• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.61-66
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• 1992

This paper addresses on the determination of damping coefficients of an infinitely long squeeze film damper operating with an electro-rheological (ER) fluid. The ER fluid behaves as Bingham fluid with an electric field dependent yield shear stress. AS phenomenological model of the fluid is adopted for the relationship between the yield shear and the intensity of the electric field imposed on the fluid domain. The model is then incorporated with the governing equation and associated boundary conditions of the squeeze film damper executing a circula centered orbit for the expression of dimension- less damping coefficients. Numerical simulation is performed to evaluate the performance improvement of the proposed squeeze film damper.

• Tribology and Lubricants
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• v.11 no.5
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• pp.93-98
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• 1995

To increase the information storage density in magnetic disk files, the head, the headdisk spacing must be reduced. This has motivated the investigation of alternatives to the conventional air-lubricated head-disk interface (HDI), which operates at a spacing of about 100 nm. One such alternative under consideration is the liquid-lubricated bearing. To properly model the HDI with a liquid bearing it is necessary to incorporate the theological properties of liquid lubricants at high shear rates. These rheological properties themselves are most easily measured within the HDI. Recently, some question has arisen in the literature concerning the interpretation of the frictional data acquired in this manner. In this study analytical and numerical solutions of the Reynolds eqn. are applied to the starved, liquid lubricated HDI to provide some validation of the rheological data reported the author and coworkers (Streator et al., 1994). Results of the analysis highlight the importance of the inlet taper region in determining the equilibrium configuration of the starved HDI even when only a small fraction of its length is wetted by the lubricant.

• Journal of Dairy Science and Biotechnology
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• v.36 no.2
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• pp.73-80
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• 2018

The textural and rheological properties of cheese are major attributes for the characterization of cheese types, ripening, and consumer preferences. The use of small amplitude oscillatory rheological testing has made it possible for cheese researchers to assess the major properties of cheese, such as melting behavior and storage modulus, without irreversible deformation. In addition, large deformation testing such as textural profile analysis can assess properties such as hardness of cheese. While the sensory properties of cheese are valued by consumers, objective and reliable measurements are paramount for researchers. Ongoing development and refinement of scientific measurement methods of cheese are vital.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.456-462
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• 2009

In comparison to processed wheat flour products, there is no established method for determining the water absorption of rye flour. The aim of this study was to work out a method using the Planetary mixer P 600 for the determination of water absorption (WA) and the rheological properties in rye dough made from rye flours of 4 different types (I-IV). In the correlation analysis showed that WA had positive correlation with ash, beginning of gelatinization, $125-160{\mu}m$ particles, sedimentation values at 20 and 25 min, bread yield, pH, and total titratable acidity, but had negative correlation with initial viscosity, gelatinization maximum, viscosities on swelling at 25, 28, and $31^{\circ}C$. The WA determined by the Planetary mixer P 600 agreed well with the experimental baking tests.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.10a
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• pp.5-9
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• 1995

In the dry-jet-wet-spinning process of a hollow fiber membrane, the polymer solution is pumped into a coaxial tube, jet spinneret. The threadline emerging from the spinneret is stabilized by an internal coagulating medium(liquid or gas) as it emerges from the jet orifice. The nascent hollow thread is further stabilized in a quench bath as shown in Fig. 1. In this scheme, three mechanism of formatiota(temperature gradient, solvent evaporation, and solvent-nonsotvent exchange) can be combined. The changes which promote stabilization often play a dominant role in determining the ultimate fiber wall structure as well. Hence, in pratice, hollow fiber stabilization and development of membrane structure are commonly inseparable. However, fiber dimension(the inside diameter and wall thickness of the hollow fiber) is mainly a rheological problem and is determined by dope pumping rate, spinneret diatance from the coagulation bath, inner coagulant flow rate, and fiber draw-rate. Besides rheological phenomena play a prominent part in the final properties of the hollow fiber.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.495-496
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• 2006

