Search results for "Nonlinear system"
showing 10 items of 1446 documents
Pressure-induced band anticrossing in two adamantine ordered-vacancy compounds: CdGa2S4 and HgGa2S4
2021
Abstract This paper reports a joint experimental and theoretical study of the electronic band structure of two ordered-vacancy compounds with defect-chalcopyrite structure: CdGa2S4 and HgGa2S4. High-pressure optical-absorption experiments (up to around 17 GPa) combined with first-principles electronic band-structure calculations provide compelling evidence of strong nonlinear pressure dependence of the bandgap in both compounds. The nonlinear pressure dependence is well accounted for by the band anticrossing model that was previously established mostly for selenides with defect chalcopyrite structure. Therefore, our results on two sulfides with defect chalcopyrite structure under compressio…
Nonlinear Disorder Mapping via Wave Mixing in poled Lithium Tantalate
2010
We introduce and test a simple approach for the characterization of domain distribution in bulk quadratic ferroelectric crystals, specifically periodically poled Lithium Tantalate with random mark-to space ratio.
Nonlinear Disorder Mapping via Three Wave Mixing in Poled Lithium Tantalate
2010
We introduce and test a simple approach for the characterization of domain distribution in bulk quadratic ferroelectric crystals, such as periodically poled Lithium Tantalate with random mark-to space ratio.
Modeling non-linear dielectric susceptibilities of supercooled molecular liquids
2021
Advances in high-precision dielectric spectroscopy have enabled access to non-linear susceptibilities of polar molecular liquids. The observed non-monotonic behavior has been claimed to provide strong support for theories of dynamic arrest based on the thermodynamic amorphous order. Here, we approach this question from the perspective of dynamic facilitation, an alternative view focusing on emergent kinetic constraints underlying the dynamic arrest of a liquid approaching its glass transition. We derive explicit expressions for the frequency-dependent higher-order dielectric susceptibilities exhibiting a non-monotonic shape, the height of which increases as temperature is lowered. We demons…
Tunable coaxial cavity resonator for linear and nonlinear microwave characterization of superconducting wires
2011
We discuss experimental results obtained using a tunable cylindrical coaxial cavity constituted by an outer Cu cylinder and an inner Pb-BSCCO wire. We have used this device for investigating the microwave response of the superconducting wire, both in the linear and nonlinear regimes. In particular, by tuning the different modes of the cavity to make them resonant at exactly harmonic frequencies, we have detected the power emitted by the superconducting inner wire at the second- and third-harmonic frequency of the driving field. The results obtained in the nonlinear regime, whether for the microwave surface impedance or the harmonic emission, are qualitatively accounted for considering inter…
Three-Dimensional Printing of Nonlinear Optical Lenses.
2018
In the current paper, a series of nonlinear optical (NLO) active devices was prepared by utilizing stereolithographic three-dimensional printing technique. Microcrystalline NLO active component, urea, or potassium dihydrogen phosphate was dispersed in a simple photopolymerizable polyacrylate-based resin and used as the printing material to fabricate highly efficient transparent NLO lenses. The nonlinear activity of the printed lenses was confirmed by second-harmonic generation measurements using a femtosecond laser-pumped optical parametric amplifier operating at a wavelength of 1195 nm. The three-dimensional printing provides a simple method to utilize a range of NLO active compounds witho…
Harmonic emission at microwave frequencies in YBa2Cu3O7 single crystals near Tc
1998
Abstract Nonlinear microwave emission by YBa 2 Cu 3 O 7 single crystals is investigated at temperatures close to T c . Second- and third-harmonic signals are studied as a function of the temperature and input power, for different values of the external magnetic field. The results are discussed in the framework of a phenomenological theory based on the two-fluid model which assumes that both the microwave and static fields perturb the partial concentrations of the normal and condensate fluids. It is suggested that, at temperatures very close to T c , this mechanism is the only one responsible for the harmonic emission by YBa 2 Cu 3 O 7 single crystals in the Meissner state. It is also effect…
Characterization of Non-linear Inductors Including Thermal Effects for Power Applications
2018
This paper is focused on the behaviour of non-linear inductors employed in DC/DC switching converters considering the effects due to variations of both current and temperature. The characterization of the inductors is performed by a buck converter operated to stimulate the inductor under test by a constant current with superimposed a large signal. The measurements are carried out at several inductor’s temperature values. Data are automatically collected by a novel virtual instrument developed by the authors in LabVIEW® environment aiming to obtain a polynomial based analytical model. The deep knowledge of the inductor model allows its design to be optimized improving the power density of th…
Phonons in YBa2Cu3O7?x crystals with site-selective oxygen isotope substitution: Frequencies, normal vectors, non-linear properties
1995
Lattice vibrations of YBa2Cu3O7−x crystals with a site-selective isotope substitution18O→16O are investigated theoretically. It is shown that shifts of the frequencies of A1g oxygen vibrations due to this substitution are smaller than under complete one. However, phonon bands and normal vectors are changed much stronger, especially in the case when apical oxygens are substituted. On the basis of the presented analysis anharmonic properties and transition temperatures of the selectively substituted crystals are also briefly discussed.
On nonlinear behavior in brittle heterogeneous materials
2006
Abstract Many modern fiber-reinforced composite materials are ‘brittle’, in the sense that their strain to failure under quasi-static loading is typically of the order of 1% when loaded in directions generally controlled by fiber fracture, and the energy-to-failure under the quasi-static loading curve is typically small. For this reason, analysis of these materials is typically done under assumptions of linear elasticity, usually for homogeneous materials or material layers in a laminate. This is in contrast to ‘ductile’ metal behavior in which elastic–plastic behavior is widely discussed. What is most remarkable is the fact that for long-term behavior, the situation is nearly reversed in m…