Search results for "HYSTERESIS"
showing 10 items of 245 documents
Discrete-Time Adaptive Hysteresis Filter for Parallel Computing and Recursive Identification of Preisach Model
2018
High-precision motion control systems, for instance deployed for micro- and nano-positioning, often use the smart-material based actuators such as piezoelectric and magnetostrictive stages. Those exhibit inherent hysteresis nonlinearities which are challenging to compensate without precise hysteresis modeling. Even if a suitable hysteresis modeling approach is available, its parameter identification, correspondingly adaptation, at normal operating conditions constitute an essential task for the overall control design. This paper uses the direct recursive identification method for the Preisach hysteresis model and describes the fast parallel-computing discrete-time algorithm for an adaptive …
Properties of Co/sub 2/YZ Heusler compounds
2005
Heusler compounds of Co/sub 2/XY composition (Co/sub 2/Cr/sub 0.6/Fe/sub 0.4/Al, Co/sub 2/FeSi) offer a variety of half-metallic ferromagnetic materials. These were prepared by arc melting and comprehensively characterized by means of X-ray diffraction ( XRD), Mossbauer spectroscopy, magnetic X-ray circular dichroism spectroscopy (MXCD), superconducting quantum interference device (SQUID) magnetometry, electron spectroscopy for chemical analysis (ESCA), extended X-ray absorption fine structure (EXAFS) and Auger electron spectroscopy (AES) depth profiling. Structural disorder phenomena, magnetic hysteresis, magnetic moments, magnetic transition temperatures and Curie temperature were obtaine…
Temperature-dependent phase transitions in water-oil-surfactant mixtures: Experiment and theory
1996
We investigate temperature induced phase transitions in mixtures of water, oil, and a nonionic surfactant. By microcalorimetric measurements it is shown that the droplet-lamellar transition shows hysteresis so that it is strongly first order. The position of this transition and of the emulsification boundary are quantitatively described by an interfacial model which considers solely the temperature dependence of the spontaneous curvature. There is no fit parameter in the model. Remarkably, the positions of both boundaries do not depend on the bending moduli. \textcopyright{} 1996 The American Physical Society.
Temperature and pressure effects on the spin state of ferric ions in the [Fe(sal2-trien)][Ni(dmit)2] spin crossover complex
2008
Abstract Thermal and pressure effects have been investigated on the [Fe(sal 2 -trien)][Ni(dmit) 2 ] spin crossover complex by means of Mossbauer spectroscopic, calorimetric, X-ray diffraction and magnetic susceptibility measurements. The complex displays a complete thermal spin transition between the S = 5 2 and S = 1 2 spin states of Fe III near 245 K with a hysteresis loop of ca. 30 K. This transition is characterised by a change of the enthalpy, Δ H HL =7 kJ/mol, entropy, Δ S HL =29 J/Kmol, and the unit cell volume, Δ V HL =15.4 A 3 . Under hydrostatic pressures up to 5.7 kbar the thermal transition shifts to higher temperatures by ca. 16 K/kbar. Interestingly, at a low applied pressure …
mplicit Identification of Contact Parameters in a Continuous Chain Model
2011
Accurate contact modeling is of great importance in the field of dynamic chain simulations. In this paper emphasis is on contact dynamics for a time-domain simulation model of large chains guided in a closed loop track. The chain model is based on theory for unconstrained rigid multibody dynamics where contact within the chain and with the track is defined through continuous point contacts using the contact indentation and rate as means. This paper presents an implicit method to determine contact parameters of the chain model through the use of none gradient optimization methods. The set of model parameters are estimated by minimizing the residual between simulated and measured results. The…
Cyanide-bridged Fe(III)–Co(II) bis double zigzag chains with a slow relaxation of the magnetisation
2003
Reaction of [FeIII(bipy)(CN)4]¯ with fully solvated MII cations [M = Co (1) and Mn (2)] produces the isostructural bis double zigzag chains [[FeIII(bipy)(CN)4]2MII(H2O)]·MeCN·1/2H2O; 1 exhibits intrachain ferromagnetic and interchain antiferromagnetic couplings, slow magnetic relaxation and hysteresis effects. Luminita Marilena, Toma, Luminita.Toma@uv.es ; Lescouezec, Alain Francois Rodri, Alain.Lescouezec@uv.es ; Lloret Pastor, Francisco, Francisco.Lloret@uv.es ; Julve Olcina, Miguel, Miguel.Julve@uv.es
Slow Magnetic Relaxation in a Co (II)–Y (III) Single‐Ion Magnet with Positive Axial Zero‐Field Splitting
2013
This work was supported by the MINECO (Spain) (Project CTQ2011-24478), the Junta de Andalucía (FQM-195 and Project of excellence P08-FQM-03705), and the University of Granada. E.R. and E.Cr. thank MINECO grant No. CTQ2011-23862-C02-01 and Generalitat de Catalunya grant No. 2009SGR-1459, for financial support. We would like to thank Prof. Liviu Chibotaru for providing us the SINGLE_ANISO program and Dr. Andrew Ozarowski for the EPR simulation software. E.K.B. thanks the EPSRC and Leverhulme Trust for financial support. The NHMFL is funded by the NSF, DoE, and the state of Florida. J.C. acknowledges financial support by the Spanish Ministerio de Ciencia e Innovación through projects CTQ2010-1…
Design of single chain magnets through cyanide-bearing six-coordinate complexes
2005
Abstract The design and preparation of stable cyanide-bearing six-coordinate complexes of formula [MIII(L)(CN)x](x + l − m)− (M = trivalent transition metal ion and L = polydentate blocking ligand) are summarized here. Their use as ligands towards either fully hydrated metal ions or coordinatively unsaturated preformed species, to afford a wide variety of low-dimensional metal assemblies whose nuclearity, dimensionality and magnetic properties can be tuned, is also reviewed. Special emphasis is put on the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors. Among the different new spin topologies obtain…
Pressure-induced transition in titanium metal: a systematic study of the effects of uniaxial stress
2005
Abstract The effects of uniaxial stress on the pressure-induced α → ω transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa (argon pressure medium); (2) the α and ω phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the ω phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the α → ω transi…
High-pressure vibrational and optical study of Bi2Te3
2011
We report an experimental and theoretical lattice dynamics study of bismuth telluride (Bi2Te 3 )u p to 23 GPa together with an experimental and theoretical study of the optical absorption and reflection up to 10 GPa. The indirect bandgap of the low-pressure rhombohedral (R-3m) phase (α-Bi2Te 3) was observed to decrease with pressure at a rate of − 6m eV/GPa. In regard to lattice dynamics, Raman-active modes of α-Bi2Te 3 were observed up to 7.4 GPa. The pressure dependence of their frequency and width provides evidence of the presence of an electronic-topological transition around 4.0 GPa. Above 7.4 GPa a phase transition is detected to the C2/m structure. On further increasing pressure two …