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Sample records for p-e hysteresis loop

  1. Analysis of wasp-waisted hysteresis loops in magnetic rocks.

    PubMed

    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

  2. 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.

  3. Simulation of polarization and butterfly hysteresis loops in bismuth layer-structured ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Ye, Z.; Tang, M. H.; Cheng, C. P.; Zhou, Y. C.; Zheng, X. J.; Hu, Z. S.

    2006-11-01

    Modeling of the hysteresis loop of ferroelectric thin films has been thought very difficult owing to its nonlinear and history-dependent electric field effects. Here we extend the Preisach model [Z. Phys. 94, 277 (1935)] by using the distribution function integral and superposition method. The model shows improved hysteresis loop that agrees reasonably well with the experimental data measured from the bismuth layer-structured ferroelectric thin films. Compared with the previous model, the current model provides polarization-field (P-E) loop with full and symmetric shape, suitable coercive field (Ec), and few undesirable parameters. The butterfly loop of perovskite-type ferroelectric thin films is also simulated. Additionally, the approach is able to describe the unsaturated loops obtained under various ac electric fields, which is very useful in circuit simulation of ferroelectric field effect transistor or ferroelectric capacitor.

  4. Influence of interfacial dislocations on hysteresis loops of ferroelectric films

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Hu, S. Y.; Choudhury, S.; Baskes, M. I.; Saxena, A.; Lookman, T.; Jia, Q. X.; Schlom, D. G.; Chen, L. Q.

    2008-11-01

    We investigated the influence of dislocations, located at the interface of a ferroelectric film and its underlying substrate, on the ferroelectric hysteresis loop including the remanent polarization and coercive field using phase-field simulations. We considered epitaxial ferroelectric BaTiO3 films and found that the hysteresis loop is strongly dependent on the type and density of interfacial dislocations. The dislocations that stabilize multiple ferroelectric variants and domains reduce the coercive field, and consequently, the corresponding remanent polarization also decreases.

  5. Understanding the Hysteresis Loop Conundrum in Pharmacokinetic / Pharmacodynamic Relationships

    PubMed Central

    Louizos, Christopher; Yáñez, Jaime A.; Forrest, Laird; Davies, Neal M.

    2015-01-01

    Hysteresis loops are phenomena that sometimes are encountered in the analysis of pharmacokinetic and pharmacodynamic relationships spanning from pre-clinical to clinical studies. When hysteresis occurs it provides insight into the complexity of drug action and disposition that can be encountered. Hysteresis loops suggest that the relationship between drug concentration and the effect being measured is not a simple direct relationship, but may have an inherent time delay and disequilibrium, which may be the result of metabolites, the consequence of changes in pharmacodynamics or the use of a non-specific assay or may involve an indirect relationship. Counter-clockwise hysteresis has been generally defined as the process in which effect can increase with time for a given drug concentration, while in the case of clockwise hysteresis the measured effect decreases with time for a given drug concentration. Hysteresis loops can occur as a consequence of a number of different pharmacokinetic and pharmacodynamic mechanisms including tolerance, distributional delay, feedback regulation, input and output rate changes, agonistic or antagonistic active metabolites, uptake into active site, slow receptor kinetics, delayed or modified activity, time-dependent protein binding and the use of racemic drugs among other factors. In this review, each of these various causes of hysteresis loops are discussed, with incorporation of relevant examples of drugs demonstrating these relationships for illustrative purposes. Furthermore, the effect that pharmaceutical formulation has on the occurrence and potential change in direction of the hysteresis loop, and the major pharmacokinetic / pharmacodynamic modeling approaches utilized to collapse and model hysteresis are detailed. PMID:24735761

  6. Completely inverted hysteresis loops: Inhomogeneity effects or experimental artifacts

    SciTech Connect

    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.

  7. 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.

  8. Loading-unloading hysteresis loop of randomly rough adhesive contacts.

    PubMed

    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

  9. Evaluation of minor hysteresis loops using Langevin transforms in modified inverse Jiles-Atherton model

    NASA Astrophysics Data System (ADS)

    Hamimid, M.; Mimoune, S. M.; Feliachi, M.

    2013-11-01

    In this paper, we present a Langevin transforms model which evaluates accurately minor hysteresis loops for the modified inverse Jiles-Atherton model by using appropriate expressions in order to improve minor hysteresis loops characteristics. The parameters of minor hysteresis loops are then related to the parameters of the major hysteresis loop according to each level of maximal induction by using Langevin transforms expressions. The stochastic optimization method “simulated annealing” is used for the determination of the Langevin transforms coefficients. This model needs only two experimental tests to generate all hysteresis loops. The validity of the Langevin transforms model is justified by comparison of calculated minor hysteresis loops to measured ones and good agreements are obtained with better results than the exponential transforms model (Hamimid et al., 2011 [4]).

  10. Modeling of hysteresis loops by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Nehme, Z.; Labaye, Y.; Sayed Hassan, R.; Yaacoub, N.; Greneche, J. M.

    2015-12-01

    Recent advances in MC simulations of magnetic properties are rather devoted to non-interacting systems or ultrafast phenomena, while the modeling of quasi-static hysteresis loops of an assembly of spins with strong internal exchange interactions remains limited to specific cases. In the case of any assembly of magnetic moments, we propose MC simulations on the basis of a three dimensional classical Heisenberg model applied to an isolated magnetic slab involving first nearest neighbors exchange interactions and uniaxial anisotropy. Three different algorithms were successively implemented in order to simulate hysteresis loops: the classical free algorithm, the cone algorithm and a mixed one consisting of adding some global rotations. We focus particularly our study on the impact of varying the anisotropic constant parameter on the coercive field for different temperatures and algorithms. A study of the angular acceptation move distribution allows the dynamics of our simulations to be characterized. The results reveal that the coercive field is linearly related to the anisotropy providing that the algorithm and the numeric conditions are carefully chosen. In a general tendency, it is found that the efficiency of the simulation can be greatly enhanced by using the mixed algorithm that mimic the physics of collective behavior. Consequently, this study lead as to better quantified coercive fields measurements resulting from physical phenomena of complex magnetic (nano)architectures with different anisotropy contributions.

  11. Role of measurement voltage on hysteresis loop shape in Piezoresponse Force Microscopy

    SciTech Connect

    Kim, Yunseok; Yang, J.-C.; Chu, Ying Hao; Yu, Pu; Lu, X.; Jesse, Stephen; Kalinin, Sergei V

    2012-01-01

    The dependence of on-field and off-field hysteresis loop shape in Piezoresponse Force Microscopy (PFM) on driving voltage, Vac, is explored. A nontrivial dependence of hysteresis loop parameters on measurement conditions is observed. The strategies to distinguish between paraelectric and ferroelectric states with small coercive bias and separate reversible hysteretic and non-hysteretic behaviors are suggested. Generally, measurement of loop evolution with Vac is a necessary step to establish the veracity of PFM hysteresis measurements.

  12. Minor hysteresis loops model based on exponential parameters scaling of the modified Jiles-Atherton model

    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.

  13. Cumulative growth of minor hysteresis loops in the Kolmogorov model

    SciTech Connect

    Meilikhov, E. Z. Farzetdinova, R. M.

    2013-01-15

    The phenomenon of nonrepeatability of successive remagnetization cycles in Co/M (M = Pt, Pd, Au) multilayer film structures is explained in the framework of the Kolmogorov crystallization model. It is shown that this model of phase transitions can be adapted so as to adequately describe the process of magnetic relaxation in the indicated systems with 'memory.' For this purpose, it is necessary to introduce some additional elements into the model, in particular, (i) to take into account the fact that every cycle starts from a state 'inherited' from the preceding cycle and (ii) to assume that the rate of growth of a new magnetic phase depends on the cycle number. This modified model provides a quite satisfactory qualitative and quantitative description of all features of successive magnetic relaxation cycles in the system under consideration, including the surprising phenomenon of cumulative growth of minor hysteresis loops.

  14. Magnetic biasing of a ferroelectric hysteresis loop in a multiferroic orthoferrite.

    PubMed

    Tokunaga, Y; Taguchi, Y; Arima, T; Tokura, Y

    2014-01-24

    In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign. PMID:24484164

  15. Comprehensive modelling of dynamic hysteresis loops in the rolling and transverse directions for transformer laminations

    NASA Astrophysics Data System (ADS)

    Baghel, A. P. S.; Gupta, A.; Chwastek, K.; Kulkarni, S. V.

    2015-04-01

    Magnetic properties of grain-oriented materials are affected by hysteresis, anisotropy and dynamic effects. The attempts to describe dynamic hysteresis loops are usually limited to the rolling direction (RD). On the other hand, modelling of magnetic properties for the transverse direction (TD) is important for numerical analysis of core-joints and corner regions in transformers. For this direction, hysteresis loops reveal complex shapes particularly for dynamic magnetization conditions. This paper presents a comprehensive approach for modelling of dynamic hysteresis loops in RD and TD. This work uses the magnetic viscosity-based approach, which is able to describe irregular widening of dynamic loops. The loss separation scheme is also considered for both principal directions. Variations of loss components with frequency for both directions are discussed. The computed dynamic loops in RD and TD are in a close agreement with experimental ones.

  16. Research on the dynamic hysteresis loop model of the residence times difference (RTD)-fluxgate.

    PubMed

    Wang, Yanzhang; Wu, Shujun; Zhou, Zhijian; Cheng, Defu; Pang, Na; Wan, Yunxia

    2013-01-01

    Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model. PMID:24002230

  17. Research on the Dynamic Hysteresis Loop Model of the Residence Times Difference (RTD)-Fluxgate

    PubMed Central

    Wang, Yanzhang; Wu, Shujun; Zhou, Zhijian; Cheng, Defu; Pang, Na; Wan, Yunxia

    2013-01-01

    Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model. PMID:24002230

  18. 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.

  19. Effects of grain size, hardness, and stress on the magnetic hysteresis loops of ferromagnetic steels

    NASA Astrophysics Data System (ADS)

    Kwun, H.; Burkhardt, G. L.

    1987-02-01

    Effects of grain size, hardness, and stress on the magnetic hysteresis loops of AISI 410 stainless steel and SAE 4340 steel specimens were investigated experimentally. It was observed that both hardness and stress significantly influenced the hysteresis loops, while the grain size had a minimal effect. For each material, the mechanically harder specimen was more difficult to magnetize. Upon application of uniaxial stress, the magnetic induction increased under tension and decreased under compression, with the sides of the hysteresis loops becoming inclined more toward the vertical axis under tension and the horizontal axis under compression. For each material, the effects of stress on the hysteresis loops were greater for the mechanically softer specimen and exhibited an inverse relationship to the hardness. The effects of stress were not dependent on grain size.

  20. Modelling offset minor hysteresis loops with the modified Jiles-Atherton description

    NASA Astrophysics Data System (ADS)

    Chwastek, K.

    2009-08-01

    The paper addresses the issue of modelling offset minor hysteresis loops within the framework of the Jiles-Atherton model. Two of the model parameters are expressed in terms of scaling power laws with respect to the magnetization level. The approach is consistent with earlier theoretical considerations on the effective 'volume fraction' by Professor D Jiles. The influence of eddy currents on hysteresis loop is taken into account using an additional term of magnetic field.

  1. Ac hysteresis loop measurement of stator-tooth in induction motor

    SciTech Connect

    Son, D.

    1999-09-01

    The properties of ac hysteresis loop of a stator tooth in a 5 hp induction motor was measured and analyzed. The load increase on the motor decreased magnetic induction, however increase the minor hysteresis loops in the high induction region. This effect caused increase in the core loss. Depending on condition of the motor, the core loss of the stator tooth can be 50% greater than the core loss under sinusoidal magnetic induction waveform.

  2. 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.

  3. Study of the fast photoswitching of spin crossover nanoparticles outside and inside their thermal hysteresis loop

    SciTech Connect

    Galle, G.; Degert, J.; Freysz, E.; Etrillard, C.; Letard, J.-F.; Guillaume, F.

    2013-02-11

    We have studied the low spin to high spin phase transition induced by nanosecond laser pulses outside and within the thermal hysteresis loop of the [Fe(Htrz){sub 2} trz](BF{sub 4}){sub 2}-H{sub 2}O spin crossover nanoparticles. We demonstrate that, whatever the temperature of the compound, the photo-switching is achieved in less than 12.5 ns. Outside the hysteresis loop, the photo-induced high spin state remains up to 100 {mu}s and then relaxes. Within the thermal hysteresis loop, the photo-induced high spin state remains as long as the temperature of the sample is kept within the thermal loop. A Raman study indicates that the photo-switching can be completed using single laser pulse excitation.

  4. Intrinsic Hysteresis Loops Calculation of BZT Thin Films

    NASA Astrophysics Data System (ADS)

    Hikam, M.; Adnan, S. R.

    2014-04-01

    The Landau Devonshire (LK) simulation is utilized to calculate the intrinsic hysteresis properties of Barium Zirconium Titanate (BZT) doped by Indium and Lanthanum. A Delphi program run on Windows platform is used to facilitate the calculation. The simulation is very useful to calculate and understand the Gibbs free energy and the relationship between spontaneous polarization and electric field.

  5. Non centered minor hysteresis loops evaluation based on exponential parameters transforms of the modified inverse Jiles-Atherton model

    NASA Astrophysics Data System (ADS)

    Hamimid, M.; Mimoune, S. M.; Feliachi, M.; Atallah, K.

    2014-10-01

    In this present work, a non centered minor hysteresis loops evaluation is performed using the exponential transforms (ET) of the modified inverse Jiles-Atherton model parameters. This model improves the non centered minor hysteresis loops representation. The parameters of the non centered minor hysteresis loops are obtained from exponential expressions related to the major ones. The parameters of minor loops are obtained by identification using the stochastic optimization method “simulated annealing”. The four parameters of JA model (a,α, k and c) obtained by this transformation are applied only in both ascending and descending branches of the non centered minor hysteresis loops while the major ones are applied to the rest of the cycle. This proposal greatly improves both branches and consequently the minor loops. To validate this model, calculated non-centered minor hysteresis loops are compared with measured ones and good agreements are obtained.

  6. Scaling Behavior of Barkhausen Avalanches along the Hysteresis loop in Nucleation-Mediated Magnetization Reversal Process

    SciTech Connect

    Im, Mi-Young; Fischer, Peter; Kim, D.-H.; Shin, S.-C.

    2008-10-14

    We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.

  7. Efficient hysteresis loop simulations of nanoparticle assemblies beyond the uniaxial anisotropy

    NASA Astrophysics Data System (ADS)

    Tamion, Alexandre; Bonet, Edgar; Tournus, Florent; Raufast, Cécile; Hillion, Arnaud; Gaier, Oksana; Dupuis, Véronique

    2012-04-01

    We propose a modified Stoner-Wohlfarth model combined with the geometrical approach of the coherent rotation of magnetization for simulating the hysteresis loops of an assembly of magnetic nanoparticles. The temperature and the size distribution are taken into account. This combined model enables the computation of hysteresis loops at low temperatures for assemblies of particles having an arbitrary type of anisotropy. The applicability of this model for fitting experimental data is discussed and results are compared to the zero-field-cooled and field-cooled fits. As an application, the hysteresis loops measured on Co clusters embedded in carbon and germanium matrices are fitted revealing unambiguously the presence of a biaxial anisotropy.

  8. Hysteresis loop behaviors of ferroelectric thin films: A Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    M. Bedoya-Hincapié, C.; H. Ortiz-Álvarez, H.; Restrepo-Parra, E.; J. Olaya-Flórez, J.; E. Alfonso, J.

    2015-11-01

    The ferroelectric response of bismuth titanate Bi4Ti3O12 (BIT) thin film is studied through a Monte Carlo simulation of hysteresis loops. The ferroelectric system is described by using a Diffour Hamiltonian with three terms: the electric field applied in the z direction, the nearest dipole-dipole interaction in the transversal (x-y) direction, and the nearest dipole-dipole interaction in the direction perpendicular to the thin film (the z axis). In the sample construction, we take into consideration the dipole orientations of the monoclinic and orthorhombic structures that can appear in BIT at low temperature in the ferroelectric state. The effects of temperature, stress, and the concentration of pinned dipole defects are assessed by using the hysteresis loops. The results indicate the changes in the hysteresis area with temperature and stress, and the asymmetric hysteresis loops exhibit evidence of the imprint failure mechanism with the emergence of pinned dipolar defects. The simulated shift in the hysteresis loops conforms to the experimental ferroelectric response. Project sponsored by the research departments of the Universidad Nacional de Colombia DIMA and DIB under Project 201010018227-“Crecimiento y caracterización eléctrica y estructural de películas delgadas de BixTiyOz producidas mediante Magnetrón Sputtering” and Project 12920-“Desarrollo teóricoexperimental de nanoestructuras basadas en Bismuto y materiales similares” and “Bisnano Project.”

  9. Magnetic field-controlled hysteresis loop bias in orthogonal exchange-spring coupling composite magnetic films

    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.

