• Elastomers and Composites
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• v.15 no.3
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• pp.147-154
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• 1980

The cellular rubber products for industrial purpose have been applied in many fields such as auto-motive parts, ship-building, machinery, sports goods, diving suit or interior housings etc. The purpose of this dissertation is to study the physical properties of celluar rubber products particulary for those elastomers such as EPDM, CR and NBR with heat resistance property, weather proofness, and oil resistance characteristics respectively, aiming at improving their quality, and renovating the manufacturing know-how which is beyond our technical power at the present time in Korea. In order to meet this requirement an ideal recipe is being shown for the three elastomers, and also a practical recipe which is easily available in terms of compounding ingredients in domestic market has set up as shown in Table 1. for the investigation of vulcanization characteristics by means of Rheometer. The optimum Mooney viscosity of compounded rubber was found to be approximately $ML_{1+4}(100^{\circ}C)$ $30\sim45$. Excess mustication makes a dispersion of ingredients worse, consequently it causes deformation of shapes and heterogenous cell distribution. In other words the articles are rejected because of its insufficient workmanship. The results of physical properties of the products are indicated in Table 3. It has shown that the quality meet requirement when tested in accordance with ASTM D572, 573 and D 395. The test results o CR/IR blends in terms of hardness, volume change by blowing, tensile strength and elongation have been shown.

• Korean Journal of Materials Research
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• v.29 no.4
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• pp.221-227
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• 2019

This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated $ZrO_2$ ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated $ZrO_2$ particles are observed by FE-TEM and FT-IR. The rheological properties of VTES-coated $ZrO_2/High-temp$ composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3D-printed objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated $ZrO_2$ ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.73-82
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• 2009

Injectable calcium phosphate cement (CPC) has been used as bone substitute successfully due to good biocompatibility and osteoconductivity. One of the important mechanical characteristics of CPC is flowablility, which can be evaluated by measuring rheological parameters. However, there have been few studies that measured rheological properties of CPC. The purpose of this study was to evaluate the effects of temperature and concentrations of 2 kinds of setting solutions, hydroxyprophyl methylcellulose (HPMC) and polyacrylic acid (PAA), on rheological properties of CPC. The CPC used was dicalcium phosphate dihydrate (DCPD). Rheological properties of CPC paste were measured using rheometer. The effect of concentrations of each solution (2% and 1% HPMC and 35% and 17.5% PAA) was evaluated. The effect of temperature ($25^{\circ}C$ and $37^{\circ}C$) on the rheological properties of CPC was also investigated. The statistical analysis was carried out with Mann-whitney test with Bonferronis collection. CPC with both setting solutions showed shear thinning behavior. Higher concentrations of setting solution (2% HPMC and 35% PAA) produced significantly higher viscosity than lower concentrations of setting solution (1% HPMC and 17.5% PAA). CPC with HPMC showed significantly higher viscosity at $37^{\circ}C$ that at $25^{\circ}C$. CPC with PAA showed lower viscosity at $37^{\circ}C$ than at $25^{\circ}C$, although the difference was not statistically significant. The results showed that CPC with HPMC or PAA solutions are pseudoplastic and the concentrations of setting solutions and temperature may have an effect on the rheological properties of CPC paste. These results showed that the flowability of injectable CPC could be improved by use of increasing frequency of oscillation. In clinical practice, the use of ultrasonic vibration would be helpful in application of injectable CPC. CPC with HPMC could be more easily applicated at $25^{\circ}C$ than $37^{\circ}C$. The use of lower concentrations of HPMC and PAA solution would be beneficial in terms of flowability.

• Food Science of Animal Resources
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• v.32 no.6
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• pp.803-809
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• 2012

This study was carried out to evaluate the effects of whey ferment containing L. acidophilus KCCM 32820 and P. freudenreichii KCCM 31227 on the quality characteristics of white pan bread. Instrumental analysis such as alveograph, gelatinization temperature, texture analysis, retrogradation rate was determined. In an alveograph test, $P_{max}$ value in the treatment was higher than that in the control, but extensibility of dough in the control showed to be higher than in the treatment, so test dough showed more strength than the control. In terms of DSC analysis for gelatinization, temperature there were no significant differences of $T_p$ and ${\Delta}H$ between the control and the treatment. In hardness analysis by rheometer, dough containing whey ferment revealed lower values than the control. From the analysis of the organic acid contents, propionic acid was not detected in the control, however 1.13 mg/g of propionic acid was detected in the treatment. In the retrogradation analysis by DSC, the test delayed slightly compared to the control.

