• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.182-188
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• 2017

In this work, a new type speaker which features various resonant frequencies is proposed utilizing a magneto-rheological (MR) fluid and its performance is evaluated in terms of the change of the field-dependent sound pressure level. In order to achieve this goal, a whole concept of the speaker system is firstly discussed and subsequently a controllable diaphragm is made using MR fluid whose rheological properties such as viscosity are controllable by the magnitude of magnetic field. Then, the proposed speaker system consisting of the inner structure and the squeeze mode type of MR diaphragm is established in an anechoic room The effectiveness of the proposed speaker system is experimentally evaluated at two different conditions; with and without the magnetic field. It is shown from experimental tests that the sound pressure level at different sound source can be controlled which is not able to achieve using one conventional speaker system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.456-461
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• 2017

In this study, the rheological properties of nitromethane gel propellants on nano/micron sized gelling agent are investigated. Silicon dioxide is used as the gellant with 5 wt%, 6.5 wt% and 8 wt% concentration, respectively, where the measurements are conducted under steady-state shear flow conditions using a rotational rheometer. The nitromethane/silicon dioxide gel showed non-Newtonian flow behavior for the entire experimental shear rate ranges. The gel fuels with nano-sized gellant had a slightly higher viscosity than the gel fuels with micron-sized one for low shear rate range. Additionally, it was found that Herschel-Bulkley model can hardly describe the rheological behavior of nitromethane gel propellant, but the NM model(by Teipel and Forter-Barth) is better suited to explain the rheological behavior of nitromethane gel propellant.

• Food Science and Preservation
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• v.30 no.3
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• pp.405-418
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• 2023

The aim of this research was to study the feasibility of the defatted wheat germ flour (DWGF) alone or in combination with xanthan gum (XG) as egg yolk substitutes in mayonnaise formulation. In this research, DWGF was used at different levels (0, 25, 75 and 100%) alone or in combination with the XG (0.2%) as egg substitutes. The effects of these substitutions on the stability, textural and rheological characteristics of mayonnaise were investigated. According to the results, DWGF can be used as an egg yolk substitute in mayonnaise. Combining DWGF and XG as egg yolk substitute, improved the stability, textural and rheological properties. Mayonnaise with 100% egg yolk replacement showed the hardest structure, while the lowest firmness value was obtained in the control containing 100% egg yolk. Also, the highest adhesiveness value occurred in the sample with 100% DWGF. The thixotropic behavior was observed for all investigated mayonnaise samples over the all ranges of the studied shear rate (0.05-450/sec). Furthermore, the highest content of consistency coefficient value was observed in the sample with 100% DWGF and 0.2% XG. Therefore, it can be concluded that low-cholesterol mayonnaise with proper stability, textural and rheological characteristics are achievable by applying of the desirable combination of DWGF and XG.

• Food Science and Biotechnology
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• v.17 no.1
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• pp.90-94
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• 2008

Dynamic rheological properties of honey samples with 3 different moisture contents (17.2, 19.0, and 21.0%) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer. The honey samples displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency ($\omega$). The magnitudes of G' and G" decreased with an increase in temperature and water content while a predominant increase of G' was noticed at $-15^{\circ}C$. The time-temperature superposition (TTS) principle was applied to bring G" values for honeys at various temperatures together into a master curve. The G" over the temperature range of -15 to $0^{\circ}C$ obeyed the Arrhenius relationship with a high determination coefficient ($R^2=0.98-0.99$). Activation energy value (Ea=112.4 kJ/mol) of honey with a moisture content of 17.2% was higher than those (Ea=98.8-101.1 kJ/mol) of other honey samples with higher moisture contents.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.41-46
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• 2009

The rheological properties of highly concentrated Ag nano sol depending on particle size were studied. The Ag nano sol was prepared by reducing the Ag ion in aqueous solution. The size of Ag nano particle was controlled by two steps of nucleation and growth, and the thickness of adsorption layer was varied by molecular weight of polyelectrolytes. The polyelectrolytes acted as not only ionic complex agent in ionic state and but also dispersant after formation of Ag nano sol. The effective volume was controlled by combination of varying the molecular weight of polyelectrolytes and the size Ag nano sol. The particle size and the viscosity of nano sol were characterized by particle size analyzer, HR-TEM and cone & plate viscometer. It was found that the 10 nm and 40 nm-sized Ag nano sols were prepared by controlling the nucleation and growth steps, respectively. Finally, we could prepare highly concentrated Ag nano sol over 50 wt%.

