• Journal of Powder Materials
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• v.17 no.4
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• pp.270-275
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• 2010

Ethylene glycol-based Cu nanofluids were prepared by pulsed wire evaporation (PWE) method. The structural properties of Cu nanoparticles were studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The average diameter and Brunauer Emmett Teller (BET) surface area of Cu nanoparticles were about 100 nm and $7.46\;m^2/g$, respectively. The thermal conductivity and viscosity of copper nanofluid were measured as functions of Cu concentration and temperature. As the volume fraction of Cu nanoparticles increased, both the enhanced ratios of thermal conductivity and viscosity of Cu nanofluids increased. As the temperature increased, the enhanced ratio of thermal conductivity increased, but that ratio of viscosity decreased.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.203-206
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• 2006

Polyacrylonitrile (PAN) nanofibers, which are pH-sensitive and exhibit soft actuation as a linear actuator and artificial muscles, were prepared by electrospinning to investigate the effect of viscosity on the morphology of PAN fibers. Experimental results revealed that higher viscosity is critical for the formation of unbeaded nanofibers because surface tension is almost constant throughout the experiment. Uniform, smooth, and continuous fibers with diameters of about 700 nm were achieved for the 10 wt% PAN fibers at a flow rate of 0.5 mL/h and an electric field of 0.875 kV/cm.

• Journal of ILASS-Korea
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• v.28 no.2
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• pp.68-74
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• 2023

In this study, the thickness of the liquid sheet formed by a low speed impinging jet onto a wall was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The measurement results were compared with the theoretical predictions for two impinging jets. The wavy surface was observed for low viscosity water, but not for high viscosity glycerol solutions. The sheet thickness decreased as the circumferential angle or the distance from the impinging point increased. The sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions showed some differences from the measurement results.

• Journal of ILASS-Korea
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• v.29 no.2
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• pp.75-82
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• 2024

In this study, the thickness of the liquid sheet formed by a splash plate nozzle at low jet velocities was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The wavy surface was observed for low viscosity water, but not for high viscosity glycerol solutions. The sheet thickness decreased as the circumferential angle or the distance from the impinging point increased. The sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions for two impinging jets showed some differences from the measurement results.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.497-501
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• 2015

Inkjet printing is a widespread technology, offering advantages such as high-quality decoration, a continuous process, and the accurate direct reproduction of patterns or pictures. In inkjet printing technology, the dispersion stability of ceramic ink is one of the most important factors. In this study, the dispersion stability of blue $CoAl_2O_4$ ink for ceramic inkjet printing is systematically investigated. Blue $CoAl_2O_4$ pigment was synthesized by a solid-state reaction and then milled to less than 300nm in size. In order to investigate the influence of the viscosity on the dispersion stability, two types of $CoAl_2O_4$ ceramic inks (termed here Blue L and Blue H) were prepared using different volume ratios of ethylene glycol and ethanol. The Blue L and Blue H ink solutions contained cetyltrimethylammonium bromide(CTAB) as a dispersive agent. The viscosity, surface tension and jetting stability of the $CoAl_2O_4$ ceramic inks were analyzed using a rheometer, a surface tension meter and a dropwatcher. The dispersion stability of the $CoAl_2O_4$ ceramic ink was investigated by a multiple light-scattering method. Blue H, a ceramic ink with higher viscosity, showed much better dispersion stability than the Blue L ceramic ink.

• Journal of the Korean Society of Safety
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• v.28 no.6
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• pp.23-28
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• 2013

In order to improve extinguishing performance of water mist, many studies of additives have been conducted. In this study, viscosity agent which has the ability to improve extinguishing performance by adhering to the surface on fire was used and fluorine-free surfactant was also added to water to enhance water's wetting ability. This study aimed to verify optimal concentration of extinguishing of additives according to fire source and extinguishing performance by comparison with pure water. In case of wood crib fire, the results show that flame suppression and extinguishing time of sodium alginate 0.4 wt.% are 3.4 times and 2.2 times shorter than those of pure water in 0.2 MPa respectively. It seems that large amount of water adhere to surface on fire, thus cooling effect on surface was enhanced. Also water consumption of sodium alginate 0.4wt.% is up to 65% lower than that of pure water. In case of heptane fire, extinguishing time of cocobetaine 0.1 wt.% is 9.7 times shorter than that of pure water in 0.2 MPa. It is thought that because cocobetaine can block oxygen and suppress oil mist by making emulsion film on fire surface due to a low surface tension. On the other hand, water consumption of cocobetaine 0.1 wt.% is 92% lower than that of pure water.

