Search results for "Surfaces"
showing 10 items of 2837 documents
An improved five-parameter model for photovoltaic modules
2010
This paper presents a new five-parameter model capable of analytically describing the I–V characteristic of a photovoltaic module for each generic condition of operative temperature and solar irradiance. The parameters of the equivalent electrical circuit are extracted by solving a system of equations based on data commonly issued by manufacturers in standard rating conditions with a trial and error process. The procedure, which does not require any special equations solver, can be easily coded into a short software routine using simple languages and finds the solution of the system of equations with the desired accuracy without needing to be guided towards solutions starting from fitted in…
Experimental data collection and modelling of dry deposition velocities for urban surfaces
2018
Dry deposition process is recognized as an important pathway among the removal processes of radioactive pollutants in atmosphere. There is not a unique and accepted theoretical description of involved dry deposition phenomena due to the complexity of the fluid-dynamic processes that influence the deposition flux, but also because there is a lack of experimental data covering all scenarios of interest. In this paper, that is the result of a National Research Program a research activity conducted by DEIM Department of the University of Palermo and ENEA and funded by the Italian Minister of Economic Development, a new schema for parameterization of particle dry deposition velocity on urban are…
Silicate and Hydroxide Concentration Influencing the Properties of Composite Al2O3-TiO2 PEO Coatings on AA7075 Alloy
2021
This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties of Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L−1 potassium titanyl oxalate, (PTO), using a unipolar waveform with constant current density. The surface and cross-section characteristics of PEO coatings including morphology, elemental distribution, and phase composition were evaluated using FESEM, EDS, and XRD techniques. Voltage-time response indicated the concentration of SMS and KOH had a significant effect on the duration of each stage of the PEO process. More cracks and pores were formed at the higher concent…
Advances in selective conversions by heterogeneous photocatalysis
2010
Selective photocatalytic conversions are offering an alternative green route for replacing environmentally hazardous processes with safe and energy efficient routes. This paper reports the most recent advances in the application of heterogeneous photocatalysis to synthesize valuable compounds by selective oxidation and reduction.
The 3D modelling of musive surfaces for a monitoring protocol
2022
In questo lavoro l'utilizzo della metodologia digitale tridimensionale per la scansione di superfici musive è stato indagato nell'ambito dell'intervento di restauro di un mosaico pavimentale all'interno della Cappella Palatina di Palermo. Grazie alla possibilità di sezionare il modello di maglia con un software di rappresentazione digitale, è stato possibile confrontare la superficie della maglia con una superficie piana di riferimento allo scopo di valutare uno dei declini della posta dei pavimenti musivi, ovvero l'abrasione delle superfici In this paper the use of three-dimensional digital methodology for scanning musive surfaces was investigated within the restoration intervention on a f…
Deformation
2020
In the continuous model of a solid object, which is ideally considered composed of such material points that each one of them is surrounded by a dense neighbourhood fully occupied by other points, the deformation is a variation carried out by a transformation, which does not preserve isometry. Deformations differ from displacements caused by rigid motions. For a closed boundary curve in the three-dimensional space, Plateau wondered what surfaces would minimize the potential surface energy. Deformation was held to underlie the evolution of biological forms, described by the “Cartesian transformations”, or the interpolation function of landmarks covariation over a thin-plate spline, the perce…
Picture
2020
Pictures are a presentation whose structure is decomposable into a surface, an arrangement of markings, the appearance of something in front of, before or behind the surface, the reference to a scene of the real or a possible world, whose aspects and concrete or abstract states of affairs are displayed by the appearance. Pictures are a kind of markings, namely patterns perceived on a surface, which do not yet convey information about it. Markings depend on surfaces. No marking exists without a surface, while the opposite is true. There is a variety of markings according to the technique and the tools chosen to produce them. Surfaces serve as a medium either as a support or as that which aff…
Metastable oxygen atom velocity and temperature in supersonic CO2plasma expansions
2008
Radial and axial velocity distribution functions of metastable oxygen atoms were obtained by way of resonant laser induced fluorescence spectroscopy at 777.19 nm in rarefied supersonic plasma jets produced from pure CO2 and CO2–N2 gas mixtures. The N2 seeded fraction is 3% in volume in order to mimic the Martian atmosphere composition. The measured lineshapes allow computation of the mean radial velocity and the perpendicular temperature, with respect to the jet axis, as well as the mean axial velocity and the parallel temperature. With an arcjet plasma source input power of 6.5 kW, the metastable O(5S) atom axial velocity is around 4500 m s−1 and the atom perpendicular temperature reaches …
Analysis of laser shock waves and resulting surface deformations in an Al-Cu-Li aluminium alloy
2012
Abstract Laser shock processing is now a recognized surface treatment for improving fatigue or corrosion behaviour of metallic materials through the generation of a compressive stress field. In turn, the analysis of shock wave propagation is of primary importance to predict numerically morphological and mechanical surface modifications. Considering experimental and numerical analyses of shock wave propagation, and surface deformations induced by single impacts, a 2050 aluminum alloy having different microstructures was investigated under laser-shock loading. In a first step, the evolution of shock wave attenuation and elastic precursor amplitude was correctly reproduced by finite element si…
Ceramic materials wear mechanisms when cutting nickel-based alloys
1999
Abstract In this paper the performances of some commercial ceramic inserts when cutting AISI 310 steel are investigated and compared to those of a traditional carbide based tool. The most important wear mechanism in the ceramic inserts is related to the segmented edges of the chips that abrade a notch at the end of the cut zone. Alumina–zirconia inserts are very sensitive to this kind of wear, whereas tools made of Sialon and alumina with SiC whiskers exhibit slightly better performances despite the concomitant chemical wear mechanisms.