Search results for " hysteresis"
showing 10 items of 98 documents
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.
Structure and physical properties of [mu-tris(1,4-bis(tetrazol-1-yl)butane-N4,N4 ')iron(II)] bis(hexafluorophosphate), a new Fe(II) spin-crossover co…
2004
[mu-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF6)(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T-1/2 = 174 K and a hysteresis of about 4 K between T-1/2 and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, Fe-57-Mossbauer spectroscopy, and variable temperature far and midrange FIR spectroscopy. The title compound crystallizes in the trigonal space group P (3) over bar (No. 147) with a unit cell content of one formula u…
Tunable crossover between one- and three-dimensional magnetic dynamics inCoIIsingle-chain magnets organized by halogen bonding
2016
Low-temperature magnetometry, ac susceptibility, and calorimetry have been employed to study Co-based single-chain magnets (SCMs) organized through halogen bonding. Magnetic hysteresis and maxima in the dc and ac susceptibilities, respectively, confirm the SCM behavior of the system. Several characteristic magnetic relaxation regimes are observed at different temperatures, which can be associated with both intra- and interchain exchange interactions. Remarkably, tweaking the rate at which an external magnetic field is swept along the axis of the chains enables a controlled transition between the one- and three-dimensional dynamics. Experiments on an isostructural Co-based SCM system crystal…
Identification of parameters of the Jiles-Atherton model by neural networks
2011
In this paper a procedure for the identification of the parameters of the Jiles–Atherton (JA) model is presented. The parameters of the JA model of a material are found by using a neural network trained by a collection of hysteresis curves, whose parameters are known. After a presentation of the Jiles–Atherton model, the neural network and the training procedure are described and the method is validated by using some numerical, as well as experimental, data.
Pressure Effect Studies on the Spin‐Transition Behavior of a Dinuclear Iron(II) Compound
2013
Magnetic studies into the effect of different hydrostatic pressures between ambient and 1.03 GPa on the high-spin (HS) i low-spin (LS) transition behavior of the dinuclear iron(II) compound [Fe II 2(PMAT)2](BF4)4·DMF (1, PMAT = 4-amino3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, DMF = N,N-dimethylformamide) have been carried out at 2– 300 K. Under ambient pressure, the sample studied exhibits a [HS–HS] to [HS–LS] half spin transition (ST) at T½ = 208 K without any thermal hysteresis. Increasing the pressure above 0.2 GPa causes an increase (initially rapid but above 0.5 GPa more gradual) of T½ as well as a matching reduction in the residual high-spin fraction at room temperatu…
The Effect of Pressure on the Cooperative Spin Transition in the 2D Coordination Polymer {Fe(phpy) 2 [Ni(CN) 4 ]}
2013
The effect of pressure on the spin-transition properties of the 2D coordination polymer {Fe(phpy)2[Ni(CN)4]} is reported. The study has been carried out by means of variable-temperature (10–310 K) magnetic susceptibility measurements at applied pressures of 105 Pa to 1.0 GPa and spectroscopic studies in the visible region at room temperature (105 Pa–3.0 GPa). As the pressure is increased, the characteristic temperature of the spin transition is displaced to higher temperatures and the thermal hysteresis loop disappears. A cooperative first-order spin transition characterized by a piezo-hysteresis loop about 0.3 GPa wide was observed at 293 K.
Tonographic Effect of Ocular Response Analyzer in Comparison to Goldmann Applanation Tonometry.
2016
AIMS The tonographic effect is a phenomenon of intraocular pressure (IOP) reduction following repeated tonometry. This study examines whether the tonographic effect occurs following IOP measurement performed with Ocular Response Analyzer (ORA). METHODS Both eyes of 31 glaucoma patients and 35 healthy controls underwent nine IOP-measurements performed with GAT and ORA. The number of GAT and ORA measurements performed on each eye differed depending on the randomly allocated investigation scheme. Central corneal thickness (CCT), anterior chamber volume (ACV) and anterior chamber depth (ACD) were assessed with Pentacam before and after the repeated GAT/ORA measurements. RESULTS There was no sta…
Corneal Biomechanical Parameters and Central Corneal Thickness in Glaucoma Patients, Glaucoma Suspects, and a Healthy Population
2021
Purpose: To evaluate and compare corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT), measurements were taken between a healthy population (controls), patients diagnosed with glaucoma (DG), and glaucoma suspect patients due to ocular hypertension (OHT), family history of glaucoma (FHG), or glaucoma-like optic discs (GLD). Additionally, Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) were compared between the different groups of patients. Methods: In this prospective analytical-observational study, a total of 1065 patients (one eye of each) were recruited to undergo Ocular Response Analyzer (ORA) testing, ultrasoun…
Are Ocular Response Analyzer useful to measure corneal hysteresis in patients with intracorneal rings?
2008
Purpose Corneal hysteresis is a viscoelastic property characterized by the difference in behavior under loading and unloading. The aim of the study was to determine corneal hysteresis in different eyes: healthy eyes, keratoconic eyes and keratoconic eyes after intracorneal ring implants. Methods This study comprised 95 eyes of 59 patients. The study population was divided into 3 groups. We analyze 30 healthy human eyes, 35 keratoconic eyes (Amsler grade II-III) and 30 keratoconic eyes after intracorneal rings implantation. Corneal biomechanical properties of these eyes were measured with the Ocular Response Analyser (ORA-Reichert) according to two parameters: corneal hysteresis (CH) and cor…