• KSTLE International Journal
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• v.10 no.1_2
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• pp.37-42
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• 2009

This paper presents the characteristics of volumetric efficiency of an axial type piston pump considering the piston tilting. A numerical analysis is carried out in order to obtain the pressure distribution considering the fluid inertia at the notch of the valve plate. The cylinder pressure variation and the discharge flow rate are measured experimentally according to the operating conditions such as supply pressure, rotational speed, and viscosity of the working fluid by using the cam type test apparatus. Leakage is also measured considering piston tilting. The characteristics of the volumetric efficiency are analyzed with respect to various operating conditions and leakage is also analyzed according to the piston tilting angle. Results are applicable to improve the design of an axial type piston pump.

• International Journal of Fluid Machinery and Systems
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• v.8 no.1
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• pp.36-45
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• 2015

Oil and gas industry pumps viscous fluids and investigation of flow physics is important to understand the machine behavior to deliver such fluids. 3D numerical flow simulation and analysis for different viscous fluids at different rotational speeds of a centrifugal impeller have been reported in this paper. Reynolds-averaged Navier Stokes (RANS) equations were solved and the performance analysis was made. Standard two equation k-${\varepsilon}$ model was used for the turbulence closure of steady incompressible flow. An inlet recirculation and reverse flow in impeller passage was observed at low impeller speeds. It was also found that the higher viscosity fluids have higher recirculation which hinders the impeller performance.

• Journal of Information Display
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• v.13 no.4
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• pp.145-149
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• 2012

Liquid crystals are useful for a wide range of applications due to their exceptional properties. Doping of liquid crystals with carbon nanotubes (CNTs), even at very low concentrations, produces a detectable effect on the liquid crystal (LC) properties that can be very attractive for various functions. In this study, an attempt was made to investigate the effect of CNTs on the electrical properties of a short-pitch and high-spontaneous-polarization ferro-electric LC mixture, FLC-6304, at different temperatures. The inclusion of the CNTs significantly reduced the polarization at temperatures well within the $SmC^*$ phase, but the effect was gradually reversed as the transition temperature was approached. The insertion of the CNTs also reduced the response time and the rotational viscosity of the FLC mixture, which is highly desirable in the LCD industry.

• Journal of Microbiology and Biotechnology
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• v.3 no.4
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• pp.292-297
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• 1993

Aspergillus niger No. PFST-38 was grown on complex media in 30L agitated fermentors at various aeration rates and stirrer speeds. We could correlate the mixing time as a function of the Reynolds number and the apparent viscosity, as follows. ${\theta}_M=2.95\;\NRe^{-0.52},\;{\theta}_M=1.88\;{\eta_a}^{0.57}$ Also, the effects of the apparent viscosity (${\theta}_a$), the impeller rotational speed (N), the air flow rate ($V_s$), and the mixing time (${\theta}_M$) on the oxygen transfer coefficient, $K_L a$ were determined experimentally, and equated as follows. $K_La=12.04N^{0.88}Vs^{0.71}{n_a}^{-0.83},\;K_La=30.2N^{0.88}Vs^{0.71}{\theta_M}^{-1.45}$ $K_La$ increased as the agitation speed and the air flow rate increased. The rate of $K_La$ increase was dependent more on the rotational speed of impeller than on the air flow rate. The glucoamylase production increased with the increase of the agitation speed upto at 500 rpm and increased with the increase of air flow rate upto at 1.0 vvm. The values calculated from the above equation confirmed that the experimental maximum production of glucoamylase was achieved when the $K_La$ and the apparent viscosity of the broth were $260\;hr^{-1}$ and 1800 cps, respectively.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.737-741
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• 2004

We presents new results for transport properties of dumbbell fluids by equilibrium molecular dynamics (EMD) simulations using Green-Kubo and Einstein formulas. It is evident that the interaction between dumbbell molecules is less attractive than that between spherical molecules which leads to higher diffusion and to lower friction. The calculated viscosity, however, is almost independent on the molecular elongation within statistical error bar, which is contradicted to the Stokes' law. The calculated thermal conductivity increases and then decreases as molecular elongation increases. These results of viscosity and thermal conductivity for dumbbell molecules by EMD simulations are inconsistent with the earlier results of those by non-equilibrium molecular dynamics (NEMD) simulations. The possible limitation of the Green-Kubo and Einstein formulas with regard to the calculations of viscosity and thermal conductivity for molecular fluids such as the missing rotational degree of freedom is pointed out.

