Platinum Group Metals and Their Oxides in Semiconductor Photosensitisation BASIC PRINCIPLES, METAL PHOTODEPOSITION AND WATER PHOTOSPLITTING REACTIONS

The basic principles of semiconductor photochemistry, particularly using titania as a semiconductor photocatalyst, are discussed. When a platinum group metal or its oxide is deposited onto the surface of a sensitised semiconductor the overall efficiency of the reactions it takes part in are often improved, especially when the deposits are used as hydrogen and oxygen catalysts, respectively. Methods of depositing metal or metal oxide are examined, and a particular focus is given to a photodeposition process that uses a sacrificial electron donor. Platinum group metal and platinum group metal oxide coated semiconductor photocatalysts are prominent in heterogeneous systems that are capable of the photoreduction, oxidation and cleavage of water. There is a recent renaissance in work on water-splitting semiconductor-sensitised photosystems, but there are continued concerns over their irreproducibility, longevity and photosynthetic nature.

Thermodynamic Properties of Mixtures Containing Ionic Liquids. 4. LLE of Binary Mixtures of [C2MIM][NTf2] with Propan-1-ol, Butan-1-ol, and Pentan-1-ol and [C4MIM][NTf2] with Cyclohexanol and 1,2-Hexanediol Including Studies of the Influence of Small Amounts of Water

Experimental data are presented for liquid-liquid equilibria of mixtures of the room-temperature ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C2MIM][NTf2]) with the three alcohols propan-1-ol, butan-1-ol, and pentan-1-ol and for the 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) imide ([C4MIM][NTf2]) with cyclohexanol and 1,2-hexanediol in the temperature range of 275 K to 345 K at ambient pressure. The synthetic method has been used. Cloud points at a given composition were observed by varying the temperature and using light scattering to detect the phase splitting. In addition, the influence of small amounts of water on the demixing temperatures of binary mixtures of [C2MIM][NTf2] and propan-1-ol, butan-1-ol, and pentan-1-ol was investigated.

Generation of a train of ultrashort pulses from a compact birefringent crystal array

A linear array of n calcite crystals is shown to allow the generation of a high contrast (> 10: 1) train of 2(n) high energy (> 100 mu J) pulses from a single ultrafast laser pulse. Advantage is taken of the pulse-splitting properties of a single birefringent crystal, where an incident laser pulse can be split into two pulses with orthogonal polarizations and equal intensity, separated temporally in proportion to the thickness of the crystal traversed and the difference in refractive indices of the two optic axes. In the work presented here an array of seven calcite crystals of sequentially doubled thickness is used to produce a train of 128 pulses, each of femtosecond duration. Readily versatile properties such as the number of pulses in the train and variable mark-space ratio are realized from such a setup. (c) 2007 Optical Society of America

Use of recycled demolition aggregate in precast products, phase II: Concrete paving blocks

A study undertaken at the University of Liverpool has investigated the potential for using construction and demolition waste (C&DW) as aggregate in the manufacture of a range of precast concrete products, i.e. building and paving blocks and pavement flags. Phase II, which is reported here, investigated concrete paving blocks. Recycled demolition aggregate can be used to replace newly quarried limestone aggregate, usually used in coarse (6 mm) and fine (4 mm-to-dust) gradings. The first objective, as was the case with concrete building blocks, was to replicate the process used by industry in fabricating concrete paving blocks in the laboratory. The compaction technique used involved vibration and pressure at the same time, i.e. a vibro-compaction technique. An electric hammer used previously for building blocks was not sufficient for adequate compaction of paving blocks. Adequate compaction could only be achieved by using the electric hammer while the specimens were on a vibrating table. The experimental work involved two main series of tests, i.e. paving blocks made with concrete- and masonry-derived aggregate. Variables that were investigated were level of replacement of (a) coarse aggregate only, (b) fine aggregate only, and (c) both coarse and fine aggregate. Investigation of mechanical properties, i.e. compressive and tensile splitting strength, of paving blocks made with recycled demolition aggregate determined levels of replacement which produced similar mechanical properties to paving blocks made with newly quarried aggregates. This had to be achieved without an increase in the cement content. The results from this research programme indicate that recycled demolition aggregate can be used for this new higher value market and therefore may encourage demolition contractors to develop crushing and screening facilities for this. (C) 2011 Published by Elsevier Ltd.

Spin-orbit effects on photoionization-produced alignment of the Ar+ 3p(4)(P-3)4p levels

We have determined photoionization spectra of Ar with excitation of the 3p(4)(P-3)4p states emphasizing the effects of two different classes of Ar+ spin-orbit interactions. The spin-orbit splitting of each Ar+ state adequately describes the resonant excitation of the quartet states of Ar+, and gives Ar photoionization cross sections with excitation of the 3p4(3P)4p P-2(3/2)o and P-4(5/2)o levels of Ar+ in sufficiently good agreement with experiment to identify the observed resonances and to estimate the excitation strengths. In addition, we demonstrate the importance of spin-orbit induced mixing of different Ar+ LS-coupled states for observables such as the alignment of the 3p(4)(P-3)4p P-4(5/2)o level and the excitation of Rydberg series converging to the 3p(4)(P-3)4p S-2(o) and S-4(o) thresholds.

