Role Of Hysteresis Research Articles

Toward a high performance and strong resilience wind energy harvester assembly utilizing flow-induced vibration: Role of hysteresis

Wind energy harvester utilizing flow-induced vibration (FIV-WEH) has attracted much attention because of its ability to capture low-speed wind energy. This study is motivated to design a reliable FIV-WEH assembly in a wind farm, and to understand the altered environmental flow and disturbed output performance through large-eddy simulations and wind tunnel experiments, for the sake of harnessing fluctuating near-ground wind energy efficiently. The results demonstrates that the proposed eco-friendly FIV-WEH assembly has less impact on the surroundings due to the fast recovery of turbulent wake. Moreover, it is equipped with remarkable hysteresis caused by the delay of wake transition from 2P to C mode, which can enhance the output power, effective wind band, and more importantly, resilience. The resilience guarantees that the FIV-WEH assembly can harvest the fluctuating wind resources optimally even under strong turbulence intensity. Specifically, compact FIV-WEH assembly (l ≤ 1.5, where l is dimensionless streamwise span) based on extended-body regime has a low cut-in speed (3 m/s), showing great potential to harvest breeze energy in a near-ground residential environment. Loose FIV-WEH assembly (1.5 < l < 5) based on reattachment regime has a large cut-in speed (9 m/s) and low span-sensitivity, which can be flexibly adjusted to extract the wind energy in spacious wind-abundant areas. Finally, two strategies developed by modifying surfaces of FIV-WEH assembly can further enhance the resilience and conversion efficiency by approximately 200%.

The Role of Hysteresis in Caching Systems

Caching is a fundamental element of networking systems since the early days of the Internet. By filtering requests toward custodians, caches reduce the bandwidth required by the latter and the delay experienced by clients. The requests that are not served by a cache, in turn, comprise its miss stream. We refer to the dependence of the cache state and miss stream on its history as hysteresis. Although hysteresis is at the core of caching systems, a dimension that has not been systematically studied in previous works relates to its impact on caching systems between misses, evictions, and insertions. In this article, we propose novel mechanisms and models to leverage hysteresis on cache evictions and insertions. The proposed solutions extend TTL-like mechanisms and rely on two knobs to tune the time between insertions and evictions given a target hit rate. We show the general benefits of hysteresis and the particular improvement of the two thresholds strategy in reducing download times, making the system more predictable and accounting for different costs associated with object retrieval.

Geometry of polygonal hydraulic jumps and the role of hysteresis

An experimental study shows that polygonal hydraulic jumps, which are formed when a liquid jet impacts a target plate, can exhibit modal hysteresis, yet the normalized jump geometry $A/P\phantom{\rule{0}{0ex}}H$ is unaffected by the flow history and has a weak dependence on the weir geometry. All experimental data collapses upon scaling with the downstream Weber number, illustrating the role of surface tension in mode selection.

A Constraint-based model of Dynamic Island Biogeography: environmental history and species traits predict hysteresis in populations and communities

A Constraint-based model of Dynamic Island Biogeography: environmental history and species traits predict hysteresis in populations and communities We present a conceptual model that shows how hysteresis can emerge in dynamic island systems given simple constraints on trait-mediated processes. Over time, many islands cycle between phases of increasing and decreasing size and connectivity to a mainland species pool. As these phases alternate, the dominant process driving species composition switches between colonization and extinction. Both processes are mediated by interactions between organismal traits and environmental constraints: colonization probability is affected by a species’ ability to cross the intervening matrix between a population source and the island; population persistence (or extinction) is driven by the minimum spatial requirements for sustaining an isolated population. Because different suites of traits often mediate these two processes, similar environmental conditions can lead to differences in species compositions at two points of time. Thus, the Constraint-based model of Dynamic Island Biogeography (C-DIB) illustrates the possible role of hysteresis—the dependency of outcomes not only on the current system state but also the system’s history of environmental change—in affecting populations and communities in insular systems. The model provides a framework upon which additional considerations of lag times, biotic interactions, evolution, and other processes can be incorporated. Importantly, it provides a testable framework to study the physical and biological constraints on populations and communities across diverse taxa, scales, and systems.

Laboratory experiments on the role of hysteresis, defect dynamics and initial perturbation on wave-generated ripple development

We performed a series of laboratory experiments to study the growth and development of wave-generated ripples under constant and varying conditions. There are two aspects of our study. First, under time varying wave conditions, we measure the rate of ripple adjustment and the equilibrium mean ripple wavelength before and after the change in forcing. Our experiments with increasing wave forcing (i.e., increasing wave amplitude or wave period) lead to faster ripple growth and larger final wavelengths. Decreasing wave forcing leads to shorter ripple wavelengths and hysteresis. Existing predictors provide a reasonable description of both the final equilibrium spacing and of the spacing evolution after wave conditions are changed. The presence of defects (crestline irregularities) impacts the final equilibrium ripple wavelength. Second, we investigate the role of initial perturbation on ripple growth and geometry. Larger initial perturbations in the bed lead to faster growth of ripples and larger initial ripple wavelength. Our results suggest that irregularities at the pattern scale, such as defects and initial bed perturbations, are likely to impact ripple evolution and can be a control factor on hysteresis.

