• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.752-757
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• 2011

This paper presents vibration characteristics of magnetorheological (MR) elastomer, whose elastic modulus are controllable by an applied magnetic field. By using this property, the material can be applied to vibration absorber, so that the stiffness of the absorber can be changed and actively controlled according to the magnetic flux density. However, the various performances of MR elastomer depends on different magnetically polarization direction and dimension during the manufacturing process. In this paper, in order to obtain the optimal characteristics of MR elastomer, MR elastomers with different types and dimensions are prepared for a series tests. Using this test setup, extent of natural frequency shifted against magnetic field at various excitation frequencies can be measured. Specimens prepared with 3 types which are exposed to magnetic field vertically, horizontally and unexposed during cure. Also, a set of design variables are considered to produce MR elastomers. Through the modal tests of mass structure with MR elastomer, the optimal design as well as the polarization direction of MR elastomer is obtained among the various dimensions and 3 directional types of MR elastomers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.147-152
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• 2006

This paper presents the dynamic characteristics of MR impact damper for vehicle collision system. Various types of mechanism have been proposed for reduce transmitted force to vehicle chassis and finally protect occupants from injury. In the case of frontal collision, the bumper make main role of isolation material for collision attenuation. In this study, proposed bumper system composed of MR impact damper and structures. The MR impact damper is to adopted MR fluid which has reversible properties with applied magnetic field. MR fluid operates under flow mode with Bingham flow and bellows is used for generation of fluid flow. Mathematical model of MR impact damper incorporated with MR fluid is established. Field dependent damping force is investigated with time and frequency domain. The MR impact damper is then incorporated with vehicle crash system. The governing equation of motion of vehicle model is formulated considering occupant model. Dynamic characteristics of vehicle collision system investigated with computer simulation.

• Macromolecular Research
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• v.10 no.4
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• pp.221-229
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• 2002

PET nanocomposites filled with fumed silicas were prepared via direct melt compounding method at various mixing conditions such as filler type and filler content. Some fumed silicas were pre-treated to improve the wettability and dispersibility, and principal characterizations were performed to investigate the effects of nano fumed silicas on polymer matrix. Hydrophobic fumed silica (M-FS), which has the similar contact angles of water with neat PET, acted as the best reinforcement for the thermal stability and mechanical properties of PET nanocomposite, and FE-SEM images also showed that M-FS was uniformly dispersed into matrix and had good wettability. But, some filler (O-FS) had low dispersibility and caused the deterioration of mechanical properties. Besides, the results of DSC revealed the nucleation effect of all fillers in polymer matrix, and PET nanocomposite filled with hydroptilic fumed silica (FS) showed markedly the characteristic dynamic rheological properties such as shear thinning behavior at very low frequencies and the decrease of viscosity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.275-278
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• 2007

In family mold, defects are frequently occurred by an excessive packing the smaller volume cavity during molding. Although runner size could be optimized by CAE analysis or experimental data, the filling imbalance is hardly avoided in the actual injection molding process by various means. Before this study, we developed a variable-runner system for balancing the cavity-filling for three resins (ABS, LDPE, and PA66) in the family-mold, and examined the effect of cross-sectional area reduction of a runner in the system. In this study, we examined the conditions of the pressure and temperature in the system with a CAE analysis. We also analyzed the influence of the rheological characteristic of resins to the balancing-capability of the system in order to help mold designers easily adopt the variable-runner system to their design.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.34-37
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• 2000

The effect of novel N-crotyl-N,N-dimethyl-4-methylanilinium hexafluroantimonate (CMH) curing agent on cure behavior and thermal properties of DGEBA epoxy cationic system was investigated. From DSC measurements of DGEBA/CMH system, it was shown that this system exhibits an excellent thermal latent characteristic in a given temperature and reveals complex cure behavior as indicated by multiple exotherms. The conversion and conversion rate of DGEBA/CMH system increased with increasing the concentration of initiator due to high activity of CMH. Viscoelastic properties during gel formation of DGEBA with CMH were investigated by rheological techniques under isothermal condition. The gel time obtained from the modulus crossover. point t(G')=G", was affected by high curing temperature and concentration of CMH, resulting in high degree of network formation in cationic polymerization. The thermal stabilities were discussed in terms of the activation energy for decomposition and thermal factors determined from TGA measurements.ents.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.7
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• pp.999-1004
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• 2010

