ORCID Profile
0000-0002-5713-112X
Current Organisations
National Institute of Advanced Industrial Science and Technology
,
Graduate University For Advanced Studies
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Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 09-2013
Publisher: IOP Publishing
Date: 07-09-2015
Publisher: IWA Publishing
Date: 24-12-2014
DOI: 10.2166/WS.2014.135
Abstract: The effects of heat treatment on membrane fouling resistance and the rejection of small and neutral solutes by reverse osmosis (RO) membranes were elucidated. RO membrane modification by heat treatment reduced fouling and improved boron rejection. However, heat treatment also caused a decrease in the water permeability of RO membranes. Significant improvement on fouling resistance by heat treatment was observed when RO concentrate was used to simulate a feed solution with high fouling propensity. The improved fouling resistance is likely to be due to changes in the hydrophobic interaction between the membrane surface and foulants. Boron rejection by the ESPA2 membrane was enhanced by heat treatment from 26 to 68% (when evaluated at the permeate flux of 20 L/m2 h). Positron annihilation lifetime spectroscopy revealed that heat treatment did not significantly influence the free-volume hole-radius of the membrane active skin layer. The results reported in this study suggested that changes in the other membrane properties such as free-volume fraction and thickness may be the main cause improving boron rejection.
Publisher: Elsevier BV
Date: 07-2015
Publisher: AIP Publishing
Date: 02-2019
DOI: 10.1063/1.5060619
Abstract: We constructed a new apparatus, built upon a trap-based slow positron beam, for the production of a collimated, energy-tunable positronium beam under ultra-high vacuum conditions employing the photodetachment of positronium negative ions. A slow positron generator consisting of a 22Na radioisotope (20 mCi) combined with a buffer-gas positron trap is employed to generate high-quality, nano-second positron bursts with a repetition rate of 1 Hz–1 kHz. The positron bursts are focused onto an efficient positron-to-positronium negative ion converter, a Na-coated W thin film in a transmission geometry, using a magnetic lens system. The ions emitted from the opposite surface of the film are electrostatically accelerated to a given energy and photodetached by a pulsed infrared laser to form a mono-energetic positronium beam with kinetic energies of 0.2 keV–3.3 keV. The achieved detection rate of Ps atoms is 23 cps at the energy of 3.3 keV with a signal-to-background ratio as high as 300. The energy spread of the beam was evaluated by comparing the result of the time-of-flight measurements and particle-tracking simulations. With the use of a collimator of 1 mm diameter, a coherent beam with an angular ergence of less than 0.3° is obtained. The obtained Ps beam, having a much higher quality than those reported hitherto, will open up a new field of experimental investigations, such as Ps interacting with a variety of materials and fundamental studies on Ps spectroscopy.
Location: Japan
Location: Japan
Location: No location found
No related grants have been discovered for Nagayasu Oshima.