• Membrane Journal
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• v.29 no.6
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• pp.362-376
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• 2019

In this study, hydrophilic coating characteristics of PVDF [poly(vinylidene fluoride)] hollow fiber membranes with flower type cross-section prepared by thermally induced phase separation were studied. The hollow fiber used in this study was provided from PureEnvitech Co. Ltd., and the hydrophilic coating experiment was performed with different concentration and number of coating of PEBAX 1657, 2533 and 3533 block copolymer solution using a dip coating method. The hydrophilic coated hollow fiber membrane was characterized to scanning microscope and contact angle measurements to determine the degree of hydrophilization. As a result of SEM characterization, it was confirmed that the thickness of the coating layer increased as the coating concentration increased and the number of coatings increased. Contact angle of surface of hollow fibers decreased as the concentration of the coating solution increased and the number of coatings increased. Gas permeance of oxygen gas was measured for the application of the hydrophilized hollow fiber to Membrane Areated Biofilm Reactor. As a result of gas permeation test, it was confirmed that gas permeance decreased with increasing coating concentration and number of coatings, and the more hydrophilized hollow fiber coated with PEBAX 1657 showed lower gas permeance than those coated with PEBAX 2533 and 3533.

• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.793-800
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• 2008

Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

• Textile Coloration and Finishing
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• v.34 no.1
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• pp.38-45
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• 2022

Sound absorbing materials are being developed in various materials and shapes and they are being applied in many fields such as construction, transportation, civil engineering, and sound. Among many sound-absorbing materials, polyester fiber has no environmental problems and harmfulness, and is a material with good sound absorption properties while being inexpensive. So it is manufactured as a nonwoven sound-absorbing material and used in various fields. In this study, polyester dry-laid nonwoven with different basis weight were manufactured using three types of polyester staple fibers: regular solid, single-hole hollow, and low linear density. We focused on the effects of the properties of the fibers, which constitute nonwovens, on the sound absorption properties, and we considered the basis weight. As the basis weight of the nonwoven fabric increased, the pore size became smaller and the air permeability was lowered, but the sound absorption coefficient was higher. However, the single-hole hollow polyester fiber did not contribute to the increase of the sound absorption coefficient of the nonwoven. It was established that, lower fiber fineness caused the sound absorption coefficient of the nonwoven to be increased. It was also found that the increase in the sound absorption coefficient due to the application of low fineness appeared from a certain basis weight or more.

• Membrane and Water Treatment
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• v.4 no.3
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• pp.157-174
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• 2013

The present study is devoted to the validation of a new method for in line electrokinetic characterisation of deposits on membrane surfaces. This method is based upon simultaneous measurements of transversal streaming potential and permeates flux at constant pressure before and during the deposit formation. Dead-end filtration experiments were conducted with negative flat membranes forming a narrow slit channel, negative hollow fiber membranes and mono-dispersed suspensions of (negatively charged) polystyrene latex and (positively charged) melamine particles at various concentrations. It was observed that the overall streaming potential coefficient increased in absolute value with the deposited latex quantity, whereas it decreased and changed of sign during the filtration of melamine suspensions. By considering a resistance-in-series model, the streaming potential coefficient of the single deposit ($SP_d$) was deduced from the electrokinetic and hydraulic measurements. The independence of $SP_d$ with respect to growth kinetics validates the measurement method and the reliability of the proposed procedure for calculating $SP_d$. It was found that $SP_d$ levelled off much more quickly when filtration was performed through the slit channel. This different behaviour could result from a non-uniform distribution of the deposit thickness along the membrane given that the position of measuring electrodes is different between the two cells.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.18-21
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• 1996

Virus and DNA removal in bio-drug manufacturing processes has received a great deal of attention in recent years. Removing of a virus using a membrane process is a promising method, because inactivated virus can be removed from the bio-drug and the process can be used as an additional and security inactivation after the method of general heat-inactivation of the virus in the bio-drug. The FDA and the biopharmaceutical industry have recently announced strict guidelines for impurities of virus and DNA contamination. The regulatory guidelines on residual amounts of DNA in mammalian cell culture products require DNA contamination of less than 100 pg/dose. Therefore, permeation and rejection of DNA through the porous membranes have become important in the application of DNA removal in bio-drug manufacturing using membrane technology. In this study, the permeation of DNA and chromatin through regenerated cellulose hollow fibers that have a mean pore diameter of 15 nm was investigated.

