• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.241-250
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• 1990

Characteristic relaxation time and characteristic diffusion time of viscoelastic fluids are determined experimentally by measuring the zero-shear-rate viscosity by falling ball viscometer and the infinite-shear-rate viscosity by capillary tube viscometer. Fluids used in experiments are aqueous solutions of polyacrylamide Separan AP-273 and the polymer concentrations range from 300 to 2000 wppm. A newly designed laser beam and timer system is employed to overcome the difficulty in measuring terminal velocities of the low concentration solutions. Ball removal device is prepared to remove the dropped ball from the bottom of cylinder without disturbing the testing fluid. In order to measure the zero-shear-rate viscosity, densities of hollow aluminium balls are adjusted very close to the densities of testing fluids. Characteristic diffusion time, which is ball viscometer. However, terminal velocity of a needle by falling ball viscometer is not affected by the time interval of dropping needles and characteristic diffusion time is not measured with a dropping needle. Powell-Eyring model predicts the highest values of the characteristic relaxation times among models used for heat transfer experimental works for a given polymer solution. As degradation of a polymer solution continues, the zero-shear-rate viscosity decreases more seriously than the infinite-shear-rate viscosity. Characteristic relaxation times of polymer solutions decreases as degradation continues.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.566-574
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• 2023

Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1194-1198
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• 1998

The density and the viscosity of aqueous PEO solutions are observed with the several concentrations of PEO at 20 ℃. The effects of urea on them are also observed. The apparent and the partial specific volumes of PEO are calculated from the density data, which result that the polymer-polymer interaction is dominating in the binary aqueous PEO solutions, while the polymer-solvent interaction is dominating in the ternary aqueous urea-PEO solutions. It is explained by the urea induced breakage of the structured water originated from the hydrophobic interactions and the binding of the urea to the PEO chain. The concentration dependence of relative viscosity and the density dependence of fluidity is also discussed with the concept of the polymersolvent and the polymer-polymer interactions of aqueous urea-PEO solutions.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.177-182
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• 2009

We present the geminate rebinding kinetics measurements of CO to 2-methylimidazole (2-MeIm) bound ferrous protoporphyrin- IX (FePPIX) in alkaline glycerol/water mixtures at 293 K after photolysis. The kinetics was probed by monitoring the CO stretching mode using femtosecond vibrational spectroscopy. When 2-MeIm is used in excess, heme dimers that typically form in low viscosity solutions disappear as the viscosity of the solvent increases. Heme aggregates formed in low viscosity solutions turn monomeric as more 2-MeIm is added, suggesting that 6-coordinated heme, including a strong proximal histidine tends to be in the monomeric form. The vibrational band of CO in the 2-MeIM-FePPIX-CO is well described by a single Gaussian function centered at 1958 $cm^-1$ and 28 $cm^-1$ full width at half maximum. The efficiency and rate of the geminate rebinding of CO to the heme increase with viscosity of the solvent, suggesting that retention of the dissociated CO near the heme, for a longer period by the viscous solvent media, accelerates rebinding.

• KSTLE International Journal
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• v.8 no.1
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• pp.16-20
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• 2007

This study introduces a new approach to a falling ball viscometer by using a high speed motion camera to measure the viscosity of both Newtonian and non-Newtonian fluids from the velocity-time data. This method involves capturing continuous photographs of the entire falling motion of the ball as the ball accelerates from the rest to the terminal velocity state. The velocity of a falling ball was determined from the distance traversed by the ball by examining video tape frame by frame using the marked graduations on the surface of the cylinder. Each frame was pre-set at 0.01. Glycerin 74% was used for Newtonian solution, while aqueous solutions of Polyacrylamide and Carboxymethyl Cellulose were for non-Newtonian solutions. The experimental viscosity data were in good agreements with the results obtained from a rotating Brookfield viscometer.

• Bulletin of the Korean Mathematical Society
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• v.52 no.6
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• pp.1945-1962
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• 2015

This paper is mainly concerned with the formation of delta standing wave for the scalar conservation law with a linear flux function involving discontinuous coefficients by using the self-similar viscosity vanishing method. More precisely, we use the self-similar viscosity to smooth out the discontinuous coefficient such that the existence of approximate viscous solutions to the delta standing wave for the Riemann problem is established and then the convergence to the delta standing wave solution is also obtained when the viscosity parameter tends to zero. In addition, the Riemann problem is also solved with the standard method and the instability of Riemann solutions with respect to the specific small perturbation of initial data is pointed out in some particular situations.

• Korea-Australia Rheology Journal
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• v.12 no.1
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• pp.69-76
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• 2000

We have derived the translation diffusion coefficient and the intrinsic viscosity formula adopting the Kholodenko's theory using 3＋1 dimensional Dirac propagator in the Kirkwood and Riseman scheme. We also performed static light scattering experiments and intrinsic viscosity measurement of dilute solutions of polyimides with different rigidities. In the framework of Kholodenko's theory, we can easily measure the persistence length of polyimide. We prepared five different polyamic acids and polyimides with different degree of imidization by controlling imidization temperatures. From experimental results, we obtained molecular weights and persistence lengths according to the Kholodenko's plot. The molecular weight and the intrinsic viscosity decreased and then increased with the imidization temperature but the persistence length increased monotonically and then leveled off. The persistence lengths calculated from intrinsic viscosities showed very good agreement with those from light scattering experiments.