  10. Simulation of magnetic hysteresis loops and magnetic Barkhausen noise of α-iron containing nonmagnetic particles

    SciTech Connect

    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.

  11. Investigation of the Temperature Hysteresis Phenomenon of a Loop Heat Pipe

    NASA Technical Reports Server (NTRS)

    Kaya, Tarik; Ku, Jentung; Hoang, Triem; Cheung, Mark K.

    1999-01-01

    The temperature hysteresis phenomenon of a Loop Heat Pipe (LHP) was experimentally investigated. The temperature hysteresis was identified by the fact that the operating temperature depends upon not only the imposed power but also the previous history of the power variation. The temperature hysteresis could impose limitations on the LHP applications since the LHP may exhibit different steady-state operating temperatures at a given power input even when the condenser sink temperature remains unchanged. In order to obtain insight to this phenomenon, a LHP was tested at different elevations and tilts by using an elaborated power profile. A hypothesis was suggested to explain the temperature hysteresis. This hypothesis explains well the experimental observations. Results of this study provide a better understanding of the performance characteristics of the LHPS.

  12. 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.

  13. 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.

  14. Nonhysteretic behavior inside the hysteresis loop of VO2 and its possible application in infrared imaging

    NASA Astrophysics Data System (ADS)

    Gurvitch, M.; Luryi, S.; Polyakov, A.; Shabalov, A.

    2009-11-01

    In the resistive phase transition in VO2, temperature excursions taken from points on the major hysteresis loop produce minor loops. For sufficiently small excursions these minor loops degenerate into single-valued, nonhysteretic branches (NHBs) linear in log(ρ) versus T and having essentially the same or even higher temperature coefficient of resistance (TCR) as the semiconducting phase at room temperature. We explain this behavior based on the microscopic picture of percolating phases. Similar short NHBs are found in otherwise hysteretic optical reflectivity. We discuss the opportunities NHBs present for infrared imaging technology based on resistive microbolometers. It is possible to choose a NHB with 102-103 times smaller resistivity than in a pure semiconducting phase, thus providing a microbolometer operating without hysteresis, with low tunable resistivity, and high TCR. Unique features of the proposed method and projected figures of merit are discussed in the context of uncooled focal plane array IR visualization technology.

  15. Simulations of magnetic hysteresis loops at high temperatures

    SciTech Connect

    Plumer, M. L.; Whitehead, J. P.; Fal, T. J.; Ek, J. van; Mercer, J. I.

    2014-09-28

    The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Our results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures.

  16. Estimate Interface Shear Stress of Woven Ceramic Matrix Composites from Hysteresis Loops

    NASA Astrophysics Data System (ADS)

    Li, Longbiao; Song, Yingdong

    2013-12-01

    An approach to estimate the fiber/matrix interface shear stress of woven ceramic matrix composites during fatigue loading has been developed in this paper. Based on the analysis of the microstructure, the woven ceramic matrix composites were divided into four elements of 0o warp yarns, 90o weft yarns, matrix outside of the yarns and the open porosity. When matrix cracking and fiber/matrix interface debonding occur upon first loading to the peak stress, it is assumed that fiber slipping relative to matrix in the interface debonded region of the 0o warp yarns is the mainly reason for the occurrence of the hysteresis loops of woven ceramic matrix composiets during unloading and subsequent reloading. The unloading interface reverse slip length and reloading interface new slip length are determined by the interface slip mechanisms. The hysteresis loops of three different cases have been derived. The hysteresis loss energy for the strain energy lost per volume during corresponding cycle is formulated in terms of the fiber/matrix interface shear stress. By comparing the experimental hysteresis loss energy with the computational values, the fiber/matrix interface shear stress of woven ceramic matrix composites corresponding to different cycles can then be derived. The theoretical results have been compared with experimental data of two different woven ceramic composites.

  17. Damping measurements of laminated composite materials and aluminum using the hysteresis loop method

    NASA Astrophysics Data System (ADS)

    Abramovich, H.; Govich, D.; Grunwald, A.

    2015-10-01

    The damping characteristics of composite laminates made of Hexply 8552 AGP 280-5H (fabric), used for structural elements in aeronautical vehicles, have been investigated in depth using the hysteresis loop method and compared to the results for aluminum specimens (2024 T351). It was found that the loss factor, η, obtained by the hysteresis loop method is linearly dependent only on the applied excitation frequency and is independent of the preloading and the stress amplitudes. For the test specimens used in the present tests series, it was found that the damping of the aluminum specimens is higher than the composite ones for longitudinal direction damping, while for bending vibrations the laminates exhibited higher damping values.

  18. Multifractal analysis of Barkhausen noise reveals the dynamic nature of criticality at hysteresis loop

    NASA Astrophysics Data System (ADS)

    Tadić, Bosiljka

    2016-06-01

    The field-driven magnetisation reversal processes in disordered systems exhibit a collective behaviour that is manifested in the scale-invariance of avalanches, closely related to underlying dynamical mechanisms. Using the multifractal time series analysis, we study the structure of fluctuations at different scales in the accompanying Barkhausen noise. The stochastic signal represents the magnetisation discontinuities along the hysteresis loop of a three-dimensional random field Ising model simulated for varied disorder strength and driving rates. The analysis of the spectrum of the generalised Hurst exponents reveals that the dominant segments of the signal with large fluctuations represent two distinct classes of stochastic processes in weak and strong pinning regimes. Furthermore, in the weak pinning regime, the part of the signal originating from the beginning of the hysteresis loop has a different multifractal spectrum than the signal near the coercive field. The enhanced fluctuations (primarily in the central part of the hysteresis loop) for increased driving rate and larger system size, lead to a further broadening of the spectrum. The analysed Barkhausen signals are also shown to exhibit temporal correlations and power-law distributions of the magnetisation discontinuity and avalanche sizes, in agreement with previous studies. The multifractal properties of Barkhausen noise describe the dynamical state of domains and precisely discriminate the weak pinning, permitting the motion of individual walls, from the mechanisms occurring in strongly disordered systems.

  19. Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy

    PubMed Central

    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

  20. Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy.

    PubMed

    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

  1. Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy

    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.

  2. ac Dynamics of Ferroelectric Domains from an Investigation of the Frequency Dependence of Hysteresis Loops

    SciTech Connect

    Yang, Sang Mo; Jo, Ji Young; Kim, T. H.; Yoon, J. -G.; Song, T. K.; Lee, Ho Nyung; Marton, Zsolt; Park, S.; Jo, Y.; Noh, Tae Won

    2010-01-01

    We investigated nonequilibrium domain wall dynamics under an ac field by measuring the hystere- sis loops of epitaxial ferroelectric capacitors at various frequencies and temperatures. Polarization switching is induced mostly by thermally activated creep motion at lower frequencies, and by vis- cous ow motion at higher frequencies. The dynamic crossover between the creep and ow regimes unveils two frequency-dependent scaling regions of hysteresis loops. Based on these findings, we constructed a dynamic phase diagram for hysteretic ferroelectric domain dynamics in the presence of ac fields.

  3. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-08-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  4. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-02-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  5. Crystal Orientation and Temperature Effects on the Double Hysteresis Loop Behavior of a PVDF- g-PS Graft Copolymer

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Yang, Lianyun; Guan, Fangxiao

    2013-03-01

    In a recent report, double hysteresis loop behavior is observed in a nanoconfined poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graft-polystyrene [P(VDF-TrFE-CTFE)- g-PS] copolymer. It is considered that the PS grafts are capable of reducing the compensation polarization and thus the polarization electric field during the reverse poling process, resulting in the double hysteresis loop behavior. In this study, we further investigated crystal orientation and temperature effects on this novel ferroelectric behavior. It is observed that with increasing the orientation factor, the electric displacement-electric field (D-E) loop changes from linear for non-oriented film to double loop for the well-oriented film. With increasing the temperature, the double hysteresis loop is gradually replaced by the single and open loop, which is attributed to the impurity ion migrational loss in the sample. This work is supported by NSF (DMR-0907580).

  6. 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.

  7. Unmixing hysteresis loops of the late Miocene–early Pleistocene loess-red clay sequence

    PubMed Central

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-01-01

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals. PMID:27389499

  8. Unmixing hysteresis loops of the late Miocene-early Pleistocene loess-red clay sequence.

    PubMed

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-01-01

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals. PMID:27389499

  9. Unmixing hysteresis loops of the late Miocene–early Pleistocene loess-red clay sequence

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-07-01

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals.

  10. Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Ehrmann, Andrea; Blachowicz, Tomasz

    2014-08-01

    The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.

  11. Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures

    SciTech Connect

    Ehrmann, Andrea; Blachowicz, Tomasz

    2014-08-15

    The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.

  12. Acquisition of vector hysteresis loops from micro-arrays of nano-magnets

    NASA Astrophysics Data System (ADS)

    Keatley, P. S.; Kruglyak, V. V.; Hicken, R. J.; Childress, J. R.; Katine, J. A.

    2006-11-01

    A modified scanning Kerr microscope has been used as a static Kerr magnetometer to acquire in-plane vector hysteresis loops from square Si/Ta(50 Å)/Co 80Fe 20(40 Å)/Ni 88Fe 12(108 Å)/Ta(100 Å) elements with size ranging from 123 nm to 10 μm. The nanoscale elements were arranged in square arrays of 4 μm size. The laser beam was focused to a sub-micron spot, while polarization changes were recorded with an optical bridge detector containing a beam-splitting polarizer and two quadrant photodiodes. The coercive field exhibited a non-monotonic increase from 11 Oe in the 10 μm element to 170 Oe in the 123 nm elements. Loops acquired with the field applied parallel to the easy and hard in-plane uniaxial anisotropy axes were observed to become more similar in shape as the element size decreased.

  13. Double hysteresis loops and large negative and positive electrocaloric effects in tetragonal ferroelectrics.

    PubMed

    Wu, Hong-Hui; Zhu, Jiaming; Zhang, Tong-Yi

    2015-10-01

    Phase field modelling and thermodynamic analysis are employed to investigate depolarization and compression induced large negative and positive electrocaloric effects (ECEs) in ferroelectric tetragonal crystalline nanoparticles. The results show that double-hysteresis loops of polarization versus electric field dominate at temperatures below the Curie temperature of the ferroelectric material, when the mechanical compression exceeds a critical value. In addition to the mechanism of pseudo-first-order phase transition (PFOPT), the double-hysteresis loops are also caused by the abrupt rise of macroscopic polarization from the abc phase to the c phase or the sudden fall of macroscopic polarization from the c phase to the abc phase when the temperature increases. This phenomenon is called the electric-field-induced-pseudo-phase transition (EFIPPT) in the present study. Similar to the two types of PFOPTs, the two types of EFIPPTs cause large negative and positive ECEs, respectively, and give the maximum absolute values of negative and positive adiabatic temperature change (ATC ΔT). The temperature associated with the maximum absolute value of negative ATC ΔT is lower than that associated with the maximum positive ATC ΔT. Both maximum absolute values of ATC ΔTs change with the variation in the magnitude of an applied electric field and depend greatly on the compression intensity. PMID:26307461

  14. Specific features of magnetic properties of ferrihydrite nanoparticles of bacterial origin: A shift of the hysteresis loop

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Krasikov, A. A.; Dubrovskiy, A. A.; Semenov, S. V.; Popkov, S. I.; Stolyar, S. V.; Iskhakov, R. S.; Ladygina, V. P.; Yaroslavtsev, R. N.

    2016-02-01

    The results of the experimental investigation into the magnetic hysteresis of systems of superparamagnetic ferrihydrite nanoparticles of bacterial origin have been presented. The hysteresis properties of these objects are determined by the presence of an uncompensated magnetic moment in antiferromagnetic nanoparticles. It has been revealed that, under the conditions of cooling in an external magnetic field, there is a shift of the hysteresis loop with respect to the origin of the coordinates. These features are associated with the exchange coupling of the uncompensated magnetic moment and the antiferromagnetic "core" of the particles, as well as with processes similar to those responsible for the behavior of minor hysteresis loops due to strong local anisotropy fields of the ferrihydrite nanoparticles.

  15. Numerical micromagnetic modeling of shifted hysteresis loops in two-phase grains.

    NASA Astrophysics Data System (ADS)

    Shcherbakov, V. P.; Sycheva, N. K.

    2003-04-01

    The shifted hysteresis loops (SHL) are usually referred to the exchange anisotropy resulting from superexchange interaction across the interface of a two-phase ferrimagnetic (FM) - antiferrimagnetic (AF) system like maghemite-hematite or ordered-disordered hemoilmenite intergrowths. The three-dimensional numerical micromagnetic modeling including the self-magnetostatic energy of the FM-AFM system is carried out. For this the rectangular grain was subdivided into 63x31x31 cells; in so doing the FM phase occupied the (N)x31x31 cells while the neighbouring AFM phase took the rest (63-N)x31x31 cells. The equilibrium state was obtained by the minimization of the total energy. The solution is specified mainly by the parameters N, K/Ms and relations of the domain wall (DW) width to the sizes L of the FM phase and M of the AFM phase. Here Ms is the spontaneous magnetization, K is the magnetocrystalline constant. Calculations performed under different given parameters of the grain had shown that, in accordance with the predictions of the analytical approach, in large enough grains, when the DW width < L and L < M, the process of re-magnetization proceeds by yielding the DW on the interface boundary and the SHL are indeed observed in such the grains. The magnitude of the shift Hsh of the hysteresis loop can be estimated as the DW energy/LMs = (0.01-0.1)T. If both AF and FM phases are of order (or thinner) than the corresponding DW widths, neither DW nor shifted loops do appear. The work is supported by INTAS grant 99-1273.

  16. Analysis of Magnetic Minor Hysteresis Loops in Thermally Aged and Cold-rolled Fe-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Takahashi, F.; Kobayashi, S.; Murakami, T.; Takahashi, S.; Kamada, Y.; Kikuchi, H.

    2011-01-01

    Neutron irradiation causes the formation of Cu precipitate in reactor pressure vessel steel and makes the steel susceptible to rupture. In the present study, we have examined magnetic minor hysteresis loops of Fe-1wt%Cu alloy after thermally ageing at 753 K and subsequent cold rolling to elucidate the effects of Cu precipitation on magnetic properties. Minor-loop coefficients, obtained from scaling power laws between field-dependent parameters of minor hysteresis loops, decrease with ageing time and show a local maximum around 200 min, reflecting the growth of Cu precipitates with ageing. For the alloy cold-rolled after ageing, the minor-loop properties linearly increase with reduction and show a good relationship with mechanical properties such as DBTT and hardness. These observations indicate that the analysis method using magnetic minor loops can be an useful technique of nondestructive evaluation of irradiation embrittlement and subsequent deformation hardening in reactor pressure vessel steels.

  17. Hysteresis loop of a cubic nanowire in the presence of the crystal field and the transverse field

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Li, Xiao-Xi; Liu, Li-Mei; Chen, Jun-Nan; Zhang, Fan

    2014-03-01

    The effective-field theory with correlations (EFT) has been used to study the various shapes of the hysteresis loop for a ferromagnetic core of spin-1 and a ferromagnetic shell of spin-3/2 with ferrimagnetic interface coupling on a cubic nanowire. The magnetizations and phase diagrams of the nanowire have been investigated in the previous work (J. Magn. Magn. Mater. 324 (2012) 4034-4042). A number of characteristic behaviors are obtained especially for the triple and multiple hysteresis loop patterns for certain values of the system parameters at low temperature. We also examine the effect of the system parameters on coercivity of the nanowire.

  18. Simulation of magnetic hysteresis loops and magnetic Barkhausen noise of α-iron containing nonmagnetic particles

    SciTech Connect

    Li, Yi; Xu, Ben; Hu, Shenyang; Li, Yulan; Li, Qiulin; Liu, Wei

    2015-07-01

    The magnetic hysteresis loops and Barkhausen noise of a single α-iron with nonmagnetic particles are simulated to investigate into the magnetic hardening due to Cu-rich precipitates in irradiated reactor pressure vessel (RPV) steels. Phase field method basing Landau-Lifshitz-Gilbert (LLG) equation is used for this simulation. The results show that the presence of the nonmagnetic particle could result in magnetic hardening by making the nucleation of reversed domains difficult. The coercive field is found to increase, while the intensity of Barkhausen noise voltage is decreased when the nonmagnetic particle is introduced. Simulations demonstrate the impact of nucleation field of reversed domains on the magnetization reversal behavior and the magnetic properties.