• Journal of the Society of Disaster Information
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• v.6 no.1
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• pp.10-24
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• 2010

In this paper, warm asphalt binder was proposed as a substitute for the polymer-modified asphalt binder to get higher viscosity than that of the polymer-modified at the same temperature. Performance grade test and rotational viscosity of warm asphalt binder were conducted to evaluate the property variations due to the addition of admixture. Research results showed that the viscosity of warm asphalt binder at $100^{\circ}C$ was similar to that of the conventional asphalt binder. The performance and durability of warm asphalt binder were also comparable to those of the polymer-modified. It is considered that the active applications of warm asphalt binder can reduce environmental damages due to less diffusions of carbon dioxide compared to the conventional.

• Advances in concrete construction
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• v.16 no.1
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• pp.59-68
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• 2023

In the pumping process, concrete moves along the pipe and experiences both pressure and shear. This changes the workability and flow characteristics of the concrete. However, the effect of pressure and shear on the change in properties of concrete during the pumping process has not yet been accurately identified. This study analyzed the effects of pressure and shear on the properties of concrete during pumping. For quantitative tests, lab-scale test equipment capable of simulating the pressure and shear applied to concrete during pumping was used. For one coarse aggregate type, two paste types, three mortar types, and five concrete types, the effects of pressure, shear, and shear under pressure conditions were examined by varying the maximum pressure (0 to 200 bar) and the rotational speed of the vane for shear (0 to 180 rpm). Under the maximum pressure condition of 200 bar, the water absorption of coarse aggregate increased by 0.62% and that of fine aggregate also increased. When the concrete was under pressure, significant changes (a reduction in a slump and an increase in viscosity and yield stress) compared with the effect of the elapsed time occurred owing to an increase in the water absorption of the aggregates. When both pressure and shear were applied to concrete, both the slump and viscosity decreased. As the rotational speed of the vane increased, changes in properties became significant. Shearing in the absence of pressure maintained the properties of concrete. However, shearing under pressure conditions caused a reduction in slump and viscosity.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1505-1509
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• 2004

The suspension of hardened red blood cells (RBCs) differs from the suspension of normal RBCs with respect to their rheological behavior. The deformability of normal and hardened RBCs (obtained by heating blood at $49^{\circ}C$ or by incubating RBCs in a solution of hydrogen peroxide) was measured with a slit diffractometer and RBC suspension viscosity was measured with a rotational viscometer. The peroxide-treated RBCs showed a significant decrease of the deformability and their suspension viscosity increased over a range of shear rates. The suspension viscosity of the heated RBCs, however, where the deformability is even lower than that of the peroxide-treated RBCs, was slightly higher than that of the normal RBC suspension in the high shear rates. The present study found that not all rigid cells cause an increase of blood viscosity at high shear rate, and therefore that decreased membrane deformability is not predictive of high-shear blood viscosity.

• Tribology and Lubricants
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• v.13 no.4
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• pp.26-32
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• 1997

The heat generation of the angular contact and the deep groove ball bearing is studied experimentally and numerically. The temperature variation of the inner and outer races and the temperature increase distribution are measured for the shaft rotational speeds, preloads, viscosities of the lubricant and lubrication methods. The measured temperature distributions are used as the input data of the numerical simulation to estimate the heat generation rate at the bearing. The temperatures of the inner and outer race increase more rapidly and approach faster to their steady values as the rotational speed increases. The optimal viscosity of the oil to minimize the heat generation is 8~10 cSt at 4$0^{\circ}C$ when the oil-air lubrication method is adopted. The heat generation of the bearing increases with the rotational speed and depends more on the lubrication method than on the preload variation.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.196-201
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• 2001

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. Therefore, there are many practical applications using the ER fluids. ER effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of starch based ER fluid were reported. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply, The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to 200s$^{-1}$ in 2 minutes. This thesis presents Bingham properties of ER fluids subjected to temperature variations. The temperature dependence of the viscosity was determined for ER fluids consisting of 35 weight % starch particles in automatic transmission oil.