Search results for "Solid"
showing 10 items of 3575 documents
Three-state Landau-Zener model in the presence of dissipation
2019
A population transfer based on adiabatic evolutions in a three-state system undergoing an avoided crossing is considered. The efficiency of the process is analyzed in connection with the relevant parameters, bringing to light an important role of the phases of the coupling constants. The role of dissipation is also taken into account, focusing on external decays that can be described by effective non-Hermitian Hamiltonians. Though the population transfer turns out to be quite sensitive to the decay processes, for very large decay rates the occurrence of a Zeno-phenomenon allows for restoring a very high efficiency.
Aspects of the characterization of cloverite by solid-state n.m.r. techniques
1993
Abstract Microporous gallophosphate cloverite has been studied by multinuclear ( 13 C, 19 F, 31 P, 71 Ga) solid-state n.m.r. spectroscopy. An extraordinarily strong quadrupolar coupling is shown to be the reason for a misleading line shape in 71 Ga MAS n.m.r. spectra. Using static 71 Ga n.m.r. spectroscopy, an estimate of the size of this quadrupolar coupling can be obtained. The limitations of the MAS technique for the study of quadrupolar nuclei in sites with very large quadrupolar couplings are addressed.
Covid-19 and Social Structure: Three Key Words for Future Orientation
2022
The paper deals on three keywords to orientation in the future by focusing on three crucial concepts: 1. The sharing economy, regarding the transformation emerging in contemporary economic scenarios; 2. The creative imagination, concerning the changes that are taking place in technological developments and linked not only to production systems but also to the consumption of goods and services; 3. The solidarity, in relation to the global changes all over the world. We will see that such three keywords, which recall specific areas of social and economic fields, are strongly interconnected to each other, especially when we look at the effects of the pandemic on the future of society.
Reliability Estimation of Optimal Viscoelastic Composite Shells in Critical-Time Calculations
2003
The problem of reliability estimation for optimal viscoelastic composite shells in critical-time calculations is considered. The weight minimization of a viscoelastic composite shell, with constraints on deflections at the critical time, leads to a system deforming unstably, whose deflections grow in time with an increasing rate. A method for estimating the reliability of such shells in calculating the critical time is discussed. This time is regarded as a random variable depending on many, roughly equivalent, factors. An analysis of the reliability is carried out for different values of coefficients of variation, occurring in practice.
Vertical distribution of crop load and fruit quality within vase- and Y-shaped canopies of 'Elegant Lady' peach
2005
Canopy shape and depth may influence crop uniformity of peach trees at harvest. To test this hypothesis we examined yield distribution and fruit quality changes at different canopy levels of peach trees trained to delayed vase (DV) and perpendicular Y (Y). Trees of both training forms were divided vertically into six or seven 50-cm-deep layers and fruit was harvested at commercial ripening from each layer separately. Regardless of training form, number of fruit and yield per layer were highest in the central part of the canopy, but more evenly distributed among canopy layers in Y trees. In DV trees, fruit weight decreased linearly from top to bottom, whereas it remained constant along the t…
Analytical approach for the mix design optimisation of bituminous mixtures with crumb rubber
2018
The present paper provides a basis for defining a mix design method specifically tailored to rubberised asphalt that takes into account the behaviour of crumb rubber. An analytical approach to quantifying the recovered deformation of crumb rubber in the post-compaction phase has been developed in order to adjust the number of gyrations proposed by the Superpave method for compacting specimens of hot mix asphalt using a Superpave gyratory compactor. The maximum allowable amount of rubber has been calculated. Finally, a step-by-step protocol has been proposed in order to fabricate and compact crumb rubber modified mixtures with the gyratory compactor.
Ab initio calculations of SrTiO3, BaTiO3, PbTiO3, CaTiO3, SrZrO3, PbZrO3 and BaZrO3 (001), (011) and (111) surfaces as well as F centers, polarons, K…
2014
In this paper, the review of recent results of calculations of surface relaxations, energetics, and bonding properties for ABO 3 perovskite (001), (011) and (111) surfaces using mostly a hybrid description of exchange and correlation is presented. Both AO and BO 2-terminations of the nonpolar (001) surface and A , BO , and O terminations of the polar (011) surface, as well as B and AO 3-terminations of the polar (111) surface were considered. On the AO -terminated (001) surface, all upper-layer A atoms relax inwards, while all second layer atoms relax outwards. For the BO 2-terminated (001) surface, in most cases, the largest relaxations are on the second-layer metal atoms. For almost all …
Radiation damage in zircon
2003
A single, zoned, Sri Lankan zircon exhibits a range of microstructures from crystalline to nearly amorphous that are the result of radiation damage over a dose range of 2.1–10.1·1015 α-decay events/mg (0.16–0.47 dpa). The zones in the crystal were examined at a variety of length scales using optical microscopy, micro-Raman spectroscopy, electron microprobe analysis, and transmission electron microscopy. Birefringence varies linearly with dose: birefringence = −4.71·10−18 /g· D α + 4.86·10−2. Full width at half maximum (FWHM) measurements of the B1g(ν3) peak, as determined by micro-Raman spectroscopy, were used to estimate the extent of radiation damage in each zone. The radiation dose (calc…
<title>High-excitation-density luminescence as probe of mixed silver halides</title>
1992
Two kinds of intrinsic luminescence in mixed AgBr1-xClx (1 io. Dependence of the parameters of this process on crystal composition has been investigated in terms of spatially well correlated Frenkel defect recombinations. The main effect found was the linear increase of the Agio migration energy with the crystal composition x. The second kind of luminescence arising due to exciton molecules has been shown to be sensitive to the solid solution composition and the quality of a crystal. It is shown that this luminescence correlates with the optical losses of the fibers studied.
Hardening and formation of dislocation structures in LiF crystals irradiated with MeV–GeV ions
2002
Abstract Material modifications of LiF crystals irradiated with Au, Pb and Bi ions of MeV to GeV energy are studied by means of microindentation measurements and dislocation etching. Above a critical irradiation fluence of 10 9 ions/cm 2 , the microhardness can improve by a factor of 2 in the bulk and by more than 3 on the surface. Radiation-induced hardening follows the evolution of the energy loss along the ion path. Annealing experiments indicate that complex defect aggregates created in the tracks play a major role for the hardness change. Evidence for severe structural modifications is found when etching indentation impressions in highly irradiated crystals leading to similar pattern a…