• Korea-Australia Rheology Journal
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• 제12권3_4호
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• pp.151-155
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• 2000

A semiconducting poly(naphthalene quinone) radical (PNQR) was synthesized from Friedel-Craft acylation between naphthalene and phthalic anhydride and used as dispersing particles of a dry-base electrorheological (ER) material in silicone oil. Under an applied electric field (E), the dynamic yield stress (${\tau}_{dyn}$) of this ER fluid, obtained from a steady shear experiment with a controlled shear rate mode, was observed to increase with $E^{1.45}$ Based on this relationship, we propose a universal correlation curve for shear viscosity, which is independent of E using a scaling analysis.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.463-466
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• 2005

The microstructure and mechanical properties of rheocast A356 aluminum alloy by electromagnetic stirring are studied. In the electromagnetic stirring, main parameters are stirring current and stirring time. Stirring current is ranged from 0 A to 60 A, and stirring time is 20, 40, and 60 sec. In the rheocasting, injection velocity and applied pressure are changed. In this paper, the effect of stirring current and stirring time on the morphology and mechanical properties are investigated and analyzed.

• 한국안전학회지
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• 제28권6호
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• pp.17-22
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• 2013

The production of flame-retardant polypropylene powder coating with the addition of flame retardant (PP) controlled rheology (CR) and polypropylene, were discussed comparing the mechanical properties, such as safety and topical coating properties. Mechanical properties measurements showed almost the same as AA-1 where the flame retardant is not added. These results appear to, and because it is excellent in compatibility with polypropylene and flame retardant. Physical properties of the coating film, a test piece flame retardant organic is added, although it shows the physical properties of the coating film was stable, did not show the physical properties satisfactory is the test piece flame retardant of weapons has been added. In the safety of the topic, AA-4, AA-5 the results of thermal analysis but it is excellent, the LOI is excellent in 27.8 vol% 27.0 vol% in AA-4 and AA-2, AA-3, and 27.4 vol%, did not show many obstacles flame AA-5 result UL94.

• 소성∙가공
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• 제14권4호
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• pp.351-359
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• 2005

The semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Also, the rheo-casting has been substituted for thixo-casting, because the rheo-casting can control the solid particles to globular and non-dendritic solid phase. In the rheo-casting process, the important thing is to control the solid particles behavior in semi-solid materials. So in this paper, to control solid particles behavior in semi-solid materials, we experimented about the die filling tests during the semi-solid die casting in 0.3, 0.4, 0.5 and 0, 6 solid fraction. The die filling in semi-solid die casting were simulated by MAGMA soft/thixo module. By the die filling tests and computer simulation, the effect of solid particles behavior in rheology flow had been investigated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.358-361
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• 2005

The rotational barrel type equipment has been designed for the new rheology fabrication process. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed and rotation time of barrel. The barrel surface can be controlled the temperature by the induction heating and cooling system. Many experiments were widely examined by using this system with controlling the rotation speed and the rotation time. The possibility for the rheoforming process was investigated with microstructural characteristics.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.645-648
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• 2005

The rotational barrel type equipment has been designed for the new rheology fabrication process. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed and rotation time of barrel. The barrel surface can be controlled the temperature by the induction heating and cooling system. Many experiments were widely examined by using this system with controlling the rotation speed and the rotation time. The possibility for the rheoforming process was investigated with microstructural characteristics.

• Journal of Microbiology and Biotechnology
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• 제20권4호
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• pp.844-851
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• 2010

Controlling the dissolved oxygen (DO) in the fed-batch culture of the medicinal mushroom Ganoderma lucidum led to a 2-fold increase of the maximum biomass productivity compared with uncontrolled DO conditions. By contrast, extracellular polysaccharide (EPS) production was two times higher under oxygen limitation (uncontrolled DO) than under increased oxygen availability (controlled DO). Morphologically, dispersed mycelium was predominant under controlled DO conditions, with highly branched hyphae, consistent with the enhanced culture growth noted under these conditions, whereas in the uncontrolled DO process mycelial clumps were the most common morphology throughout the culture. However, in both cultures, clamp connections were found. This is an exciting new finding, which widens the applicability of this basidiomycete in submerged fermentation. In rheological terms, broths demonstrated shear-thinning behavior with a yield stress under both DO conditions. The flow curves were best described by the Herschel-Bulkley model: flow index down to 0.6 and consistency coefficient up to 0.2 and 0.6 Pa $s^n$ in uncontrolled and controlled cultures DO, respectively. The pseudoplastic behavior was entirely due to the fungal biomass, and not to the presence of EPS (rheological analysis of the filtered broth showed Newtonian behavior). It is clear from this study that dissolved oxygen tension is a critical process parameter that distinctly influences G. lucidum morphology and rheology, affecting the overall performance of the process. This study contributes to an improved understanding of the process physiology of submerged fermentation of G. lucidum.

• Korea-Australia Rheology Journal
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• 제11권3호
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• pp.169-195
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• 1999

An electrorheological fluid (ERF) is typically a suspension of semi-conducting solid particles dispersed in an insulating carrier fluid, and shows a dramatic change in rheological properties when an external electric field is applied. This rapid and reversible change in flow properties has potential application in many electronically controlled mechanical devices, but the development of efficient devices and optimal materials for ERF is still hindered by incomplete understanding of the fundamental physical mechanisms involved. In recent years there have been considerable advances In relating microstructural models to the rheological behaviour, and these will form the basis of this review. Results of the theoretical calculations and simulations will be compared to the key experimental evidence available. An overview of the fundamental physical concepts behind electrorheological fluid behaviour will also be presented.

• Korea-Australia Rheology Journal
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• 제15권1호
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• pp.9-17
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• 2003

The rheological behaviour of anatase $TiO_2$ with organic coating has been investigated extensively in this study. The yield stress was measured over a wide range of solids concentration and pH using stress-controlled and speed-controlled rheometers. The organic treatment leads to a shift of the isoelectric point (IEP) from around pH 5.5 to pH 2.4. A maximum yield stress occurs in the vicinity of the isoelectric point determined by electrokinetic measurements. The transition of rheological behaviour between elastic solid and viscous liquid is represented by a stress plateau in a plot of stress against strain. It is hypothesised that the slope of the stress plateau reflects the uniformity of the structure, and hence the distribution of bond strength. Altering the concentration and the surface chemistry can vary the bond strength and its distribution. therefore, resulting in different type of failure: "ductile-type" or "brittle-type". pH and volume fraction dependence of yield stress could be described quantitatively using existing models with reasonable agreement.easonable agreement.

• 소성∙가공
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• 제14권4호
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• pp.319-326
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• 2005

In this study, the nano-deformation behavior of semi-solid Al-Si alloy was investigated using a molecular dynamics simulation as a part of the research on the surface crack behavior in thixoformed automobile parts. The microstructure of the grain-size controlled Al-Si alloy consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary phase of the grain-size controlled Al-Si alloy were investigated through the molecular dynamics simulation. The primary phase was assumed to be single crystal aluminum. It was shown that the vacancy occurred at the zone where silicon molecules were.