipitation with PAC were derived to optimize the process efficiency. When the initial PO₄-P concentration was 0.065 and 0.161 mmol P/L under an initial pH of 8-10, the optimal PAC dose was 0.126-0.378 and 0.189-0.667 mmol Al/L, respectively. Under these conditions, the Al/P molar ratio was 2.16-6.18 and 1.28-4.30, respectively, and the PO₄-P removal efficiency was in the range of 40.2-92.5%. When the Al/P molar ratio was 2 or less under an initial pH condition of 6-8, the PO₄-P removal efficiency was approximately ≤40% owing to insufficient Al³⁺ ions. However, when the Al/P molar ratio is 3-5, the PO₄-P removal efficiency improved to approximately 80-90%. Thus, the optimal Al/P molar ratio to achieve a PO₄-P removal efficiency of over 90% was determined to be approximately 4 in the PO₄-P coagulation/precipitation process using PAC.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.9
• /
• pp.879-886
• /
• 2010

This study investigated the removal characteristics of highly concentrated $NH_4$-N and $PO_4$-P by struvite crystallization using converter slag as a seed crystal. The optimal pH range for removal and recovery of $NH_4$-N and $PO_4$-P by struvite crystallization was measured to be 8.0~8.75, in which total removal efficiencies for $NH_4$-N and $PO_4$-P by struvite precipitation and crystallization were 34.3~61.0% and 91.0~96.2%, respectively. The maximum removal efficiencies for $NH_4$-N and $PO_4$-P by struvite crystallization were 29.4% at pH 8.5 and 65.1% at pH 8.0, respectively. The removal efficiency of $NH_4$-N by struvite crystallization decreased with increasing calcium ion concentration. The analysis results of SEM, EDS and XRD exhibited that $NH_4$-N and $PO_4$-P in meta-stable region of struvite crystallization could be eliminated through formation of magnesium ammonia phosphate (MAP) and hydroxyapatite (HAp) on seed crystals by struvite precipitation and crystallization.

• Korean Journal of Food Science and Technology
• /
• v.21 no.5
• /
• pp.619-623
• /
• 1989

The cultural condition of Pseudomonas mendocina for polysaccharide production was examined. The optimal medium contains following composition per liter of distilled water: Sucrose 23.75g, $(NH_4)_2SO_4$ 1.57g, Yeast extract 0.5g, $KH_2PO_4\;2.9g,\;MgSO_4.\;7H_2O\;1.0g,\;CaCO_3$ 2.5g. The optimum temperature and pH were $30^{\circ}C$ and 6.5. At the condition. Ps mendocina produced 5.98g/l of polysaccharide. The culture viscosity after 3 days was 191mPa.s at $70sec^{-1}$. The product yield $(Y_{p/s})$ and specific productivity $(Q_p)$ were 25.18% and 32.83mg/g-cell/h.

• The Korean Journal of Pesticide Science
• /
• v.21 no.1
• /
• pp.26-32
• /
• 2017

Antimicrobial activity of 6 phosphate compounds as $H_3PO_3$, $H_3PO_4$, $K_3PO_4$, $K_2HPO_4$, $KH_2PO_4$ and $NH_4H_2PO_4$ against Phytophthora capsici JHAW 1-2 and Colletotrichum acutatum JC24 was investigated in this study. Inhibitory effect on zoospore release, zoosporangia germination and zoospore germination was superior than mycelial growth. Among 6 compounds, $H_3PO_3$ and $H_3PO_4$ showed the best antimicrobial activity against P. capsici JHAW 1-2. Diseases controlling activity of the phosphate compounds tested on seedling and fruit of pepper against Phytophthora blight was also better than those against anthracnose. When $H_3PO_3$ was applied to the pepper seedlings at a concentration of $100{\mu}g\;mL^{-1}$, severe phytotoxicity was occurred. However, with applying $10{\mu}g\;mL^{-1}$ of $H_3PO_3$ showed 100% the disease control efficacy. In case of $100{\mu}g\;mL^{-1}$ $H_3PO_4$ application showed excellent antimicrobial activity against P. capsici JHAW 1-2, and 56.7% of the disease control efficacy with no phytotoxicity. To investigate the control efficacy against anthracnose, conidia suspension was inoculated with non-wound and wound inoculation method on pepper fruit. Among 6 compounds, only $100{\mu}g\;mL^{-1}$ of $H_3PO_3$ and $H_3PO_4$ had a activity of more than 70%, but the control activity on other treatments was minimal or unacceptable.

