• Clean Technology
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• v.24 no.4
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• pp.315-322
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• 2018

Industrial use of waste oyster shells is limited because of requiring excessive energy for converting natural oyster shells in the form of calcium carbonate ($CaCO_3$) into calcium oxide (CaO) for this purpose. This study aimed to develop energy-saving process for producing solidifying agent using waste oyster shells for backfill materials. It was suggested that oyster shells were converted to calcium sulfates which were mixed with sodium hydroxide solution and red clay, forming solid specimen. The optimal concentrations of sulfuric acid for sulfation of oyster shell and sodium hydroxide to generate calcium hydroxide ($Ca(OH)_2$), were determined. Unconfined compressive strength of solid specimen increased with increasing the content of solidifying agent while it increased also with increasing ratio of natural oyster shells to coal ash. The result clearly demonstrates that solidifying agent consisting of sulfuric acid-treated oyster shell, coal ash, and sodium hydroxide solution, can be effectively utilized for preparing backfill materials using natural oyster shell and coal ash. Sulfuric acid-treated oyster shell-based solidifying agent has not been previously developed and will contribute to broaden industrial application of waste oyster shells.

• Journal of Food Hygiene and Safety
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• v.13 no.1
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• pp.14-19
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• 1998

The residual tissue concentraion of the widely used aquatic antibacterial agent, oxolinic acid, was surveyed in eels collected from fish markets of Chonbuk Province, Korea. Their concentrations in the dorsolateral muscle were widely varying. In about 32% of samples examined, oxolinic acid was not detected. In about 16% of those samples in which oxolinic acid was detected, the concentration was above 0.1 ppm. The tissue distrubution of the agent in major organs was in the rank order of kidney>liver>plasma>muscle. When the muscle samples which contained residual oxolinic acid were baked for up to 10 min, there was no change in the drug concentration. Their concentration declined to about 50% by baking for 30 min at which time the tissue turned to the texture of charcoal. The extreme stability of oxolinic acid to heating process was confirmed with muscle samples from eels to which a high dose of oxolinic acid was administered, and also with an aqueous oxolinic acid solution of known concentration. It is suggested that an effective regulatory measure should be initiated to keep eel consumers from residual oxolinic acid impact.

• Resources Recycling
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• v.18 no.5
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• pp.44-51
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• 2009

Fundamental study has been made on the recovery of copper from the electronic scrap by hydrometallurgical process. Nitric acid was used as a leaching agent to dissolve the metals such as Cu, Sn, Pb, Fe etc. from the crushed electronic scraps. TBP was employed to extract nitric acid from the strong nitric acid leaching solutions and to reclaim nitric acid. From the experimental results, Cu was effectively leached by 3.0-4.0 M nitric acid. And 95% of nitric acid in the leaching solution was extracted by 60% TBP, and 98% of nitric acid was stripped from the loaded organic phase by distilled water and it was possible to reuse as a leaching agent.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.402-405
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• 2001

The production of fumaric acid in shaken flask cultures by Rhizopus oryzae KCTC 6946 was studied. The effects of various carbon and nitrogen sources on fumaric acid production were investigated. The strain fermented starch (or glucose) and corn steep liquor (or polypepton) better than other carbon and nitrogen sources to fumaric acid. When C/N ratio of carbon and nitrogen source was 41.7, the concentration of fumaric acid produced with 2N NaGH as a neutralizing agent was more than 10 g/L after 3 days.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2473-2478
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• 2010

Novel 1'-methyl-5'-norcarbocyclic adenosine phosphonic acid analogues were synthesized using an acyclic stereoselective route from commercially available 3,3-diethoxy-propan-1-ol 4. The synthesized nucleoside phosphonate 19 and phosphonic acid 21 were subjected to antiviral screening against various viruses.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.199-202
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• 2004

In this study the field-scale tests were performed in which in-situ E/K remediation technologies were applied, and then the results were present. For traditional E/K remediation method the efficiency of remediation is not large, but the enhanced method with citric acid significantly increases the removal efficiency. Also EDTA, reported as a good enhancement agent for removal of heavy metals, is similar to that of citric acid. Therefore citric acid is preferred rather than EDTA in view of the cost on the contaminant removal per unit concentration.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.58-65
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• 1998