• Journal of the Mineralogical Society of Korea
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• v.16 no.1
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• pp.33-47
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• 2003

Various applied-mineralogical characterization including measurements of surface area, size distribution, swelling index, and viscosity were done for some domestic bentonites in order to decipher the rheological properties and their controlling factors. The bentonites, which are Ca-type and relatively low-grade (rnontmorillonite contents: 30 ∼ 75 wt%), occur mostly as subhedral lamellas with the size range of 2 ∼ 4 $\mu\textrm{m}$. The size distribution of mineral fractions in bentonite suspension is dominant in the range of 10 ∼ 100 $\mu\textrm{m}$, and though rather complicated, exhibits roughly bimodal patterns. The feature is more conspicuous in the case of zeolitic bentonite. The bentonites have surface areas ranging 269 ∼ 735 $\m^2$/g, which are measured by EGME adsorption method. The EGME surface areas are nearly proportional to the rnontmorillonite contents, moisture contents, or total CEC. In the surface area measurements, zeolitic bentonites have slightly higher values than those zeolite- free types. The measured swelling index and viscosity of domestic bentonites are comparatively low in values. The swelling values of bentonites were measured to be 250∼500% at maximum by progressively mixing amounts of 2 ∼ 5 wt% Na$_2$CO$_3$, which varies depending on the contents of rnontmorillonite and other impurities, especially zeolite. Much amount of sodium carbonate is required for optimum swelling property of zeolitic bentonited which has usually strong Na- exchanged capacity. The bentonites, which are comparatively feldspar-rich and low in size and crystallinity, tend to be higher in viscosity values. Tn addition, the viscosity is largely higher in case of the bentonites with higher pH in suspension. However, the rheological properties of bentonites such as swelling index and viscosity do not show any obvious relationships with rnontmorillonite contents and mean particle size in suspension. In contrast, roughly speaking, the swelling index of bentonites is reversely proportional to the values of surface area which can be regarded as a collective physico-chemical parameter encompassing all the effects caused by mineral composition, surface charge, particle size, morphological farm, and etc. in bentonites. Thus, the rheological properties in bentonite suspension appear to be rather complicated characteristics which mainly depend on the flocculation of clay particles and the mode of particle association, i.e. quasicrystals, controlled by surface charge, morphology, size, and texture of rnon-tmorillonite, and which partly affected by the finer impurities such as zeolite.

• Journal of Oral Medicine and Pain
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• v.39 no.3
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• pp.90-95
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• 2014

Purpose: To investigate viscosity and wettability of hyaluronic acid (HA) solutions according to supplementation of lysozyme and/or peroxidase, and different ionic strength and pH conditions. Methods: Solutions containing HA were prepared using distilled deionized water (DDW) and simulated salivary buffer (SSB) in different conditions. Different concentrations of hen egg-white lysozyme and bovine lactoperoxidase was added into HA solutions. HA solutions with antimicrobials in different ionic strength and pH conditions were prepared. Viscosity was measured using cone-and-plate digital viscometer at six different shear rates and wettability on acrylic resin and Co-Cr alloy was determined by contact angle. Results: The viscosity values of HA dissolved in DDW were decreased in order of HA, HA containing lysozyme, HA containing peroxidase, and HA containing lysozyme and peroxidase. The viscosity values for HA in DDW were decreased as the concentration of lysozyme and/or peroxidase increased. However, the viscosity values for HA in SSB showed no significant changes according to the concentration of lysozyme and/or peroxidase. The viscosity values of HA solutions were inversely proportional to ionic strength and pH. The contact angle of HA solutions showed no significant differences according to tested surface materials, addition of lysozyme and/or peroxidase, and different ionic strength and pH conditions. Contact angles on acrylic resin by HA solutions in all tested conditions were much higher than those by human saliva. Conclusions: The rheological properties of HA supplemented with lysozyme and/or peroxidase in different ionic strength and pH conditions were objectively confirmed, indicating the possibility of HA with lysozyme and/or peroxidase as main components in the development of effective saliva substitutes.

• Journal of Korea Water Resources Association
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• v.33 no.1
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• pp.39-50
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• 2000

Generally speaking, a hydrodynamic model needs a friction coefficient (Manning coefficient or Chezy coefficient) and eddy viscosity. For numerical solution the coefficients are usually determined by recursive calculations. The eddy viscosity in numerical model plays physical diffusion in flow and also acts as numerical viscosity. Hence its value has influence on the stability of numerical solution and for these reasons a consistent evaluation procedure is needed. By using records of stage and discharge in the downstream reach of the Han river, I-D models (HEC-2 and NETWORK) and 2-D model (SMS), estimated values of Manning coefficient and an empirical equation for eddy viscosity are presented. The computed results are verified through the recorded flow elevation data.n data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.258-265
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• 2016

Digital printing has been used in various industrial areas, including semiconductor manufacturing and textile printing. However, implications on ceramic textile have not been well established so far. Printing high-viscosity materials requires an understanding of their behavior. An inorganic high viscous material with a viscosity range of 20-30 cps is analyzed using a viscometer and through X-ray diffraction. In this study, a digital printer is designed and assembled using a high-viscosity material with software for PC control, resulting in reduced processing at a fast area velocity of $20m^2/hr$. The present study demonstrated that the printer is capable of controlling the shape of the drop mass to smear ink smoothly onto the ceramic surface under an economic budget. In addition, to avoid any difficulty in color management, the ceramic printer is equipped with an independent color management system designed to cope with images on a highly viscous material.