The use of recycled demolition aggregate in precast concrete products – Phase III: Concrete pavement flags

A study undertaken at the University of Liverpool has investigated the potential for using construction and demolition waste (C&DW) derived aggregate in the manufacture of a range of precast concrete products, i.e. building and paving blocks and pavement flags. Phase III, which is reported here, investigated
concrete pavement flags. This was subsequent to studies on building and paving blocks. Recycled demolition aggregate can be used to replace newly quarried limestone aggregate, usually used in coarse (6 mm) and fine (4 mm-to-dust) gradings. The first objective was, as was the case with concrete building
and paving blocks, to replicate the process used by industry in fabricating concrete pavement flags in the laboratory. The ‘‘wet’’ casting technique used by industry for making concrete flags requires a very workable mix so that the concrete flows into the mould before it is compressed. Compression squeezes out water from the top as well as the bottom of the mould. This industrial casting procedure was successfully replicated in the laboratory by using an appropriately modified cube crushing machine and a special mould typical of what is used by industry. The mould could be filled outside of the cube crushing machine and then rolled onto a steel frame and into the machine for it to be compressed. The texture and mechanical properties of the laboratory concrete flags were found to be similar to the factory ones. The experimental work involved two main series of tests, i.e. concrete flags made with concrete- and
masonry-derived aggregate. Investigation of flexural strength was required for concrete paving flags. This is different from building blocks and paving blocks which required compressive and tensile splitting strength respectively. Upper levels of replacement with recycled demolition aggregate were determined
that produced similar flexural strength to paving flags made with newly quarried aggregates, without requiring an increase in the cement content. With up to 60% of the coarse or 40% of the fine fractions replaced with concrete-derived aggregates, the target mean flexural strength of 5.0 N/mm2 was still
achieved at the age of 28 days. There was similar detrimental effect by incorporating the fine masonry-derived aggregate. A replacement level of 70% for coarse was found to be satisfactory and also conservative. However, the fine fraction replacement could only be up to 30% and even reduced to 15% when used for mixes where 60% of the coarse fraction was also masonry-derived aggregate.

The electronic band structure of indium selenide:Photoemission and theory

The electronic band structure of vacuum cleaved single-crystal indium selenide has been investigated by X-ray and ultraviolet photoelectron spectroscopy. The valence band consists of three well separated groups, one derived from the Se 4s levels, and two derived from p-like wavefunctions. The band structure and valence band density of states has been calculated using a tight-binding single-layer approximation and all the major features in the experimental spectra are well accounted for. The spin-orbit splitting and electron loss structure associated with the In 4d core level is also reported.

Stiffener debonding mechanisms in post-buckled CFRP aerospace panels

This paper describes the fractographic analysis of five CFRP post-buckled skin/stringer panels that were tested to failure in compression. The detailed damage mechanisms for skin/stiffener detachment in an undamaged panel were characterised and related to the stress conditions during post-buckling; in particular the sites of peak twist (at buckling nodes) and peak bending moments (at buckling anti-nodes). The initial event was intralaminar splitting of the +45 degrees plies adjacent to the skin/stiffener interface, induced by high twist at a nodeline. This was followed by mode II delamination, parallel to +/- 45 degrees plies and then lengthwise (0 degrees) shear along the stiffener centreline. The presence of defects or damage was found to influence this failure process, leading to a reduction in strength. This research provides an insight into the processes that control post-buckled performance of stiffened panels and suggests that 2D models and element tests do not capture the true physics of skin/stiffener detachment: a full 3D approach is required.

Illumination invariant facial recognition using a piecewise-constant lighting model

In this paper we demonstrate a simple and novel illumination model that can be used for illumination invariant facial recognition. This model requires no prior knowledge of the illumination conditions and can be used when there is only a single training image per-person. The proposed illumination model separates the effects of illumination over a small area of the face into two components; an additive component modelling the mean illumination and a multiplicative component, modelling the variance within the facial area. Illumination invariant facial recognition is performed in a piecewise manner, by splitting the face image into blocks, then normalizing the illumination within each block based on the new lighting model. The assumptions underlying this novel lighting model have been verified on the YaleB face database. We show that magnitude 2D Fourier features can be used as robust facial descriptors within the new lighting model. Using only a single training image per-person, our new method achieves high (in most cases 100%) identification accuracy on the YaleB, extended YaleB and CMU-PIE face databases.

Characterization of Inter-Body Interference in Context Aware Body Area Networking (CABAN)

The characterization and understanding of body to body communication channels is a pivotal step in the development of emerging wireless applications such as ad-hoc personnel localisation and context aware body area networks (CABAN). The latter is a recent innovation where the inherent mobility of body area networks can be used to improve the coexistence of multiple co-located BAN users. Rather than simply accepting reductions in communication performance, sensed changes in inter-network co-channel interference levels may facilitate intelligent inter-networking; for example merging or splitting with other BANs that remain in the same domain. This paper investigates the inter-body interference using controlled measurements of the full mesh interconnectivity between two ambulatory BANs operating in the same environment at 2.45 GHz. Each of the twelve network nodes reported received signal strength to allow for the creation of carrier to interference ratio time series with an overall entire mesh sampling period of 54 ms. The results indicate that even with two mobile networks, it is possible to identify the onset of co-channel interference as the BAN users move towards each other and, similarly, the transition to more favourable physical layer channel conditions as they move apart. © 2011 IEEE.

