Neural network controlled three-phase four-wire shunt active powerfilter

A three-phase four-wire shunt active power filter for harmonic mitigation and reactive power compensation in power systems supplying nonlinear loads is presented. Three adaptive linear neurons are used to tackle the desired three-phase filter current templates. Another feedforward three-layer neural network is adopted to control the output filter compensating currents online. This is accomplished by producing the appropriate switching patterns of the converter's legs IGBTs. Adequate tracking of the filter current references is obtained by this method. The active filter injects the current required to compensate for the harmonic and reactive components of the line currents, Simulation results of the proposed active filter indicate a remarkable improvement in the source current waveforms. This is reflected in the enhancement of the unified power quality index defined. Also, the filter has exhibited quite a high dynamic response for step variations in the load current, assuring its potential for real-time applications

Phase and space resolved optical emission spectroscopic investigations of an inductively coupled RF plasma using an imaging acousto-optic spectrometer

A novel acousto-optic spectrometer (IfU Diagnostic Systems GmbH) for 2-dimensional (2D) optical emission spectroscopy with high spectral resolution has been developed. The spectrometer is based on acousto-optic tuneable filter technology with fast random wavelength access. Measurements for characterisation of the imaging quality, the spatial resolution, and the spectral resolution are presented. The applicability for 2D-space and phase resolved optical emission spectroscopy (2D-PROES) is shown. 2D-PROES has been applied to an inductively coupled plasma with radio frequency excitation at 13.56 MHz.

A computational model for the cooling phase of injection moulding

This paper discusses the approaches and techniques used to build a realistic numerical model to analyse the cooling phase of the injection moulding process. The procedures employed to select an appropriate mesh and the boundary and initial conditions for the problem are discussed and justified. The final model is validated using direct comparisons with experimental results generated in an earlier study. The model is shown to be a useful tool for further studies aimed at optimising the cooling phase of the injection moulding process. Using the numerical model provides additional information relating to changes in conditions throughout the process, which otherwise could not be deduced or assessed experimentally. These results, and other benefits related to the use of the model, are also discussed in the paper. © 2007 Elsevier B.V. All rights reserved.

Dramatic liquid-phase dehydrogenation rate enhancements using gas-phase hydrogen acceptors

The dehydrogenation of 1,2,3,4-tetrahydrocarbazole (THCZ) to form carbazole (CZ) over supported palladium catalysts was examined in the presence of hydrogen acceptors. As expected, liquid hydrogen acceptors increased the rate of reaction but, importantly, gaseous hydrogen acceptors also have been used. Ethene, propene, and but-1-ene showed up to a fivefold increase in the rate of dehydrogenation. Moreover, compared with the analogous liquid systems, the gaseous alternatives are a potentially more economic method of enhancing the activity and provide a simpler workup. The mechanism for the increase in rate was examined by density functional theory calculations, which showed that the propene hydrogenation competes effectively with the back-hydrogenation of the intermediates formed during the THCZ dehydrogenation, resulting in a shift in the equilibrium toward to the formation of CZ. (C) 2007 Elsevier Inc. All rights reserved.

Supported and liquid phase task specific ionic liquids for base catalysed Knoevenagel reactions

A series of Hunig's base tethered ammonium ionic liquids have been used to catalyse the Knoevenagel condensation of aldehydes/ketones with malononitrile and ethyl cyanoacetate. The reactions were performed under homogeneous and under biphasic, liquid-liquid and liquid-silica supported ionic liquid, conditions with the biphasic systems employing cyclohexene as the second phase. By increasing the distance between the ammonium head group and Hunig's base the activity of the catalyst was found to increase. Higher activity, in general, was found under homogeneous reaction conditions; however, the recyclability of the catalyst was improved by supporting the BIL under biphasic conditions. (c) 2007 Elsevier B.V. All rights reserved.