  19. Simulation of magnetic hysteresis loops and magnetic Barkhausen noise of α-iron containing nonmagnetic particles

    DOE PAGESBeta

    Li, Yi; Xu, Ben; Hu, Shenyang; Li, Yulan; Li, Qiulin; Liu, Wei

    2015-07-01

    The magnetic hysteresis loops and Barkhausen noise of a single α-iron with nonmagnetic particles are simulated to investigate into the magnetic hardening due to Cu-rich precipitates in irradiated reactor pressure vessel (RPV) steels. Phase field method basing Landau-Lifshitz-Gilbert (LLG) equation is used for this simulation. The results show that the presence of the nonmagnetic particle could result in magnetic hardening by making the nucleation of reversed domains difficult. The coercive field is found to increase, while the intensity of Barkhausen noise voltage is decreased when the nonmagnetic particle is introduced. Simulations demonstrate the impact of nucleation field of reversed domainsmore » on the magnetization reversal behavior and the magnetic properties.« less

  20. Simulation of magnetic hysteresis loops and magnetic Barkhausen noise of α-iron containing nonmagnetic particles

    SciTech Connect

    Li, Yi; Li, Qiulin; Liu, Wei; Xu, Ben; Hu, Shenyang; Li, Yulan

    2015-07-15

    The magnetic hysteresis loops and Barkhausen noise of a single α-iron with nonmagnetic particles are simulated to investigate into the magnetic hardening due to Cu-rich precipitates in irradiated reactor pressure vessel (RPV) steels. Phase field method basing Landau-Lifshitz-Gilbert (LLG) equation is used for this simulation. The results show that the presence of the nonmagnetic particle could result in magnetic hardening by making the nucleation of reversed domains difficult. The coercive field is found to increase, while the intensity of Barkhausen noise voltage is decreased when the nonmagnetic particle is introduced. Simulations demonstrate the impact of nucleation field of reversed domains on the magnetization reversal behavior and the magnetic properties.

  1. Article surveillance magnetic marker having an hysteresis loop with large Barkhausen discontinuities

    DOEpatents

    Humphrey, Floyd B.

    1987-01-01

    A marker for an electronic article surveillance system is disclosed comprising a body of magnetic material with retained stress and having a magnetic hysteresis loop with a large Barkhausen discontinuity such that, upon exposure of the marker to an external magnetic field whose field strength in the direction opposing the instantaneous magnetic polarization of the marker exceeds a predetermined threshold value, there results a regenerative reversal of the magnetic polarization of the marker. An electronic article surveillance system and a method utilizing the marker are also disclosed. Exciting the marker with a low frequency and low field strength, so long as the field strength exceeds the low threshold level for the marker, causes a regenerative reversal of magnetic polarity generating a harmonically rich pulse that is readily detected and easily distinguished.

  2. A differential algebraic approach for the modeling of polycrystalline ferromagnetic hysteresis with minor loops and frequency dependence

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Wang, Linxiang; Melnik, Roderick

    2016-07-01

    In the current paper, a nonlinear differential algebraic approach is proposed for the modeling of hysteretic dynamics of polycrystalline ferromagnetic materials. The model is constructed by employing a phenomenological theory to the magnetization orientation switching. For the modeling of hysteresis in polycrystalline ferromagnetic materials, the single crystal model is applied to each magnetic domain along its own principal axis. The overall dynamics of the polycrystalline materials is obtained by taking a weighted combination of the dynamics of all magnetic domains. The weight function for the combination is taken as the distribution function of the principal axes. Numerical simulations are performed and comparisons with its experimental counterparts are presented. The hysteretic dynamics caused by orientation switching processes is accurately captured by the proposed model. Minor hysteresis loops associated with partial-amplitude loadings are also captured. Rate dependence of the hysteresis loops are inherently incorporated into the model due to its differential nature.

  3. Modeling for Fatigue Hysteresis Loops of Carbon Fiber-Reinforced Ceramic-Matrix Composites under Multiple Loading Stress Levels

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    In this paper, the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) under multiple loading stress levels considering interface wear has been investigated using micromechanical approach. Under fatigue loading, the fiber/matrix interface shear stress decreases with the increase of cycle number due to interface wear. Upon increasing of fatigue peak stress, the interface debonded length would propagate along the fiber/matrix interface. The difference of interface shear stress existed in the new and original debonded region would affect the interface debonding and interface frictional slipping between the fiber and the matrix. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading, the interface slip lengths, i.e., the interface debonded length, interface counter-slip length and interface new-slip length, are determined by fracture mechanics approach. The fatigue hysteresis loops models under multiple loading stress levels have been developed. The effects of single/multiple loading stress levels and different loading sequences on fatigue hysteresis loops have been investigated. The fatigue hysteresis loops of unidirectional C/SiC composite under multiple loading stress levels have been predicted.

  4. Current and surface charge modified hysteresis loops in ferroelectric thin films

    DOE PAGESBeta

    Balke Wisinger, Nina; Jesse, Stephen; Maksymovych, Petro; Okatan, Mahmut Baris; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei

    2015-08-19

    Polarization domains in ferroelectric materials and the ability to orient them with an external electric field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelectric domains and ferroelectric domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its commercial availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelectric effect are barely discussed or considered. This becomes especiallymore » important for materials with a small piezoelectric coefficient or materials with unknown ferroelectric properties, including non-ferroelectric materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelectrics are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type experiments and offer a pathway to study additional phenomena besides ferroelectricity.« less

  5. Ferroeletricity and Double Hysteresis Loop Behavior in Even-Numbered n-Nylons

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongbo; Zhu, Lei; Litt, Morton

    2015-03-01

    Ferroelectric (FE) property in odd-numbered n-nylons has been known for a long time. In comparison, even-numbered n-nylons are claimed to be non-ferroelectric due to their non-polar crystalline structure, where the direction of hydrogen bonded dipoles alternates. Nevertheless, in this presentation, FE property is discovered in even n-nylons, and it is related to the mesomorphic crystalline structure formed via quenching and/or stretching. Although there was an earlier claim maintaining that FE behavior in melt-quenched nylon 6 was due to the amorphous phase, the conclusion is debatable and the understanding of the FE mechanism is still lacking. We find that poorly bonded amide dipoles, which result from the defective crystalline mesophase, play an important role in the FE behavior of nylon 12. In this mesophase, the chain conformation is smectic-like, twisted, and the hydrogen bonds are randomized. Therefore, this mesophase is abundant in defects and poorly bonded dipoles, which can easily flip under electric field. In addition, the hydrogen-bonded amides can serve as pinning points and induce double hysteresis loop behavior. This understanding illustrates that FE in even n-nylons originates from the defective crystalline phase rather than the amorphous region. NSF (DMR0907580).

  6. Anisotropy and shape of hysteresis loop of frozen suspensions of iron oxide nanoparticles in water

    NASA Astrophysics Data System (ADS)

    Boekelheide, Zoe; Gruettner, Cordula; Dennis, Cindi

    2014-03-01

    Colloidal suspensions of nanoparticles in liquids have many uses in biomedical applications. We studied approximately 50 nm diameter iron oxide particles dispersed in H2O for magnetic nanoparticle hyperthermia cancer treatment. Interactions between nanoparticles have been indicated for increasing the heat output under application of an alternating magnetic field, as in hyperthermia. Interactions vary dynamically with an applied field as the nanoparticles reorient and rearrange within the liquid. Therefore, we studied the samples below the liquid freezing point in a range of magnetic field strengths to literally freeze in the effects of interactions. We found that the shape of the magnetic hysteresis loop is squarer (higher anisotropy) when the sample was cooled in a high field, and less square (lower anisotropy) when the sample was cooled in a low or zero field. The cause is most likely the formation of long chains of nanoparticles up to 500 μm, which we observe optically. This increase in anisotropy may indicate improved heating ability for these nanoparticles under an alternating magnetic field.

  7. Quantum memory effects in noninteracting cold-atom systems: Hysteresis loop and lattice transformation

    NASA Astrophysics Data System (ADS)

    Chien, Chihchun; Metcalf, Mekena; Lai, Chenyen

    2016-05-01

    Memory effects are observable in magnetization, rechargeable batteries, and many systems exhibiting history-dependent states. Quantum memory effects are observable, for instance, in atomic superfluids. A counter-intuitive question is whether quantum memory effects can exist in noninteracting systems. Here we present two examples of cold-atom systems demonstrating memory effects in noninteracting systems. The first example is a ring-shaped potential loaded with noninteracting fermions. An artificial vector potential drives a current and with a tunable dissipative background, the current lags behind the driving and exhibits hysteresis loops. The dissipative energy can be controlled by the coupling between the fermions and the background. In the second example, cold atoms loaded in a tunable optical lattice transformed from the triangular to the kagome geometry. The kagome lattice supports a flat-band consisting of degenerate localized states. Quantum memory effects are observable after a lattice transformation as the steady-state density depends on the rate of the transformation. The versatility of memory effects in cold-atom systems promises novel applications in atomtronics.

  8. Phase transition and hysteresis loop in structured games with global updating

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Xu; Lü, Jinhu; Chen, Guanrong; Hui, P. M.

    2008-04-01

    We present a global payoff-based strategy updating model for studying cooperative behavior of a networked population. We adopt the Prisoner’s Dilemma game and the snowdrift game as paradigms for characterizing the interactions among individuals. We investigate the model on regular, small-world, and scale-free networks, and find multistable cooperation states depending on the initial cooperator density. In particular for the snowdrift game on small-world and scale-free networks, there exist a discontinuous phase transition and hysteresis loops of cooperator density. We explain the observed properties by theoretical predictions and simulation results of the average number of neighbors of cooperators and defectors, respectively. Our work indicates that individuals with more neighbors have a trend to preserve their initial strategies, which has strong impacts on the strategy updating of individuals with fewer neighbors; while the fact that individuals with few neighbors have to become cooperators to avoid gaining the lowest payoff plays significant roles in maintaining and spreading of cooperation strategy.

  9. Current and surface charge modified hysteresis loops in ferroelectric thin films

    SciTech Connect

    Balke Wisinger, Nina; Jesse, Stephen; Maksymovych, Petro; Okatan, Mahmut Baris; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei

    2015-08-19

    Polarization domains in ferroelectric materials and the ability to orient them with an external electric field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelectric domains and ferroelectric domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its commercial availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelectric effect are barely discussed or considered. This becomes especially important for materials with a small piezoelectric coefficient or materials with unknown ferroelectric properties, including non-ferroelectric materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelectrics are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type experiments and offer a pathway to study additional phenomena besides ferroelectricity.

  10. A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

    PubMed Central

    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

  11. A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope.

    PubMed

    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

  12. A New Model Based on Adaptation of the External Loop to Compensate the Hysteresis of Tactile Sensors

    PubMed Central

    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

  13. A new model based on adaptation of the external loop to compensate the hysteresis of tactile sensors.

    PubMed

    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

  14. The phase transition of ɛ-InxFe2-xO3 nanomagnets with a large thermal hysteresis loop (invited)

    NASA Astrophysics Data System (ADS)

    Yamada, Kana; Tokoro, Hiroko; Yoshikiyo, Marie; Yorinaga, Takenori; Namai, Asuka; Ohkoshi, Shin-ichi

    2012-04-01

    A large thermal hysteresis loop was observed in the phase transition on rod-shaped ɛ-InxFe2-xO3 (x ˜ 0.04) nanomagnets. The width of the thermal hysteresis loop, ΔT, increased with increasing rod length (l), i.e., ΔT = 6 K (l = 25 nm), 14 K (40 nm), 25 K (80 nm), and 47 K (170 nm). The observed ΔT value of 47 K is one of the largest values among insulating ferromagnetic materials. The thermal hysteresis loops were analyzed by the Slichter and Drickamer model, and the results showed that the transition enthalpy and entropy do not change. However, the elastic interaction parameter between the transition sites increases with an increasing l value. Maybe the correlation length of a propagating phonon due to elastic interaction competes with the rod length of the samples, causing the rod-length dependence of the thermal hysteresis loop.

  15. 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.

  16. Spectral properties of the Preisach hysteresis model with random input. II. Universality classes for symmetric elementary loops

    NASA Astrophysics Data System (ADS)

    Radons, Günter

    2008-06-01

    The Preisach model with symmetric elementary hysteresis loops and uncorrelated input is treated analytically in detail. It is shown that the appearance of long-time tails in the output correlations is a quite general feature of this model. The exponent η of the algebraic decay t-η , which may take any positive value, is determined by the tails of the input and the Preisach density. We identify the system classes leading to identical algebraic tails. These results imply the occurrence of 1/f noise for a large class of hysteretic systems.

  17. Dipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted hysteresis loops

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the constricted loop show a similar mechanism to the exchange coupling effect in magnetic multilayers.

  18. 3D and 1D calculation of hysteresis loops and energy products for anisotropic nanocomposite films with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Yuan, X. H.; Zhao, G. P.; Yue, Ming; Ye, L. N.; Xia, J.; Zhang, X. C.; Chang, J.

    2013-10-01

    In this paper, the magnetic reversal process, hysteresis loops and energy products for exchange-coupled Nd2Fe14B/α-Fe bilayers are studied systematically by a three-dimensional (3D) model. The 3D calculations are numerically solved using the finite difference method, where the results are carefully compared with those calculated by one-dimensional (1D) model. It is found that the calculated hysteresis loops and energy products based on the two methods are consistent with each other. Both nucleation fields and coercivities decrease monotonically as the soft layer thickness Ls increases. In addition, the calculated spatial distributions of magnetization orientations in the thickness direction at various applied fields based on both methods signify a three-step magnetic reversal process, which are nucleation, growth and displacement of the domain wall. The calculated magnetic orientations within the film plane, however, are totally different according to the two methods. The 3D calculation exhibits a process of vortex formation and annihilation. On the other hand, the 1D calculation gives a quasi-coherent one, where magnetization orientation is coherent in the film plane and varies in the thickness direction. This new reversal mechanism displayed in the film plane has a systematic influence on the nucleation fields, coercivity and energy products.

  19. Thermally induced all-optical inverter and dynamic hysteresis loops in graphene oxide dispersions.

    PubMed

    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

  20. Characterization of electrocaloric properties by indirect estimation and direct measurement of temperature-electric field hysteresis loops

    NASA Astrophysics Data System (ADS)

    Maiwa, Hiroshi

    2015-10-01

    The electrocaloric properties of Pb(Zr,Ti)O3(PZT)-based and Ba(Zr,Ti)O3 ceramics and Pb(Mg,Nb)O3-PbTiO3 (PMN-PT) crystals were investigated by the indirect estimation and direct measurement of temperature-electric field (T-E) hysteresis loops. The measured T-E loops showed a similar shape to strain-electric field (s-E) loops. The adiabatic temperature change ΔT due to electrocaloric effects was estimated from the polarization change of these samples. ΔTs of 0.48 and 0.66 K were estimated for the (Pb,La)(Zr,Ti)O3 (PLZT)(9.1/65/35) ceramics and PMN-PT crystals under a field of 30 kV/cm, respectively. The measured temperature changes ΔTs in these samples upon the release of the electric field from 30 kV/cm to zero were 0.39 and 0.36 K, respectively.

  1. Dynamical control of the spin transition inside the thermal hysteresis loop of a spin-crossover single crystal

    NASA Astrophysics Data System (ADS)

    Boukheddaden, Kamel; Sy, Mouhamadou; Paez-Espejo, Miguel; Slimani, Ahmed; Varret, François

    2016-04-01

    We have succeeded to achieve experimentally, using an adapted optical microscopy setup, the reversible control of the front transformation between the low-spin (LS)-high-spin (HS) interface in the spin-crossover (SC) single crystal [{Fe(NCSe)(py)2}2(m-bpypz)] undergoing a first-order transition at 112 K with a 7 K hysteresis width. For that, we first generate a phase separation state (a HS/LS interface at equilibrium) inside the hysteresis loop by tuning the light intensity of the microscope. In the second step, this intensity is monitored in such a way to drive, through a photo-heating process, the interface motion. This photo-control is found to be reversible, accurate and requiring a very small amount of energy. In addition the integrity of the crystal is maintained even after a large number of cycling. The experimental observations, are well described as a reaction diffusion process accounting for the front propagation and the photo-heating effects.

  2. The J-Meter Coercivity Spectrometer - Hysteresis Loop, IRM Acquisition Spectrum and Viscosity Spectrum in 6 Minutes

    NASA Astrophysics Data System (ADS)

    Enkin, R. J.; Nourgaliev, D.; Iassonov, P.

    2009-05-01

    The J-Meter Coercivity Spectrometer uses an innovative robust design for measuring a geological sample's magnetic hysteresis loop, IRM acquisition spectrum and viscosity spectrum in 6 minutes. With this tool, several labs around the world have been able measure large sample collections and develop useful magnetic proxies for a variety of paleoclimate, diagenesis and other studies. The main element of the J-meter is a pulse magnetometer, in which an electromotive force pulse is induced in an array of pick-up coils by the magnetic field of a sample moving at a high speed past the coils. The sample is placed near the rim of a 50 cm diameter plexiglas disk which rotates 18 times a second through the pole pieces of an electromagnet. Both the induced and remanent magnetization are measured during each rotation of the disk. Induced magnetization for hysteresis loops are measure with a set of pick-up coils mounted directly on the pole pieces, similar to the geometry used for a vibrating sample magnetometer. The magnetic remanence is measured with a second array of coils situated away from the electromagnet and surrounded by a three-layer mu-metal shield. The electromagnet field is ramped up to 500 mT, and the down to the opposite polarity (-500 mT). The J meter is called a coercivity spectrometer because it is particularly well suited to measuring the IRM acquisition curve with sufficient sensitivity and resolution to take the derivative which defines the coercivity spectrum. To finish each measurement, the magnetic field is cut to zero and the viscous demagnetization is monitored for 100s, mostly following a log(time) relationship but with perturbations determined by the grain size distribution of the finest grains. A suite of analysis programs have been developed to determine hysteresis parameters and S-ratios, and to characterize coercivity and viscosity spectra. We present a series of applications demonstrating the power of the J-Meter to trace sediment sources

  3. Double hysteresis loop induced by defect dipoles in ferroelectric Pb(Zr{sub 0.8}Ti{sub 0.2})O{sub 3} thin films

    SciTech Connect

    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.