• Journal of Powder Materials
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• v.19 no.4
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• pp.271-277
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• 2012

$SnO_2$ nanotubes were successfully synthesized using an electrospinning technique followed by calcination in air. The nanotubes were the single phase nature of $SnO_2$ and consisted of approximately 14 nm nanocrystals. SEM and TEM characterizations demonstrated that uniform hollow fibers with an average outer diameter of around 124 nm and wall thickness of around 25 nm were successfully obtained. As anode materials for lithium ion batteries, the $SnO_2$ nanotubes exhibited excellent cyclability and reversible capacity of $580mAhg^{-1}$ up to 25 cycles at $100mAg^{-1}$ as compared to $SnO_2$ nanoparticles with a capacity of ${\sim}200mAhg^{-1}$. Such excellent performance of the $SnO_2$ nanotube was related to the one-dimensional hollow structure which acted as a buffer zone during the volume contraction and expansion of Sn.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.2
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• pp.102-110
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• 2001

To establish an accurate asbestos analysis method for workplace samples, chrysotile, amosite, crocidolite, tremolite, actinolite, and anthophyllite asbestos fibers were analyzed for their morphology, atomic content and electron diffraction patterns. The morphology of asbestos fiber was evaluated in $10,000{\times}$ magnification. The atomic contents was analyzed by X-ray analyzer (TEM-EDX). Asbestos fibers were further assessed using electron diffraction (ED) patterns to provide an additional criterion for classifying the asbestos fibers. Twenty asbestos fibers were initially randomly selected for morphological evaluation; based on an aspect ratio (length : diameter = 3:1). Then the fibers were determined for their EDX spectrums and ED patterns. Our results showed that only chrysotile fiber has a hollow tube structure to be distinguished from other asbestos fibers. Although asbestos fibers had similar morphology, they had different EDX spectrums and ED patterns. Our results on the atomic content of asbestos fibers were very similar to those of other researchers, but amosite and crocidolite had a little difference in atomic content compared with the results from other researchers. The difference may be due to the difference in equipment or asbestos sample selection. A study on asbestos samples from biological specimens to establish a criterion for determining occupational asbestos exposed diseases should be done in the near future.

• Membrane and Water Treatment
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• v.9 no.1
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• pp.43-51
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• 2018

Hollow fiber (HF) membranes are gaining wide interest over flat membranes due to their compaction and high area to surface volume ratio. This work addresses the fabrication of HF from polysulfone (PS) and polyethersulfone (PES) using N-methylpyrrolidone (NMP) as solvent in addition to other additives to achieve desired characteristics. The semi-pilot spinning system includes jacketed vessel, four spinneret block, coagulation and washing baths in addition to dryer and winder. Different parameters affecting dry-wet spinning phase inversion process were investigated. Dope compositions of PES, NMP and polyvinyl pyrrolidone (PVP) of varying molecular weights as additive were addressed. Some critical parameters of importance were also investigated. Those include dope flow rate, air gap, coagulation & washing baths and drying temperatures. The measured dope viscosity was in the range from 1.7 to 36.5 Pa.s. Air gap distance was adjusted from 20 to 45 cm and coagulation bath temperature from 20 to $46^{\circ}C$. The HF membranes were characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and mechanical properties. Results indicated prevalence of finger like structure and average surface roughness from about 29 to 78.3 nm. Profile of stress strain characteristics revealed suitability of the fibers for downstream interventions for fabrication of thin film composite membrane. Different empirical correlations were formulated which enable deeper understanding of the interaction of the above mentioned variables. Data of pure water permeability (PWP) confirmed that the fabricated samples fall within the microfiltration (MF)-ultrafiltration (UF) range of membrane separation.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.224-228
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• 2010

The encapsulation of bacteria may be used to harness them for longer periods of time in order to make them viable, whereas antibiotic treatment would result in controlled release of therapeutic molecules. Encapsulated Escherichia coli GFP (green fluorescent protein) (E. coli GFP) was used here as a model for therapeutic substance - GFP fragments release (model of bioactive substances). Our aim was to evaluate the performance of bacteria encapsulated in hollow fibers (HFs) treated with antibiotic for induction of cell death. The polypropylene-surface-modified HFs were applied for E. coli encapsulation. The encapsulated bacteria were treated with tetracycline in vitro or in vivo during subcutaneous implantation into mice. The HF content was evaluated in a flow cytometer, to assess the bacteria cell membrane permeability changes induced by tetracycline treatment. It was observed that the applied membranes prevented release of bacteria through the HF wall. The E. coli GFP culture encapsulated in HF in vitro proved the tetracycline impact on bacteria viability and allows the recognition of the sequence of events within the process of bacteria death. Treatment of the SCID mice with tetracycline for 8 h proved the tetracycline impact on bacteria viability in vivo, raising the necrotic bacteria-releasing GFP fragments. It was concluded that the bacteria may be safely enclosed within the HF at the site of implantation, and when the animal is treated with antibiotic, bacteria may act as a local source of fragments of proteins expressed in the bacteria, a hypothetical bioactive factor for the host eukaryotic organism.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.250-255
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• 2011

In this study, by using the polymeric membrane separation process, the $CO_{2}/CH_{4}$ separation and $H_{2}S$ removal from biogas were performed in order to $CH_{4}$ purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of $CO_{2}$ and $CO_{2}/CH_{4}$ selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the $CO_{2}$ and $H_{2}S$ were decreased while concentration of $CH_{4}$ was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the $CH_{4}$ recovery ratio in retentate side was increased while the $CH_{4}$ purity in retentate side was decreased.