• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.21-28
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• 2000

Although commercial PIV systems have been widely used for the non-intrusive velocity field measurement of fluid flows, they are still under development and have considerable room for improvement. In this study, a single-frame double-exposure PIV system using a high-resolution CCD camera was developed. A pulsed Nd:Yag laser and high-resolution CCD camera were synchronized by a home-made control circuit. In order to resolve the directional ambiguity problem encountered in the single-frame PIV technique, the second particle image was genuinely shifted in the CCD sensor array during the time interval dt. The velocity vector field was determined by calculating the displacement vector at each interrogation window using cross-correlation with 50% overlapping. In order to check the effect of spatial resolution of CCD camera on the accuracy of PIV velocity field measurement, the developed PIV system with three different resolution modes of the CCD camera (512 ${\times}$ 512, lK ${\times}$ IK, 2K ${\times}$ 2K) was applied to a turbulent flow which simulate the Zn plating process of a steel strip. The experimental model consists of a snout and a moving belt. Aluminum flakes about $1{\mu}m$ diameter were used as scattering particles for the liquid flow in the zinc pot and the gas flow above the zinc surface was seeded with atomized olive oil with an average diameter of 1-$3{\mu}m$. Velocity field measurements were carried out at the strip speed $V_s$=1.0 m/s. The 2K ${\times}$ 2K high-resolution PIV technique was significantly superior compared to the smaller pixel resolution PIV system. For the cases of 512 ${\times}$ 512 and 1K ${\times}$ 1K pixel resolution PIV system, it was difficult to get accurate flow structure of viscous flow near the wall and small vortex structure in the region of large velocity gradient.

• Analytical Science and Technology
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• v.11 no.4
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• pp.297-304
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• 1998

The three analysis methods, EPA method 3050, the method offered by Ministry of Environment in Korea, and modified method corrected in this laboratory, were studied to investigate the effect of matrix on the analysis of inorganic priority pollutants. 7 inorganic priority pollutants(Ni, Cr, Cu, Zn, Pb, Cd, Hg) were spiked to the plating, leather, paper, electric, and dye sludges. Mean recovery of the elements except Hg was 95.5% when the procedure of EPA method was applied. However, recovery by the two other extraction methods showed 11.1% and 27.7%, respectively. Digestions were done by MDS (microwave digestion system) and $HNO_3+HClO_4$ methods. To study organic and inorganic matrix effect, samples were made by adding triethanol amine as a organic matrix and $FeCl_3{\cdot}6H_2O$+$AlCl_3{\cdot}6H_2O$ as a inorganic matrix, respectively. The extracts were analyzed by AAS and HG-AAS. Mean recovery of the elements by the $HNO_3+HClO_4$ procedure, except Hg, gave better result than that of the MDS method. Mean recovery of elements was decreased when organic and inorganic matrices were added in the sludge samples. The procedure of MDS and $HNO_3+HClO_4$ digestion gave higher recoveries than that of direct analysis. In general, the results of the studies showed a significant matrix effect on the inorganic priority pollutants analysis in sludges.

• Clean Technology
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• v.8 no.2
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• pp.85-92
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• 2002

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M $H_2SO_4$ solution with 10g of red mud at $85^{\circ}C$ or by reacting 100ml of 9M HCl solution with 10g of red mud at $25^{\circ}C$. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant ($FeCl_3$). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by $FeCl_3$.