• Restorative Dentistry and Endodontics
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• v.29 no.6
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• pp.520-531
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• 2004

The aim of this study was to investigate the effect of monomer and filler compositions on the rheological properties related to the handling characteristics of resin composites. Methods. Resin matrices that Bis-GMA as base monomer was blended with TEGDMA as diluent at various ratio were mixed with the Barium glass (0.7 um and 1.0 um), 0.04 um fumed silica and 0.5 um round silica. All used fillers were silane treated. In order to vary the viscosity of experimental composites, the type and content of incorporated fillers were changed, Using a rheometer, a steady shear test and a dynamic oscillatory shear test were used to evaluate the viscosity ($\eta$) of resin matrix, and the storage shear modulus (G'), the loss shear modulus (G"), the loss tangent ($tan{\delta}$) and the complex viscosity (${\eta}^*$) ofthe composites as a function of frequency ${\omega}{\;}={\;}0.1-100{\;}rad/s$. To investigate the effect of temperature on the viscosity of composites, a temperature sweep test was also undertaken. Results. Resin matrices were Newtonian fluid regardless of diluent concentration and all experimental composites exhibited pseudoplastic behavior with increasing shear rate. The viscosity of composites was exponentially increased with increasing filler volume%. In the same filler volume, the smaller the fillers were used, the higher the viscosities were. The effect of filler size on the viscosity was increased with increasing filler content. Increasing filler content reduced $tan{\delta}$ by increasing the G' further than the G". The viscosity of composites was decreased exponentially with increasing temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.3
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• pp.442-448
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• 2015

The aim of this study was to investigate the effects of guar gum on the rheological behaviors, sensory attributes, and consumer acceptability of soft tofu stew sauce. Five different soft tofu stew sauces were commercially manufactured with various levels of guar gum (0.0, 0.1, 0.2, 0.4, and 0.5%). Twelve sensory attributes of the stew sauces were identified by nine trained descriptive panelists, whereas hedonic levels of the stew sauces were assessed by a group of 51 consumers. Steady flow of the stew sauces were measured by a rheometer. Significant differences were observed in terms of sensory saltiness and viscosity among the products. For the consumer test, 0.1% guar gum-added product was most liked by consumers. Partial least square regression showed sensory shellfish, green onion, and shrimp flavors to be key factors affecting overall acceptability for the stew sauces. For rheological behaviors, 0.0, 0.1, and 0.2% guar gum-added products showed newtonian behaviors ($R^2$=0.99 by power law model), whereas 0.4 and 0.5% products followed pseudoplastic behaviors ($R^2$=0.99 by power law model). Based on the established equivalence table using rheological and consumer data, smaller than 0.0114 ($Pa{\cdot}s$) of the apparent viscosity should be necessary to guarantee 'slightly like' category in a consumer hedonic test. It seems that addition of guar gum not only influenced rheological properties but overall acceptability for the stew sauces.

• Applied Microscopy
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• v.38 no.4
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• pp.339-345
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• 2008

In this study, we compared the stress and tensile strength of the hair treated with oxidative permanent dye with those of virgin hair. We investigated the fine structure of the hair section after the tensile test using scanning electron microscopy. The tensile strength of the virgin hair was measured as $14.66\;g/cm^2$, tensile energy was $108\;erg/cm^2$, and the maximum stress was 146.64g. Those of the dyed hair were $13.69\;g/cm^2$, $89.62\;erg/cm^2$ and 136.90 g, respectively. The differences in the tensile strength, the tensile energy and the maximum stress were $-0.97\;g/cm^2$, $-18.38\;erg/cm^2$, -9.74 g, respectively, which showed that the dyed hair had less elasticity and strength than the virgin hair. In the scanning electron microscopy investigation of the damaged hair after the tensile test, lift-off of the cuticle outer layer were shown in both virgin hair and dyed hair, which was more severe in the dyed hair than the virgin hair. Adjacent cuticular cells of the cuticle layer were separated by the destruction of intercellular membrane complex. The macrofibrils were exposed and separated from the cortex torn by tensile strength.

• Journal of the Korean Society of Food Culture
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• v.7 no.3
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• pp.213-222
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• 1992

This investigation was undertaken for the purpose of studying the quality and acceptability during storage at room or refrigerator temperature of Yackwa containing waxy rice flour substituted for 0,10,30,50,70% of the wheat flour. The storage periods were 0,15,30 and 45 days. Chemical composition, composition of fatty acids, and value, and peroxide values of Yackwa were measured. Sensory evaluation was done by a panel of 5 judges majoring in food and nutrition. The evaluation was repeated 4 times. Objective evaluation was done by rheometer and color difference meter. Chemical composition of Yackwa were $5.9{\sim}6.8%$ for moisture, $3.43{\sim}4.09%$ for crude protein, $22.35{\sim}27.65%$ for crude fat, $0.27{\sim}0.31%$ for ash, $15.6{\sim}18.4%$ for fructose, $10.6{\sim}13.7%$ for glucose, $0.34{\sim}1.0%$ for sucrose, and $0.79{\sim}2.37%$ for maltose, respectively. Fatty acid contents of Yackwa were $10.54{\sim}10.73%$ for palmitic acid, $4.12{\sim}4.18%$ for stearic acid, $25.8{\sim}26.9%$ for oleic acid, $51.6{\sim}52.1%$ for linoleic acid, and $0.27{\sim}0.34%$ for linolenic acid, respectively. Acid value and peroxide value of Yackwa during storage showed little change. As a result of sensory evaluation for Yackwa made various levels of waxy rice flour, there were no significant differences in most of characteristics between the samples supplemented with waxy rice flour to 30% of wheat flour at 0.01% level. By the color difference meter, the value of L (lightness) and b (yellowness) were increased by increasing the amounts of waxy rice flour, however, there were no significant differences at 0.1% level between the samples supplemented with waxy rice flour to 30% of wheat flour, on the other hand, the value of a (redness) was decreased by increasing the amount of waxy rice flour. In the textural characteristics, brittleness, and chewiness were increased by increasing the amounts of waxy rice flour, and by lengthening the storage period, on the other hand, resilience and cohesiveness showed vice versa. In the correlation coefficient between sensory characteristics and mechanical characteristics, overall acceptability in sensory evaluation correlated significantly with cohesiveness, chewiness, and the values of L, a, and b in mechanical test in most of samples(p<0.001).

