• YAKHAK HOEJI
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• v.34 no.3
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• pp.161-165
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• 1990

An automated, simple, and reliable method was developed for determining in vitro drug release rate from transdermal delivery dosage forms. The patch is held in position in the heating block by sandwiching it between the middle plate and the bottom plate of diffusion cell. The dissolution profile of the commercially available transdermal scopolamine patch was determined over a 72-h period, and the results were compared with those obtained with other methods; paddle-over-disk method, reciprocating method, and diffusion cell method. It was demonstrated that the flow-through method is equivalent in terms of release rate profile and accumulated released drug amount over the lifetime of the dosage form tested. Also this method is simple, reliable and reproducible. Therefore, this technique can be used in a quality control for assuring product uniformity.

• Journal of Pharmaceutical Investigation
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• v.26 no.2
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• pp.119-124
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• 1996

To develop oral controlled release dosage forms, ionic interactions between polymers and drugs were evaluated. Hydroxypropylmethyl cellulose and carboxymethylene were used as model nonionic and ionic polymers, respectively. 5-fluorouracil, propranolol-HCl and sodium salicylate were selected as model nonionic, cationic and anionic, respectively. Polymer-drug mixtures were compressed into tablets and drug release kinetics from these tablets were determined. Drug release from the tablets made of the nonionic polymer was not affected by the charge of drugs, rather, was regulated by the solubility of drugs in different pH releasing media. However, drug release kinetics were significantly affected when drug-polymer ionic interactions exist. Enhanced drug release was observed from anionic drug-anionic polymer tablets due to ionic repulsion, whereas drug release was retarded in cationic drug-anionic polymer tablets owing to ionic attractive force. Therefore, the results suggested that the polymer-drug interactions are important factors in designing controlled release dosage forms.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.9-14
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• 2008

The cracking problem in concrete is widespread and complex. This paper reviews the problem and focuses on those parts of the problem that are more readily solved. Polymer fibers are shown to have promise in several important areas of the cracking problem. To investigate one of these areas of the cracking problem more completely, an experimental research program focusing on the early-age properties of fibers was carried out. This study researched the properties of four polymer fibers; two of the fibers were macrofibers, and two were microfibers. Each fiber was tested at several dosage rates to identify optimum dosage levels. Early-age shrinkage, long-term shrinkage, compressive strength, and tensile strength were investigated. Long-term shrinkage and strength impacts from the polymer fibers were minimal; however, the polymer fibers were shown to have a great impact on early-age shrinkage and a moderate impact on early-age strength.

• Advances in concrete construction
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• v.11 no.4
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• pp.323-333
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• 2021

The main objective of this study is to characterize and evaluate the hydrophobic performance of polymer-based water-repellent coatings on cementitious mortar surfaces. Different concentrations of poly(vinyl acetate) (PVAc) and poly(1,4-butylene adipate) (PBA) were prepared in the laboratory and their applicability and performance was tested experimentally by water absorption test and analysis of surface contact angles of cementitious mortar specimens. According to the results of this study, it can be stated that incorporation of nano polymer particles on the surface of cementitious mortar specimens can enhance contact angles and reduce water absorption by increasing hydrophobicity. However, a dosage limit exists for polymer materials in coating, and observed hydrophobic improvements decreases when polymer dosage reached beyond the limit. Additionally, it is observed that water absorption of polymer coated cementitious mortars is closely related with the results of surface contact angle.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.617-626
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• 2006

Compared with the sludge from gravity sedimentation, it is difficult for operations to settle the sludge occurred from dissolved-air-flotation (DAF). Even though there are some problems in treating DAF sludge with conventional gravity thickeners, those has been used until now. In this study, Solid Flux theory for gravity thickening was applied to the Solid Flux of DAF sludge through flotation in order to develop new methodology for treatment of DAF sludge. Also, characteristics of DAF sludge were investigated. From the experiment results, it was revealed that the higher the polymer dosage, at fixed the solid concentration, the greater the rising velocity becomes. When we applied solid flux theory, the relationship, which is similar to that of gravity thickening, has been achieved. Also, we could find the proper polymer dosage from the rising velocity is about 50 mg/L. Consequently, the limiting solid flux can be derived from the relationship between the total solid flux and the withdrawal velocity of DAF sludge. Furthermore, the factors, such as solid concentrations, bubble volume, pH, zeta potential, and temperature, have effects on the flotation and sedimentation for DAF sludge treatment.

