Platinum and Palladium in Semiconductor Photocatalytic Systems FACTORS AFFECTING THE PURIFICATION OF WATER AND AIR

A wide range of organic pollutants can be destroyed by semiconductor photocatalysis using titania. The purification of water and air contaminated with organic pollutants has been investigated by semiconductor photocatalysis for many years and in attempts to improve the purification rate platinum and palladium have been deposited, usually as fine particles, on the titania surface. Such deposits are expected to improve the rate of reduction of oxygen and so reduce the probability of electron-hole recombination and increase the overall rate of the reaction. The effectiveness of the deposits is reviewed here and appears very variable with reported rate enhancement factors ranging from 8 to 0.1. Semiconductor photocatalysis can be used to purify air (at temperatures > 100 degrees C) and Pt deposits can markedly improve the overall rate of mineralisation. However, volatile organic compounds containing an heteroatom can deactivate the photocatalyst completely and irreversibly. Factors contributing to the success of the processes are considered. The use of chloro-Pt(IV)-titania and other chloro-platinum group metals-titania complexes as possible visible light sensitisers for water and air purification is briefly reviewed.

Variable selection via RIVAL and its application in nuclear material detection

In many situations, the number of data points is fixed, and the asymptotic convergence results of popular model selection tools may not be useful. A new algorithm for model selection, RIVAL (removing irrelevant variables amidst Lasso iterations), is presented and shown to be particularly effective for a large but fixed number of data points. The algorithm is motivated by an application of nuclear material detection where all unknown parameters are to be non-negative. Thus, positive Lasso and its variants are analyzed. Then, RIVAL is proposed and is shown to have some desirable properties, namely the number of data points needed to have convergence is smaller than existing methods.

Voltage and power quality improvement strategy for a DFIG wind turbine during variable wind conditions

This paper presents a voltage and power quality enhancement scheme for a doubly-fed induction generator (DFIG) wind farm during variable wind conditions. The wind profiles were derived considering the measured data at a DFIG wind farm located in Northern Ireland (NI). The aggregated DFIG wind farm model was validated using measured data at a wind farm during variable generation. The voltage control strategy was developed considering the X/R ratio of the wind farm feeder which connects the wind farm and the grid. The performance of the proposed strategy was evaluated for different X/R ratios, and wind profiles with different characteristics. The impact of flicker propagation along the wind farm feeder and effectiveness of the proposed strategy is also evaluated with consumer loads connected to the wind farm feeder. It is shown that voltage variability and short-term flicker severity is significantly reduced following implementation of the novel strategy described.

Modelling and Control of a Variable-Speed Switched Reluctance Generator based Wind Turbine

This paper studies the system modelling and control aspects of switched reluctance generator (SRG) based variable speed wind turbines. A control system is implemented to provide proper operation of the SRG as well as power tracking capabilities for varying wind speeds. The control system for the grid side inverter that will allow the SRG to properly generate power to the system is also presented. Studies are presented of both the SRG and inverter control systems capabilities during a balanced three-phase fault. The paper will demonstrate that the SRG based wind turbine presents a feasible variable wind speed solution with good fault response capabilities.

Catalysis in Ionic Liquid-Supercritical CO2 Systems

The combination of ionic liquids (ILs) and supercritical CO2 (scCO2) allows efficient catalytic processes to be developed. Catalyst separation is generally a major challenge when enzymes or homogeneous organometallic catalysts are utilised for reactions, and IL–scCO2 systems address these separation problems, facilitating the recycling or continual use of the catalyst. Typically these systems involve a catalyst being dissolved in an IL and this is where it remains during the process, with scCO2 extracting the products from the IL (catalyst) phase. ILs and many catalysts are not soluble in scCO2 and this facilitates the clean separation of products from the catalyst and IL. When the pressure is reduced in a collection chamber, the scCO2 returns to CO2 gas and products can be obtained without contamination of catalyst or solvents. It is possible to operate IL–scCO2 systems in a continuous flow manner and this further improves the efficiency and industrial potential of these systems. This chapter will introduce the fundamental properties of these multiphase catalytic systems. It will also highlight key examples of catalytic processes from the academic literature which illustrate the benefits of utilising this combination of solvents for catalysis

EL CVn-type binaries - Discovery of 17 helium white dwarf precursors in bright eclipsing binary star systems

The star 1SWASP J024743.37-251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP 0247-25 B). The remnant is in a rarely observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low mass white dwarf composed almost entirely of helium, i.e. it is a pre-helium white dwarf (pre-He-WD). We have used the photometric database from theWide Angle Search for Planets (WASP) to find 17 eclipsing binary stars with orbital periods P = 0.7-2.2 d with similar light curves to 1SWASP J024743.37-251549.2. The only star in this group previously identified as a variable star is the brightest one, EL CVn, which we adopt as the prototype for this class of eclipsing binary star. The characteristic light curves of EL CVn-type stars show a total eclipse by an A-type dwarf star of a smaller, hotter star and a secondary eclipse of comparable depth to the primary eclipse. We have used new spectroscopic observations for six of these systems to confirm that the companions to the A-type stars in these binaries have very low masses (≈0.2M⊙). This includes the companion to EL CVn which was not previously known to be a pre-He-WD. EL CVn-type binary star systems will enable us to study the formation of very low mass white dwarfs in great detail, particularly in those cases where the pre-He-WD star shows non-radial pulsations similar to those recently discovered in WASP0247-25 B. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Improving Bandwidth Efficiency in E-band Communication Systems

