NASA Astrophysics Data System (ADS)
Fujisaki, Keisuke; Liu, Sungju
2014-05-01
The influence of power semiconductor characteristic in Pulse-width-modulation (PWM) inverter on the magnetic hysteresis curve in silicon steel is discussed through the measured magnetic hysteresis curves. The magnetic hysteresis curve of PWM inverter-fed silicon steel has a lot of minor loops as closed loops and open loops, which make an influence on the iron loss. Two shapes of minor loops are found to be caused by the voltage shifts and they are derived from the on-voltage of the semiconductors in PWM inverter circuit. Therefore, it is concluded that the power-semiconductor characteristic in PWM inverter makes an influence on the magnetic hysteresis curve in silicon steel.
Hysteresis and uncertainty in soil water-retention curve parameters
Likos, William J.; Lu, Ning; Godt, Jonathan W.
2014-01-01
Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting hydraulic and mechanical responses in a large number of applications. A comprehensive suite of laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) representing a wide range of soil types. Results were used to quantitatively assess differences and uncertainty in three simplifications frequently adopted to estimate wetting-path SWCC parameters from more easily measured drying curves. They are the following: (1) αw=2αd, (2) nw=nd, and (3) θws=θds, where α, n, and θs are fitting parameters entering van Genuchten’s commonly adopted SWCC model, and the superscripts w and d indicate wetting and drying paths, respectively. The average ratio αw/αd for the data set was 2.24±1.25. Nominally cohesive soils had a lower αw/αd ratio (1.73±0.94) than nominally cohesionless soils (3.14±1.27). The average nw/nd ratio was 1.01±0.11 with no significant dependency on soil type, thus confirming the nw=nd simplification for a wider range of soil types than previously available. Water content at zero suction during wetting (θws) was consistently less than during drying (θds) owing to air entrapment. The θws/θds ratio averaged 0.85±0.10 and was comparable for nominally cohesive (0.87±0.11) and cohesionless (0.81±0.08) soils. Regression statistics are provided to quantitatively account for uncertainty in estimating hysteretic retention curves. Practical consequences are demonstrated for two case studies.
Laminar-Turbulent Transition: A Hysteresis Curve of Two Critical Reynolds Numbers in Pipe Flow
NASA Astrophysics Data System (ADS)
Kanda, Hidesada
2006-11-01
A laminar-turbulent transition model (DFD 2004) has been constructed for pipe flows: (1) Natural transition occurs in the entrance region, and (2) Entrance shape determines a critical Reynolds number Rc. To verify the model, we have carried out experiments similar to Reynolds's color-dye experiment with 5 bellmouth entrances and a straight pipe. Then, we observed the following: (i) two different types of Rc exist, Rc1 from laminar to turbulent and Rc2 from turbulent to laminar, and (ii) the ratio of bellmouth diameter BD to pipe diameter D affects the values of Rc1 and Rc2. For each entrance, Rc1 has a maximum value Rc1(max) and Rc2 has a minimum value Rc2(min). When overlapping the two curves of Rc1(max) and Rc2(min) against BD/D, a hysteresis curve is confirmed. All Rc values exist inside this hysteresis curve. Consequently, Rc takes a minimum value Rc(min) of approximately 2000 when BD/D is at a minimum, i.e., at BD/D = 1, Rc(min) = Rc1(max) = Rc2(min) = 2000. Regarding Reynolds's Rc of 12,830, we observed Rc1(max) of approximately 13,000 at BD/D above 1.54. Therefore, the model has been partly verified.
View to southwest along bridge alignment, showing reverse curve; photographer ...
View to southwest along bridge alignment, showing reverse curve; photographer unknown; 1933 photo from collection of Office-of Structures Maintenance, California Department of Transportation, Sacramento - Carroll Overhead Bridge, Altamont Pass Road, Livermore, Alameda County, CA
van Vörden, Dennis; Möller, Rolf
2012-01-01
Summary Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111) √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force–distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle. PMID:22496993
Lange, Manfred; van Vörden, Dennis; Möller, Rolf
2012-01-01
Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip-sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111) √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force-distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle. PMID:22496993
Organic matter turnover in a tropical floodplain shows hysteresis during a flood cycle
NASA Astrophysics Data System (ADS)
Zuijdgeest, Alissa; Baumgartner, Simon; Wehrli, Bernhard
2016-04-01
Tropical inland waters are increasingly recognized for their role in the global carbon cycle, but uncertainty about the effects of such systems on the transported organic matter remains. The seasonal interactions between river, floodplain, and vegetation result in highly dynamic systems, which can exhibit markedly different biogeochemical patterns throughout a flood cycle. In this study, we investigated patterns and rates of organic matter turnover, and determined responsible processes. Multi-probes upstream and downstream of the Barotse Plains, a pristine floodplain in the Upper Zambezi (Zambia), provided a high-resolution data set over the course of a hydrological cycle. Concentrations of oxygen, carbon dioxide, dissolved organic carbon, and suspended particulate matter in water column of the main channel showed clear hysteresis trends relative to hydrological parameters. Considering that the respiration rate in the river water remained rather low and stable throughout the year, these patterns indicated that degradation of the terrestrial organic matter was mainly occurring on the floodplain. We suggest that the main location of terrestrially-derived organic matter degradation in river-floodplain systems shifts during a flood cycle from the water of the main channel, to the soil-water interface on the floodplain when the water spends more time on the floodplain.
View to southwest along bridge alignment, showing reverse curve from ...
View to southwest along bridge alignment, showing reverse curve from near deck level; Southern Pacific Railroad track passing beneath bridge; Western Pacific Railroad track out of sight behind bridge; photographer unknown; 1933 photo from collection of Office of Structures Maintenance, California Department of Transportation, Sacramento - Carroll Overhead Bridge, Altamont Pass Road, Livermore, Alameda County, CA
Interior detail, building 810, view to north showing curved chord ...
Interior detail, building 810, view to north showing curved chord sections of roof trusses, 90mm lens plus electronic flash fill lighting. - Travis Air Force Base, B-36 Hangar, Between Woodskill Avenue & Ellis, adjacent to Taxiway V & W, Fairfield, Solano County, CA
Stan, Raluca-Maria; Gaina, Roxana; Enachescu, Cristian E-mail: radu.tanasa@uaic.ro; Stancu, Alexandru; Tanasa, Radu E-mail: radu.tanasa@uaic.ro; Bronisz, Robert
2015-05-07
In this paper, we analyze two types of hysteresis in spin crossover molecular magnets compounds in the framework of the First Order Reversal Curve (FORC) method. The switching between the two stable states in these compounds is accompanied by hysteresis phenomena if the intermolecular interactions are higher than a threshold. We have measured the static thermal hysteresis (TH) and the kinetic light induced thermal hysteresis (LITH) major loops and FORCs for the polycrystalline Fe(II) spin crossover compound [Fe{sub 1−x}Zn{sub x}(bbtr){sub 3}](ClO{sub 4}){sub 2} (bbtr = 1,4-di(1,2,3-triazol-1-yl)butane), either in a pure state (x = 0) or doped with Zn ions (x = 0.33) considering different sweeping rates. Here, we use this method not only to infer the domains distribution but also to disentangle between kinetic and static components of the LITH and to estimate the changes in the intermolecular interactions introduced by dopants. We also determined the qualitative relationship between FORC distributions measured for TH and LITH.
Stoleriu, Laurentiu E-mail: cristian.enachescu@uaic.ro; Stancu, Alexandru; Enachescu, Cristian E-mail: cristian.enachescu@uaic.ro; Chakraborty, Pradip; Hauser, Andreas
2015-05-07
The recently obtained spin-crossover nanoparticles are possible candidates for applications in the recording media industry as materials for data storage, or as pressure and temperature sensors. For these applications, the intermolecular interactions and interactions between spin-crossover nanoparticles are extremely important, as they may be essential factors in triggering the transition between the two stable phases: the high-spin and low-spin ones. In order to find correlations between the distributions in size and interactions and the transition temperatures distribution, we apply the FORC (First Order Reversal Curves) method, using simulations based on a mechanoelastic model applied to 2D triangular lattices composed of molecules linked by springs and embedded in a surfactant. We consider two Gaussian distributions: one is the size of the nanoparticles and another is the elastic interactions between edge spin-crossover molecules and the surfactant molecules. In order to disentangle the kinetic and non-kinetic parts of the FORC distributions, we compare the results obtained for different temperature sweeping rates. We also show that the presence of few larger particles in a distribution centered around much smaller particles dramatically increases the hysteresis width.
Curves showing column strength of steel and duralumin tubing
NASA Technical Reports Server (NTRS)
Ross, Orrin E
1929-01-01
Given here are a set of column strength curves that are intended to simplify the method of determining the size of struts in an airplane structure when the load in the member is known. The curves will also simplify the checking of the strength of a strut if the size and length are known. With these curves, no computations are necessary, as in the case of the old-fashioned method of strut design. The process is so simple that draftsmen or others who are not entirely familiar with mechanics can check the strength of a strut without much danger of error.
NASA Astrophysics Data System (ADS)
Giorgi, Giacomo; Yamashita, Koichi
2015-11-01
Starting from a brief description of the main architectures characterizing the novel solar technology of perovskite-based solar cells, we focus our attention on the anomalous hysteresis experimentally found to affect the measurement of the current-voltage curve of such devices. This detrimental effect, associated with slow dynamic reorganization processes, depends on several parameters; among them, the scan rate of the measurements, the architecture of the cell, and the perovskite deposition rate are crucial. Even if a conclusive explanation of the origin of the hysteresis has not been provided so far, several experimental findings ascribe its origin to ionic migration at an applied bias and dielectric polarization that occurs in the perovskite layer. Consistently, a dipole-moment-reduced cation such as formamidinium ion is experimentally reported to quantitatively reduce the hysteresis from perovskite-based devices. By means of a density-functional theory-based set of calculations, we have predicted and characterized guanidinium ion (GA = +[C(NH2)3], a zero-dipole moment cation by symmetry)-based organic-inorganic halide perovskite’s structural and electronic properties, speculating that such a cation and the alloys it may form with other organic cations can represent a possible chemical solution for the puzzling issue of the hysteresis.
Giorgi, Giacomo; Yamashita, Koichi
2015-11-01
Starting from a brief description of the main architectures characterizing the novel solar technology of perovskite-based solar cells, we focus our attention on the anomalous hysteresis experimentally found to affect the measurement of the current-voltage curve of such devices. This detrimental effect, associated with slow dynamic reorganization processes, depends on several parameters; among them, the scan rate of the measurements, the architecture of the cell, and the perovskite deposition rate are crucial. Even if a conclusive explanation of the origin of the hysteresis has not been provided so far, several experimental findings ascribe its origin to ionic migration at an applied bias and dielectric polarization that occurs in the perovskite layer. Consistently, a dipole-moment-reduced cation such as formamidinium ion is experimentally reported to quantitatively reduce the hysteresis from perovskite-based devices. By means of a density-functional theory-based set of calculations, we have predicted and characterized guanidinium ion (GA = (+)[C(NH2)3], a zero-dipole moment cation by symmetry)-based organic-inorganic halide perovskite's structural and electronic properties, speculating that such a cation and the alloys it may form with other organic cations can represent a possible chemical solution for the puzzling issue of the hysteresis. PMID:26468971
NASA Astrophysics Data System (ADS)
Mellado, Paula; Concha, Andres; Aguayo, David
Hysteresis manifests as the lack of retraceability of the magnetization curve in magnetic systems. It has been associated with rotation of magnetization and changes of magnetic domains. However, up to date there has been no realization that allows to separate these coupled mechanisms. We introduce a minimal magnetic system where hysteresis is realized in a simple and minimal fashion. The basic units are a few U(1) ferromagnetic altitudinal rotors placed along a one dimensional chain. They exhibit a dissipative dynamics, interacting via magnetic coupling among them and via Zeeman interaction with the external magnetic field. The system displays a hysteretic behavior starting with N=2 rotors which remains qualitatively invariant as more magnets are added to the chain. We explain this irreversibility by using a model that includes Coulombic interactions between magnetic charges located at the ends of the magnets, zeeman coupling and viscous dissipation. We show that interactions between the unit components is the key element responsible for hysteresis and find that the ability to perceive hysteresis, depends on how the time frequencies of damping and interactions inherent to the system compare with the time frequency set by the external field ramping rate.
NASA Astrophysics Data System (ADS)
Cao, Yue; Xu, Ke; Jiang, Weilin; Droubay, Timothy; Ramuhalli, Pradeep; Edwards, Danny; Johnson, Bradley R.; McCloy, John
2015-12-01
Hysteretic behavior was studied in a series of Fe thin films, grown by molecular beam epitaxy, having different grain sizes and grown on different substrates. Major and minor loops and first order reversal curves (FORCs) were collected to investigate magnetization mechanisms and domain behavior under different magnetic histories. The minor loop coefficient and major loop coercivity increase with decreasing grain size due to higher defect concentration resisting domain wall movement. First order reversal curves allowed estimation of the contribution of irreversible and reversible susceptibilities and switching field distribution. The differences in shape of the major loops and first order reversal curves are described using a classical Preisach model with distributions of hysterons of different switching fields, providing a powerful visualization tool to help understand the magnetization switching behavior of Fe films as manifested in various experimental magnetization measurements.
NASA Astrophysics Data System (ADS)
Sablik, M. J.; Rios, S.; Landgraf, F. J. G.; Yonamine, T.; de Campos, M. F.
2005-05-01
In 2.2% Si electrical steel, the magnetic hysteresis behavior is sharply sheared by a rather small plastic deformation (0.5%). A modification to the Jiles-Atherton hysteresis model makes it possible to model magnetic effects of plastic deformation. In this paper, with this model, it is shown how a narrow hysteresis with an almost steplike hysteresis curve for an undeformed specimen is sharply sheared by plastic deformation. Computed coercivity and hysteresis loss show a sharp step to higher values at small strain due to an n =1/2 power law dependence on residual strain. The step is seen experimentally.
Sablik, M.J.; Rios, S.; Landgraf, F.J.G.; Yonamine, T.; Campos, M.F. de
2005-05-15
In 2.2% Si electrical steel, the magnetic hysteresis behavior is sharply sheared by a rather small plastic deformation (0.5%). A modification to the Jiles-Atherton hysteresis model makes it possible to model magnetic effects of plastic deformation. In this paper, with this model, it is shown how a narrow hysteresis with an almost steplike hysteresis curve for an undeformed specimen is sharply sheared by plastic deformation. Computed coercivity and hysteresis loss show a sharp step to higher values at small strain due to an n=1/2 power law dependence on residual strain. The step is seen experimentally.
AN Lyn: a multiperiodic Delta Scuti star showing atypical light curves
NASA Astrophysics Data System (ADS)
Rodriguez, E.; Gonzalez-Bedolla, S. F.; Rolland, A.; Costa, V.; Lopez-Gonzalez, M. J.; Lopez de Coca, P.
1997-07-01
We have collected simultaneous uvby photometry of the Delta Sct star AN Lyn during the years 1995 and 1996 at the observatories of San Pedro Mertir, Mexico and Sierra Nevada, Spain. Firstly, analysis of frequencies of our 1995's data set was carried out using the Discrete Fourier Transform method, as described in Lopez de Coca et al. (1984), to the filter v. The periodograms showed a principal peak at v1 ~ 10.1756 c/d, very close to that frequency which corresponds to the period P ~0.0982739 d derived from earlier works. After prewhitening for v1 we found a second peak at 20.3525 c/d that corresponds to 2*v1. When these two frequencies are subtracted from the light curves, the periodograms show some peaks that reveal that additional frequencies are remaining in the spectra at very low amplitude as compared with the amplitude of the main peak (less than 5%).
NASA Astrophysics Data System (ADS)
Nobuhiko Sakai,; Ritthikrai Chai-Ngam,; Akihisa Koizumi,; Hisao Kobayashi,
2010-06-01
The spacer thickness dependence of the interlayer magnetic coupling (IMC) between Gd and Fe layers separated by Al spacers has been studied. Magnetization measurement and X-ray magnetic circular dicroism (XMCD) spectroscopy at the Gd-L3 edge have been carried out on sputtered Fe (20 Å)/Al (R Å)/Gd (40 Å) multilayer films (MLFs) for R = 0, 5, 10, and 100 and on some reference films. Experimental data at low magnetic fields below 1 kOe are carefully investigated. A simple theoretical model is introduced to evaluate the strength of IMC. The energy of IMC is represented by the term J MFe \\cdot MGd, in which MFe and MGd denote the average overall magnetic moments of Fe and Gd layers, respectively. It is found that J, which is evaluated from the magnetization curves and the Gd-XMCD signals, is 370 × 104 Oe\\cdotcm2/emu for MLF of R = 0, and can be reduced by one order of magnitude when R is changed from 0 to 10. Most of characteristic features of the experimental data are ascribed to the varing magnetization of Gd layers. It is found that 40 Å Gd layers, which are paramagnetic at 5 K when isolated using 100 Å Al spacers, show magnetic hysteresis when sandwiched between Fe layers.
Lin, Maozi; Wang, Zhiwei; He, Lingchao; Xu, Kang; Cheng, Dongliang; Wang, Genxuan
2015-01-01
Photosynthesis-irradiance (PI) curves are extensively used in field and laboratory research to evaluate the photon-use efficiency of plants. However, most existing models for PI curves focus on the relationship between the photosynthetic rate (Pn) and photosynthetically active radiation (PAR), and do not take account of the influence of environmental factors on the curve. In the present study, we used a new non-competitive inhibited Michaelis-Menten model (NIMM) to predict the co-variation of Pn, PAR, and the relative pollution index (I). We then evaluated the model with published data and our own experimental data. The results indicate that the Pn of plants decreased with increasing I in the environment and, as predicted, were all fitted well by the NIMM model. Therefore, our model provides a robust basis to evaluate and understand the influence of environmental pollution on plant photosynthesis. PMID:26561863
Isotropic hysteresis modeling of Fe-Co-B alloys
NASA Astrophysics Data System (ADS)
Hauser, Hans; Grössinger, Roland
1999-04-01
The energetic model of ferromagnetic hysteresis calculates the magnetic state of materials by minimizing the total energy function for statistical domain behavior. The physical constants of this model are derived from anisotropy energy constants, initial susceptibility, coercivity, and saturation magnetization. The approach shows a good agreement to the magnetization curves of FeCoB strips, also in dependence of applied stress.
NASA Technical Reports Server (NTRS)
Flatley, Thomas W.; Henretty, Debra A.
1995-01-01
The Passive Aerodynamically Stabilized Magnetically Damped Satellite (PAMS) will be deployed from the Space Shuttle and used as a target for a Shuttle-mounted laser. It will be a cylindrical satellite with several corner cube reflectors on the ends. The center of mass of the cylinder will be near one end, and aerodynamic torques will tend to align the axis of the cylinder with the spacecraft velocity vector. Magnetic hysteresis rods will be used to provide passive despin and oscillation-damping torques on the cylinder. The behavior of the hysteresis rods depends critically on the 'B/H' curves for the combination of materials and rod length-to-diameter ratio ('l-over-d'). These curves are qualitatively described in most Physics textbooks in terms of major and minor 'hysteresis loops'. Mathematical modeling of the functional relationship between B and H is very difficult. In this paper, the physics involved is not addressed, but an algorithm is developed which provides a close approximation to empirically determined data with a few simple equations suitable for use in computer simulations.
Mathematical models of hysteresis
1998-08-01
The ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema (not the entire input variations) leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. The origin of such tools can be traced back to the landmark paper of Preisach. Their research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. During the past four years, the study has been by and large centered around the following topics: (1) further development of Scalar and vector Preisach-type models of hysteresis; (2) experimental testing of Preisach-type models of hysteresis; (3) development of new models for viscosity (aftereffect) in hysteretic systems; (4) development of mathematical models for superconducting hysteresis in the case of gradual resistive transitions; (5) software implementation of Preisach-type models of hysteresis; and (6) development of new ideas which have emerged in the course of the research work. The author briefly describes the main scientific results obtained in the areas outlined above.
[Mathematical models of hysteresis
Mayergoyz, I.D.
1991-01-01
The research described in this proposal is currently being supported by the US Department of Energy under the contract Mathematical Models of Hysteresis''. Thus, before discussing the proposed research in detail, it is worthwhile to describe and summarize the main results achieved in the course of our work under the above contract. Our ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories''. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. Our research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. Our study has by and large been centered around the following topics: various generalizations and extensions of the classical Preisach model, finding of necessary and sufficient conditions for the representation of actual hysteretic nonlinearities by various Preisach type models, solution of identification problems for these models, numerical implementation and experimental testing of Preisach type models. Although the study of Preisach type models has constituted the main direction of the research, some effort has also been made to establish some interesting connections between these models and such topics as: the critical state model for superconducting hysteresis, the classical Stoner-Wohlfarth model of vector magnetic hysteresis, thermal activation type models for viscosity, magnetostrictive hysteresis and neural networks.
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan; Banerjee, Shreya
2016-07-01
Hysteresis is a phenomenon occurring naturally in several magnetic and electric materials in condensed matter physics. When applied to cosmology, aka cosmological hysteresis, has interesting and vivid implications in the scenario of a cyclic bouncy universe. Most importantly, this physical prescription can be treated as an alternative proposal to inflationary paradigm. Cosmological hysteresis is caused by the asymmetry in the equation of state parameter during expansion and contraction phase of the universe, due to the presence of a single scalar field. This process is purely thermodynamical in nature, results in a non-vanishing hysteresis loop integral (∮pdV) in cosmology. When applied to variants of modified gravity models 1) Dvali-Gabadadze-Porrati (DGP) brane world gravity, 2) Cosmological constant dominated Einstein gravity, 3) Loop Quantum Gravity (LQG), 4) Einstein-Gauss-Bonnet brane world gravity and 5) Randall Sundrum single brane world gravity (RSII), under certain circumstances, this phenomenon leads to the increase in amplitude of the consecutive cycles and to a universe with older and larger successive cycles, provided we have physical mechanisms to make the universe bounce and turnaround. This inculcates an arrow of time in a dissipationless cosmology. Remarkably, this phenomenon appears to be widespread in several cosmological potentials in variants of modified gravity background, which we explicitly study for i) Hilltop, ii) Natural and iii) Coleman-Weinberg potentials, in this paper. Semi-analytical analysis of these models, for different potentials with minimum/minima, show that the conditions which creates a universe with an ever increasing expansion, depend on the signature of the hysteresis loop integral (∮pdV) as well as on the variants of model parameters.
The magnetization process: Hysteresis
NASA Technical Reports Server (NTRS)
Balsamel, Richard
1990-01-01
The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hysteresis and the hysteresis of common magnetic materials is described in detail.
Tokunaga, Tetsu K.; Olson, Keith R.; Wan, Jiamin
2004-03-12
Hysteresis in the relation between water saturation and matric potential is generally regarded as a basic aspect of unsaturated porous media. However, the nature of an upper length scale limit for saturation hysteresis has not been previously addressed. Since hysteresis depends on whether or not capillary rise occurs at the grain scale, this criterion was used to predict required combinations of grain size, surface tension, fluid-fluid density differences, and acceleration in monodisperse systems. The Haines number (Ha), composed of the aforementioned variables, is proposed as a dimensionless number useful for separating hysteretic (Ha < 15) versus nonhysteretic (Ha > 15) behavior. Vanishing of hysteresis was predicted to occur for grain sizes greater than 10.4 +- 0.5 mm, for water-air systems under the acceleration of ordinary gravity, based on Miller-Miller scaling and Haines' original model for hysteresis. Disappearance of hysteresis was tested through measurements of drainage and wetting curves of sands and gravels and occurs between grain sizes of 10 and 14 mm (standard conditions). The influence of surface tension was tested through measurements of moisture retention in 7 mm gravel, without and with a surfactant (sodium dodecylbenzenesulfonate (SDBS)). The ordinary water system (Ha = 7) exhibited hysteresis, while the SDBS system (Ha = 18) did not. The experiments completed in this study indicate that hysteresis in moisture retention relations has an upper limit at Ha = 16 +- 2 and show that hysteresis is not a fundamental feature of unsaturated porous media.
New approach to the calculation of pistachio powder hysteresis
NASA Astrophysics Data System (ADS)
Tavakolipour, Hamid; Mokhtarian, Mohsen
2016-04-01
Moisture sorption isotherms for pistachio powder were determined by gravimetric method at temperatures of 15, 25, 35 and 40°C. A selected mathematical models were tested to determine the best suitable model to predict isotherm curve. The results show that Caurie model had the most satisfactory goodness of fit. Also, another purpose of this research was to introduce a new methodology to determine the amount of hysteresis at different temperatures by using best predictive model of isotherm curve based on definite integration method. The results demonstrated that maximum hysteresis is related to the multi-layer water (in the range of water activity 0.2-0.6) which corresponds to the capillary condensation region and this phenomenon decreases with increasing temperature.
Modeling of hysteresis in gene regulatory networks.
Hu, J; Qin, K R; Xiang, C; Lee, T H
2012-08-01
Hysteresis, observed in many gene regulatory networks, has a pivotal impact on biological systems, which enhances the robustness of cell functions. In this paper, a general model is proposed to describe the hysteretic gene regulatory network by combining the hysteresis component and the transient dynamics. The Bouc-Wen hysteresis model is modified to describe the hysteresis component in the mammalian gene regulatory networks. Rigorous mathematical analysis on the dynamical properties of the model is presented to ensure the bounded-input-bounded-output (BIBO) stability and demonstrates that the original Bouc-Wen model can only generate a clockwise hysteresis loop while the modified model can describe both clockwise and counter clockwise hysteresis loops. Simulation studies have shown that the hysteresis loops from our model are consistent with the experimental observations in three mammalian gene regulatory networks and two E.coli gene regulatory networks, which demonstrate the ability and accuracy of the mathematical model to emulate natural gene expression behavior with hysteresis. A comparison study has also been conducted to show that this model fits the experiment data significantly better than previous ones in the literature. The successful modeling of the hysteresis in all the five hysteretic gene regulatory networks suggests that the new model has the potential to be a unified framework for modeling hysteresis in gene regulatory networks and provide better understanding of the general mechanism that drives the hysteretic function. PMID:22588784
NASA Astrophysics Data System (ADS)
Sódor, Á.; Chené, A.-N.; De Cat, P.; Bognár, Zs.; Wright, D. J.; Marois, C.; Walker, G. A. H.; Matthews, J. M.; Kallinger, T.; Rowe, J. F.; Kuschnig, R.; Guenther, D. B.; Moffat, A. F. J.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.
2014-08-01
Context. The central star of the HR 8799 system is a γ Doradus-type pulsator. The system harbours four planetary-mass companions detected by direct imaging, and is a good solar system analogue. The masses of the companions are not accurately known because the estimation depends greatly on the age of the system, which is also not known with sufficient accuracy. Asteroseismic studies of the star might help to better constrain the age of HR 8799. We organized an extensive photometric and multi-site spectroscopic observing campaign to study the pulsations of the central star. Aims: The aim of the present study is to investigate the pulsation properties of HR 8799 in detail via the ultra-precise 47 d nearly continuous photometry obtained with the Microvariability and Oscillations in STars (MOST) space telescope, and to find as many independent pulsation modes as possible, which is the prerequisite for an asteroseismic age determination. Methods: We carried out Fourier analysis of the wide-band photometric time series. Results: We find that resonance and sudden amplitude changes characterize the pulsation of HR 8799. The dominant frequency is always at f1 = 1.978 d-1.Many multiples of one-ninth of the dominant frequency appear in the Fourier spectrum of the MOST data: n/9 f1, where n = {1,2,3,4,5,6,7,8,9,10,13,14,17,18}. Our analysis also reveals that many of these peaks show strong amplitude decrease and phase variations even on the 47 d time scale. The dependencies between the pulsation frequencies of HR 8799 make the planned subsequent asteroseismic analysis rather difficult. We point out some resemblance between the light curve of HR 8799 and the modulated pulsation light curves of Blazhko RR Lyrae stars. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.