• Geotechnical Engineering
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• v.4 no.3
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• pp.53-62
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• 1988

When a ground soil is under the constant continuous stress less than the failure strength of that soil, its deformation, in some cases, will increase continuously as time goes on due to creep phenomena. Deformation of soil caused by creep behavior will appear in various types depending on the elastic, plastic, viscous properties of soil. Therefore in this study, visco-plastic characteristics of grouted soil was studied by analysing the result of uniaxial creep test on the grouted soil. As a result of this research, it was found that the rheological model of grouted soil can be decided as Vyalov model and the visco-plastic properties of grouted soil is influenced by the content of silicate in grout.

• Culinary science and hospitality research
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• v.12 no.2 s.29
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• pp.168-183
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• 2006

The purpose of this study was to investigate quality characteristics of roll bread with the addition of Chungkukjang powder(0, 5, 10, 15, 20%). The antioxidative activity of antioxidative substances produced from several bacterial strains isolated from fermented foods were tested by DPPH $(\alpha,\alpha’-diphenyl-\beta-picrylhydrazyl)$ free radical scavenging activity. The most optimal medium condition for the production of antioxidative substance from Bacillus sp. FF-7 was 2% galactose as carbon source and 1% tryptone as nitrogen source. In color values, with increasing Chungkukjang powder content, the "lightness" (p<0.05) decreased in the crumb bread, while the redness(p<0.05) and yellowness(p<0.05) increased. The volume and specific volume of roll bread with 5.0% Chungkukjang powder were the highest(p<0.05). In the rheology measurements for the roll bread, the hardness (p<0.05) decreased with the addition of 5.0% Chungkukjang powder, but then increased with further additions of Chungkukjang up to 10.0%. Highest sensory scores for color, flavor, taste(p<0.05), texture(p<0.05) and overall acceptance(p<0.05) were obtained from roll bread with 5.0% Chungkukjang powder and control. From the results of this study, it was assumed that the development of food products using Chungkukjang is prospective in response to health-oriented consumers.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.3-10
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• 2003

The formation of surface defects associated with Jotting in injection molding is related to the geometries of cavity and fate, operational conditions and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for the throe kinds of PCs which have different molecular weights and structures, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes those are tensile, flexural and impact test specimens with various gates and cavity thicknesses. Through this study we have observed that the jetting is related to the dic swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.114-117
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• 1986

The rheological properties of arrowroot starch suspension (2-6%) were investigated with a tube viscometer. The starch suspensions of less $t^1$, 4% showed a dilatant behavior with no yield stress at the temperature range of $30-65^{\circ}C$. However, the starch suspension of 6% concentration showed a pseudoplastic behavior at $65^{\circ}C$. The consistency index was exponentially increased with the increase of the starch concentration. The activation energy of flow of the starch suspensions was 0.370-0.399 kcal/mole at $30^{\circ}-60^{\circ}C$ and 28-60 kcal/mole at $65^{\circ}C$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.3
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• pp.115-120
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• 1989

Physicochemical changes were investigated during repeated freezing and thawing processes using fish meat paste of alaska pollack (Theragra chalcogramma). During repeated thawing process, the solubility of myofibrillar protein, $Ca^{++}-ATPase$ activity, water holding capacity (WHC), electrophoretic patterns and rheological properties were evaluated at various thawing temperatures. Solubility of myofibrillar protein and $Ca^{++}-ATPase$ activity were decreased with increasing thawing temperatures. Thawing temperatures and the frequency of freezing and thawing processes did not affect WHC significantly. Upon repeated freezing and thawing cycles, electrophoretic patterns showed that only the amount of myosin heavy chain was decreased, whereas the amount of actin remained constant. Young's modulus for viscoelasticity of fish meat pastes increased with increasing thawing temperatures and the value showed maximum at third cycle and decreased thereafter.