The allocation of a large amount of bandwidth by regulating bodies in the 70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges for providing affordable and reliable Gigabit per second wireless point-to-point links. This article first reviews the available bandwidth and licensing regulations in the E-band. Subsequently, different propagation models, e.g., the ITU-R and Cane models, are compared against measurement results and it is concluded that to meet specific availability requirements, E-band wireless systems may need to be designed with larger fade margins compared to microwave systems. A similar comparison is carried out between measurements and models for oscillator phase noise. It is confirmed that phase noise characteristics, that are neglected by the models used for narrowband systems, need to be taken into account for the wideband systems deployed in the E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed continuous aperture phased (CAP)-MIMO, is presented. Simulations show that CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs. Finally, it is argued that full-duplex relaying can be used to greatly enhance the coverage of E-band systems without sacrificing throughput, thus, facilitating their application in establishing the backhaul of heterogeneous networks.

Proposal for a Noninterferometric Test of Collapse Models in Optomechanical Systems

The test of modifications to quantum mechanics aimed at identifying the fundamental reasons behind the unobservability of quantum mechanical superpositions at the macroscale is a crucial goal of modern quantum mechanics. Within the context of collapse models, current proposals based on interferometric techniques for their falsification are far from the experimental state of the art. Here we discuss an alternative approach to the testing of quantum collapse models that, by bypassing the need for the preparation of quantum superposition states might help us addressing nonlinear stochastic mechanisms such as the one at the basis of the continuous spontaneous localization model. 

A continuous flow packed bed photocatalytic reactor for the destruction of 2-methylisoborneol and geosmin utilising pelletised TiO2

Taste and odour compounds, especially geosmin (GSM) and 2-methylisoborneol (2-MIB), cause major problems in both drinking water and aquaculture industries world-wide. Aquaculture in particular has experienced significant financial losses due to the accumulation of taint compounds prior to harvest resulting in consumer rejection. UV-TiO2 photocatalysis has been demonstrated to remove GSM and 2-MIB at laboratory scale but the development of a continuous flow reactor suitable for use in water treatment has not been investigated. In this study, a pilot packed bed photocatalytic reactor was developed and evaluated for water treatment with both laboratory and naturally tainted samples. A significant reduction of both 2-MIB and GSM was achieved in both trials using the packed bed reactor unit. With the laboratory spiked water (100ngL-1 of each compound added prior to treatment), detectable levels were reduced by up to 97% after a single pass through the unit. When the reactor was used to treat water in a fish farm where both compounds were being produced in situ (2-MIB: 19ngL-1 and GSM: 14ngL-1) a reduction of almost 90% in taint compounds was achieved. These very encouraging promising results demonstrate the potential of this UV-TiO2 photocatalytic reactor for water treatment in fish rearing systems and other applications.

The importance of gas infrastructure in power systems with high wind power penetrations

Gas fired generation currently plays an integral support role ensuring security of supply in power systems with high wind power penetrations due to its technical and economic attributes. However, the increase in variable wind power has affected the gas generation output profile and is pushing the boundaries of the design and operating envelope of gas infrastructure. This paper investigates the mutual dependence and interaction between electricity generation and gas systems through the first comprehensive joined-up, multi-vector energy system analysis for Ireland. Key findings reveal the high vulnerability of the Irish power system to outages on the Irish gas system. It has been shown that the economic operation of the power system can be severely impacted by gas infrastructure outages, resulting in an average system marginal price of up to €167/MWh from €67/MWh in the base case. It has also been shown that gas infrastructure outages pose problems for the location of power system reserve provision, with a 150% increase in provision across a power system transmission bottleneck. Wind forecast error was shown to be a significant cause for concern, resulting in large swings in gas demand requiring key gas infrastructure to operate at close to 100% capacity. These findings are thought to increase in prominence as the installation of wind capacity increases towards 2020, placing further stress on both power and gas systems to maintain security of supply.

A Continuous Time Markov Chain Based Sequential Analytical Approach for Composite Power System Reliability Assessment

This paper proposes a continuous time Markov chain (CTMC) based sequential analytical approach for composite generation and transmission systems reliability assessment. The basic idea is to construct a CTMC model for the composite system. Based on this model, sequential analyses are performed. Various kinds of reliability indices can be obtained, including expectation, variance, frequency, duration and probability distribution. In order to reduce the dimension of the state space, traditional CTMC modeling approach is modified by merging all high order contingencies into a single state, which can be calculated by Monte Carlo simulation (MCS). Then a state mergence technique is developed to integrate all normal states to further reduce the dimension of the CTMC model. Moreover, a time discretization method is presented for the CTMC model calculation. Case studies are performed on the RBTS and a modified IEEE 300-bus test system. The results indicate that sequential reliability assessment can be performed by the proposed approach. Comparing with the traditional sequential Monte Carlo simulation method, the proposed method is more efficient, especially in small scale or very reliable power systems.