NASA Astrophysics Data System (ADS)
Jena, Ajay Kumar; Kulkarni, Ashish; Ikegami, Masashi; Miyasaka, Tsutomu
2016-03-01
Hysteresis in current-voltage curves of perovskite solar cells is a serious concern as it creates confusions about actual cell performance and raises questions on its reliability. Although a lot of effort has been made to understand the origin of hysteresis, knowing whether hysteresis affects the cell performance while they are in practical use (operated constantly at maximum power point) is not yet examined. In the present study, we investigate steady state performance and performance stability of perovskite solar cells (planar architecture with varying perovskite film thickness and TiO2 mesoscopic structure with different TiO2 compact layer thickness exhibiting hysteresis of different magnitudes) operating across an external load in relation to hysteresis. The planar cells with larger hysteresis exhibit a steady state current that closely matches the value determined on forward voltage scan. Cyclic photocurrent-dark current measurements on cells with hysteresis of different magnitudes reveal that photo-induced electrical instability (not material degradation), which might be originated from ion migration or photo-induced traps formation, is not related to hysteresis. Performance of the cells is recovered partially or fully, depending on the device structure, on storage in dark. TiO2 meso-structure cells tend to show complete recovery while the planar cells recover partially.
A simple model of hysteresis behavior using spreadsheet analysis
NASA Astrophysics Data System (ADS)
Ehrmann, A.; Blachowicz, T.
2015-01-01
Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.
Scalar and vector hysteresis simulations using HysterSoft
NASA Astrophysics Data System (ADS)
Dimian, M.; Andrei, P.
2015-02-01
Hysteresis modeling has become an important research area with many applications in science and engineering. In this article we present a unified and robust simulation framework designed to perform scalar and vector hysteresis modeling. The framework is based on HysterSoft© which is a simulation platform that can be interfaced with other libraries and simulation programs to model various aspects of hysteresis. We describe the main features of our simulation framework by focusing on scalar and vector hysteresis modeling, direct and inverse modeling, dynamic hysteresis modeling, first-order reversal-curves analysis, identification of the scalar and vector Preisach distribution function using an experimental first- order reversal-curves, noise passage analysis through hysteretic systems, and thermal relaxation in scalar and vector hysteresis. The simulation modules, the user-defined features, and various parameter identification techniques are also presented.
ERIC Educational Resources Information Center
Flanagan, Ted B., And Others
1987-01-01
This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)
Efficient Computational Model of Hysteresis
NASA Technical Reports Server (NTRS)
Shields, Joel
2005-01-01
A recently developed mathematical model of the output (displacement) versus the input (applied voltage) of a piezoelectric transducer accounts for hysteresis. For the sake of computational speed, the model is kept simple by neglecting the dynamic behavior of the transducer. Hence, the model applies to static and quasistatic displacements only. A piezoelectric transducer of the type to which the model applies is used as an actuator in a computer-based control system to effect fine position adjustments. Because the response time of the rest of such a system is usually much greater than that of a piezoelectric transducer, the model remains an acceptably close approximation for the purpose of control computations, even though the dynamics are neglected. The model (see Figure 1) represents an electrically parallel, mechanically series combination of backlash elements, each having a unique deadband width and output gain. The zeroth element in the parallel combination has zero deadband width and, hence, represents a linear component of the input/output relationship. The other elements, which have nonzero deadband widths, are used to model the nonlinear components of the hysteresis loop. The deadband widths and output gains of the elements are computed from experimental displacement-versus-voltage data. The hysteresis curve calculated by use of this model is piecewise linear beyond deadband limits.
Hysteresis in a quantized superfluid 'atomtronic' circuit.
Eckel, Stephen; Lee, Jeffrey G; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W; Lobb, Christopher J; Phillips, William D; Edwards, Mark; Campbell, Gretchen K
2014-02-13
Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits-it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose-Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices). PMID:24522597
NASA Astrophysics Data System (ADS)
Yu, Guo-An; Disse, Markus; Yu, Yang
2016-04-01
Suspended sediment dynamics of the Tarim River, an allogenic and perennial river flowing in a very arid environment in China, are analyzed to examine the hysteresis effects based on data of flow discharge (Q) and suspended sediment concentration (SSC) from two hydrologic gauging stations in the river in the last five decades (1960-2011). Strong hysteresis effects existed in the sediment rating curves of the Tarim River. Under similar flow conditions, the first flood event in a year quite often causes higher suspended sediment concentration (SSC value), and form a rating curve visibly different from later flood processes. The successive flood events often form rating curves gradually from left to right progressively with time on the SSC-Q plot, indicating that higher flow intensity is needed for later flood events to reach the same SSC value of the earlier flood events. Three hysteresis loop forms, i.e., clockwise, anti-clockwise and Figure-eight existed with occurrence frequency of 57%, 27.3% and 15.6% respectively, showing that clockwise loop is the major hysteresis form and sediment load is generally derived from the channel bed. The very weak banks due to composition of quite homogeneous noncohesive particles (fine sand, silt and almost no clay content) often induce bank failure, which complicates suspended sediment dynamics and causes to shape different hysteresis loops. Somehow random but occurrence of bank collapse with higher possibility near the peak and at the falling limb of a flood hydrograph is probably the major reason causing anti-clockwise and figure-eight hysteresis loops.
Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes
NASA Astrophysics Data System (ADS)
Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem
2014-02-01
The Gd5Ge2Si2 alloy and the off-stoichiometric Ni50Mn35In15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd5Ge2Si2 and Ni50Mn35In15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis.
Corneal hysteresis and its relevance to glaucoma
Deol, Madhvi; Taylor, David A.; Radcliffe, Nathan M.
2015-01-01
Purpose of review Glaucoma is a leading cause of irreversible blindness worldwide. It is estimated that roughly 60.5 million people had glaucoma in 2010 and that this number is increasing. Many patients continue to lose vision despite apparent disease control according to traditional risk factors. The purpose of this review is to discuss the recent findings with regard to corneal hysteresis, a variable that is thought to be associated with the risk and progression of glaucoma. Recent findings Low corneal hysteresis is associated with optic nerve and visual field damage in glaucoma and the risk of structural and functional glaucoma progression. In addition, hysteresis may enhance intraocular pressure (IOP) interpretation: low corneal hysteresis is associated with a larger magnitude of IOP reduction following various glaucoma therapies. Corneal hysteresis is dynamic and may increase in eyes after IOP-lowering interventions are implemented. Summary It is widely accepted that central corneal thickness is a predictive factor for the risk of glaucoma progression. Recent evidence shows that corneal hysteresis also provides valuable information for several aspects of glaucoma management. In fact, corneal hysteresis may be more strongly associated with glaucoma presence, risk of progression, and effectiveness of glaucoma treatments than central corneal thickness. PMID:25611166
Adhesion hysteresis of silane coated microcantilevers
DE BOER,MAARTEN P.; KNAPP,JAMES A.; MICHALSKE,TERRY A.; SRINIVASAN,U.; MABOUDIAN,R.
2000-04-17
The authors have developed a new experimental approach for measuring hysteresis in the adhesion between micromachined surfaces. By accurately modeling the deformations in cantilever beams that are subject to combined interfacial adhesion and applied electrostatic forces, they determine adhesion energies for advancing and receding contacts. They draw on this new method to examine adhesion hysteresis for silane coated micromachined structures and found significant hysteresis for surfaces that were exposed to high relative humidity (RH) conditions. Atomic force microscopy studies of these surfaces showed spontaneous formation of agglomerates that they interpreted as silages that have irreversibly transformed from uniform surface layers at low RH to isolated vesicles at high RH. They used contact deformation models to show that the compliance of these vesicles could reasonably account for the adhesion hysteresis that develops at high RH as the surfaces are forced into contact by an externally applied load.
Two-level model and magnetic field effects on the hysteresis in n-GaAs
NASA Astrophysics Data System (ADS)
Tzeng, Shwu-Yun Tsay; Tzeng, Yiharn
2004-08-01
Efforts are made in this work to interpret the experimentally observed magnetic effects on the hysteretic I-V curve for an n-GaAs semiconductor through a two-impurity-level model with the assumptions of spatial homogeneity in current flow direction and instantaneous energy balance. We construct the model by considering carefully the Landau level shifts for the electrons in the conduction band, the magnetoresistance property, and the modification on the cross sections of the impact ionization. With the inclusions of the effects from the carrier electron temperature variation and the field-dependent electron mobility, we are able to describe the hysteretic I-V characteristics satisfactorily for the case of applying either a longitudinal or a transverse magnetic field simultaneously within a single model. Our numerical results show that when the applied longitudinal magnetic field B increases, the holding voltage of the hysteresis shifts towards a higher value, while the breakdown voltage remains almost fixed and thus the width of the hysteresis decreases. Above a critical magnetic field intensity 86mT , the hysteresis vanishes. Under the transverse magnetic field, the breakdown voltage of the hysteresis shifts significantly towards the higher direction with a stronger magnetic field B , and therefore a considerably wider hysteresis width. The dynamic behavior of our model has displayed the same features of the experimental observations described by Aoki, Kondo, and Watanabe in Solid State Commun. 77, 91 (1991).
NASA Astrophysics Data System (ADS)
Johnson, David B.; Rasmussen, Roy M.
1992-12-01
The transition between wet and dry growth for graupel and hail is examined, and new figures are presented illustrating the critical water contents necessary for transitions into or out of the wet-growth regime. These figures are extended to smaller sizes and lower bulk densities than considered in previous studies. In addition, the possibility of hysteresis in the transitions is examined.
Hysteresis phenomena of the intelligent driver model for traffic flow
NASA Astrophysics Data System (ADS)
Dahui, Wang; Ziqiang, Wei; Ying, Fan
2007-07-01
We present hysteresis phenomena of the intelligent driver model for traffic flow in a circular one-lane roadway. We show that the microscopic structure of traffic flow is dependent on its initial state by plotting the fraction of congested vehicles over the density, which shows a typical hysteresis loop, and by investigating the trajectories of vehicles on the velocity-over-headway plane. We find that the trajectories of vehicles on the velocity-over-headway plane, which usually show a hysteresis loop, include multiple loops. We also point out the relations between these hysteresis loops and the congested jams or high-density clusters in traffic flow.
Transport, hysteresis and avalanches in artificial spin ice systems
Reichhardt, Charles; Reichhardt, Cynthia J; Libal, A
2010-01-01
We examine the hopping dynamics of an artificial spin ice system constructed from colloids on a kagome optical trap array where each trap has two possible states. By applying an external drive from an electric field which is analogous to a biasing applied magnetic field for real spin systems, we can create polarized states that obey the spin-ice rules of two spins in and one spin out at each vertex. We demonstrate that when we sweep the external drive and measure the fraction of the system that has been polarized, we can generate a hysteresis loop analogous to the hysteretic magnetization versus external magnetic field curves for real spin systems. The disorder in our system can be readily controlled by changing the barrier that must be overcome before a colloid can hop from one side of a trap to the other. For systems with no disorder, the effective spins all flip simultaneously as the biasing field is changed, while for strong disorder the hysteresis curves show a series of discontinuous jumps or avalanches similar to Barkhausen noise.
Magnetic hysteresis measurements of thin films under isotropic stress.
NASA Astrophysics Data System (ADS)
Holland, Patrick; Dubey, Archana; Geerts, Wilhelmus
2000-10-01
Nowadays, ferromagnetic thin films are widely applied in devices for information technology (credit cards, video recorder tapes, floppies, hard disks) and sensors (air bags, anti-breaking systems, navigation systems). Thus, with the increase in the use of magnetic media continued investigation of magnetic properties of materials is necessary to help in determining the useful properties of materials for new or improved applications. We are currently interested in studying the effect of applied external stress on Kerr hysteresis curves of thin magnetic films. The Ni and NiFe films were grown using DC magnetron sputtering with Ar as the sputter gas (pAr=4 mTorr; Tsub=55-190 C). Seed and cap layers of Ti were used on all films for adhesion and oxidation protection, respectively. A brass membrane pressure cell was designed to apply in-plane isotropic stress to thin films. In this pressure cell, gas pressure is used to deform a flexible substrate onto which a thin magnetic film has been sputtered. The curvature of the samples could be controlled by changing the gas pressure to the cell. Magneto-Optical in-plane hysteresis curves at different values of strain were measured. The results obtained show that the stress sensitivity is dependent on the film thickness. For the 500nm NiFe films, the coercivity strongly decreased as a function of the applied stress.
NASA Astrophysics Data System (ADS)
Baghel, A. P. S.; Kulkarni, S. V.
2013-01-01
Grain-oriented (GO) laminations owing to their crystalline and textured structure exhibit strong anisotropy in magnetic characteristics. GO laminations generally display highly steep, gooseneck, and narrow waist rolling direction (RD) hysteresis loops and complex-shaped transverse direction (TD) curves. The original Jiles-Atherton (JA) model needs improvisation while modeling such characteristics. The paper proposes a modified JA model for the hysteresis modeling of GO laminations with consideration of their crystalline and textured structure. The model is based on single crystal approximation of polycrystalline materials and modifies the anhysteretic magnetization on account of anisotropic energy. It takes into account the domain wall motion as well as domain magnetization rotation. The model provides a better prediction of RD hysteresis loops and also shows ability to characterize of TD hysteresis loops with reasonable accuracy. The model preserves simplicity of the original JA model.
The extrinsic hysteresis behavior of dilute binary ferrofluids.
Lin, Lihua; Li, Jian; Lin, Yueqiang; Liu, Xiaodong; Chen, Longlong; Li, Junming; Li, Decai
2014-10-01
We report on the magnetization behavior of dilute binary ferrofluids based on γ-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ・4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction φ(A) = 0.2% and B-particle volume fractions φ(B) = 0.1% and φ(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single γ-Fe(2)O(3)/Ni(2)O(3) ferrofluids with φ(A) = 0.2% and binary ferrofluids with φ(A) = 0.2% and φ(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with φ(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with φ(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system. PMID:25365919
Semi-empirical modeling of hysteresis compensation in magnetostrictive actuator
NASA Astrophysics Data System (ADS)
Ji, Ki-Hyun; Park, Hae-Jung; Park, Young-Woo; Wereley, Norman M.
2013-04-01
Hysteresis causes a delayed response to a given input in a magnetostrictive actuator (MA). It becomes critical when the MA has to be controlled in precise and real-time mode. An efficient way to compensate hysteresis must be considered. The Jiles-Atherton and Preisach models have been applied mostly in the literature, but these models need complex mathematics that makes them difficult to be applied in precise and real-time mode. Thus, this paper presents a semi-empirical model to compensate hysteresis in the MA. The idea comes from the similarity of the shapes between the hysteresis-compensated input voltage to the MA, and the output voltage of R-C circuit. The respective hysteresis-compensated input voltage and R-C circuit are expressed as polynomial and exponential equations, resulting in two closed-form equations about capacitance. One set of capacitance values for each frequency is selected by simulating the derived equations. Experiments are performed to choose one capacitance value among a set of capacitance values from simulation, based on trial-and-error. The concept of the hysteresis loss is introduced and defined as the ratio of areas between the hysteretic and reference curves. It is observed that the percent change of hysteresis loss increases as the frequency increases up to 400 Hz, but decreases with further increase of the frequency up to 800 Hz. It can be concluded that the proposed approach is effective to compensate hysteresis in the MA, and that hysteresis loss definition introduced by us can be used as a helpful measure of hysteresis compensation.
Mesoscopic magnetomechanical hysteresis in a magnetorheological elastomer
NASA Astrophysics Data System (ADS)
Biller, A. M.; Stolbov, O. V.; Raikher, Yu. L.
2015-08-01
Field-induced magnetostatic interaction in a pair of identical particles made of a magnetically soft ferromagnet is studied. It is shown that due to saturation of the ferromagnet magnetization, this case differs significantly from the (super)paramagnetic one. A numerical solution is given, discussed, and compared with that provided by a simpler model (nonlinear mutual dipoles). We show that for multidomain ferromagnetic particles embedded in an elastomer matrix, as for paramagnetic ones in the same environment, pair clusters may form or break by a hysteresis scenario. However, the magnetization saturation brings in important features to this effect. First, the bistability state and the hysteresis take place only in a limited region of the material parameters of the system. Second, along with the hysteresis jumps occurring under the sole influence of the field, the "latent" hysteresis is possible which realizes only if the action of the field is combined with some additional (nonmagnetic) external factor. The obtained conditions, when used to assess the possibility of clustering in real magnetorheological polymers, infer an important role of mesoscopic magnetomechanical hysteresis for the macroscopic properties of these composites.
Hysteresis in layered spring magnets.
Jiang, J. S.; Kaper, H. G.; Leaf, G. K.; Mathematics and Computer Science
2001-01-01
This article addresses a problem of micromagnetics: the reversal of magnetic moments in layered spring magnets. A one-dimensional model is used of a film consisting of several atomic layers of a soft material on top of several atomic layers of a hard material. Each atomic layer is taken to be uniformly magnetized, and spatial inhomogeneities within an atomic layer are neglected. The state of such a system is described by a chain of magnetic spin vectors. Each spin vector behaves like a spinning top driven locally by the effective magnetic field and subject to damping (Landau-Lifshitz-Gilbert equation). A numerical integration scheme for the LLG equation is presented that is unconditionally stable and preserves the magnitude of the magnetization vector at all times. The results of numerical investigations for a bilayer in a rotating in-plane magnetic field show hysteresis with a basic period of 2{pi} at moderate fields and hysteresis with a basic period of {pi} at strong fields.
Core hysteresis in nematic defects
NASA Astrophysics Data System (ADS)
Kralj, Samo; Virga, Epifanio G.
2002-08-01
We study field-induced transformations in the biaxial core of a nematic disclination with strength m=1, employing the Landau-de Gennes order tensor parameter Q. We first consider the transition from the defectless escaped radial structure into the structure hosting a line defect with a negative uniaxial order parameter along the axis of a cylinder of radius R. The critical field of the transition monotonically increases with R and asymptotically approaches a value corresponding to ξb/ξf~0.3, where the correlation lengths ξb and ξf are related to the biaxial order and the external field, respectively. Then, in the same geometry, we focus on the line defect structure with a positive uniaxial ordering along the axis, surrounded by the uniaxial sheath, the uniaxial cylinder of radius ξu with negative order parameter and director in the transverse direction. We study the hysteresis in the position of the uniaxial sheath upon increasing and decreasing the field strength. In general, two qualitatively different solutions exist, corresponding to the uniaxial sheath located close to the defect symmetry axis or close to the cylinder wall. This latter solution exists only for strong enough anchorings. The uniaxial sheath is for a line defect what the uniaxial ring is for a point defect: by resorting to an approximate analytic estimate, we show that essentially the same hysteresis exhibited by the uniaxial sheath is expected to occur at the uniaxial ring in the core structure of a point defect.
Predictability of magnetic hysteresis and thermoremanent magnetization using Preisach theory
NASA Astrophysics Data System (ADS)
Newell, A. J.; Niemerg, M.; Bates, D.
2014-12-01
Preisach theory is a phenomenological model of hysteresis that is the basis for FORC analysis in rock magnetism. In FORC analysis, a system is characterized using first-order reversal curves (FORCs), each of which is a magnetization curve after a reversal in the direction of change of the magnetic field. Preisach theory uses the same curves to predict the magnetic response to changes in the magnetic field. In rock magnetism, the Preisach model has been adapted to predict general properties of thermoremanent magnetization (TRM), and even to inferpaleointensity from room-temperature FORCs. Preisach theory represents hysteresis by a collection of hysteresis units called hysterons; the distribution of hysterons is inferred from FORC measurements. Each hysteron represents a two-state system. This is similar to a single-domain (SD) magnet, but the first-order theory cannot represent the magnetism of a simple system of randomly oriented SD magnets. Such a system can be represented by a second-order Preisach theory, which requires the measurement of magnetization curves after two reversals of the direction of change. One can generalize this process to higher order reversal curves, although each increase in the number of reversals greatly increases the number of measurements that are needed. The magnetic hysteresis of systems of interacting SD magnets is calculated using numerical homotopy, a method that can find all the solutions of the equilibrium equations for such a system. The hysteresis frequently has features that cannot be represented by any order of Preisach theory. Furthermore, there are stable magnetic states that are not reachable during isothermal hysteresis unless thermal fluctuations are large enough. Such states would not be visible at room temperature but would contribute to TRM.
Hysteresis, thermomagnetic, and low-temperature magnetic properties of Southwestern U.S. obsidians
NASA Astrophysics Data System (ADS)
Sternberg, R. S.; Jackson, M. J.; Shackley, M. S.
2011-12-01
Geochemical signatures of Southwestern U.S. obsidians have been intensively studied, in part to use as a provenance method for archaeological obsidians (Shackley, 2005). We reported (Sternberg et al. 2010) examined magnetic properties of 50 unoriented samples from 10 geologic obsidian sources in Arizona, Nevada, and New Mexico; here we provide additional results measured at the Institute for Rock magnetism. Room-temperature hysteresis curves were measured using a vibrating sample magnetometer on 58 specimens from all 50 samples. The Quantum Designs Magnetic Properties Measurement System was used to measure low temperature cycling of the natural remanence and/or of a room-temperature saturation isothermal remanence for 10 specimens, and frequency dependence of susceptibility for 7 specimens. A Princeton VSM was used to measure hysteresis curves and thermomagnetic curves for 19 specimens from 17 samples. Eleven of the thermomagnetic curves show Curie temperatures close to that for magnetite, and most of them are almost perfectly reversible. Many of the specimens also show a less well-defined Curie point around 150-200°C; for a few specimens the thermomagnetic behavior is dominated by paramagnetic iron and no ferromagnetic phases can be identified. The low-temperature remanence and susceptibility measurements show the magnetite Verwey transition in almost all specimens, and a significant superparamagnetic presence in only a few cases. Hysteresis parameters plot mainly in the lower half of the PSD domain on a Day plot, and saturation magnetization values indicate magnetite concentrations of about 0.2% to 0.5% for most specimens. The coercivity of remanence decreased considerably for one specimen after surface cleaning, although for 5 other comparisons there was no change.
NASA Technical Reports Server (NTRS)
Cunningham, A. M., Jr.
1986-01-01
An experimental study was conducted to quantify the hysteresis associated with various vortex flow transition points and to determine the effect of planform geometry. The transition points observed consisted of the appearance (or disappearance) of trailing edge vortex burst and the transition to (or from) flat plate or totally separated flows. Flow visualization with smoke injected into the vortices was used to identify the transitions on a series of semi-span models tested in a low speed tunnel. The planforms tested included simple deltas (55 deg to 80 deg sweep), cranked wings with varying tip panel sweep and dihedral, and a straked wing. High speed movies at 1000 frames per second were made of the vortex flow visualization in order to better understand the dynamics of vortex flow, burst and transition.
Hysteresis multicycles in nanomagnet arrays.
Deutsch, J M; Mai, Trieu; Narayan, Onuttom
2005-02-01
We predict two physical effects in arrays of single-domain nanomagnets by performing simulations using a realistic model Hamiltonian and physical parameters. First, we find hysteretic multicycles for such nanomagnets. The simulation uses continuous spin dynamics through the Landau-Lifshitz-Gilbert (LLG) equation. In some regions of parameter space, the probability of finding a multicycle is as high as approximately 0.6 . We find that systems with larger and more anisotropic nanomagnets tend to display more multicycles. Our results also demonstrate the importance of disorder and frustration for multicycle behavior. Second, we show that there is a fundamental difference between the more realistic vector LLG equation and scalar models of hysteresis, such as Ising models. In the latter case spin and external field inversion symmetry is obeyed, but in the former it is destroyed by the dynamics, with important experimental implications. PMID:15783391
Electroosmotic flow hysteresis for dissimilar ionic solutions.
Lim, An Eng; Lim, Chun Yee; Lam, Yee Cheong
2015-03-01
Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species. PMID:25945139
Electroosmotic flow hysteresis for dissimilar ionic solutions
Lim, An Eng; Lam, Yee Cheong
2015-01-01
Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species. PMID:25945139
Macroscopic theory for capillary-pressure hysteresis.
Athukorallage, Bhagya; Aulisa, Eugenio; Iyer, Ram; Zhang, Larry
2015-03-01
In this article, we present a theory of macroscopic contact angle hysteresis by considering the minimization of the Helmholtz free energy of a solid-liquid-gas system over a convex set, subject to a constant volume constraint. The liquid and solid surfaces in contact are assumed to adhere weakly to each other, causing the interfacial energy to be set-valued. A simple calculus of variations argument for the minimization of the Helmholtz energy leads to the Young-Laplace equation for the drop surface in contact with the gas and a variational inequality that yields contact angle hysteresis for advancing/receding flow. We also show that the Young-Laplace equation with a Dirichlet boundary condition together with the variational inequality yields a basic hysteresis operator that describes the relationship between capillary pressure and volume. We validate the theory using results from the experiment for a sessile macroscopic drop. Although the capillary effect is a complex phenomenon even for a droplet as various points along the contact line might be pinned, the capillary pressure and volume of the drop are scalar variables that encapsulate the global quasistatic energy information for the entire droplet. Studying the capillary pressure versus volume relationship greatly simplifies the understanding and modeling of the phenomenon just as scalar magnetic hysteresis graphs greatly aided the modeling of devices with magnetic materials. PMID:25646688
The significance of observed rotational magnetic hysteresis in lunar samples
NASA Technical Reports Server (NTRS)
Wasilewski, P.
1974-01-01
Rotational magnetic hysteresis curves for lunar soils 10084, 12070, and 14259, and rock 14053 have been published. There is no adequate explanation to date for the observed large hysteresis at high fields. Lunar rock magnetism researchers consider fine particle iron to be the primary source of stable magnetic remanence in lunar samples. Iron has cubic anisotropy with added shape anisotropy for extreme particle shapes. The observed high-field hysteresis must have its source in uniaxial or unidirectional anisotropy. This implies the existence of minerals with uniaxial anisotropy or exchange-coupled spin states. Therefore, the source of this observed high-field hysteresis must be identified and understood before serious paleointensity studies are made. It is probable that the exchange-coupled spin states and/or the source of uniaxial anisotropy responsible for the high-field hysteresis might be influenced by the lunar surface diurnal temperature cycling. The possible sources of high-field hysteresis in lunar samples are presented and considered.
NASA Astrophysics Data System (ADS)
Hamimid, M.; Mimoune, S. M.; Feliachi, M.
2012-07-01
In this present work, the minor hysteresis loops model based on parameters scaling of the modified Jiles-Atherton model is evaluated by using judicious expressions. These expressions give the minor hysteresis loops parameters as a function of the major hysteresis loop ones. They have exponential form and are obtained by parameters identification using the stochastic optimization method “simulated annealing”. The main parameters influencing the data fitting are three parameters, the pinning parameter k, the mean filed parameter α and the parameter which characterizes the shape of anhysteretic magnetization curve a. To validate this model, calculated minor hysteresis loops are compared with measured ones and good agreements are obtained.
Conductance hysteresis in the voltage-dependent anion channel.
