Predicting chemical reaction equilibria in molten carbonate fuel cells via molecular simulations

It has been recently suggested that hydroxide ions can be formed in the electrolyte of molten carbonate fuel cells when water vapor is present. The hydroxide can replace carbonate in transporting electrons across the electrolyte, thereby reducing the CO₂ separation efficiency of the fuel cell although still producing electricity. In this work, we obtain the equilibrium concentration of hydroxide in five molten alkali carbonate salts from molecular simulations. The results reveal that there can be a substantial amount of hydroxide in the electrolyte at low partial pressures of CO₂ . In addition, we find that the equilibrium concentration of molecular water dissolved in the electrolyte is over two orders of magnitude higher than that of CO₂ . Increasing the size and polarizability (or in other words reducing the “hardness”) of the cations present in the electrolyte can reduce the hydroxide fraction, but at the cost of lowering ionic conductivity.     

QoS experiences in native IPv6 networks

Deployment of IPv6 technology in research and commercial networks has accelerated in the last few years. Inevitably, as more advanced services take advantage of the new technology, IPv6 traffic gradually increases. Today, there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks that support the Differentiated Services framework. As available software and hardware are designed to handle IPv4 packets, there is a need to accurately measure and validate performance of QoS mechanisms in an IPv6 environment. This paper discusses tests and technical challenges in the deployment of IPv6 QoS in core networks, namely the production dual stack gigabit‐speed Greek Research and Education Network (GRNET) and the IPv6‐only 6NET European test network, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common to IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class, while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state‐of‐the‐art router cards at gigabit speeds. Copyright © 2008 John Wiley & Sons, Ltd.     

Pre-vocational skills laboratory: designing interventions to improve employment skills for students with autism spectrum disorders

Universal Access in the Information Society - The use of information and communication technologies in educating children with autism spectrum disorders (ASD) is a dynamic field linking both...     

Immobilization of Lipid Substrates: Application on Phospholipase A2 Determination

The purpose of the study was to assess a fluorimetric assay for the determination of total phospholipase A₂ (PLA₂) activity in biological samples introducing the innovation of immobilized substrates on crosslinked polymeric membranes. The immobilized C₁₂‐NBD‐PtdCho, a fluorescent analogue of phosphatidylcholine, exhibited excellent stability for 3 months at 4 °C and was not desorbed in the aqueous reaction mixture during analysis. The limit of detection was 0.5 pmol FA (0.2 pg) and the linear part of the response curve extended from 1 up to 190 nmol FA/h/mL sample. The intra‐ and inter‐day relative standard deviations (%RSD), were ≤6 and ≤9 %, respectively. Statistical comparison with other fluorescent methods showed excellent correlation and agreement. Semiempirical calculations showed a fair amount of electrostatic interaction between the NBD‐labeled substrate and the crosslinked polyvinyl alcohol with the styryl pyridinium residues (PVA‐SbQ) material, from the plane of which, the sn‐2 acyl chain of the phospholipid stands out and is accessible by PLA₂. Atomic Force Microscopy revealed morphological alterations of the immobilized substrate after the reaction with PLA₂. Mass spectrometry showed that only C₁₂‐NBD‐FA, the PLA₂ hydrolysis product, was detected in the reaction mixture, indicating that PLA₂ recognizes PVA‐SbQ/C₁₂‐NBD‐PtdCho as a surface to perform catalysis.     

On the optimization of hydrogen storage in metal hydride beds

This work presents a novel systematic approach for the optimal design and control of metal hydride beds used for hydrogen storage. A detailed 2-D mathematical model is developed and validated against experimental and theoretical literature results. Based on recent advances in dynamic optimization, the objective is then to find the optimal process design (e.g. cooling systems design) and operating strategy (e.g. cooling fluid profile over time, hydrogen charging profile, etc.) so as to minimize the storing time, while satisfying, a number of operating constraints. Such constraints account for pressure drop limitations, cooling fluid availability and maximum tank temperature. Optimization results indicate that almost 60% improvement of the storage time can be achieved, over the case where the system is not optimized, for a minimum storage capacity of 99% of the total bed capacity. Trade-offs between various objectives, alternative design options and optimal cooling control policies are systematically revealed illustrating the potential offered by modern optimization techniques.     

Spatial patterns,controlling factors,and characteristics of landslides triggered by strike-slip faulting earthquakes: case study of Lefkada island,Greece

Bulletin of Engineering Geology and the Environment - The correlation of coseismic landslides with the seismic and morphological parameters has been investigated in detail by many researchers,...     

Synthesis gas production from methane and propane in a miniaturized GlidArc reformer

The current paper focuses on the miniaturization and utilization of the GlidArc^® principle for the reforming of fuel gases (such as methane and propane) to synthesis gas (H₂ + CO). The reforming characteristics and optimal operating conditions to achieve maximum synthesis gas yield were determined. Parametric screening studies were performed with different (i) atomic ratios of oxygen to carbon (O/C) in the range from 1 to 2, (ii) and feed flow rates from 2 to 10 L/min using alternating current voltage to produce the plasma in the reactor, which was varied from 2.8 to 4.6 kV. A Higher synthesis gas ratio of H₂/CO ≈ 2.35 was achieved when methane was processed at O/C = 1 in comparison with propane (H₂/CO ≈ 1.52).     

A high pressure single-pass high-conversion electrochemical cell for intensification of organic electrosynthesis processes

The anode oxidation of 4-methoxytoluene (4-MT) to 4-methoxybenzyl dimethylacetal (4-MBDMA) in methanol is used as a test reaction for the study of a microchannel electrochemical reactor operated continuously in a single-pass high-conversion mode. The cell consists of two stainless steel cathodes, grooved with 100 μm deep channels surrounding a flat glassy carbon anode. Pressures up to 20 bars are applied in the cell in order to reduce the volumetric flow rate of the cathodically produced hydrogen. Both the narrow gap and the operation under pressure lead to an enhancement of the electrolytic conductivity of the cell and make it possible to operate with concentrated solutions, with high current densities and with a very low supporting electrolyte concentration (i.e. 0.01 M KF).The cell performance is discussed in terms of cell voltage, reactant conversion, material and current efficiency and finally selectivity in 4-MBDMA. The effect of inlet reagent concentration, pressure, flow-rate and temperature are investigated. Best performance is obtained with 0.5 M 4-MT at 5 bars and 45 °C: for a 90% conversion, selectivity and current efficiency attain, respectively, 92% and 85%. The high pressure, single-pass high-conversion cell exhibits in this case a space time yield 5–10 times higher than the current industrial process, with a significantly lower concentration of the supporting electrolyte.