• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.80-85
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• 2016

Acoustic cavitation can induce various sonochemical effects including pyrolysis and radical reactions and sonophysical effects including microjets and shockwave. In environmental engineering field, ultrasound technology using sonochemical effects can be useful for the removal and mineralization of recalcitrant trace pollutants in aqueous phase as one of emerging advanced oxidation processes (AOPs). In this study, the effect of liquid height, the distance from the transducer to the water surface, on sonochemical oxidation reactions was investigated using KI dosimetry. As the liquid height/volume increased (40~400 mm), the cavitation yield steadily increased even though the power density drastically decreased. It was found that the enhancement at higher liquid height conditions was due to the formation of standing wave field, where cavitation events could stably occur and a large amount of oxidizing radicals such as OH radicals could be continuously provided.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.622-627
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• 2008

Experiment of active noise control on supersonic jet noise was conducted by use of microjet injection. The microjets were injected to the shear layer of the main jet through 22 small holes at the lip of a rectangular nozzle. Based on the measurement of farfield sound pressure, it was found that the jet noise was effectively reduced by several dB(in some cases up to 10 dB). The power levels of all measurement points were also reduced by use of microjet injection. The microjet affected not only the broadband noise but also the screech tone noise. The sound pressure level, the frequency of the screech tone, and the structure of the jet could be changed by the microjet. Flow visualization with schlieren technique was also made to observe the effect of microjet on the flow field.

• Journal of Environmental Science International
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• v.19 no.3
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• pp.379-387
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• 2010

Sediments of Little Scioto (LS) River in Ohio was contaminated by poor disposal of creosote from Baker Wood Creosoting Facility. Among the primary compounds of creosote, Polycyclic Aromatic Hydrocarbons (PAHs) are the most common ingredient PAHs are known for toxic, carcinogenic and mutagenic compounds. There are many difficulties to remove the PAHs in nature environment because their characteristics are having a less water-solubility, volatile and low mobility properties as increasing the molecular weight. The generation of hydroxyl radicals (${\cdot}OH$) and hydrogen peroxide ($H_2O_2$) forms as well as high temperature (5000 K) and pressure (1000 atm) by a physico-chemical effects of ultrasound during a cavitation collapse can promote the degradation and desorption of PAHs in sediment And it can also produces shock wave and microjets which are able to change the size and surface of particle in solid-liquid system as one of physical effects. Therefore, we explored to understand the role of particle size, the effect of elimination for PAHs concentration by ultrasound and optimize the conditions for ultrasonic treatment. The condition of various size of particles (> $150{\mu}m$, < $150{\mu}m$) and solid-liquid ratio (12.5g/L, 25g/L) for the treatment was considered and ultrasonic power (430 W/L) with liquid - hexane extraction and microwave extraction method were applied after ultrasound treatment.