Rappaport, Shay M; Teijido, Oscar; Hoogerheide, David P; Rostovtseva, Tatiana K; Berezhkovskii, Alexander M; Bezrukov, Sergey M
2015-09-01
Hysteresis in the conductance of voltage-sensitive ion channels is observed when the transmembrane voltage is periodically varied with time. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, because the focus was solely on the channel opening branches of the hysteresis loops. We studied the hysteretic response of a multichannel VDAC system to a triangular voltage ramp the frequency of which was varied over three orders of magnitude, from 0.5 mHz to 0.2 Hz. We found that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, suggesting broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, quasi-equilibrium two-state behavior is observed for hysteresis branches corresponding to VDAC opening. This enables calculation of the usual equilibrium gating parameters, gating charge and voltage of equipartitioning, which were found to be almost insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, and, in the opening branch, follows quasi-equilibrium paths. PMID:26094068
Ac magnetorestriction hysteresis and magnetization direction in grain oriented silicon steels
Mogi, Hisashi; Matsuo, Yukio; Kumano, Tomoji
1999-09-01
A hysteresis curve of ac magnetostriction was measured, magnetizing a grain oriented silicon steel in the direction deviated from rolling direction of a sample. The ac magnetostriction ({lambda} ac) curves were analyzed as harmonics in the interest of noise spectrum of such as a power transformer. The domain structure model in this magnetostriction process was proposed. The hysteresis was large in the magnetization direction inclined at 30 and 90{degree} from the rolling direction.
Mach, methodology, hysteresis and economics
NASA Astrophysics Data System (ADS)
Cross, R.
2008-11-01
This methodological note examines the epistemological foundations of hysteresis with particular reference to applications to economic systems. The economy principles of Ernst Mach are advocated and used in this assessment.
Hysteresis of boiling for different tunnel-pore surfaces
NASA Astrophysics Data System (ADS)
Pastuszko, Robert; Piasecka, Magdalena
2015-05-01
Analysis of boiling hysteresis on structured surfaces covered with perforated foil is proposed. Hysteresis is an adverse phenomenon, preventing high heat flux systems from thermal stabilization, characterized by a boiling curve variation at an increase and decrease of heat flux density. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins covered with the copper wire net (NTS-L). The experiments were carried out with water, R-123 and FC-72 at atmospheric pressure. A detailed analysis of the measurement results identified several cases of type I, II and III for TS, NTS and NTS-L surfaces.
Mastering hysteresis in magnetocaloric materials.
Gutfleisch, O; Gottschall, T; Fries, M; Benke, D; Radulov, I; Skokov, K P; Wende, H; Gruner, M; Acet, M; Entel, P; Farle, M
2016-08-13
Hysteresis is more than just an interesting oddity that occurs in materials with a first-order transition. It is a real obstacle on the path from existing laboratory-scale prototypes of magnetic refrigerators towards commercialization of this potentially disruptive cooling technology. Indeed, the reversibility of the magnetocaloric effect, being essential for magnetic heat pumps, strongly depends on the width of the thermal hysteresis and, therefore, it is necessary to understand the mechanisms causing hysteresis and to find solutions to minimize losses associated with thermal hysteresis in order to maximize the efficiency of magnetic cooling devices. In this work, we discuss the fundamental aspects that can contribute to thermal hysteresis and the strategies that we are developing to at least partially overcome the hysteresis problem in some selected classes of magnetocaloric materials with large application potential. In doing so, we refer to the most relevant classes of magnetic refrigerants La-Fe-Si-, Heusler- and Fe2P-type compounds.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402928
High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects
NASA Astrophysics Data System (ADS)
Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong
2009-08-01
A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.
Effect of Hysteresis on Measurements of Thin-Film Cell Performance
Albin, D.; del Cueto, J.
2011-03-01
Transient or hysteresis effects in polycrystalline thin film CdS/CdTe cells are a function of pre-measurement voltage bias and whether Cu is introduced as an intentional dopant during back contact fabrication. When Cu is added, the current-density (J) vs. voltage (V) measurements performed in a reverse-to-forward voltage direction will yield higher open-circuit voltage (Voc), up to 10 mV, and smaller short-circuit current density (Jsc), by up to 2 mA/cm2, relative to scanning voltage in a forward-to-reverse direction. The variation at the maximum power point, Pmax, is however small. The resulting variation in FF can be as large as 3%. When Cu is not added, hysteresis in both Voc and Jsc is negligible however Pmax hysteresis is considerably greater. This behavior corroborates observed changes in depletion width, Wd, derived from capacitance (C) vs voltage (V) scans. Measured values of Wd are always smaller in reverse-to-forward voltage scans, and conversely, larger in the forward-to-reverse voltage direction. Transient ion drift (TID) measurements performed on Cu-containing cells do not show ionic behavior suggesting that capacitance transients are more likely due to electronic capture-emission processes. J-V curve simulation using Pspice shows that increased transient capacitance during light-soak stress at 100 degrees C correlates with increased space-charge recombination. Voltage-dependent collection however was not observed to increase with stress in these cells.
Hysteresis modeling in ballistic carbon nanotube field-effect transistors.
Liu, Yian; Moura, Mateus S; Costa, Ademir J; de Almeida, Luiz Alberto L; Paranjape, Makarand; Fontana, Marcio
2014-01-01
Theoretical models are adapted to describe the hysteresis effects seen in the electrical characteristics of carbon nanotube field-effect transistors. The ballistic transport model describes the contributions of conduction energy sub-bands over carbon nanotube field-effect transistor drain current as a function of drain-source and gate-source voltages as well as other physical parameters of the device. The limiting-loop proximity model, originally developed to understand magnetic hysteresis, is also utilized in this work. The curves obtained from our developed model corroborate well with the experimentally derived hysteretic behavior of the transistors. Modeling the hysteresis behavior will enable designers to reliably use these effects in both analog and memory applications. PMID:25187698
Hysteresis modeling in ballistic carbon nanotube field-effect transistors
Liu, Yian; Moura, Mateus S; Costa, Ademir J; de Almeida, Luiz Alberto L; Paranjape, Makarand; Fontana, Marcio
2014-01-01
Theoretical models are adapted to describe the hysteresis effects seen in the electrical characteristics of carbon nanotube field-effect transistors. The ballistic transport model describes the contributions of conduction energy sub-bands over carbon nanotube field-effect transistor drain current as a function of drain-source and gate-source voltages as well as other physical parameters of the device. The limiting-loop proximity model, originally developed to understand magnetic hysteresis, is also utilized in this work. The curves obtained from our developed model corroborate well with the experimentally derived hysteretic behavior of the transistors. Modeling the hysteresis behavior will enable designers to reliably use these effects in both analog and memory applications. PMID:25187698
Thermal-expansion hysteresis in graphite/glass composites
Janas, V.F.
1988-07-01
The thermal-expansion hysteresis phenomena in graphite/glass composites was studied. Neat (unfilled) glass and unidirectional composites showed no observable hysteresis, while (0/90) cross-ply composites showed significant residual thermal strain (approx. 20 PPM) after thermal cycling (25 ..-->.. 150 ..-->.. 25/sup 0/C). Multiple thermal cycling of the composite and the strengthening of the fiber/matrix bond were found to greatly reduce the magnitude of the residual thermal strain. Bond strengthening also weakened and embrittled the composite, supporting a fiber-slippage mechanism for hysteresis. Thermal precycling and interface modification are proposed as methods of diminishing the effects of thermal-expansion hysteresis. 11 references, 6 figures, 4 tables.
The intrinsic origin of hysteresis in MoS2 field effect transistors
NASA Astrophysics Data System (ADS)
Shu, Jiapei; Wu, Gongtao; Guo, Yao; Liu, Bo; Wei, Xianlong; Chen, Qing
2016-01-01
We investigate the hysteresis and gate voltage stress effect in MoS2 field effect transistors (FETs). We observe that both the suspended and the SiO2-supported FETs have large hysteresis in their transfer curves under vacuum which cannot be attributed to the traps at the interface between the MoS2 and the SiO2 or in the SiO2 substrate or the gas adsorption/desorption effect. Our findings indicate that the hysteresis we observe comes from the MoS2 itself, revealing an intrinsic origin of the hysteresis besides some extrinsic factors. The fact that the FETs based on thinner MoS2 have larger hysteresis than that with thicker MoS2 suggests that the surface of MoS2 plays a key role in the hysteresis. The gate voltage sweep range, sweep direction, sweep time and loading history all affect the hysteresis observed in the transfer curves.We investigate the hysteresis and gate voltage stress effect in MoS2 field effect transistors (FETs). We observe that both the suspended and the SiO2-supported FETs have large hysteresis in their transfer curves under vacuum which cannot be attributed to the traps at the interface between the MoS2 and the SiO2 or in the SiO2 substrate or the gas adsorption/desorption effect. Our findings indicate that the hysteresis we observe comes from the MoS2 itself, revealing an intrinsic origin of the hysteresis besides some extrinsic factors. The fact that the FETs based on thinner MoS2 have larger hysteresis than that with thicker MoS2 suggests that the surface of MoS2 plays a key role in the hysteresis. The gate voltage sweep range, sweep direction, sweep time and loading history all affect the hysteresis observed in the transfer curves. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07336g
Hysteresis Analysis Based on the Ferroelectric Effect in Hybrid Perovskite Solar Cells.
Wei, Jing; Zhao, Yicheng; Li, Heng; Li, Guobao; Pan, Jinlong; Xu, Dongsheng; Zhao, Qing; Yu, Dapeng
2014-11-01
The power conversion efficiency (PCE) of CH3NH3PbX3 (X = I, Br, Cl) perovskite solar cells has been developed rapidly from 6.5 to 18% within 3 years. However, the anomalous hysteresis found in I-V measurements can cause an inaccurate estimation of the efficiency. We attribute the phenomena to the ferroelectric effect and build a model based on the ferroelectric diode to explain it. The ferroelectric effect of CH3NH3PbI3-xClx is strongly suggested by characterization methods and the E-P (electrical field-polarization) loop. The hysteresis in I-V curves is found to greatly depend on the scan range as well as the velocity, which is well explained by the ferroelectric diode model. We also find that the current signals show exponential decay in ∼10 s under prolonged stepwise measurements, and the anomalous hysteresis disappears using these stabilized current values. The experimental results accord well with the model based on ferroelectric properties and prove that prolonged stepwise measurement is an effective way to evaluate the real efficiency of perovskite solar cells. Most importantly, this work provides a meaningful perspective that the ferroelectric effect (if it really exists) should be paid special attention in the optimization of perovskite solar cells. PMID:26278773
Protonated polynucleotides structures - 23. The acid-base hysteresis of poly(dG).poly(dC).
Thiele, D; Marck, C; Schneider, C; Guschlbauer, W
1978-01-01
The large hysteresis observed during the acid-base titration of poly(dG). poly (dC) was studied by CD and potentiometric scanning curves. Intermediate scanning loops as well as the equilibrium and metastable branches of the hysteresis loop have been determined. The potentiometric titrations showed, however, that the various complexes were not discrete entities, but were linked in "polycomplexes" as had been already suggested. This prevented a thermodynamic study of the system. The acid-base titration was further investigated as a function of ionic strength and temperature. The pK's showed considerably lower ionic strength dependence than observed for polyribonucleotide complexes. The thermal transitions permitted to establish the relative stabilities of the various complexes between pH 2.5 and pH 12.0. PMID:27762
Applications of a theory of ferromagnetic hysteresis
NASA Astrophysics Data System (ADS)
Hodgdon, M. L.
The differential equation dB/dt = alpha times the absolute value of dH/dt (f(H) - B) + dH/dt g(H) and a set of restrictions on the material functions f and g yield a theory of rate independent hysteresis for isoperm ferromagnetic materials. A modification based on exchanging the positions of B and H in the differential equation and on allowing for the dependence of the material functions on dH/dt extends the theory to rate dependent, nonisoperm materials. The theory and its extension exhibit all of the important features of ferromagnetic hysteresis, including the existence and stability of minor loops. Both are well suited for use in numerical field solving codes. Examples in which the material functions are simple combinations of analytic functions are presented here for Mn-Zn ferrite, Permalloy, CMD5005, and CoCr thin film. Also presented is a procedure for constructing a two dimensional vector model that yields bell-shaped and M-shaped curves for graphs of the angular variation of the coercive field.
Residual stresses and vector hysteresis modeling
NASA Astrophysics Data System (ADS)
Ktena, Aphrodite
2016-04-01
Residual stresses in magnetic materials, whether the result of processing or intentional loading, leave their footprint on macroscopic data, such hysteresis loops and differential permeability measurements. A Preisach-type vector model is used to reproduce the phenomenology observed based on assumptions deduced from the data: internal stresses lead to smaller and misaligned grains, hence increased domain wall pinning and angular dispersion of local easy axes, favouring rotation as a magnetization reversal mechanism; misaligned grains contribute to magnetostatic fields opposing the direction of the applied field. The model is using a vector operator which accounts for both reversible and irreversible processes; the Preisach concept for interactions for the role of stress related demagnetizing fields; and a characteristic probability density function which is constructed as a weighed sum of constituent functions: the material is modeled as consisting of various subsystems, e.g. reversal mechanisms or areas subject to strong/weak long range interactions and each subsystem is represented by a constituent probability density function. Our assumptions are validated since the model reproduces the hysteresis loops and differential permeability curves observed experimentally and calculations involving rotating inputs at various residual stress levels are consistent and in agreement with experimental evidence.
Dynamic Hysteresis in Compacted Magnetic Nanoparticles
NASA Astrophysics Data System (ADS)
Chowdary, Krishna M.
The frequency and temperature dependent magnetic response of a bulk soft magnetic nanocomposite made by compacting Fe10Co 90 nanoparticles was measured and modeled. Electron microscopy and x-ray diffraction were used to characterize the size, composition, and structure of the nanoparticles and nanocomposite. Polyol synthesis was used to produce 200 nm particles with average grain size 20 nm and large superparamagnetic fraction. The nanoparticles were consolidated to 90% theoretical density by plasma pressure compaction. The compacted nanoparticles retained the 20 nm average grain size and large superparamagnetic fraction. The nanocomposite resistivity was more than three times that of the bulk alloy. Vibrating sample and SQUID-MPMS magnetometers were used for low frequency magnetic measurements of the nanoparticles and nanocomposite. Compaction reduced the coercivity from 175 Oe to 8 Oe and the effective anisotropy from 124 x 10 3 ergs/cc to 7.9 x 103 ergs/cc. These reductions were caused by increased exchange coupling between surface nanograins, consistent with predictions from the Random Anisotropy model. Varying degrees of exchange coupling existed within the nanocomposite, contributing to a distribution of energy barriers. A permeameter was used for frequency dependent magnetic measurements on a toroid cut from the nanocomposite. Complex permeability, coercivity, and power loss were extracted from dynamic minor hysteresis loops measured over a range of temperatures (77 K - 873 K) and frequencies (0.1 kHz - 100 kHz). The real and imaginary parts of the complex permeability spectrum showed asymmetries consistent with a distribution of energy barriers and high damping. When the complex permeability, power loss, and coercivity were scaled relative to the peak frequency of the imaginary permeability, all fell on universal curves. Various microscopic and macroscopic models for the complex permeability were investigated. The complex permeability was successfully fit
Revisiting the hysteresis effect in surface energy budgets
NASA Astrophysics Data System (ADS)
Sun, Ting; Wang, Zhi-Hua; Ni, Guang-Heng
2013-05-01
The hysteresis effect in diurnal cycles of net radiation Rn and ground heat flux G0 has been observed in many studies, while the governing mechanism remains vague. In this study, we link the phenomenology of hysteresis loops to the wave phase difference between the diurnal evolutions of various terms in the surface energy balance. Rn and G0 are parameterized with the incoming solar radiation and the surface temperature as two control parameters of the surface energy partitioning. The theoretical analysis shows that the vertical water flux W and the scaled ratio As*>/AT* (net shortwave radiation to outgoing longwave radiation) play crucial roles in shaping hysteresis loops of Rn and G0. Comparisons to field measurements indicate that hysteresis loops for different land covers can be well captured by the theoretical model, which is also consistent with Camuffo-Bernadi formula. This study provides insight into the surface partitioning and temporal evolution of the energy budget at the land surface.
A New Model Based on Adaptation of the External Loop to Compensate the Hysteresis of Tactile Sensors
Sánchez-Durán, José A.; Vidal-Verdú, Fernando; Oballe-Peinado, Óscar; Castellanos-Ramos, Julián; Hidalgo-López, José A.
2015-01-01
This paper presents a novel method to compensate for hysteresis nonlinearities observed in the response of a tactile sensor. The External Loop Adaptation Method (ELAM) performs a piecewise linear mapping of the experimentally measured external curves of the hysteresis loop to obtain all possible internal cycles. The optimal division of the input interval where the curve is approximated is provided by the error minimization algorithm. This process is carried out off line and provides parameters to compute the split point in real time. A different linear transformation is then performed at the left and right of this point and a more precise fitting is achieved. The models obtained with the ELAM method are compared with those obtained from three other approaches. The results show that the ELAM method achieves a more accurate fitting. Moreover, the involved mathematical operations are simpler and therefore easier to implement in devices such as Field Programmable Gate Array (FPGAs) for real time applications. Furthermore, the method needs to identify fewer parameters and requires no previous selection process of operators or functions. Finally, the method can be applied to other sensors or actuators with complex hysteresis loop shapes. PMID:26501279
Sánchez-Durán, José A; Vidal-Verdú, Fernando; Oballe-Peinado, Óscar; Castellanos-Ramos, Julián; Hidalgo-López, José A
2015-01-01
This paper presents a novel method to compensate for hysteresis nonlinearities observed in the response of a tactile sensor. The External Loop Adaptation Method (ELAM) performs a piecewise linear mapping of the experimentally measured external curves of the hysteresis loop to obtain all possible internal cycles. The optimal division of the input interval where the curve is approximated is provided by the error minimization algorithm. This process is carried out off line and provides parameters to compute the split point in real time. A different linear transformation is then performed at the left and right of this point and a more precise fitting is achieved. The models obtained with the ELAM method are compared with those obtained from three other approaches. The results show that the ELAM method achieves a more accurate fitting. Moreover, the involved mathematical operations are simpler and therefore easier to implement in devices such as Field Programmable Gate Array (FPGAs) for real time applications. Furthermore, the method needs to identify fewer parameters and requires no previous selection process of operators or functions. Finally, the method can be applied to other sensors or actuators with complex hysteresis loop shapes. PMID:26501279
Hysteresis in rotation magnetic field
NASA Astrophysics Data System (ADS)
Ivanyi, Amalia
2000-01-01
The different properties of the vector Jiles-Atherton hysteresis operator is proved under forced H- and B-field supply. Feeding the magnetic material with alternating and circular polarised rotational excitation, the different properties of the model under the input field intensity and the flux density are investigated and the results are proved in figures.
Nonlinear diffusion and superconducting hysteresis
Mayergoyz, I.D.
1996-12-31
Nonlinear diffusion of electromagnetic fields in superconductors with ideal and gradual resistive transitions is studied. Analytical results obtained for linear and nonlinear polarizations of electromagnetic fields are reported. These results lead to various extensions of the critical state model for superconducting hysteresis.
Hysteresis in quartz resonators-a review.
Kusters, J A; Vig, J R
1991-01-01
The literature on the frequency versus temperature characteristics of quartz crystal resonators is reviewed. Three papers that deal with frequency versus pressure hysteresis are included, as these may possibly have relevance to frequency versus temperature hysteresis. It is seen that the causes of hysteresis are not well understood. The evidence to date is inconclusive. The mechanisms that can cause hysteresis include: strain changes changes in the quartz, contamination redistribution, oscillator circuitry hysteresis, and apparent hysteresis due to thermal gradients. The results to date seem to indicate that lattice defects are somehow related to thermal hysteresis. Stress relief in the mounting structure can also produce significant hysteresis. As crystal processing techniques have improved. contamination has become less of a problem. PMID:18267585
Bistability and hysteresis of annular impinging jets
NASA Astrophysics Data System (ADS)
Tisovsky, Tomas
2016-06-01
In present study, the bistability and hysteresis of annular impinging jets is investigated. Annular impinging jets are simulated using open source CFD code - OpenFOAM. Both flow field patterns of interest are obtained and hysteresis is found by means of dynamic mesh simulation. Effect of nozzle exit velocity on resulting hysteresis loop is also illustrated.
The intrinsic origin of hysteresis in MoS2 field effect transistors.
Shu, Jiapei; Wu, Gongtao; Guo, Yao; Liu, Bo; Wei, Xianlong; Chen, Qing
2016-02-01
We investigate the hysteresis and gate voltage stress effect in MoS2 field effect transistors (FETs). We observe that both the suspended and the SiO2-supported FETs have large hysteresis in their transfer curves under vacuum which cannot be attributed to the traps at the interface between the MoS2 and the SiO2 or in the SiO2 substrate or the gas adsorption/desorption effect. Our findings indicate that the hysteresis we observe comes from the MoS2 itself, revealing an intrinsic origin of the hysteresis besides some extrinsic factors. The fact that the FETs based on thinner MoS2 have larger hysteresis than that with thicker MoS2 suggests that the surface of MoS2 plays a key role in the hysteresis. The gate voltage sweep range, sweep direction, sweep time and loading history all affect the hysteresis observed in the transfer curves. PMID:26782750
Incorporation of Hysteresis Effects into Magnetc Finite Element Modeling
NASA Astrophysics Data System (ADS)
Lee, J. Y.; Lee, S. J.; Melikhov, Y.; Jiles, D. C.; Garton, M.; Lopez, R.; Brasche, L.
2004-02-01
Hysteresis effects have usually been ignored in magnetic modeling due to the multi-valued property causing difficulty in its incorporation into numerical calculations such as those based on finite elements. A linear approximation of magnetic permeability or a nonlinear B-H curve formed by connecting the tips of the hysteresis loops has been widely used in magnetic modeling for these types of calculations. We have employed the Jiles-Atherton (J-A) hysteresis model for development of a finite element method algorithm incorporating hysteresis effects. J-A model is suited for numerical analysis such as finite element modeling because of the small number of degrees of freedom and its simple form of equation. A finite element method algorithm for hysteretic materials has been developed for estimation of the volume and the distribution of retained magnetic particles around a defect site. The volume of retained magnetic particles was found to depend not only on the existing current source strength but also on the remaining magnetization of a hysteretic material. Detailed algorithm and simulation results are presented.
Wetting hysteresis induced by nanodefects.
Giacomello, Alberto; Schimmele, Lothar; Dietrich, Siegfried
2016-01-19
Wetting of actual surfaces involves diverse hysteretic phenomena stemming from ever-present imperfections. Here, we clarify the origin of wetting hysteresis for a liquid front advancing or receding across an isolated defect of nanometric size. Various kinds of chemical and topographical nanodefects, which represent salient features of actual heterogeneous surfaces, are investigated. The most probable wetting path across surface heterogeneities is identified by combining, within an innovative approach, microscopic classical density functional theory and the string method devised for the study of rare events. The computed rugged free-energy landscape demonstrates that hysteresis emerges as a consequence of metastable pinning of the liquid front at the defects; the barriers for thermally activated defect crossing, the pinning force, and hysteresis are quantified and related to the geometry and chemistry of the defects allowing for the occurrence of nanoscopic effects. The main result of our calculations is that even weak nanoscale defects, which are difficult to characterize in generic microfluidic experiments, can be the source of a plethora of hysteretical phenomena, including the pinning of nanobubbles. PMID:26721395
Wetting hysteresis induced by nanodefects
Giacomello, Alberto; Schimmele, Lothar; Dietrich, Siegfried
2016-01-01
Wetting of actual surfaces involves diverse hysteretic phenomena stemming from ever-present imperfections. Here, we clarify the origin of wetting hysteresis for a liquid front advancing or receding across an isolated defect of nanometric size. Various kinds of chemical and topographical nanodefects, which represent salient features of actual heterogeneous surfaces, are investigated. The most probable wetting path across surface heterogeneities is identified by combining, within an innovative approach, microscopic classical density functional theory and the string method devised for the study of rare events. The computed rugged free-energy landscape demonstrates that hysteresis emerges as a consequence of metastable pinning of the liquid front at the defects; the barriers for thermally activated defect crossing, the pinning force, and hysteresis are quantified and related to the geometry and chemistry of the defects allowing for the occurrence of nanoscopic effects. The main result of our calculations is that even weak nanoscale defects, which are difficult to characterize in generic microfluidic experiments, can be the source of a plethora of hysteretical phenomena, including the pinning of nanobubbles. PMID:26721395
Hysteresis in Pressure-Driven DNA Denaturation
Hernández-Lemus, Enrique; Nicasio-Collazo, Luz Adriana; Castañeda-Priego, Ramón
2012-01-01
In the past, a great deal of attention has been drawn to thermal driven denaturation processes. In recent years, however, the discovery of stress-induced denaturation, observed at the one-molecule level, has revealed new insights into the complex phenomena involved in the thermo-mechanics of DNA function. Understanding the effect of local pressure variations in DNA stability is thus an appealing topic. Such processes as cellular stress, dehydration, and changes in the ionic strength of the medium could explain local pressure changes that will affect the molecular mechanics of DNA and hence its stability. In this work, a theory that accounts for hysteresis in pressure-driven DNA denaturation is proposed. We here combine an irreversible thermodynamic approach with an equation of state based on the Poisson-Boltzmann cell model. The latter one provides a good description of the osmotic pressure over a wide range of DNA concentrations. The resulting theoretical framework predicts, in general, the process of denaturation and, in particular, hysteresis curves for a DNA sequence in terms of system parameters such as salt concentration, density of DNA molecules and temperature in addition to structural and configurational states of DNA. Furthermore, this formalism can be naturally extended to more complex situations, for example, in cases where the host medium is made up of asymmetric salts or in the description of the (helical-like) charge distribution along the DNA molecule. Moreover, since this study incorporates the effect of pressure through a thermodynamic analysis, much of what is known from temperature-driven experiments will shed light on the pressure-induced melting issue. PMID:22496765
ERIC Educational Resources Information Center
Rousseau, Ronald
1994-01-01
Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)
Lee, J.H.; Hyun, D.S. . Dept. of Electrical Engineering)
1999-05-01
In high speed applications of PMASynRM, hysteresis losses can become the major cause of power dissipation. Therefore, whereas in other kind of machines a rough estimation of hysteresis can be accepted, their importance in PMASynRM justifies a greater effort in calculating them more precisely. This study investigates the hysteresis phenomena of the Permanent Magnet Assisted Synchronous Reluctance Motor (PMASynRM) using coupled FEM and Preisach modelling. Preisach's model, which allows accurate prediction of hysteresis, is adopted in this procedure to provide a nonlinear solution. The computer simulation and experimental result for the i-[lambda] loci show the propriety of the proposed method.
Magnetic hysteresis based on dipolar interactions in granular magnetic systems
NASA Astrophysics Data System (ADS)
Allia, Paolo; Coisson, Marco; Knobel, Marcelo; Tiberto, Paola; Vinai, Franco
1999-11-01
The magnetic hysteresis of granular magnetic systems is investigated in the high-temperature limit (T>> blocking temperature of magnetic nanoparticles). Measurements of magnetization curves have been performed at room temperature on various samples of granular bimetallic alloys of the family Cu100-xCox (x=5-20 at. %) obtained in ribbon form by planar flow casting in a controlled atmosphere, and submitted to different thermal treatments. The loop amplitude and shape, which are functions of sample composition and thermal history, are studied taking advantage of a novel method of graphical representation, particularly apt to emphasize the features of thin, elongated loops. The hysteresis is explained in terms of the effect of magnetic interactions of the dipolar type among magnetic-metal particles, acting to hinder the response of the system of moments to isothermal changes of the applied field. Such a property is accounted for in a mean-field scheme, by introducing a memory term in the argument of the Langevin function which describes the anhysteretic behavior of an assembly of noninteracting superparamagnetic particles. The rms field arising from the cumulative effect of dipolar interactions is linked by the theory to a measurable quantity, the reduced remanence of a major symmetric hysteresis loop. The theory's self-consistence and adequacy have been properly tested at room temperature on all examined systems. The agreement with experimental results is always striking, indicating that at high temperatures the magnetic hysteresis of granular systems is dominated by interparticle, rather than single-particle, effects. Dipolar interactions seem to fully determine the magnetic hysteresis in the high-temperature limit for low Co content (x<=10). For higher concentrations of magnetic metal, the experimental results indicate that additional hysteretic mechanisms have to be introduced.