• Journal of Pharmaceutical Investigation
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• v.39 no.3
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• pp.185-199
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• 2009

Using a strain-controlled rheometer [Advanced Rheometric Expansion System (ARES)], the steady shear flow properties and the dynamic viscoelastic properties of $Antiphlamine-S^{(R)}$ lotion have been measured at $20^{\circ}C$ (storage temperature) and $37^{\circ}C$ (body temperature). In this article, the temperature dependence of the linear viscoelastic behavior was firstly reported from the experimental data obtained from a temperature-sweep test. The steady shear flow behavior was secondly reported and then the effect of shear rate on this behavior was discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters. The angular frequency dependence of the linear viscoelastic behavior was nextly explained and quantitatively predicted using a fractional derivative model. Finally, the strain amplitude dependence of the dynamic viscoelastic behavior was discussed in full to elucidate a nonlinear rheological behavior in large amplitude oscillatory shear flow fields. Main findings obtained from this study can be summarized as follows : (1) The linear viscoelastic behavior is almostly independent of temperature over a temperature range of $15{\sim}40^{circ}C$. (2) The steady shear viscosity is sharply decreased as an increase in shear rate, demonstrating a pronounced Non-Newtonian shear-thinning flow behavior. (3) The shear stress tends to approach a limiting constant value as a decrease in shear rate, exhibiting an existence of a yield stress. (4) The Herschel-Bulkley, Mizrahi-Berk and Heinz-Casson models are all applicable and have an equivalent validity to quantitatively describe the steady shear flow behavior of $Antiphlamine-S^{(R)}$ lotion whereas both the Bingham and Casson models do not give a good applicability. (5) In small amplitude oscillatory shear flow fields, the storage modulus is always greater than the loss modulus over an entire range of angular frequencies tested and both moduli show a slight dependence on angular frequency. This means that the linear viscoelastic behavior of $Antiphlamine-S^{(R)}$ lotion is dominated by an elastic nature rather than a viscous feature and that a gel-like structure is present in this system. (6) In large amplitude oscillatory shear flow fields, the storage modulus shows a nonlinear strain-thinning behavior at strain amplitude range larger than 10 % while the loss modulus exhibits a weak strain-overshoot behavior up to a strain amplitude of 50 % beyond which followed by a decrease in loss modulus with an increase in strain amplitude. (7) At sufficiently large strain amplitude range (${\gamma}_0$>100 %), the loss modulus is found to be greater than the storage modulus, indicating that a viscous property becomes superior to an elastic character in large shear deformations.

• Korean journal of food and cookery science
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• v.7 no.4
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• pp.63-69
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• 1991

This study was undertaken for the purpose of studying the physicochemical propery of mungbean and texture of mungbean starch gels. Mungbean starch gel made with different levels of oil were tested to investigate the textural characteristics by mechanical test. The results are summerized as fallows: The content of moisture fat, protein, and ash in Seonwha mungbean were shown to be about 13.19%, 1.02%, 23.57% 3.13% respectively. Those of Seonwha mungbean crude starch were 12.48%, 0.63%, 0.94%, 0.13% respectively. The gain of dry crude starch from peeled mungbean was 22.48%. Water binding capacity of Seonwha mungbean crude starch was 183.1%. The pattern of change in swelling power of Seonwha mungbean crude starch for increasing temperature increased slowly to $70^{\circ}C$, and then increased rapidly. The pattern of change in solubility was similar to that of swelling power. The amylose and amylopectin content were 22.5%, 77.5%. Brabender hot-paste viscosities of mungbean crude starch at 8% and 10% showed the similar amylogram patterns with peak vicosity. By the Rheometer measurement result of 8% 10% mungbean starch gel, Hardness and Fractuability tended to be decreased as the addition level of oil increased. Elasticity, Adhesiveness, Chewiness, L, a, and b value tended to be increased as the addition level of oil increased.