Use of an amorphous iron oxide hydrated as catalyst for hydrogen peroxide oxidation of ferulic acid in water

The abatement of ferulic acid (FA), a polyphenolic constituent of olive mill wastewater, is studied in the pH range 5.0-7.0 by using hydrogen peroxide and an amorphous iron oxide as catalyst. The effect of pH, catalyst load, hydrogen peroxide and substrate starting concentrations is assessed during the investigation. A suitable reaction scheme is developed and used to build a mathematical model which satisfactorily describes the system's behavior. Kinetic constants for the proposed scheme as well as the total active site concentration of the catalyst in the studied pH range are estimated. The occurrence of internal mass-transfer limitation for the adopted granulometric fraction of the catalyst is demonstrated.     

Ferroelectric hollow particles obtained by solid-state reaction

Hollow particles of barium titanate were obtained by a two-step process combining colloidal chemistry and solid-state reaction. BaCO(3) crystals (size ≈1?μm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphous TiO(2) shell using a precipitation process. Calcination of the BaCO(3)@TiO(2) core-shell particles at 700?°C resulted in the formation of BaTiO(3) hollow particles (shell thickness of ≈70?nm) which retain the morphology of the BaCO(3) crystals. Formation of the cavity occurs because out-diffusion of the core phase is much faster than in-diffusion of the shell material. X-ray diffraction (XRD) and Raman spectroscopy indicate that the hollow particles possess a tetragonal ferroelectric structure with axial ratio c/a = 1.005. Piezoresponse force microscopy has shown strong piezoactivity and 180° ferroelectric domains. The process described provides a general route to fabricate hollow ferroelectric structures of several compounds.     

Experimental analysis and modelling of bolted T-stubs under cyclic loads

Bolted connections have recently attracted new research efforts after the unexpected failures of welded connections during Northridge and Kobe earthquakes. The criteria and the formulations for predicting the rotational stiffness and the flexural resistance, under static loading conditions, of the most common connection typologies have been codified by Eurocode 3 [CEN. EN 1993-1-8 Eurocode 3: Design of steel structures — Part 1.8 Design of joints. 2005] which is based on the so-called component approach. In order to extend the component approach to the prediction of the seismic response of partial-strength connections, the modelling of the cyclic response of the joint components is necessary. Starting from the observation that the main sources of deformability and plastic deformation capacity of bolted connections can be modelled by means of an equivalent T-stub, an experimental program devoted to the cyclic response of the most important component of bolted connections has been carried out aiming at the modelling of the cyclic force-displacement curve of bolted T-stubs. In this paper, starting from the analysis of the results of the experimental tests performed, stiffness and strength degradation rules are derived as a function of the displacement amplitude required at any cycle and of the energy dissipated in the previous loading history. The combination of these rules with the theoretical prediction of the monotonic envelope leads to a proposal for predicting the cyclic behaviour of bolted T-stubs starting from the knowledge of their geometrical and mechanical properties.     

Application of the SKYRAD Improved Langley plot method for the in situ calibration of CIMEL Sun-sky photometers

The in situ procedure for determining the solar calibration constants, originally developed for the PREDE Sun-sky radiometers and based on a modified version of the Langley plot, was applied to a CIMEL instrument located in Valencia, Spain, not integrated into AERONET. Taking into account the different mechanical and electronic characteristics of the two radiometers, the method was adapted to the characteristics of the CIMEL instrument. The iterative procedure for the determination of the solar calibration constants was applied to a 3-year data set. The results were compared with the two sets of experimental calibration constants determined during this period using the standard Langley plot method. The agreement was found to be consistent with the experimental errors, and the method can definitely also be used to determine the solar calibration constant for the CIMEL instrument, improving its calibration. The method can be used provided the radiometer is previously calibrated for diffuse radiance using a standard lamp.     

Calculations of light scattering from isolated and interacting metallic nanowires of arbitrary cross section by means of Green's theorem surface integral equations in parametric form

We study theoretically the light scattering from metal wires of arbitrary cross section, with emphasis on the occurrence of plasmon resonances. We make use of the rigorous formulation of the Green's theorem surface integral equations of the electromagnetic wave scattering, written for an arbitrary number of scatterers described in parametric form. We have investigated the scattering cross sections for nanowires of various shapes (circle, triangles, rectangles, and stars), either isolated or interacting. The relationship between the cross sectional shape and the spectral dependence of the plasmon resonances is studied, including the impact of nanoparticle coupling in the case of interacting scatterers. Near-field intensity maps are also shown that shed light on the plasmon resonance features and the occurrence of local field enhancements.     

A second-generation voltage conveyor (VCII)–based simulated grounded inductor

In this paper, an implementation of a simulated grounded inductor (SGI) based on a recently developed active building block called second-generation voltage conveyor (VCII) is proposed. The proposed SGI employs two VCIIs, two resistors, and one grounded capacitor, which is preferred when integration is involved. More importantly, unlike most of the other previously reported SGIs, this one is free from any restrictive matching conditions. A complete analysis of nonidealities along with sensitivity treatment by considering parasitic impedances and nonideal gains of the VCII are performed. A simple VCII circuit is designed to be used in the implementation of the proposed SGI. To support the presented theory, Pspice simulation results using 0.18-μm CMOS technology parameters and supply voltage of ±0.9 V are provided. On the basis of the achieved results, the proposed SGI operates in a good agreement with an ideal inductor. The power consumption is only 0.65 mW, and the parasitic series impedance is approximately 191.9 Ω. The applicability of the proposed SGI is tested by using it in a standard second-order high-pass RLC filter.     

Determination of REE,U,Th,Ba,and Zr in simulated hydrogeological leachates by ICP-AES after matrix solvent extraction

A fast, reliable and precise method for the determination of Ba, Zr, Th, U, La, Ce, Eu, Hf and Gd in leaching solutions containing up to 1 mol/L FeCl3 by inductively coupled plasma-atomic emission spectrometry (ICP-AES) was described. Liquid-liquid extraction with diethyl ether was applied for selective and quantitative extraction of the iron with a decontamination factor of 65000. The study has enabled the determination of rare earth elements, U, Th Ba, and Zr, from the solution with high iron content with detection limits in the range of 1-24 ng/ml and a precision of 0.9%-4.6 % relative standard deviation. The developed method was simple and was adopted for implementation in a glove box for handling radioactive materials.     

High concentration photovoltaic systems applying III–V cells

High concentration systems make use of the direct solar beam and therefore are suitable for application in regions with high annual direct irradiation values. III–V PV cells with a nominal efficiency of up to 39% are readily available in today's market, with further efficiency improvements expected in the years ahead. The relatively high cost of III–V cells limits their terrestrial use to applications under high concentration, usually above 400 suns. In this way the relatively high cell cost is compensated through the low amount for cells needed per kW nominal system output.This paper presents a state of the art of high concentration photovoltaics using III–V cells. This PV field accounts already for more than 20 developed systems, which are commercially available or shortly before market introduction.