• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.124-134
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• 2013

This study investigated the effect of surface water on concrete substrate on adhesive strength in tension of very high flowable SBR-modified cement mortar. The specimens were prepared with proportionally mixing SBR latex, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Polymer cement ratio (P/C) were 10, 20, 30, 50 and 75% and the weight ratio of fine aggregate to cement were 1:1 and 1:3. The specimens obtained with different P/C and C:F were characterized by unit weight, flow test, crack resistance and adhesion test. After basic tests, two mixtures of P/C=20% and 30% in case of C:F=1:1, and one mixture of P/C=50% in case of C:F=1:3 were selected, respectively. These three selected specimens were studied about the effect of surface water evenly sprayed on concrete substrate by a amount of 0, 0.006, 0.012, 0.017, 0.024g per unit area ($cm^2$) of concrete substrate surface The results show that surface water on concrete substrate increases the adhesive strength in tension of high flowable SBR-modified cement mortar and improve the flowability compared to the non-sprayed case.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.22-35
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• 1993

The transport phenomena of the free amino acids through poly(hydroxyethyl methacrylate)[P(HEMA)] have been investigated with and without various kinds of surfactants solution and in the mixed surfactants solution. Glutamine has the highest diffusivity among 4 amino acids at 1CMC of cetyldimethylethylammonium bromide(CTABr) surfactant. Glutamic acid is not affected by the concentration of CTABr. Methionine and Lysine shows slight decreased diffusivity at 0.5 CMC, but increase its diffusivity at 1CMC and 2CMC due to the structure change of membrane and the viscosity change of surfactant solution. Glutamic acid has the highest diffusivity among four amino acids at sodium dodecyl sulfate(SDS) and Triton X-100 surfactant. In mixed surfactant solution, each amino acids shows high diffusivity through 45% water content membrane at the 0.5 mole fraction of SDS in the SDS/TX-100 surfactant mixtures. It has been found that not only the property of membrane but also the effects of solute-solvent interactions and solvent effect are very important as the permeation of amino acids occurs through P(HEMA) membrane. The diffusivities of free amino acids through membrane depend upon their molecular shape, size and charge.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.455-463
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• 2012

In this study, the measurement of physical properties of ethylene oxide-propylene oxide adducted zwitterionic surfactants were measured such as critical micelle concentration, surface tension, interfacial tension, contact angle, viscosity and foam stability. Also, the dual function characteristics of a zwitterionic surfactant were investigated by determining an isoelectric point, which were obtained using zeta potential measurement and QCM (quartz crystal microbalance) experiments. The isoelectric point of DEP-OSA82-AO zwitterionic surfactant determined by zeta potential measurement was close to that obtained by QCM experiment and both results have shown almost the same trend as that determined by the frictional property measured using an automated mildness tester. In particular, it has been observed that DEP32-OSA82-AO and DEP34-OSA82-AO surfactants provide better softening effect at a pH of acidic or neutral condition than at an alkaline condition. This result indicates that both surfactants act as a cationic surfactant at a pH of acidic or neutral condition and thus provide good softening effect during a rinsing cycle in the detergency process.

• Korean Journal of Food Science and Technology
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• v.36 no.2
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• pp.246-254
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• 2004

Physicochemical properties of bread dough added with silkpeptide were investigated. Protein content of silkpeptide was 90.83%. In amino acid analysis, glycine content was highest at 18,760.04 mg%. Alanine, serine, and tyrosine contents were much higher in silkpeptide flour than wheat flour. Mixed silkpeptide showed low lightness and redness values and high yellowness. Farinograph water absorption decreased as silkpeptide content increased. Both arrival and development times of silkpeptide-added dough were longer than those of wheat flour, As silkpeptide content increased, degree of weakness increased, Maximum viscosity of amylograph decreased gradually with addition of silkpeptide, while gelatinization temperature was not affected. Extensograph showed extensibility and resistance to extension of dough increased, while ratio of resistence to extensibility highly increased with increasing amount of silkpeptide. Silkpeptide added to bread dough showed oxidation effect, indication that it could be used as natural additive for improving bread dough quality.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.152-158
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• 2015

In order to investigate the feasibility of stone dust sludge as fine aggregate, an experimental study was performed on cement mortar with stone dust sludge. fresh mortar properties and strength with various stone dust sludge replacement ratios were estimated. the replacement ratio adopted in this study was 0, 10, 20, 30%. Flow, air content, and rheological properties were considered as properties of fresh mortar. Compressive strength and flexural tensile strength were measured for strength. The results are as follows. Higher amount of stone dust sludge caused reduction in slump and air content. In the rheological properties, both yield stress and plastic viscosity increased as stone dust sludge content increased up to 20% replacement ratio, but there were no remarkable difference between 20 and 30%. Yield stress increased drastically between 10 and 20%. Compressive and flexural tensile strength results indicated that the strength variation was not significant according to stone dust sludge content, but the strength gain in the early age by adding stone dust sludge was evident. the strength at the age of 28 days however did not show noticeable effect of adding stone dust sludge.