• Journal of Environmental Health Sciences
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• v.33 no.1 s.94
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• pp.68-74
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• 2007

The objective of this study is to examine the effect of the coagulation and homogenization in bulking sludge thickening of paper manufacturing plant using DAF(Dissolved Air Flotation) and gravitational sedimentation. The effects of parameters such as dosage of coagulant and homogenization time were examined. The results showed that DAF and sedimentation was affected aluminum sulfate and anion polymer coagulant differently. At the optimum dosage of aluminum sulfate, thickening efficiency of DAF and sedimentation process were increase 1.25 time and 2.02 time, respectively. At the optimum dosage of anion polymer coagulant, thickening efficiency of DAF process was increase 1.35 time, but thickening efficiency at sedimentation was 1.06 time. When anion polymer coagulant of 0.5 mg/l was added in DAF process, water content of sludge was decreased from 96.6% to 90.7% in dewatering process using Buchner funnel test device. After homogenization(20500 rpm, 10 min), Sauter mean diameter of sludge floc was decreased from 631 ${\mu}m$ to 427 ${\mu}m$, however increase of flotation efficiency by DAF was only 1.09 time.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.253-258
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• 2004

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. Intermittent aerobic digestion is an useful digestion technology and has many advantages like neutral pH, low installation cost and easiness to operation. The objectives of this study were to investigate the dewaterability of intemittent aerobic digestion sludge and to find the relationship between dewaterability and particle size distribution change under the conditioning of intermittent aerobic digestion sludge by cationic polyelectrolyte. Digested sludge from intermittent aerobic digestion was used and cationic polyacrylamide polymer was added as a conditioner. CST(capillary suction time), TTF(time-to-filtration) were tested as a dewaterability index and the number of particle distribution was analyzed using particle size analyzer. The results indicate that cationic polyelectrolytes is useful to enhance dewaterability of intermittent aerobic digestion sludge. Mean particle diameter was increased as polymer dosage increased and its value was reached up to 100 mm on the condition of optimal cationic polymer dosage. CST and TTF are well correlated with mean particle diameter when the weighting order is 1.7. By the optimal conditioning with cationic polymer, particles in the filtrate are also reduced significantly and this means that conditioning is helpful to main stream by reducing SS loading from return flow.

• Journal of Environmental Science International
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• v.7 no.2
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• pp.217-222
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• 1998

Organics matters including algae are the major contaminants of Nak-dong river and it's concentration Is more Increasing now. The use of coagulants has been Incresed for the effective treatment of drinking water, and aluminum coagulants have been the most widely used in raw water treatment. However, when inorganic metal coagulant is excessively used for long period, it would result in secondary problems, such as increasing sludge production, enhancing the cost of water treatment process, and increasing concentration of residual metal, especially aluminum. Therefore, recently. in order to reduce the use of metal coagulant and enhance the coagulation effectiveness, several alternative coagulants, such as polymeric Inorganic coagulants and organic polymers, have been used In water treatment plants. The objectives of thins research were (11 to determine optimum dosage concentration and compare the coajuiation efnciency at various pH ranees with alum alone, alum+cationic polymer, and alum+anlonlc polymer, (21 to evaluate the amount of alum reduced by using organic polymer, (31 to maximize removal officiency of organic matter and minimize the concentration of residual aluminum.

• Current Research on Agriculture and Life Sciences
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• v.27
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• pp.29-33
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• 2009

Liquefied-wood polymer composite was prepared and mechanical properties was evaluated to develop potential utility of liquefied wood. The liquefied wood was made from waste wood and chemical modified with acetic anhydride and maleic anhydride (MA), phtalic anhydride (PA). The composite sheet was prepared from modified liquefied-wood and polymer(PE). The mechanical, chemical and microscopical properties composite sheet were investigated. The results were summarized as follows, 1. The tensile strength was increased and breaking elongation of composite sheet was decreased with the time of acetylation and the dosage of MA. 2. The Young's modulus of composite sheet was gradually decreased with the dosage of PA. 3. The peak intensity of 1737cm-1 in FT-IR spectra of chemical modified liquefied woods was increased. 4. The dispersity of liquefied woods with PE was improved with chemical modification.

• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.370-375
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• 2004

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. When conditioning biological sludges, the charge on the polymer has a significant impact on the effectiveness of the polymer as a conditioner. The objectives of this investigation were to determine the most effective type and dosage of polymer for conditioning digested sludge prior to dewatering, and to investigate the relationship between dewaterability and particle size. 3 types of digested sludge were used under the different digestion processes like anaerobic digestion, aerobic digestion and intermittent aerobic digestion. CST(capillary suction time), TTF(time-to-filter) and SRF(specific resistance to filtration) were tested as a dewaterability index and the number of particle distribution was analyzed using particle size analyzer. The results indicate that cationic polymer appears to be required for effective conditioning of these 3 types digested sludge and the optimal polymer dosage is about 0.6% of SS. CST and TTF are well correlated with mean particle diameter of which the dimension order is 1.7.