• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.3
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• pp.311-318
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• 2003

The present work evaluates the effects of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly. by obtaining velocity and pressure fields. turbulent intensity. flow-mixing factors. heat transfer coefficient and friction factor using three-dimensional RANS analysis. Four different shapes of mixing vane. which were designed by the authors were tested to evaluate the performances in enhancing the heat transfer. Standard k-$\varepsilon$ model is used as a turbulence closure model. and. periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant. but the twist angle of mixing vane is changed. The results with three turbulence models were compared with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.8 s.251
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• pp.796-805
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• 2006

In this study, the problem of using the mixing index as a measure of the mixing performance for a certain flow field has been discussed. The flow model subjected to this study is the two-dimensional unsteady lid-driven cavity flow. The transport equation for the concentration within the cavity was solved by using the finite volume method where the convective terms are discretized with the central difference scheme. It was shown that both the concentration dispersion and the mixing index depend highly on the initial distribution of the concentration, and therefore the mixing index obtained from the concentration dispersion equation loses its universal applicability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1145-1152
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• 2002

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields was obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera could be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter. height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration after the dye infusion reflects the large scale turbulent mixing while the fellowed slow decay reveals the small scale molecular mixing. The temporal change of concentration variance field conjectures the two sequential processes for the batch type mixing. An inactive column of water is existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• Journal of the Korean Society of Visualization
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• v.16 no.2
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• pp.53-58
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• 2018

This paper presents an electromagnetically driven microrobot for the enhancement of mixing performance in high viscous liquid media such as blood and bone marrow. First, an electromagnetic system was fabricated, and the magnetic flux density generated from the system was compared with the theoretical value. Second, the reciprocating motion of the microrobot was demonstrated in microchannel using electromagnetic system. As a proof of concept, the mixing performance by the electromagnetically driven microrobot in high viscous liquid was investigated using safranin solution. As a result, it was completely mixed within 140 s with the reciprocating motion of the microrobot while it took 1680 s for natural diffusion. In addition, the mixing efficiency was quantitatively evaluated through a mixing index obtained by an image analysis. The proposed method provides not only wireless actuation of a microrobot with a simple design but also high mixing performance in variety of high viscous liquid media.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.31-34
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• 2004

Carbon nanofiber exhibits superior and often unique characteristics of mechanical, electrical chemical and thermal properties. In this study, For improvement of the mechanical properties of composites, carbon nanofiber reinforced hybrid composites was investigated. For the effect of dispersion, The dispersion methods of solution blending and mechanical mixing were used. The mixing of solution blending method was used using ultrasonic. Dispersion of carbon nanofiber was observed by scanning electron microscope (SEM). Mechanical properties were measured by universal testing Machine (UTM).

• Korea-Australia Rheology Journal
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• v.18 no.3
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• pp.153-160
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• 2006

We analyzed the non-Newtonian and non-isothermal flow with Carreau-Yasuda viscosity model in co-rotating and counter-rotating twin screw extruder systems. The mixing performances with respect to the screw speed, the screw pitch, and the rotating direction have been investigated. The dynamics of mixing was studied numerically by tracking the motions of particles. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the average strain. The results showed that the high screw speed decreases the residence time but increases the deformation rate. Small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance, while the small screw pitch increases the distributive mixing performance. Co-rotating screw extruder has the better conveying performance and the distributive mixing performance than counter-rotating screw extruder with the same screw speed and pitch. Co-rotating screw extruder developed faster transport velocity and it is advantageous the flow characteristics to the mixing that transfers polymer melt from one barrel to the other barrel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.904-912
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Barrier Embedded Kenics Micromixer (BEKM). In the BEKM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: (i) splitting/reorientation by helical elements inside the microchannel and (ii) stretching/folding via periodically located barriers on the channel wall. The fully three-dimensional geometry of BEKM was realized by a micro-stereolithography technology, in this study, along with a Kenics micromixer and a circular T-pipe. Mixing performances of three micromixers were experimentally characterized in terms of an average mixing color intensity of phenolphthalein. Experimental results show that BEKM has better mixing performance than other two micromixers. Chaotic mixing mechanism, proposed in this study, could be integrated as a mixing component with Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.140-155
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• 2002

Void-free impression taking is important for the fabrication of accurate dental restorations. One of the essential properties of an impression material used for indirect fabrication of precision castings is the reproduction of the fine detail. The objective in this study was to determine the influence of mixing methods on the number of voids and surface detail reproduction. The number of voids and surface detail reproduction were evaluated with the steteomicroscope $SZ-PT^{(R)}$ and photographed. The results were as follows ; 1. In comparison of the void formation according to mixing methods of all impression materials, mechanical mixing was better than hand mixing and there was significant difference(p<0.05) 2. In comparison of the void formation according to hand mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA \;FINE\;DF\;III^{(R)}$), there was no significant difference among alginate groups. But the number of void was increased in the order of $Panasil^{(R)}\;contact,\;TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}$ light bodied and there was significant difference (p<0.05). 3. In comparison of the void formation according to mechanical mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA FINE\;DF\;III^{(R)}$), there was no significant different among alginate groups. But the number of void was decreased in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}light\;bodied,\;Panasil^{(R)}$ contact and there was significant difference (p<0.05). 4. In comparison of the surface detail reproduction according to mixing methods of 3 types of impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}\;light\;bodied,\;Panasil^{(R)}\;contact$), there was no significant difference between hand mixing and mechanical mixing method 5. The surface detail reproduction was only influenced by impression materials, and produced better in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Panasil^{(R)}\;contact,\;Permlastic^{(R)}$ light bodied. There was significat difference among 3 type of impression materials(p<0.05). From the above results, void formation is influenced by mixing methods and surface detail reproduction is influenced by impression materials than mixing methods. Therefore, to fabricate accurate restorations, proper impression material and mechanical mixing method are more effective and available clinically.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.6-13
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• 2017

This study examines the effect of the type and number of orifices in an in-line mixer to improve the mixing performance and pressure loss. Recently, in-line non-power-consuming mixers have been increasingly used to complement mechanical mixers, which have a long dwell time, noise, excessive energy consumption, and high maintenance costs. An in-line mixer with an orifice for efficient mixing in water treatment was examined by numerical analysis using the commercial code FLUENT. The flow characteristics of pressure loss and velocity distribution within the mixer and the mixing efficiency were compared with and without the orifices. The CFD results show that the mixing efficiency was improved, but the pressure loss was increased by the in-line mixer with an orifice. A sensitivity study was also done on the principal parameters.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.9-13
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• 2002

This study has been performed to investigate the physical and mechanical characteristics of compaction, volume change and compressive strength for reinforced soil mixed with cement. And confirm the reinforcing effects with admixture such as cement. To this end, a series of compaction test and compression test was conducted for clayey soil(CL) and cement reinforced soil. In order to determine proper moisture content and mixing ratio, pilot test was carried out for soil and cement reinforced soil. And the mixing ratio of cement admixture was fixed 3%, 6%, 9% and 12% by the weight of dry soil. As the experimental results, the maximum dry unit weight(${\gamma}_{dmax}$) was increased with the mixing ratio and then shown the peak at 10% reinforced soil, but the optimum moisture content(OMC) and the volume change was decreased with the ratio increase. And the compressive strength volume change was decreased with mixing ratio increased.