Interaction of mineral matter of coal with oxygen carriers in chemical-looping combustion (CLC)

The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are novel solutions for efficient combustion with direct separation of carbon dioxide. These processes use a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor, where the fuel reacts with the solid oxygen carrier. When utilizing coal in CLC, the oxygen carrier particles could be affected through interaction with the ash-forming mineral matter found in coal, causing deactivation and/or agglomeration. In this work, possible interactions between minerals commonly encountered in coal and several promising oxygen carriers that are currently under investigation for their use in CLC are studied by both experiment and thermodynamic equilibrium calculations. Possible interaction was studied for both highly reducing and oxidizing conditions at 900 °C. Under highly reducing conditions pyrite was found to have by far the most deteriorating effect on the oxygen carrier particles, as the sulfur in the pyrite reacted with the oxygen carrier to form sulfides. Quartz and clay minerals were found to have a rather low influence on the oxygen carriers. Out of the oxygen carriers investigated, CuO/MgAl₂O₄ and the Mn₃O₄/ZrO₂ oxygen carriers tended to be quite reactive towards mineral matter whereas ilmenite has been shown to be the most robust oxygen carrier. Although sulfur can clearly deactivate Ni, Cu and Mn based oxygen carriers under sub-stoichiometric conditions, when the fuel is converted fully to CO₂ and H₂O, sulfides are only expected for Ni-based oxygen carriers.     

Solar light photocatalytic hydrogen production from water over Pt and Au/TiO2(anatase/rutile) photocatalysts: Influence of noble metal and porogen promotion

Hydrogen production from water under artificial solar light irradiation was performed over a series of Pt and Au/TiO₂(anatase/rutile) photocatalysts. Different TiO₂ supports with varying anatase/rutile contents were compared, based on either sol–gel synthesis or commercial TiO₂. The influence of template promotion on sol–gel TiO₂ synthesis has been studied using different porogens or templates. Among various factors influencing the hydrogen evolution efficiency, it was pointed out that the following parameters were crucial to enhance H₂ evolution: (i) the nature and content of the metallic co-catalyst, (ii) the surface, crystallographic, and porosity properties of the TiO₂ anatase/rutile support, (iii) the anatase/rutile ratio, (iv) the metal–support interactions, and (v) the relative amount of methanol added as a sacrificial reagent. The influence of these different factors was studied in detail. In optimized conditions, important H₂ production efficiency (120 μmol/min) was obtained over days without deactivation and with very low amounts of methanol.     

Detection of anthropogenic gadolinium in treated wastewater in South East Queensland, Australia

The use of refractory gadolinium (Gd) complexes as paramagnetic contrast agents in magnetic resonance imaging has resulted in point source release of anthropogenic Gd (GdAnth) into the environment, and presents opportunities to trace the fate of wastewater in natural environments. We demonstrate an inductively coupled plasma mass spectrometry (ICP-MS) technique that is capable of detecting GdAnth at concentrations as low as 48 fM, approximately six orders of magnitude lower than most other micropollutants, without the need for preconcentration. Further, we establish the ubiquitous presence of GdAnth in wastewater at eight separate wastewater treatment plants in Brisbane, Australia, over a 3-month time period. In contrast, there is no evidence of GdAnth in tap water, or in four separate regional water supply dams in South East Queensland, Australia. It is, therefore, highly unlikely that other anthropogenic micropollutants sourced from urban wastewater would be present in the drinking water supply.     

Development of a model for assessing methane formation in rising main sewers

Significant methane formation in sewers has been reported recently, which may contribute significantly to the overall greenhouse gas emission from wastewater systems. The understanding of the biological conversions occurring in sewers, particularly the competition between methanogenic and sulfate-reducing populations for electron donors, is an essential step for minimising methane emissions from sewers. This work proposes an extension to the current state-of-the-art models characterising biological and physicochemical processes in sewers. This extended model includes the competitive interactions of sulfate-reducing bacteria and methanogenic archaea in sewers for various substrates available. The most relevant parameters of the model were calibrated with lab-scale experimental data. The calibrated model described field data reasonably well. The model was then used to investigate the effect of several key sewer design and operational parameters on methane formation. The simulation results showed that methane production was highly correlated with the hydraulic residence time (HRT) and pipe area to volume (A/V) ratio showing higher methane concentrations at a long HRT or a larger A/V ratio.     

ESD robust high-voltage active clamps

Using circuit simulation extended by a proper failure criterion, the HBM and TLP robustness of high-voltage clamps can be accurately predicted without the need for test silicon. Electrical measurements, physical damage analysis, and device simulation have proved that the drain junction breakdown voltage constitutes the proper failure criterion for our HV active clamps.     

