Experimental study of laser dissimilar joining for Usibor 2000 and Al-T7075 with Tepex 102

Due to the needs of weight reduction in the automobile structures and of time reduction in the Body-In-White (BIW) manufacturing stage, effective and accurate dissimilar joining is demanded to take advantage of metal-polymer structures. Automotive industry is highly interested in the combination of metal alloys and composite materials; however, dissimilar joining of this type of materials without using mechanic or adhesive joining is a challenge. As an alternative to the classical joining techniques, laser technology can be used to join dissimilar materials. In laser direct joining, a laser beam is used to heat the metal and by conduction to heat the polymer up to melting temperature in the interface without reaching degradation temperature. In this work, an experimental procedure is proposed to set the basis of dissimilar joining between metal and composite parts for the automobile industry. To do that, laser texturing on metallic parts was studied and a wide battery of experimental test were performed to obtain the proper joining process parameters for dissimilar joining between Usibor 2000 and Al-T7075 with Tepex 102. Results show that is possible to reach over 17 MPa in lap shear adhesion test which is similar to the performance of typical adhesives used in automotive industry.Authors wish to thank Basque Country Government for financial support provided through MULTIMAT project Elkartek KK2017/00088 as well as the Spanish Industry ministry for support provided in INTEGRADDI project DPI 2016-79889

Diffusion of Hydrogen in Pd Assisted by Inelastic Ballistic Hot Electrons

Sykes {\it et al.} [Proc. Natl. Acad. Sci. {\bf 102}, 17907 (2005)] have reported how electrons injected from a scanning tunneling microscope modify the diffusion rates of H buried beneath Pd(111). A key point in that experiment is the symmetry between positive and negative voltages for H extraction, which is difficult to explain in view of the large asymmetry in Pd between the electron and hole densities of states. Combining concepts from the theory of ballistic electron microscopy and electron-phonon scattering we show that H diffusion is driven by the $s$-band electrons only, which explains the observed symmetry.Comment: 5 pages and 4 figure

First CRDS-measurements of water vapour continuum in the 940nm absorption band

Measurements of near-infrared water vapour continuum using continuous wave cavity ring down spectroscopy (cw- CRDS) have been performed at around 10611.6 and 10685:2 cm1. The continuum absorption coefficients for N2- broadening have been determined for two temperatures and wavenumbers. These results represent the first near-IR continuum laboratory data determined within the complex spectral environment in the 940nm water vapour band and are in reasonable agreement with simulations using the semiempirical CKD formulation

Residual do herbicida atrazina em solo cultivado com milho e na água de irrigação de arroz cultivado em sequência.

bitstream/item/60627/1/boletim-137.pd

Bending modes, anharmonic effects and thermal expansion coefficient in single layer and multilayer graphene

We present a simple analytical approach to study anharmonic effects in single layer, bilayer, and multilayer graphene. The coupling between in plane and out of plane modes leads to negative Gr\"uneisen coefficients and negative thermal expansion. The value of the thermal expansion coefficient depends on the coupling to the substrate. The bending rigidity in bilayer graphene shows a crossover between a long wavelength regime where its value is determined by the in plane elastic properties and a short wavelength regime where its value approaches twice that of a single layer

Aperiodic invariant continua for surface homeomorphisms

We prove that if a homeomorphism of a closed orientable surface S has no wandering points and leaves invariant a compact, connected set K which contains no periodic points, then either K=S and S is a torus, or $K$ is the intersection of a decreasing sequence of annuli. A version for non-orientable surfaces is given.Comment: 8 pages, to appear in Mathematische Zeitschrif

Shuttle Mechanism for Charge Transfer in Coulomb Blockade Nanostructures

Room-temperature Coulomb blockade of charge transport through composite nanostructures containing organic inter-links has recently been observed. A pronounced charging effect in combination with the softness of the molecular links implies that charge transfer gives rise to a significant deformation of these structures. For a simple model system containing one nanoscale metallic cluster connected by molecular links to two bulk metallic electrodes we show that self-excitation of periodic cluster oscillations in conjunction with sequential processes of cluster charging and decharging appears for a sufficiently large bias voltage. This new `electron shuttle' mechanism of discrete charge transfer gives rise to a current through the nanostructure, which is proportional to the cluster vibration frequency.Comment: 4 pages, 4 figure

Inherent tracers for carbon capture and storage in sedimentary formations: composition and applications

Inherent tracers - the “natural” isotopic and trace gas composition of captured CO₂ streams – are potentially powerful tracers for use in CCS technology. This review outlines for the first time the expected carbon isotope and noble gas compositions of captured CO₂ streams from a range of feedstocks, CO₂-generating processes and carbon capture techniques. The C-isotope composition of captured CO₂ will be most strongly controlled by the feedstock, but significant isotope fractionation is possible during capture; noble gas concentrations will be controlled by the capture technique employed. Comparison with likely baseline data suggests that CO₂ generated from fossil fuel feedstocks will often have δ13C distinguishable from storage reservoir CO₂. Noble gases in amine-captured CO₂ streams are likely to be low concentration, with isotopic ratios dependant on the feedstock, but CO₂ captured from oxyfuel plants may be strongly enriched in Kr and Xe which are potentially valuable subsurface tracers. CO₂ streams derived from fossil fuels will have noble gas isotope ratios reflecting a radiogenic component that will be difficult to distinguish in the storage reservoir, but inheritance of radiogenic components will provide an easily recognisable signature in the case of any unplanned migration into shallow aquifers or to the surface

Phytosociological characterization of weeds as a function of residual herbicides applied to rice grown under sprinkler irrigation.

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