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991.
In the present paper the authors propose a portable and low-cost speckle interferometer for evaluating 3D deformation fields. The interferometer was designed and realized with the aim of carrying out measurements on small areas, hence it can be used to approach problems characterized by displacement field with highly localized gradients, such as the strain relief occurring in residual stress evaluation or the displacements which arise around notches or crack tips. The costs of the experimental equipment were reduced by employing laser diodes as light sources, a PZT actuator designed and calibrated by the authors and a control electronics realized on purpose. Moreover the configuration which was adopted allows further saving on optical components. The experimental results reported at the end of the paper, and obtained by a specimen subjected to 3D rigid body motions, show a high repeatability and accuracy. Furthermore the experimental results have shown that the geometry of the optical setup implies the variation of the sensitivity vectors on the inspected area, but this effect can be evaluated (analytically and/or experimentally) and taken into account in order to increase the accuracy of the measurements. 相似文献
992.
Maria Inês Bruno Tavares 《Polymer Testing》2000,19(8):899-904
Analysis of the dynamic behaviour of two highly crystalline polymers, polyethylene (HDPE) and polypropylene (iPP) was carried out by solution and solid state nuclear magnetic resonance (NMR) to obtain the response of the behaviour of both polymers with respect to the molecular chain dynamics, the chain ordination and the molecular packing. The proton spin-lattice relaxation time in the rotating frame (T1Hρ) showed that HDPE is more rigid than iPP, because the chain orientation and the molecular packing are different. T1Hρ parameter also depends on the molecular chain dynamics, as a result of the different sequence distribution in the domains 相似文献
993.
994.
The sulfone 2 , and the sulfoxides (S)‐ 3 and (R)‐ 3 were obtained by oxidation of the thiomethylene‐linked A*[s ]U dinucleoside 1 . Conformational analysis and association studies of 2 , (S)‐ 3 , and (R)‐ 3 reveal a strong influence of the configuration on the conformation of the linking unit and on the self‐association of the dinucleosides. 相似文献
995.
Bruno Romeira Ricardo Avó Julien Javaloyes Salvador Balle Charles N. Ironside José M. L. Figueiredo 《Optical and Quantum Electronics》2014,46(10):1391-1396
We investigate the dynamics of optoelectronic oscillator (OEO) systems based on resonant tunneling diode photodetector (RTD-PD) and laser diode hybrid integrated circuits. We demonstrate that RTD-based OEOs can be noise-activated in either monostable or bistable operating conditions, providing a rich variety of signal outputs—spiking, square pulses, bursting—and behaviours—stochastic and coherence resonances—that are similar to that of biological systems such as neurons. The potential for fully monolithic integration of our OEO confers them a great potential in novel neuromorphic optoelectronic circuits for signal processing tasks including re-timing and re-shaping of pulsed signals exploiting either the monostable or the bistable operating conditions. 相似文献
996.
997.
Cecile Baudin Christophe Pean Bruno Pellizzari Andree Gadelle Florence Fauvelle Jean-Claude Debouzy Jean-Pierre Dalbiez Bruno Perly 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):287-296
We report on the synthesis,characterization and ionic complexation properties ofhexakis (2-O-acetyl-3,6-anhydro)cyclomaltohexaose and hexakis (2-O-methyl-3,6-anhydro) cyclomaltohexaose usingthin-layer chromatography and Nuclear MagneticResonance spectroscopy. The selectivity towardscations depends on chemical modification of thehydroxyl groups and a very high specificity can beobtained in the case of lead for methylatedderivatives. 相似文献
998.
In the realm of topological automorphisms of totally disconnected locally compact groups, the scale function introduced by Willis in [19] is compared with the topological entropy. We prove that the logarithm of the scale function is always dominated by the topological entropy and we provide examples showing that this inequality can be strict. Moreover, we give a condition equivalent to the equality between these two invariants. Various properties of the scale function, inspired by those of the topological entropy, are presented. 相似文献
999.
1000.
M. Durante C. Bruno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):215-218
Exposure to cosmic radiation is today acknowledged as a major obstacle to
human missions to Mars. In fact, in addition to the poor knowledge on the
late effects of heavy ions in the cosmic rays, simple countermeasures are
apparently not available. Shielding is indeed very problematic in space,
because of mass problems and the high-energy of the cosmic rays, and
radio-protective drugs or dietary supplements are not effective. However,
the simplest countermeasure for reducing radiation risk is to shorten the
duration time, particularly the transit time to Mars, where the dose rate is
higher than on the planet surface. Here we show that using nuclear electric
propulsion (NEP) rockets, the transit time could be substantially reduced to
a point where radiation risk could be considered acceptable even with the
current uncertainty on late effects. 相似文献