Search results for "63"

Historia verdadera del perverso Emperador Constante, y pasion, y muerte de San Martin, Papa, muy semejante à la de Jesu-Christo Señor nuestro Sacada …

Data presa del Catálogo Colectivo del Patrimonio Bibliográfico Español Sign.: [A]-B2, C[8 Reclams Grav. xil. enmarcat a la port. avant del tít., representant a Sant Martí Frisos

2017

Abstract Chromic acid anodizing is important for the corrosion protection of aerospace aluminium alloys. Previous study has demonstrated that SO 4 2 − impurity in the chromic acid affects the film growth on aluminium at a voltage of 100 V. The present work further investigates aluminium and extends the study to industrial anodizing conditions (Bengough-Stuart (B-S) process) and to the AA 2024-T3 alloy. It is shown that SO 4 2 − concentrations between ~ 38–300 ppm reduce the film growth rate for aluminium anodized at 100 V in comparison with an electrolyte than contains ≤ 1.5 ppm SO 4 2 − , whereas ~ 1500–3000 ppm SO 4 2 have an opposite effect and lead to an unstable pore diameter. Under th…

Influence of nanoporous structure on mechanical strength of aluminium and aluminium alloy adhesive structural joints

2006

The influence of surface treatments on the mechanical strength of adhesive joints was investigated. The attention was focused on AA2024 alloy because it is extensively used in both the automotive and aerospace industries. Adhesive joints fabricated with pure aluminium were also investigated in order to evidence possible differences in the surface features after identical treatments. Before joining with a commercial epoxy adhesive, metal substrates were subjected to different kinds of treatment and the surfaces were characterized by SEM analysis. The formation of a microporous surface in the AA2024 alloy, upon etching and anodizing, is discussed on the basis of the role of the intermetallic …

Polarized multiplex coherent anti-Stokes Raman scattering using a picosecond laser and a fiber supercontinuum

2011

International audience; We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600–2000 cm−1 spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant …

Mechanical behavior of a sandwich with corrugated GRP core: numerical modeling and experimental validation

2014

In this work the mechanical behaviour of a core reinforced composite sandwich structure is studied. The sandwich employs a Glass Reinforced Polymer (GRP) orthotropic material for both the two external skins and the inner core web. In particular, the core is designed in order to cooperate with the GRP skins in membrane and flexural properties by means of the addition of a corrugated laminate into the foam core. An analytical model has been developed to replace a unit cell of this structure with an orthotropic equivalent thick plate that reproduces the in plane and out of plane behaviour of the original geometry. Different validation procedures have been implemented to verify the quality of t…

Fabrication of carbon nanotube-based field-effect transistors for studies of their memory effects

2007

Carbon nanotube‐based field‐effect transistors (CNTFETs) have been fabricated using nanometer thin dielectric material as the gate insulator film. The demonstrated fabrication technique is highly suitable for preparing devices with low contact resistances between the electrodes and the carbon nanotube, down to 14 kΩ. Electronic transport measurements of the fabricated devices have been conducted on more than 70 FETs. Hysteretic behavior in the transfer characteristics of some CNTFETs was observed.

A numerical and experimental study through laser thermography for defect detection on metal additive manufactured parts

2017

Additive manufacturing has been recently employed in industrial sectors with the fundamental requirement for zero defect parts. Technological developments in additive manufacturing notwithstanding, there continues to be a scarcity of non-destructive inspection techniques to be exploited during the manufacturing process itself, thus limiting industrial advancements and extensive applications. Therefore, being able to integrate the defect inspection phase within the additive manufacturing process would open the way to enabling corrective actions on the component in itinere, that is, before reaching the final product. For this reason, new methods of in-process monitoring are gaining more and m…

On microstructural phenomena occurring in friction stir welding of aluminium alloys

2006

Abstract The results of experimental activity on friction stir welding (FSW) of aluminum alloys are reported. Butt joints of two different materials, namely AA2024-T4 and AA7075-T6, were investigated from a metallurgical point of view. Grain dimensions and insoluble particle densities were investigated both in the parent materials and in the joints. Furthermore, the effect of post-welding heat treatments on the joint strength was studied.

Acoustic modes in metallic nanoparticles: atomistic versus elasticity modeling

2009

The validity of the linear elasticity theory is examined at the nanometer scale by investigating the vibrational properties of silver and gold nanoparticles whose diameters range from about 1.5 to 4 nm. Comparing the vibration modes calculated by elasticity theory and atomistic simulation based on the Embedded Atom Method, we first show that the anisotropy of the stiffness tensor in elastic calculation is essential to ensure a good agreement between elastic and atomistic models. Second, we illustrate the reduction of the number of vibration modes due to the diminution of the number of atoms when reducing the nanoparticles size. Finally, we exhibit a breakdown of the frequency-spectra scalin…

Vibrations of free and embedded anisotropic elastic spheres:Application to low-frequency Raman scattering of silicon nanoparticles in silica

2004

Vibrational mode frequencies and damping are calculated for an elastic sphere embedded in an infinite, homogeneous, isotropic elastic medium. Anisotropic elasticity of the sphere significantly shifts the frequencies in comparison to simplified calculations that assume isotropy. New low-frequency Raman light scattering data are presented for silicon spheres grown in a ${\mathrm{SiO}}_{2}$ glass matrix. Principal features of the Raman spectrum are not correctly described by a simple model of the nanoparticle as a free, isotropic sphere, but require both matrix effects and the anisotropy of the silicon to be taken into account. Libration, not vibration, is the dominant mechanism.