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| 3. |
- Avila, Marta, et al.
(författare)
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Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions
- 2014
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 245, s. 201-209
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Tidskriftsartikel (refereegranskat)abstract
- Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.
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| 4. |
- Burks, Terrance, 1969-, et al.
(författare)
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Studies on the adsorption of chromium(VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles
- 2014
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 425, s. 36-43
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Tidskriftsartikel (refereegranskat)abstract
- Chromium (Cr) in the form of Cr(VI) is deemed toxic in water due to its mutagenic and carcinogenic properties. For the successful removal of Cr(VI), we demonstrate a novel adsorbent consisting of superparamagnetic iron oxide nanoparticles (SPION) functionalized with 3-Mercaptopropionic acid (3-MPA). Fourier transform infrared spectroscopy (FT-IR) confirmed the functionalization of nanoparticles and presence of sulfonate groups. Batch adsorption experiments showed that the functionalized adsorbent recovered 45 mg of Cr(VI)/g of 3-MPA coated SPION at initial concentration of 50 mg/L aqueous solution at pH 1 with less than 1% of Fe dissolution from SPION. The results from X-ray photoelectron spectroscopy confirmed that Cr(VI) chemisorbed onto the adsorbent. Hence, the XPS spectra did not indicate any reduction of Cr(VI) to Cr(III) upon adsorption. The adsorption data were better fitted for the Freundlich model. Moreover, the Cr(VI) adsorption kinetics on functionalized SPION followed a pseudo-second order rate, revealing chemisorption as the dominant mechanism. The high Cr(VI) removal, rapid adsorption kinetics and stability of adsorbent indicate that 3-MPA coated SPION could be an efficient adsorbent for the removal of Cr(VI). (C) 2014 Elsevier Inc. All rights reserved.
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| 5. |
- Cumpstey, Ian, et al.
(författare)
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Amine-linked diglycosides : Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays
- 2011
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 7, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated-4-alcohols gave the 4-amino-pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium-catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino-pseudodisaccharide as the major product, along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4-6)Glc and Man(N4-6)Man diglycosides. The amine-linked diglycosides were found to show weak glycosidase inhibitory activity.
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- De Nardis, L., et al.
(författare)
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Impact of mobility in cooperative spectrum sensing : Theory vs. simulation
- 2012
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Ingår i: Wireless Communication Systems (ISWCS), 2012 International Symposium on. - : IEEE. - 9781467307604 ; , s. 416-420
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Konferensbidrag (refereegranskat)abstract
- This work addresses the problem of cooperative spectrum sensing in cognitive radio networks, focusing on the impact of mobility on performance of cooperative sensing. First, a review of the most recent results on cooperative spectrum sensing is provided, resulting in the identification of measurement correlation and frame error rate in the reporting channel as the main parameters influencing the performance of cooperative sensing schemes. Next, the paper discusses the extension of the analysis to the case of mobile sensors, and determines the set of assumptions made in existing literature when taking into account mobility in sensing. The paper moves then to remove some of such assumptions, by presenting simulation results obtained in presence of realistic models for propagation in the considered area, as well as of a realistic mobility model. A comparison between theoretical derivation and simulation results shows that correlation among measurements taken by different sensors and the selected mobility model may significantly affect the sensing performance.
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| 7. |
- Kennedy, Mark W., et al.
(författare)
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Analytical and FEM modeling of aluminum billet induction heating with experimental verification
- 2012
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Ingår i: Light Metals 2012. - Hoboken, NJ, USA : John Wiley & Sons. ; , s. 269-275
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Konferensbidrag (refereegranskat)abstract
- Induction heating is commonly used in the re-heating of aluminum billets before forging or extrusion. Powerful finite element modeling (FEM) tools are available to assist in the design of such processes; however, such models should be validated by comparison with analytical solutions or experimental results to ensure accuracy. Induction heating experiments have been performed using a number of different coil designs and work piece dimensions at 50 Hz. Aluminum alloys with different electrical conductivities have been used, i.e. 6060 and A356. Process parameters such as: current, power, magnetic field, electrical conductivity, etc. have been measured with high precision instrumentation. Experimental data are presented and compared with equivalent 1D analytical and 2D axial symmetric FEM modeling results. The effect of frequency on the induction heating process is reviewed using the validated analytical and FEM models. Some recommendations are given with respect to appropriate modeling techniques, boundary conditions and numerical mesh sizes.
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| 8. |
- Kennedy, M. W., et al.
(författare)
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Review of classical design methods as applied to aluminum billet heating with induction coils
- 2011
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Ingår i: TMS Annual Meeting. - 9781617827389 ; , s. 707-722
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Konferensbidrag (refereegranskat)abstract
- In the present study classical induction design tools are applied to the problem of heating non-magnetic metal billets, using 50 Hz AC. As an example of great practical industrial interest, the induction heating of aluminum billets is addressed specifically. The predicted work piece power is compared with the measured work piece power for a long and a short coil, using well established methods, such as those of Burch and Davis, introduced in 1926/28, Dwight and Bagai in 1935, Baker in 1944/57, Vaughan and Williamson in 1945, and by Tudbury in 1960. A calculation methodology based on a combination of the available tools is also introduced and discussed. The method has proven to give an error of <10% of the actual work piece power. An equation for Tudbury's work piece shortness correction factor is disclosed for the first time.
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| 10. |
- Mirzaei, B., et al.
(författare)
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On the effect of oxide level in gravity cast A356 aluminium alloy
- 2013
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Ingår i: ICASE 2013 - Proceedings of the 3rd International Conference on Aerospace Science and Engineering. - : IEEE Computer Society. ; , s. 90-100
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Konferensbidrag (refereegranskat)abstract
- Porosity formation in aluminium alloys is strongly dependent on melt cleanliness (oxide level) and its hydrogen content. Porosity phenomenon in aluminium alloys is extremely important in case of critically stressed components such as in aerospace applications. In order to investigate the effect of varying oxide levels (by the addition of anodized plates and oxide rods), series of reproducible castings were produced at a constant hydrogen level, i.e. 0.2 ml/100g melt under carefully controlled conditions. The ALSPEK H probe was used for the measurement of the hydrogen level. The Porous Disc Filtration Apparatus (PoDFA) and Reduced Pressure Test (RPT) were performed in parallel with the casting trials for the melt quality assessment. It has been found that the presence and distribution of the defects is strongly influenced by the melt oxide level. Analysis of fracture surfaces by Scanning Electron Microscope (SEM) shows that the oxides are associated with the pores. The bi-film index and melt inclusions content (mm2/kg) based on the RPT and PoDFA tests, proved to be increased with the oxide additions.
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