• Journal of Oral Medicine and Pain
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• v.32 no.4
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• pp.365-373
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• 2007

Destruction of oral soft and hard tissues and resulting problems seriously affect the life quality of xerostomic patients. Although artificial saliva is the only regimen for xerostomic patients with totally abolished salivary glands, currently available artificial salivas give restricted satisfaction to patients. The purpose of this study was to contribute to the development of ideal artificial saliva through comparing viscosity and wettability between CMC solutions and human saliva. Commercially-available CMC is dissolved in simulated salivary buffer (SSB) and distilled deionized water (DDW). Various properties of human whole saliva, human glandular saliva, and a CMC-based saliva substitutes known as Salivart and Moi-Stir were compared with those of CMC solutions. Viscosity was measured with a cone-and-plate digital viscometer at six different shear rates, while wettability on acrylic resin and Co-Cr alloy was determined by the contact angle. The obtained results were as follows: 1. The viscosity of CMC solutions was proportional to CMC concentration, with 0.5% CMC solution displaying similar viscosity to stimulated whole saliva. Where as a decrease in contact angle was found with increasing CMC concentration. 2. The viscosity of human saliva was found to be inversely proportional to shear rate, a non-Newtonian (pseudoplastic) trait of biological fluids. The mean viscosity values at various shear rates increased as follows: stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. 3. Contact angles of human saliva on the tested solid phases were inversely correlated with viscosity, namely decreasing in the order stimulated parotid saliva, stimulated whole saliva, unstimulated whole saliva, stimulated submandibular-sublingual saliva. 4. Boiled CMC dissolved in SSB (CMC-SSB) had a lower viscosity than CMC-SSB (P < 0.01 at shear rate of $90s^{-1}$). 5. For human saliva, contact angles on acrylic resin were significantly lower than those on Co-Cr alloy (P < 0.01). 6. Comparing CMC solutions with human saliva, the contact angles between acrylic resin and human saliva solutions were significantly lower than those between acrylic resin and CMC solutions, including Salivart and Moi-Stir (P <0.01). The effectiveness of CMC solutions in terms of their rheological properties was objectively confirmed, indicating a vital role for CMC in the development of effective salivary substitutes.

• Korean Journal of Food Science and Technology
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• v.16 no.1
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• pp.11-16
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• 1984

Rheological properties of waxy and non-waxy rice starch solutions were evaluated with a narrow gap rotational and Cannon Fenske viscometers. The gelatinized rice starch solutions containing 0.2-1.0% starch displayed pseudoplastic flow behavior. At higher starch level, degree of pseudoplasticity of waxy rice starch solutions increased, while that of non-waxy rice did not changed apparently. The consistency coefficient (K) of non-waxy rice starch solutions increased with increasing gelatinization temperature, but waxy rice starch solutions remained constant, and in alkaline aqueous solutions both of them showed increasing K values. The value of K increased exponentially with an increase in concentration. The effect of the temperature on the viscosity of the solutions followed Arrhenius' type equation, and the activation energies were in the range of 3.675-3.775 kcal/g-mol that were near to that of pure water. The changes of reduced viscosity with concentration were followed Huggin's equation and the values of intrinsic viscosity and interaction coefficient were 0.78-1.59 dl/g and 0.67-2.75, respectively.

• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.178-181
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• 1998

An exopolysaccharide, designated as A49-Pol, was produced from Bacillus polymyxa KCTC 8648P in nitrogen sufficient conditions. The viscosity of the culture broth increased up to $2\times10^4$cP in 38 hours of culture and then decreased to $1.5\times10^4$CP at 48 hours. The $1.0\%$ (w/v) solution of purified A49-Pol represented pseudoplasticity with a viscosity of $2.7\times10^4$cP which was two times higher than xanthan at the same concentration. The viscosity of the A49-Pol solution was also greatly affected by its concentration in comparison with the xanthan solution. The viscosity of $1.0\%$ A49-Pol solution was 930-fold higher than its $0.2\%$ solution, whereas the corresponding viscosities of xanthan solution experienced only l7-fold difference. The viscosity was observed to be maximum at pH 7.0 in both A49-Pol and xanthan solutions, and gradually decreased as the pHs of the polysaccharide solutions went to acidic or alkaline regions. The viscosity of A49-Pol solution was very sensitive to temperature compared to xanthan and decreased with increasing temperature. The viscosity of $0.6\%$ solution of A49-Pol was 8,100 cP at $10^{\circ}C$ and 55 cP at $50^{\circ}C$. The viscosity was also affected by the presence of surfactants such as Span 20 and Triton X-l00 ; with $0.5\%$ Triton X-l00 (v/v), the viscosity of A49-Pol solution increased by $50\%$.