Basaltic sand ripples at Eagle Crater as indirect evidence for the hysteresis effect in martian saltation

The rover Opportunity documented small basaltic sand ripples at the bottom of Eagle Crater, Meridiani Planum on Mars. These ripples are composed of fine basaltic sand (∼100μm diameter) and their average wavelength and height are 10cm and 1cm, respectively. Present theories on the transition between saltation and suspension predict that such light particles are suspended by turbulence at the fluid threshold, which is the minimum wind speed required to initiate saltation. Consequently, the existence of these ∼100μm ripples on Mars indicates that either current suspension theories are incorrect, or that saltation can take place at wind speeds substantially below the fluid threshold. Indeed, recent studies point to the occurrence of hysteresis in martian saltation. That is, once initiated, hysteresis can be maintained at much lower wind speeds than the fluid threshold. We investigated the possible role of hysteresis in the formation of fine-grained ripples on Mars by coupling, for the first time, a detailed numerical saltation model (COMSALT) with a dynamic model for sand ripple formation. The results from the coupled model indicate that ripples with properties similar to those observed at Eagle Crater can be developed by the impact mechanism at shear velocities far below the fluid threshold. These findings are consistent with the occurrence of hysteresis in martian saltation, and support the hypothesis that hysteresis plays a role in the surprisingly large sand mobility observed at several locations on Mars.

Role of hysteresis in stomatal aperture dynamics

Stomata are pores responsible for gas exchange in leaves. Several experiments indicate that stomata synchronize into clusters or patches. The patches' coordination may produce oscillations in stomatal conductance. Previous studies claim to reproduce some experimental results. However, none was able to explain the variety of behavior observed in the stomatal dynamics. Recently, Ferraz and Prado suggested a realistic geometry of vein distribution. Although it reproduces the patches, no oscillation was observed and the patches remain static. Without exploring significant details, the authors stated that hysteresis in stomatal aperture could explain several experimental features. In this paper, the hysteresis hypothesis is further explored through the concept of hysteretic operators. We have shown that the hysteresis assumption is sufficient to obtain dynamical patches and oscillations in stomatal conductance. The robustness of this hypothesis is tested by using different hysteresis operators. The model analysis reveals a dependence between the period of oscillation in stomatal conductance and the water deficit between the leaf and the environment. This underlying feature of the model might inspire further experiments to test this hypothesis.

Direct measurements of the entropy change and its history dependence in Ni–Mn–Ga alloys

The role of hysteresis on materials with giant magnetocaloric effect (GMCE) was pointed out by comparing isothermal entropy change measured on a Ni55Mn20Ga25 single crystal presenting a first order magnetostructural phase transition. The entropy change is determined by a laboratory Peltier calorimeter with magnetic field of up to 2T. The measurements performed have allowed to compare the entropy change in partial or complete phase transitions induced by temperature or magnetic field, respectively. The sequence in the temperature and field change affects dramatically the observed MCE demonstrating that a control on both quantities must be accurately performed in order to extract the whole available entropy change. This kind of behavior can be explained if hysteresis in the first order phase transition is taken into account and a correct field-temperature sequence is proposed in order to maximize the MCE.

Carnot cycle for magnetic materials: The role of hysteresis

The role of hysteresis in a refrigeration thermodynamic cycle involving ferromagnetic materials is discussed. A model allowing to calculate magnetization, entropy and entropy production in systems with hysteresis is used to compute a non-ideal Carnot cycle performed on a ferromagnetic material.

About the role of hysteresis in magnetic penetration at extremely low frequency

In this paper a discussion about the role of magnetic hysteresis on the magnetic field distortion and attenuation is presented. A one-dimensional FDITD algorithm has been used to evaluate the weight of hysteresis in determining the magnetic field attenuation for a magnetic iron hollow indefinite thin cylinder. On the basis of such an analysis a second 2D-FEM numerical algorithm has been implemented taking into account only the virgin magnetization curve, therefore, not describing the hysteretic cycles and simulations have been done for a finite thin hollow cylinder geometry. To investigate the approximation due to such a strategy an experimental setup has been implemented and results have been compared. Data have shown that for the investigated geometry and materials the error remains small validating the simplified methodology at least from an engineering point of view.

