Search results for "Hysteresi"
showing 10 items of 250 documents
A Novel Neural Approach to the Determination of the Distribution Function in Magnetic Preisach Systems
2004
This paper presents a novel method to identify both the functional dependence of the Preisach function as well as its numerical parameters on the basis of some known magnetic behavior. In this paper, the identification of the Preisach function of a material is performed by using a neural network trained by a collection of hysteresis curves, whose Preisach functions are known. When a new hysteresis curve is given as input to this neural network, it is able to give as output both the functional dependence of the Preisach function as well as its numerical parameters.
On the dependence of magnetic stochastic resonance features on the features of magnetic hysteresis
2005
Numerical study of magnetic stochastic resonance (SR) in several magnetic systems having different hysteresis loops was performed. The various hysteresis loops were modeled by using Preisach model in which several identification functions were used. The results showed the dependence of SR on the parameters of Preisach function. The results also showed how the field H/sub 0/ shifted the onset of SR and how a large dispersion of the distribution of hysterons degraded the SR.
Magnetic Stochastic Resonance in systems described by Dynamic Preisach Model
2008
Stochastic resonance (SR) is generally considered as an enhancement of the system response for certain finite values of the noise strength. In particular the signal to noise ratio (SNR) and the signal amplification show a maximum as a function of the noise intensity. This effect has been experimentally observed in many physical systems and also in magnetic systems. However, as far as magnetic systems are concerned, the dynamic features of the systems have been neglected and it has been assumed that the typical relaxation time is negligible. However this is clearly a rough approximation. In order to clarify this relation, in this paper we numerically study magnetic stochastic resonance in se…
Forming pressure dependence of the ferroelectric domain structure in green barium titanate pellets
1995
Abstract Modifications of the X-ray diffraction line profiles by die pressing of fine grained powders of barium titanate have been studied. Two main parameters have been considered: the forming pressure and the mechanical characteristics of the binder. The higher the forming pressure, the greater the modifications of the line profiles. Furthermore, the phenomena seems to be related to pressing only; no significant effect related to the nature of the binder has been shown. The modifications of the diffraction line profiles are interpreted by considering a reduction of the size of the ferroelectric domains during pressing. In order to confirm this interpretation, the behaviour of the domain s…
Comparison of unconfined and confined unsaturated hydraulic conductivity
2007
Abstract The field tension infiltrometer (TI) and the laboratory unit hydraulic gradient (UHG) methods are widely applied to determine the near-saturated soil hydraulic conductivity, K . Comparison between the two methods is relevant given that they differ in the explored soil volume (undetached or detached) and in the flow process (unconfined or confined). The objective of this investigation was to compare unconfined and confined measurements of unsaturated hydraulic conductivity. Twenty TI experiments were conducted in a relatively coarse-textured soil having an appreciable hysteretic behavior by using two different dry-to-wet-to-dry (DTWTD) sequences of pressure head, h 0 , values that d…
Pressure-tuning of magnetism and linkage isomerism in iron(II) hexacyanochromate.
2005
A pressure-induced linkage isomerization of the cyanide anion has been observed in single crystals of a chromium(III)-iron(II) Prussian blue analogue of formula K0.4Fe4[Cr(CN)6]2.8 square1.2.16H2O (1). Upon application of pressure in the 0-1200 MPa range, the cyanide ligand rotates and becomes C-bonded to the iron(II) cations, leading to a stabilization of their diamagnetic low-spin states. The result is a decrease of magnetization and magnetic ordering temperatures from TC = 19 K at ambient pressure to 13 K at 1200 MPa. The initial magnetic properties can be restored on pressure release. The reversible movement of cyanide in the solid state can be exploited as a switch of the magnetic inte…
Mechanostructural adaptations preceding postpneumonectomy lung growth
2012
In many species, pneumonectomy results in compensatory growth in the remaining lung. Although the late mechanical consequences of murine pneumonectomy are known, little is known about the anatomic adaptations and respiratory mechanics during compensatory lung growth. To investigate the structural and mechanical changes during compensatory growth, mice were studied for 21 days after left pneumonectomy using microCT and respiratory system impedance (FlexiVent). Anatomic changes after left pneumonectomy included minimal mediastinal shift or chestwall remodeling, but significant displacement of the heart and cardiac lobe. Mean displacement of the cardiac lobe centroid was 5.2 ± 0.8 mm. Lung imp…
Bistable spin-crossover nanoparticles showing magnetic thermal hysteresis near room temperature
2007
We have demonstrated that the reverse micelle technique can be applied to polymeric spin-crossover systems, such as [Fe(Htrz)2(trz)](BF4), to control the growth of the crystallites. Small nanoparticles of diameters around 10 nm and narrow size distribution were obtained. It is easy to envision that, by modifying the synthetic procedure, the size and critical temperatures of these nanoparticles can be tuned. On one hand, different ratios of solvent, water, and surfactants will lead to different micelle sizes, which will affect the particle size and, maybe, the magnetic properties. On the other hand, the critical temperatures can be lowered towards room temperature by changing the composition…
Spin crossover behavior under pressure of Fe(PM-L)2(NCS)2 compounds with substituted 2′-pyridylmethylene 4-anilino ligands
1998
Abstract New iron(II) spin crossover systems with large aromatic ligands, based on 2′-pyridylmethylene 4-anilino units, have been synthesized and studied. The whole range of spin crossover behavior has been observed, starting from pure high-spin to more or less complete gradual transitions and finally to discontinuous type transitions with both small and large hysteresis. Magnetic measurements under pressure have revealed that two of the compounds exhibit pressure-induced new phases with larger hysteresis than at atmospheric pressure. For one of the compounds the formation of this new phase is irreversible and the hysteresis width is ∼100 K, as compared to 37 K before applying pressure.
Room temperature hysteretic spin crossover in a new cyanoheterometallic framework.
2019
A new iron(II)-based spin-crossover compound with thermal hysteresis operating under ambient conditions is reported. This complex exhibits a high reproducibility of the spin transition in many successive thermal cycles, stability of both spin states at room temperature and an attractive operational temperature range.