Gas-phase photocatalytic oxidation of dichlorobutenes

Gas-phase photocatalysis of 1,4-dichlorobut-2-enes and 3,4-dichlorobut-1-ene (DCB) has been studied using TiO2 and 3%WO3/TiO2 supported on SiO2. DCB was found to oxidize efficiently over these catalysts; however, only low rates of CO2 formation were observed. With these chlorinated hydrocarbons, the catalysts were found to deactivate over time, probably via the formation of aldol condensation products of chloroacetaldehyde, which is the predominant intermediate observed. The variation in rate and selectivity of the oxidation reactions with O-2 concentration is reported and a mechanism is proposed. Using isotope ratio mass spectrometry, the initial step for the DCB removal has been shown not to be a carbon bond cleavage but is likely to be hydroxyl radical addition to the carbon-carbon double bond.

The effect of the addition of sodium compounds in the liquid-phase hydrodechlorination of chlorobenzene over palladium catalysts

The hydrodechlorination of chlorobenzene over supported palladium catalysts has been studied. The palladium catalysts: deactivate as the reaction proceeds due to the HCl formed as by-product. The effect of the addition of sodium compounds has been analysed for the neutralisation of HCl. When NaOH was added to the reaction mixture, no beneficial effect was observed due to the detrimental effect of the alkaline medium on the textural and metallic properties of the catalysts. Doping the support with NaOH prior to impregnation with the metal precursor leads (after calcination and reduction) to catalysts with better activity and tolerance to deactivation, especially those obtained when using PdCl2 as the metal precursor. Low metal dispersion and the capture of chloride by forming NaCl are the: main factors contributing to the: improved catalytic properties. Finally, doping the catalysts with NaOH or NaNO3, after reduction of the metal precursor leads to a moderate increase in initial activity and final conversion, although NaOH impregnation also gave rise to support corrosion and metal dispersion modification. (C) 2001 Elsevier Science B.V, All rights reserved.

The influence of the relative phase between the driving voltages on electron heating in asymmetric dual frequency capacitive discharges

The influence of the relative phase between the driving voltages on electron heating in asymmetric phase-locked dual frequency capacitively coupled radio frequency plasmas operated at 2 and 14 MHz is investigated. The basis of the analysis is a nonlinear global model with the option to implement a relative phase between the two driving voltages. In recent publications it has been reported that nonlinear electron resonance heating can drastically enhance the power dissipation to electrons at moments of sheath collapse due to the self-excitation of nonlinear plasma series resonance (PSR) oscillations of the radio frequency current. This work shows that depending on the relative phase of the driving voltages, the total number and exact moments of sheath collapse can be influenced. In the case of two consecutive sheath collapses a substantial increase in dissipated power compared with the known increase due to a single PSR excitation event per period is observed. Phase resolved optical emission spectroscopy (PROES) provides access to the excitation dynamics in front of the driven electrode. Via PROES the propagation of beam-like energetic electrons immediately after the sheath collapse is observed. In this work we demonstrate that there is a close relation between moments of sheath collapse, and thus excitation of the PSR, and beam-like electron propagation. A comparison of simulation results to experiments in a single and dual frequency discharge shows good agreement. In particular the observed influence of the relative phase on the dynamics of a dual frequency discharge is described by means of the presented model. Additionally, the analysis demonstrates that the observed gain in dissipation is not accompanied by an increase in the electrode’s dc-bias voltage which directly addresses the issue of separate control of ion flux and ion energy in dual frequency capacitively coupled radio frequency plasmas.

USE OF RETRODIRECTIVE ARRAY PHASE CONJUGATION CIRCUITRY FOR NEAR- AND FAR-FIELD POSITION ANGLE OF ARRIVAL DETECTION

In this article, we present position indication functionality as obtained by using a retrodirective array, thereby allowing location information extraction of the position of the remote transmitter with which the retrodirective array is cooperating. This is carried out using straightforward circuitry with no requirement for complex angle of arrival algorithms, thereby giving a result in real time enabling tracking of fast moving transmitters. We show using a 10 x element retrodirective array, operating at 2.4 GHz that accuracies of far-field angle of arrival of within +/- 1 degrees over the arrays +/- 30 degrees azimuth field of view are possible. While in the near-field for angles of arrival of +/- 10 degrees it is possible to extract the position of a dipole source down to a resolution of 032 lambda. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1031-1034, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25097

