Search results for "Harmonic"
showing 10 items of 984 documents
Identification of parameters and harmonic losses of a deep-bar induction motor
2017
High frequency harmonics from a frequency converter causes additional losses in a deep-bar induction motor. The harmonics have their own amplitude and phase with respect to the fundamental signal, but the harmonic loss is only dependent on the amplitude of harmonics. A deep-bar induction motor can be modelled by a triple-cage circuit to take skin effect into account. The triple cage circuit having many parameters could be estimated from a small-signal model of the machine by using Differential Evolution. The correctly estimated parameters make the triple-cage circuit valid in a wide range of frequencies. However, the triple-cage circuit is very complicated which makes it difficult to model …
Current induced chiral domain wall motion in CuIr/CoFeB/MgO thin films with strong higher order spin–orbit torques
2020
We investigate the Dzyaloshinskii–Moriya interaction (DMI) and spin–orbit torque effects in CuIr/CoFeB/MgO heterostructures. To this end, harmonic Hall measurements and current induced domain wall motion experiments are performed. The motion of domain walls at zero applied field due to current demonstrates the presence of DMI in this system. We determine the strength of the DMI to be D = + 5 ± 3 μ J / m 2 and deduce right-handed chirality in domain walls showing a partial Neel type spin structure. To ascertain the torques, we perform a second harmonic measurement to quantify the damping- and field-like current induced effective fields as a function of the magnetization direction. From the a…
The Effect of the Harmonic Content Generated by AC/DC Modular Multilevel Converters on HVDC Cable Systems
2019
With the increasing penetration of renewable and decentralized energy sources into the power grid, an extended use of DC voltages is expected on both distribution and transmission levels. Generation of DC voltages by means of voltage source converters is associated with a wide spectrum of harmonic distortions at converter terminals, both on the ac and on the dc sides. This can lead to partial discharges in power cables, which deteriorate insulation material thus weakening its performance and reducing cable life-time. In the previously published paper, the effect of harmonic distortion on appearance of partial discharges in cable insulation was evaluated. Here, the study related to the PD be…
On the ‘expanded local mode’ approach applied to the methane molecule: isotopic substitution CH2D2←CH4
2011
On the basis of a compilation of the ‘expanded local mode’ model and the general isotopic substitution theory, sets of simple analytical relations between different spectroscopic parameters (harmonic frequencies, ωλ, anharmonic coefficients, x λμ, ro-vibrational coefficients, , different kinds of Fermi- and Coriolis-type interaction parameters) of the CH2D2 molecule are derived. All of them are expressed as simple functions of a few initial spectroscopic parameters of the mother, CH4, molecule. Test calculations with the derived isotopic relations show that, in spite of a total absence of initial information about the CH2D2 species, the numerical results of the calculations have a very good…
Theoretical investigation of the potential energy surface of the van der Waals complex CH4-N-2
2009
International audience; The interaction potential energy surface of the van der Waals CH4-N-2 complex has been calculated for a broad range of intermolecular separations and configurations in the approximation of rigid interacting molecules at the CCSD(T) and MP2 levels of theory using the correlation consistent aug-cc-pVTZ basis set. The BSSE correction was taken into account for all the calculations. The most stable configurations of the complex were found. Binding energies were calculated in the CBS limit with accounting for the molecular deformations. The harmonic and anharmonic fundamental vibrational frequencies and rotational constants for the ground and first excited vibrational sta…
Laser control in open molecular systems: STIRAP and Optimal Control
2007
We examine the effect of dissipation on the laser control of a process that transforms a state into a superposed state. We consider a two-dimensional double well of a single potential energy surface. In the context of reactivity, the objective of the control is the localization in a given well, for instance the creation of an enantiomeric form whereas for quantum gates, this control corresponds to one of the transformation of the Hadamard gate. The environment is either modelled by coupling few harmonic oscillators (up to five) to the system or by an effective interaction with an Ohmic bath. In the discrete case, dynamics is carried out exactly by using the coupled harmonic adiabatic channe…
Inelastic neutron scattering study of proton dynamics in Ca(OH)2 at 20 K
1995
Abstract Inelastic neutron scattering (INS) spectra of Ca(OH) 2 at 20 K are presented from 30 to 4000 cm −1 for a powder sample, from 30 to 12000 cm −1 for an oriented single-crystal. INS band splitting due to the lattice density-of-states is observed. Polarization effects reveal the orientation of atomic displacements for each mode and a new band assignment scheme is proposed. For the single-crystal, the v OH mode and overtones are observed. This oscillator shows only moderate anharmonicity. Spectrum simulation reveals that INS spectral intensities are not consistent with simple normal coordinates and harmonic force-fields for Ca(OH) 2 entities. A new dynamical model is proposed, including…
Harmonic morphisms in nonlinear potential theory
1992
This article concerns the following problem: given a family of partial differential operators with similar structure and given a continuous mapping f from an open set Ω in Rn into Rn, then when does f pull back the solutions of one equation in the family to solutions of another equation in that family? This problem is typical in the theory of differential equations when one wants to use a coordinate change to study solutions in a different environment.
SEA LEVEL VARIATIONS AT THE LATVIAN COASTAL HYDROLOGIC STATIONS
2016
The objective of this paper is to analyse water level variations of the Baltic Sea on the Latvian coast. This is important because the Baltic Sea exhibits a number of remarkable phenomena. One of them is the sea level variations due to winds, complicated by the shape of the gulfs and islands. Under this influence the range of the sea level variations can reach 3 m on the coasts of gulfs. However, the tidal variations of the Baltic Sea range in the order of centimetres only. In the frame of this study, using hourly time series of the sea level records from 7 Latvian coastal hydrologic stations and employing spectral analysis, it has become feasible to identify diurnal and semi-diurnal tide e…
Rocking of rigid block on nonlinear flexible foundation
2017
Abstract The two prime models used currently to describe rocking of rigid bodies, the Housner’s model and the Winkler foundation model, can capture some of the salient features of the physics of this important problem. These two models involve either null or linear interaction between the block and the foundation. Hopefully, some additional aspects of the problem can be captured by an enhanced nonlinear model for the base-foundation interaction. In this regard, what it is adopted in this paper is the Hunt and Crossley’s nonlinear impact force model in which the impact/contact force is represented by springs in parallel with nonlinear dampers. In this regard, a proper mathematical formulatio…