Search results for "defect"
showing 10 items of 879 documents
Intrinsic defects induced by β-irradiation in silica
2002
We report an electron paramagnetic resonance study of defects induced by β-irradiation in natural and synthetic samples of high purity commercial silica. Data are collected for the E′ centers and a resonance satellite signal split by 1.36 mT. By comparison with the effects of γ-irradiation it is shown that the mechanisms of defect generation are the same for the two irradiation sources and that in the high-dose limit they involve intrinsic defects of the glassy matrix. Moreover, the high concentration of defects generated by β-irradiation modifies the EPR spectrum due to spin–spin interaction.
Local structure of gallate proton conductors
2009
Lanthanum barium gallate proton conductors are based on disconnected GaO4 groups. The insertion of hydroxyls in the LaBaGaO4 network proceeds through self-doping with Ba2+, consequent O2- vacancy formation to fulfill charge neutrality. With a structural investigation on self-doped LaBaGaO4 oxides using synchrotron XRD and EXAFS on the Ga K-edge, we find that: (a) the GaO4 tetrahedra retain their size throughout the whole series; (b) the GaO4 tetrahedra rotate as rigid bodies on hydration, leading to the formation of a network of shorter O-O configurations that are stabilized by hydrogen bonds; (c) contraction of the lattice occurs along the a unit cell axis, as a consequence of an overall s…
Theoretical simulations of regular and defective aluminium nitride nanotubes
2007
For theoretical simulation on AlN nanotubes (NTs) of different chiralities (armchair-and zigzag-type) and uniform diameters, we have considered their single-walled (SW) 1D periodic models. For this aim, we have performed ab initio DFT calculations on AlN SW NTs using formalism of the localized Gaussian-type atomic functions as implemented in CRYSTAL-03 computer code. We have shown that the smaller the diameter of AlN single-walled nanotube is, the closer its electronic and structural properties to AlN bulk. We have analysed an influence of N vacancies (neutral F centres) created by either soft irradiation of nanotubes or under experimental conditions of their growth, on the atomic and elect…
Incidence of PV module rated power tolerances on PV system energy production
2016
Discussing the electrical energy production of a PV system realized by PV modules with a large range of tolerance for the rated power values is the aim of this paper. In particular, the paper shows how the incidence of tolerance can be significant, in terms of output power reduction, when the PV system works in partial shading condition. For this issue, using a tool developed for this purpose, several simulations have been run, which consider different tolerance values for the module rated power and different shading patterns for the PV array. The authors quantify the peak power values of the different system configurations, showing the importance of the choice of modules with reduced toler…
Eficacia de procesamiento de los entrañamientos y de las implicaturas conversacionales generalizadas: la lógica deductiva y la lógica por defecto
2022
This work aims to study the processing differences that occur between deductive logic and default logic. Since the entailments are based on deductive logic and generalised conversational implicatures (GCI) are built from the default logic, two questionnaires were proposed to collect the processing efficiency expressed as the number of hits per minute. The data collected shows that there is a significant difference in the processing of entailments and ICGs: entailments are processed more efficiently than ICGs and, therefore, it is concluded that the default logic requires greater cognitive effort. Este trabajo tiene como objetivo estudiar las diferencias de procesamiento que se producen al a…
Defect detection in additively manufactured titanium prosthesis by flying laser scanning thermography
2018
Abstract Metal additive manufacturing is nowadays a well-established technology for cutting edge applications in the automotive, aerospace, defense and medical sectors. Since additive metal deposition is basically a welding method, which creates parts by successively adding layers of material, there is a chance for defects like pores, cracks, inclusions and lack of fusion to develop. As a matter of fact, interlayer and intralayer defects are often observed in additive manufactured components. However, if one considers the typical end applications along with the high costs involved in metal additive manufactured components, a “zero defect” target is close to mandatory for this technology. Pl…
Assisted Reproductive Techniques and Risk of Congenital Heart Diseases in Children: a Systematic Review and Meta-analysis
2023
AbstractInfertility is a growing phenomenon and leads to an increased use of assisted reproductive techniques (ARTs). In recent years, concerns about the safety of these procedures emerged and ARTs were hypothesized to be a risk factor for developing congenital heart diseases (CHDs) in offspring. Our aim is to investigate the association between ART and CHD, specifying results according to various subtypes of defects. We performed a systematic review and random-effects meta-analysis following the PRISMA guidelines. MEDLINE and Google Scholar were searched from January 2011 to May 2022. Data about incidence of CHD in ART were tabulated and extracted from all the studies included. Twenty-four…
<title>Annealing of radiation defects in x-irradiated LiBaF<formula><inf><roman>3</roman></inf></formula>&l…
2003
Results of the glow rate technique application for analysis of the activation energy of thermostimulated annealing of X-ray created F-type color centers in pure and containing oxygen centers LiBaF3 crystals are presented. It is shown that depending on the impurity composition two alternative mechanisms could be involved in the annealing of color centers. It is proposed that either the anion vacancy governed migration of F-centers resulting in recombination with complementary defects, or the thermal delocalization of radiation created fluorine (Fi) interstitials captured by anti-structure defects followed by recombination with all kinds of complementary F-type centers are responsible for the…
Generation of defects in amorphous SiO(2) assisted by two-step absorption on impurity sites.
2011
Generation of the Si dangling bond defect in amorphous SiO(2) (E' centre) induced by tunable pulsed UV laser radiation was investigated by in situ optical absorption measurements. The defect generation efficiency peaks when the photon energy equals ∼5.1 eV, it depends quadratically on laser intensity and is correlated with the native linear absorption due to Ge impurities. We propose a model in which the generation of E' is assisted by a two-step absorption process occurring on Ge impurity sites.
Influence of hydrogen on paramagnetic defects induced by UV laser exposure in natural silica
2005
Diffusion limited reactions of point defects were investigated in amorphous SiO2 exposed to UV laser light. Electron spin resonance and in situ absorption measurements at room temperature evidenced the annealing of E' centers and the growth of H(II) centers both occurring in the post-irradiation stage and lasting a few hours. These transients are caused by reactions involving molecular hydrogen H2, made available by dimerization of radiolytic H0.