• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.270-275
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• 2009

Sound absorption characteristics of membrane system which are used in stadiums and arenas were investigated. Theoretical studies on acoustic properties of single and double leaf permeable membrane conducted. Also, experimental studies on sound absorption characteristics of combined membrane system that is composed of outer and inner membrane material were conducted. In this study, sound absorption characteristics of each membrane were investigated by experiments in reverberation chamber. 4 types of permeable membranes and a non-permeable membrane were used for experiments. Air space behind membrane material and tension on the membrane was varied. Sound absorption performance of permeable membrane materials was confirmed. As increasing air space behind the membrane material, sound absorption coefficient was increased. In a resonance absorption frequency band sound absorption coefficient varied more dramatically. Sound absorption characteristics were flat in mid and high frequency range and sound absorption coefficient was from 0,3 to 0,5. Also sound absorption coefficient was increased by the increment of surface density and air permeability of membrane. However, over the certain value of air permeability, sound absorption coefficient was decreased. These results can be used as design factors and method for the room acoustic design of dome-stadiums and large free-form buildings.

• Membrane and Water Treatment
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• v.6 no.2
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• pp.141-160
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• 2015

This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases.

• Membrane Journal
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• v.9 no.3
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• pp.151-156
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• 1999

Silicone was used in this study to enhance the oxygene permeability of gas separation membranes. PMP and PMMA were used to prepare the copolymers and IPN membranes, respectively. In the case of copolymers, there were two methodsCswelling and solvent evaporation) in this study and it was revealed that this preparation method affected the oxygene permeability. It was also shown that the IPN method brought the enhacement of oxygen permeability and slight decrease of separation factor. Regarding oxygen permeability 10 wt% of PMMA was the best composition of IPN membrane.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.2
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• pp.177-183
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• 2020

To utilize hydrogen energy, high-yield, high-purity hydrogen needs to be produced; therefore, hydrogen separation membrane studies are being conducted. The membrane reactor that fabricates hydrogen needs to have high hydrogen permeability, selective permeability, heatresistant and a stable mechanical membrane. Dense membranes of Pd and Pd alloys are usually used, but these have drawbacks associated with high cost and durability. Therefore, many researchers have studied replacing Pd and Pd alloys. Dense TiN membrane is highly selective and can separate high-purity hydrogen. The porous alumina has a high permeation rate but low selectivity; therefore, separating high-purity hydrogen is difficult. To overcome this drawback, the two materials are combined as composite reclamations to produce a separation membrane with a high penetration rate and high selectivity. Accordingly, TiN-alumina was manufactured using a high-energy ball mill. The TiN-alumina membrane was characterized by X-ray diffraction analysis, scanning electron microscopy, and energy dispersive spectroscopy. The hydrogen permeability of the TiN-alumina membrane was estimated by a Sievert-type hydrogen permeation membrane apparatus. Due to the change in the diffusion mechanism, the transmittance value was lower than that of the general TiN ceramic separator.

• Korean Membrane Journal
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• v.6 no.1
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• pp.44-54
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• 2004

Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

• Membrane Journal
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• v.22 no.5
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• pp.352-358
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• 2012

In this study, we found structure-property relationship for pressure retarded osmosis (PRO) membrane, between BPS-XX and BisA-XX having similar structure but different free volume. And this comparison was subdivided by controlling its sulfonation degree. BPS-XX and BisA-XX were prepared via a polycondensation reaction. The degree of sulfonation were 20 to 60 mol.%. And they were fabricated to membrane. Characteristics were analyzed to verify of free volume. And the results showed that increase of free volume normally lead to increase permeability and decrease selectivity in equivalent molecule structure. Finally, in the permeability-selectivity results, we conclude high permeability and selectivity membrane can be prepared by controlling molecular structure and free volume.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.90-93
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• 2004

In this study, we have reported an organic-inorganic hybrid membrane, which exhibits an asymmetric structure consisted of a carbonized skin layer and a polyimide porous substructure, to synthesize a novel gas separation membrane combining high gas permeability and selectivity. Both the gas permeability and selectivity of the carbonized layer significantly enhanced when compared with those determined in the control polyimide.

• Korean Journal of Weed Science
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• v.5 no.1
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• pp.85-88
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• 1985

Leakage of electrolytes from leaf discs of treated bean (Phaseolus velgaris L.) plant was the criterion used to investigate the effect of four herbicides on the permeability of leaf-cell membrane. CGA 82725 (2-propynyl 2-((3, 5-dichloro-2 pyridinyl) oxy) phenoxy prpanate) at $10^{-3}M$ increased significantly cell membrane permeability within 1 h after 12 h treatment. Significant increase in cell membrane permeability was also detected at $10^{-2}M$ of DOWCO 453 (Haloxy-methyl 2-(4 (3-chloro- 5-(trifuluoromethyl)-2-pyridinyl) phenoxy) propanate. The effect of dinoseb (2-(1-methylpropyl)-4, 6-dintrophenol) on cell premeability was detected at $10^{-4}M$ after 12h. The highest conductivity measurement was obtained from paraquat (1, 1'- dimethyl-4, 4'-bipyridinium ion). Increase in cell membrane permeability was not always associated with injury symptoms such as appearance of necrotic area in leaves.

• Membrane Journal
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• v.24 no.2
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• pp.136-141
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• 2014

In this study, cellulose acetate (CA) membrane was prepared by phase inversion precipitation and then evaluated the forward osmosis (FO) membrane performance. Differences in water flux and salt rejection between RO and FO with prepared membranes were observed. The different structure membranes were prepared with various solvent which evaluate the influence of membrane structure on permeability. The structure of the prepared membrane was confirmed through scanning electron microscopy (SEM) and the permeability changes were estimated using the bench-scale FO test equipment.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.453-460
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• 2018

The impact of sodium hydroxide, which is one of chemicals of clean in place (CIP) for removing membrane fouling, on the PVDF membrane is reviewed with respect to physical/chemical structural change, the permeability affected therefrom. Based on the cleaning concentration applied in membrane water treatment facilities, 10% of accumulated defluorination was confirmed up to 166g.hr/L which reflects the exposure time. However, membrane resistance was confirmed to be reduced by about 10%. Through FT-IR and EDS analysis, reduction of F and change of are confirmed as factors that affect the permeability of membrane. Membrane resistance, which affects permeability, is affected by loss of additives for hydrophilicity, rather than defluorination of PVDF material. Therefore, in order to check membrane degradation degree, an accelerated test by NaOH was carried out, loss of additives was confirmed, and then PVDF inherent characteristic was observed.