  4. An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples--a useful setup for magnetic hyperthermia applications.

    PubMed

    Connord, V; Mehdaoui, B; Tan, R P; Carrey, J; Respaud, M

    2014-09-01

    A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications. PMID:25273736

  5. An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples—A useful setup for magnetic hyperthermia applications

    NASA Astrophysics Data System (ADS)

    Connord, V.; Mehdaoui, B.; Tan, R. P.; Carrey, J.; Respaud, M.

    2014-09-01

    A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications.

  6. Dipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted hysteresis loops

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the multilayers stack behave as dipole spring ferroelectric, named in analogy to exchange spring magnets in magnetic multilayers that show similar loops.

  7. Tailoring Staircase-like Hysteresis Loops in Electrodeposited Trisegmented Magnetic Nanowires: a Strategy toward Minimization of Interwire Interactions.

    PubMed

    Zhang, Jin; Agramunt-Puig, Sebastià; Del-Valle, Núria; Navau, Carles; Baró, Maria D; Estradé, Sònia; Peiró, Francesca; Pané, Salvador; Nelson, Bradley J; Sanchez, Alvaro; Nogués, Josep; Pellicer, Eva; Sort, Jordi

    2016-02-17

    A new strategy to minimize magnetic interactions between nanowires (NWs) dispersed in a fluid is proposed. Such a strategy consists of preparing trisegmented NWs containing two antiparallel ferromagnetic segments with dissimilar coercivity separated by a nonmagnetic spacer. The trisegmented NWs exhibit a staircase-like hysteresis loop with tunable shape that depends on the relative length of the soft- and hard-magnetic segments and the respective values of saturation magnetization. Such NWs are prepared by electrodepositing CoPt/Cu/Ni in a polycarbonate (PC) membrane. The antiparallel alignment is set by applying suitable magnetic fields while the NWs are still embedded in the PC membrane. Analytic calculations are used to demonstrate that the interaction magnetic energy from fully compensated trisegmented NWs with antiparallel alignment is reduced compared to a single-component NW with the same length or the trisegmented NWs with the two ferromagnetic counterparts parallel to each other. The proposed approach is appealing for the use of magnetic NWs in certain biological or catalytic applications where the aggregation of NWs is detrimental for optimized performance. PMID:26804742

  8. Unveiling the Mechanism for the Split Hysteresis Loop in Epitaxial Co2Fe1-xMnxAl Full-Heusler Alloy Films

    PubMed Central

    Tao, X. D.; Wang, H. L.; Miao, B. F.; Sun, L.; You, B.; Wu, D.; Zhang, W.; Oepen, H. P.; Zhao, J. H.; Ding, H. F.

    2016-01-01

    Utilizing epitaxial Co2Fe1-xMnxAl full-Heusler alloy films on GaAs (001), we address the controversy over the analysis for the split hysteresis loop which is commonly found in systems consisting of both uniaxial and fourfold anisotropies. Quantitative comparisons are carried out on the values of the twofold and fourfold anisotropy fields obtained with ferromagnetic resonance and vibrating sample magnetometer measurements. The most suitable model for describing the split hysteresis loop is identified. In combination with the component resolved magnetization measurements, these results provide compelling evidences that the switching is caused by the domain wall nucleation and movements with the switching fields centered at the point where the energy landscape shows equal minima for magnetization orienting near the easy axis and the field supported hard axis. PMID:26733075

  9. Unveiling the Mechanism for the Split Hysteresis Loop in Epitaxial Co2Fe1-xMnxAl Full-Heusler Alloy Films

    NASA Astrophysics Data System (ADS)

    Tao, X. D.; Wang, H. L.; Miao, B. F.; Sun, L.; You, B.; Wu, D.; Zhang, W.; Oepen, H. P.; Zhao, J. H.; Ding, H. F.

    2016-01-01

    Utilizing epitaxial Co2Fe1-xMnxAl full-Heusler alloy films on GaAs (001), we address the controversy over the analysis for the split hysteresis loop which is commonly found in systems consisting of both uniaxial and fourfold anisotropies. Quantitative comparisons are carried out on the values of the twofold and fourfold anisotropy fields obtained with ferromagnetic resonance and vibrating sample magnetometer measurements. The most suitable model for describing the split hysteresis loop is identified. In combination with the component resolved magnetization measurements, these results provide compelling evidences that the switching is caused by the domain wall nucleation and movements with the switching fields centered at the point where the energy landscape shows equal minima for magnetization orienting near the easy axis and the field supported hard axis.

  10. Unveiling the Mechanism for the Split Hysteresis Loop in Epitaxial Co2Fe1-xMnxAl Full-Heusler Alloy Films.

    PubMed

    Tao, X D; Wang, H L; Miao, B F; Sun, L; You, B; Wu, D; Zhang, W; Oepen, H P; Zhao, J H; Ding, H F

    2016-01-01

    Utilizing epitaxial Co2Fe1-xMnxAl full-Heusler alloy films on GaAs (001), we address the controversy over the analysis for the split hysteresis loop which is commonly found in systems consisting of both uniaxial and fourfold anisotropies. Quantitative comparisons are carried out on the values of the twofold and fourfold anisotropy fields obtained with ferromagnetic resonance and vibrating sample magnetometer measurements. The most suitable model for describing the split hysteresis loop is identified. In combination with the component resolved magnetization measurements, these results provide compelling evidences that the switching is caused by the domain wall nucleation and movements with the switching fields centered at the point where the energy landscape shows equal minima for magnetization orienting near the easy axis and the field supported hard axis. PMID:26733075

  11. Lags and Hysteresis Loops of Cosmic Ray Intensity Versus Sunspot Numbers: Quantitative Estimates for Cycles 19 - 23 and a Preliminary Indication for Cycle 24

    NASA Astrophysics Data System (ADS)

    Kane, R. P.

    2014-07-01

    Hysteresis plots between cosmic-ray (CR) intensity (recorded at the Climax station) and sunspot relative number R Z show broad loops in odd cycles (19, 21, and 23) and narrow loops in even cycles (20 and 22). However, in the even cycles, the loops are not narrow throughout the whole cycle; around the sunspot-maximum period, a broad loop is seen. Only in the rising and declining phases, the loops are narrow in even cycles. The CR modulation is known to have a delay with respect to R Z, and the delay was believed to be longer in odd cycles (19, 21, and 23; about 10 months) than the delay in even cycles (20 and 22; about 3 - 5 months). When this was reexamined, it was found that the delays are different during the sunspot-minimum periods (2, 6, and 14 months for odd cycles and 7 and 9 months for even cycles) and sunspot-maximum periods (0, 4, and 7 months for odd cycles and 5 and 8 months for even cycles). Thus, the differences between odd and even cycles are not significant throughout the whole cycle. In the recent even cycle 24, hysteresis plots show a preliminary broadening near the sunspot maximum, which occurred recently (February 2012). The CR level (recorded at Newark station) is still high in 2013, indicating a long lag (exceeding 10 months) with respect to the sunspot maximum.

  12. Research on hysteresis loop considering the prestress effect and electrical input dynamics for a giant magnetostrictive actuator

    NASA Astrophysics Data System (ADS)

    Zhu, Yuchuan; Yang, Xulei; Wereley, Norman M.

    2016-08-01

    In this paper, focusing on the application-oriented giant magnetostrictive material (GMM)-based electro-hydrostatic actuator, which features an applied magnetic field at high frequency and high amplitude, and concentrating on the static and dynamic characteristics of a giant magnetostrictive actuator (GMA) considering the prestress effect on the GMM rod and the electrical input dynamics involving the power amplifier and the inductive coil, a methodology for studying the static and dynamic characteristics of a GMA using the hysteresis loop as a tool is developed. A GMA that can display the preforce on the GMM rod in real-time is designed, and a magnetostrictive model dependent on the prestress on a GMM rod instead of the existing quadratic domain rotation model is proposed. Additionally, an electrical input dynamics model to excite GMA is developed according to the simplified circuit diagram, and the corresponding parameters are identified by the experimental data. A dynamic magnetization model with the eddy current effect is deduced according to the Jiles–Atherton model and the Maxwell equations. Next, all of the parameters, including the electrical input characteristics, the dynamic magnetization and the mechanical structure of GMA, are identified by the experimental data from the current response, magnetization response and displacement response, respectively. Finally, a comprehensive comparison between the model results and experimental data is performed, and the results show that the test data agree well with the presented model results. An analysis on the relation between the GMA displacement response and the parameters from the electrical input dynamics, magnetization dynamics and mechanical structural dynamics is performed.

  13. Mechanism of the hysteretic behavior of the magnetoresistance of granular HTSCs: The universal nature of the width of the magnetoresistance hysteresis loop

    SciTech Connect

    Balaev, D. A. Dubrovskii, A. A.; Shaikhutdinov, K. A.; Popkov, S. I.; Gokhfeld, D. M.; Gokhfeld, Yu. S.; Petrov, M. I.

    2009-02-15

    The hysteretic behavior of the magnetoresistance R(H) of granular high-temperature superconductors (HTSCs) of the Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and La-Sr-Cu-O classical systems is investigated for transport current densities lower and higher than the critical density (at H = 0). All systems exhibit universal behavior of the width of the magnetoresistance hysteresis loop: independence of transport current under identical external conditions. This means that flux trapping in HTSC grains is the main mechanism controlling the hysteretic behavior of the magnetoresistance of granular HTSCs, while pinning of Josephson vortices in the intragranular medium makes no appreciable contribution to the formation of magnetoresistance hysteresis (when transport current flows through the sample). Experimental data on relaxation of residual resistance after the action of a magnetic field also confirm this conclusion.

  14. Velocity of the high-spin low-spin interface inside the thermal hysteresis loop of a spin-crossover crystal, via photothermal control of the interface motion.

    PubMed

    Slimani, Ahmed; Varret, François; Boukheddaden, Kamel; Garrot, Damien; Oubouchou, Hassane; Kaizaki, Sumio

    2013-02-22

    We investigated by optical microscopy the thermal transition of the spin-crossover dinuclear iron(II) compound [(Fe(NCSe)(py)(2))(2)(m-bpypz)]. In a high-quality crystal the high-spin (HS) low-spin (LS) thermal transition took place with a sizable hysteresis, at ~108 K and ~116 K on cooling and heating, respectively, through the growth of a single macroscopic domain with a straight LS and HS interface. The interface orientation was almost constant and its propagation velocity was close to ~6 and 26 μ m s(-1) for the on-cooling and on-heating processes, respectively. We found that the motion of the interface was sensitive to the intensity of the irradiation beam of the microscope, through a photothermal effect. By fine-tuning the intensity we could stop and even reverse the interface motion. This way we stabilized a biphasic state of the crystal, and we followed the spontaneous motion of the interface at different temperatures inside the thermal hysteresis loop. This experiment gives access for the first time to an accurate determination of the equilibrium temperature in the case of thermal hysteresis--which was not accessible by the usual quasistatic investigations. The temperature dependence of the propagation velocity inside the hysteretic interval was revealed to be highly nonlinear, and it was quantitatively reproduced by a dynamical mean-field theory, which made possible an estimate of the macroscopic energy barrier. PMID:23473199

  15. Compensation effects and relation between the activation energy of spin transition and the hysteresis loop width for an iron(ii) complex.

    PubMed

    Bushuev, Mark B; Pishchur, Denis P; Nikolaenkova, Elena B; Krivopalov, Viktor P

    2016-06-22

    The enthalpy-entropy compensation was observed for the cooperative → spin transition (the phase is a mononuclear complex [FeL2](BF4)2, L is 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)-6-methylpyrimidine). The physical origin of this effect is the fact that the → spin transition is the first order phase transition accompanied by noticeable variations in the Tonset↑, ΔH and ΔS values. Higher ΔH and ΔS values are correlated with higher Tonset↑ values. The higher the enthalpy and entropy of the spin transition, the wider the hysteresis loop. The kinetic compensation effect, i.e. a linear relationship between ln A and Ea, was observed for the → spin transition. Moreover, an isokinetic relationship was detected in this system: the Arrhenius lines (ln k vs. 1/T) obtained from magnetochemical data for different samples of the phase undergoing the → transition show a common point of intersection (Tiso = 490 ± 2 K, ln kiso = -6.0 ± 0.2). The validity of this conclusion was confirmed by the Exner-Linert statistical method. This means that the isokinetic relationship and the kinetic compensation effect (ln A vs. Ea) in this system are true ones. The existence of a true kinetic compensation effect is supported independently by the fact that the hysteresis loop width for the cooperative spin transition ↔ increases with increasing activation barrier height. Estimating the energy of excitations for the phase with Tiso ∼ 490 K yields wavenumbers of ca. 340 cm(-1) corresponding to the frequencies of the stretching vibrations of the Fe(LS)-N bonds, i.e. the bonds directly involved in the mechanism of the spin transition. This is the first observation of the kinetic compensation effect (ln A vs. Ea) and the isokinetic relationship for a cooperative spin crossover system showing thermal hysteresis. Our results provide the first experimental evidence that the higher the activation barrier for the spin transition, the wider the hysteresis loop for a

  16. Scaling Behavior of Amplitude-Dependent Ferroelectric Hysteresis Loops in an Epitaxial PbZr0.2Ti0.8O3 Thin Film

    SciTech Connect

    Yang, Sang Mo; Jang, S. Y.; Kim, T. H.; Kim, Hun-Ho; Lee, Ho Nyung; Yoon, J. -G.

    2011-01-01

    We investigated the scaling behavior of ferroelectric (FE) hysteresis loops as a function of the applied field amplitude (E{sub 0}) in a high-quality epitaxial PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin film. We observed that the areas of the polarization-electric field hysteresis loops (A) followed the scaling law A {proportional_to} E{sub 0}{sup {alpha}}, with the exponent {alpha} = 0.45 {+-} 0.01. This result is in excellent agreement with the theoretical prediction of {alpha} by the two-dimensional Ising model. In addition, we found that the coercive field (E{sub C}) showed E{sub C} {proportional_to} E{sub 0}{sup {gamma}} with the exponent {gamma} = 0.28 {+-} 0.01. We attribute this relationship to the difference in the sweep rate of the field amplitude E{sub 0}. From the obtained {gamma} value, the growth dimension of FE domains is found to be about 1.68 in our epitaxial PZT thin film.

  17. Enhancement of magnetic domain topologies in Co/Pt thin films by fine tuning the magnetic field path throughout the hysteresis loop

    NASA Astrophysics Data System (ADS)

    Westover, Andrew S.; Chesnel, Karine; Hatch, Kelsey; Salter, Philip; Hellwig, Olav

    2016-02-01

    We have studied the influence of magnetic history on the topology of perpendicular magnetic domains in a thin ferromagnetic film made of [Co(8 Å)/Pt(7 Å)]50 multilayers. More specifically, we have followed the morphological changes in the domain pattern when applying a magnetic field perpendicular to the layer, throughout minor and major magnetization loops, and in the resulting remanent state. We carried out this study by using MFM microscopy with an in-situ magnetic field. We find that the morphology of the magnetic domain pattern is greatly influenced by the magnetic history of the material and that some features, such as the degree of bubbliness (i.e., the extent of bubble domain formation) and density of isolated domains can be enhanced by fine tuning the magnetic field path within the major hysteresis loop towards different remanent states. In particular, we see how hysteresis is correlated to irreversible changes in the domain morphology. More interestingly, we find that the magnetic domain morphology at remanence can be changed from an interconnected labyrinthine stripe state to a state of many separated bubble domains by fine tuning the magnitude of the field previously applied to the material. These results agree well with other findings, such as the magnetic reversal behavior and magnetic memory effects in Co/Pt multilayers, and provide opportunities for potential technological applications.

  18. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    SciTech Connect

    Wieserman, W.R.; Schwarze, G.E.; Niedra, J.M.

    1994-09-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglass 2605SC over the frequency range of 1-50 kHz and temperature range of 23-300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  19. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  20. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loop for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  1. Hysteresis in single and polycrystalline iron thin films: Major and minor loops, first order reversal curves, and Preisach modeling

    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.

  2. Steady state boiling crisis in a helium vertically heated natural circulation loop - Part 1: Critical heat flux, boiling crisis onset and hysteresis

    NASA Astrophysics Data System (ADS)

    Furci, H.; Baudouy, B.; Four, A.; Meuris, C.