• Journal of the Korean Chemical Society
• /
• v.49 no.2
• /
• pp.161-166
• /
• 2005

• Bulletin of the Korean Chemical Society
• /
• v.26 no.7
• /
• pp.1035-1036
• /
• 2005

• Korean Journal of Ecology and Environment
• /
• v.37 no.1 s.106
• /
• pp.78-86
• /
• 2004

In order to reveal the relationship between the concentration of chlorophyll- a and the environmental factors affecting eutrophication, the present study was biweekly conducted at G stations in the lower part of the Han river during the period from Feb. 24,2001 to Feb. 9,2002. Water temperature was changed from $0.5^{\circ}C$ to $26.4^{\circ}C$, pH was 5.77${\sim}$8.99, DO 3.15${\sim}$14,36 mg $L^{-1}$, BOD 0.90${\sim}$7.45 mg $L^{-1}$, and COD 1.16${\sim}$9.13 mg $L^{-1}$. TN and TP were ranged from 1.68${\sim}$20.96 mg $L^{-1}$, and 0.02 ${\sim}$ 1.17 mg $L^{-1}$, respectively. $NH_4\;^+$-N, $NO_3\;^-$-N, and $PO_4\;^{3-}$-P were ranged from 0.56${\sim}$3.60 mg $L^{-1}$, 0.03${\sim}$7.29 mg $L^{-1}$, and 0.002${\sim}$0.754 mg $L^{-1}$. Chlorophyll- a was extensively changed from 2.29 ${\mu}g\;L^{-1}$ to 136.28 ${\mu}g\;L^{-1}$ by month and stations. Results of nutrients indicated the eutrophic level in this area and water quality was the gradual worsening in the lower stations than those of upper stations during the period studied. The Pearson correlation analysis between the concentration of chlorophyll- a and the environmental factors indicated that BOD, COD, pH, $NH_4\;^+$-N, TP, TN, conductivity and $PO_4\;^{3-}$-P were positive correlation, but $NO_3\;^-$-N was negative. The environmental factors investigated using the principal component method could be triparted. The first factor group included conductivity, BOD, COD, TN, TP, $NH_4\;^+$-N, $PO_4\;^{3-}$-P and SS, the second WT and DO, and the third pH and $NO_3\;^-$-N. Using the stepwise regression analysis, chlorophyll- a was under the influence of conductivity, $PO_4\;^{3-}$-P, $>NO_3\;^-$-N and $NH_4\;^+$-N Chlorophyll-a = 0.3661 ${\times}$ (Conductivity) - 0.3592 ${\times}$ ($PO_4\;^{3-}$-P) - 0.3449 ${\times}$ ($NO_3\;^-$-N)+0.4362 ${\times}$ ($NH_4\;^+$-N.

• Applied Biological Chemistry
• /
• v.43 no.3
• /
• pp.163-168
• /
• 2000

To remove phosphate accumulated in the soil and water, Acinetobacter lwoffi PO8 possessing a high ability to accumulate phosphate was isolated from a active sludge. Bacterium was cultured in the liquid medium containing $150\;{\mu}g/mL$ of phosphate at $30^{\circ}C$ in different culture conditions to examine intracellular phosphate uptake. The initial pH in the range of $7.5{\sim}8.5$ was effective on the growth and phosphate uptake of the strain. Glycerol and arabinose used as a carbon sources showed 93 and 91% the phsphate uptake, respectively. Among the nitrogen sources, ammonium salt such as $NH_4NO_3$ and $(NH_4)_2SO_4$ was effectively utilized on the phosphate uptake compared with amino compounds. The rate of phosphate uptake of $NH_4NO_3$, and $(NH_4)_2SO_4$, was 95 and 96%, respectively The growth and Phosphate uptake ability in the strain were significantly promoted when metal ions were added in the medium; $Co^{2+}$, however, was not utilized by the strain. The capacity of phosphate uptake was enhanced to $10{\sim}20%$ when arginine, methionine, or lysine was added. Using $^{32}P$ to examine the uptake Pattern of intracellular phosphate, experiment result showed that polyphosphate was largely found in the fraction of intracellular inorganic phosphate of Acinetobacter lwoffi PO8.

• Journal of the Korean Chemical Society
• /
• v.49 no.4
• /
• pp.381-388
• /
• 2005