• Korea-Australia Rheology Journal
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• v.16 no.1
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• pp.47-54
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• 2004

Low Reynolds number, dilute, and surfactant-free bubble suspensions are prepared by mechanical mixing after introducing carbon dioxide bubbles into a Newtonian liquid, polyol. The apparent shear viscosity is measured with a wide-gap parallel plate rheometer by imposing a simple shear flow of capillary numbers(Ca) of the order of $10^{-2}$ ~ $10^{-1}$ and for various gas volume fractions ($\phi$). Effects of capillary numbers and gas volume fractions on the viscosity of polyol foam are investigated. At high capillary number, viscosity of the suspension increases as the gas volume fraction increases, while at low capillary number, the viscosity decreases as the gas volume fraction increases. An empirical constitutive equation that is similar to the Frankel and Acrivos equation is proposed by fitting experimental data. A numerical simulation for deformation of a single bubble suspended in a Newtonian fluid is conducted by using a newly developed two-dimensional numerical code using a finite volume method (FVM). Although the bubble is treated by a circular cylinder in the two dimensional analysis, numerical results are in good agreement with experimental results.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.59-67
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• 2012

In this paper, performances of solar hot water supply systems are parametrically analyzed with the variations of solar collector area, slope of collector and volume of storage. All simulations are conducted by using TRNSYS computer program. Average solar fractions, collector efficiencies and temperatures of storage are investigated monthly as well as annually. For system analysis, the maximum value of monthly average solar fractions has a limitation of 90 percent. As a result, the designed solar thermal system with $6m^2$ collector area, $50^{\circ}$ slope and $0.36m^2$ storage volume could provide almost an annual average solar fraction of 72 percent. By increasing the storage volume to $0.42m^2$, the annual solar fraction of system increases up to 73 percent.

• Steel and Composite Structures
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• v.12 no.2
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• pp.117-127
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• 2012

This paper deals with an experimental investigation to study the effect of fibre content on the stability of composite plates with various aspect ratios. Epoxy based glass fibre reinforced composite plates with aspect ratio varying from 0.4 to 1 and with volume fractions of 0.36, 0.4, 0.46, 0.49 and 0.55 are used for the investigation. From the study it is observed that for plate with aspect ratio of 0.5 and 0.4 there is no buckling and the plate got crushed at the middle. As the volume fraction increases the buckling load also increases to a limit and then began to reduce with further increase in fibre content. The optimum range of fibre content for maximum stability is found between 0.49 and 0.55. Polynomial expressions are developed for the study of buckling behaviour of composite plates with different volume fractions in terms of load and aspect ratio.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.821-826
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• 2008

This study evaluated spalling and internal temperature distribution after elevated temperatures test for high strength concrete ($f_{ck}=60\;MPa$) column member with various polypropylene fiber volume fractions. The ISO-834 time-temperature curve was used for measurement of fire resistance properties. As the result of test, average internal temperature results indicated to low temperature in increased polypropylene fiber volume fraction. But, the highest internal temperature results show that does not difference in proportion of polypropylene fiber volume fractions.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.3
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• pp.198-207
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• 1998

To determine the effect of temperature and microstructure on the fatigue crack propagation behavior in Ti-3Al-2.5V alloy, experimental investigations have been carried out with the specimens of different temperatures and different volume fractions of prime $\alpha$-phase. The temperatures employed were room temperature, 20$0^{\circ}C$, 30$0^{\circ}C$ and 40$0^{\circ}C$ under the same frequency of 20Hz. To obtain the different volume fractions of the primary $\alpha$-phase, specimens were solution-treated at $\alpha$+$\beta$ and above the $\beta$ region. From the experimental results, following conclusions were obtained. (1) ΔKth was observed to increase with the less volume fraction of the primary $\alpha$-phase. (2) As the temperature increased. (3) Microstructures having more primary $\alpha$-phase showed higher strength at the high temperatures.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.46-50
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• 2008

Super duplex stainless steel has along life in severe environments because of its strength and corrosion resistance. If 0.2$\sim$0.3% Nitrogen in aninterstitial solid solution is added, the austenite structure is reinforced. This improves the solid solution hardening and the anticorrosionability. In this study, the mechanical properties and structures of the super duplex stainless steel with the 0.2% N additive were investigated to determine the effect of various volume fractions on the austenite phase. The various volume fractions and distributions of the austenite structure in the applied test specimens were obtained by changing the heat treatment temperature and cycle. The characteristics by amounts of the $\sigma$ phase obtained from the precipitation heat treatment were alsoinvestigated. From the results, when the austenite volume fraction increases, the tensile strength decreases and elongation increases. And the $\sigma$ phase was rapidly increased by increasing the heat treatment time. When the volume fraction of the $\sigma$ phase increased, tensile strength increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.6
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• pp.38-47
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• 1989

The Finite Element Method has been employed to calculate the effect of particle size, matrix, and volume fractions on the stress-strain relations of .alpha.-.betha. titanium alloys. It was found that for a given volume fraction, the calculated stress-strain curve was higher for a finer particle size than for a coarse particle size within the range of the strains considered, and this behavior was seen for all the different volume fraction alloys considered. The calculated stress-strain curves for three vol. pct .alpha. alloys were compared with their corresponding experimental curve, and in general, good agreement was found.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.65-69
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• 2000

This study is to investigate the characteristics of fatigue crack propagation in rolled super duplex stainless steel that was changed austenite-ferrite volume fraction by heat treatment. It was used two kinds of specimen the rolling and the transverse directions δ-phase fraction affected sound velocity hardness and Young's modulus. Characteristics of fatigue crack propagation was affected by anisotropy and (δ+γ) phase volume fractions.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.1
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• pp.100-107
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• 1998

Polyester filaments were dyed with disperse dye in dyebath containing water and water miscible organic solvents . acetone, 1,4-dioxane, DMF. In case of Acetone and 1,4-dioxane, the equilibrium dyeuptake was maximun at the volume fraction 0.05. The equilibrium dye uptakes were decreased as volun~e fraction of organic solvents were increased. When the volume fractions of water miscible organic solvents were varied, dye uptake was increased constantly with dyeing time. In dyebath containing water and water miscible organicsolvent, the dyeuptake was increased quickly during initial 40∼ 60 min. and slowly increased there after. The slope of Ct/Coo to t was greater in dyebath containing water and water miscible organic solvents than dyebath containing water. The differences of the slope with volulne fractions of water miscible organic solvent were not shown big.