Implicit dose-response curves.
Pérez Millán, Mercedes; Dickenstein, Alicia
2015-06-01
We develop tools from computational algebraic geometry for the study of steady state features of autonomous polynomial dynamical systems via elimination of variables. In particular, we obtain nontrivial bounds for the steady state concentration of a given species in biochemical reaction networks with mass-action kinetics. This species is understood as the output of the network and we thus bound the maximal response of the system. The improved bounds give smaller starting boxes to launch numerical methods. We apply our results to the sequential enzymatic network studied in Markevich et al. (J Cell Biol 164(3):353-359, 2004) to find nontrivial upper bounds for the different substrate concentrations at steady state. Our approach does not require any simulation, analytical expression to describe the output in terms of the input, or the absence of multistationarity. Instead, we show how to extract information from effectively computable implicit dose-response curves, with the use of resultants and discriminants. We moreover illustrate in the application to an enzymatic network, the relation between the exact implicit dose-response curve we obtain symbolically and the standard hysteresis diagram provided by a numerical ode solver. The setting and tools we propose could yield many other results adapted to any autonomous polynomial dynamical system, beyond those where it is possible to get explicit expressions. PMID:25008963
The mechanism by which fish antifreeze proteins cause thermal hysteresis.
Kristiansen, Erlend; Zachariassen, Karl Erik
2005-12-01
the hysteresis freezing point. We then go on to summarise the empirical data to show that the dependence of the hysteresis on the concentration of antifreeze proteins arises from an equilibrium exchange of antifreeze proteins between ice and solution at the melting point. This reversible association between antifreeze proteins and the ice is followed by an irreversible adsorption of the antifreeze proteins onto a newly formed crystal plane when the temperature is lowered below the melting point. The formation of the crystal plane is due to a solidification of the interfacial region, and the necessary bond strength is provided by the protein "freezing" to the surface. In essence: the antifreeze proteins are "melted off" the ice at the bulk melting point and "freeze" to the ice as the temperature is reduced to subfreezing temperatures. We explain the different hysteresis activities caused by different types of antifreeze proteins at equimolar concentrations as a consequence of their solubility features during the phase of reversible association between the proteins and the ice, i.e., at the melting point; a low water solubility results in a large fraction of the proteins being associated with the ice at the melting point. This leads to a greater density of irreversibly adsorbed antifreeze proteins at the ice surface when the temperature drops, and thus to a greater hysteresis activity. Reference is also made to observations on insect antifreeze proteins to emphasise the general validity of this approach. PMID:16140290
Completely inverted hysteresis loops: Inhomogeneity effects or experimental artifacts
Song, C. Cui, B.; Pan, F.; Yu, H. Y.
2013-11-14
Completely inverted hysteresis loops (IHL) are obtained by the superconducting quantum interference device with large cooling fields (>10 kOe) in (La,Sr)MnO{sub 3} films with self-assembled LaSrMnO{sub 4}, an antiferromagnetic interface. Although the behaviours of measured loops show many features characteristic to the IHL, its origin, however, is not due to the exchange coupling between (La,Sr)MnO{sub 3}/LaSrMnO{sub 4}, an often accepted view on IHL. Instead, we demonstrate that the negative remanence arises from the hysteresis of superconducting coils, which drops abruptly when lower cooling fields are utilized. Hence the completely inverted hysteresis loops are experimental artifacts rather than previously proposed inhomogeneity effects in complicated materials.
Hysteresis-driven structure formation in biochemical networks
Klein
1998-09-21
A mechanism of structure formation, based on hysteresis behaviour is presented. A bisubstrate kinetic system with substrate inhibition, discussed previously in the context of Turing structure formation, may show hysteresis behaviour, when embedded in a metabolic network: the system may possess multiple steady states and may be switched from one stable fixpoint to the other. When cells containing this type of system are diffusively coupled, under certain conditions patterns result, which, as is demonstrated, are not of the Turing type. The main difference to diffusion-driven (Turing) structures is the fact that the hysteresis-driven patterns emerge under diffusive conditions, under which both the homogeneous and the asymmetrical steady state is stable. The resulting special properties and biological implications are discussed.Copyright 1998 Academic Press Limited PMID:9778438
Asymmetric-hysteresis compensation in piezoelectric actuators
NASA Astrophysics Data System (ADS)
Aguirre, Gorka; Janssens, Thierry; Van Brussel, Hendrik; Al-Bender, Farid
2012-07-01
The advantages of using piezoelectric actuators in ultra-precision applications are often impaired by nonlinear effects, in particular hysteresis, which may lead to positioning uncertainties of up to 15% of the actuator's stroke. Model-based compensation strategies are often prescribed in order to overcome this limitation and achieve better dynamical accuracy. This comes, however, at the expense of increasing identification and implementation complexity, especially when hysteresis is of the asymmetric type, such as prevalent in hard piezoceramic materials. This paper proposes a new compensation strategy based upon (i) treating hysteresis as being separate from other dynamical effects and (ii) formulating a new, simplified model to deal with asymmetric hysteresis, based on applying a linear operator to the conventional hysteresis models. After developing the theoretical background of the compensation strategy, the accuracy improvement due to the new hysteresis-compensation method is demonstrated experimentally.
NASA Astrophysics Data System (ADS)
Losby, Joseph; Diao, Zhu; Burgess, Jacob; Compton, Shawn; Fani Sani, Fatemeh; Firdous, Tayyaba; Vick, Douglas; Belov, Miro; Hiebert, Wayne; Freeman, Mark
2013-03-01
A micromagnetic disk was milled from a monocrystalline yttrium iron garnet film using a focused ion beam and micromanipulated onto a nanoscale torsional resonator. Nanomechanical torque magnetometry results show a unipolar magnetic hysteresis characteristic of a magnetic vortex state. Landau-Lifshitz-Gilbert-based micromagnetic simulations of the disk show a rich, flux-enclosed, three-dimensional domain structure. On the top and bottom faces of the disk, a skewed vortex state exists with a very small core. The core region extends through the thickness of the disk with a smooth variation in core diameter reaching a maximum along the midplane of the disk. The single crystalline nature of the disk lends to an observed absence of Barkhausen-like steps in the magnetization-versus-field curves, qualitatively different in comparison to the magnetometry results of an individual polycrystalline permalloy microdisk. Prospects for the mechanical detection of spin dynamical modes in these structures will also be discussed.
Pu Yunti; Zhu Jiliang; Zhu Xiaohong; Luo Yuansheng; Wang Mingsong; Li Xuhai; Liu Jing; Zhu Jianguo; Xiao Dingquan
2011-02-15
Pb(Zr{sub 0.8}Ti{sub 0.2})O{sub 3} (PZT80/20) thin films were deposited on the Pt(111)/Ti/SiO{sub 2}/Si(100) substrates by RF magnetron sputtering. Mainly perovskite crystalline phase with highly (202)-preferred orientation, determined by x-ray diffraction, was formed in the lead zirconate titanate (PZT)(80/20) thin films. Polarization measurements of the unannealed and aged films showed a clear double hysteresis loop. However, the double hysteresis loop phenomenon was greatly suppressed in the PZT thin films annealed under pure oxygen, and thus they exhibited larger remnant polarization (P{sub r} = 6.3 {mu}C/cm{sup 2}). The related mechanism for the appearance of constricted and double hysteresis loops was investigated to be associated with the realignment and disassociation of defect dipoles via oxygen octahedral rotations or oxygen vacancy diffusion. The butterfly-shaped C-V characteristic curve with a valley gave further evidence for double hysteresis loop characteristic in the unannealed and aged PZT thin films.
Hysteresis and the Dynamic Elasticity of Consolidated Granular Materials
NASA Astrophysics Data System (ADS)
Guyer, R. A.; Tencate, James; Johnson, Paul
1999-04-01
Quasistatic elasticity measurements on rocks show them to be strikingly nonlinear and to have elastic hysteresis with end point memory. When the model for this quasistatic elasticity is extended to the description of nonlinear dynamic elasticity the elastic elements responsible for the hysteresis dominate the behavior. Consequently, in a resonant bar, driven to nonlinearity, the frequency shift and the attenuation are predicted to be nonanalytic functions of the strain field. A resonant bar experiment yielding results in substantial qualitative and quantitative accord with these predictions is reported.
Khoshnevis, Sepideh; Craik, Natalie K; Matthew Brothers, R; Diller, Kenneth R
2016-03-01
The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC-skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy. PMID:26632263
NASA Astrophysics Data System (ADS)
Atitoaie, Alexandru; Stoleriu, Laurentiu; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian
2016-04-01
The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.
Improved charge amplifier using hybrid hysteresis compensation
NASA Astrophysics Data System (ADS)
Amin-Shahidi, Darya; Trumper, David L.
2013-08-01
We present a novel charge amplifier, with a robust feedback circuit and a method for compensating piezoelectric actuator's hysteresis at low frequencies. The amplifier uses a modified feedback circuit which improves robustness to the addition of series load impedance such as in cabling. We also describe a hybrid hysteresis compensation method for enabling the charge amplifier to reduce hysteresis at low frequencies. Experimental results demonstrate the utility of the new amplifier design.
Hysteresis and Frequency Tunability of Gyrotrons
NASA Astrophysics Data System (ADS)
Dumbrajs, O.; Khutoryan, E. M.; Idehara, T.
2016-06-01
We present the first devoted theoretical and experimental study of the hysteresis phenomenon in relation to frequency tunability of gyrotrons. In addition, we generalize the theory describing electron tuning of frequency in gyrotrons developed earlier to arbitrary harmonics. It is found that theoretical magnetic and voltage hysteresis loops are about two times larger than experimental loops. In gyrotrons whose cavities have high quality factors, hysteresis allows one only little to broaden the frequency tunability range.
Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system
Kocakaplan, Yusuf; Keskin, Mustafa
2014-09-07
The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.
Semiempirical model of soil water hysteresis
Nimmo, J.R.
1992-01-01
In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a given porous medium. Tests of the model show that it provides high-quality optimized fits to measured water content vs. matric pressure wetting curves for a wide variety of media. A practical use of this model is to provide a complete simulated main wetting curve for a medium where only a main drying curve and two points on the wetting curve have been measured. -from Author
MATHEMATICAL MODELS OF HYSTERESIS (DYNAMIC PROBLEMS IN HYSTERESIS)
Professor Isaak Mayergoyz
2006-08-21
This research has further advanced the current state of the art in the areas of dynamic aspects of hysteresis and nonlinear large scale magnetization dynamics. The results of this research will find important engineering applications in the areas of magnetic data storage technology and the emerging technology of “spintronics”. Our research efforts have been focused on the following tasks: • Study of fast (pulse) precessional switching of magnetization in magnetic materials. • Analysis of critical fields and critical angles for precessional switching of magnetization. • Development of inverse problem approach to the design of magnetic field pulses for precessional switching of magnetization. • Study of magnetization dynamics induced by spin polarized current injection. • Construction of complete stability diagrams for spin polarized current induced magnetization dynamics. • Development of the averaging technique for the analysis of the slow time scale magnetization dynamics. • Study of thermal effects on magnetization dynamics by using the theory of stochastic processes on graphs.
Electroosmotic Flow Hysteresis for Dissimilar Anionic Solutions.
Lim, An Eng; Lim, Chun Yee; Lam, Yee Cheong
2016-08-16
Electroosmotic flow (EOF) with two or more fluids is often encountered in various microfluidic applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during displacement flow of solutions with dissimilar anion species. In this investigation, EOF of dissimilar anionic solutions was studied experimentally through the current monitoring method and numerically through finite element simulations. As opposed to other conventional displacement flows, EOF involving dissimilar anionic solutions exhibits counterintuitive behavior, whereby the current-time curve does not reach the steady-state value of the displacing electrolyte. Two distinct mechanics have been identified as the causes for this observation: (a) ion concentration adjustment when the displacing anions migrate upstream against EOF due to competition between the gradients of electromigrative and convective fluxes and (b) ion concentration readjustment induced by the static diffusive interfacial region between the dissimilar fluids which can only be propagated throughout the entire microchannel with the presence of EOF. The resultant ion distributions lead to the flow rate to be directional-dependent, indicating that the flow conditions are asymmetric between these two different flow directions. The outcomes of this investigation contribute to the in-depth understanding of flow behavior in microfluidic systems involving inhomogeneous fluids, particularly dissimilar anionic solutions. The understanding of EOF hysteresis is fundamentally important for the accurate prediction of analytes transport in microfluidic devices under EOF. PMID:27426052
Hysteresis modeling and measurement for two-dimensional particle assemblies
NASA Astrophysics Data System (ADS)
Hauser, H.; Fulmek, P. L.; Grössinger, R.
2002-04-01
The increasing accuracy of circuit data storage simulations demands reliable models for the magnetic behaviour of the magnetic storage material. This paper introduces and compares the results of measurements and the results of model calculations by applying the Jiles-Atherton model, and the energetic model of ferromagnetic hysteresis by Hauser. The results show good agreement for uniaxial particle assemblies.
Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at nanoscale
Kalinin, Sergei V.; Jesse, Stephen; Yang, Yaodong; Li, Linglong; Liu, Zhengchun; Vasudevan, Rama K.
2016-04-27
Here, the nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with first order reversal curve (FORC) measurements on (K,Na)NbO3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the FORC ofmore » the polarization switching shows a clear decrease in correlation with increasing AC bias, suggesting the impact of domain wall clamping on the DC measurement case. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. These confirm the link between local piezoelectric nonlinearity, domain wall motion and minor loop formation, and suggest that existing theories (such as Preisach) are applicable at these length scales, with associated implications for future nanoscale devices.« less
NASA Astrophysics Data System (ADS)
Patros, T.
2011-12-01
Specific yield, or drainable porosity, is an important component in estimating groundwater recharge (GWR) using the water table fluctuation (WTF) method. The use of soil fillable porosity instead of specific yield has been proposed due to the effect of hysteresis on the soil moisture characteristic curve (SMCC), which shows that the specific yield may be larger than the fillable porosity, resulting in larger estimation of GWR. Here, an attempt is made to compare the specific yield and the fillable porosity mathematically, using an equation(s) for the SMCC (including hysteresis) from the literature. The implication of using either the specific yield or the fillable porosity on GWR estimation in homogeneous and layered heterogeneous profiles for a variety of soil textural classes is presented. In addition, replacing soil residual volumetric water content with soil field capacity, or specific retention, as a lower limit of the SMCC, and the influence of that change on GWR estimation, is critically examined for both the specific yield and the fillable porosity.
Hysteresis in the metachronal-tripod gait transition of insects: A modeling study
NASA Astrophysics Data System (ADS)
Fujiki, Soichiro; Aoi, Shinya; Funato, Tetsuro; Tomita, Nozomi; Senda, Kei; Tsuchiya, Kazuo
2013-07-01
Locomotion in biological systems involves various gaits, and hysteresis appears when the gaits change in accordance with the locomotion speed. That is, the gaits vary at different locomotion speeds depending on the direction of speed change. Although hysteresis is a typical characteristic of nonlinear dynamic systems, the underlying mechanism for the hysteresis in gait transitions remains largely unclear. In this study, we construct a neuromechanical model of an insect and investigate the dynamic characteristics of its gait and gait transition. The simulation results show that our insect model produces metachronal and tripod gaits depending on the locomotion speed through dynamic interactions among the body mechanical system, the nervous system, and the environment in a self-organized manner. They also show that it undergoes the metachronal-tripod gait transition with hysteresis by changing the locomotion speed. We examined the hysteresis mechanism in the metachronal-tripod gait transition of insects from a dynamic viewpoint.
Why Microtubules Run in Circles: Mechanical Hysteresis of the Tubulin Lattice
NASA Astrophysics Data System (ADS)
Ziebert, Falko; Mohrbach, Hervé; Kulić, Igor M.
2015-04-01
The fate of every eukaryotic cell subtly relies on the exceptional mechanical properties of microtubules. Despite significant efforts, understanding their unusual mechanics remains elusive. One persistent, unresolved mystery is the formation of long-lived arcs and rings, e.g., in kinesin-driven gliding assays. To elucidate their physical origin we develop a model of the inner workings of the microtubule's lattice, based on recent experimental evidence for a conformational switch of the tubulin dimer. We show that the microtubule lattice itself coexists in discrete polymorphic states. Metastable curved states can be induced via a mechanical hysteresis involving torques and forces typical of few molecular motors acting in unison, in agreement with the observations.
Hysteresis modeling of anisotropic and isotropic nanocrystalline hard magnetic films
NASA Astrophysics Data System (ADS)
Cornejo, D. R.; Azevedo, A.; Rezende, S. M.
2003-05-01
In the Hauser model, the magnetic state of a system is obtained by minimizing the so-called total energy function for a statistical set of magnetic domains. In this article, this energetic model of ferromagnetic materials is used in order to calculate hysteresis loops of isotropic and anisotropic nanocrystalline SmCo films at room temperature. A qualitative very good agreement between the calculated and experimental curves is obtained, mainly in the anisotropic case. Also, it has been verified that, under suitable approximations, the free parameters of the model can tie with intrinsic characteristics of the reversal magnetization process.
Hysteresis in the phase transition of chocolate
NASA Astrophysics Data System (ADS)
Ren, Ruilong; Lu, Qunfeng; Lin, Sihua; Dong, Xiaoyan; Fu, Hao; Wu, Shaoyi; Wu, Minghe; Teng, Baohua
2016-01-01
We designed an experiment to reproduce the hysteresis phenomenon of chocolate appearing in the heating and cooling process, and then established a model to relate the solidification degree to the order parameter. Based on the Landau-Devonshire theory, our model gave a description of the hysteresis phenomenon in chocolate, which lays the foundations for the study of the phase transition behavior of chocolate.
NASA Astrophysics Data System (ADS)
Barai, Anup; Widanage, W. Dhammika; Marco, James; McGordon, Andrew; Jennings, Paul
2015-11-01
Among lithium-ion battery applications, the relationship between state of charge (SoC) and open circuit voltage (OCV) is used for battery management system operation. The path dependence of OCV is a distinctive characteristic of lithium-ion batteries which is termed as OCV hysteresis. Accurate estimation of OCV hysteresis is essential for correct SoC identification. OCV hysteresis test procedures used previously do not consider the coupling of variables that show an apparent increase in hysteresis. To study true OCV hysteresis, this paper proposes a new test methodology. Using the proposed methodology, OCV hysteresis has been quantified for different lithium-ion cells. The test results show that a battery's OCV is directly related to the discharge capacity. Measured battery capacity can vary up to 5.0% depending on the test procedure and cell chemistry. The maximum hysteresis was found in a LiFePO4 (LFP) cell (38 mV) and lowest in the LTO cell (16 mV). A dynamic hysteresis model is used to show how better prediction accuracy can be achieved when hysteresis voltage is a function of SoC instead of assuming as a constant. The results highlight the importance of the testing procedure for OCV characterisation and that hysteresis is present in other Li-ion batteries in addition to LFP.
Riggs, H.C.
1968-01-01
This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.
Assessing temporal variations in connectivity through suspended sediment hysteresis analysis
NASA Astrophysics Data System (ADS)
Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; Melland, Alice; Mellander, Per-Erik; hUallacháin, Daire Ó.
2016-04-01
Connectivity provides a valuable concept for understanding catchment-scale sediment dynamics. In intensive agricultural catchments, land management through tillage, high livestock densities and extensive land drainage practices significantly change hydromorphological behaviour and alter sediment supply and downstream delivery. Analysis of suspended sediment-discharge hysteresis has offered insights into sediment dynamics but typically on a limited selection of events. Greater availability of continuous high-resolution discharge and turbidity data and qualitative hysteresis metrics enables assessment of sediment dynamics during more events and over time. This paper assesses the utility of this approach to explore seasonal variations in connectivity. Data were collected from three small (c. 10 km2) intensive agricultural catchments in Ireland with contrasting morphologies, soil types, land use patterns and management practices, and are broadly defined as low-permeability supporting grassland, moderate-permeability supporting arable and high-permeability supporting arable. Suspended sediment concentration (using calibrated turbidity measurements) and discharge data were collected at 10-min resolution from each catchment outlet and precipitation data were collected from a weather station within each catchment. Event databases (67-90 events per catchment) collated information on sediment export metrics, hysteresis category (e.g., clockwise, anti-clockwise, no hysteresis), numeric hysteresis index, and potential hydro-meteorological controls on sediment transport including precipitation amount, duration, intensity, stream flow and antecedent soil moisture and rainfall. Statistical analysis of potential controls on sediment export was undertaken using Pearson's correlation coefficient on separate hysteresis categories in each catchment. Sediment hysteresis fluctuations through time were subsequently assessed using the hysteresis index. Results showed the numeric
Three-Phase Capillary Pressure, Hysteresis and Trapping in a Porous Glass-Bead Column
NASA Astrophysics Data System (ADS)
Andersson, L.; Schlüter, S.; Li, T.; Brown, K. I.; Helland, J. O.; Wildenschild, D.
2015-12-01
Enhanced oil recovery (EOR) strategies employing water-alternate-gas (WAG) injections may improve oil mobility and production recovery. WAG injections for EOR create regions in the reservoir with simultaneous flow of oil, water and air dominated by capillary and gravity forces. As a result of the dynamics in the transition zones, the invading fluid may snap off compartments of the displaced fluid which could then be trapped in the pore space, contributing to the hysteresis of the three-phase capillary pressure curves. Three-phase capillary pressure curves are needed to model the three-phase transition zone movements in the reservoir. In reservoir simulation models, the common practice has been to implement three-phase capillary pressure curves based on two-phase gas-oil and oil-water capillary pressure data. However, experimental and modelling studies of three-phase fluid distributions at the pore scale have shown that this procedure is not always valid; three-phase capillary pressure curves exhibit hysteresis and depend on the saturation history of the three phases which cannot be derived from two-phase capillary pressure curves. We have developed three-phase experiments that provide capillary pressures and 3D-image data of fluid distributions in the entire saturation space of oil, water and air in water-wet porous glass-bead columns; a time-consuming and technically challenging exercise. The 3D data with a resolution of 6.38 μm were derived from high-resolution synchrotron x-ray computed micro-tomography (CMT), collected at the GSECARS beam line 13-BM-D at the Advanced Photon Source, Argonne National Laboratory. In particular, we discuss how three-phase pore-scale mechanisms, such as oil layer existence and multiple displacement events, affect the mobility and trapping of oil in the porous medium. We also show that wettability-alterations of the porous medium in contact with the three-phase fluid system and exposure to x-rays can be avoided by using iodine
New Phenomenon of the Hysteresis of 4He in Vycor Glass
NASA Astrophysics Data System (ADS)
Jin, Xin; Xu, Xiaonong; Yan, Yong; A, L. Thomson; D, F. Brewer; S, Haynes; N, Sharma
1992-02-01
The low temperature part of hysteresis curves of the freezing and melting processes of 4He in vycor glass with the lowest temperature 0.4K were measured, as the pressure ranged from 36.45 to 55.18 (105 Pa). Some novel characteristics of these curves were observed in such high temperature and pressure range. They may result from the existence of superfluid 4He.
Direct hysteresis measurements on ferroelectret films by means of a modified Sawyer-Tower circuit
NASA Astrophysics Data System (ADS)
Qiu, Xunlin; Holländer, Lars; Wirges, Werner; Gerhard, Reimund; Cury Basso, Heitor
2013-06-01
Ferro- and piezo-electrets are non-polar polymer foams or film systems with internally charged cavities. Since their invention more than two decades ago, ferroelectrets have become a welcome addition to the range of piezo-, pyro-, and ferro-electric materials available for device applications. A polarization-versus-electric-field hysteresis is an essential feature of a ferroelectric material and may also be used for determining some of its main properties. Here, a modified Sawyer-Tower circuit and a combination of unipolar and bipolar voltage waveforms are employed to record hysteresis curves on cellular-foam polypropylene ferroelectret films and on tubular-channel fluoroethylenepropylene copolymer ferroelectret film systems. Internal dielectric barrier discharges (DBDs) are required for depositing the internal charges in ferroelectrets. The true amount of charge transferred during the internal DBDs is obtained from voltage measurements on a standard capacitor connected in series with the sample, but with a much larger capacitance than the sample. Another standard capacitor with a much smaller capacitance—which is, however, still considerably larger than the sample capacitance—is also connected in series as a high-voltage divider protecting the electrometer against destructive breakdown. It is shown how the DBDs inside the polymer cavities lead to phenomenological hysteresis curves that cannot be distinguished from the hysteresis loops found on other ferroic materials. The physical mechanisms behind the hysteresis behavior are described and discussed.
Hysteresis during contact angles measurement.
Diaz, M Elena; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D
2010-03-15
A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle. PMID:20060981
Hysteresis of unsaturated hydromechanical properties of a silty soil
Lu, Ning; Kaya, Murat; Collins, Brian D.; Godt, Jonathan W.
2013-01-01
Laboratory tests to examine hysteresis in the hydrologic and mechanical properties of partially saturated soils were conducted on six intact specimens collected from a landslide-prone area of Alameda County, California. The results reveal that the pore-size distribution parameter remains statistically unchanged between the wetting and drying paths; however, the wetting or drying state has a pronounced influence on the water-entry pressure, the water-filled porosity at zero suction, and the saturated hydraulic conductivity. The suction stress values obtained from the shear-strength tests under both natural moisture and resaturated conditions were mostly bounded by the suction stress characteristic curves (SSCCs) obtained from the hydrologic tests. This finding experimentally confirms that the soil-water retention curve, hydraulic conductivity function, and SSCC are intrinsically related.
The capillary hysteresis model HYSTR: User`s guide
Niemi, A.; Bodvarsson, G.S.
1991-11-01
The potential disposal of nuclear waste in the unsaturated zone at Yucca Mountain, Nevada, has generated increased interest in the study of fluid flow through unsaturated media. In the near future, large-scale field tests will be conducted at the Yucca Mountain site, and work is now being done to design and analyze these tests. As part of these efforts a capillary hysteresis model has been developed. A computer program to calculate the hysteretic relationship between capillary pressure {phi} and liquid saturation (S{sub 1}) has been written that is designed to be easily incorporated into any numerical unsaturated flow simulator that computes capillary pressure as a function of liquid saturation. This report gives a detailed description of the model along with information on how it can be interfaced with a transport code. Although the model was developed specifically for calculations related to nuclear waste disposal, it should be applicable to any capillary hysteresis problem for which the secondary and higher order scanning curves can be approximated from the first order scanning curves. HYSTR is a set of subroutines to calculate capillary pressure for a given liquid saturation under hysteretic conditions.
Stress hysteresis as the cause of persistent holes in particulate suspensions
NASA Astrophysics Data System (ADS)
Deegan, Robert D.
2010-03-01
Concentrated particulate suspensions under vibrations can support stable, localized, vertically oriented free surfaces. The most robust of these structures are persistent holes: deep and stable depressions of the interface. Using a reduced model of the hydrodynamics we show that a rheology with hysteresis can lead to motion opposite to the time-averaged applied force. Moreover, we show experimentally that particulate suspensions of cornstarch in water exhibits hysteresis in the shear-rate response to an applied sinusoidal stress. The results of our model and our experiments suggest that hysteresis accounts for the outward force needed to support persistent holes.