• Korean Journal of Microbiology
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• v.53 no.2
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• pp.103-117
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• 2017

The aim of this study was to evaluate the effect of green tea extract on probiotic potential, physico-chemical and functional properties of yogurt fermented with Lactobacillus acidophilus D11 or Lactobacillus fermentum D37 strains isolated from Doenjang. Probiotic activities such as the resistance to artificial digestive juices and the ability to adhere to epithelial cells were slightly higher in yogurt supplemented with green tea extract than in plain yogurt, which may be attributed to the increase in the number of lactic acid bacteria (LAB) by green tea extract supplementation. Furthermore, the microbiological and physico-chemical properties such as the number of LAB, organic acid production and viscosity were significantly (P<0.05) increased in yogurt added green tea extract compared to plain yogurt fermented with L. acidophilus D11. However, the green tea extract did not significantly (P>0.05) affect these properties of yogurt fermented with L. fermentum D37 strain. Meanwhile, the antibacterial activities against Escherichia coli O157 ATCC 43889, Salmonella enteritidis ATCC 13076, and Salmonella typhimurium KCTC 2514 and antioxidant activities including total phenol content, radical scavenging ability, and ferric-reducing antioxidant power were significantly higher in plain yogurt fermented with L. fermentum D37 than with L. acidophilus D11. The antibacterial and antioxidant activities of the yogurt were significantly (P<0.05) increased in proportion to the concentration of green tea extract added to plain yogurt. Consequently, green tea yogurt fermented with L. acidophilus D11 or L. fermentum D37 was considered to be a useful functional food that can inhibit the growth of pathogenic bacteria and scavenge the free radicals from the body cells.

• Korean Journal of Food Science and Technology
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• v.30 no.4
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• pp.832-841
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• 1998

In order to economically utilize flour brew with Bifidobacterium bifidum as a bread improver, the effect of flour brew on the rheological properties of dough, growth curve and acid production, and symbiosis with yeast were investigated. Growth of bifidobacteria was not increased more than initial seed volume but was consistent during 24 hours of incubation. pH was decreased and T.T.A was increased up to 12 hours of incubation. Symbiosis between bifidobacteria and yeast was little. Bifidobacteria produced more lactic acid than acetic acid in flour brew and the opposite in skim milk broth. This result was inferred from Lactobacillus sp. inherent in flour. On rheological properties of dough, farinograms of flour showed progressively decreasing baking absorption, mixing time and stability as the amount of flour brew increased. The validation of extensograms showed that R/E ratio linearly increased with increment of flour brew, and nearly doubled in all treatments comparing to that of control, which suggest the reduction of actual fermentation time. On visco/amylograms, malt index increased with addition of flour brew, accordingly showing the decrease in viscosity. Break down and set back value decreased with increment of flour brew, suggesting that staling rate of bread can be delayed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.1
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• pp.118-127
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• 2015

In this study, chiffon cakes were prepared with wild grape powder. Different amounts of the wild grape powder were tested (3%, 6%, 9%, and 12%) to determine the optimal amount. Rice chiffon cake was evaluated for quality characteristics, antioxidant properties, and sensory evaluation. The specific gravity of control batter was 0.48 g/mL, and it decreased with increasing amounts of wild grape powder, whereas viscosity showed the reverse effect. The pH of batter and cake decreased with increasing amounts of wild grape powder. The moisture content significantly increased with increasing amounts of wild grape powder, and the water activity of cakes was not significantly different between samples from 0.905~0.908. For color, lightness and yellowness deceased with increasing amounts of wild grape powder, whereas redness showed the reverse effect. For texture, hardness, fracturability, gumminess, and chewiness significantly increased with increasing amounts of wild grape powder. Total polyphenol content, DPPH radical scavenging activity, and ABTS radical scavenging activity significantly increased with increasing amounts of wild grape powder. In the sensory evaluation, the control sample showed the highest scores for color, flavor, softness, and overall acceptability. Based on these results, wild grape powder could be considered as a functional material, and 6% wild grape powder is the optimum level for manufacture of rice chiffon cake.

• Elastomers and Composites
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• v.38 no.1
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• pp.57-64
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• 2003

Metal oxide(MgO) was added to FKM rubber in order to develop automotive fuel hose which ran show elastic characteristics under extreme condition. Cure characteristics, physical properties, thermal resistance and fuel resistance of FKM compounded rubber with MgO were investigated. MgO was mixed to FKM rubber materials within the range of $0{\sim}20phr$. From the test results of rheological properties and Mooney viscosity, the $t_{s2}$, $T_{c90}$ values increased as the MgO contents increased in FKM rubber compounding. Hardness and 100% modulus of FKM compounded rubber slightly increased, but tensile strength and elongations at break slightly decreased. From the test results of thermal resistance of rubber specimens at 130, 150, and $170^{\circ}C$ for 70 hrs, the changing rate of physical properties was found to be relatively small. Fuel resistance tests were carried out for fuel A, B, C and D at $40^{\circ}C$ for 70hrs, and the results showed that the changing rate in physical properties was found to increase from Fuel A to D, Furthermore thermal properties of FKM compounded rubber containing MgO were also investigated by using TGA/DSC. The optimum mixing ratio of additive to FKM rubber to get the maximum effect on thermal resistance and fuel resistance, within the range of desirable specification for rubber material, was determined to be 6 phr for MgO.

• Elastomers and Composites
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• v.38 no.1
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• pp.81-87
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• 2003

In this work, $Fe_3O_4$ (magnetite), conductive filler was prepared from $FeCl_2{\cdot}4H_2O,\;(CH_2)_6N_4$ (hexamethylene tetramine), and $NaNO_2$, followed by mixing with crystallizable chloroprene rubber(CR). The influence of conductive filler content on the properties of the conductive composite was studied and temperature dependence of the electrical conductivity (${\sigma}$) was also investigated. It is found that the percolation threshold concept holds true for the conductive particle-filled composite where ${\sigma}$ indicates a nearly sharp increase when the fraction of magnetite in the mixture exceeds 27%. The temperature dependence of ${\sigma}$ is thermally activated blelow or at the $P_c$. Magnetite acts as reinforcement and conductive filler for CR rubber. Moreover, it is shown that the composite with magnetite of 50 phr gives the most significant mechanical properties for tensile strength and elongation at break, which is due to the formation of optimum physical interlock and crosslinking. The results of 100%, 200%, and 300% moduli suggest that the moduli are related with reinforcement effect of magnetite and viscosity of the blend.