The kneading process and formulations of feedstock obviously affect the quality of MIM products. In the present work, the rheological behaviour of the composite MIM feedstock, metal matrix (Cu) with few additions of ceramic powders $(Al_2O_3)$, was measured by a self-designed/manufactured simple capillary rheometer. Experimental results show that the distribution between powders and binder is more uniformly when blending time increased. Though high powder loading will increase the feedstock viscosity, the fluidity reveals relatively stable through the load curves of extrusion. Besides, the temperature-dependence of viscosity of the feedstock approximately follows an Arrehnius equation. Basing on Taguchi's method, the kneading optimization conditions and the rheological model of the feedstock were established, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.142-143
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• 2021

The purpose of this study is to analyze the extent of the rheology parameters at the segregation boundary of mid-range workability concrete. In addition, it was intended to present the extent of the rheology parameters of the normal strength concrete with segregation resistance using the determination of segregation occurrence of concrete and the use of the rheology parameters. However, it was confirmed that segregation occurs even if the measured rheology parameters is in the range of the suggested rheology parameters. Therefore, it is determined that the conditions under which segregation occurs will provide fundamental data that can be rheological defined. Additional studies are also needed on the relationship between rheological parameters and segregation.

• Korea-Australia Rheology Journal
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• v.19 no.4
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• pp.221-225
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• 2007

Electrorheological characteristics of a dispersed system of phosphorylated potato starch particles in silicone oil investigated via a rotational rheometer equipped with a high voltage generator is being reanalysized. Flow curves of these ER fluids both under several applied electric field strengths and with different degrees of phosphate substitution were mainly examined via three different rheological constitutive equations of Bingham model, De Kee-Turcotte model and our previously proposed CCJ model. Among these, the CCJ equation was found to fit the data of phosphorylated potato starch well.

• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.269-274
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• 1995

For the screening of a new functional exopolysaccharide, sugar composition and rheological properties of exopolysaccharide produced from Xanthomonas sp. EPS-1 were investigated. The average molecular weight of exopolysaccharide was determined to be approximately 2.l $\times$ 10$^{6}$ dalton. The new exopolysaccharide EPS-1 was composed of mannose, glucose, galactose and gluco- samine. IR analysis showed that the exopolysaccharide EPS-1 was assumed to be polymer with carbohydrates. NMR analysis showed that exopolysaccharide EPS-1 was presumed to be 4 units of sugar and trace of CH$_{3}$ group. Exopolysaccharide EPS-1 solution showed a characteristic of non-Newtonian fluid properties. At the concentration of 1.0%, the consistency index and the flow behavior index were shown at 10.8352 poise-sec and 0.4419, respectively. All dispersions were pseudoplastic fluids described accurately by Power-law model. Exopolysaccharide EPS-1 was highly viscous at low concentration, with good stability over a wide range of pH 5 to 13. The excellent compatibility of exopolysaccharide EPS-1 was represented with salts such as sodium chloride.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1005-1011
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• 2004

Squeeze film dampers (SFDs) have been commonly used to effectively enhance the dynamic behavior of the rotating shaft supported by rolling element bearings. However, due to the recent trends of high operating speed, high load capacity and light weight in rotating machinery, it is becoming increasingly important to change the dynamic characteristics of rotating machines in operation so that the excessive vibrations, which may occur particularly when passing through critical speeds or unstable regions, can be avoided. Semi-active type SFDs using magneto-rheological fluid (MR fluid), which responds to an applied magnetic field with a change in rheoloaical behavior, are introduced in order to find its applications to rotating machinery as an effective device attenuating unbalance responses. In this paper, a semi-active SFD using MR fluid is designed, tested and identified by means of linear analysis to investigate the capability of changing its dynamic properties such as damping and stiffness. Furthermore, the proposed device is applied to a rotor system to investigate its potential capability for vibration attenuation: an efficient method for selecting the optimal location of the proposed damper is introduced and control algorithm that could improve the unbalance response properties of a flexible rotor is also proposed.