Knoop, P.; Culick, F.E.C.; Zukoski, E.E.
1996-07-01
This report presents the first quantitative data establishing the details of hysteresis whose existence in dynamical behavior was reported by Sterling and Zukoski. The new idea was demonstrated that the presence of dynamical hysteresis provides opportunity for a novel strategy of active nonlinear control of unsteady motions in combustors. A figure shows the hysteresis exhibited for the amplitude of pressure oscillations as a function of equivalence ratio in a combustor having a recirculation zone, in this case a dump combustor.
Cardona, Samir Julián Calvo; Cadavid, Henry Cardona; Corrales, Juan David; Munilla, Sebastián; Cantet, Rodolfo J C; Rogberg-Muñoz, Andrés
2016-09-01
The κ-casein (CSN-3) and β-lactoglobulin (BLG) genes are extensively polymorphic in ruminants. Several association studies have estimated the effects of polymorphisms in these genes on milk yield, milk composition, and cheese-manufacturing properties. Usually, these results are based on production integrated over the lactation curve or on cross-sectional studies at specific days in milk (DIM). However, as differential expression of milk protein genes occurs over lactation, the effect of the polymorphisms may change over time. In this study, we fitted a mixed-effects regression model to test-day records of milk yield and milk quality traits (fat, protein, and total solids yields) from Colombian tropical dairy goats. We used the well-characterized A/B polymorphisms in the CSN-3 and BLG genes. We argued that this approach provided more efficient estimators than cross-sectional designs, given the same number and pattern of observations, and allowed exclusion of between-subject variation from model error. The BLG genotype AA showed a greater performance than the BB genotype for all traits along the whole lactation curve, whereas the heterozygote showed an intermediate performance. We observed no such constant pattern for the CSN-3 gene between the AA homozygote and the heterozygote (the BB genotype was absent from the sample). The differences among the genotypic effects of the BLG and the CSN-3 polymorphisms were statistically significant during peak and mid lactation (around 40-160 DIM) for the BLG gene and only for mid lactation (80-145 DIM) for the CSN-3 gene. We also estimated the additive and dominant effects of the BLG locus. The locus showed a statistically significant additive behavior along the whole lactation trajectory for all quality traits, whereas for milk yield the effect was not significant at later stages. In turn, we detected a statistically significant dominance effect only for fat yield in the early and peak stages of lactation (at about 1-45 DIM
Cihan, Abdullah; Birkholzer, Jens; Trevisan, Luca; Bianchi, Marco; Zhou, Quanlin; Illangasekare, Tissa
2014-12-31
During CO_{2} injection and storage in deep reservoirs, the injected CO_{2} enters into an initially brine saturated porous medium, and after the injection stops, natural groundwater flow eventually displaces the injected mobile-phase CO_{2}, leaving behind residual non-wetting fluid. Accurate modeling of two-phase flow processes are needed for predicting fate and transport of injected CO_{2}, evaluating environmental risks and designing more effective storage schemes. The entrapped non-wetting fluid saturation is typically a function of the spatially varying maximum saturation at the end of injection. At the pore-scale, distribution of void sizes and connectivity of void space play a major role for the macroscopic hysteresis behavior and capillary entrapment of wetting and non-wetting fluids. This paper presents development of an approach based on the connectivity of void space for modeling hysteretic capillary pressure-saturation-relative permeability relationships. The new approach uses void-size distribution and a measure of void space connectivity to compute the hysteretic constitutive functions and to predict entrapped fluid phase saturations. Two functions, the drainage connectivity function and the wetting connectivity function, are introduced to characterize connectivity of fluids in void space during drainage and wetting processes. These functions can be estimated through pore-scale simulations in computer-generated porous media or from traditional experimental measurements of primary drainage and main wetting curves. The hysteresis model for saturation-capillary pressure is tested successfully by comparing the model-predicted residual saturation and scanning curves with actual data sets obtained from column experiments found in the literature. A numerical two-phase model simulator with the new hysteresis functions is tested against laboratory experiments conducted in a quasi-two-dimensional flow cell (91.4cm×5.6cm×61cm
Cihan, Abdullah; Birkholzer, Jens; Trevisan, Luca; Bianchi, Marco; Zhou, Quanlin; Illangasekare, Tissa
2014-12-31
During CO2 injection and storage in deep reservoirs, the injected CO2 enters into an initially brine saturated porous medium, and after the injection stops, natural groundwater flow eventually displaces the injected mobile-phase CO2, leaving behind residual non-wetting fluid. Accurate modeling of two-phase flow processes are needed for predicting fate and transport of injected CO2, evaluating environmental risks and designing more effective storage schemes. The entrapped non-wetting fluid saturation is typically a function of the spatially varying maximum saturation at the end of injection. At the pore-scale, distribution of void sizes and connectivity of void space play a major role formore » the macroscopic hysteresis behavior and capillary entrapment of wetting and non-wetting fluids. This paper presents development of an approach based on the connectivity of void space for modeling hysteretic capillary pressure-saturation-relative permeability relationships. The new approach uses void-size distribution and a measure of void space connectivity to compute the hysteretic constitutive functions and to predict entrapped fluid phase saturations. Two functions, the drainage connectivity function and the wetting connectivity function, are introduced to characterize connectivity of fluids in void space during drainage and wetting processes. These functions can be estimated through pore-scale simulations in computer-generated porous media or from traditional experimental measurements of primary drainage and main wetting curves. The hysteresis model for saturation-capillary pressure is tested successfully by comparing the model-predicted residual saturation and scanning curves with actual data sets obtained from column experiments found in the literature. A numerical two-phase model simulator with the new hysteresis functions is tested against laboratory experiments conducted in a quasi-two-dimensional flow cell (91.4cm×5.6cm×61cm), packed with homogeneous and
Negative and positive hysteresis in double-cavity optical bistability in a three-level atom
Babu, H. Aswath; Wanare, Harshawardhan
2011-03-15
We present dual hysteretic behavior of a three-level ladder system exhibiting optical bistability in a double-cavity configuration in the mean-field limit. The two fields coupling the atomic system experience competing cooperative effects along the two transitions. We observe a hump-like feature in the bistable curve arising due to cavity-induced inversion, which transforms into a negative-hysteresis loop. Apart from negative- and positive-hysteresis regions, the system offers a variety of controllable nonlinear dynamical features, ranging from switching, periodic self-pulsing to chaos.
NASA Astrophysics Data System (ADS)
Andrei, Petru; Oniciuc, Liviu; Stancu, Alexandru; Stoleriu, Laurentiu
2007-09-01
An identification technique for the parameters of phenomenological models of hysteresis is presented. The basic idea of our technique is to set up a system of equations for the parameters of the model as a function of known quantities on the major or minor hysteresis loops (e.g. coercive force, susceptibilities at various points, remanence), or other magnetization curves. This system of equations can be either over or underspecified and is solved by using the conjugate gradient method. Numerical results related to the identification of parameters in the Energetic, Jiles-Atherton, and Preisach models are presented.
Equivalent Circuit Modeling of Hysteresis Motors
Nitao, J J; Scharlemann, E T; Kirkendall, B A
2009-08-31
We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.
Free boundaries in problems with hysteresis
Apushkinskaya, D. E.; Uraltseva, N. N.
2015-01-01
Here, we present a survey concerning parabolic free boundary problems involving a discontinuous hysteresis operator. Such problems describe biological and chemical processes ‘with memory’ in which various substances interact according to hysteresis law. Our main objective is to discuss the structure of the free boundaries and the properties of the so-called ‘strong solutions’ belonging to the anisotropic Sobolev class with sufficiently large q. Several open problems in this direction are proposed as well. PMID:26261368
Spatial versus time hysteresis in damping mechanisms
NASA Technical Reports Server (NTRS)
Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.
1988-01-01
A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.
Special hysteresis effects in N{sub 2}-sorption and mercury-porosimetry measurements
Giesche, H.
1996-12-31
Model pore structures were prepared from dispersions of submicron monodispersed silica particles by a sedimentation process. Ordered dense sphere packing structures were observed with scanning electron microscopy. Nitrogen sorption- as well as Hg-porosimetry measurements confirmed the calculated values of the pore openings in those structures. In Hg-porosimetry measurements a two step extrusion curve was observed, when the pore system was only partially filled during the intrusion process. This two step curve was not observed in case the pore system was filled with mercury to more than 95% during the intrusion run. The mercury porosimetry results can be interpreted in terms of the coexistence of octahedral and tetrahedral voids (pores) in the examined sphere packing structure and their special arrangement within the structure (connectivity). Two models will be described to explain the general occurrence of hysteresis in Hg-porosimetry. The actual pore geometry is shown to have a profound influence on the hysteresis shape as well as a change in the contact angle (constant within each measurement) can result in totally different hysteresis curves. Nitrogen adsorption and desorption measurements on the same powders did not reveal any fine structure within the hysteresis range.
Load-Dependent Friction Hysteresis on Graphene.
Ye, Zhijiang; Egberts, Philip; Han, Gang Hee; Johnson, A T Charlie; Carpick, Robert W; Martini, Ashlie
2016-05-24
Nanoscale friction often exhibits hysteresis when load is increased (loading) and then decreased (unloading) and is manifested as larger friction measured during unloading compared to loading for a given load. In this work, the origins of load-dependent friction hysteresis were explored through atomic force microscopy (AFM) experiments of a silicon tip sliding on chemical vapor deposited graphene in air, and molecular dynamics simulations of a model AFM tip on graphene, mimicking both vacuum and humid air environmental conditions. It was found that only simulations with water at the tip-graphene contact reproduced the experimentally observed hysteresis. The mechanisms underlying this friction hysteresis were then investigated in the simulations by varying the graphene-water interaction strength. The size of the water-graphene interface exhibited hysteresis trends consistent with the friction, while measures of other previously proposed mechanisms, such as out-of-plane deformation of the graphene film and irreversible reorganization of the water molecules at the shearing interface, were less correlated to the friction hysteresis. The relationship between the size of the sliding interface and friction observed in the simulations was explained in terms of the varying contact angles in front of and behind the sliding tip, which were larger during loading than unloading. PMID:27110836
Magnetic resonance imaging (MRI) study of jet height hysteresis in packed beds
NASA Astrophysics Data System (ADS)
Köhl, Maximilian H.; Lu, Guang; Third, James R.; Prüssmann, Klaas P.; Müller, Christoph R.
2013-06-01
The jet-spout transition in fluidized beds can show hysteretic behavior. In this study the jet-spout transition was studied as a function of orifice velocity for particles of different size and shape using Magnetic Resonance Imaging (MRI). The measurements showed that the particle shape primarily affect to the width of the hysteresis loop whereas particle size governs the position of the hysteresis loop with regards to the orifice velocity.
NASA Astrophysics Data System (ADS)
Nishida, Kentaro; Okada, Yukimasa; Takao, Yoshinori; Eriguchi, Koji; Ono, Kouichi
2016-06-01
We propose an electrical method, named capacitance–voltage (C–V) monitoring, for quantifying plasma-induced damage (PID) to interlayer dielectrics. By this method, we measure the C–V hysteresis loops to assign carrier trap sites created by PID, and simultaneously obtain the change in the dielectric constant and thickness. We optimized the bias-sweep configuration for measuring the hysteresis curves. It is found that the C–V curve shifted in the negative direction during the optimized voltage sweep from accumulation to inversion in a pseudo-metal–oxide–semiconductor (MOS) structure. This implies the appearance of net positively charged sites owing to PID, presumably near the surface of the SiOC film. We estimate the density of defects created near the surface by monitoring the obtained C–V hysteresis curve shift. Since the degradation of interlayer dielectrics affects the circuit performance, the proposed quantitative method should be used for plasma process designs.
Hysteresis in the creasing instability of hydrogels and elastomers
NASA Astrophysics Data System (ADS)
Chen, Dayong; Cai, Shengqiang; Jin, Lihua; Suo, Zhigang; Hayward, Ryan
2013-03-01
Soft polymers placed under compressive stress can undergo an elastic creasing instability in which sharp folds spontaneously form on the free surfaces. This process can play an important role in a variety of material failure modes, but has also been harnessed to fabricate dynamic chemical and topographic patterns. Creases have been found to form by nucleation and growth, which we show reflects the influence of surface energy as a barrier for both processes. Hysteresis in the loading and unloading cycles is an important aspect of this process, but has been reported to occur to different degrees in different material systems. Through variations in interfacial energy, we show that for a model elastomeric system, it is self-adhesion within the folding region rather than plastic deformation that gives rise to hysteresis.
Bazghaleh, Mohsen Grainger, Steven; Cazzolato, Ben; Lu, Tien-Fu; Oskouei, Reza
2014-04-15
Smart actuators are the key components in a variety of nanopositioning applications, such as scanning probe microscopes and atomic force microscopes. Piezoelectric actuators are the most common smart actuators due to their high resolution, low power consumption, and wide operating frequency but they suffer hysteresis which affects linearity. In this paper, an innovative digital charge amplifier is presented to reduce hysteresis in piezoelectric stack actuators. Compared to traditional analog charge drives, experimental results show that the piezoelectric stack actuator driven by the digital charge amplifier has less hysteresis. It is also shown that the voltage drop of the digital charge amplifier is significantly less than the voltage drop of conventional analog charge amplifiers.
Sufficient conditions for rate-independent hysteresis in autoregressive identified models
NASA Astrophysics Data System (ADS)
Martins, Samir Angelo Milani; Aguirre, Luis Antonio
2016-06-01
This paper shows how hysteresis can be described using polynomial models and what are the sufficient conditions to be met by the model in order to have hysteresis. Such conditions are related to the model equilibria, to the forcing function and to certain term clusters in the polynomial models. The main results of the paper are used in the identification and analysis of nonlinear models estimated from data produced by a magneto-rheological damper (MRD) model with Bouc-Wen rate-independent hysteresis. A striking feature of the identified model is its simplicity and this could turn out to be a key factor in controller design.
Oscillating hysteresis in the q -neighbor Ising model
NASA Astrophysics Data System (ADS)
JÈ©drzejewski, Arkadiusz; Chmiel, Anna; Sznajd-Weron, Katarzyna
2015-11-01
We modify the kinetic Ising model with Metropolis dynamics, allowing each spin to interact only with q spins randomly chosen from the whole system, which corresponds to the topology of a complete graph. We show that the model with q ≥3 exhibits a phase transition between ferromagnetic and paramagnetic phases at temperature T*, which linearly increases with q . Moreover, we show that for q =3 the phase transition is continuous and that it is discontinuous for larger values of q . For q >3 , the hysteresis exhibits oscillatory behavior—expanding for even values of q and shrinking for odd values of q . Due to the mean-field-like nature of the model, we are able to derive the analytical form of transition probabilities and, therefore, calculate not only the probability density function of the order parameter but also precisely determine the hysteresis and the effective potential showing stable, unstable, and metastable steady states. Our results show that a seemingly small modification of the kinetic Ising model leads not only to the switch from a continuous to a discontinuous phase transition, but also to an unexpected oscillating behavior of the hysteresis and a puzzling phenomenon for q =5 , which might be taken as evidence for the so-called mixed-order phase transition.
Oscillating hysteresis in the q-neighbor Ising model.
Jȩdrzejewski, Arkadiusz; Chmiel, Anna; Sznajd-Weron, Katarzyna
2015-11-01
We modify the kinetic Ising model with Metropolis dynamics, allowing each spin to interact only with q spins randomly chosen from the whole system, which corresponds to the topology of a complete graph. We show that the model with q≥3 exhibits a phase transition between ferromagnetic and paramagnetic phases at temperature T*, which linearly increases with q. Moreover, we show that for q=3 the phase transition is continuous and that it is discontinuous for larger values of q. For q>3, the hysteresis exhibits oscillatory behavior-expanding for even values of q and shrinking for odd values of q. Due to the mean-field-like nature of the model, we are able to derive the analytical form of transition probabilities and, therefore, calculate not only the probability density function of the order parameter but also precisely determine the hysteresis and the effective potential showing stable, unstable, and metastable steady states. Our results show that a seemingly small modification of the kinetic Ising model leads not only to the switch from a continuous to a discontinuous phase transition, but also to an unexpected oscillating behavior of the hysteresis and a puzzling phenomenon for q=5, which might be taken as evidence for the so-called mixed-order phase transition. PMID:26651645
Scaling law for dynamical hysteresis of cavity solitons
NASA Astrophysics Data System (ADS)
Ahmadipanah, Sahar; Kheradmand, Reza; Prati, Franco
2016-02-01
By applying to a cavity soliton a control beam modulated in time, we study numerically the performance of the soliton as a flip-flop memory. The soliton is switched on and off periodically through a hysteresis cycle whose size increases dynamically with the modulation frequency. We show that the phenomenon is ruled by a scaling law with an exponent compatible with the theoretical value 2/3 predicted in much simpler systems in the low-frequency limit.
Hysteresis effects of changing the parameters of noncooperative games
NASA Astrophysics Data System (ADS)
Wolpert, David H.; Harré, Michael; Olbrich, Eckehard; Bertschinger, Nils; Jost, Jürgen
2012-03-01
We adapt the method used by Jaynes to derive the equilibria of statistical physics to instead derive equilibria of bounded rational game theory. We analyze the dependence of these equilibria on the parameters of the underlying game, focusing on hysteresis effects. In particular, we show that by gradually imposing individual-specific tax rates on the players of the game, and then gradually removing those taxes, the players move from a poor equilibrium to one that is better for all of them.
Matthews, G.P.; Ridgway, C.J.; Spearing, M.C.
1995-04-01
A void space network is presented for the simulation of mercury intrusion hysteresis in outcrop and reservoir sandstones and paper coatings. Three methods are described which allow the convergence of the simulation onto experiment, each finding the optimum pore and throat size distributions and connectivity according to different criteria. The simulated pore and throat size distributions are entirely different from the first derivatives of the intrusion curves which are commonly employed. The optimum void space networks, which have the correct porosity, are then used to simulate the hysteresis which occurs when the mercury is withdrawn. The effects of contact angle hysteresis and trapping within wide pores adjacent to narrow throats are demonstrated. Considerable trapping of mercury is found to occur because of snap-off effects, without invoking any dead-end pores. Similar networks have been used to simulate absolute gas permeability, tortuosity, diffusion, formation factor, and colloidal flow formation damage and can be applied to any porous medium.
Hybrid models of hysteresis for mixed hysteretic loops in heterogeneous magnetic materials
NASA Astrophysics Data System (ADS)
Dimian, M.; Andrei, P.; Grayson, M.
2014-05-01
The mixed hysteresis behavior of counter-clockwise and clockwise loops has recently attracted the attention of the magnetics community, due to several experimental findings in inhomogeneous and hetero-structure magnetic systems. Various hybrid models are proposed here to address this behavior based on the superposition of standard hysteresis models and their newly developed clockwise variants. A special attention is also devoted to Bouc-Wen model, a typical clockwise often used by applied mechanics community, and to its relevance for mixed hysteresis. These clockwise and hybrid models have been implemented in an open-access academic software and their performance is illustrated by examples of hysteretic loops, first order reversal curves and diagrams simulated in this framework.
Loading-unloading hysteresis loop of randomly rough adhesive contacts
NASA Astrophysics Data System (ADS)
Carbone, Giuseppe; Pierro, Elena; Recchia, Giuseppina
2015-12-01
We investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave vectors. A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged, and the calculated contact area and applied load are shown as a function of the penetration, for loading and unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process.
Loading-unloading hysteresis loop of randomly rough adhesive contacts.
Carbone, Giuseppe; Pierro, Elena; Recchia, Giuseppina
2015-12-01
We investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave vectors. A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged, and the calculated contact area and applied load are shown as a function of the penetration, for loading and unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process. PMID:26764700
Hysteresis in the Central African Rainforest
NASA Astrophysics Data System (ADS)
Pietsch, Stephan Alexander; Elias Bednar, Johannes; Gautam, Sishir; Petritsch, Richard; Schier, Franziska; Stanzl, Patrick
2014-05-01
Past climate change caused severe disturbances of the Central African rainforest belt, with forest fragmentation and re-expansion due to drier and wetter climate conditions. Besides climate, human induced forest degradation affected biodiversity, structure and carbon storage of Congo basin rainforests. Information on climatically stable, mature rainforest, unaffected by human induced disturbances, provides means of assessing the impact of forest degradation and may serve as benchmarks of carbon carrying capacity over regions with similar site and climate conditions. BioGeoChemical (BGC) ecosystem models explicitly consider the impacts of site and climate conditions and may assess benchmark levels over regions devoid of undisturbed conditions. We will present a BGC-model validation for the Western Congolian Lowland Rainforest (WCLRF) using field data from a recently confirmed forest refuge, show model - data comparisons for disturbed und undisturbed forests under different site and climate conditions as well as for sites with repeated assessment of biodiversity and standing biomass during recovery from intensive exploitation. We will present climatic thresholds for WCLRF stability, analyse the relationship between resilience, standing C-stocks and change in climate and finally provide evidence of hysteresis.
Titration and hysteresis in epigenetic chromatin silencing
NASA Astrophysics Data System (ADS)
Dayarian, Adel; Sengupta, Anirvan M.
2013-06-01
Epigenetic mechanisms of silencing via heritable chromatin modifications play a major role in gene regulation and cell fate specification. We consider a model of epigenetic chromatin silencing in budding yeast and study the bifurcation diagram and characterize the bistable and the monostable regimes. The main focus of this paper is to examine how the perturbations altering the activity of histone modifying enzymes affect the epigenetic states. We analyze the implications of having the total number of silencing proteins, given by the sum of proteins bound to the nucleosomes and the ones available in the ambient, to be constant. This constraint couples different regions of chromatin through the shared reservoir of ambient silencing proteins. We show that the response of the system to perturbations depends dramatically on the titration effect caused by the above constraint. In particular, for a certain range of overall abundance of silencing proteins, the hysteresis loop changes qualitatively with certain jump replaced by continuous merger of different states. In addition, we find a nonmonotonic dependence of gene expression on the rate of histone deacetylation activity of Sir2. We discuss how these qualitative predictions of our model could be compared with experimental studies of the yeast system under anti-silencing drugs.
NASA Astrophysics Data System (ADS)
Dos Santos, E.; Gattacceca, J.; Rochette, P.; Scorzelli, R. B.; Fillion, G.
2015-05-01
Since the solid matter in our solar system began to assemble 4.57 billion years ago, meteorites have recorded a large range of processes, including metamorphism, melting, irradiation and hypervelocity impacts. These processes as well as solar system magnetic fields can be accessed through the investigation of magnetic properties of meteorites. In this work, we present magnetic hysteresis properties, isothermal remanent magnetization acquisition curves and 57Fe Mössbauer spectra for nineteen iron and eleven stony-iron meteorites. These data will be the background for a discussion about the thermal and shock history of these meteorites. Although Mössbauer spectroscopy and hysteresis measurements are not able to provide cooling rates like the conventional metallographic method does, we show that the combination of the ordering degree of taenite phase measured by Mössbauer spectroscopy and hysteresis properties are useful for constraining the thermal and shock history of meteorites. In particular, strong shock and the associated thermal event that result in disordering of tetrataenite can be easily identified.
Hysteresis model and statistical interpretation of energy losses in non-oriented steels
NASA Astrophysics Data System (ADS)
Mănescu (Păltânea), Veronica; Păltânea, Gheorghe; Gavrilă, Horia
2016-04-01
In this paper the hysteresis energy losses in two non-oriented industrial steels (M400-65A and M800-65A) were determined, by means of an efficient classical Preisach model, which is based on the Pescetti-Biorci method for the identification of the Preisach density. The excess and the total energy losses were also determined, using a statistical framework, based on magnetic object theory. The hysteresis energy losses, in a non-oriented steel alloy, depend on the peak magnetic polarization and they can be computed using a Preisach model, due to the fact that in these materials there is a direct link between the elementary rectangular loops and the discontinuous character of the magnetization process (Barkhausen jumps). To determine the Preisach density it was necessary to measure the normal magnetization curve and the saturation hysteresis cycle. A system of equations was deduced and the Preisach density was calculated for a magnetic polarization of 1.5 T; then the hysteresis cycle was reconstructed. Using the same pattern for the Preisach distribution, it was computed the hysteresis cycle for 1 T. The classical losses were calculated using a well known formula and the excess energy losses were determined by means of the magnetic object theory. The total energy losses were mathematically reconstructed and compared with those, measured experimentally.
Material Data Representation of Hysteresis Loops for Hastelloy X Using Artificial Neural Networks
NASA Technical Reports Server (NTRS)
Alam, Javed; Berke, Laszlo; Murthy, Pappu L. N.
1993-01-01
The artificial neural network (ANN) model proposed by Rumelhart, Hinton, and Williams is applied to develop a functional approximation of material data in the form of hysteresis loops from a nickel-base superalloy, Hastelloy X. Several different ANN configurations are used to model hysteresis loops at different cycles for this alloy. The ANN models were successful in reproducing the hysteresis loops used for its training. However, because of sharp bends at the two ends of hysteresis loops, a drift occurs at the corners of the loops where loading changes to unloading and vice versa (the sharp bends occurred when the stress-strain curves were reproduced by adding stress increments to the preceding values of the stresses). Therefore, it is possible only to reproduce half of the loading path. The generalization capability of the network was tested by using additional data for two other hysteresis loops at different cycles. The results were in good agreement. Also, the use of ANN led to a data compression ratio of approximately 22:1.
A combined Preisach-Hyperbolic Tangent model for magnetic hysteresis of Terfenol-D
NASA Astrophysics Data System (ADS)
Talebian, Soheil; Hojjat, Yousef; Ghodsi, Mojtaba; Karafi, Mohammad Reza; Mirzamohammadi, Shahed
2015-12-01
This study presents a new model using the combination of Preisach and Hyperbolic Tangent models, to predict the magnetic hysteresis of Terfenol-D at different frequencies. Initially, a proper experimental setup was fabricated and used to obtain different magnetic hysteresis curves of Terfenol-D; such as major, minor and reversal loops. Then, it was shown that the Hyperbolic Tangent model is precisely capable of modeling the magnetic hysteresis of the Terfenol-D for both rate-independent and rate-dependent cases. Empirical equations were proposed with respect to magnetic field frequency which can calculate the non-dimensional coefficients needed by the model. These empirical equations were validated at new frequencies of 100 Hz and 300 Hz. Finally, the new model was developed through the combination of Preisach and Hyperbolic Tangent models. In the combined model, analytical relations of the Hyperbolic Tangent model for the first order reversal loops determined the weighting function of the Preisach model. This model reduces the required experiments and errors due to numerical differentiations generally needed for characterization of the Preisach function. In addition, it can predict the rate-dependent hysteresis as well as rate-independent hysteresis.
Mechanisms of magnetic and temperature hysteresis in ErFeO3 and TmFeO3 single crystals
NASA Astrophysics Data System (ADS)
Tsymbal, L. T.; Bazaliy, Ya. B.; Kakazei, G. N.; Vasiliev, S. V.
2010-10-01
Magnetic hysteresis is studied in the orthoferrites ErFeO3 and TmFeO3 using the single crystal samples of millimeter dimensions. It is shown that in both materials one observes a temperature transition manifesting itself through the temperature hysteresis of the magnetic moment and a peculiar temperature evolution of the field hysteresis loop shapes near this transition. Experiments rule out the hypothesis that the ordering of the orthoferrite's rare-earth magnetic moments plays an important role in these phenomena. The hysteresis curves can be explained by a few-domain magnetic state of the samples that results from the weak ferromagnetism of the orthoferrites. The phenomenon is generic for weak ferromagnets with temperature dependent magnetization. A large characteristic magnetic length makes the behavior of the relatively big samples analogous to that observed in the nanosize samples of strong ferromagnets.
