Search results for "Magneto"
showing 10 items of 919 documents
Electron scattering mechanisms inn-type indium selenide
1984
Electron scattering mechanisms in $n$-type indium selenide are investigated by means of the temperature dependence (4-500 K) of Hall mobility and the magnetic field dependence of Hall and magnetoresistance coefficients. The Schmid model for homopolar optical-phonon scattering can explain the temperature dependence of electron mobility above 40 K. The electron-phonon coupling constant is determined, ${g}^{2}=0.054$. The optical phonon involved in the process is identified as the ${A}_{1}^{\ensuremath{'}}$ phonon with energy 14.3 meV. The magnetic field dependence of Hall and magnetoresistance coefficients is discussed in terms of the Jones-Zener expansion.
Optical and magneto‐optical studies of Mn‐activated LiBaF 3
2005
The photoluminescence (PL) of Mn-doped LiBaF3 shows a weak Mn2+ emission band at 710 nm; the corresponding excitation bands are between 210 and 620 nm. After X-irradiation the PL spectrum shows two new bands peaking at 600 and 670 nm that are tentatively assigned to perturbed Mn2+ emissions; the intensity of all PL bands is increased. Magnetic circular dichroism (MCD) and the MCD-detected electron paramagnetic resonance (EPR) measurements show that F-type centres are formed after X-irradiation. The EPR measurements indicate that there is a spatial correlation between the F-type centre and the Mn2+ dopant. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced models for smart multilayered plates based on Reissner Mixed Variational Theorem
2017
In the present work, families of equivalent singe layer and layer-wise models for the static and free vibrations analysis of magneto-electro-elastic multilayered plates are developed. The models are defined in the framework of a unified formulation, which offers a systematic approach for generating refined plate theories through suitable expansions of the through-the-thickness components of the relevant fields, considering the expansion order as a free parameter. The key features of the developed formulation are: a) the condensation of the electric and magnetic description into the mechanical representation, based on the quasi-static electric-magnetic approximation, which allows to reduce t…
Semiactive Control Methodologies for Suspension Control With Magnetorheological Dampers
2012
Authors version of an article published in the journal: IEEE/ASME Transactions on Mechatronics. Also available from the publisher at: http://dx.doi.org/10.1109/TMECH.2011.2107331 Suspension systems are one of the most critical components of transportation vehicles. They are designed to provide comfort to the passengers to protect the chassis and the freight. Suspension systems are normally provided with dampers that mitigate these harmful and uncomfortable vibrations. In this paper, we explore two control methodologies (in time and frequency domain) used to design semiactive controllers for suspension systems that make use of magnetorheological dampers. These dampers are known because of th…
Heuristic and Backstepping Control Strategies for Semiactive Suspension in Automotive Systems Equipped with MR Dampers
2010
Abstract This paper deals with the problem of semiactive vibration reduction in a class of automotive systems. Most conventional suspensions use passive devices to absorb impacts and vibrations, which is generally difficult to adapt to the uncertain circumstances. Semiactive suspension techniques promise a solution to the above problem with some comparatively better features than active and passive suspension devices. In this work, the semiactive suspension with magnetorheological (MR) dampers is applied for the vibration attenuation. Both backstepping and heuristic control strategies are proposed. In the design of backstepping controller, the Dahl model of the MR damper is used to estimate…
Mathematical Model of a PM Brushless Motor with Different Stator-Rotor Pole Pairs Number
2013
The paper presents a mathematical model of Permanent Magnet AC brushless machines (PMSM) having a number of stator poles-obtained via the distribution of the three-phase winding- different from the rotor one, realized by the displacement of the permanent magnets. For these so- called ‘Fractional-Slot’ motors (where few total slots generate high equivalent number of poles) the available mathematical models appear partial and/or incomplete, despite of numerous designing considerations made in literature. In this paper an analytical approach is developed to point out an instantaneous- values mathematical model with concentrated parameters, that can be suitable for control architecture systems …
Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing
2009
The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among o…
A mixed H<inf>2</inf>/H<inf>&#x221E;</inf>-based semiactive control for vibration mitigation in flexible structures
2009
In this paper, we address this problem through the design of a semiactive controller based on the mixed H 2 /H ∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H 2 /H ∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evalu…
Thermo acoustic - MHD electrical Generator
2011
Abstract The thermo-acoustic generators offer a unique means of converting thermal energy into mechanical energy without any moving parts and without fluid circulation. They are comparable to the Stirling engine with the advantage of much greater simplicity. They are therefore natural candidates for special uses where interventions are limited. The problem to solve is transforming the mechanical energy into electrical energy. MHD generators offer excellent opportunities in this area, particularly by using the mechanisms of induction. The work concerns the combination of a thermo-acoustic generator with an induction generator of a new concept for obtaining electric current with adjustable vo…
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…