    2016-01-01

    Experiments were conducted on a 2-m high two-phase helium natural circulation loop operating at 4.2 K and 1 atm. The same loop was used in two experiments with different heated section internal diameter (10 and 6 mm). The power applied on the heated section wall was controlled in increasing and decreasing sequences, and temperature along the section, mass flow rate and pressure drop evolutions were recorded. The values of critical heat flux (CHF) were found at different positions of the test section, and the post-CHF regime was studied. The predictions of CHF by existing correlations were good in the downstream portion of the section, however CHF anomalies have been observed near the entrance, in the low quality region. In resonance with this, the re-wetting of the surface has distinct hysteresis behavior in each of the two CHF regions. Furthermore, hydraulics effects of crisis, namely on friction, were studied (Part 2). This research is the starting point to future works addressing transients conducing to boiling crisis in helium natural circulation loops.

  3. Thermo-magnetic history effects in the giant magnetostriction across the first-order transition and minor hysteresis loops modeling in Fe0.955Ni0.045Rh alloy.

    PubMed

    Manekar, Meghmalhar; Sharma, V K; Roy, S B

    2012-05-30

    Results of temperature- and magnetic field-dependent strain measurements across the first-order antiferromagnetic to ferromagnetic phase transition in Fe(0.955)Ni(0.045)Rh are presented. Distinct thermal and magnetic field hystereses are observed in the measured strain across the phase transition. The minor hysteresis loops inside the hysteretic regime across the temperature-driven transition are modeled using the Preisach model of hysteresis. The applicability of the Preisach model to explain the general features of minor hysteresis loops is discussed for a disorder influenced first-order transition. The minor hysteresis loops show the property of retaining the memory of the starting or end point of the temperature cycle followed within the hysteretic region. A larger temperature excursion within the hysteretic region wipes out the memory of a smaller temperature cycle which contains one of the extrema of the larger cycle. The end-point memory and the wiping-out property of the minor hysteresis loops can be described quite well within the Preisach model, irrespective of the temperature history followed to reach a particular starting point. Thermo-magnetic history effects across the magnetic field-induced transition are explained, which will enable the choice of the starting point of an experimental cycle in the field-temperature phase space so as to achieve the desired functionality. Our results highlight the necessity to understand the influence of disorder on a first-order phase transition so as to achieve a repeatable performance of materials whose functionalities are based on such a transition. PMID:22543692

  4. 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.

  5. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles.

    PubMed

    Xu, S T; Ma, Y Q; Zheng, G H; Dai, Z X

    2015-04-21

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23,817 and 15,056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance. PMID:25787852

  6. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, S. T.; Ma, Y. Q.; Zheng, G. H.; Dai, Z. X.

    2015-04-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23 817 and 15 056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

  7. 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.

  8. Hysteresis in the Sky

    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.

  9. Mathematical models of hysteresis

    SciTech Connect

    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.

  10. Template-free synthesis of Nd{sub 0.1}Bi{sub 0.9}FeO{sub 3} nanotubes with large inner diameter and wasp-waisted hysteresis loop

    SciTech Connect

    Li, X.; Guo, F.; Wang, X.; Wang, S. Y. E-mail: wfliu@tju.edu.cn; Xu, X. L.; Liu, W. F. E-mail: wfliu@tju.edu.cn; Gao, J.

    2015-08-10

    One-dimensional (1D) nanotubes of Nd{sub 0.1}Bi{sub 0.9}FeO{sub 3} (NBFO) with an inner diameter of ∼50 nm were synthesized via sol-gel based electrospinning without template assistant. The phases, morphologies, crystalline structures, and magnetic properties of these 1D nanostructures were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and SQUID, respectively. It was found that the calcination condition plays a crucial role in determining the morphologies and the magnetic properties. Interestingly, these 1D NBFO nanotubes exhibit wasp-waisted magnetic hysteresis with a lower coercivity and larger saturation magnetization, which were prevalent in natural rocks and artificial composite materials. The origin of these wasp-waisted hysteresis loops was discussed.

  11. Modeling of hysteresis in gene regulatory networks.

    PubMed

    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

  12. [Mathematical models of hysteresis

    SciTech Connect

    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.

  13. 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.

  14. A magnetic hysteresis model

    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.

  15. A trinuclear defect-grid iron(II) spin crossover complex with a large hysteresis loop that is readily silenced by solvent vapor.

    PubMed

    Steinert, Markus; Schneider, Benjamin; Dechert, Sebastian; Demeshko, Serhiy; Meyer, Franc

    2014-06-10

    A new type of [2×2] matrix-like complexes with one vertex devoid of a metal ion has been selectively synthesized. The defect-grid triiron(II) complex exhibits a sharp and complete spin-crossover (SCO) from the 1HS-2LS to the 2HS-1LS state (HS: high spin; LS: low spin) with wide hysteresis near room temperature. Although the "structurally soft" H-bonded vertex, elastically coupled to the metal ions, accounts for the stabilization of spin states, it also mediates a dramatic, yet reversible, response to the uptake of exogenous solvent molecules leading to silencing of the SCO. The high sensitivity towards those guest molecules, the short response time upon exposure, and the smooth reversibility of guest binding are favorable characteristics for future sensing applications of such defect grids. PMID:24854423

  16. 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.

  17. 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.

  18. Hysteresis in a quantized superfluid 'atomtronic' circuit.

    PubMed

    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

  19. The New P.E.

    ERIC Educational Resources Information Center

    Vandertie, Joan; Corner, Amy B.; Corner, Kevin J.

    2012-01-01

    Marana Middle School in Tucson, Ariz., scrapped its traditional P.E. program that emphasized team sports and shifted to a program that focuses on lifetime fitness, student choice in activities, and nutrition and health education. The program also includes student leadership development and informal community service. As a result, Marana students…

  20. 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.

  1. 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.

  2. Introducing a domain flexing function in the Jiles-Atherton hysteresis model

    NASA Astrophysics Data System (ADS)

    Miljavec, Damijan; Zidarič, Bogomir

    The Jiles-Atherton hysteresis model (J-A model) exhibits a certain unphysical behavior when magnetic excitation reaches or reverses from the extremity of the hysteresis loop. Introducing a domain flexing function, coherent with the magnetic excitation level, improves accuracy of the J-A hysteresis model and at the same time prevents its unphysical behavior. Moreover, applying this function also improves representation of inner (lower excitation level) hysteresis loops. Implementation of magnetic excitation dependence in the domain flexing function adds a valuable parameter to the J-A original model on the way towards its further optimization. In the proposed hysteresis model, genetic algorithms are used in parameters optimization.

  3. Hysteresis in Metal Hydrides.

    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)

  4. 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.

  5. Evaluation of fatigue damage in steels using Preisach model analysis of magnetic hysteresis measurements

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.; Melikhov, Y. Y.; Kadlecová, J.; Perevertov, O. V.; Tomáš, I.; Ring, A. P.; Jiles, D. C.

    2001-04-01

    The Preisach model analysis of magnetic hysteresis measurements has been applied to evaluate the microstructural changes in steels subjected to cyclic loading. Families of hysteresis loops were measured to obtain the Preisach-like functions. Barkhausen effect signals were also measured. The Preisach representation was found to be more sensitive to the increase in the number of stress cycles during the stable fatigue stage than the traditional hysteresis loop properties and Barkhausen effect signals.

  6. Generalization of a model of hysteresis for dynamical systems.

    PubMed

    Piquette, Jean C; McLaughlin, Elizabeth A; Ren, Wei; Mukherjee, Binu K

    2002-06-01

    A previously described model of hysteresis [J. C. Piquette and S. E. Forsythe, J. Acoust. Soc. Am. 106, 3317-3327 (1999); 106, 3328-3334 (1999)] is generalized to apply to a dynamical system. The original model produces theoretical hysteresis loops that agree well with laboratory measurements acquired under quasi-static conditions. The loops are produced using three-dimensional rotation matrices. An iterative procedure, which allows the model to be applied to a dynamical system, is introduced here. It is shown that, unlike the quasi-static case, self-crossing of the loops is a realistic possibility when inertia and viscous friction are taken into account. PMID:12083200

  7. Adsorption hysteresis for a slit-like pore model

    NASA Astrophysics Data System (ADS)

    Kutarov, V. V.; Tarasevich, Yu. I.; Aksenenko, E. V.; Ivanova, Z. G.

    2011-07-01

    The Frenkel-Halsey-Hill equation is used to describe the adsorption branch of a hysteresis loop upon polylayer adsorption with an H3 loop according to IUPAC nomenclature. The equation for the desorption branch of a hysteresis loop is derived from a combined solution to the equation for the Gibbs potential change, given the adsorbent swelling and pore connectivity function, and the Laplace equation taken for the conditions of infinitely elongated meniscus. This equation is shown to connect the adsorbate relative pressure in a bulk phase for the desorption branch of a hysteresis loop with the key parameters of the adsorption system. The equation obtained was verified by a water adsorption isotherm on natural mineral schungite.

  8. 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.

  9. 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.

  10. Hail Growth Hysteresis.

    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.

  11. Unveiling magnetic Hysteresis

    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.

  12. 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.

  13. Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling

    PubMed Central

    Lee, Hyo-Chang; Chung, Chin-Wook

    2015-01-01

    Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics. PMID:26482650

  14. Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling

    NASA Astrophysics Data System (ADS)

    Lee, Hyo-Chang; Chung, Chin-Wook

    2015-10-01

    Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

  15. Magnetic hysteresis curve influenced by power-semiconductor characteristics in pulse-width-modulation inverter

    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.

  16. 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.

  17. 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.

  18. 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.

  19. Vortex flow hysteresis

    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.

  20. On physical aspects of the Jiles-Atherton hysteresis models

    NASA Astrophysics Data System (ADS)

    Zirka, Sergey E.; Moroz, Yuriy I.; Harrison, Robert G.; Chwastek, Krzysztof

    2012-08-01

    The physical assumptions underlying the static and dynamic Jiles-Atherton (JA) hysteresis models are critically analyzed. It is shown that the energy-balance method used in deriving these models is actually closer to a balance of coenergies, thereby depriving the resulting JA phenomenology of physical meaning. The non-physical basis of its dynamic extension is demonstrated by a sharp contrast between hysteresis loops predicted by the model and those measured for grain-oriented steel under conditions of controlled sinusoidal flux density at frequencies of 50, 100, and 200 Hz.

  1. The frequency-dependent Jiles-Atherton hysteresis model

    NASA Astrophysics Data System (ADS)

    Malczyk, Robert; Izydorczyk, Jacek

    2015-04-01

    An extension of the Jiles-Atherton (J-A) magnetic hysteresis model is proposed in the paper. The physical J-A model has been substituted with the specially chosen mathematical Chua model. The proposed model produces identical results to those of the original J-A model for the static magnetic hysteresis loop. The new model permits the inclusion of a wide variety of additional effects observed for ferromagnetic materials without invalidating the well-known and broadly used J-A model parameters. Thus, it is possible to effectively model phenomena, whose detailed physical model would require complex mathematical calculations.

  2. Unconventional dynamic hysteresis in a periodic assembly of paramagnetic colloids

    NASA Astrophysics Data System (ADS)

    Tierno, Pietro; Johansen, Tom H.; Sancho, J. M.

    2013-06-01

    Dynamic hysteresis phenomena are widespread in physical sciences and describe the complex behavior of systems driven out of equilibrium by a periodic forcing. We use here paramagnetic colloids above a stripe-patterned garnet film as the model system to study dynamic hysteresis, the latter induced when the particles are periodically translated by an oscillating magnetic field. In contrast to the expected behavior for a bistable system, we observe that the area of the hysteresis loop decreases by increasing the driving frequency and reduces to zero for frequencies higher than 5-7s-1. To explain the experimental results, we develop a simple model based on an overdamped Brownian particle driven by a periodic potential with an oscillating amplitude.

  3. Hysteresis modeling in ballistic carbon nanotube field-effect transistors.

    PubMed

    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

  4. Sinusoidal input describing function for hysteresis followed by elementary backlash

    NASA Technical Reports Server (NTRS)

    Ringland, R. F.

    1976-01-01

    The author proposes a new sinusoidal input describing function which accounts for the serial combination of hysteresis followed by elementary backlash in a single nonlinear element. The output of the hysteresis element drives the elementary backlash element. Various analytical forms of the describing function are given, depending on the a/A ratio, where a is the half width of the hysteresis band or backlash gap, and A is the amplitude of the assumed input sinusoid, and on the value of the parameter representing the fraction of a attributed to the backlash characteristic. The negative inverse describing function is plotted on a gain-phase plot, and it is seen that a relatively small amount of backlash leads to domination of the backlash character in the describing function. The extent of the region of the gain-phase plane covered by the describing function is such as to guarantee some form of limit cycle behavior in most closed-loop systems.

  5. Hysteresis of Freedericksz transition in confined light beams

    SciTech Connect

    Ledney, M. F. Tarnavsky, A. S.

    2010-03-15

    The effect of the transverse confinement of an incident light beam on the hysteresis of light-induced Freedericksz transition in a nematic liquid crystal cell is considered. The thresholds of the orientational instability of the director with an increase and decrease in the light beam's intensity are calculated numerically in relation to its transverse size. The hysteresis loop width is shown to change nonmonotonically with an increase in the transverse dimension. In contrast to a homogeneous light beam, the hysteresis existence region is determined not only by the parameter (K{sub 3} - K{sub 1})/K{sub 3} but also by the parameter K{sub 2}/K{sub 3}. With an increase in the transverse beam size, the critical values of the parameter (K{sub 3} - K{sub 1})/K{sub 3} increase, while those of the parameter K{sub 2}/K{sub 3} decrease.

  6. An Energy-Based Hysteresis Model for Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

    Calkins, F. T.; Smith, R. C.; Flatau, A. B.

    1997-01-01

    This paper addresses the modeling of hysteresis in magnetostrictive transducers. This is considered in the context of control applications which require an accurate characterization of the relation between input currents and strains output by the transducer. This relation typically exhibits significant nonlinearities and hysteresis due to inherent properties of magnetostrictive materials. The characterization considered here is based upon the Jiles-Atherton mean field model for ferromagnetic hysteresis in combination with a quadratic moment rotation model for magnetostriction. As demonstrated through comparison with experimental data, the magnetization model very adequately quantifies both major and minor loops under various operating conditions. The combined model can then be used to accurately characterize output strains at moderate drive levels. The advantages to this model lie in the small number (six) of required parameters and the flexibility it exhibits in a variety of operating conditions.

  7. Hysteresis modeling in ballistic carbon nanotube field-effect transistors

    PubMed Central

    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

  8. 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.

  9. 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.

  10. Conductance hysteresis in the voltage-dependent anion channel.

    PubMed

    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

  11. Mastering hysteresis in magnetocaloric materials.

    PubMed

    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

  12. 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.

  13. Strategy for stabilization of the antiferroelectric phase (Pbma) over the metastable ferroelectric phase (P2{sub 1}ma) to establish double loop hysteresis in lead-free (1−x)NaNbO{sub 3}-xSrZrO{sub 3} solid solution

    SciTech Connect

    Guo, Hanzheng Randall, Clive A.; Shimizu, Hiroyuki; Mizuno, Youichi

    2015-06-07

    A new lead-free antiferroelectric solid solution system, (1−x)NaNbO{sub 3}-xSrZrO{sub 3}, was rationalized through noting the crystal chemistry trend, of decreasing the tolerance factor and an increase in the average electronegativity of the system. The SrZrO{sub 3} doping was found to effectively stabilize the antiferroelectric (P) phase in NaNbO{sub 3} without changing its crystal symmetry. Preliminary electron diffraction and polarization measurements were presented which verified the enhanced antiferroelectricity. In view of our recent report of another lead-free antiferroelectric system (1−x)NaNbO{sub 3}-xCaZrO{sub 3} [H. Shimizu et al. “Lead-free antiferroelectric: xCaZrO{sub 3} - (1−x)NaNbO{sub 3} system (0 ≤ x ≤ 0.10),” Dalton Trans. (published online)], the present results point to a general strategy of utilizing tolerance factor to develop a broad family of new lead-free antiferroelectrics with double polarization hysteresis loops. We also speculate on a broad family of possible solid solutions that could be identified and tested for this important type of dielectric.

  14. 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.

  15. Barkhausen discontinuities and hysteresis of ferromagnetics: New stochastic approach

    SciTech Connect

    Vengrinovich, Valeriy

    2014-02-18

    The magnetization of ferromagnetic material is considered as periodically inhomogeneous Markov process. The theory assumes both statistically independent and correlated Barkhausen discontinuities. The model, based on the chain evolution-type process theory, assumes that the domain structure of a ferromagnet passes successively the steps of: linear growing, exponential acceleration and domains annihilation to zero density at magnetic saturation. The solution of stochastic differential Kolmogorov equation enables the hysteresis loop calculus.

  16. Domain-wall motion in random potential and hysteresis modeling

    SciTech Connect

    Pasquale, M.; Basso, V.; Bertotti, G.; Jiles, D.C.; Bi, Y.