Systematic approach to the synthesis of continuous-time cascaded sigma–delta modulators

This paper deals with a systematic approach to the synthesis of continuous-time cascaded sigma–delta modulators. Based on a system-theoretical model, a detailed derivation of the digital cancelation filters for continuous-time cascaded architectures is presented in order to achieve maximum signal-to-noise ratio together with optimal anti-aliasing performance. By using the same model, an exact equation for the performance loss of any cascaded architecture is derived. The latter is due to the scaling for stability and given relative to an ideal high-pass filter of the overall modulator order. Finally, an analytical calculation of optimal scaling coefficients in between the stages is performed, resulting in a limited search-space for these coefficients. Theoretical results are verified by simulations.     

Experimental investigation of R-ratio effects on fatigue crack growth of adhesively-bonded pultruded GFRP DCB joints under CA loading

A series of fatigue experiments was performed in order to investigate the effect of the R-ratio on the fatigue/fracture behavior of adhesively-bonded pultruded GFRP double cantilever beam joints. Constant amplitude fatigue experiments were carried out under displacement control with a frequency of 5 Hz in ambient laboratory conditions. Three different R-ratios were applied: R = 0.1, R = 0.5 and R = 0.8. The crack length was determined by means of crack gages and a dynamic compliance method. The dominant failure mode was a fiber-tear failure that occurred in the mat layers of the pultruded laminates. The depth of the crack location significantly affected the energy dissipated for the fracture under cyclic loading. Short-fiber and roving bridging increased the fracture resistance during crack propagation. Fatigue crack growth curves were derived for each R-ratio and each observed crack path location. The fatigue threshold and slope of the fatigue crack growth curve significantly increased with increased R-ratio.     

Improved mechanical oil spill recovery using an optimized geometry for the skimmer surface

The primary objective of this research was to improve the efficiency of mechanical oil spill response equipment by optimizing the geometry of the oleophilic skimmer recovery surface. Another objective of this work was to study the relation between the operational variables and the oil spill recovery efficiency in a full-scale oil spill recovery test, comparing novel and conventional oleophilic drum skimmer configurations. The study showed that using the new surface pattern in the recovery unit can increase the skimmer oil recovery efficiency up to three times. The improved surface pattern was found to be efficient on oils with a wide range of viscosities, including diesel oil, which is a challenging liquid to recover due to its low viscosity. The effect of the surface pattern dimensions on the recovery efficiency was explored. Guidelines for the design of a more efficient surface geometry tailored to the properties of the recovered oil were developed.     

Digestion of delta-endotoxin by gut proteases may explain reduced sensitivity of advanced instar larvae of Spodoptera littoralis to CryIC

The present study describes the correlation between gut protease activity of lepidopteran larvae of different instars, the inactivation of Bacillus thuringiensis delta-endotoxins in crystalline and noncrystalline forms, and the reduced susceptibility of advanced larval instars of Spodoptera littoralis to the toxin. The original assembly of delta-endotoxins in a crystal structure is essential for causing efficient larval mortality. Denaturation and renaturation (D/R) of delta-endotoxin crystals increased the vulnerability of the toxin molecules to proteolysis, reduced their capability to kill neonate larvae of S. littoralis, but sustained most of their larval growth-inhibition activity. E. coli-produced CryIC delta-endotoxin applied as a fraction of inclusion bodies exerted a growth inhibition effect, similar to the molecules released from the crystals by denaturation and subsequent renaturation. Incubation of CryIC with gut juice of 1st or 2nd instar larvae, left part of the CryIC toxin intact, while the toxin was completely degraded when incubated with gut juice of 5th instar larvae. The degradation rate was consistent with the increase of protease specific activity of the gut juice during larval development. This increase in toxin degradation may account for the loss of sensitivity of 5th instar larvae to CryIC. Specific protease inhibitors such as PMSF and Leupeptin were shown to inhibit gut proteases activity in all instar larvae, while, 1,10 phenanthroline, TLCK and TPCK were effective only in young instar larvae. The differential effect of protease inhibitors on proteases obtained from different larval instars indicated that gut juice protease profiles change with larval age. The observed quantitative and qualitative differences in degradation of delta-endotoxin by larval gut proteases that occur during larval maturation may account for the difference in susceptibility to the delta-endotoxin. This finding should be taken into consideration when designing strategies for the development of transgenic crops expressing delta-endotoxins as potent insecticidal proteins.     

Superluminal interactions in near-field optics

The fact that photons emitted from an electric-dipole active atom cannot be spatially localized better than to the near-field zone of the atom is seen as the origin of genuine superluminality. By means of a simple model dipole current density the general theory is used to demonstrate numerically how superluminality enters the near-field dynamics, and how from a measurement one could be tempted to believe that superluminal propagation effects occur. Furthermore, it is shown how for source-detector distances larger than a pulse length one should be able to divide the pulse into two separate parts: one purely superluminal part arising solely in the non-local generation process of the field, and another part seemingly propagating with superluminal speed. We comment on different velocity analyses, and we argue that the only fundamental velocity entering the problem is the vacuum velocity of light, which in a measurement would appear as the velocity of the trailing edge of the pulse.