A software-defined networking approach for handover management with real-time video in WLANs

Railway Engineering Science - To achieve high performance and reliability in video streaming over wireless local area networks (WLANs), one must jointly consider both optimized association to...     

A system approach to high‐quality picture‐rate conversion

Abstract— Various techniques have been implemented to improve the motion portrayal of flat‐panel displays, of which the widespread introduction of motion‐compensated picture‐rate conversion systems is an essential part. However, a careful design of such systems is critical as they have the potential to introduce perceptually annoying artifacts. In this paper, an overview of the required “ingredients” of high‐quality motion‐compensated picture‐rate conversion is presented, as implemented in state‐of‐the‐art systems‐on‐chip. The visual impact of individual components on picture quality is illustrated.     

Experimental performance of borehole heat exchangers and grouting materials for ground source heat pumps

The system performance of a ground source heat pump (HP) system is determined by the HP characteristics itself and by the thermal interaction between the ground and its borehole heat exchanger (BHE). BHE performance is strongly influenced by the thermal properties of the ground formation, grouting material, and BHE type. Experimental investigations on different BHE types and grouting materials were carried out in Belgium. Its performances were investigated with in situ thermal response tests to determine the thermal conductivity (λ) and borehole resistance (R_b). The line‐source method was used to analyze the results, and the tests showed the viability of the method. The main goal was to determine the thermal borehole resistance of BHEs, including the effect of the grouting material. The ground thermal conductivity was measured as 2.21 W m^?1 K^?1, a high value for the low fraction of water‐saturated sand and the high clay content at the test field. The borehole resistance for a standard coaxial tube with cement–bentonite grouting varied from 0.344 to 0.162 K W^?1 m for the double U‐tube with cement–bentonite mixture (52% reduction). Grouting material based on purely a cement–bentonite mixture results in a high thermal borehole resistance. Addition of sand to the mixture leads to a better performance. The use of thermally enhanced grouts did not improve the performance significantly in comparison with only a low‐cost grouting material as sand. Potential future applications are possible in our country using a mobile testing device, such as characteristics, standardization, quality control, and certification for drilling companies and ground source HP applications, and in situ research for larger systems. Copyright © 2011 John Wiley & Sons, Ltd.     

Smouldering of pine wood: Kinetics and reaction heats

A kinetic model of smouldering of pine wood is determined by thermo-gravimetric analysis (TGA), describing the reactions of wood pyrolysis, wood oxidation and char oxidation. Thermo-gravimetric experiments were conducted with constant heating rates ranging from 2.5 to 10 K/min in atmospheres of pure nitrogen and mixtures of nitrogen and oxygen (with 20.5%, 8.2% and 4.3% O₂). At first wood pyrolysis and char oxidation experiments are carried out in an independent way. Then smouldering experiments are conducted, which combine the two previous reactions with wood oxidation. Finally, the heats of the reactions are determined by differential scanning calorimetry (DSC). The results are discussed, compared with the literature and the derived kinetic model is presented, which includes five components: three pseudo-components of wood – representing roughly cellulose, hemi-cellulose and lignin – as well as char and ashes.     

A search for new Mg- and K-containing alanates for hydrogen storage

In this work Mg- and K-containing alanates have been investigated as possible hydrogen storage materials. Ball milling was carried out under argon or at moderate/high hydrogen pressure in order to obtain an improved driving force for the formation of potential new alanate phases. Powder X-ray diffraction and volumetric measurements were used in order to identify reaction mechanisms and phases forming in these systems. New unidentified peaks were detected for the mixtures 2MgH₂ + 3Al + KH and 2CaH₂ + Al + 2KH. However, they do not seem to belong to reversible hydride phases.     

Biogenic metals for the oxidative and reductive removal of pharmaceuticals, biocides and iodinated contrast media in a polishing membrane bioreactor

Pharmaceutical and personal care products, biocides and iodinated contrast media (ICM) are persistent compounds, which appear in ng to μg L⁻¹ in secondary effluents of sewage treatment plants (STPs). In this work, biogenic metals manganese oxides (BioMnOx) and bio-palladium (Bio-Pd) were applied in lab-scale membrane bioreactors (MBR) as oxidative and reductive technologies, respectively, to remove micropollutants from STP-effluent. From the 29 substances detected in the STP-effluent, 14 were eliminated in the BioMnOx-MBR: ibuprofen (>95%), naproxen (>95%), diuron (>94%), codeine (>93%), N-acetyl-sulfamethoxazole (92%), chlorophene (>89%), diclofenac (86%), mecoprop (81%), triclosan (>78%), clarithromycin, (75%), iohexol (72%), iopromide (68%), iomeprol (63%) and sulfamethoxazole (52%). The putative removal mechanisms were the chemical oxidation by BioMnOx and/or the biological removal by Pseudomonas putida and associated bacteria in the enriched biofilm. Yet, the removal rates (highest value: 2.6 μg diclofenac L⁻¹ d⁻¹) need to improve by a factor 10 in order to be competitive with ozonation. ICM, persistent towards oxidative techniques, were successfully dehalogenated with a novel reductive technique using Bio-Pd as a nanosized catalyst in an MBR. Iomeprol, iopromide and iohexol were removed for >97% and the more recalcitrant diatrizoate for 90%. The conditions favorable for microbial H₂-production enabling the charging of the Pd catalyst, were shown to be important for the removal of ICM. Overall, the results indicate that Mn oxide and Pd coupled to microbial catalysis offer novel potential for advanced water treatment.     

A sustainable, carbon neutral methane oxidation by a partnership of methane oxidizing communities and microalgae

Effluents of anaerobic wastewater treatment plants are saturated with methane, an effective greenhouse gas. We propose a novel approach to treat such effluents using a coculture of methane oxidizing communities and microalgae, further indicated as methalgae, which would allow microbial methane oxidation with minimal CO₂ emissions. Coculturing a methane oxidizing community with microalgae in sequence batch reactors under continuous lightning yielded a factor of about 1.6 more biomass relative to the control without microalgae. Moreover, 55% less external oxygen supply was needed to maintain the methane oxidation, as oxygen was produced in situ by the microalgae. An overall methane oxidation rate of 171 ± 27 mg CH₄ L⁻¹ liquid phase d⁻¹ was accomplished in a semi-batch setup, while the excess CO₂ production was lower than 1 mg CO₂ L⁻¹ d⁻¹. Both nitrate and ammonium were feasible nitrogen sources for the methalgae. These results show that a coculture of microalgae and methane oxidizing communities can be used to oxidize dissolved methane under O₂-limiting conditions, which could lead to a novel treatment for dissolved methane in anaerobic effluents.