    1998-06-01

    Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop typical of the Jiles{endash}Atherton model and then extend its validity to cases where mean-field effects and reversible contributions are present. {copyright} {ital 1998 American Institute of Physics.}

  17. Domain-wall motion in random potential and hysteresis modeling

    NASA Astrophysics Data System (ADS)

    Pasquale, M.; Basso, V.; Bertotti, G.; Jiles, D. C.; Bi, Y.

    1998-06-01

    Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop typical of the Jiles-Atherton model and then extend its validity to cases where mean-field effects and reversible contributions are present.

  18. Dynamic magnetic hysteresis and nonlinear susceptibility of antiferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kalmykov, Yuri P.; Ouari, Bachir; Titov, Serguey V.

    2016-08-01

    The nonlinear ac stationary response of antiferromagnetic nanoparticles subjected to both external ac and dc fields of arbitrary strength and orientation is investigated using Brown's continuous diffusion model. The nonlinear complex susceptibility and dynamic magnetic hysteresis (DMH) loops of an individual antiferromagnetic nanoparticle are evaluated and compared with the linear regime for extensive ranges of the anisotropy, the ac and dc magnetic fields, damping, and the specific antiferromagnetic parameter. It is shown that the shape and area of the DMH loops of antiferromagnetic particles are substantially altered by applying a dc field that permits tuning of the specific magnetic power loss in the nanoparticles.

  19. Modeling of two-phase magnetic materials based on Jiles-Atherton theory of hysteresis

    NASA Astrophysics Data System (ADS)

    Raghunathan, A.; Melikhov, Y.; Snyder, J. E.; Jiles, D. C.

    2012-01-01

    The Jiles-Atherton (JA) theory of hysteresis has been extended in the present paper to model hysteresis in two-phase magnetic materials. Two-phase materials are those that exhibit two magnetic phases in one hysteresis cycle: one at lower fields and the other at higher fields. In magnetic hysteresis, the transition from one phase to the other i.e. low field phase to high field phase depends mainly on the exchange field. Hence, the material-dependent microstructural parameters of JA theory: spontaneous magnetization, MS, pinning factor, k, domain density, a, domain coupling, α, and reversibility factor, c, are represented as functions of the exchange field. Several cases based on this model have been discussed and compared with the measured data from existing literature. The shapes of the calculated and measured hysteresis loops are in excellent agreement.

  20. The hysteresis-free negative capacitance field effect transistors using non-linear poly capacitance

    NASA Astrophysics Data System (ADS)

    Fan, S.-T.; Yan, J.-Y.; Lai, D.-C.; Liu, C. W.

    2016-08-01

    A gate structure design for negative capacitance field effect transistors (NCFETs) is proposed. The hysteresis loop in current-voltage performances is eliminated by the nonlinear C-V dependence of polysilicon in the gate dielectrics. Design considerations and optimizations to achieve the low SS and hysteresis-free transfer were elaborated. The effects of gate-to-source/drain overlap, channel length scaling, interface trap states and temperature impact on SS are also investigated.

  1. The application of the load-stroke hysteresis technique for evaluating fatigue damage development

    SciTech Connect

    Baxter, T.; Reifsnider, K.L.

    1994-12-31

    A new experimental method was developed to measure hysteresis loss during a fatigue test from the load and stroke signals of a standard servo-hydraulic materials testing system. The method was used to characterize changes in properties and performance induced by long-term cyclic loading. Advantages of the load-stroke hysteresis measurement include: (1) contact with the specimen is not required, (2) the fatigue test is not interrupted for data collection, (3) the measured quantity (the hysteresis loop area) is directly related to the (damage) events that alter material properties and life, and (4) a quantitative measure of damage extent and development rate is obtained. The method was used to evaluate damage development during fatigue tests of polymeric composite laminates with unidirectional and angle-ply fiber orientations. The hysteresis loop measurements were used to identify the different stages of damage development and the different damage mechanisms (matrix cracking, delamination, and fiber fracture) in the material systems. The results from the hysteresis technique were correlated with conventional NDE methods such as dynamic signal analysis and specimen surface temperature measurements. It was found that the load-stroke hysteresis technique was especially sensitive to the fiber fracture, the most difficult type of damage process to interrogate in-situ. The hysteresis technique may provide a valuable method for predicting fatigue failure in composite specimens.

  2. A theory of triple hysteresis in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Weng, George J.

    2009-10-01

    In the vicinity of the transition temperature between two ferroelectric states, a ferroelectric crystal could exhibit a triple hysteresis under an ac field. For a BaTiO3 with the "c-plate" configuration slightly below this temperature, the middle loop is caused by the 0°→180° domain switch in the orthorhombic phase, whereas the upper and lower loops are the result of orthorhombic-to-tetragonal phase transition, and vice versa. In this article we first develop a micromechanics-based thermodynamic model to determine the thermodynamic driving force for phase transition and for domain switch as a function of electric field and temperature, and in the latter case, further supplement it with a kinetic equation and a homogenization scheme. The dependence of dielectric constant of the orthorhombic and tetragonal phases on temperature and electric field are also established. The developed theory is then applied to calculate the triple hysteresis loops of BaTiO3 at several levels of temperature. The calculated results for the triple loops, and for the variation of dielectric constant, are found to be in full accord with the test data of Huibregtse and Young [Phys. Rev. 103, 1705 (1956)].

  3. 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.

  4. Nonlinear diffusion and superconducting hysteresis

    SciTech Connect

    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.

  5. 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.

  6. Disorder Identification in Hysteresis Data: Recognition Analysis of the Random-Bond-Random-Field Ising Model

    SciTech Connect

    Ovchinnikov, O. S.; Jesse, S.; Kalinin, S. V.; Bintacchit, P.; Trolier-McKinstry, S.

    2009-10-09

    An approach for the direct identification of disorder type and strength in physical systems based on recognition analysis of hysteresis loop shape is developed. A large number of theoretical examples uniformly distributed in the parameter space of the system is generated and is decorrelated using principal component analysis (PCA). The PCA components are used to train a feed-forward neural network using the model parameters as targets. The trained network is used to analyze hysteresis loops for the investigated system. The approach is demonstrated using a 2D random-bond-random-field Ising model, and polarization switching in polycrystalline ferroelectric capacitors.

  7. Understanding contact angle hysteresis on an ambient solid surface.

    PubMed

    Wang, Yong Jian; Guo, Shuo; Chen, Hsuan-Yi; Tong, Penger

    2016-05-01

    We report a systematic study of contact angle hysteresis (CAH) with direct measurement of the capillary force acting on a contact line formed on the surface of a long glass fiber intersecting a liquid-air interface. The glass fiber of diameter 1-2μm and length 100-200μm is glued onto the front end of a rectangular cantilever beam, which is used for atomic force microscopy. From the measured hysteresis loop of the capillary force for 28 different liquids with varying surface tensions and contact angles, we find a universal behavior of the unbalanced capillary force in the advancing and receding directions and the spring constant of a stretched meniscus by the glass fiber. Measurements of the capillary force and its fluctuations suggest that CAH on an ambient solid surface is caused primarily by two types of coexisting and spatially intertwined defects with opposite natures. The contact line is primarily pinned by the relatively nonwetting (repulsive) defects in the advancing direction and by the relatively wetting (attractive) defects in the receding direction. Based on the experimental observations, we propose a "composite model" of CAH and relevant scaling laws, which explain the basic features of the measured hysteresis force loops. PMID:27300959

  8. Understanding contact angle hysteresis on an ambient solid surface

    NASA Astrophysics Data System (ADS)

    Wang, Yong Jian; Guo, Shuo; Chen, Hsuan-Yi; Tong, Penger

    2016-05-01

    We report a systematic study of contact angle hysteresis (CAH) with direct measurement of the capillary force acting on a contact line formed on the surface of a long glass fiber intersecting a liquid-air interface. The glass fiber of diameter 1 -2 μ m and length 100 -200 μ m is glued onto the front end of a rectangular cantilever beam, which is used for atomic force microscopy. From the measured hysteresis loop of the capillary force for 28 different liquids with varying surface tensions and contact angles, we find a universal behavior of the unbalanced capillary force in the advancing and receding directions and the spring constant of a stretched meniscus by the glass fiber. Measurements of the capillary force and its fluctuations suggest that CAH on an ambient solid surface is caused primarily by two types of coexisting and spatially intertwined defects with opposite natures. The contact line is primarily pinned by the relatively nonwetting (repulsive) defects in the advancing direction and by the relatively wetting (attractive) defects in the receding direction. Based on the experimental observations, we propose a "composite model" of CAH and relevant scaling laws, which explain the basic features of the measured hysteresis force loops.

  9. 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.

  10. Hysteresis in quartz resonators-a review.

    PubMed

    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

  11. Criteria for saturated magnetization loop

    NASA Astrophysics Data System (ADS)

    Harres, A.; Mikhov, M.; Skumryev, V.; Andrade, A. M. H. de; Schmidt, J. E.; Geshev, J.

    2016-03-01

    Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe3O4 and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one.

  12. Contrasting diel hysteresis between soil autotrophic and heterotrophic respiration in a desert ecosystem under different rainfall scenarios

    PubMed Central

    Song, Weimin; Chen, Shiping; Zhou, Yadan; Wu, Bo; Zhu, Yajuan; Lu, Qi; Lin, Guanghui

    2015-01-01

    Diel hysteresis occurs often between soil CO2 efflux (RS) and temperature, yet, little is known if diel hysteresis occurs in the two components of RS, i.e., autotrophic respiration (RA) and heterotrophic respiration (RH), and how diel hysteresis will respond to future rainfall change. We conducted a field experiment in a desert ecosystem in northern China simulating five different scenarios of future rain regimes. Diel variations of soil CO2 efflux and soil temperature were measured on Day 6 and Day 16 following the rain addition treatments each month during the growing season. We found contrasting responses in the diel hysteresis of RA and RH to soil temperature, with a clockwise hysteresis loop for RH but a counter-clockwise hysteresis loop for RA. Rain addition significantly increased the magnitude of diel hysteresis for both RH and RA on Day 6, but had no influence on either on Day 16 when soil moisture was much lower. These findings underline the different roles of biological (i.e. plant and microbial activities) and physical-chemical (e.g. heat transport and inorganic CO2 exchange) processes in regulating the diel hysteresis of RA and RH, which should be considered when estimating soil CO2 efflux in desert regions under future rainfall regime. PMID:26615895

  13. Contrasting diel hysteresis between soil autotrophic and heterotrophic respiration in a desert ecosystem under different rainfall scenarios.

    PubMed

    Song, Weimin; Chen, Shiping; Zhou, Yadan; Wu, Bo; Zhu, Yajuan; Lu, Qi; Lin, Guanghui

    2015-01-01

    Diel hysteresis occurs often between soil CO2 efflux (R(S)) and temperature, yet, little is known if diel hysteresis occurs in the two components of R(S), i.e., autotrophic respiration (R(A)) and heterotrophic respiration (R(H)), and how diel hysteresis will respond to future rainfall change. We conducted a field experiment in a desert ecosystem in northern China simulating five different scenarios of future rain regimes. Diel variations of soil CO2 efflux and soil temperature were measured on Day 6 and Day 16 following the rain addition treatments each month during the growing season. We found contrasting responses in the diel hysteresis of R(A) and R(H) to soil temperature, with a clockwise hysteresis loop for R(H) but a counter-clockwise hysteresis loop for R(A). Rain addition significantly increased the magnitude of diel hysteresis for both R(H) and R(A) on Day 6, but had no influence on either on Day 16 when soil moisture was much lower. These findings underline the different roles of biological (i.e. plant and microbial activities) and physical-chemical (e.g. heat transport and inorganic CO2 exchange) processes in regulating the diel hysteresis of R(A) and R(H), which should be considered when estimating soil CO2 efflux in desert regions under future rainfall regime. PMID:26615895

  14. Fatigue Hysteresis of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-02-01

    When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress-strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress-strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress-strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established.

  15. Wetting hysteresis induced by nanodefects.

    PubMed

    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

  16. Wetting hysteresis induced by nanodefects

    PubMed Central

    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

  17. Magnetic hysteresis of p(+) and He-3(2+) irradiated melt-textured YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Song, S. N.; Liu, J.; Chen, I. G.; Weinstein, Roy

    1992-01-01

    We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O(7-delta) samples before and after p(+) and He-3(2+) irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper He-3(2+) fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence. After the irradiation, the best fit has been achieved by using an exponential form. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.

  18. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    SciTech Connect

    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.

  19. Rotational hysteresis of the exchange anisotropy direction in Co /FeMn thin films

    NASA Astrophysics Data System (ADS)

    Olamit, Justin; Liu, Kai

    2007-05-01

    The effects of rotating an applied field on the exchange anisotropy in Co /FeMn thin films have been investigated. When the applied field is initially along the cooling field direction, the longitudinal hysteresis loop has a maximum coercivity and the transverse hysteresis loop is flat, indicating that the exchange field is along the cooling field direction. When the applied field angle is rotated away and then restored to the original field cooling direction, the exchange anisotropy direction has changed. The rotation of the exchange field direction trails the applied field and is hysteretic. The rotational hysteresis of the exchange field direction is due to the weak anisotropy in thin FeMn layers and decreases with increasing FeMn thickness.

  20. 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 is a non-linear loop-like behavior that is common in natural systems. Hysteresis is common in the relation between streamflow and a number of other hydrologic variables, e.g., groundwater levels, soil moisture, extent of the saturated area, and sediment and solute concentrations. Analysis of these hysteretic patterns at the event time scale can lead to a better understanding of the processes underlying the catchment hydrological response. Hysteretic patterns can also be used for model calibration and testing. Several indexes have been developed to analyze hysteresis and quantify the direction and the extent of the loops, particularly to determine hysteresis in the relation between sediment concentrations and runoff. However, they typically suffer from a degree of subjectivity, do not take into account complex hysteretic patterns and are therefore not always applicable to describe other hysteretic relations as well. Therefore, we present a new versatile index for the quantification of a wide range hysteretic loops between hydrological variables at the runoff event timescale and test the sensitivity of the index to the temporal resolution of the measurement data and measurement errors. The conceptual development of the new hysteresis index is based on i) a normalization to compare hysteretic loops at different space- and timescales, and ii) the computation of the slopes of segments connecting the initial state to observations of the independent variable. The index provides information on the direction, the extent and the shape of the hysteretic loops. The index was tested with hydrological data from three experimental catchments in Northern Italy. Hysteretic relations between streamflow (the independent variable) and four different dependent variables (soil moisture, groundwater level, isotopic composition of stream water and electrical conductivity of stream water) were correctly identified and quantified by the index. The objective quantification of

  1. Modeling of hysteresis in magnetic multidomains

    NASA Astrophysics Data System (ADS)

    Cardelli, E.; Carpentieri, M.; Faba, A.; Finocchio, G.

    2014-02-01

    In this paper, the analysis of multi-domain nanostructures is made by means of numerical approaches. The Landau-Lifshitz-Gilbert LLG equation is used to compute the magnetic hysteresis loops for different alternate scalar polarizations. The data computed are then used to identify the parameters of a phenomenological model, based on the extension of the Preisach model in 2-D. The identification in this case is the evaluation of the size and the position of the hysterons in the H-plane. Each hysteron is associated to a domain of the nanostructure and the assembly of hysterons reproduces with satisfactory accuracy the hysteretic behavior of the nanostructure computed by the LLG equation with an extremely reduced computational time. Some possible relationships between the magnetization nanostructure and the parameters of the hysteron are suggested. These relationship should be used for a “blind” prediction of the magnetization state of much larger magnetic structures, whose computation using the LLG equation is not possible in practice due to the enormous computational time, supposing that magnetic structures with the same aspect ratio exhibit a similar distribution of magnetic domains. The theory is applied here to an example of Permalloy nanostructure.

  2. 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.

  3. Ionically-mediated electromechanical hysteresis in transition metal oxides

    SciTech Connect

    Kim, Yunseok; Kumar, Amit; Jesse, Stephen; Kalinin, Sergei V

    2012-01-01

    Electromechanical activity, remanent polarization states, and hysteresis loops in paraelectric TiO2 and SrTiO3 are observed. The coupling between the ionic dynamics and incipient ferroelectricity in these materials is analyzed using extended Ginsburg Landau Devonshire (GLD) theory. The possible origins of electromechanical coupling including ionic dynamics, surface-charge induced electrostriction, and ionically-induced ferroelectricity are identified. For the latter, the ionic contribution can change the sign of first order GLD expansion coefficient, rendering material effectively ferroelectric. These studies provide possible explanation for ferroelectric-like behavior in centrosymmetric transition metal oxides.

  4. 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.

  5. Regulative Loops, Step Loops and Task Loops

    ERIC Educational Resources Information Center

    VanLehn, Kurt

    2016-01-01

    This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, which…

  6. Hysteresis effects in suspended sediment concentration of an allogenic river channel in a very arid environment

    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.

  7. 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.

  8. 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.

  9. 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.

  10. Hysteresis in layered spring magnets.

    SciTech Connect

    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.

  11. 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.

