• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.4
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• pp.757-761
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• 2004

The alginate extracted from Hizikia fusiform by the acid alkali soluble alginate (AASA) extraction method was reacted with Na$_2$SO$_4$. The amount of sulfate absorbed in the 3% alginate solution was determined about 18,435 ppm by inductively coupled plasma-atomic emission spectrometry. Both alginate and S-alginate stimulated the growth of Lactobacillus acidophilus in MRS broth and peptone water medium. The addition of S-alginate to the media showed the higher bacterial numbers than alginate supplement. There was no mutagenic activity of S-alginate in the Ames test using the Salmonella Typhimurium TA98 and TA100 strains. The S-alginate showed suppressive effect against 2-NF and MMS of mutagens.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.487-492
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• 2013

Transesterifications of waste oils mixed with animal tallows and vegetable oil by ultrasonic energy were examined over various catalysts for biodiesel production. Reaction activities of the transesterification were evaluated to the ultrasonic energy and thermal energy. The physicochemical properties of feedstock and products were also investigated to the biodiesels produced from the oils in the reaction using ultrasonic energy. The highest fatty acid methyl ester (FAME) yield was obtained on the potassium hydroxide catalyst in the transesterification by ultrasonic irradiation. The effective reaction conditions by ultrasonic energy were 0.5 wt% catalyst loading and 6:1 molar ratio of methanol to the mixed oils. The reaction rate of the transesterification by ultrasonic energy was faster than that by thermal energy. The highest yields of FAME were obtained as 80% in 5 min and the reaction equilibrium reached at that time.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1001-1009
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• 2000

This study is to find the utilization of intermittent aeration system, around S-COD, T-COD, SS, timewise changes of treatment performance, sludge conversion yield, changes of temperature and pH, etc. In consequence of this study, factors of temperature correction showed 1.052 on continuous aeration, and 1.056 on intermittent aeration which is more sensitive to temperature through a minute degree. Meanwhile, sludge conversion yield on intermittent aeration showed lower and more economical than that on continuous aeration. In case of changing pH, treatment water of both reactors worsened slightly in acid but improved in alkali. In general. considering the quality of effluent water, variation pH of effluent water, etc. the case of intermittent aeration was more favorable than that of continuous aeration.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.3
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• pp.75-86
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• 1991

Ion exchange strengthening is a chemical process whereby large alkali ions(such as potassium) are substituted for smaller ions(sodium) within the surfaces of glasses and ceramics, thereby reducing the thermal expansion coefficient of this surface region, and creating beneficial state of compressive stress within the near surface region. The purpose of this study was to determine the effects of ion exchange and etching treatments on the strength of some dental porcelains. Two feldspathic dental porcelains(Vitadur-N, G-Cera) were used in this study. A commercial ion exchange paste and etching gel containing 8% hydrofluoric acid were used for surface conditioning. Transverse strength was measured using a universal testing machine and the technique of EPMA(electron probe micro analysis) was used to access the potassium contents. The results were as follows: 1. Improvement in strength was only obtained by treating the surface placed in tension. 2. No changes in the dimensions of the treated specimens were detected when samples were measured with a micrometer. 3. There was significant increase in transverse strength of G-Cera IV group treated with etching and ion exchange, compared with G-Cera II group only treated with ion exchange. 4. From the results of EPMA test, increase in potassium contents was observed on the surface treated with ion exchange paste.

• International Journal of Ocean System Engineering
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• v.3 no.1
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• pp.33-37
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• 2013

Reinforced concrete structures have been increasingly widely used in numerous industrial fields. These structures are often exposed to severely corrosive environments such as seawater, contaminated water, acid rain, and the seashore. Thus, the corrosion problems that occur with the steel bars embedded in concrete are very important from the safety and economic points of view. In this study, the effects of the cover thickness on the corrosion properties of reinforced steel bars embedded in multiple mortar test specimens immersed in seawater for 5 years were investigated using electrochemical methods such as the corrosion potentials, polarization curves, cyclic voltammograms, galvanostat, and potentiostat. The corrosion potentials shifted in the noble direction, and the value of the AC impedance also exhibited a higher value with increasing cover thickness. Furthermore, the polarization resistance increased with increasing cover thickness, which means that the oxide film that is deposited on the surface of a steel bar surrounded by alkali environment exhibits better corrosion resistance because the water, chloride ions and dissolved oxygen have difficulty penerating to the surface of the steel bar with increasing cover thickness. Consequently, it is considered that the corrosion resistance of reinforced steel can be improved by increasing the cover thickness. However, the corrosion resistance values of a steel bar estimated by measuring the corrosion potential, impedance and polarization resistance were not in good agreement with its corrosion resistance obtained by polarization curves.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.1
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• pp.79-88
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• 2008

