Series Of Hysteresis Loops Research Articles

Fatigue life analysis of monopile-supported offshore wind turbines based on hyperplastic ratcheting model

Fatigue life is an important factor to be considered in foundation design of offshore wind turbines (OWTs), and accurate prediction of fatigue damage is dependent on an appropriate foundation model. Currently, the rigid foundation is widely used to model the monopile foundation in most aero-hydro-servo-elastic simulation tools, and soil stiffness and damping are not considered. This will lead to an inaccurate estimation of fatigue damage of monopile-supported OWTs. Given this limitation, hyperplastic ratcheting model is incorporated into FAST v7, the variations of stiffness, damping and accumulated displacement for monopile-supported OWTs subjected to cyclic loadings are well considered. The validity of the implementation is demonstrated by presentation of non-linear soil resistance-displacement curves, and a series of hysteresis loops can be observed. Based on this integrated tool, extensive simulations and analyses for monopile-supported OWTs under different environmental states are performed. Furthermore, the effect of pile-soil interaction on fatigue life of monopile is quantified. The aim of this paper is to provide an accurate model to estimate fatigue life of monopile-supported OWTs.

Rotation of exciton-polariton condensates with TE-TM splitting in a microcavity ring

We investigate exciton-polariton condensates with a rotating potential induced by an electric field in a semiconductor microcavity ring. In the absence of transverse-electric-transverse-magnetic (TE-TM) splitting, we find that there is a critical laser pump rate, above which the quantized phase slips appear with hysteresis, and there exist quantized average angular momenta at fixed angular velocities, regardless of the pump rate. When considering the TE-TM splitting, we find that there are a series of hysteresis loops with the same intervals which are modulated by the magnitude of the splitting for a linear polarization laser. Further, multistability occurs at large pump rate, and there arises a phase slip for only one spin with large absolute value of the polarization degree, owing to the competition of the TE-TM splitting and energy induced by rotation. These results can be verified experimentally with current technology, and are useful for future electro-optic devices.

Effective field study of ising model on a double perovskite structure

By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one.

Modeling and characterization of hysteresis loops with Preisach hysteron weight modification

ABSTRACTPreisach-based method was used to characterize a series of BaTiO3 hysteresis loops with varying external field frequencies. A stochastic adjustment of hysterons' weight was performed to obtain the Preisach densities. These densities, in representing the hysteresis responses, were characterized with three key parameters of the 3-dimensional hyperbolic-like distribution. One of the parameters relates directly to coercivity, while the other two concurrently represent polarization derivatives close to the coercivity, and emphasize an adaptability of the material to the external field around the main body of the loops. Thus, this approach can be extended to characterize other series of hysteresis loops to study changes of material responses influenced by varying external field frequency factor.

GRACE storage-runoff hystereses reveal the dynamics of regional watersheds

Abstract. We characterize how regional watersheds function as simple, dynamic systems through a series of hysteresis loops using measurements from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. These loops illustrate the temporal relationship between runoff and terrestrial water storage in three regional-scale watersheds (> 150 000 km2) of the Columbia River Basin, USA and Canada. The shape and size of the hysteresis loops are controlled by the climate, topography, and geology of the watershed. The direction of the hystereses for the GRACE signals moves in opposite directions from the isolated groundwater hystereses. The subsurface water (soil moisture and groundwater) hystereses more closely resemble the storage-runoff relationship of a soil matrix. While the physical processes underlying these hystereses are inherently complex, the vertical integration of terrestrial water in the GRACE signal encapsulates the processes that govern the non-linear function of regional-scale watersheds. We use this process-based understanding to test how GRACE data can be applied prognostically to predict seasonal runoff (mean Nash-Sutcliffe Efficiency of 0.91) and monthly runoff during the low flow/high demand month of August (mean Nash-Sutcliffe Efficiency of 0.77) in all three watersheds. The global nature of GRACE data allows this same methodology to be applied in other regional-scale studies, and could be particularly useful in regions with minimal data and in trans-boundary watersheds.

Coupling strength with off-axial external field in magnetic tunnel junction cells

A series of hysteresis loops with off-axial external magnetic fields have been measured to identify magnetization reversal properties as well as coupling effects in magnetic tunnel junctions (MTJs). MTJ films, consisting of a synthetic artificial antiferromagnetic pinned layer of CoFeB/Ru/CoFe/IrMn, were patterned into an elliptical cell array with sizes of 200 × 300 nm and 500 × 750 nm. The hysteresis loops were measured using a vibrating sample magnetometer with various directions of the external magnetic field; the angle θ between the external magnetic field (H→E) and the biasing field of the pinned layer (H→B) was varied from 0° to 90°. The two significant coupling effects, ascribed to exchange bias between CoFe/IrMn and Ruderman–Kittel–Kasuya–Yosida–like coupling in CoFeB/Ru/CoFe, can be observed in these hysteresis loops. The angular dependence of the hysteresis loops is employed to characterize the variation of these coupling effects in extended and patterned MTJ films.

Reversible and irreversible unfolding of mitotic newt chromosomes by applied force.

The force-extension behavior of individual mitotic newt chromosomes was studied, using micropipette surgery and manipulation, for elongations up to 80 times native length. After elongations up to five times, chromosomes return to their native length. In this regime chromosomes have linear elasticity, requiring approximately 1 nN of force to be stretched to two times native length. After more than five times stretching, chromosomes are permanently elongated, with force hysteresis during relaxation. If a chromosome is repeatedly stretched to approximately 10 times native length and relaxed, a series of hysteresis loops are obtained that converge to a single reversible elastic response. For further elongations, the linear dependence of force on extension terminates at a force "plateau" of approximately 15-20 nN, near 30 times extension. After >30 times extensions, the elastic moduli of chromosomes can be reduced by more than 20-fold, and they appear as "ghosts": swollen, elongated, and with reduced optical contrast under both phase and differential interference contrast imaging. Antibody labeling indicates that histone proteins are not being lost during even extreme extensions. Results are interpreted in terms of extension and failure of chromatin-tethering elements; the force data allow estimates of the number and size of such connectors in a chromosome.

The Vibratory Unconfined Compression Tester(VUCT) for Cohesive Solids

A Vibrational Unconfined Compression Tester has been developed which superimposes applied vibration upon axial compression for a cylindrical sample of cohesive material. The VUCT has been applied to systems of wet sands. During applied vibration, the material retreated into elastic space within each vibration cycle. The top cap stress/axial strain curve progressed through a series of hysteresis loops. The instantaneous values of peak axial stress, Pi, and averaged values, Pave, have been compared with peak stresses for control tests with no applied vibration, Pnv. Pave always gave lower values than Pi, due to the cyclic nature of the system. However, in some tests Pi was not significantly different from Pnv. Thus, Pave is not an appropriate parameter for determination of the effects of vibration upon material strength. In some cases, vibration caused a genuine reduction in material strength as measured by peak stress. This depended upon applied vibration and material properties. The maximum reduction in strength did not correspond to resonance frequency.