Search results for "VENT"
showing 10 items of 24974 documents
Comparative study of the luminescence properties of macro- and nanocrystalline MgO using synchrotron radiation
2013
MgO nano-powder with an average crystallite size of nanoparticles ranging 10-15 nm was synthesized using the extractive-pyrolytic method and was studied by room temperature VUV spectroscopy under synchrotron radiation excitation. Comparative analysis of their luminescent properties with that of mac- rocrystalline powder analogues and an MgO single crystal, grown by the arc-fusion method, has been per- formed under excitation by pulsed VUV synchrotron radiation. Special attention was paid to VUV spectral range, which is not reachable with commonly used lamp and laser sources. A considerable blue shift of about 0.3 eV in the excitation spectra of 2.95 eV emission band, was revealed in nanocry…
Creation and thermal annealing of structural defects in neutron-irradiated MgAl 2 O 4 single crystals
2018
Abstract Several novel hole-type defects (a hole localized at a regular oxygen ion near a negatively charged structural defect) have been revealed in fast neutron irradiated MgAl2O4 crystals using the EPR method. The pulse annealing of the EPR signal of these centers was compared to that of radiation induced optical absorption in the same crystals. Taking into account the determined models of V1, V2 and V22 paramagnetic centers, the tentative scenario of the thermal annealing process of neutron-induced defects (hole-type and complementary electron F-type ones) is proposed. In addition, one more paramagnetic hole center consisting of an Al|Mg as-grown antisite defect near an aluminum vacancy…
EPR and optical spectroscopy of neutron-irradiated Gd3Ga5O12 single crystals
2020
Abstract In this paper, we have performed comparative analysis of EPR, optical absorption (OA) and luminescence spectra for a series of Gd3Ga5O12 (GGG) single crystals irradiated with fast neutrons with fluencies varied from 1016 to 1020n/cm2. In a crystal irradiated with the maximum neutron fluence, the EPR spectra demonstrated the formation of several paramagnetic defects. In particular, EPR spectrum shows a strong resonance at (effective) g ≈ 1.4 with practically isotropic behavior in the crystal rotation around the [1 1 1] direction (magnetic field being perpendicular to [1 1 1]) and several weaker lines in the g ≈ 1.1–2.6 region, which show more pronounced angular dependences. While th…
Comparison of Single Event Transients Generated at Four Pulsed-Laser Test Facilities-NRL, IMS, EADS, JPL
2012
Four pulsed-laser single-event effects systems, differing in wavelength and pulse width, were used to generate single event transients in a large-area silicon photodiode and an operational amplifier (LM124) to determine how transient amplitude and charge collection varied among the different systems. The optical wavelength and the focused spot size are the primary factors influencing the resultant charge density profile. In the large-area photodiode the transients can be distorted by high charge-injection densities that occur for tightly focused, higher energy optical pulses. When the incident laser-pulse energies are corrected for reflection losses and photon efficiency, with collection de…
Radiation resistance of nanolayered silicon nitride capacitors
2020
Abstract Single-layered and multi-layered 20–60 nm thick silicon nitride (Si3N4) dielectric nanofilms were fabricated using a low-pressure chemical vapour deposition (LPCVD) method. The X-ray photoelectron spectroscopy (XPS) confirmed less oxygen content in the multi-layered nanofilms. The capacitors with Si3N4 multilayer demonstrated a tendency to a higher breakdown voltage compared to the capacitors with Si3N4 single layer. Si3N4 nanofilms and capacitors with Si3N4 dielectric were exposed to 1 kGy dose of gamma photons. Fourier transform infrared (FTIR) spectroscopy analysis showed that no modifications of the chemical bonds of Si3N4 were present after irradiation. Also, gamma irradiation…
Mechanisms of Electron-Induced Single-Event Upsets in Medical and Experimental Linacs
2018
In this paper, we perform an in-depth analysis of the single-event effects observed during testing at medical electron linacs and an experimental high-energy electron linac. For electron irradiations, the medical linacs are most commonly used due to their availability and flexibility. Whereas previous efforts were made to characterize the cross sections at higher energies, where the nuclear interaction cross section is higher, the focus of this paper is on the complete overview of relevant electron energies. Irradiations at an electron linac were made with two different devices, with a large difference in feature size. The irradiations at an experimental linac were performed with varying en…
Marginal and internal fit evaluation of conventional metal-ceramic versus zirconia CAD/CAM crowns
2019
Background The purpose of this in vivo study was to compare the marginal and internal gap widths of monolithic zirconia crowns fabricated by CAD/CAM technique and metal-ceramic crowns fabricated by conventional technique. Material and methods 10 participants needing a single restoration were selected. Zirconia crowns using CAD/CAM technology (Group A) (n=10) and metal-ceramic crowns (Group B) (n=10) using lost wax casting technique were fabricated for each selected tooth. The marginal and internal gaps of crowns were recorded using a replica technique with light body silicone material stabilized with a regular set putty. Each replica was sectioned buccolingually and mesiodistally and then e…
Compact setup for spin-, time-, and angle-resolved photoemission spectroscopy.
2020
Review of scientific instruments 91(6), 063001 (2020). doi:10.1063/5.0004861
A Simple Approach for Determination of Numerical Values of Ferrite Nonlinear Susceptibilities
2020
This article presents a straightforward approach for determination of numerical values of nonlinear susceptibilities of soft magnetic ferrites. It is shown that numerical values of susceptibilities can be calculated from the measured amplitudes of harmonics in the output voltage of ferrite core transformer. For this purpose, useful expressions for the susceptibilities are derived and as example, numerical values of the largest nonlinear susceptibilities those of the third and fifth orders are calculated. Additionally, errors of the measured susceptibilities also are determined. Based on the expressions obtained, the analysis of phase shifts between components of flux density on different fr…
On asymmetric periodic solutions in relay feedback systems
2021
Abstract Asymmetric self-excited periodic motions or periodic solutions which are produced by relay feedback systems that have symmetric characteristics are studied in the paper. Two different mechanisms of producing an asymmetric oscillation by a system with symmetric properties are noted and analyzed by the locus of a perturbed relay system (LPRS) method. Bifurcation between the ability to excite symmetric and asymmetric oscillation with variation of system parameters is analyzed. An algorithm of finding asymmetric solutions is proposed.