Substituted dicyandiamide(Sub-DICY), Accelerated dicyandiamide(Acc-DICY), Trimellitic anhydride(TMA), Pyromellitic dianhydride(PMDA) and Phenolic curing agent(Ph.C.A.) are mainly used for epoxy powder coating curing agent. Various characteristics of epoxy films fully cured by optimum condition such as mechanical properties like $T_g$, tensile strength, elongation at break hardness, abrasion resistance and chemical properties like water absorption, acid resistance, alkali resistance and electrical properties, corrosion resistance are determined by various measuring devices and analyses devices. In conclusion, phenolic curing agent was shown excellent thoughness but severe color change as temperature increased. Acid anhydride has excellent insulation properties and color stability at elevated temperature but lower thoughness and adhesion to substrate. DICY curing agent was shown high water absorption and severe color chance as temperature increased.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.1 no.1
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• pp.31-37
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• 2015

Chelating agents 1,4,7-triazacyclononanetriacetic acid (NOTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and 30-amino-3,14,25-trihydroxy-3,9,14,20,25-penta-azatriacontane-2,10,13,21,24-pentaone (desferrioxamine, DFO) were labeled with $^{68}Ga$ and tested in vitro properties to check the feasibility of using DFO as a bifunctional chelating agent or renal imaging agent. The chelating agents of concentration $2{\mu}M$ were labeled with $^{68}Ga$ in 0.1 M HCl at pH 1.7-10.3 at room temperature and $80^{\circ}C$ and the optimal pH for labeling each chelating agent was found. And then, the chelating agents were labeled with $^{68}Ga$ in various concentration of chelating agents at optimal pH. The labeled chelating agents were subject to stability test in human serum and to binding studies to human red blood cell (RBC) and plasma protein. The optimal pH's of NOTA, DOTA and DFO for $^{68}Ga$-labeling were 4.4, 3.6 and 5.6, respectively. DFO ($10{\mu}M$) showed high labeling efficiency (>97%) at pH 5.6. All the labeled chelating agents showed high stability in human serum. $^{68}Ga$-DFO showed low RBC binding but significant amount was bound to plasma protein. The results demonstrated that $^{68}Ga$-DFO can be used as a bifunctional chelating agent but not as a renal imaging agent.

• Journal of Adhesion and Interface
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• v.10 no.4
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• pp.182-190
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• 2009

In this work, effect of antistrip additives to reduce moisture damage of asphalt mixture were studied. Asphalt antistripping agents were prepared by condensation of formaldehyde with tetraethylene pentamine (TEPA), triethylenetetramine (TETA) and bis(hexamethylene)-triamine (BHMT), respectively. And also the metal type antistripping agent was prepatred by neutralization of stearic acid or palmitic acid with metal hydroxide. Mechanical characteristics of the asphalt mixture added antistripping agent were evaluated with Marshall stability, submerging residuals and coating rate. It was found that antistripping agent prepared in this study reduced moisture damages of asphalt mixtures. In particular, asphalt mixtures added BHMT and C/S (Calcium stearate hydroxide) antistripping agent showed highest submerging and coating rate. Because BHMT and C/S type antistripping agent was to improve bonding between asphalt and aggregate owing to increase of amine concentration and role of metal surfactant.

• The korean journal of orthodontics
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• v.20 no.3 s.32
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• pp.583-591
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• 1990

If the bond strength is sufficient to resist orthodontic force, orthodontic brackets can be bonded to restorations. Orthodontic brackets were bonded to composite resin and glass ionomer cement restorations with no-mix adhesive or glass ionomer cement. The shear bond strength of adhesives bonded to restorations was studied in vitro. Orthodontic brackets were bonded to 10 extracted natural teeth, 40 composite resin restorations and 40 glass ionomer restorations. The surfaces of composite resin restorations were roughened or applied with bonding agent (Scothbond) after surface roughening. The surfaces of glass ionomer cement restorations were conditioned with acid etching or applied with Scotchbond to etched surface. The adhesive was no-mix resin or glass ionomer cement. The shear bond strength was measured. The results were as follows: 1. Orthodontic brackets could be bonded to composite resin restorations effectively as they could be bonded to acid etched enamel with no-mix adhesive. The shear bond strength was sufficient to resist orthodontic force and was not affected by bonding agent greatly. 2. The shear bond strength of no-mix adhesive bonded to acid etched glass ionomer cement restorations was sufficient to resist orthodontic force. However. the fracture risk of glass ionomer cement restorations was increased during debonding. The bonding agent couldn't increase the shear bond strength greatly. 3. The shear bond strength of glass ionomer cement bonded to glass ionomer cement restorations was lower than that of no-mix adhesive. The shear bond strength was sufficient to resist orthodontic force and was greatly decreased by bonding agent. 4. The shear bond strength of glass ionomer cement bonded to composite resin restorations was too low to resist orthodontic force.