This study was carried out to investigate the quality characteristics of ginseng Jung Kwa obtained by treatments with different sugars. Ginseng Jung Kwa was made with four different sugars (sucrose, glucose, honey and fructose). Chemical characteristic was measured by ginsenosides content and rheological characteristics were measured by rheometer and color meter. Total ginsenoside and Rf contents on Ginseng Jung Kwa by sucrose were highest at 10.0, and 7.82 mg/g, respectively. On ginseng Jung Kwa by fructose, total ginsenoside content was the lowest, and hardness and adhesiveness were the highest, and by honey, stiffness, cohesiveness, gumminess, chewiness, and springiness were the highest, and fracture force did not appear as a significant difference by treatment of different sugars. Coefficient of variance on ginseng Jung Kwa by honey was the highest. On ginseng Jung Kwa by sucrose, color (lightness, redness and yellowness) all were the highest. Browning on Jung Kwa by fructose was the greatest. Sensory evaluation preference analysis (color, taste, texture, flavor and overall acceptability) on ginseng Jung Kwa were determined by 50 panelists (30~50's age) using 5-point scale. On ginseng Jung Kwa by honey, texture and overall acceptability were the best. Ginseng Jung Kwa by fructose was very sticking and adhering, so preference by sensory evaluation was inferior to others.

• Food Science and Preservation
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• v.9 no.3
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• pp.309-314
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• 2002

Safflower Yangengs were prepared with composite dried powder of small red bean(Phaseolus radiatus L.) containing various ratios of safflower(Carthamus tinctorius L.) seed powder sifted through 20, 35, 45 and 60 mesh size and kinds of mixed water, their cooking characteristics were evaluated. Water content and water activity of cooked products were increased as the content and sieve mesh number of safflower seed powder increasing from 5%, 20 mesh to 20%, 60mesh, respectively. Color values of yangeng were increased in green tea extract mixed water. Rheological properties of yangengs were measured by compression test with texture analyzer, as results, hardness and fracturability increased that were shown in high content and high mesh number sifted safflower seed powder, but adhesiveness and springiness decreased, respectively. From the sensory evaluation test for yangeng, sensory scores were good scores in more mesh number sifted powder addition, especially overall acceptance, texture and fracturability. The 45mesh and 15% powder added yangeng was noted as having high sensory scores and preferable acceptability in sensory evaluation.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.95-107
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• 2004

In this paper, the rheological characteristics of slurry used fur slurry-shield tunnels were studied with emphasis on penetration characteristics. The slurry penetration was modeled by soil-filter clogging theory. The coefficient of particle deposition was suggested as an indicator of sin clogging during tunnel construction and calculated through model tests. The measured slurry weight, clogged in the base soil, was compared with the value obtained from clogging theory. Based on the testing results, a stability analysis of a tunnel face was performed to pinpoint the most influential factor affecting stability of slurry-shield tunnels. It was found that the stability of tunnel face is dependent on the ratio of infiltration velocity to the coefficient of particle deposition, and the penetration distance of slurry increases with the ratio of infiltration velocity to the coefficient of particle deposition. Since the stability of tunnel face decreases with the slurry penetration distance, it was necessary to add some additives in order to reduce the slurry penetration distance. It was found that the ground condition needs additives when the soil has the effective particle diameter$(D_{10})$ larger than 0.75mm. It was also found that the tunnel face stability due to slurry penetration is significantly affected by the tunnel advance rate.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.134-143
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• 1987

In order to observe the strawberry as the raw materials and to compare the color of strawberry's products, Hunter L,a,b tristimulate color values were measured physically by color difference meter. Food textural properties of strawberry were measured by Rheo textural meter for rheological properties of strawberry jam. According to results obtained, it showed that Hunter L,a,b tristimulus color values were affected by ripening time of strawberry and Hunter color values changed regularly on different pH. Deformation of red color pigment Hunter color values changed linearlly on different pH, therefore red color pigment of elderberry showed to be used as a food color agent. The first peak of strawberry in TPA curve was high as cherry, grape and pineapple Strawberry jam showed pseudoplastic characteristic and time dependence.

• Food Engineering Progress
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• v.21 no.2
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• pp.167-173
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• 2017

Purple-fleshed potato powder (PFPP) was investigated to determine optimal mixing ratio with milk powder and dextrin to produce a ready-to-eat mashed potato powder. The rheological characteristics, color, and anthocyanin contents were studied at a different concentration of ingredients. The power-law model was applied to explain the mechanical spectra of mashed potatoes which represented the change in structure induced by different mixing ratios. Mixture design was used to obtain the experimental points used to establish the empirical models to describe the effects of each ingredient on the characteristic of the mashed potato. The results of mechanical spectra showed that both storage and loss moduli (G' and G'') were significantly influenced by PFPP and milk powder concentration. The power law parameters n' and n'' showed higher values for the mashed potato with a lower concentration of PFPP and a higher concentration of milk powder, which showed that the gel networks involved in the mashed potato were weaker. The optimum mixing ratio with the highest redness and anthocyanin content, while maintaining the rheological properties similar to the commercial mashed potato, was determined as PFPP:milk powder:dextrin = 90.49:4.86:4.65 (w/w). The proportions of PFPP and milk powder in the formulation significantly changed the characteristics of mashed potato, whereas no significant effect of dextrin was observed in this formulation.