Attosecond phase locking of harmonics emitted from laser-produced plasmas

Laser-driven coherent extreme-ultraviolet (XUV) sources provide pulses lasting a few hundred attoseconds(1,2), enabling real-time access to dynamic changes of the electronic structure of matter(3,4), the fastest processes outside the atomic nucleus. These pulses, however, are typically rather weak. Exploiting the ultrahigh brilliance of accelerator-based XUV sources(5) and the unique time structure of their laser-based counterparts would open intriguing opportunities in ultrafast X-ray and high-field science, extending powerful nonlinear optical and pump-probe techniques towards X-ray frequencies, and paving the way towards unequalled radiation intensities. Relativistic laser-plasma interactions have been identified as a promising approach to achieve this goal(6-13). Recent experiments confirmed that relativistically driven overdense plasmas are able to convert infrared laser light into harmonic XUV radiation with unparalleled efficiency, and demonstrated the scalability of the generation technique towards hard X-rays(14-19). Here we show that the phases of the XUV harmonics emanating from the interaction processes are synchronized, and therefore enable attosecond temporal bunching. Along with the previous findings concerning energy conversion and recent advances in high-power laser technology, our experiment demonstrates the feasibility of confining unprecedented amounts of light energy to within less than one femtosecond.

Effect of a pharmacist-led multicomponent intervention focussing on the medication monitoring phase to prevent potential adverse drug events in nursing homes

OBJECTIVES: To determine the extent to which the use of a clinical informatics tool that implements prospective monitoring plans reduces the incidence of potential delirium, falls, hospitalizations potentially due to adverse drug events, and mortality.

DESIGN: Randomized cluster trial.

SETTING: Twenty-five nursing homes serviced by two long-term care pharmacies.

PARTICIPANTS: Residents living in nursing homes during 2003 (1,711 in 12 intervention; 1,491 in 13 usual care) and 2004 (1,769 in 12 intervention; 1,552 in 13 usual care).

INTERVENTION: The pharmacy automatically generated Geriatric Risk Assessment MedGuide (GRAM) reports and automated monitoring plans for falls and delirium within 24 hours of admission or as part of the normal time frame of federally mandated drug regimen review.

MEASUREMENTS: Incidence of potential delirium, falls, hospitalizations potentially due to adverse drug events, and mortality.

RESULTS: GRAM triggered monitoring plans for 491 residents. Newly admitted residents in the intervention homes experienced a lower rate of potential delirium onset than those in usual care homes (adjusted hazard ratio (HR)=0.42, 95% confidence interval (CI)=0.35–0.52), overall hospitalization (adjusted HR=0.89, 95% CI=0.72–1.09), and mortality (adjusted HR=0.88, 95% CI=0.66–1.16). In longer stay residents, the effects of the intervention were attenuated, and all estimates included unity.

CONCLUSION: Using health information technology in long-term care pharmacies to identify residents who might benefit from the implementation of prospective medication monitoring care plans when complex medication regimens carry potential risks for falls and delirium may reduce adverse effects associated with appropriate medication use.

A kinetic study of the liquid-phase hydrogenation of citral on Au/TiO2 and Pt-Sn/TiO2 thin films in capillary microreactors

The kinetics of the liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Au/TiO2 and Pt-Sn/TiO2 thin films was studied in the temperature range 313-353 K and citral concentrations of 0.25-10.0 mol m(-3). The thin films were deposited onto the inner walls of silica capillaries with internal diameter of 250 mu m. First-order dependence on hydrogen pressure and near zero order dependence on citral concentration were observed for the initial rate of citral hydrogenation over the Pt-Sn/TiO2 and Au/TiO2 thin films. The Au/TiO2 catalyst prevents citronellal formation. The highest yield of unsaturated alcohols was obtained on the Pt-Sn/TiO2 film at a reaction temperature of 343 K, liquid residence time of 30 min and a citral conversion of 99%. (C) 2011 Elsevier B.V. All rights reserved.