  12. Parent Effectiveness Training (P.E.T.): Criticisms and Caveats.

    ERIC Educational Resources Information Center

    Doherty, William J.; Ryder, Robert G.

    1980-01-01

    Criticizes Parent Effectiveness Training (P.E.T.) for its emphasis on one-sided techniques in the parent-child relationship and its tendency to reduce complex problems to simplistic formulas. P.E.T.'s central metaphor of parent-as-therapist is identified and found wanting. Issues have applicability to the parent education movement in general.…

  13. MATHEMATICAL MODELS OF HYSTERESIS (DYNAMIC PROBLEMS IN HYSTERESIS)

    SciTech Connect

    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.

  14. 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.

  15. A neural network for incorporating the thermal effect on the magnetic hysteresis of the 3F3 material using the Jiles-Atherton model

    NASA Astrophysics Data System (ADS)

    Nouicer, A.; Nouicer, E.; Feliachi, Mouloud

    2015-01-01

    The present paper deals with the temperature dependent modeling approach for the generation of hysteresis loops of ferromagnetic materials. The physical model is developed to study the effect of temperature on the magnetic hysteresis loop using the Jiles-Atherton (J-A) model. The thermal effects were incorporated through temperature dependent hysteresis parameters of JA model. The temperature-dependent J-A model was validated by measurements made on the ferrite material. The results of proposed model were in good agreement with the measurements.

  16. 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.

  17. From the Cover: Hysteresis drives cell-cycle transitions in Xenopus laevis egg extracts

    NASA Astrophysics Data System (ADS)

    Sha, Wei; Moore, Jonathan; Chen, Katherine; Lassaletta, Antonio D.; Yi, Chung-Seon; Tyson, John J.; Sible, Jill C.

    2003-02-01

    Cells progressing through the cell cycle must commit irreversibly to mitosis without slipping back to interphase before properly segregating their chromosomes. A mathematical model of cell-cycle progression in cell-free egg extracts from frog predicts that irreversible transitions into and out of mitosis are driven by hysteresis in the molecular control system. Hysteresis refers to toggle-like switching behavior in a dynamical system. In the mathematical model, the toggle switch is created by positive feedback in the phosphorylation reactions controlling the activity of Cdc2, a protein kinase bound to its regulatory subunit, cyclin B. To determine whether hysteresis underlies entry into and exit from mitosis in cell-free egg extracts, we tested three predictions of the Novak-Tyson model. (i) The minimal concentration of cyclin B necessary to drive an interphase extract into mitosis is distinctly higher than the minimal concentration necessary to hold a mitotic extract in mitosis, evidence for hysteresis. (ii) Unreplicated DNA elevates the cyclin threshold for Cdc2 activation, indication that checkpoints operate by enlarging the hysteresis loop. (iii) A dramatic "slowing down" in the rate of Cdc2 activation is detected at concentrations of cyclin B marginally above the activation threshold. All three predictions were validated. These observations confirm hysteresis as the driving force for cell-cycle transitions into and out of mitosis.

  18. 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.

  19. Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at the nanoscale

    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.

  20. Hysteresis multicycles in nanomagnet arrays.

    PubMed

    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

  1. 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.

  2. Negative and positive hysteresis in double-cavity optical bistability in a three-level atom

    SciTech Connect

    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.

  3. Identification techniques for phenomenological models of hysteresis based on the conjugate gradient method

    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.

  4. Modeling of dynamic hysteresis for grain-oriented laminations using a viscosity-based modified dynamic Jiles-Atherton model

    NASA Astrophysics Data System (ADS)

    Baghel, A. P. S.; Shekhawat, S. K.; Kulkarni, S. V.; Samajdar, I.

    2014-09-01

    Grain-oriented (GO) materials exhibit arbitrary frequency-loss behaviors and anomalies in dynamic hysteresis loop shapes. Significant attempts have been made in the literature to approximate dynamic hysteresis loops using the dynamic Jiles-Atherton (JA) model based Bertotti's approach. Such a model is inefficient in accurate loss computation over a wide range of frequencies and in predictions of correct loop shapes. Moreover, the original static JA model also needs to be improved for accurate prediction of highly steep, gooseneck, and narrow-waist static loops of GO materials. An alternative approach based on magnetic viscosity provides flexibilities to handle indefinite frequency dependence of the losses and to control the anomalous loop shapes. This paper proposes a viscosity-based dynamic JA model which gives accurate prediction of dynamic loops of GO materials. A modified static JA model which considers crystalline and textured structures of GO materials is used to predict static hysteresis loops. The dynamic losses are included in the modified model using the field separation approach. The proposed model is validated using experimental measurements. The computed and measured dynamic loops are in close agreement in the frequency range of 1-200 Hz.

  5. Hysteresis modeling of the grain-oriented laminations with inclusion of crystalline and textured structure in a modified Jiles-Atherton model

    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.

  6. Effect of the exchange bias on the magnetization hysteresis of a ferromagnetic film in contact with an antiferromagnet

    NASA Astrophysics Data System (ADS)

    Grechnev, A. G.; Kovalev, A. S.; Pankratova, M. L.

    2013-12-01

    The transformation of the hysteretic field dependence of the magnetization of a ferromagnetic thin layer in contact with a magnetically hard antiferromagnet is considered. It is shown that this interaction leads to a shift of the hysteresis loop from the configuration symmetric with respect to magnetic field (exchange bias). Furthermore, upon increasing the magnitude of the exchange interaction, within a narrow range of the magnitudes, there occurs a qualitative change in the hysteresis loop shape and its subsequent disappearance; hence the field dependence of the magnetization becomes monotonous and single-valued.

  7. Corneal hysteresis and its relevance to glaucoma

    PubMed Central

    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

  8. Technical Note: Testing an improved index for analysing storm discharge-concentration hysteresis

    NASA Astrophysics Data System (ADS)

    Lloyd, C. E. M.; Freer, J. E.; Johnes, P. J.; Collins, A. L.

    2016-02-01

    Analysis of hydrochemical behaviour during storm events can provide new insights into the process controls on nutrient transport in catchments. The examination of storm behaviours using hysteresis analysis has increased in recent years, partly due to the increased availability of high temporal resolution data sets for discharge and water quality parameters. A number of these analyses involve the use of an index to describe the characteristics of a hysteresis loop in order to compare storm behaviours both within and between catchments. This technical note reviews the methods for calculation of the hysteresis index (HI) and explores a new more effective methodology. Each method is systematically tested and the impact of the chosen calculation on the results is examined. Recommendations are made regarding the most effective method of calculating a HI which can be used for comparing data between storms and between different water quality parameters and catchments.

  9. 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).

  10. A two-state hysteresis model from high-dimensional friction.

    PubMed

    Biswas, Saurabh; Chatterjee, Anindya

    2015-07-01

    In prior work (Biswas & Chatterjee 2014 Proc. R. Soc. A 470, 20130817 (doi:10.1098/rspa.2013.0817)), we developed a six-state hysteresis model from a high-dimensional frictional system. Here, we use a more intuitively appealing frictional system that resembles one studied earlier by Iwan. The basis functions now have simple analytical description. The number of states required decreases further, from six to the theoretical minimum of two. The number of fitted parameters is reduced by an order of magnitude, to just six. An explicit and faster numerical solution method is developed. Parameter fitting to match different specified hysteresis loops is demonstrated. In summary, a new two-state model of hysteresis is presented that is ready for practical implementation. Essential Matlab code is provided. PMID:26587279

  11. A two-state hysteresis model from high-dimensional friction

    PubMed Central

    Biswas, Saurabh; Chatterjee, Anindya

    2015-01-01

    In prior work (Biswas & Chatterjee 2014 Proc. R. Soc. A 470, 20130817 (doi:10.1098/rspa.2013.0817)), we developed a six-state hysteresis model from a high-dimensional frictional system. Here, we use a more intuitively appealing frictional system that resembles one studied earlier by Iwan. The basis functions now have simple analytical description. The number of states required decreases further, from six to the theoretical minimum of two. The number of fitted parameters is reduced by an order of magnitude, to just six. An explicit and faster numerical solution method is developed. Parameter fitting to match different specified hysteresis loops is demonstrated. In summary, a new two-state model of hysteresis is presented that is ready for practical implementation. Essential Matlab code is provided. PMID:26587279

  12. Hysteresis during contact angles measurement.

    PubMed

    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

  13. Adhesion hysteresis of silane coated microcantilevers

    SciTech Connect

    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.

  14. 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.

  15. Magnetic hysteresis in natural materials. [chondrites, lunar samples and terrestrial rocks

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.

    1973-01-01

    Magnetic hysteresis loops and the derived hysteresis ratios R sub H and R sub I are used to classify the various natural dilute magnetic materials. R sub I is the ratio of saturation isothermal remanence (I sub R) to saturation (I sub S) magnetization, and R sub H is the ratio of remanent coercive force (H sub R) to coercive force (H sub C). The R sub H and R sub I values depend on grain size, the characteristics of separate size modes in mixtures of grains of high and low coercivity, and the packing characteristics. Both R sub H and R sub I are affected by thermochemical alterations of the ferromagnetic fraction. Hysteresis loop constriction is observed in lunar samples, chondrite meteorites, and thermochemically altered basaltic rocks, and is due to mixtures of components of high and low coercivity. Discrete ranges of R sub H and R sub I for terrestrial and lunar samples and for chondrite meteorites provide for a classification of these natural materials based on their hysteresis properties.

  16. Equivalent Circuit Modeling of Hysteresis Motors

    SciTech Connect

    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.

  17. Free boundaries in problems with hysteresis

    PubMed Central

    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

  18. 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.

  19. Controller Parameter Tuning for Systems with Hysteresis and Its Application to Shape Memory Alloy Actuators

    NASA Astrophysics Data System (ADS)

    Wakasa, Yuji; Kanagawa, Shinji; Tanaka, Kanya; Nishimura, Yuki

    This paper proposes a simple controller parameter tuning method that can compensate for hysteresis. The proposed method is based on the so-called fictitious reference iterative tuning (FRIT) technique which can easily tune controller parameters such as proportional-integral-derivative gains using a one-shot closed-loop experimental data. In the proposed framework, a simple hysteresis model is introduced to a control system, and its inverse is used as a hysteresis compensator. Since the hysteresis model is characterized with only three parameters, the related computational burden is moderate in the parameter tuning process. Also, the proposed FRIT method needs an only one-shot experiment as in the standard FRIT one, which implies that the feature of FRIT is well-maintained. In the optimization process, the so-called covariance matrix adaptation evolution strategy is used for simultaneously searching hysteresis parameters as well as controller parameters. The proposed FRIT method is applied to an experimental control system that comprises a shape memory alloy actuator, and its effectiveness is verified.

  20. 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.

  1. 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.

  2. Noncontact evaluation of surface-modified materials by a model-assisted hysteresis measurement technique

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.

    2010-05-01

    This paper reports on a model-assisted magnetic hysteresis measurement method for noncontact characterization of surface-modified materials whose magnetic properties vary with depth. The technique involves measuring hysteresis loops from a test sample using a surface sensor probe in close proximity to the sample without any direct contact with it. The sensor outputs were simulated based on an extended magnetic hysteresis model to describe the magnetic hysteresis of the sample and its influence on the magnetic reluctance of the magnetic circuit. The technique was applied to characterize a series of surface hardened Fe-C samples with hardening depths ranging from 1.09 to 5.68 mm. The hysteresis behavior of the samples was modeled using a parametrized function to describe the depth profile of domain wall pinning strength. The midpoints of the inverted pinning strength profiles were found to agree with those of the measured hardness profiles, demonstrating the potential of the model-assisted technique for quantitative evaluation of surface-modified magnetic materials.

  3. Load-Dependent Friction Hysteresis on Graphene.

    PubMed

    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

  4. Disorder-driven first-order phase transformations: A model for hysteresis

    SciTech Connect

    Dahmen, K.; Kartha, S.; Krumhansl, J.A.; Roberts, B.W.; Sethna, J.P.; Shore, J.D. )

    1994-05-15

    Hysteresis loops in some magnetic systems are composed of small avalanches (manifesting themselves as Barkhausen pulses). Hysteresis loops in other first-order phase transitions (including some magnetic systems) often occur via one large avalanche. The transition between these two limiting cases is studied, by varying the disorder in the zero-temperature random-field Ising model. Sweeping the external field through zero at weak disorder, we get one large avalanche with small precursors and aftershocks. At strong disorder, we get a distribution of small avalanches (small Barkhausen effect). At the critical value of disorder where a macroscopic jump in the magnetization first occurs, universal power-law behavior of the magnetization and of the distribution of (Barkhausen) avalanches is found. This transition is studied by mean-field theory, perturbative expansions, and numerical simulation in three dimensions.

  5. The influence of laminar separation and transition on low Reynolds number airfoil hysteresis

    NASA Technical Reports Server (NTRS)

    Mueller, T. J.

    1984-01-01

    An experimental study of the Lissaman 7769 and Miley MO6-13-128 airfoils at low chord Reynolds numbers is presented. Although both airfoils perform well near their design Reynolds number of about 600,000, they each produce a different type of hysteresis loop in the lift and drag forces when operated below chord Reynolds numbers of 300,000. The type of hysteresis loop was found to depend upon the relative location of laminar separation and transition. The influence of disturbance environment and experimental procedure on the low Reynolds number airfoil boundary layer behavior is also presented. The use of potential flow solutions to help predict how a given airfoil will behave at low Reynolds numbers is also discussed.

  6. Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions

    NASA Astrophysics Data System (ADS)

    Shalev, Eyal; Lyakhovsky, Vladimir; Ougier-Simonin, Audrey; Hamiel, Yariv; Zhu, Wenlu

    2014-05-01

    Sandstones display non-linear and inelastic behaviour such as hysteresis when subjected to cyclic loading. We present three hydrostatic compaction experiments with multiple loading-unloading cycles on Berea and Darley Dale sandstones and explain their hysteretic behaviour using non-linear inelastic compaction and dilation. Each experiment included eight to nine loading-unloading cycles with increasing maximum pressure in each subsequent cycle. Different pressure-volumetric strain relations during loading and unloading were observed. During the first cycles, under relatively low pressures, not all of the volumetric strain is recovered at the end of each cycle whereas at the last cycles, under relatively high pressures, the strain is recovered and the pressure-volumetric strain hysteresis loops are closed. The observed pressure-volumetric strain relations are non-linear and the effective bulk modulus of the sandstones changes between cycles. Observations are modelled with two inelastic deformation processes: irreversible compaction caused by changes in grain packing and recoverable compaction associated with grain contact adhesion, frictional sliding on grains or frictional sliding on cracks. The irreversible compaction is suggested to reflect rearrangement of grains into a more compact mode as the maximum pressure increases. Our model describes the `inelastic compaction envelope' in which sandstone sample will follow during hydrostatic loading. Irreversible compaction occurs when pressure is greater than a threshold value defined by the `inelastic compaction envelope'.

  7. Transport, hysteresis and avalanches in artificial spin ice systems

    SciTech Connect

    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.

  8. Modelling of microstructural effects on magnetic hysteresis properties

    NASA Astrophysics Data System (ADS)

    Dupré, L.; Sablik, M. J.; Van Keer, R.; Melkebeek, J.

    2002-09-01

    In this paper, the relationship between microstructural properties of steels and the material parameters in the Preisach model and in the Jiles-Atherton (JA) model is discussed, in the instance where both models describe quasi-static hysteretic magnetic behaviour. It is shown how the material parameters in both hysteresis models should be modified to reflect their dependence on dislocation density and grain size. The dependence of the Preisach material parameters on these microstructural features is identified starting from hysteresis loops calculated by the microstructurally dependent modified JA model. For the Preisach model, a Lorentzian distribution function is used for the distribution function. This makes it possible to compare predictions here to results of an earlier paper in which the Lorentzian distribution was used for Preisach fits to experimental data for steels of different grain sizes. Also, in a different earlier paper, it was shown how the Lorentzian distribution can be formulated so that it connects with salient features of the JA model. The procedure in this paper enables one to examine and predict microstructural variations of Preisach parameters in steels not only for the case of grain size variation but also for the case of variation in dislocation density.

  9. 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

  10. 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.

  11. Dynamical analysis to the levitated systems of high temperature superconductors with hysteresis

    NASA Astrophysics Data System (ADS)

    Zhou, You-He; Zhao, Xian-Feng

    2006-08-01

    Dynamic behavior and penetration history of shielding currents distribution associated with the hysteresis of magnetic levitation force are investigated to the vertically mechanical oscillation of a permanent magnet (PM) which is magnetically levitated over a YBCO superconductor based on Bean’s critical-state model and Ampére circulation theorem. After the shielding current distribution is analytically derived out from the Maxwell’s equations of the electromagnetic system to each monotonic procedure of the hysteresis, the dynamic differential equation of the levitation is solved to the damped free vibration of the system using the adaptive Runge-Kutta approach of order 4. The obtained results display that the partially wiping-out phenomenon of shielding currents always happens in the interior of the superconductor such that the PM experiences a damped vibration. It is found that the damping generated from the hysteresis in the superconductor is time-changeable in the whole response, and that the frequency of vibration or magnetic stiffness increases with time during the first four periods of the response, as well as that the maximum penetration depth, δp, of the shielding currents at the end of each procedure of the hysteresis decays with time or turning number, Ntur, i.e., δp=e where α0 and α1 are the fitting coefficients.

