• Proceedings of the KSME Conference
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• 2001.06e
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• pp.542-547
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• 2001

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 are 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 can 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 in each region after the dye infusion reflects the large scale mixing while the followed slow decay reveals the small scale mixing. The temporal change of concentration probability functions conjectures the two sequential processes in the batch type mixing. An inactive column of water existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• 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 computational fluids engineering
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• v.11 no.4 s.35
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• pp.67-74
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• 2006

The characteristics of turbulent flow and mixing in a small can type combustor are investigated by means of Large Eddy Simulation (LES). Attention is paid for a combustor having a baffle plate with oxidant injection and fuel injection holes and study is made for three cases of different baffle plate configurations. From the result, it is confirmed that mixing is promoted by interaction between the jets during their developing process and large vortical flows generated in the vicinity of the combustor wall or fuel jet front. This particular flow feature is effective to accelerate the slow mixing between fuel and oxidant suffering from low Reynolds number condition in such a small combustor. In particular, the vortical flow region ahead of fuel jet plays an important role for rapid mixing. Discussion is made for the time and space averaged turbulent flow and scalar quantities which show peculiar characteristics corresponding to different vortical flow structures for each baffle plate shapes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.42-47
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• 2004

Air-fuel mixing and flame-holding are two important factors that have to be considered in the design of an injection system. Different injection strategies have been proposed with particular concern for rapid air-fuel mixing and flame-holding. Two representative injection techniques can be applied in a supersonic combustor. One of the simplest approaches is a transverse(normal) injection. The cavity flame holder, an integrated fuel injection/flame-holding approach, has been proposed as a new concept for flame holding and air-fuel mixing in a supersonic combustor. This paper describes numerical efforts to characterize the flame-holding and air-fuel mixing process of a model scramjet engine combustor, where hydrogen is injected into a supersonic cross flow and a cavity. The combustion phenomena in a model scramjet engine, which has been experimentally studied at University of Queensland and Australian National University using a free-piston shock tunnel, were observed around the separation region of the transverse injector upstream and the inside cavity. The results show that this flow separation generates recirculation regions which increase air-fuel mixing. Self-ignition occurs in the separation-freestream and cavity-fteestream interfaces.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.52-58
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• 2005

To establish low-cost and high efficiency water treatment process, feasibility of applying ultrasonic spray nozzle for chemical injection was evaluated. Ultrasonic spray nozzle was manufactured using piezoelectric ceramics. Treatment efficiencies of contaminants by ultrasonic spray nozzle were compared with conventional chemical mixing such as back-mixing. It was found out that the rate of chemical diffusion rate by ultrasonic spray nozzle was faster than by back-mixing method. Removal efficiencies of various contaminants, such as turbidity, organics and microorganism by ultrasonic spray nozzle were also higher than by back-mixing method. By adapting ultrasonic spray nozzle in coagulant injection process, it can be prevented that the decline of treatment efficiency by coagulant overdose. The amount of coagulant can be reduced by applying ultrasonic spray nozzle in water treatment. Along with these advantages chemical mixing chamber is not required if ultrasonic spray nozzle is adapted. From these results, it can be concluded that chemical injection by ultrasonic spray nozzle is an economical and highly efficient device for coagulant mixing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.229-229
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• 2012

Adhesion of Copper film on the aluminum oxide layer formed by anodizing an aluminum plate was enhanced by applying ion beam mixing method. Forming an conductive metal layer on the insulating oxide surface without using adhesive epoxy bonds provide metal-PCB(Printed Circuit Board) better thermal conductivities, which are crucial for high power electric device working condition. IBM (Ion beam mixing) process consists of 3 steps; a preliminary deposition of an film, ion beam bombardment, and additional deposition of film with a proper thickness for the application. For the deposition of the films, e-beam evaporation method was used and 70 KeV N-ions were applied for the ion beam bombardment in this work. Adhesions of the interfaces measured by the adhesive tape test and the pull-off test showed an enhancement with the aid of IBM and the adhesion of the ion-beam-mixed films were commercially acceptable. The mixing feature of the atoms near the interface was studied by scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.53-62
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• 1980

The present work is concerned with the studies on the production of PZT ceramics by newly developed mixing process, which tentatively named "precipitation mixing method", consists of precipitating lead carbontate in the presence of $TiO_2$ and/or $ZrO_2$. Mixtures of $PbCO_3$ and $TiO_2$ or $ZrO_2$ were compared with those obtained by ball-milling with special emphasis on the rate and mechanism of formation of lead titanate and lead zirconate. A possiblity for obtaining PZT ceramics by "precipitation mixing method" was established.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.10-17
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• 2000

This work presents an investigation of aerodynamic characteristics of fuel spray injected from a high pressure hollow cone swirl injector into a constant volume chamber. Laser tomography visualization was used to interrogate the fuel and air mixing characteristics and the effect of chamber pressure and temperature increase was analyzed, Preliminary results on spray development showed that mixing effect tends to increase with the increase of injection pressure and chamber gas pressure yielding a decrease of spray penetration and an attenuation of well-defined vortex structure. Topological analysis of the spray structure has been performed to initiate the understanding of mixing and vaporization process. For the present experimental conditions fuel injection pressure and chamber gas pressure appear as the dominant factors which govern the transient mixing characteristics. Moreover spray atmixation characteristics are improved by increasing chamber gas temperature.

• Communications of the Korean Mathematical Society
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• v.23 no.4
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• pp.597-606
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• 2008

Let {$Y_{ij}-{\infty}\;<\;i\;<\;{\infty}$} be a doubly infinite sequence of identically distributed and ${\rho}^*$-mixing random variables with zero means and finite variances and {$a_{ij}-{\infty}\;<\;i\;<\;{\infty}$} an absolutely summable sequence of real numbers. In this paper, we prove the complete moment convergence of {${\sum}^n_{k=1}\;{\sum}^{\infty}_{i=-{\infty}}\;a_{i+k}Y_i/n^{1/p}$; $n\;{\geq}\;1$} under some suitable conditions. We extend Theorem 1.1 of Li and Zhang [Y. X. Li and L. X. Zhang, Complete moment convergence of moving average processes under dependence assumptions, Statist. Probab. Lett. 70 (2004), 191.197.] to the ${\rho}^*$-mixing case.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.99-112
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• 1997

Mixing process of impinging jets of liquid oxidizer and liquid fuel is simulated by using water and sodium carbonate (Na$_{2}$CO$_{3}$) solution. The shapes of liquid sheets are visualized and flowrate distributions are measured by collecting droplets using measuring cells. Mixing charateristics are studied by using acid-base titration. Stable liquid sheets are formed and two liquid jets are well mixed for symmetric impinging jets. Similarity in flowrate distribution for various measuring heights is observed. For asymmetric impinging jets, liquid sheets become unstable as the difference in the velocities of jets increases. In some extreme cases, liquid sheets are not formed and the jets are separated. Dimensionless variables are adopted demonstrating similarly in flowrate distribution. Mixing characteristics vary significantly with experiment conditions.