IO Performance Prediction in Consolidated Virtualized Environments

We propose a trace-driven approach to predict the performance degradation of disk request response times due to storage device contention in consolidated virtualized environments. Our performance model evaluates a queueing network with fair share scheduling using trace-driven simulation. The model parameters can be deduced from measurements obtained inside Virtual Machines (VMs) from a system where a single VM accesses a remote storage server. The parameterized model can then be used to predict the effect of storage contention when multiple VMs are consolidated on the same virtualized server. The model parameter estimation relies on a search technique that tries to estimate the splitting and merging of blocks at the the Virtual Machine Monitor (VMM) level in the case of multiple competing VMs. Simulation experiments based on traces of the Postmark and FFSB disk benchmarks show that our model is able to accurately predict the impact of workload consolidation on VM disk IO response times.

Integrated Low-Loss Passive SiGe Power Splitter and Combiner Operating Across 78-86 GHz Band

This paper describes the design, implementation, and characterization of a new type of passive power splitting and combining structure for use in a differential four-way power-combining amplifier operating at E-band. In order to achieve lowest insertion loss, input and output coils inductances are resonated with shunt capacitances. Simple C-L-C and L-C networks are proposed in order to compensate inductive loading due to routing line that would otherwise introduce mismatch and increase loss. Across 78-86 GHz band, measured insertion loss is about 7 dB. Measured return losses are >10 dB from 73 GHz to 94 GHz at the input port and >9 dB from 60 GHz to 94 GHz at the output port. When integrated with driver and power amplifier cells, the simulated complete circuit exhibits 18.2 dB gain and 20.3 dBm saturated output power.

Context-Aware Body Area Networks (CABAN) for interactive smart environments:Interference characterization

Body Area Networks are unique in that the large-scale mobility of users allows the network itself to travel across a diverse range of operating domains or even to enter new and unknown environments. This network mobility is unlike node mobility in that sensed changes in inter-network interference level may be used to identify opportunities for intelligent inter-networking, for example, by merging or splitting from other networks, thus providing an extra degree of freedom. This paper introduces the concept of context-aware bodynets for interactive environments using inter-network interference sensing. New ideas are explored at both the physical and link layers with an investigation based on a 'smart' office environment. A series of carefully controlled measurements of the mesh interconnectivity both within and between an ambulatory body area network and a stationary desk-based network were performed using 2.45 GHz nodes. Received signal strength and carrier to interference ratio time series for selected node to node links are presented. The results provide an insight into the potential interference between the mobile and static networks and highlight the possibility for automatic identification of network merging and splitting opportunities. © 2010 ACM.

Wave loads on the foundation of a bottom-hinged modular flap structure

Large loads result in expensive foundations which are a substantial proportion of the capital cost of flap-type Wave Energy Converters (WECs). Devices such as Oyster 800, currently deployed at the European Marine Energy Centre (EMEC), comprise a single flap for the full width of the machine. Splitting a flap-type device into smaller vertical flap modules, to make a ‘modular-flap’, might reduce the total foundation loads, whilst still providing acceptable performance in terms of energy conversion.
This paper investigates the foundation loads of an undamped modular-flap device, comparing them to those for a rigid flap of an equivalent width. Physical modelling in a wave tank is used, with loads recorded using a six degree of freedom (DoF) load cell. Both fatigue and extreme loading analysis was conducted. The rotations of the flaps were also recorded, using a motion-tracking system.

Universal tight binding model for chemical reactions in solution and at surfaces. I. Organic molecules

As is now well established, a first order expansion of the Hohenberg-Kohn total energy density functional about a trial input density, namely, the Harris-Foulkes functional, can be used to rationalize a non self consistent tight binding model. If the expansion is taken to second order then the energy and electron density matrix need to be calculated self consistently and from this functional one can derive a charge self consistent tight binding theory. In this paper we have used this to describe a polarizable ion tight binding model which has the benefit of treating charge transfer in point multipoles. This admits a ready description of ionic polarizability and crystal field splitting. It is necessary in constructing such a model to find a number of parameters that mimic their more exact counterparts in the density functional theory. We describe in detail how this is done using a combination of intuition, exact analytical fitting, and a genetic optimization algorithm. Having obtained model parameters we show that this constitutes a transferable scheme that can be applied rather universally to small and medium sized organic molecules. We have shown that the model gives a good account of static structural and dynamic vibrational properties of a library of molecules, and finally we demonstrate the model's capability by showing a real time simulation of an enolization reaction in aqueous solution. In two subsequent papers, we show that the model is a great deal more general in that it will describe solvents and solid substrates and that therefore we have created a self consistent quantum mechanical scheme that may be applied to simulations in heterogeneous catalysis.