• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.429-435
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• 2007

The present study proposed a method fer simulating reflective boundary conditions in Boussinesq wave propagation model by lining lateral boundaries like breakwaters and seawalls with artificial sponge layers. In order to find out the reflective characteristics of sponge layers, 1D numerical experiments were performed varying the relative sponge width (sponge width/wave length). The results showed that the reflection coefficient can be effectively realized from no reflection to full reflection simply by adjusting the relative sponge width. Based on the results, a multiple regression formula was proposed to delineate the relationship among the reflection coefficient and other dimensionless variables. Finally, the reflective sponge layer was applied to a semi-infinite breakwater, demonstrating that it can also be successfully employed in 2D applications.

• Membrane Journal
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• v.24 no.1
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• pp.50-62
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• 2014

An asymmetric microfiltration membranes were prepared with polysulfone by an immersion precipitation phase inversion method. Microfiltration membranes were prepared by polysulfone/N-methyl-2-pyrrolidone/polyvinylpyrrolidone/phosphoric acid casting solution and water coagulant. The vapor induced phase inversion method was used to prepare the membranes. The pore size and the morphology were changed by the phosphoric acid additive, the temperature of casting plate and the exposure time at the relative humidity of 74%. The morphology of membranes was investigated by scanning electron microscopy and microflow permporometer. By the addition of the phosphoric acid additive in the casting solution, the morphology of the prepared membranes were changed from a dense sponge structure to a loose asymmetric sponge structure. Due to the addition of catalytic amount of phosphoric acid to NMP casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 3,000 LMH. The temperature of casting plate and exposure time had a apparent effect on the skin layer structure and the pore size and the porosity of the membrane.

• Membrane Journal
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• v.22 no.6
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• pp.450-460
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• 2012

In the submerged membrane-coupled sequencing batch reactor (MSBR) with sponge type media, the effect of media on the removal efficiency and filtration performance were investigated. Dosages of the media in the MSBR were set of 5%, 10%, and 20% based on working volume of reactor. As a control system, the MSBR without media was also operated. The experimental results showed that there was also no difference observed in the removal efficiencies of COD, T-N, and T-P irrespective of the dosages of the media. But TMP (transmembrane pressure) of the MSBR with media increased slowly during the operation time, while that of the MSBR without media increased rapidly at the initial operation. This result was thought that the collisions between flat membrane and moving media gave shear forces which decreased the cake layer on the surface of flat type membrane. Consequently, this study showed that filtration performance of the MSBR with media was greatly enhanced compared with that of the MSBR without media. The MSBR with media suggested in this study can be a good candidate for the wastewater treatment.