Water as a Promoter of the Complete Oxidation of Volatile Organic Compounds over Uranium Oxide Catalysts

The effect of water addition on the complete oxidation of benzene and propane VOCs by uranium oxide catalysts has been investigated. Benzene oxidation was studied using a silica supported U₃O₈ catalyst. Complete oxidation is promoted by the addition of 2.6% water compared with the reactivity when no water is added to the reactant feed. Increasing the water concentration to 12.1% resulted in a suppression of oxidation activity. Investigation of propane oxidation using U₃O₈ shows a dramatic promotion of activity. Propane conversion was ca. 50% at 600 °C without added water, whilst it increased to 100% at 400 °C with the addition of 2.6% water. A comparison of oxidation activity has been made with Mn₂O₃, an oxide recognised for complete oxidation. In contrast to the U₃O₈ catalysts the addition of 2.6% water suppresses the activity of Mn₂O₃. In situ powder X-ray diffraction studies showed that the bulk U₃O₈ structure was stable under all the reaction conditions. The origin of the increased activity is not clear but may be due to modification of the catalyst surface and the contribution from new reaction pathways such as steam reforming.     

Direct synthesis of hydrogen peroxide from H2 and O2 using zeolite-supported Au catalysts

The direct synthesis of hydrogen peroxide from H₂ and O₂ using zeolite-supported Au catalysts is described and their activity is contrasted with silica- and alumina-supported Au catalysts. Two zeolites were investigated, ZSM-5 and zeolite Y. The effect of calcination of these catalysts is studied and it is found that for uncalcined catalysts high rates of hydrogen peroxide formation are observed, but these catalysts are unstable and lose Au during use. Consequently, reuse of these catalysts leads to lower rates of hydrogen peroxide formation. However, catalysts calcined at 400 °C are more stable and can be reused without loss of gold. The use of zeolites as a support for Au gives comparable rates of hydrogen peroxide formation to alumina-supported Au catalysts and higher rates when compared with silica-supported catalysts. prepared using a similar method. Zeolite Y-supported catalysts are more active than ZSM-5-supported catalysts for the stable calcined materials. It is considered that the overall activity of these supported catalysts may be related to the aluminium content as the activity increases with increasing aluminium content.     

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass,part II: Structure

High-alumina containing high-level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition-structure-property (C-S-P) relationships compared to previously studied HLW glasses. These C-S-P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and ²⁷Al, ²³Na, ²⁹Si, and ¹¹B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD simulations were used to generate atomistic structural models of the borosilicate glasses and simulation results were validated by the experimental structural data. Short-range (eg, bond distance, coordination number, etc) and medium-range (eg, oxygen speciation, network connectivity, polyhedral linkages) structural features of the borosilicate glasses were systematically investigated as a function of the degree of substitution. The results show that bond distance and coordination number of the cation-oxygen pairs are relatively insensitive to Al:Si and (Al + Na):Si substitutions with the exception of the B-O pair. Additionally, the Al:Si substitution results in an increase in tri-bridging oxygen species, whereas (Al + Na):Si substitution creates nonbridging oxygen species. Charge compensator preferences were found for Si-[NBO] (Na⁺), ^[3]B-[NBO] (Na⁺), ^[4]B (mostly Ca²⁺), ^[4]Al (nearly equally split Na⁺ and Ca²⁺), and ^[6]Zr (mostly Ca²⁺). The network former-BO-network former linkages preferences were also tabulated; Si-O-Al and Al-O-Al were preferred at the expense of lower Si-O-^[3]B and ^[3]B-O-^[3]B linkages. These results provide insights on the structural origins of property changes such as glass-transition temperature caused by the substitutions, providing a basis for future improvements of theoretical and computer simulation models.     

Impact damage detection in carbon fibre composites using HTS SQUIDs and neural networks

A neural network-based data analysis tool, developed to speed the damage detection process for the NDE of impact damaged carbon fibre composites, is discussed. A feature extraction method utilising a gradient threshold search function and a feed forward neural network for pattern recognition were used to develop the system. Impact damaged carbon composite sample plates were scanned with an eddy current-based NDE setup using HTS SQUID gradiometers and double-D excitation coils. Detection of damage sites in data affected by noise spikes caused by environmental disturbances is demonstrated. Finally, a possible design for a future entirely automated scanning system is also introduced.     

The influence of grain-boundary segregation of Y in Cr2O3 on the oxidation of Cr metal

The oxidation behavior at 900°C of pure Cr and Cr implanted with 2×10¹⁶ Y ions/cm² was studied. The kinetics of oxidation were measured thermogravimetrically and manometrically. The mechanisms of oxide growth were studied using¹⁸O-tracer oxidation experiments, and the composition and microstructure of the oxide scales were characterized by TEM and STEM. Segregation of Y cations at Cr₂O₃ grain boundaries was found to be the critical factor governing changes in the oxidation behavior of Cr upon the addition of Y. In the absence of Y, pure Cr oxidized by the outward diffusion of cations via grain boundaries in the Cr₂O₃ scale. When Y was present at high concentration in the scale, as when Cr implanted with 2×10¹⁰ Y ions/cm² was oxidized, anion diffusion predominated. It is concluded that strain-induced segregation of Y at grain boundaries in the oxide reduced the cation flux along the grain boundaries. The rate of oxidation was reduced because the grain-boundary diffusivity of cations became lower than the grain-boundary diffusivity of the anions, which then controlled the rate of oxidation. Changes in the relative rates of Cr³⁺ and O^2– transport, as well as a solute-drag effect exerted by Y on the oxide grain boundaries, resulted in changes in the microstructure of the oxide.     

Innovative potential of 3D software applications in fashion and textile design

Advanced cloth simulation plug-in tools are increasingly being used by designers in movies, television, advertising and computer games, to take the strain out of creating and simulating realistic cloth effects for dressing virtual characters. This paper describes experiments into designing textiles and clothing using 3D graphics software and a digital cloth dynamics plug-in, which are an integral part of PhD research in progress. The methods used in testing the 3D software and the cloth dynamics plug-in illustrate the experiences of a designer/learner. The results identify designer/learner needs and expectations for the further educational development of the research and use of cloth simulation tools in textiles/fashion design in the near future.     

Segmentation and recognition of phonetic features in handwritten Pitman shorthand

There is a wish to be able to enter text into mobile computing devices at the speed of speech. Only handwritten shorthand schemes can achieve this data recording rate. A new, overall solution to the segmentation and recognition of phonetic features in Pitman shorthand is proposed in this paper. Approaches to the recognition of consonant outlines, vowel and diphthong symbols and shortforms, which are different components of Pitman shorthand, are presented. A new rule is introduced to solve the issue of smooth junctions in the consonant outlines which was normally the bottleneck for recognition. Experiments with a set of 1127 consonant outlines, 2039 vowels and diphthongs and 841 shortforms from three shorthand writers have demonstrated that the proposed solution is quite promising. The recognition accuracies for consonant outlines, vowels and diphthongs, and shortforms achieved 75.33%, 96.86% and 91.86%, respectively. From the evaluation of 461 outlines with smooth junction, the introduction of the new rule has a great positive effect on the performance of the solution. The recognition accuracy of smooth junction improves from 37.53% to 93.41% given a writing time increase of 14.42%.