Deformation Hysteresis of Electrohydrodynamic Patterning on a Thin Polymer Film.
Yang, Qingzhen; Li, Ben Q; Tian, Hongmiao; Li, Xiangming; Shao, Jinyou; Chen, Xiaoliang; Xu, Feng
2016-07-13
Electrohydrodynamic patterning is a technique that enables micro/nanostructures via imposing an external voltage on thin polymer films. In this investigation, we studied the electrohydrodynamic patterning theoretically and experimentally, with special interest focused on the equilibrium state. It is found that the equilibrium structure height increases with the voltage. In addition, we have observed, and believe it to be the first time, a hysteresis phenomenon exists in the relationship between the voltage and structure height. With an increase in the voltage, a critical value (the first critical voltage) is noticed, above which the polymer film would increase dramatically until it comes into contact with the template. However, with a decrease in the voltage, a smaller voltage (the second critical voltage) is needed to detach the polymer from the template. The mismatch of the first and second critical voltages distorts the voltage-structure height curve into an "S" shape. Such a phenomenon is verified for three representative templates and also by experiments. Furthermore, the effects of some parameters (e.g., polymer film thickness and dielectric constant) on this hysteresis phenomenon are also discussed. PMID:27326791
Preliminary capillary hysteresis simulations in fractured rocks, Yucca Mountain, Nevada
NASA Astrophysics Data System (ADS)
Niemi, A.; Bodvarsson, G. S.
1988-12-01
Preliminary simulations have been carried out to address the question of how hysteretic (history-dependent) capillary pressure-liquid saturation relation may affect the flow and liquid saturation distribution in a fractured rock system. Using a hysteresis model modified from the theoretically based dependent domain model of Mualem (1984), a system consisting of discrete fractures and rock matrix parts was simulated under periodically occurring infiltration pulses. Comparisons were made between the hysteretic case and the non-hysteretic case using the main drying curve alone. Material properties used represent values reported for the densely welded tuffs at Yucca Mountain, Nevada. Since no actual hysteresis measurements were available for the welded tuffs, the necessary data was derived based on information available in the soils literature The strongly hysteretic behavior in the uppermost layer of the matrix along with the overall lower matrix capillary suctions, generated higher fracture flows and a more "smeared" matrix liquid saturation vs. depth distribution for the hysteretic case. While the actual amounts of water being absorbed into the matrix were very similar, the distributions of this absorbed water were different and the matrix was affected up to greater depths in the hysteretic case in comparison to the non-hysteretic case.
Modeling of the interleaved hysteresis loop in the measurements of rotational core losses
NASA Astrophysics Data System (ADS)
Alatawneh, Natheer; Pillay, Pragasen
2016-01-01
The measurement of core losses in machine laminations reveals a fundamental difference between rotational and pulsating types. Rotational core losses under rotating fields decrease at high flux density, while pulsating losses keep increasing steadily. Experimental analyses of loss components Px and Py in x and y directions with rotating fields show that the loss decreases in one loss component and sometimes attains negative values. Tracking the evolution of hysteresis loops along this loss component discloses a peculiar behavior of magnetic hysteresis, where the loop changes its path from counterclockwise to clockwise within a cycle of magnetization process, the so called interleaved hysteresis loop. This paper highlights a successful procedure for modeling the interleaved hysteresis loop in the measurement of rotational core losses in electrical machine laminations using the generalized Prandtl-Ishlinskii (PI) model. The efficiency of the proposed model is compared to Preisach model. Results and conclusion of this work are of importance toward building an accurate model of rotational core losses.
Geometric hysteresis of alveolated ductal architecture.
Kojic, M; Butler, J P; Vlastelica, I; Stojanovic, B; Rankovic, V; Tsuda, A
2011-11-01
Low Reynolds number airflow in the pulmonary acinus and aerosol particle kinetics therein are significantly conditioned by the nature of the tidal motion of alveolar duct geometry. At least two components of the ductal structure are known to exhibit stress-strain hysteresis: smooth muscle within the alveolar entrance rings, and surfactant at the air-tissue interface. We hypothesize that the geometric hysteresis of the alveolar duct is largely determined by the interaction of the amount of smooth muscle and connective tissue in ductal rings, septal tissue properties, and surface tension-surface area characteristics of surfactant. To test this hypothesis, we have extended the well-known structural model of the alveolar duct by Wilson and Bachofen (1982, "A Model for Mechanical Structure of the Alveolar Duct," J. Appl. Physiol. 52(4), pp. 1064-1070) by adding realistic elastic and hysteretic properties of (1) the alveolar entrance ring, (2) septal tissue, and (3) surfactant. With realistic values for tissue and surface properties, we conclude that: (1) there is a significant, and underappreciated, amount of geometric hysteresis in alveolar ductal architecture; and (2) the contribution of smooth muscle and surfactant to geometric hysteresis are of opposite senses, tending toward cancellation. Quantitatively, the geometric hysteresis found experimentally by Miki et al. (1993, "Geometric Hysteresis in Pulmonary Surface-to-Volume Ratio during Tidal Breathing," J. Appl. Physiol. 75(4), pp. 1630-1636) is consistent with little or no smooth muscle tone in anesthetized rabbits in control conditions, and with substantial smooth muscle activation following methacholine challenge. The observed local hysteretic boundary motion of the acinar duct would result in irreversible acinar flow fields, which might be important mechanistic contributors to aerosol mixing and deposition deep in the lung. PMID:22168737
Hysteresis and Wavenumber Vacillation in Unstable Baroclinic Flows
NASA Technical Reports Server (NTRS)
Chou, Shih-Hung; Goodman, H. Michael (Technical Monitor)
2001-01-01
Hysteresis and wavenumber vacillation are studied numerically in a weakly stratified quasigeostrophic model. In general, the amplitude of the most unstable wave increases, as the flow becomes more unstable. When the wave becomes saturated, the next longer wave will grow at the expanse of the most unstable wave and becomes the dominant wave. However, once the longwave state is established, it may remain in that regime even as the instability is decreased beyond the threshold where it first developed, thus constituting a hysteresis loop. In a highly unstable case, the flow may not show a preference for any single wave. Instead, the dominant wave aperiodically varies among several long waves. This phenomenon is known as wavenumber vacillation. Hysteresis is further examined in terms of eddy heat flux. It is shown that total eddy heat flux increases as the flow becomes more unstable, but displays a sharp drop when transition to a longer wave occurs. However, in a longwave state, the heat flux always decreases with decreasing instability even pass the threshold when wave transition first occurs.
Hysteresis modeling in graphene field effect transistors
Winters, M.; Rorsman, N.; Sveinbjörnsson, E. Ö.
2015-02-21
Graphene field effect transistors with an Al{sub 2}O{sub 3} gate dielectric are fabricated on H-intercalated bilayer graphene grown on semi-insulating 4H-SiC by chemical vapour deposition. DC measurements of the gate voltage v{sub g} versus the drain current i{sub d} reveal a severe hysteresis of clockwise orientation. A capacitive model is used to derive the relationship between the applied gate voltage and the Fermi energy. The electron transport equations are then used to calculate the drain current for a given applied gate voltage. The hysteresis in measured data is then modeled via a modified Preisach kernel.
Hysteresis from Multiscale Porosity: Modeling Water Sorption and Shrinkage in Cement Paste
NASA Astrophysics Data System (ADS)
Pinson, Matthew B.; Masoero, Enrico; Bonnaud, Patrick A.; Manzano, Hegoi; Ji, Qing; Yip, Sidney; Thomas, Jeffrey J.; Bazant, Martin Z.; Van Vliet, Krystyn J.; Jennings, Hamlin M.
2015-06-01
Cement paste has a complex distribution of pores and molecular-scale spaces. This distribution controls the hysteresis of water sorption isotherms and associated bulk dimensional changes (shrinkage). We focus on two locations of evaporable water within the fine structure of pastes, each having unique properties, and we present applied physics models that capture the hysteresis by dividing drying and rewetting into two related regimes based on relative humidity (RH). We show that a continuum model, incorporating a pore-blocking mechanism for desorption and equilibrium thermodynamics for adsorption, explains well the sorption hysteresis for a paste that remains above approximately 20% RH. In addition, we show with molecular models and experiments that water in spaces of ≲1 nm width evaporates below approximately 20% RH but reenters throughout the entire RH range. This water is responsible for a drying shrinkage hysteresis similar to that of clays but opposite in direction to typical mesoporous glass. Combining the models of these two regimes allows the entire drying and rewetting hysteresis to be reproduced accurately and provides parameters to predict the corresponding dimensional changes. The resulting model can improve the engineering predictions of long-term drying shrinkage accounting also for the history dependence of strain induced by hysteresis. Alternative strategies for quantitative analyses of the microstructure of cement paste based on this mesoscale physical model of water content within porous spaces are discussed.
Adsorption Hysteresis and its Effect on CO2 Sequestration and Enhanced Coalbed Methane Recovery
NASA Astrophysics Data System (ADS)
Seto, C. J.; Tang, G. T.; Jessen, K.; Kovscek, A. R.; Orr, F. M.
2006-12-01
CO2 sequestration in coal reservoirs is a promising technology for reducing atmospheric CO2 concentrations. Of the candidates for geological sequestration, the physics of transport and sequestration in coal is the least well understood. Adsorption hysteresis has been observed for pure gas adsorption on some coals. It is manifest as desorption curves where the loading of gas on coal surfaces is greater than sorption at the same pressure. Current simulation technology does not have the functionality to incorporate this phenomenon that has a potentially great effect on sequestration in coalbeds. Understanding the interplay between adsorption and desorption of gas species, phase behaviour and convection is paramount to designing safe and effective sequestration projects. Our work integrates experiments and theory development. Isotherms of CH4, N2 and CO2 were measured on a sample of coal from the Powder River Basin, WY, for adsorption and desorption paths. Hysteresis was observed for all gases. Likewise, the displacment of methane by various mixtures of N2 and CO2 was also measured. Simultaneously, a model was developed to solve for the dispersion-free limit of convective transport in multiphase systems with adsorption, including the effects of volume change as components transfer from vapour to liquid and solid phases. Analytical solutions were obtained using the method of characteristics. These solutions were compared against corresponding solutions without adsorption hysteresis. For pure gas injection, in which the amount of adsorbed injected gas increases monotonically and the amount of adsorbed initial gas decreases monotonically, hysteresis effects were not observed. For injection gas mixtures of N2-CO2 displacing CH4, CO2 and N2 separated chromatographically and hysteresis effected breakthrough and bank arrival times as well as shifted overall component concentrations as the displacement progressed. When injection gas mixtures were rich in N2, the structures
NASA Astrophysics Data System (ADS)
Gangishetty, Mahesh K.; Scott, Robert W. J.; Kelly, Timothy L.
2016-03-01
Due to the hygroscopic nature of organolead halide perovskites, humidity is one of the most important factors affecting the efficiency and longevity of perovskite solar cells. Although humidity has a long term detrimental effect on device performance, it also plays a key role during the initial growth of perovskite crystals. Here we demonstrate that atmospheric relative humidity (RH) plays a key role during the formation of perovskite thin films via the sequential deposition technique. Our results indicate that the RH has a substantial impact on the crystallization process, and hence on device performance. SEM and pXRD analysis show an increase in crystallite size with increasing humidity. At low RH, the formation of small cubic crystallites with large gaps between them is observed. The presence of these voids adversely affects device performance and leads to substantial hysteresis in the device. At higher RH, the perovskite crystals are larger in size, with better connectivity between the crystallites. This produced efficient planar heterojunction solar cells with low hysteresis. By careful control of the RH during the cell fabrication process, efficiencies of up to 12.2% are reached using P3HT as the hole-transport material.Due to the hygroscopic nature of organolead halide perovskites, humidity is one of the most important factors affecting the efficiency and longevity of perovskite solar cells. Although humidity has a long term detrimental effect on device performance, it also plays a key role during the initial growth of perovskite crystals. Here we demonstrate that atmospheric relative humidity (RH) plays a key role during the formation of perovskite thin films via the sequential deposition technique. Our results indicate that the RH has a substantial impact on the crystallization process, and hence on device performance. SEM and pXRD analysis show an increase in crystallite size with increasing humidity. At low RH, the formation of small cubic crystallites
Influence of hydraulic hysteresis on the mechanical behavior of unsaturated soils and interfaces
NASA Astrophysics Data System (ADS)
Khoury, Charbel N.
Unsaturated soils are commonly widespread around the world, especially at shallow depths from the surface. The mechanical behavior of this near surface soil is influenced by the seasonal variations such as rainfall or drought, which in turn may have a detrimental effect on many structures (e.g. retaining walls, shallow foundations, mechanically stabilized earth walls, soil slopes, and pavements) in contact with it. Thus, in order to better understand this behavior, it is crucial to study the complex relationship between soil moisture content and matric suction (a stress state variable defined as pore air pressure minus pore water pressure) known as the Soil Water Characteristic Curve (SWCC). In addition, the influence of hydraulic hysteresis on the behavior of unsaturated soils, soil-structure interaction (i.e. rough and smooth steel interfaces, soil-geotextile interfaces) and pavement subgrade (depicted herein mainly by resilient modulus, Mr) was also studied. To this end, suction-controlled direct shear tests were performed on soils, rough and smooth steel interfaces and geotextile interface under drying (D) and wetting after drying (DW). The shearing behavior is examined in terms of the two stress state variables, matric suction and net normal stress. Results along the D and DW paths indicated that peak shear strength increased with suction and net normal stress; while in general, the post peak shear strength was not influenced by suction for rough interfaces and no consistent trend was observed for soils and soil-geotextiles interfaces. Contrary to saturated soils, results during shearing at higher suction values (i.e. 25 kPa and above) showed a decrease in water content eventhough the sample exhibited dilation. A behavior postulated to be related to disruption of menisci and/or non-uniformity of pore size which results in an increase in localized pore water pressures. Interestingly, wetting after drying (DW) test results showed higher peak and post peak shear
Managing Hysteresis: Three Cornerstones to Fiscal Stability
ERIC Educational Resources Information Center
Weeks, Richard
2012-01-01
The effects of the Great Recession of 2007-2009 continue to challenge school business officials (SBOs) and other education leaders as they strive to prepare students for the global workforce. Economists have borrowed a word from chemistry to describe this state of affairs: hysteresis--the lingering effects of the past on the present. Today's SBOs…
Design of hysteresis circuits using differential amplifiers
NASA Technical Reports Server (NTRS)
Cooke, W. A.
1971-01-01
Design equations for hysteresis circuit are based on the following assumptions: amplifier input impedance is larger than source impedance; amplifier output impedance is less than load impedance; and amplifier switches state when differential input voltage is approximately zero. Circuits are designed to any given specifications.
Circuit increases capability of hysteresis synchronous motor
NASA Technical Reports Server (NTRS)
Markowitz, I. N.
1967-01-01
Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain.
Flexible pivot mount eliminates friction and hysteresis
NASA Technical Reports Server (NTRS)
Highman, C. O.
1970-01-01
Flexible steel pivot mount, suspended by flat vertical beryllium copper springs, is capable of rotation, free of hysteresis and starting friction. Mount requires no lubrication, is made in varying sizes, and is driven with either dc torque motor or mechanical linkage.
Thermally induced all-optical inverter and dynamic hysteresis loops in graphene oxide dispersions.
Melle, Sonia; Calderón, Oscar G; Egatz-Gómez, Ana; Cabrera-Granado, E; Carreño, F; Antón, M A
2015-11-01
We experimentally study the temporal dynamics of amplitude-modulated laser beams propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. Nonlinear refraction induced in the sample by thermal effects leads to both phase reversing of the transmitted signals and dynamic hysteresis in the input-output power curves. A theoretical model including beam propagation and thermal lensing dynamics reproduces the experimental findings. PMID:26560566
Modeling and inverse feedforward control for conducting polymer actuators with hysteresis
NASA Astrophysics Data System (ADS)
Wang, Xiangjiang; Alici, Gursel; Tan, Xiaobo
2014-02-01
Conducting polymer actuators are biocompatible with a small footprint, and operate in air or liquid media under low actuation voltages. This makes them excellent actuators for macro- and micro-manipulation devices, however, their positioning ability or accuracy is adversely affected by their hysteresis non-linearity under open-loop control strategies. In this paper, we establish a hysteresis model for conducting polymer actuators, based on a rate-independent hysteresis model known as the Duhem model. The hysteresis model is experimentally identified and integrated with the linear dynamics of the actuator. This combined model is inverted to control the displacement of the tri-layer actuators considered in this study, without using any external feedback. The inversion requires an inverse hysteresis model which was experimentally identified using an inverse neural network model. Experimental results show that the position tracking errors are reduced by more than 50% when the hysteresis inverse model is incorporated into an inversion-based feedforward controller, indicating the potential of the proposed method in enabling wider use of such smart actuators.
High-Precision Hysteresis Sensing of the Quartz Crystal Inductance-to-Frequency Converter.
Matko, Vojko; Milanović, Miro
2016-01-01
A new method for the automated measurement of the hysteresis of the temperature-compensated inductance-to-frequency converter with a single quartz crystal is proposed. The new idea behind this method is a converter with two programmable analog switches enabling the automated measurement of the converter hysteresis, as well as the temperature compensation of the quartz crystal and any other circuit element. Also used is the programmable timing control device that allows the selection of different oscillating frequencies. In the proposed programmable method two different inductances connected in series to the quartz crystal are switched in a short time sequence, compensating the crystal's natural temperature characteristics (in the temperature range between 0 and 50 °C). The procedure allows for the measurement of the converter hysteresis at various values of capacitance connected in parallel with the quartz crystal for the converter sensitivity setting at selected inductance. It, furthermore, enables the measurement of hysteresis at various values of inductance at selected parallel capacitance (sensitivity) connected to the quartz crystal. The article shows that the proposed hysteresis measurement of the converter, which converts the inductance in the range between 95 and 100 μH to a frequency in the range between 1 and 200 kHz, has only 7 × 10(-13) frequency instability (during the temperature change between 0 and 50 °C) with a maximum 1 × 10(-11) hysteresis frequency difference. PMID:27367688
High-Precision Hysteresis Sensing of the Quartz Crystal Inductance-to-Frequency Converter
Matko, Vojko; Milanović, Miro
2016-01-01
A new method for the automated measurement of the hysteresis of the temperature-compensated inductance-to-frequency converter with a single quartz crystal is proposed. The new idea behind this method is a converter with two programmable analog switches enabling the automated measurement of the converter hysteresis, as well as the temperature compensation of the quartz crystal and any other circuit element. Also used is the programmable timing control device that allows the selection of different oscillating frequencies. In the proposed programmable method two different inductances connected in series to the quartz crystal are switched in a short time sequence, compensating the crystal’s natural temperature characteristics (in the temperature range between 0 and 50 °C). The procedure allows for the measurement of the converter hysteresis at various values of capacitance connected in parallel with the quartz crystal for the converter sensitivity setting at selected inductance. It, furthermore, enables the measurement of hysteresis at various values of inductance at selected parallel capacitance (sensitivity) connected to the quartz crystal. The article shows that the proposed hysteresis measurement of the converter, which converts the inductance in the range between 95 and 100 μH to a frequency in the range between 1 and 200 kHz, has only 7 × 10−13 frequency instability (during the temperature change between 0 and 50 °C) with a maximum 1 × 10−11 hysteresis frequency difference. PMID:27367688
NASA Astrophysics Data System (ADS)
Mansanarez, Valentin; Le Coz, Jérôme; Renard, Benjamin; Lang, Michel; Birgand, François
2015-04-01
The hysteresis effect is a hydraulic phenomenon associated with transient flow in a relatively flat channel. Hysteresis leads to non-univocal stage-discharge relationships: for a given stage, discharge during the rising limb is greater than during the recession. Hysteresis occurs in open-channel flows because the velocity pressure wave usually propagates faster than the pressure wave. In practice, hysteresis is often ignored when developing hydrometric rating curves, leading to biased flood hydrographs. When hysteresis is not ignored, the most common practice is to correct the univocal rating curve by using the simple Jones formula. This formula requires the estimation of different physical variables through numerical modelling and/or expertise. The estimation of the associated discharge uncertainty is still an open question. The Bayesian method proposed in this presentation incorporates information from both hydraulic knowledge (equations of channel controls based on geometry and roughness estimates) and stage-discharge observations (gauging data). The obtained total uncertainty combines parametric uncertainty (unknown rating curve parameters) and structural uncertainty (imperfection of the rating curve model). This method provides a direct estimation of the physical inputs of the rating curve (roughness, bed slope, kinematic wave celerity, etc.). Two hysteresis formulas were used: the most widely-used Jones formula and its expansion to the 3rd order, known as the Fenton formula. The wave celerity may be either constant or expressed as a simple function of stage based on the kinematic wave assumption. This method has been applied to one data set. Sensitivity tests allowed us to draw the following conclusions. As expected, more precise hydraulic priors and/or less uncertain gaugings provide rating curves that agree well with discharge measurements and have a smaller uncertainty. The simple Jones formula leads to as good results as the more complex Fenton formula
Calculation of hysteresis losses for Terfenol-D ultrasonic transducer
NASA Astrophysics Data System (ADS)
Zeng, Jianbin; Zeng, Haiquan; Bai, Baodong; Yan, Ming
2009-07-01
Thermal is one of critical factors effecting the application of Terfenol-D ultrasonic magnetostrictive transducer. Hysteresis losses are the main source for heating the it. A new method of hysteresis losses calculation, which based on Jiles-Atherton hysteresis model and electro-magnetic field finite element analysis, is proposed in this paper. The hysteresis losses obtained by this method can be used as thermal sources in electro-thermal finite element analysis of Terfenol-D ultrasonic transducer.
Ganow, H.C.
1985-08-01
The US Bureau of Mines borehole deformation gauge (BMG) was designed in the early 1960`s to allow rock stress measurements by the overcoring method. Since that time it has become a de facto standard against which the performance of other borehole deformation gauges is often judged. However, during recent in situ stress studies in the Climax Stock at the Nevada Test Site a strange "negative hysteresis" in the order of 300 to 500 microstrains was observed in standard calibration data. Here, the relaxation curve lies below the indentation (compression) curves as if the system were to somehow respond with an energy release. Therefore, a precision micro-indentation apparatus has been designed and used to perform a series of tests allowing a better understanding of the BMG button to cantilever interaction. Results indicate that the hysteresis effect is caused by differential motion between the button base and the cantilever resulting from the geometric motion inherent in the cantilever. The very large apparent hysteresis is mainly caused by cycling opposing cantilevers through the instrument`s entire dynamic range, and the fundamental imprecision inherent in use of the standard micrometers to calibrate the BMG. Laboratory mean hysteresis magnitudes for a polished cantilever typically range from 3 to 25 microstrain for 100 and 1000 microstrain relaxations on 1000 microstrain deflection loops intended to simulate typical field data. The error percentage is thought to remain fairly constant with deformation loop size, and is sufficiently small such that it can be safely ignored. The hysteresis effect can probably be reduced, and instrument stability improved by machining a small 90 degree cone in the cantilever in which a slightly larger mating cone on the base of the indentation button would reside. 5 refs. 26 figs., 1 tab.
Analysis of wasp-waisted hysteresis loops in magnetic rocks.
Kharwanlang, R S; Shukla, Prabodh
2012-01-01
The random-field Ising model of hysteresis is generalized to dilute magnets and is solved on a Bethe lattice. Exact expressions for the major and minor hysteresis loops are obtained. In the strongly dilute limit the model provides a simple and useful understanding of the shapes of hysteresis loops in magnetic rock samples. PMID:22400529
Torque meter aids study of hysteresis motor rings
NASA Technical Reports Server (NTRS)
Cole, M.
1967-01-01
Torque meter, simulating hysteresis motor operation, allows rotor ring performance characteristics to be analyzed. The meter determines hysteresis motor torque and actual stresses of the ring due to its mechanical situation and rotation, aids in the study of asymmetries or defects in motor rings, and measures rotational hysteresis.
NASA Astrophysics Data System (ADS)
Mc Namara, Hugh A.; Pokrovskii, Alexei V.
2006-02-01
The Kaldor model-one of the first nonlinear models of macroeconomics-is modified to incorporate a Preisach nonlinearity. The new dynamical system thus created shows highly complicated behaviour. This paper presents a rigorous (computer aided) proof of chaos in this new model, and of the existence of unstable periodic orbits of all minimal periods p>57.
NASA Astrophysics Data System (ADS)
Gershenzon, N. I.; Ritzi, R. W., Jr.; Dominic, D. F.; Mehnert, E.; Okwen, R. T.
2015-12-01
Naum I. Gershenzona, Robert W. Ritzi Jr.a, David F. Dominica, Edward Mehnertb, and Roland T. OkwenbaDepartment of Earth and Environmental Sciences, Wright State University, 3640 Col. Glenn Hwy., Dayton, OH 45435, USAbIllinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 East Peabody Drive, Champaign, IL 61820, USA A number of important candidate CO2 reservoirs exhibit sedimentary architecture reflecting fluvial deposition. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to CO2 injection and storage, led to new geocellular modelling approaches for representing this architecture, and led to new computational studies of CO2 plume dynamics during and after injection. The processes of CO2 trapping depend upon a complex system of non-linear and hysteretic characteristic relationships including how relative permeability and capillary pressure vary with brine and CO2 saturation. New computational studies of capillary trapping in conglomeratic reservoirs strongly suggest that representing small-scale (decimeter to meter) textural facies among different rock types, including their organization within a hierarchy of larger-scale stratification, representing differences in characteristic relationships between rock types, and representing hysteresis in characteristic curves can all be critical to understanding trapping processes. In this context, CO2trapping was evaluated in conglomeratic reservoirs with fluvial architecture including different rock types with different and hysteretic characteristic curves and with capillary pressure defined for each rock type using two different conventional approaches, i.e. Brooks-Corey and van Genuchten. The results show that in these reservoirs the capillary trapping rates are quite sensitive to differences between the Brooks-Corey and van Genuchten approaches, and that
Searcy, James Kincheon
1959-01-01
The flow-duration curve is a cumulative frequency curve that shows the percent of time specified discharges were equaled or exceeded during a given period. It combines in one curve the flow characteristics of a stream throughout the range of discharge, without regard to the sequence of occurrence. If the period upon which the curve is based represents the long-term flow of a stream, the curve may be used to predict the distribution of future flows for water- power, water-supply, and pollution studies. This report shows that differences in geology affect the low-flow ends of flow-duration curves of streams in adjacent basins. Thus, duration curves are useful in appraising the geologic characteristics of drainage basins. A method for adjusting flow-duration curves of short periods to represent long-term conditions is presented. The adjustment is made by correlating the records of a short-term station with those of a long-term station.
One-phase flow in porous media with hysteresis
NASA Astrophysics Data System (ADS)
Botkin, N. D.; Brokate, M.; El Behi-Gornostaeva, E. G.
2016-04-01
This paper presents a numerical simulation of one phase flow through a porous medium showing a hysteretic relation between the capillary pressure and the saturation of the phase. The flow model used is based on mass conservation principle and Darcy's law. Boundary conditions of Neumann and Signorini type are imposed. The hysteretic relation between the capillary pressure and the saturation is described by a Preisach hysteresis operator. A numerical algorithm for the treatment of the arising system of equations is proposed. Results of numerical simulations are presented.
Anomalous hysteresis properties of iron films deposited on liquid surfaces
NASA Astrophysics Data System (ADS)
Ye, Quan-Lin; Feng, Chun-Mu; Xu, Xiao-Jun; Jin, Jin-Sheng; Xia, A.-Gen; Ye, Gao-Xiang
2005-07-01
A nearly free sustained iron film system, deposited on silicone oil surfaces by vapor-phase deposition method, has been fabricated and its crystal structure as well as magnetic properties has been studied. Both the temperature-dependent coercivity Hc(T) and exchange anisotropy field HE(T) of the iron films possess a maximum peak around the critical temperature Tcrit=10-15 and 4K, respectively. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase below freezing temperature Tf=30-50K.
