Search results for "HYSTERESIS"
showing 10 items of 245 documents
Colossal barocaloric effects in the complex hydride Li$_{2}$B$_{12}$H$_{12}$
2021
Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($|\Delta T| \sim 1$ K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of $|\Delta S| \sim 100$ JK$^{-1}…
Hysteresis vs. natural rate of unemployment: new evidence for OECD countries
2004
Abstract The paper tests hysteresis effects in unemployment using panel data for 19 OECD countries. We apply a sequential procedure based in two multivariate augmented Dickey-Fuller test (ADF)-type panel unit root tests in a SURE framework. We strongly reject the joint null of hysteresis and find that only seven countries present evidence of hysteresis.
Dynamic Preisach Hysteresis Model for Magnetostrictive Materials for Energy Application
2013
In this paper the magnetostrictive material considered is Terfenol-D. Its hysteresis is modeled by applying the DPM whose identification procedure is performed by using a neural network procedure previously publised [. The neural network used is a multiplayer perceptron trained with the Levenberg-Marquadt training algorithm. This allows to obtain the Preisach distribution function, without any special conditioning of the measured data, owing to the filtering capabilities of the neural network interpolators. The model is able to reconstruct both the magnetization relation and the Field-strain relation. The model is validated through comparison and prediction of data collected from a typical …
Nonlinear analysis of cylindrical and conical hysteretic whirl motions in rotor-dynamics
2014
Abstract The internal friction of a rotor–shaft-support system is mainly due to the shaft structural hysteresis and to some possible shrink-fit release of the assembly. The experimentation points out the destabilizing effect of the internal friction in the over-critical rotor running. Nevertheless, this detrimental influence may be efficiently counterbalanced by other external dissipative sources located in the supports or by a proper anisotropic configuration of the support stiffness. The present analysis considers a rotor–shaft system which is symmetric with respect to the mid-span and is constrained by viscous-flexible supports with different stiffness on two orthogonal planes. The cylin…
The Jiles Atherton Model for Description Of Hysteresis in Lithium Battery
2013
In this paper Jiles Atherton (JA) Model is used to obtain a mathematical model of the hysteresis in lithium battery. JA Model allows to describe both the hysteresis and the dynamical features of charging and discharging cycles in a lithium battery. The identification of the model is obtained by using a neural network technique developed for magnetic systems. The model is validated on some experimental tests on commercial batteries.
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…
Real-time 3D imaging of Haines jumps in porous media flow.
2013
Newly developed high-speed, synchrotron-based X-ray computed microtomography enabled us to directly image pore-scale displacement events in porous rock in real time. Common approaches to modeling macroscopic fluid behavior are phenomenological, have many shortcomings, and lack consistent links to elementary pore-scale displacement processes, such as Haines jumps and snap-off. Unlike the common singular pore jump paradigm based on observations of restricted artificial capillaries, we found that Haines jumps typically cascade through 10–20 geometrically defined pores per event, accounting for 64% of the energy dissipation. Real-time imaging provided a more detailed fundamental understanding o…
Measuring low H field and currents with AMR sensors
2017
The growing demand from the automotive industry for high accuracy magnetic sensors and the need to perform high resolution angular position measurements have been the drivers for the industrial research in magnetic sensing technologies. This paper describes the design and characterization of several experimental devices implementing simple magnetoresistive structures targeting contactless current measurement in the tens to hundreds of milliamps range with sub-mA resolution. The ultimate goal is to extend the application area of magnetoresistive sensors beyond their current niche in automotive into more general applications. The initial set of devices tested to-date has shown a sensitivity o…
Stability analysis of rotor whirl under nonlinear internal friction by a general averaging approach
2016
The two main sources of internal friction in a rotor-shaft system are the shaft structural hysteresis and the possible shrink-fit release of the assembly. The internal friction tends to destabilize the over-critical rotor running, but a remedy against this effect may be provided by a proper combination of some external damping in the supports and an anisotropic arrangement of the support stiffness, or at most by the support damping alone, depending on the system geometry. The present analysis reported here considers a general asymmetric rotor-shaft system, where the rotor is perfectly rigid and is constrained by viscous–flexible supports having different stiffnesses on two orthogonal plane…
Effect of nanostructuration on the spin crossover transition in crystalline ultrathin films† †Electronic supplementary information (ESI) available: M…
2019
Film thickness and microstructure critically affect the spin crossover transition of a 2D coordination polymer.