Role of hysteresis in the molecular picture of friction

A constrained Monte Carlo technique was used to study the effects of hysteresis on the friction curve (shear yield stress s. normal stress) for an ideal microscopic contact: two rigid crystalline surfaces separated by a mobile adsorbed film. The constraint in the form of an auxiliary external field corresponds to the relaxation time for migration of admolecules relative to the time required for a measurement. Wide variation in the form of the friction curve with the (relative) relaxation time shows that hysteresis (irreversibility) must be incorporated into a complete molecular picture of friction.

Analytical and Computational Advances for Hydrodynamic Models of Classical and Quantum Charge Transport

In recent years, substantial advances have been made in understanding hydrodynamic models, both from the standpoint of analytical infrastructure, as well as the parameters which play a decisive effect in the behavior of such models. Both classical and quantum hydrodynamic models have been studied in depth. In this survey paper, we describe several results of this type. We include, for example, well-posedness for both classical and quantum reduced models, and the relaxation drift–diffusion limit as examples of analytical results. As examples of computational results, we include some discussion of effective algorithms, but most importantly, some information gleaned from extensive simulation. In particular, we present our findings of the prominent role played by the mobilities in the classical models, and the role of hysteresis in the quantum models. All models are self-consistent. Included is discussion of recent analytical results on the use of Maxwell’s equations. Benchmark devices are utilized: the MESFET transistor and the n+/n/n+ diode for classical transport, and the resonant tunneling diode for quantum transport. Some comparison with the linear Boltzmann transport equation is included.

Hysteresis and the earnings of immigrants in the United States labour market

The paper analyses the role of hysteresis in explaining the slow wage convergence between certain immigrant groups and native workers. Using the 1990 Integrated Public Use Microdata Samples (IPUMS), the analysis reveals that past earnings history in the country of origin has a relatively smaller effect on post-migration earnings when compared to past earnings history in the US. In addition, the paper suggests that the earnings history in the country of origin is more productive in the US labour market for immigrants from advanced economies as compared to those from less-developed countries. In particular, we find that US labour market does not value the past earnings history of Mexican immigrants as high as that of other ethnic groups with similar socioeconomic characteristics across successive cohorts.

On the role of hysteresis for flux distributions in transformer cores

In spite of the systems simplicity, single phase transformer cores show distinct flux inhomogeneities. Earlier it has been predicted numerically that the latter are affected also by effects of hysteresis which has not been considered so far. The aim of the present work was to verify these predictions experimentally and to interpret the involved physical mechanisms. The flux distribution of a model core was locally analysed by means of search coils through the whole core, the corresponding field by means of tangential H-coils. The results indicate distinct local variations of dynamic hysteresis loops, the interpretation of which is complicated through anisotropy. Hysteresis proves to cause specific effects such as asymmetrical waveforms of flux. Further it yields phase shifts corresponding to antiparallel circulation of flux portions throughout the core.

The Role of Hysteresis in Tire Wear and Laboratory Abrasion

Abstract The simple theory outlined in this paper accounts for the wear of slipping wheels in their dependence on external parameters. In addition, it draws attention to the importance of the elastic properties and the unsuspected influence of mechanical hysteresis. The experimental evidence brought forward in support of this side of the theory stems mostly from laboratory work. When attempting to apply the theory to road wear, it must be kept in mind that the mechanical properties of tires are only in part determined by the tread, their elastic behavior being largely that of the pneumatic casing. Laboratory experiments carried out with solid wheels give therefore an exaggerated estimate of the influence exercised by the hysteresis of the tread on the rate of wear. Nevertheless, the relation between wear and hysteresis should be as valid for tires as for other slipping wheels, if the resilience pertaining to the tire as a whole is introduced into the calculations. There is another aspect of hysteresis which might usefully be mentioned here. In the foregoing, the rolling resistance of tires has been neglected. While rolling resistance has most probably little effect on the wear mechanism, it does increase with increasing hysteresis of the tire. Thus, lengthening the life of a tire by increasing its hysteresis has to be paid for by an increased fuel bill.

The role of hysteresis in reducing evaporation from soils in contact with a water table

Evaporation studies were conducted on three soil types in contact with a water table. For conditions of high evaporativity or increased depth to the water table, it was found that evaporation from the soils was not always in proportion to the rate of evaporation from a free-water surface. Under some conditions there was an inverse relation between evaporation from the soils and that from the free-water surface. Analysis of upward movement of water from a water table in the absence of hysteresis effects does not provide a satisfactory explanation for this inverse relation. A capillary tube model is used to explain qualitatively these results on the basis of reversals of changes in pressure in the soil water. This hysteresis phenomenon is believed to be responsible for reducing evaporation from soils in contact with a water table.