NASA Astrophysics Data System (ADS)
Choi, Seung-Bok; Seong, Min-Sang; Ha, Sung Hoon
2013-04-01
In this work, position control of a one-link flexible arm is undertaken by considering the field-dependent hysteresis behavior of a piezoceramic actuator (piezoactuator in short). The proposed arm is controlled by two actuators: a motor mounted at the hub and a piezoceramic bonded to the surface of the flexible link. In the modeling process, two transfer functions: one from the input torque to output hub angle and the other from the input voltage to the output tip deflection are obtained. The hysteretic behavior of the piezoactuator is experimentally identified using the Preisach model, and the first-order descending (FOD) curves are obtained that are required to design a hysteresis compensator. After establishing the overall control block diagram for the position control of the flexible arm, a quantitative feedback theory (QFT) controller is designed by treating parameter variations and external disturbances as uncertainties. Subsequently, a hysteresis compensator that produces additional control input to the piezoactuator is designed to enhance the vibration control performance. An experimental realization of the proposed control scheme is undertaken and the effect of the hysteresis compensator on vibration control of the flexible arm is evaluated in the time domain.
Lift hysteresis at stall as an unsteady boundary-layer phenomenon
NASA Technical Reports Server (NTRS)
Moore, Franklin K
1956-01-01
Analysis of rotating stall of compressor blade rows requires specification of a dynamic lift curve for the airfoil section at or near stall, presumably including the effect of lift hysteresis. Consideration of the magnus lift of a rotating cylinder suggests performing an unsteady boundary-layer calculation to find the movement of the separation points of an airfoil fixed in a stream of variable incidence. The consideration of the shedding of vorticity into the wake should yield an estimate of lift increment proportional to time rate of change of angle of attack. This increment is the amplitude of the hysteresis loop. An approximate analysis is carried out according to the foregoing ideas for a 6:1 elliptic airfoil at the angle of attack for maximum lift. The assumptions of small perturbations from maximum lift are made, permitting neglect of distributed vorticity in the wake. The calculated hysteresis loop is counterclockwise. Finally, a discussion of the forms of hysteresis loops is presented; and, for small reduced frequency of oscillation, it is concluded that the concept of a viscous "time lag" is appropriate only for harmonic variations of angle of attack with time at mean conditions other than maximum lift.
Wetting Hysteresis at the Molecular Scale
NASA Technical Reports Server (NTRS)
Jin, Wei; Koplik, Joel; Banavar, Jayanth R.
1996-01-01
The motion of a fluid-fluid-solid contact line on a rough surface is well known to display hysteresis in the contact angle vs. velocity relationship. In order to understand the phenomenon at a fundamental microscopic level, we have conducted molecular dynamics computer simulations of a Wilhelmy plate experiment in which a solid surface is dipped into a liquid bath, and the force-velocity characteristics are measured. We directly observe a systematic variation of force and contact angle with velocity, which is single-valued for the case of an atomically smooth solid surface. In the microscopically rough case, however, we find (as intuitively expected) an open hysteresis loop. Further characterization of the interface dynamics is in progress.
Origin of hysteresis in bed form response to unsteady flows
NASA Astrophysics Data System (ADS)
Martin, Raleigh L.; Jerolmack, Douglas J.
2013-03-01
Field and laboratory studies indicate that changes in riverbed morphology often lag changes in water discharge. This lagged response produces hysteresis in the relationship between water discharge and bed form geometry. To understand these phenomena, we performed flume experiments to observe the response of a sand bed to step increases and decreases in water discharge. For an abrupt rise in discharge, we observed that bed forms grew rapidly by collision and merger of bed forms migrating with different celerities. Growth rate slowed as bed forms approached equilibrium with the higher discharge regime. After an abrupt discharge drop, bed form decay occurred through formation of smaller secondary bed forms, in equilibrium with the lower discharge, which cannibalized the original, relict features. We present a simple model framework to quantitatively predict time scales of bed form adjustment to flow changes, based on equilibrium bed form heights, lengths, and celerities at low and high flows. For rising discharge, the model assumes that all bed form collisions result in irreversible merger, due to a dispersion of initial celerities. For falling discharge, we derive a diffusion model for the decay of relict high-stage features. Our models predict the form and time scale of experimental bed form adjustments. Additional experiments applying slow and fast triangular flood waves show that bed form hysteresis occurs only when the time scale of flow change is faster than the modeled (and measured) bed form adjustment time. We show that our predicted adjustment time scales can also be used to predict the occurrence of bed form hysteresis in natural floods.
Electromagnetic phenomena and hysteresis losses in superconductors
NASA Astrophysics Data System (ADS)
Matsushita, T.
Hysteresis losses in superconductors are caused by irreversible motion of fluxoids. This motion is, in most cases, described by the critical state model. In this article, various electromagnetic phenomena due to flux pinning effects are reviewed and explanations of these phenomena are given using the critical state model. The phenomena which cannot be well described by the present model, such as reversible fluxoid motion and the longitudinal field effect, are also introduced.
Vectorized Jiles-Atherton hysteresis model
NASA Astrophysics Data System (ADS)
Szymański, Grzegorz; Waszak, Michał
2004-01-01
This paper deals with vector hysteresis modeling. A vector model consisting of individual Jiles-Atherton components placed along principal axes is proposed. The cross-axis coupling ensures general vector model properties. Minor loops are obtained using scaling method. The model is intended for efficient finite element method computations defined in terms of magnetic vector potential. Numerical efficiency is ensured by differential susceptibility approach.
Two phase flow of liquids in a narrow gap: Phase interference and hysteresis
NASA Astrophysics Data System (ADS)
Raza, Salim; Hejazi, S. Hossein; Gates, Ian D.
2016-07-01
Co-current flow of two immiscible liquids, such as oil and water in a planar fracture, exhibits nonlinear structures which become important in many natural and engineering systems such as subsurface flows, multiphase flows in lubrication joints, and coating flows. In this context, co-current flow of oil and water with variable rates is experimentally studied in a Hele-Shaw cell, various flow regimes are classified, and relative permeabilities for the phases are analysed thoroughly. Similar to multiphase pipe flows, multiphase flow in planar gaps shows various flow regimes, each having different flow rate/pressure gradient behaviour. As well as recovering the known results in the immiscible displacements in Hele-Shaw cell where the fluid-fluid interface remains stable/unstable for favorable/adverse viscosity ratios, it is found that the co-current flow of two fluids with different viscosities results in three distinct flow regimes. Before breakthrough of non-wetting phase, i.e, water, a "linear displacement" flow regime initially establishes at very low water injection rates. This stable movement turns into a "fingering advancement" flow regime at high water flow rates and Saffman-Taylor instability develops normal to the direction of the flow. After the breakthrough, a "droplet formation" flow regime is identified where the droplets of wetting phase, oil, are trapped in the water phase. For subsurface flow applications, we quantify these regimes through relative permeability curves. It is reported that as the water flow rate increases, the relative permeabilities and flow channels become smooth and regular. This behaviour of relative permeability and saturations shows dominance of capillary forces at low flow rates and viscous forces at higher flow rates. Variable injection rates provide the interface structures for both drainage and imbibition process, where the wetting phase saturation decreases and increases respectively. It is shown that relative permeability
NASA Astrophysics Data System (ADS)
Luo, Jie-Xin; Chen, Jing; Chai, Zhan; Lü, Kai; He, Wei-Wei; Yang, Yan; Wang, Xi
2014-12-01
The impact of shallow trench isolation (STI) mechanical stress on the hysteresis effect in the output characteristics is measured in partially depleted (PD) silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistors (MOSFETs). We develop ID hysteresis, which is defined as the difference between ID versus VD forward sweep and reverse sweep. The fabricated devices show positive and negative peaks in ID hysteresis. The experimental results show that ID hysteresis declined as the STI mechanical stress increases. We also elaborate on the impact of STI mechanical stress on the ID hysteresis of PD SOI n-type MOSFETs.
NASA Astrophysics Data System (ADS)
Lewis, L. H.; Gao, J.; Jiles, D. C.; Welch, D. O.
1996-04-01
The Jiles-Atherton theory is based on considerations of the dependence of energy dissipation within a magnetic material resulting from changes in its magnetization. The algorithm based on the theory yields five computed model parameters, MS, a, α, k, and c, which represent the saturation magnetization, the effective domain density, the mean exchange coupling between the effective domains, the flexibility of domain walls and energy-dissipative features in the microstructure, respectively. Model parameters were calculated from the algorithm and linked with the physical attributes of a set of three related melt-quenched permanent magnets based on the Nd2Fe14B composition. Measured magnetic parameters were used as inputs into the model to reproduce the experimental hysteresis curves. The results show that two of the calculated parameters, the saturation magnetization MS and the effective coercivity k, agree well with their directly determined analogs. The calculated a and α parameters provide support for the concept of increased intergranular exchange coupling upon die upsetting, and decreased intergranular exchange coupling with the addition of gallium.
Hysteresis and bristle stiffening effects in brush seals
NASA Astrophysics Data System (ADS)
Basu, P.; Datta, A.; Loewenthal, R.; Short, J.; Johnson, R.
1994-07-01
Extensive testing of conventional brush seals has identified the phenomena of bristle 'hysteresis' and 'stiffening' with pressure as their two major drawbacks. Subsequent to any differential movement of the runner into the bristle pack due to its radial excursions or centrifugal/thermal growths, the displaced bristles do not recover against the frictional forces between them and the backing plate. As a result, a significant leakage increase is observed following any runner movement. Furthermore, the bristle pack exhibits a considerable stiffening effect with the application of pressure. This phenomenon may adversely affect the life of the seal and the runner due to a highly increased mechanical contact pressure at the sliding interface. In comparison with these conventional design seals, the characteristics of an improved design, known as the 'low hysteresis' design, are presented here. This design shows a substantially lower degree of the detrimental effects mentioned above. This type of seal can maintain its reduced leakage characteristics throughout the running cycle with runner excursions and growths. The bristles also do not show any stiffening, up to a certain pressure threshold. Therefore, this seal also has a potential for a longer life than a brush seal of conventional design.
Hysteresis and bristle stiffening effects of conventional brush seals
NASA Astrophysics Data System (ADS)
Basu, P.; Datta, A.; Johnson, R.; Loewenthal, R.; Short, J.
1993-06-01
Extensive testing of conventional brush seals has identified the phenomena of bristle 'hysteresis' and 'stiffening' with pressure as their two major drawbacks. Subsequent to any differential movement of the runner into the bristle pack due to its radial excursions or centrifugal/thermal growths, the displaced bristles do not recover against the frictional forces between them and the backing plate. As a result, a significant leakage increase is observed following any runner movement. Furthermore, the bristle pack exhibits a considerable stiffening effect with the application of pressure. This phenomenon adversely affects the life of the seal and the runner due to a highly increased mechanical contact pressure at the sliding interface. In comparison with these conventional design seals, the characteristics of an improved design, known as the 'low hysteresis' design, are presented here. This design shows a substantially lower degree of the detrimental effects mentioned above. This type of seal can maintain its reduced leakage characteristics throughout the running cycle with runner excursions and growths. The bristles also do not show any stiffening, up to a certain pressure threshold. Therefore, this seal also has a potential for a longer life than a brush seal of conventional design.
NASA Astrophysics Data System (ADS)
Briggs, M. A.; Day-Lewis, F. D.; Zarnetske, J. P.; Harvey, J. W.; Lane, J. W., Jr.
2015-12-01
Heterogeneous streambed materials may be expected to develop two general porosity domains: a more-mobile porosity dominated by advective exchange, and a less-mobile porosity dominated by diffusive exchange. Less-mobile porosity containing unique redox conditions or contaminant mass may be invisible to traditional porewater sampling methods, even using "low-flow" techniques, because these methods sample water preferentially from the mobile porosity domain. Further, most tracer breakthrough curve analyses have only provided indirect information (tailing) regarding the prevalence and connectivity of less-mobile porosity, typically over experimental flowpath scales between 1-10 meters. To address the limitations of conventional methods, we use electrical geophysical methods to aid in the inference of less-mobile porosity parameters. Unlike traditional fluid sampling, electrical methods can directly sense less-mobile solute and can target specific points along subsurface flowpaths. We demonstrate how the geophysical methodology developed for dual-domain groundwater transport can be scaled to the streambed through synthetic, laboratory column, and field experiments; further we show how previously-used numerical modeling techniques can be replaced by a more-simple analytical approach. The new analytical method is based on electrical theory, and involves characteristics of electrical hysteresis patterns (e.g. hinge point values) that are used to quantify (1) the size of paired mobile and less-mobile porosities, and (2) the exchange rate coefficient through simple curve fitting. Results from the analytical approach compare favorably with results from calibration of numerical models and also independent measurements of mobile and less-mobile porosity. Lastly, we demonstrate a method of focused solute streambed injection to quantify less-mobile porosity and explain redox zonation in contrasting stream environments.
Thermal hysteresis of permeability and transport properties of Mn substituted Mg Cu Zn ferrites
NASA Astrophysics Data System (ADS)
Manjurul Haque, M.; Huq, M.; Hakim, M. A.
2008-03-01
Mn substituted Mg-Cu-Zn ferrites of composition Mg0.35Cu0.20Zn0.45O(Fe2-xMnx O3)0.97 have been prepared by the standard double sintering ceramic technique. X-ray diffraction patterns of the samples showed single phase cubic spinel structure without any detectable impurity phases. The lattice constant is found to increase linearly with increase in Mn3+ ion concentration obeying Vegard's law. The initial permeability (μi) of the Mg-Cu-Zn ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature TC to below. The sharp decrease of μi at T = TC indicates that the samples have high homogeneity according to Globus et al. The Curie temperature TC of the studied ferrite system was determined from the μi-T curves where the Hopkinson type of effect at the TC has been observed with the manifestation of a sharp fall in permeability. The Curie temperature TC is found to increase with increasing Mn content. Dc electrical resistivity increases significantly with the increase in Mn content. The ac resistivity (ρac) and dielectric constant (ɛ') of the samples are found to decrease with increase in frequency, exhibiting normal ferrimagnetic behaviour. Dielectric relaxation peaks were observed for the frequency dependence of dielectric loss tangent curves. ɛ' increases as the temperature increases, which is the normal dielectric behaviour of the magnetic semiconductor ferrite. The observed variation of electrical and dielectric properties are explained on the basis of Fe2+/Fe3+ ionic concentration as well as the electronic hopping frequency between Fe2+ and Fe3+ ions in the present samples.
Revisiting hydraulic hysteresis based on long-term monitoring of hydraulic states in lysimeters
NASA Astrophysics Data System (ADS)
Hannes, M.; Wollschläger, U.; Wöhling, T.; Vogel, H.-J.
2016-05-01
Hysteretic processes have been recognized for decades as an important characteristic of soil hydraulic behavior. Several studies confirmed that wetting and drying periods cannot be described by a simple functional relationship, and that some nonequilibrium of the water retention characteristics has to be taken into account. A large number of models describing the hysteresis of the soil water retention characteristic were successfully tested on soil cores under controlled laboratory conditions. However, its relevance under field conditions under natural forcings has rarely been investigated. In practice, the modeling of field soils usually neglects the hysteretic nature of soil hydraulic properties. In this study, long-term observations of water content and matric potential in lysimeters of the lysimeter network TERENO-SoilCan are presented, clearly demonstrating the hysteretic behavior of field soils. We propose a classification into three categories related to different time scales. Based on synthetic and long-term monitoring data, three different models of hysteresis were applied to data sets showing different degrees of hysteresis. We found no single model to be superior to the others. The model ranking depended on the degree of hysteresis. All models were able to reflect the general structure of hysteresis in most cases but failed to reproduce the detailed trajectories of state variables especially under highly transient conditions. As an important result we found that the temporal dynamics of wetting and drying significantly affects these trajectories which should be accounted for in future model concepts.
Studies of hysteresis in two-dimensional kinetic Ising model using the FORC technique
NASA Astrophysics Data System (ADS)
Robb, Daniel; Novotny, Mark; Rikvold, Per Arne
2004-03-01
We describe the FORC (first order reversal curve) technique [1] for hysteresis, first developed as an experimental method to better characterize magnetic materials, and present FORC distributions for simulations of a square-lattice kinetic Ising model. To understand the simulation results, we apply a theory of magnetization reversal for the multidroplet (MD) regime [2] for homogeneous nucleation and growth, also called the Kolmogorov-Johnson-Mehl-Avrami regime. The FORC `partial hysteresis' loops exhibit different properties than those of systems with strong disorder [1]. We compare the simulation and the theory for several lattice sizes, frequencies of the external field, and temperatures. [1] C.R. Pike, A.P. Roberts, and K.L. Verosub, J. Appl. Phys. 85, 6660 (1999). [2] S.W. Sides, P.A. Rikvold, and M.A. Novotny, Phys. Rev. E 59, 2710 (1999).
Conformational Electroresistance and Hysteresis in Nanoclusters
Li, Xiangguo; Zhang, Xiaoguang; Cheng, Hai-Ping
2014-07-02
Among many mechanisms proposed for electroresistance, ones involving structural changes are the least understood because of challenges of controllability and repeatability. Yet structural changes can cause dramatic changes in electronic properties, leading to multiple ways in which conduction paths can be opened and closed, not limited to filament movement or variation in molecular conductance. Here we show at least another way: conformational dependence of the Coulomb charging energy of a nanocluster, where charging induced conformational distortion changes the blockade voltage, which in turn leads to a giant electroresistance. This intricate interplay between charging and conformation change is demonstrated in a nanocluster Zn3O4 by combining a first-principles calculation with a temperature dependent transport model. The predicted hysteretic Coulomb blockade staircase in the current-voltage curve adds another dimension to the rich phenomenon of tunneling electroresistance. The new mechanism also provides a better controlled and repeatable platform to study conformational electroresistance.
Conformational Electroresistance and Hysteresis in Nanoclusters
Li, Xiangguo; Zhang, Xiaoguang; Cheng, Hai-Ping
2014-07-02
Among many mechanisms proposed for electroresistance, ones involving structural changes are the least understood because of challenges of controllability and repeatability. Yet structural changes can cause dramatic changes in electronic properties, leading to multiple ways in which conduction paths can be opened and closed, not limited to filament movement or variation in molecular conductance. Here we show at least another way: conformational dependence of the Coulomb charging energy of a nanocluster, where charging induced conformational distortion changes the blockade voltage, which in turn leads to a giant electroresistance. This intricate interplay between charging and conformation change is demonstrated in amore » nanocluster Zn3O4 by combining a first-principles calculation with a temperature dependent transport model. The predicted hysteretic Coulomb blockade staircase in the current-voltage curve adds another dimension to the rich phenomenon of tunneling electroresistance. The new mechanism also provides a better controlled and repeatable platform to study conformational electroresistance.« less
Hysteresis prediction inside magnetic shields and application.
Morić, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe
2014-07-01
We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission. PMID:25085183
Hysteresis prediction inside magnetic shields and application
NASA Astrophysics Data System (ADS)
Morić, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe
2014-07-01
We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission.
Hysteresis prediction inside magnetic shields and application
Morić, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe
2014-07-15
We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission.
Mechano-electric optoisolator transducer with hysteresis
NASA Astrophysics Data System (ADS)
Ciuruş, I. M.; Dimian, M.; Graur, A.
2011-01-01
This article presents a theoretical and experimental study of designing a mechano-electric optoisolator transducer with hysteresis. Our research is centred upon designing transducers on the basis of optical sensors, as photoelectric conversions eliminate the influence of electromagnetic disturbances. Conversion of the rotation/translation motions into electric signals is performed with the help of a LED-photoresistor Polaroid optocoupler. The driver of the optocoupler's transmitter module is an independent current source. The signal conditioning circuit is a Schmitt trigger circuit. The device is designed to be applied in the field of automation and mechatronics.
Hysteresis modeling of synchronous reluctance motor considering PWM input voltage
NASA Astrophysics Data System (ADS)
Lee, J. H.; Kim, J. C.; Hyun, D. S.
2000-01-01
This paper deals with the hysteresis characteristics analysis in PWM fed synchronous reluctance motor (SynRM) using a coupled finite element method (FEM) and Preisach's modeling, which is presented to analyze the characteristics under the effect of saturation and hysteresis loss. With regard to the PWM characteristics, a vector control inverter is combined with an analysis tool. Also, a moving mesh technique is used with regard to rotation due to velocity. The focus of this paper is the applied method of Preisach modeling for rotating machines and the characteristics analysis of a SynRM using the proposed method of analysis. For the propriety of proposed method of analysis, TMS320C31 DSP-installed experimental devices are used. And then, computer simulation and experimental result for the i- λ loci, speed, current response, show the propriety of the proposed method. The characteristic analysis is performed in relation to the maximum efficiency condition for a SynRM in simulation and experiment.
Magnetic hysteresis, compensation behaviors, and phase diagrams of bilayer honeycomb lattices
NASA Astrophysics Data System (ADS)
Ersin, Kantar
2015-10-01
Magnetic behaviors of the Ising system with bilayer honeycomb lattice (BHL) structure are studied by using the effective-field theory (EFT) with correlations. The effects of the interaction parameters on the magnetic properties of the system such as the hysteresis and compensation behaviors as well as phase diagrams are investigated. Moreover, when the hysteresis behaviors of the system are examined, single and double hysteresis loops are observed for various values of the interaction parameters. We obtain the L-, Q-, P-, and S-type compensation behaviors in the system. We also observe that the phase diagrams only exhibit the second-order phase transition. Hence, the system does not show the tricritical point (TCP).
Hysteresis in single-layer MoS2 field effect transistors.
Late, Dattatray J; Liu, Bin; Matte, H S S Ramakrishna; Dravid, Vinayak P; Rao, C N R
2012-06-26
Field effect transistors using ultrathin molybdenum disulfide (MoS(2)) have recently been experimentally demonstrated, which show promising potential for advanced electronics. However, large variations like hysteresis, presumably due to extrinsic/environmental effects, are often observed in MoS(2) devices measured under ambient environment. Here, we report the origin of their hysteretic and transient behaviors and suggest that hysteresis of MoS(2) field effect transistors is largely due to absorption of moisture on the surface and intensified by high photosensitivity of MoS(2). Uniform encapsulation of MoS(2) transistor structures with silicon nitride grown by plasma-enhanced chemical vapor deposition is effective in minimizing the hysteresis, while the device mobility is improved by over 1 order of magnitude. PMID:22577885
Hysteresis of transient populations in absorbing-state systems
NASA Astrophysics Data System (ADS)
Kapitanchuk, Oleksiy L.; Marchenko, Oleksij M.; Teslenko, Victor I.
2016-06-01
A nonequilibrium density matrix theory is used in order to explicitly describe the hysteresis interrelation between populations of nonstationary states in an absorbing multi-stage chain system in the one-particle approximation. As an illustrative example, we restrict ourselves to consideration of the 3-stage absorbing case for which we identify three types of the hysteresis; that is, the causal time dependent hysteresis with leaf-like and triangle-like closed loops, the hidden hysteresis with broken-line loops and the true hysteresis with open loops. Furthermore, we observe a common critical threshold for the hysteresis types and ascertain a reciprocal correspondence of this threshold as between the types as well with the experiment.
NASA Astrophysics Data System (ADS)
Jiang, Jun; Yu, Tian; Pan, Rui; Zhang, Qin-Tong; Liu, Pan; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Han, Xiufeng
2016-06-01
The exchange bias (EB) is an effective fundamental and applicational method to realize magnetic hysteresis loop shifting. However, further manipulation of EB unidirectional anisotropy is difficult after setup using either field deposition or post-annealing. In this work, we experimentally show a new approach to control the magnetic hysteresis loop bias in a [Co(0.2)/Pd(1)]5/CoFeB orthogonal exchange-spring (ES) coupling system, where the direction and strength of unidirectional anisotropy can be easily manipulated by applying an external magnetic field.
Li, Yi; Xu, Ben; Hu, Shenyang Y.; Li, Yulan; Li, Qiulin; Liu, Wei
2015-09-25
Hysteresis loops and Magnetic Barkhausen Noise in a single crystal α-iron containing a nonmagnetic particle were simulated based on the Laudau-Lifshitz-Gilbert equation. The analyses of domain morphologies and hysteresis loops show that reversal magnetization process is control by nucleation of reversed domains at nonmagnetic particle when the particle size reaches a particle value. In such a situation, the value of nucleation field is determined by the size of nonmagnetic particles, and moreover, coercive field and Magnetic Barkhausen Noise signal are strongly affected by the nucleation field of reversed domains.
Hysteresis compensation and trajectory preshaping for piezoactuators in scanning applications
NASA Astrophysics Data System (ADS)
Liu, Yanfang; Shan, Jinjun; Gabbert, Ulrich; Qi, Naiming
2014-01-01
This paper focuses on the dynamics and control of piezoactuators (PEAs) for high-speed large-range scanning applications. Firstly, the nonlinear hysteresis is modeled by using a modified Maxwell resistive capacitor (MRC) model. Secondly, an inverse-based feedforward controller is proposed for this application with hysteresis compensation. Then, the scanning trajectories are preshaped by treating the hysteresis-compensated PEA as a linear system. Finally, experiments are conducted to verify the effectiveness of the proposed approaches.
Method and apparatus for sub-hysteresis discrimination
De Geronimo, Gianluigi
2015-12-29
Embodiments of comparator circuits are disclosed. A comparator circuit may include a differential input circuit, an output circuit, a positive feedback circuit operably coupled between the differential input circuit and the output circuit, and a hysteresis control circuit operably coupled with the positive feedback circuit. The hysteresis control circuit includes a switching device and a transistor. The comparator circuit provides sub-hysteresis discrimination and high speed discrimination.
NASA Astrophysics Data System (ADS)
Shoushtari, Seyed Mohammad Hossein Jazayeri; Cartwright, Nick; Perrochet, Pierre; Nielsen, Peter
2015-12-01
In this paper, the influence of hysteresis on water table dynamics in an unconfined aquifer was examined using a numerical model to solve Richards' unsaturated flow equation. The model was subject to simple harmonic forcing across a sloping boundary with a seepage face boundary condition. Time series from both hysteretic and non-hysteretic models were subject to harmonic analysis to extract the amplitude and phase profiles for comparison with existing sand flume data (Cartwright et al., 2004). The results from both model types show good agreement with the data indicating no influence of hysteresis at the oscillation period examined (T = 348 s). The models were then used to perform a parametric study to examine the relationship between oscillation period and hysteresis effects with periods ranging from 3 min to 180 min. At short oscillation periods, (T ≈ 180 s) the effects of hysteresis were negligible with both models providing similar results. As the oscillation period increased, the hysteretic model showed less amplitude damping than the non-hysteretic model. For periods greater than T = 60 min, the phase lag in the non-hysteretic model is greater than for the hysteretic one. For periods less than T = 60 min this trend is reversed and the hysteretic model produced a greater phase lag than the non-hysteretic model. These findings suggest that consideration of hysteresis dynamics in Richards' equation models has no influence on water table wave dispersion for short period forcing such as waves (T ≈ 10 s) whereas for long period forcing such as tides (T ≈ 12.25 h) or storm surges (T ≈ days) hysteresis dynamics should be taken into account.