The production of bioethanol, which is one of the alternative fuel, cause the various problem such as agflation in human society. As a substitute for the feedstock, lignocellulosic biomass have a big potential. However, bioethanol production with cellulosic material is not commercialized due to high cost. Thermochemical pretreatment to improve the rate of enzyme hydrolysis and increase the recovery of fermentable sugar, is required in order to achieve the cost down in bioethanol production. In this study, various problems and technologies for pretreatment is introduced. Acid hydrolysis, alkali hydrolysis, steam explosion, organosolv process, ammonia explosion, and wet oxidation pretreatment remove lignin and hemicellulose, and reduce cellulose crystallinity. Optimization of pretreatment process on various sources of lignocellulosic biomass such as softwood, hardwood, and straw should be performed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.117-123
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• 2010

If FRP materials that have been known as high durability materials are exposed to harmful environmental factors, deterioration and characteristics of materials can be reduced due to chemical reaction such as hydrolysis. Therefore, to use FRP materials as building major materials, it is important to exactly grasp dynamic properties by use condition. Accordingly, this study stored FRP materials in a strong acid and alkali compound solution for a certain period to conduct simulation for acute or chronic, extreme changes by chemicals, and conducted a test for compressive, tensile, shear and bending strength to analyze changes in strength by kinds and storage days of chemicals. In conclusion, the study findings indicate excellent chemical resistance of FRP materials.

• Food Science and Preservation
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• v.5 no.4
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• pp.350-354
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• 1998

This paper was investigated to changes of cell components during drying for studies on the softening of jujube fruits. The contents of alcohol-insoluble material, cell wall and water-soluble material were not changed at 6 days of drying, but alcohol-insoluble materials and cell wall were decreased at 9 days of drying, however water-soluble materials were increased. Pectin and hemicellulose were not changed at 6 days of drying. Pectin and alkali-soluble hemicellulose were remarkable decreased at 9 days of drying, but acid-soluble hemicellulose was increased. Water-soluble pectin was not changed at 6 days of drying, but increased at 9 days of drying. EDTA-soluble and insoluble pectin were decreased after 6 days of drying. The non-cellulosic neutral sugars were not changed at 6 days of drying. The contents of arabinose, galactose and total neutral suger were decreased at 9 days of drying.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.187-193
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• 2019

Regarding physical absorption mechanism for fine particles(Dust), internal pore-bridging is a major parameter in porous media. In this paper, internal bridging pore system is invented through FA-based geopolymer and incorporated PLA (Polylactic Acid) fiber with biodegradability. With various mix proportions, compressive strength over 20MPa is obtained but PLA is little dissolved in the condition of NaOH 5mole and $30^{\circ}C$ of temperature, which was found that temperature rising accelerates PLA solubility. Within 24hours, beads type PLA is completely dissolved under $90{\sim}130^{\circ}C$ and NaOH 5~12mole of alkali. In room condition, geo-polymerization is limitedly occurs so that the internal pore after PLA dissolution is thought to be effective to absorption and storage of fine particles.

• Korean Journal of Plant Resources
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• v.12 no.4
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• pp.289-296
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• 1999

The availability of Bacillus polimyxa 'HB 26-5' as a biological control agent was investigated. The antagonistic bacteria Bacillus polymyxa 'HB 26-5' grew well on the media at pH 7.0 and the optimum growth temperature was $25^{\circ}C$. The pH of the media changed to weak acid(pH 6.1~6.5) at the beginning of incubation, but to weak alkali(pH 7.8~8.2) at 7days after incubation. The best carrier to enhance colonization of the bacteria were the mixture of rice bran and peat, or rice bran and kaoline, in those formulation the density of the bacteria was changed slightly, though the density was beginning to decrease 3 weeks after application at field. In view of the physical characteristics of the formulation for the density maintenance during storage such as the hardness and the size, the best one was the formulation consisted of sodium alginate 2%, kaolin 15% and rice bran 3%.