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151.
Jos Roberto Berretta Wagner de Rossi Maurício David Martins das Neves Ivan Alves de Almeida Nilson Dias Vieira Junior 《Optics and Lasers in Engineering》2007,45(9):960-966
The technique to weld AISI 304 stainless steel to AISI 420 stainless steel with a pulsed Nd:YAG laser has been investigated. The main objective of this study was to determine the influence of the laser beam position, with respect to the joint, on weld characteristics. Specimens were welded with the laser beam incident on the joint and moved 0.1 and 0.2 mm on either side of the joint. The joints were examined in an optical microscope for cracks, pores and to determine the weld geometry. The microstructure of the weld and the heat affected zones were observed in a scanning electron microscope. An energy dispersive spectrometer, coupled to the scanning electron microscope, was used to determine variations in (weight %) the main chemical elements across the fillet weld. Vickers microhardness testing and tensile testing were carried out to determine the mechanical properties of the weld. The results of the various tests and examinations enabled definition of the best position for the incident laser beam with respect to the joint, for welding together the two stainless steels. 相似文献
152.
Nanoscale energetic materials 总被引:1,自引:0,他引:1
Carole Rossi 《Journal of Physics and Chemistry of Solids》2010,71(2):57-7447
153.
We model a feasible experiment involving two interacting microwave cavities with very different quality factors. An excitation is initially present in the high Q cavity. Modeling the environment as linearly coupled oscillators, we find a Zeno-like behavior which should occur when the dissipation constant is large enough as compared to the unitary coupling. 相似文献
154.
Paolo Ferruti Elisabetta Ranucci Amedea Manfredi Nicolò Mauro Elena Ferrari Riccardo Bruni Francesco Colombo Patrizia Mussini Manuela Rossi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5000-5010
Traditional precipitation methods for inorganic micropollutant removal from waters are increasingly being replaced by sorption methods based on both natural and synthetic materials. In this context, two novel effective heavy metal ions absorbers are presented. These resins, LYMA and LMT85, were crosslinked poly(amidoamine)s carrying amine and carboxyl groups in their repeating units. In particular, the LYMA‐repeating unit contains one carboxyl and two amine groups and is a mimic of L ‐lysine, whereas LMT85 contains two amine and five carboxyl groups and is a mimic of EDTA. Both resins were prepared at moderate cost by simple eco‐friendly procedures. The heavy metal ion set adopted as benchmark was Cu2+, Cd2+, Pb2+, Zn2+, Ni2+, and Co2+. LYMA proved selective for Cu2+ and Ni2+, the other ions tested being negligibly absorbed, whereas LMT85 proved capable of rapidly and quantitatively absorbing all the ions tested either singly or in mixed solution. The absorption process was reversible, and the resins were easily regenerated by acidification. The absorption of several metal ions imparted intense coloring to the resins, a feature possibly exploitable for analytical purposes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
155.
156.
Fulvio Ratto Paolo Matteini Alberto Cini Sonia Centi Francesca Rossi Franco Fusi Roberto Pini 《Journal of nanoparticle research》2011,13(9):4337-4348
We investigate the photothermal conversion and transformation of gold nanoparticles with an initial dogbone shape after dispersion
in hydrated chitosan films, which is a representative model of biological tissue, and excitation by a CW diode laser for 1 min.
Gold nanodogbones are observed to undergo a distinct modification above a sharp threshold of ~11 W cm−2 and 110 °C. Surprisingly, the very same modification is achieved up to at least 36 W cm−2 and 250 °C. We use an analytical model derived from Gans theory to associate the change in color of the films with the change
in shape statistics of these gold nanoparticles. This model proves both convenient and dependable. We interpret the photothermal
transformation as a rearrangement of particles with a dogbone shape and an aspect ratio of 4.1 into rods with an aspect ratio
of 2.5, where material from the end lobes of the dogbones may relocate to the waists of the rods. In turn, additional transitions
to stable gold nanospheres may exhibit fairly slower kinetics. 相似文献
157.
Francesco Acquasanta Corrado BertiMartino Colonna Maurizio FioriniSreepadaraj Karanam 《Polymer Degradation and Stability》2011,96(4):566-573
Recent regulation IEC 60335-1 ed.4 (2008) was introduced for materials used in electric appliance, establishing new limits in Glow Wire Ignition Temperature (GWIT) performance for materials used for electric connectors. Development of new products with high GWIT is possible, but the main issue is to keep good mechanical properties and processability, as well as tracking resistance (Comparative Tracking Index-CTI). Only a few patents and scientific publications exist about glow wire test performance of polymers. In this work we report GWIT and CTI properties for three engineering thermoplastic polymers (PBT, PET and PC). We have also studied the phenomena involved in this test, treating the phenomena with the parameterisation approach already used in the studies of the fire behaviour of polymers. PC, PBT and PET filled with 30% w/w glass fibres have been tested, and material properties that can be related to GWIT and CTI performance have been measured by TGA, Laser Flash Thermal Diffusivity (LFTD), Pyrolysis-GC/MS. CTI seems to be correlated with the char formation tendency of the materials, so PBT show a higher tracking resistance than PET and PC. Polycarbonate was the only material that passed the glow wire test (GWIT higher than 775 °C) but generally GWIT performance is not directly related with degradation temperature, since PET is thermally more stable compared with PBT, but less stable in glow wire test. The ignition process, together with the unsteady heat and mass transfer process characteristic of glow wire testing, are affected by many parameters at the same time. That’s why it is not easy to relate results of TGA, Laser flash, Pyrolysis-GC/MS with the glow wire ignition temperature of the materials tested, but the whole of these properties can give useful indication. 相似文献
158.
Maurizio A. P. Mingardi 《光谱学快报》2013,46(6):141-147
In the past five years, a number of d6 complexes have been found to exhibit luminescence when excited by ultraviolet light. Such emission has been assigned to d-d transitions localized on the metal ion, to charge-transfer transitions, and to ligand localized transitions2,3. The specific kind of emission observed is thought to depend on which electronic level lies lowest in energy. 相似文献
159.
We developed a constituent quark-diquark model for the nucleon and its resonances using a harmonic oscillator potential for
the interaction. The effects due to relativistic kinetic energy correction are studied. Finally, charge form factor of the
model is calculated and compared with experimental data.
相似文献
160.