An inclusive model of ferromagnetic hysteresis
NASA Astrophysics Data System (ADS)
Phelps, Brian Fletcher
A new inclusive macroscopic model of ferromagnetic hysteresis is proposed. The model is developed from a Stoner-Wohlfarth approach by adding mean field or nearest neighbour dipole-dipole interactions. Pinning of domain rotation is also postulated, and a rotational pinning extension included. The model includes the principal features of the Jiles-Atherton model in the previous Atherton-Beattie extension of the Stoner-Wohlfarth model, but still omits the domain wall energy effects included in the Globus model. The new model describes both reversible and irreversible processes, and hysteresis caused by combinations of interaction, anisotropy, and pinning. Computational approaches to both two and three dimensional calculations are detailed, and examples given. Simulations of hard magnetic materials are done, including major loops to near saturation, minor loops, and demagnetizations. The complete 2 x 2 magnetization tensor response is shown, including fan diagram representations. The minor loop simulations involve complicated sets of field turning points typical of the Preisach model, and the minor loops are seen to exhibit incongruence and eventual closure. The demagnetization simulations are done for both rotating and oscillating applied field cycles. Both isotropic and anisotropic polycrystalline easy axis distributions are treated.
Effects of Hysteresis on Groundwater Recharge From Ephemeral Flows
NASA Astrophysics Data System (ADS)
Parissopoulos, G. A.; Wheater, H. S.
1992-11-01
The effects of hysteresis on the movement of the saturated and unsaturated soil water phase due to infiltration from ephemeral surface water flows are investigated for different scenarios of flood events in homogeneous and heterogeneous media with the use of a two-dimensional model based on Richards' equation and the dependent domain hysteresis model of Mualem (1984). Hysteresis effects were found in general to be small, but sensitive to water ponding depth, hydraulic contact between surface and groundwater and initial moisture distribution. In all cases tested, hysteresis resulted in higher rise of the toe of the water mound formed beneath the wadi despite a decrease of cumulative infiltration.
Dynamic hysteresis modeling including skin effect using diffusion equation model
NASA Astrophysics Data System (ADS)
Hamada, Souad; Louai, Fatima Zohra; Nait-Said, Nasreddine; Benabou, Abdelkader
2016-07-01
An improved dynamic hysteresis model is proposed for the prediction of hysteresis loop of electrical steel up to mean frequencies, taking into account the skin effect. In previous works, the analytical solution of the diffusion equation for low frequency (DELF) was coupled with the inverse static Jiles-Atherton (JA) model in order to represent the hysteresis behavior for a lamination. In the present paper, this approach is improved to ensure the reproducibility of measured hysteresis loops at mean frequency. The results of simulation are compared with the experimental ones. The selected results for frequencies 50 Hz, 100 Hz, 200 Hz and 400 Hz are presented and discussed.
NASA Astrophysics Data System (ADS)
Aljanaideh, Omar; Habineza, Didace; Rakotondrabe, Micky; Al Janaideh, Mohammad
2016-04-01
An experimental study has been carried out to characterize rate-dependent hysteresis of a piezoelectric tube actuator at different excitation frequencies. The experimental measurements were followed by modeling and compensation of the hysteresis nonlinearities of the piezoelectric tube actuator using both the inverse rate-dependent Prandtl-Ishlinskii model (RDPI) and inverse rate-independent Prandtl-Ishlinskii model (RIPI) coupled with a controller. The comparison of hysteresis modeling and compensation of the actuator with both models is presented.
Highly curved microchannel plates
NASA Technical Reports Server (NTRS)
Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.
1990-01-01
Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.
Harrison, S M; Lamont, C; Miller, D J
1988-01-01
1. The relationship between pCa (-log10[Ca2+]) and steady-state isometric tension has been investigated in saponin- or Triton-treated (chemically 'skinned') cardiac muscle of rat. 2. Hysteresis exists in the relationship such that the muscle is less sensitive to Ca2+ during increasing activation (as [Ca2+] is stepped upward) than during reducing activation (as [Ca2+] is stepped downward). 3. The extent of the hysteresis is insensitive to interventions that increase overall calcium sensitivity by chemical means, such as caffeine, carnosine or increased pH. 4. The extent of the hysteresis is sensitive to sarcomere length. The phenomenon is virtually absent above sarcomere lengths of about 2.2-2.3 microns but becomes progressively greater at shorter sarcomere lengths. 5. The effect of sarcomere length on calcium sensitivity is restricted to the upward-going (increasing activation) part of the pCa-tension loop below 2.2 microns. The downward-going (decreasing activation) part of the hysteretic relationship is virtually unaffected by sarcomere length up to 2.2 microns. 6. Significant alterations in sarcomere length do not occur during tension development in the experiments described here: the phenomenon is not attributable to experimental artifacts of this kind. 7. Hysteresis develops sufficiently rapidly to be consistent with a physiological relevance during the normal heart beat. 8. The effects of sarcomere length show that the phenomenon is not due to force per se since, for example, greater peak force produces less hysteresis as sarcomere length is increased towards 2.2 microns. 9. Tonicity increase (by high-molecular-weight dextran), which shrinks the myofilament lattice, increases calcium sensitivity but reduces the effect of sarcomere length on calcium sensitivity. 10. The results suggest that lattice shrinkage is the mechanism which accounts for hysteresis in, and the sarcomere length dependence of, calcium sensitivity in cardiac muscle. Images Fig. 1 Fig. 11
ERIC Educational Resources Information Center
Gehring, John
2004-01-01
For the past 16 years, the blue-collar city of Huntington, West Virginia, has rolled out the red carpet to welcome young wrestlers and their families as old friends. They have come to town chasing the same dream for a spot in what many of them call "The Show". For three days, under the lights of an arena packed with 5,000 fans, the state's best…
A new index to quantify hysteresis at the runoff event timescale
NASA Astrophysics Data System (ADS)
Zuecco, Giulia; Penna, Daniele; van Meerveld, Ilja; Borga, Marco
2015-04-01
hysteresis by the index allowed for the robust classification of hysteresis in datasets and thus to determine differences in hydrological responses for different events. The index also captured the switch in the direction of the hysteretic relation between soil moisture and streamflow with changes in event size and antecedent wetness conditions well. Finally, the sensitivity analyses showed that the index was little affected by the temporal resolution of the measurements and random errors in the input data. Keywords: hysteresis index; hysteretic loops; streamflow; soil moisture; seasonal dynamics; sensitivity analysis
A Hysteresis Model for Piezoceramic Materials
NASA Technical Reports Server (NTRS)
Smith, Ralph C.; Ounaies, Zoubeida
1999-01-01
This paper addresses the modeling of nonlinear constitutive relations and hysteresis inherent to piezoceramic materials at moderate to high drive levels. Such models are, necessary to realize the, full potential of the materials in high performance control applications, and a necessary prerequisite is the development of techniques which permit control implementation. The approach employed here is based on the qualification of reversible and irreversible domain wall motion in response to applied electric fields. A comparison with experimental data illustrates that because the resulting ODE model is physics-based, it can be employed for both characterization and prediction of polarization levels throughout the range of actuator operation. Finally, the ODE formulation is amenable to inversion which facilitates the development of an inverse compensator for linear control design.
Hysteresis of misaligned hard-soft grains
NASA Astrophysics Data System (ADS)
Wan, X. L.; Zhao, G. P.; Zhang, X. F.; Xia, J.; Zhang, X. C.; Morvan, F. J.
2016-01-01
The demagnetization process in hard/soft multilayer systems has been investigated systematically within a self-contained micromagnetic model when a deviation angle β between the easy axis and the applied field exists. Hysteresis loops, spin distributions and energy products have been calculated with a finite hard layer thickness th. Both remanence and coercivity of the multilayer system decrease as β increases, leading to a significant decrease of the maximum energy product. A 30° deviation of the easy axis could result in a drop of the maximum energy product by more than 60%, which offers a possible explanation on the large discrepancy between the experimental and theoretical energy products. The effect of the finite hard layer thickness on the demagnetization process is important, which can only be ignored when th is large enough.
Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola
2016-01-01
Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique. PMID:27426442
Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola
2016-01-01
Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique. PMID:27426442
NASA Astrophysics Data System (ADS)
Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola
2016-07-01
Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique.
Circuit measures hysteresis loop areas at 30 Hz
NASA Technical Reports Server (NTRS)
Hoffman, C.; Spilo, D.
1967-01-01
Analog circuit measures hysteresis loop areas as a function of time during fatigue testing of specimens subjected to sinusoidal tension-compression stresses at a frequency of Hz. When the sinusoidal stress signal is multiplied by the strain signal, the dc signal is proportional to hysteresis loop area.
Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics
NASA Astrophysics Data System (ADS)
Lefebvre, J.; Ding, J.; Li, Z.; Cheng, F.; Du, N.; Malenfant, P. R. L.
2015-12-01
We present two examples of carbon nanotube network thin film transistors with strongly hydrophobic dielectrics comprising either Teflon-AF or a poly(vinylphenol)/poly(methyl silsesquioxane) (PVP/pMSSQ) blend. In the absence of encapsulation, bottom gated transistors in air ambient show no hysteresis between forward and reverse gate sweep direction. Device threshold gate voltage and On-current present excellent time dependent stability even under dielectric stress. Furthermore, threshold gate voltage for hole conduction is negative upon device encapsulation with PVP/pMSSQ enabling much improved current On/Off ratio at 0 V. This work addresses two major challenges impeding solution based fabrication of relevant thin film transistors with printable single-walled carbon nanotube channels.
Adhesion hysteresis of a film-terminated fibrillar array
NASA Astrophysics Data System (ADS)
Yan, ShunPing; He, LingHui; Wang, HuiJing
2012-06-01
Motivated by the recent biomimic design of microstructured adhesive surfaces, we study adhesion between a film-terminated fibrillar array and a rigid substrate. Using a two-dimensional model and ignoring the deformation of the fibers and the backing layer, we show that the adhesion behavior is dominated by a dimensionless parameter reflecting the global flexibility of the terminal film. In particular, if the parameter is larger than 0.4, the adhesion is reversible; otherwise one or more hysteresis loops will appear after an approach-retraction cycle, leading to significant increase in the specific separation work. The result is expected to help not only optimal design of the structure, but also other applications such as micro-manipulation in micromechanical systems.
Hysteresis loops of spin-dependent electronic current in a paramagnetic resonant tunnelling diode
NASA Astrophysics Data System (ADS)
Wójcik, P.; Spisak, B. J.; Wołoszyn, M.; Adamowski, J.
2012-11-01
Nonlinear properties of the spin-dependent electronic transport through a semiconductor resonant tunnelling diode with a paramagnetic quantum well are considered. The spin-dependent Wigner-Poisson model of the electronic transport and the two-current Mott’s formula for the independent spin channels are applied to determine the current-voltage curves of the nanodevice. Two types of the electronic current hysteresis loops are found in the current-voltage characteristics for both the spin components of the electronic current. The physical interpretation of these two types of the electronic current hysteresis loops is given based on the analysis of the spin-dependent electron densities and the potential energy profiles. The differences between the current-voltage characteristics for both the spin components of the electronic current allow us to explore the changes of the spin polarization of the current for different electric fields and determine the influence of the electronic current hysteresis on the spin polarization of the current flowing through the paramagnetic resonant tunnelling diode.
Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki
2016-01-01
Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed. PMID:27435309
Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki
2016-01-01
Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed. PMID:27435309
Tan, U-Xuan; Latt, Win Tun; Shee, Cheng Yap; Riviere, Cameron N; Ang, Wei Tech
2009-10-01
Piezoelectric, magnetostrictive, and shape memory alloy actuators are gaining importance in high-frequency precision applications constrained by space. Their intrinsic hysteretic behavior makes control difficult. The Prandtl-Ishlinskii (PI) operator can model hysteresis well, albeit a major inadequacy: the inverse operator does not exist when the hysteretic curve gradient is not positive definite, i.e., ill condition occurs when slope is negative. An inevitable tradeoff between modeling accuracy and inversion stability exists. The hysteretic modeling improves with increasing number of play operators. But as the piecewise continuous interval of each operator reduces, the model tends to be ill-conditioned, especially at the turning points. Similar ill-conditioned situation arises when these actuators move heavy loads or operate at high frequency. This paper proposes an extended PI operator to map hysteresis to a domain where inversion is well behaved. The inverse weights are then evaluated to determine the inverse hysteresis model for the feedforward controller. For illustration purpose, a piezoelectric actuator is used. PMID:19936032
NASA Astrophysics Data System (ADS)
Shimazu, Yoshihiro; Tashiro, Mitsuki; Sonobe, Satoshi; Takahashi, Masaki
2016-07-01
Molybdenum disulfide (MoS2) has recently received much attention for nanoscale electronic and photonic applications. To explore the intrinsic properties and enhance the performance of MoS2-based field-effect transistors, thorough understanding of extrinsic effects such as environmental gas and contact resistance of the electrodes is required. Here, we report the effects of environmental gases on the transport properties of back-gated multilayered MoS2 field-effect transistors. Comparisons between different gases (oxygen, nitrogen, and air and nitrogen with varying relative humidities) revealed that water molecules acting as charge-trapping centers are the main cause of hysteresis in the transfer characteristics. While the hysteresis persisted even after pumping out the environmental gas for longer than 10 h at room temperature, it disappeared when the device was cooled to 240 K, suggesting a considerable increase in the time constant of the charge trapping/detrapping at these modestly low temperatures. The suppression of the hysteresis or instability in the easily attainable temperature range without surface passivation is highly advantageous for the device application of this system. The humidity dependence of the threshold voltages in the transfer curves indicates that the water molecules dominantly act as hole-trapping centers. A strong dependence of the on-state current on oxygen pressure was also observed.
Modeling Loading/Unloading Hysteresis Behavior of Unidirectional C/SiC Ceramic Matrix Composites
NASA Astrophysics Data System (ADS)
Longbiao, Li; Yingdong, Song; Youchao, Sun
2013-08-01
The loading/unloading tensile behavior of unidirectional C/SiC ceramic matrix composites at room temperature has been investigated. The loading/unloading stress-strain curve exhibits obvious hysteresis behavior. An approach to model the hysteresis loops of ceramic matrix composites including the effect of fiber failure during tensile loading has been developed. By adopting a shear-lag model which includes the matrix shear deformation in the bonded region and friction in the debonded region, the matrix cracking space and interface debonded length are obtained by matrix statistical cracking model and fracture mechanics interface debonded criterion. The two-parameter Weibull model is used to describe the fiber strength distribution. The stress carried by the intact and fracture fibers on the matrix crack plane during unloading and subsequent reloading is determined by the Global Load Sharing criterion. Based on the damage mechanisms of fiber sliding relative to matrix during unloading and subsequent reloading, the unloading interface reverse slip length and reloading interface new slip length are obtained by the fracture mechanics approach. The hysteresis loops of unidirectional C/SiC ceramic matrix composites corresponding to different stress have been predicted.
Co/Cu multilayers with reduced magnetoresistive hysteresis
NASA Astrophysics Data System (ADS)
Kubinski, D. J.; Holloway, H.
1997-01-01
Practical applications of Co/Cu multilayers (MLs) require copper thicknesses either ≈ 9 Å or ≈ 20 Å corresponding to the first or second antiferromagnetic maximum (AFM). The first AFM has much smaller magnetoresistive hysteresis than the second, but also has lower sensitivity. We discuss application of these MLs when low hysteresis is required. For the first AFM we may improve the sensitivity while retaining low hysteresis by increasing the cobalt thickness to 30-40 Å. At the second AFM we can reduce the magnetoresistive hysteresis by reducing the cobalt thickness to ˜ 3 Å. A particularly attractive combination of high sensitivity and low hysteresis is obtained at the second AFM by alternating such very thin Co layers with 15 Å thick Co layers.
Coexistence of negative photoconductivity and hysteresis in semiconducting graphene
NASA Astrophysics Data System (ADS)
Zhuang, Shendong; Chen, Yan; Xia, Yidong; Tang, Nujiang; Xu, Xiaoyong; Hu, Jingguo; Chen, Zhuo
2016-04-01
Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.
Preisach-type modeling of high-temperature superconducting hysteresis
NASA Astrophysics Data System (ADS)
ElBidweihy, Hatem
2016-05-01
Even though Isaak Mayergoyz described it as: "much more accurate for the description of superconducting hysteresis than for the description of hysteresis of magnetic materials", Preisach modeling of superconducting hysteresis is not a popular investigative tool. This might be due to the complexity of identifying the Preisach distribution function or due to lack of convincing physical reasoning behind pure phenomenological versions. In this paper, a two-component Preisach-type model is presented which is computationally-efficient and physically-sound. The change in the slope of the minor hysteresis loops is incorporated in the model and is attributed to reversible fluxoid motion. The model presented is clearly capable of simulating various shapes of superconducting hysteresis loops and could be easily coupled with finite element method (FEM) numerical software.
Dang, M T; Denisov, D; Struth, B; Zaccone, A; Schall, P
2016-04-01
The mechanical response of glasses remains challenging to understand. Recent results indicate that the oscillatory rheology of soft glasses is accompanied by a sharp non-equilibrium transition in the microscopic dynamics. Here, we use simultaneous x-ray scattering and rheology to investigate the reversibility and hysteresis of the sharp symmetry change from anisotropic solid to isotropic liquid dynamics observed in the oscillatory shear of colloidal glasses (D. Denisov, M.T. Dang, B. Struth, A. Zaccone, P. Schall, Sci. Rep. 5 14359 (2015)). We use strain sweeps with increasing and decreasing strain amplitude to show that, in analogy with equilibrium transitions, this sharp symmetry change is reversible and exhibits systematic frequency-dependent hysteresis. Using the non-affine response formalism of amorphous solids, we show that these hysteresis effects arise from frequency-dependent non-affine structural cage rearrangements at large strain. These results consolidate the first-order-like nature of the oscillatory shear transition and quantify related hysteresis effects both via measurements and theoretical modelling. PMID:27106107
NASA Astrophysics Data System (ADS)
Wang, Chongchong; Wang, Yukun; Hu, Lifa; Wang, Shaoxin; Cao, Zhaoliang; Mu, Quanquan; Li, Dayu; Yang, Chengliang; Xuan, Li
2016-05-01
The intrinsic hysteresis nonlinearity of the piezo-actuators can severely degrade the positioning accuracy of a tip-tilt mirror (TTM) in an adaptive optics system. This paper focuses on compensating this hysteresis nonlinearity by feed-forward linearization with an inverse hysteresis model. This inverse hysteresis model is based on the classical Presiach model, and the neural network (NN) is used to describe the hysteresis loop. In order to apply it in the real-time adaptive correction, an analytical nonlinear function derived from the NN is introduced to compute the inverse hysteresis model output instead of the time-consuming NN simulation process. Experimental results show that the proposed method effectively linearized the TTM behavior with the static hysteresis nonlinearity of TTM reducing from 15.6% to 1.4%. In addition, the tip-tilt tracking experiments using the integrator with and without hysteresis compensation are conducted. The wavefront tip-tilt aberration rejection ability of the TTM control system is significantly improved with the -3 dB error rejection bandwidth increasing from 46 to 62 Hz.
ST/HR hysteresis: exercise and recovery phase ST depression/heart rate analysis of the exercise ECG.
Lehtinen, R
1999-01-01
ST segment depression/heart rate (ST/HR) hysteresis is a recently introduced novel computer method for integrating the exercise and recovery phase ST/HR analysis for improved detection of coronary artery disease (CAD). It is a continuous diagnostic variable that extracts the prevailing direction and average magnitude of the hysteresis in ST depression against HR during the first 3 consecutive minutes of postexercise recovery. This article reviews the development and evaluation of this new method in a clinical population of 347 patients referred for a routine bicycle exercise electrocardiographic (ECG) test at Tampere University Hospital, Finland. Of these patients, 127 had angiographically proven CAD, whereas 13 had no CAD according to angiography, 18 had no perfusion defect according to Tc-99m-sestamibi myocardial imaging and single photon emission computed tomography, and 189 were clinically normal with respect to cardiac diseases. For each patient, the values for ST/HR hysteresis, ST/HR index, end-exercise ST depression, and recovery ST depression were determined for each lead of the Mason-Likar modification of the standard 12-lead exercise ECG and maximum value from the lead system (aVL, aVR, and V1 excluded). The area under the receiver operating characteristics curve (ie, the discriminative capacity) of the ST/HR hysteresis was 89%, which was significantly larger than that of the end-exercise ST depression (76%, P < .0001), recovery ST depression (84%, P = .0063) or ST/HR index (83%, P = .0023), indicating the best diagnostic performance of the ST/HR hysteresis in detection of CAD regardless of the partition value selection. Furthermore, the superior diagnostic performance of the method was relatively insensitive to the ST segment measurement point or to the ECG lead selection. These results suggest that the ST/HR hysteresis improves the clinical utility of the exercise ECG test in detection of CAD. PMID:10688326
ERIC Educational Resources Information Center
Swain, Gordon A.
2013-01-01
We show that inside every triangle the locus of points satisfying a natural proportionality relationship is a parabola and go on to describe how this triangle-parabola relationship was used by Archimedes to find the area between a line and a parabola.
ERIC Educational Resources Information Center
Yates, Robert C.
This volume, a reprinting of a classic first published in 1952, presents detailed discussions of 26 curves or families of curves, and 17 analytic systems of curves. For each curve the author provides a historical note, a sketch or sketches, a description of the curve, a discussion of pertinent facts, and a bibliography. Depending upon the curve,…
The field and temperature dependence of hysteresis loops in P(VDF-TrFE) copolymer films
NASA Astrophysics Data System (ADS)
Mai, Manfang; Leschhorn, Andreas; Kliem, Herbert
2015-01-01
The ferroelectric hysteresis loops of poly(vinylidene fluoride/trifluoethylene) [P(VDF-TrFE)] copolymer films are investigated as a function of external field and temperature. Starting from a plateau at the low frequency side the coercive field increases with increasing frequency. It exhibits a maximum in the kHz-range and decreases then. The remanent polarization is almost constant at low frequencies and decreases above the kHz-range. For a constant frequency, the coercive field increases with increasing the amplitude of the external field. Furthermore, the hysteresis loops at different temperatures at a given frequency and amplitude exhibit a linear decrease of coercive field with increasing temperature. A double hysteresis loop is observed close to the Curie point and a sharp jump of the remanent polarization is obtained in samples as thick as 600 nm indicating a first order phase transition. For samples as thin as 90 nm, the double hysteresis loop of the polarization is absent and the change of remanent polarization dependent on temperature is smoother. The above experimental results can be explained and simulated in the Weiss mean field model. The simulation results are compared with the experiments and show a good consistency.
NASA Astrophysics Data System (ADS)
Konar, G.; Chakraborty, N.; Das, J.
Hysteresis motors being capable of producing a steady torque at low speeds and providing good starting properties at loaded condition became popular among different fractional horse power electrical motors. High temperature superconducting materials being intrinsically hysteretic are suitable for this type of motor. In the present work, performance study of a 2-pole, 50 Hz HTS hysteresis motor with conventional stator and HTS rotor has been carried out numerically using finite element method. The simulation results confirm the ability of the segmented HTS rotor with glued circular sectors to trap the magnetic field as high as possible compared to the ferromagnetic rotor. Also the magnetization loops in the HTS hysteresis motor are obtained and the corresponding torque and AC losses are calculated. The motor torque thus obtained is linearly proportional to the current which is the common feature of any hysteresis motor. Calculations of torques, current densities etc are done using MATLAB program developed in-house and validated using COMSOL Multiphysics software. The simulation result shows reasonable agreement with the published results.
Hysteresis of Current in Noninteracting Atomic Fermi Gases in Optical Ring Potentials
NASA Astrophysics Data System (ADS)
Metcalf, Mekena; Chien, Chih-Chun; Lai, Chen-Yen
Hysteresis is a ubiquitous phenomenon, which can be found in magnets, superfluids, and other many-body systems. Although interactions are present in most systems exhibiting hysteresis, here we show the current of a non-interacting Fermi gas in an optical ring potential produces hysteresis behavior when driven by a time-dependent artificial gauge field and subject to dissipation. Fermions in a ring potential threaded with flux can exhibit a persistent current when the system is in thermal equilibrium, but cold-atoms are clean and dissipation for reaching thermal equilibrium may be introduced by an external, thermal bath. We use the standard relaxation approximation to model the dynamics of cold-atoms driven periodically by an artificial gauge field. A competition of the driven time and the relaxation time leads to hysteresis of the mass current, and work done on the system, as a function of the relaxation time, exhibits similar behavior as Kramers transition rate in chemical reaction and one-dimensional thermal transport.
NASA Astrophysics Data System (ADS)
Li, Linglong; Yang, Yaodong; Liu, Zhengchun; Jesse, Stephen; Kalinin, Sergei V.; Vasudevan, Rama K.
2016-04-01
The nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with hysteresis measurements with varying voltage windows on (K,Na)NbO3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the amplitude during hysteresis loop acquisition shows a clear decrease with increasing AC bias. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. This study suggests applicability at local length scales of fundamental principles of Rayleigh behavior, with associated implications for future nanoscale ferroic devices.
Towards the establishment of an archeointensity master curve for Mesoamerica
NASA Astrophysics Data System (ADS)
Morales, J.; Gogichaisvili, A.; Acosta, G.; Gonzales, T.
2007-05-01
We present new rock-magnetic and archaeointensity results of some pre-Columbian potteries found at archaeological caves in Chiapas, Southeast Mexico. The ceramics studied consist mostly of tiles of different archaeological artifacts. Their archeological ages cover mainly two ranges: from 550-250 BC and from 100-500 AD. `Rock-magnetic' experiments which included susceptibility vs. temperature and hysteresis measurements were used to select magnetically stable and suitable material for Thellier absolute intensity determinations. Six out of thirteen archaeological tiles, which showed no evidence of strong secondary components and presenting almost reversible susceptibility curves, were selected for archeointensity studies. Each of these tiles were further divided into at least seven fragments and then set in salt (NaCl) pellets in order to treat them as standard paleomagnetic cores. Magnetization per unit volume of `blank' pellets is negligible with respect to that of ceramic samples. Archeointensity experiments were carried out using the Coe version of the Thellier method. Cooling rate and anisotropy effects were investigated on each sample. Thellier experiments yielded unusually high success rate and data obtained are of excellent technical quality, attested by reasonably high Coe's factors. This pioneering study proves the usefulness of Mesoamerican ceramics for archeointensity studies and opens new perspectives towards the establishment of a reference intensity variation curve for the region.
Hysteresis and precession of a swirling jet normal to a wall.
Shtern, V; Mi, J
2004-01-01
Interaction of a swirling jet with a no-slip surface has striking features of fundamental and practical interest. Different flow states and transitions among them occur at the same conditions in combustors, vortex tubes, and tornadoes. The jet axis can undergo precession and bending in combustors; this precession enhances large-scale mixing and reduces emissions of NOx. To explore the mechanisms of these phenomena, we address conically similar swirling jets normal to a wall. In addition to the Serrin model of tornadolike flows, a new model is developed where the flow is singularity free on the axis. New analytical and numerical solutions of the Navier-Stokes equations explain occurrence of multiple states and show that hysteresis is a common feature of wall-normal vortices or swirling jets no matter where sources of motion are located. Then we study the jet stability with the aid of a new approach accounting for deceleration and nonparallelism of the base flow. An appropriate transformation of variables reduces the stability problem for this strongly nonparallel flow to a set of ordinary differential equations. A particular flow whose stability is studied in detail is a half-line vortex normal to a rigid plane-a model of a tornado and of a swirling jet issuing from a nozzle in a combustor. Helical counter-rotating disturbances appear to be first growing as Reynolds number increases. Disturbance frequency changes its sign along the neutral curve while the wave number remains positive. Short disturbance waves propagate downstream and long waves propagate upstream. This helical instability causes bending of the vortex axis and its precession-the effects observed in technological flows and in tornadoes. PMID:14995717