• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1307-1312
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• 2005

Turbulent in-situ mixing process is a new material process technology to get dispersed phase in nanometer size by controlling reaction of liquid/liquid, liquid/solid and liquid/gas, flow and solidification speed simultaneously. In this study mixing, the key technology to this synthesis method will be studied by computational fluid dynamics. For the simulation of mixing of liquid metal, static mixers will be investigated. Two inlets for different liquid metal meet and merge like 'Y' shape tube. The tube has various shapes such as straight and curved. Also, the radius of curve will be varied. The performance of mixer will be evaluated with quantitative analysis with coefficient of variance of mass fraction. Also, detailed plots of intersection will be presented to understand effect of mixer shape on mixing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.335-344
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• 2006

In this study, sequential mixing model (SMM) was proposed based on the Taylor's theory which can be summarized as the fact that longitudinal advection and transverse diffusion occur independently and then the balance between the longitudinal shear and transverse mixing maintains. The numerical simulation of the model were performed for cases of different mixing time and transverse velocity distribution, and the results were compared with the solutions of 1-D longitudinal dispersion model (1-D LDM) and 2-D advection-dispersion model (2-D ADM). As a result it was confirmed that SMM embodies the Taylor's theory well. By the comparison between SMM and 2-D ADM, the relationship between the mixing time and the transverse diffusion coefficient was evaluated, and thus SMM can integrate 2-D ADM model as well as 1-D LDM model and be an explanatory model which can represents the shear flow dispersion in a visible way. In this study, the predicting equation of the longitudinal dispersion coefficient was developed by fitting the simulation results of SMM to the solution of 1-D LDM. The verification of the proposed equation was performed by the application to the 38 sets of field data. The proposed equation can predict the longitudinal dispersion coefficient within reliable accuracy, especially for the river with small width-to-depth ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.137-142
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• 1997

From the results of study on the electrical characteristics of heat-generation mortar used graphite as fine aggregates is summerized as following. The primary purpose of this study is the mixing ratio of graphite (35%, 50%/Sg), curing conditions (autoclave, steam, surface, underwater) and shape change (length, section of the electric heat-generation mortar). In case of the test condition with the steam curing condition appearance to most excellent heat-generation reproducibility. And temperature a coefficient of electric heat-generation mortar change from is in inverse proportion to the temperature a coefficient of direct proportion as the ratio of graphite mixing increased.

• Nuclear Engineering and Technology
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• v.38 no.8
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• pp.809-818
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• 2006

The existing experimental data related to the turbulent mixing factor in rod arrays is examined and a new definition of the turbulent mixing factor is introduced to take into account the turbulent mixing of fluids with various Prandtl numbers. The new definition of the mixing factor is based on the eddy diffusivity of energy. With this definition of the mixing factor, it was found that the geometrical parameter, ${\delta}_{ij}/D_h$ correlates the turbulent mixing data better than Sid, which has been used frequently in existing correlations. Based on the experimental data for a highly turbulent condition in square rod arrays, a correlation describing turbulent mixing dependent on the parameter ${\delta}_{ij}/D_h$ has been developed. The correlation is insensitive to the Re number and it takes into account the effect of the turbulent Prandtl number. The proposed correlation predicts a reasonable mixing even at a lower S/d ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.11-12
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• 2017

The properties of concrete produced by ready mixed concrete company in Busan were tested. Because the concrete was mixed with blast furnace slag and fly ash, the compressive strength and chloride ion diffusion coefficient were lower than OPC concrete even though the specified concrete strength was same. If the durability about salt attack were satisfied, the concrete of lower specified concrete strength would be adopted to concrete mixing design.

• Journal of the Korean Geotechnical Society
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• v.29 no.3
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• pp.61-70
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• 2013

Evaluation of permeability and coefficient of consolidation of clayey sand is critical in analyzing ground stability or environmental problems such as prediction of pollutant transport in groundwater. In this study, permeability tests using a flexible wall permeameter are performed to derive the coefficient of consolidation and permeability of reconstituted soil samples with various mixing ratios of kaolin clays and two different types of sands, which are Jumunjin and Ottawa sands. The test results indicate that the coefficient of consolidation and permeability plots linearly against clay contents in semi-log scale graphs for low clay mixing ratios ranging between 10 to 30%. It is also demonstrated that coefficient of consolidation and permeability of sand and clay mixture are dependent on the soil structure. Contrary to previous findings, the permeability is shown to be independent of the void ratio at low mixing ratios, which can be classified as non-floating fabric. The permeability decreases with the void ratio for floating fabric.

• 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.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.79-87
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• 2002

The present work analyzed the effect 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. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ 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( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.

• Korean Journal of Remote Sensing
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• v.29 no.6
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• pp.657-662
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• 2013

The comparison between $CO_2$ volume mixing ratios observed by GOSAT and TCCON from September 2009 through November 2012 was performed at Tsukuba and Saga, two downwind sites in East Asia. The temporal trends of $CO_2$ values obtained from GOSAT show good agreement with those observed by TCCON at these two by the TCCON, showing a coefficient of determination ($R^2$) of 0.65. The regression slop we obtained was 0.92, showing a small bias of GOSAT $CO_2$ values compared to those observed by TCCON. However, we found the higher correlation in fall and winter than that in spring and summer. The $CO_2$ volume mixing ratios observ sites. The $CO_2$ volume mixing ratios observed by GOSAT are also in good agreement with those measured ed by GOSAT are in good agreement with those measured by the TCCON at those two sites in fall and winter, showing a coefficient of determination ($R^2$) of 0.66 where as the correlation of determination obtained between GOSAT and TCCON was only 0.27 in spring and summer.

• Atmosphere
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• v.34 no.3
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• pp.283-304
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• 2024

This study analyzed the variability and correlation between ground-level air pollutant concentrations and the atmospheric mixing layer height using data from four types of air pollutants (PM_2.5, PM₁₀, NO₂, and O₃) collected at AirKorea monitoring stations nationwide over a five-year period (2018~2022), and aerosol backscatter data observed by the Vaisala CL31 to derive atmospheric mixing layer heights. The five-year trends and variability of ground-level air pollutant concentrations under seasonal and hourly conditions were examined, as well as the seasonal distribution and diurnal variation of the atmospheric mixing layer height. Five correlation coefficient methodologies were applied to analyze the correlations between ground-level air pollutants and atmospheric mixing layer height under various seasonal and hourly conditions, confirming the dilution effect of the atmospheric mixing layer height. The results showed that PM_2.5, PM₁₀, and NO₂ generally had negative correlations with the atmospheric mixing layer height, while O₃ showed a strong positive correlation up to an altitude of 1,200~1,500 meters, and a negative correlation beyond that altitude. It was also shown that a single high concentration event (e.g., PM₁₀) can alter the overall correlation. The correlation can also vary depending on the characteristics of the correlation coefficient methodology, highlighting the importance of applying the appropriate methodology for each case during the analysis process.