• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.60-67
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• 2018

As the lack of specific aggregation intensifies, the development of alternative resources is urgent. Construction waste is increasing every year, but recycled aggregate is used as a low value added material. Various studies are currently underway at the national level. In this paper, the mechanical performance of the concrete according to the concrete mixing method and the replacement amount of the circulating coarse aggregate was compared and evaluated. Concrete mixing method was normal mixing approach(NMA) method, two-stage mixing approach1 (TSMA1) method, two-stage mixing approach2 (TSMA2) method. Fresh concrete was tested for air content, slump test, and unit volume weight. Compressive strength and flexural strength were tested in hardened concrete. According to the TSMA method, the mechanical performance difference of concrete is shown, and the strength is decreased according to the circulating coarse aggregate replacement amount.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.5
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• pp.492-501
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• 2001

The use of alginate impression materials today is prevalent because of its efficiency and simplicity in clinical settings. Unfortunately, the simplicity of the procedure tends to lull the dentist into a sense of well-being, and lead him into using careless or sloppy technique. Alginate impression materials are used to fabricate diagnostic and preliminary casts, and the final cast. Incorrect use of this material is known to affect the accuracy of the final prosthesis. The purpose of this study was to compare the effect of different mixing methods of alginate impression material and tray adhesive on the accuracy of the stone cast produced by each method. A total of 30 stone casts were produced by using 3 different types of mixing methods (10 stone cast for each mixing method, respectively). The first method utilized an automatic-mixing machine to mix alginate while the second method was carried out manually, strictly following manufacturer's instructions. The third method also involved manual mixing, but did not follow the manufacturer's instructions and was done in a random fashion. Also, 20 additional stone casts were produced by using alginate with or without tray adhesives were included in the study to evaluate effects of tray adhesives on the accuracy of alginate impression. 10 stone casts were produced by adding tray adhesives to the interior surface of the impression tray prior to taking the impression. The other 10 excluded this step. A total of 50 stone casts were analyzed by the three-dimensional measuring machine to measure and compare the dimensional changes of the impression material of each group. The results are as follows. 1. No significant difference was found between the automatic mixing group and the manually-mixing group(p>0.05). 2. For the group that followed manufacturer's instructions, less dimensional changes were record ed than the group that didn't in measuring distanced 4(p<0.05). 3. The group that used tray adhesives showed less dimensional changes(p<0.05). The findings revealed that mechanical methods of mixing alginate impression materials had little influence on dimensional changes. However, it is proven that following manufacturers instructions in alginate impression taking is an important step in acquiring accurate impressions and tray adhesives may play an important role in enhancing the results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.430-437
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• 2006

The mixing effect is studied by comparing rotating and oscillating stirrers in the micro channel. The cases of Re=10 to 80 with various stirring speeds are considered to analysis the effect of Re and stirrer speed for the mixing. Under Re=20, the oscillating stirrer represents better mixing rate than the rotating stirrer up to the critical stirrer speed which has a maximum efficiency. Over Re=30, the results of oscillating and rotating stirrer show that the faster the stirrer speed, the higher the mixing effect within the concerned stirrer speed range and the oscillating stirrer keeps the higher mixing rate. It was found that the mixing effect is a function which has an optimum of the Reynolds number and the stirrer speed. The D2Q9 Lattice Boltzmann Method is used due to the merits of calculation for the unsteady flow with moving boundary.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.929-936
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• 2004

In the present work, shape of the mixing vane in Plus7 fuel assembly has been optimized numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis of flow and heat transfer. Standard $k-{\epsilon}$ model is used as a turbulence closure. The Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of friction loss. Bend angle and base length of mixing vane are selected as design variables. Thermal-hydraulic performances for different shapes of mixing vane have been discussed, and optimum shape has been obtained as a function of weighting factor in the objective function.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.513-514
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• 2006

A CFD analysis for a thermal mixing experiment during steam jet discharge was performed to develop the analysis methodology for the thermal mixing between steam and subcooled water and to find the optimized numerical method. In the CFD analysis, the steam condensation phenomena by a direct contact was modelled by the so-called condensation region model. The comparison of the CFD results with the test data showed a good agreement as a whole, but a small temperature difference was locally found at some locations. However, the commercial CFD code of CFX4.4 together with the condensation region model can simulate the thermal mixing behaviour reasonably well when a sufficient number of mesh distribution and a proper numerical method are adopted

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.62-68
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• 2001

It is a serous subject for energy conservation to prevent the energy loss caused by the mixture of heated and cooled air jets in perimeter and interior zone of a building operated with tow kinds of air-conditioning system simultaneously. The purpose of this paper is to clarify the quantitative and qualitative mechanisms of mixing loss and to propose a evaluation method for it. By using the dynamic heat load calculation, heat extraction load of a typical office building in Busan are calculated. According to the results, numerical simulations based on CFD(Computational Fluid Dynamics) were performed in order to evaluate mixing loss in the physical size of HVAC system. Then, the distributions of air temperature and airflow patterns according to the differences of set-point temperature are analyzed to grasp relations how to influence mixing loss.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.7-13
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2495-2500
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• 2008

We simulated the mixing characteristics in micro T-channel using Lattice Boltzmann Method. We studied the relation a mixing length and pressure-drop due to inlet and outlet ration in Reynolds number 0.5, Peclet number 500 and Schmidt 1000. The ratio of a down-inlet to up-inlet was $0.5{\sim}1.5$ times, up-inlet to outlet was $1{\sim}3$ times and outlet length was 250 times to up-inlet. The mixing length decrease linearly as outlet ratio decreased, and pressure-drip increase non-linearly. Initial stage of micro channel mixture was fast by down-inlet ratio, however, the mixing length is not influence.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.275-281
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• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method was employed to simulate mixing performance of Passive mixer in a micro-channel. It physically analyzed stream line and Pressure drop for passive mixer in a micro-channel. The flow characteristics in a micro-channel was a function of Peclet number. The results indicated that the size of static element was more effect on the mixing than the number of static element and the distance of static elements.