Search results for "hysteresi"
showing 10 items of 250 documents
GA-based Off-Line Parameter Estimation of the Induction Motor Model Including Magnetic Saturation and Iron Losses
2020
This paper, starting from recent papers in the scientific literature dealing with Rotating Induction Motor (RIM) dynamic modelling, as a first step, improves its space-vector dynamic model, including both the magnetic saturation and iron losses; The main original aspects of the proposed model are the following: 1) the magnetic saturation of the iron core has been described on the basis of both current versus flux and flux versus current functions, 3) it includes the iron losses, separating them in hysteresis and eddy current ones, 4) it includes the effect of the load on the magnetic saturation. Afterwards, it proposes an off-line technique for the estimation of electrical parameters of thi…
Bidirectional photo-switching of the spin state of iron(II) ions in a triazol based spin crossover complex within the thermal hysteresis loop
2009
Abstract We have investigated the effect of short laser pulses (532 nm, 4 ns, −2 ) on the spin state of iron(II) ions in the spin crossover compound {[Fe II (Htrz) 2 (trz)](BF 4 )} within the hysteresis region of the high-spin (HS) to low-spin (LS) first-order thermal phase transition. Using Raman spectroscopy we have evidenced quasi-complete HS → LS as well as LS → HS photo-conversions, which can be induced by a single laser shot in the descending (351 K) and ascending (378 K) branches of the hysteresis loop, respectively. No effect has been observed, however, close to the center of the hysteresis loop even for repeated exposures.
On break-away forces in actuated motion systems with nonlinear friction
2017
The phenomenon of so-called break-away forces, as maximal actuation forces at which a sticking system begins to slide and thus passes over to a steady (macro) motion, is well known from engineering practice but still less understood in its cause-effect relationship. This note analyzes the break-away behavior of systems with nonlinear friction, which is analytically well-described by combining the Coulomb friction law with rate-independent presliding transitions and, when necessary, Stribeck effect of the velocity-weakening steady-state curve. The break-away conditions are harmonized with analytic form of the system description and shown to be in accord with a relationship between the varyin…
Complex Dynamics in a Harmonically Excited Lennard-Jones Oscillator: Microcantilever-Sample Interaction in Scanning Probe Microscopes1
1998
In this paper we model the microcantilever-sample interaction in an atomic force microscope (AFM) via a Lennard-Jones potential and consider the dynamical behavior of a harmonically forced system. Using nonlinear analysis techniques on attracting limit sets, we numerically verify the presence of chaotic invariant sets. The chaotic behavior appears to be generated via a cascade of period doubling, whose occurrence has been studied as a function of the system parameters. As expected, the chaotic attractors are obtained for values of parameters predicted by Melnikov theory. Moreover, the numerical analysis can be fruitfully employed to analyze the region of the parameter space where no theoret…
Pressure Tunable Electronic Bistability in Fe(II) Hofmann-like Two-Dimensional Coordination Polymer [Fe(Fpz)2Pt(CN)4]: A Comprehensive Experimental a…
2021
A comprehensive experimental and theoretical study of both thermal-induced spin transition (TIST) as a function of pressure and pressure-induced spin transition (PIST) at room temperature for the two-dimensional Hofmann-like SCO polymer [Fe(Fpz)2Pt(CN)4] is reported. The TIST studies at different fixed pressures have been carried out by magnetic susceptibility measurements, while PIST studies have been performed by means of powder X-ray diffraction, Raman, and visible spectroscopies. A combination of the theory of elastic interactions and numerical Monte Carlo simulations has been used for the analysis of the cooperative interactions in TIST and PIST studies. A complete (T, P) phase diagram…
Capillary pressure, hysteresis and residual saturation in porous media
2006
Abstract A macroscopic theory for capillarity in porous media is presented. The capillary pressure function in this theory is not an input parameter but an outcome. The theory is based on introducing the trapped or residual saturations as state variables. It allows to predict spatiotemporal changes in residual saturation. The theory yields process dependence and hysteresis in capillary pressure as its main result.
Influence of the Preparation Method on Planar Perovskite CH 3 NH 3 PbI 3-x Cl x Solar Cell Performance and Hysteresis
2017
The present research has been supported by the State Research Programme “LATENERGI” and National Research Programme “Multifunctional Materials and Composites, Photonics and Nanotechnology (IMIS2)”.
Rotor whirl damping by dry friction suspension systems
2008
An efficient and automatic attenuation technique for the whirling motion of rotating machinery can be achieved by supporting the journal boxes elastically and providing them with suitable rubbing surfaces subject to dry friction normal to the shaft axis. The critical flexural speeds are easily cut off and the whirl amplitude is minimized throughout the frequency range. Confining the usual operative angular speed of the rotor in the range of adhesive contact between the dry friction surfaces, there is no significant increase of power dissipation or heat production as a whole due to this type of suspension system, whose task is just to suppress the resonant peaks when passing the critical spe…
Non-Linear Hysteretic Instability in Rotating Machinery
2013
Uniaxial Pressure Effect on Electric Properties of PSN and 0.95PSN-0.05PLuN Ceramics
2006
The dielectric, pyroelectric and hysteresis loops measurements of PSN and 0.95PSN-0.05PLuN ceramics stress-free and under the stress (0–1.5 kbar) have been carried out. It was shown that axial pressure seems to change the partially ordered state to a disordered one, shifts the phase transformation and decreases the thermal hysteresis of the dielectric permittivity and the field-polarization hysteresis. These effects can be connected with change in domain structure, inter-ionic distances and defect density under the action of uniaxial pressure. The thermodynamic parameters of the phase transition were also determined.