  12. Formative Assessment Probes: Using the P-E-O Technique

    ERIC Educational Resources Information Center

    Keeley, Page

    2013-01-01

    This article describes how observing whether objects sink or float in water using the P-E-O (Predict, Explain, and Observe) technique is an elementary precursor to developing explanations in later grades that involve an understanding of density and buoyancy. Beginning as early as preschool, elementary students engage in activities that encourage…

  13. A GCMC simulation and experimental study of krypton adsorption/desorption hysteresis on a graphite surface.

    PubMed

    Prasetyo, Luisa; Horikawa, Toshihide; Phadungbut, Poomiwat; Johnathan Tan, Shiliang; Do, D D; Nicholson, D

    2016-09-15

    Adsorption isotherms and isosteric heats of krypton on a highly graphitized carbon black, Carbopack F, have been studied with a combination of Monte Carlo simulation and high-resolution experiments at 77K and 87K. Our investigation sheds light on the microscopic origin of the experimentally observed, horizontal hysteresis loop in the first layer, and the vertical hysteresis-loop in the second layer, and is found to be in agreement with our recent Monte Carlo simulation study (Diao et al., 2015). From detailed analysis of the adsorption isotherm, the latter is attributed to the compression of an imperfect solid-like state in the first layer, to form a hexagonally packed, solid-like state, immediately following the first order condensation of the second layer. To ensure that capillary condensation in the confined spaces between microcrystallites of Carbopack F does not interfere with these hysteresis loops, we carried out simulations of krypton adsorption in the confined space of a wedge-shaped pore that mimics the interstices between particles. These simulations show that, up to the third layer, any such interference is negligible. PMID:27343464

  14. 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.

  15. Modeling mixed clockwise and counter-clockwise hysteresis in multi-layer materials by using a generalized Jiles-Atherton model

    NASA Astrophysics Data System (ADS)

    Andrei, Petru; Mehta, Mohit; Dimian, Mihai

    2014-02-01

    A generalized Jiles-Atherton model is proposed to describe mixed clockwise and counter-clockwise hysteresis loops. While it is physically inconsistent for homogeneous magnetic materials, this mixed type of hysteresis is exhibited by several multi-layer and superlattice materials with antiferromagnetic coupling. The modeling approach is based on a newly developed clockwise hysteretic model using the Jiles-Atherton framework and its linear superposition to the classical counter-clockwise version. The resulting technique is implemented in open-access academic software for hysteresis and simulation samples are presented in the paper.

  16. Negative hysteresis effect observed during calibration of the US Bureau of Mines borehole deformation gauge

    SciTech Connect

    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.

  17. Contribution of opening and closing of lung units to lung hysteresis.

    PubMed

    Cheng, W; DeLong, D S; Franz, G N; Petsonk, E L; Frazer, D G

    1995-12-01

    The recruitment and derecruitment of lung units is one explanation of the hysteresis observed in an excised lung during inflation and deflation. A simplified model has been proposed in which the recruitment-derecruitment process is a function of end-expiratory pressure (Frazer, D.G., K.C. Weber and G.N. Franz, Respir. Physiol. 61: 277-288, 1985). The object of this study was to test this model with three experimental procedures. During the first set of experiments, progressively larger pressure-volume (PL-VL) loops were recorded with end-expiratory pressure held at either -5 cmH2O, where all lung units are assumed to be closed, or +5 cmH2O, where all recruited lung units are assumed to be open. In the first case hysteresis is maximal, in the second, minimal. The difference in hysteresis is presumed to arise from the recruitment-derecruitment process. In the second set of experiments, excised lungs are slowly inflated and then deflated at a constant rate while constant-amplitude sinusoidal volume oscillations are superimposed. The end-expiratory pressure of the superimposed loops gradually rose as the lung was inflated and fell as the lung was deflated. Hysteresis was minimal when end-expiratory pressure was above 4 +/- 1 cmH2O even as peak-to-peak loop pressure greatly varied. This supports the notion of an end-expiratory pressure dependent mechanism of recruitment/derecruitment. During the third set of experiments lungs were inflated to either 50%, 75%, or 100% TLC. Volumes of air were then withdrawn and replaced so that the initial volume was restored in sinusoidal fashion as the amplitude of the volume excursions increased. For PL-VL loops with end-expiratory pressures between +4 and -2 cmH2O, pressure amplitudes rose and the hysteresis index (loop area/tidal volume) increased, regardless of the initial lung volume. These results are consistent with the previously described model of Frazer et al. (1985) which assumed that PL-VL curves can be divided into an

  18. Geometric hysteresis of alveolated ductal architecture.

    PubMed

    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

  19. Hysteresis and the length dependence of calcium sensitivity in chemically skinned rat cardiac muscle.

    PubMed Central

    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

  20. Hysteresis modeling in graphene field effect transistors

    SciTech Connect

    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.

  1. Origin of plate tectonics: Grain-damage, inheritance and hysteresis

    NASA Astrophysics Data System (ADS)

    Bercovici, D.; Ricard, Y. R.

    2015-12-01

    The emergence of plate tectonics is enigmatic because of the lack of observations in the early Archean as well as the challenge of understanding how plates form. The damage theory of lithospheric weakening by grain-reduction provides a physical framework for plate generation. This model builds on grain-scale physics to describe planetary-scale processes, and is consistent with lab and field observations of polycrystalline rocks and lithospheric mylonites. Grain-damage accounts for the evolution of damage and healing by grain growth, hence predicts plate boundary formation and longevity, and how they depend on surface conditions. The establishment of global plate tectonics likely started between >4Ga and 2.7Ga, and may have taken over a billion years to develop. Under Earth-like conditions, grain-damage combined with intermittent Archean protosubduction produces persistent weak zones that accumulate into well developed plates by 3Ga. However, Venus' hotter surface promotes healing, suppresses damage and inhibits weak zone accumulation, which suggests why plate tectonics failed to spread on our sister planet. New work posits that interface damage is possibly suppressed at moderate grain-size; this induces a hysteresis loop wherein three equilibrium deformation branches coexist. These branches include a stable large-grain, weakly-deforming state in dislocation creep, a stable small-grain rapidly-deforming state in diffusion creep analogous to mylonites, and an unstable intermediate-grain state. At the right conditions, a lithosphere can acquire two stable deformation states characteristic of plate tectonics; i.e., both slowly deforming plate interiors and rapidly deforming plate boundaries can co-exist. Earth currently sits inside the hysteresis loop and can have coexisting deformation states, while Venus sits at the end of the loop where only the weakly deforming branch dominates. The hot post-Hadean Earth might have had peak deformation only on the weakly

  2. Hysteresis compensation of the piezoelectric ceramic actuators-based tip/tilt mirror with a neural network method in adaptive optics

    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.

  3. Tracking control of shape-memory-alloy actuators based on self-sensing feedback and inverse hysteresis compensation.

    PubMed

    Liu, Shu-Hung; Huang, Tse-Shih; Yen, Jia-Yush

    2010-01-01

    Shape memory alloys (SMAs) offer a high power-to-weight ratio, large recovery strain, and low driving voltages, and have thus attracted considerable research attention. The difficulty of controlling SMA actuators arises from their highly nonlinear hysteresis and temperature dependence. This paper describes a combination of self-sensing and model-based control, where the model includes both the major and minor hysteresis loops as well as the thermodynamics effects. The self-sensing algorithm uses only the power width modulation (PWM) signal and requires no heavy equipment. The method can achieve high-accuracy servo control and is especially suitable for miniaturized applications. PMID:22315530

  4. A Jiles-Atherton and fixed-point combined technique for time periodic magnetic field problems with hysteresis

    SciTech Connect

    Chiampi, M.; Repetto, M.; Chiarabaglio, D.

    1995-11-01

    The hysteresis phenomenon can significantly affect the behavior of magnetic cores in electrical machines and devices. This paper presents a finite element solution of periodic steady state magnetic field problems in soft materials with scalar hysteresis. The Jiles-Atherton model is employed for the generation of symmetric B-H loops and it is coupled with the Fixed Point Technique for handling magnetic nonlinearities. The proposed procedure is applied to a hysteretic model problem whose analytical solution is available. The results show that the Fixed Point Technique can efficiently deal with non-single valued material characteristics under periodic operating conditions.

  5. Tracking Control of Shape-Memory-Alloy Actuators Based on Self-Sensing Feedback and Inverse Hysteresis Compensation

    PubMed Central

    Liu, Shu-Hung; Huang, Tse-Shih; Yen, Jia-Yush

    2010-01-01

    Shape memory alloys (SMAs) offer a high power-to-weight ratio, large recovery strain, and low driving voltages, and have thus attracted considerable research attention. The difficulty of controlling SMA actuators arises from their highly nonlinear hysteresis and temperature dependence. This paper describes a combination of self-sensing and model-based control, where the model includes both the major and minor hysteresis loops as well as the thermodynamics effects. The self-sensing algorithm uses only the power width modulation (PWM) signal and requires no heavy equipment. The method can achieve high-accuracy servo control and is especially suitable for miniaturized applications. PMID:22315530

  6. Naturally Produced Co/CoO Nanocrystalline Magnetic Multilayers: Structure and Inverted Hysteresis.

    PubMed

    Santarossa, Francesca; Pappas, Spiridon D; Delimitis, Andreas; Sousanis, Andreas; Poulopoulos, Panagiotis

    2016-05-01

    Cobalt-based multilayers with excellent sequencing are grown via radiofrequency magnetron sputtering with the use of one Co target and natural oxidation. The Co layers are continuous, fully textured {111} and have the face centered cubic structure. At the end of deposition of each Co layer air is let to flow into the vacuum chamber via a fine (leak) valve. The top of Co is oxidized. The oxidized layers consist of cubic CoO crystallites. Near the film surface hexagonal Co(OH)2 is also detected. Magneto-optical Kerr effect hysteresis loops show in-plane magnetized films. The magnetic saturation field in the out-of-plane measurements is large exceeding 12 kOe. This observation supports indirectly the fact that Co is face centered cubic; if it was c-axis textured hexagonal the magnetocrystalline anisotropy would be large resulting in smaller values of the saturation field. As the Co-layer thickness decreases the in-plane loops show reduced remanence, slow approach to magnetic saturation and the out-of-plane loops show inverted hysteresis and/or crossing loop features with sizeable remanence. The effects are discussed with respect to the enhanced orbital magnetic moment of Co and the antiferromagnetic coupling between Co spins at the Co/CoO interface. PMID:27483852

  7. 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…

  8. 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.

  9. 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.

  10. 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.

  11. Macroscopic theory for capillary-pressure hysteresis.

    PubMed

    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

  12. Performance Calculation of High Temperature Superconducting Hysteresis Motor Using Finite Element Method

    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.

  13. 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.

  14. Damage Monitoring of Unidirectional C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading using A Hysteresis Loss Energy-Based Damage Parameter at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    The damage evolution of unidirectional C/SiC ceramic-matrix composite (CMC) under cyclic fatigue loading has been investigated using a hysteresis loss energy-based damage parameter at room and elevated temperatures. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy versus cycle number have been analyzed. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different cycle number and peak stress has been estimated. The experimental evolution of fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter versus cycle number has been predicted for unidirectional C/SiC composite at room and elevated temperatures. The predicted results of interface shear stress degradation, stress-strain hysteresis loops corresponding to different number of applied cycles, fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter as a functions of cycle number agreed with experimental data. It was found that the fatigue hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.

  15. Damage Monitoring of Unidirectional C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading using A Hysteresis Loss Energy-Based Damage Parameter at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-06-01

    The damage evolution of unidirectional C/SiC ceramic-matrix composite (CMC) under cyclic fatigue loading has been investigated using a hysteresis loss energy-based damage parameter at room and elevated temperatures. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy versus cycle number have been analyzed. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different cycle number and peak stress has been estimated. The experimental evolution of fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter versus cycle number has been predicted for unidirectional C/SiC composite at room and elevated temperatures. The predicted results of interface shear stress degradation, stress-strain hysteresis loops corresponding to different number of applied cycles, fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter as a functions of cycle number agreed with experimental data. It was found that the fatigue hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.

  16. 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.

  17. 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.

  18. A guided enquiry approach to introduce basic concepts concerning magnetic hysteresis to minimize student misconceptions

    NASA Astrophysics Data System (ADS)

    Wei, Yajun; Zhai, Zhaohui; Gunnarsson, Klas; Svedlindh, Peter

    2014-11-01

    Basic concepts concerning magnetic hysteresis are of vital importance in understanding magnetic materials. However, these concepts are often misinterpreted by many students and even textbooks. We summarize the most common misconceptions and present a new approach to help clarify these misconceptions and enhance students’ understanding of the hysteresis loop. In this approach, students are required to perform an experiment and plot the measured magnetization values and thereby calculated demagnetizing field, internal field, and magnetic induction as functions of the applied field point by point on the same graph. The concepts of the various coercivity, remanence, saturation magnetization, and saturation induction will not be introduced until this stage. By plotting this graph, students are able to interlink all the preceding concepts and intuitively visualize the underlying physical relations between them.

  19. Characterizing piezoscanner hysteresis and creep using optical levers and a reference nanopositioning stage

    SciTech Connect

    Xie, H.; Regnier, S.

    2009-04-15

    A method using atomic force microscope (AFM) optical levers and a reference nanopositioning stage has been developed to characterize piezoscanner hysteresis and creep. The piezoscanner is fixed on a closed-loop nanopositioning stage, both of which have the same arrangement on each axis of the three spatial directions inside the AFM-based nanomanipulation system. In order to achieve characterization, the optical lever is used as a displacement sensor to measure the relative movement between the nanopositioning stage and the piezoscanner by lateral tracking a well-defined slope with the tapping mode of the AFM cantilever. This setup can be used to estimate a piezoscanner's voltage input with a reference displacement from the nanopositioning stage. The hysteresis and creep were accurately calibrated by the method presented, which use the current setup of the AFM-based nanomanipulation system without any modification or additional devices.

  20. Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape

    NASA Astrophysics Data System (ADS)

    Syrenova, Svetlana; Wadell, Carl; Nugroho, Ferry A. A.; Gschneidtner, Tina A.; Diaz Fernandez, Yuri A.; Nalin, Giammarco; Świtlik, Dominika; Westerlund, Fredrik; Antosiewicz, Tomasz J.; Zhdanov, Vladimir P.; Moth-Poulsen, Kasper; Langhammer, Christoph

    2015-12-01

    Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that hydride decomposition either occurs incoherently or via different kinetic pathways.

  1. 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).

  2. Angular dependence of hysteresis shift in oblique deposited ferromagnetic/antiferromagnetic coupled bilayers

    NASA Astrophysics Data System (ADS)

    Oliveira, A. B.; Rodriguez-Suarez, R. L.; Michea, S.; Vega, H.; Azevedo, A.; Rezende, S. M.; Aliaga, C.; Denardin, J.

    2014-07-01

    The angular dependence of the hysteresis shift has been investigated in ferromagnetic/antiferromagnetic (NiFe/IrMn) bilayers grown by oblique deposition under the influence of a static magnetic field applied perpendicular to the uniaxial anisotropy direction induced during the growth process. It was found that at low oblique deposition angles, the unidirectional anisotropy field is much greater than the uniaxial anisotropy field and the corresponding anisotropies directions are noncollinear. In these conditions, the angular dependence of the hysteresis loop shift exhibits the well know cosine like shape but demanding a phase shift. Contrary to this, at high oblique deposition angle (70°), the uniaxial anisotropy plays the fundamental role and the anisotropies directions are collinear. In this case, the exchange bias displays a jump phenomenon. The numerical calculations are consistent with the experimental data obtained from magneto-optical Kerr effect and ferromagnetic resonance.

  3. Robust adaptive tracking control of MIMO nonlinear systems in the presence of actuator hysteresis

    NASA Astrophysics Data System (ADS)

    Fu, Guiyuan; Ou, Linlin; Zhang, Weidong

    2016-07-01

    Adaptive tracking control of a class of MIMO nonlinear system preceded by unknown hysteresis is investigated. Based on dynamic surface control, an adaptive robust control law is developed and compensators are designed to mitigate the influences of both the unknown bounded external uncertainties and the unknown Prandtl-Islinskii hysteresis. By adopting the low-pass filters, the explosion of complexity caused by tedious computation of the time derivatives of the virtual control laws is overcome. With the proposed control scheme, the closed-loop system is proved to be semi-globally ultimately bounded by the Lyapunov stability theory, and the output of the controlled system can track the desired trajectories with an arbitrarily small error. Finally, numerical simulations are given to verify the effectiveness of the proposed approach.

  4. Soft x-ray magneto-optic Kerr rotation and element-specific hysteresis measurement

    SciTech Connect

    Kortright, J.B.; Rice, M.

    1996-03-01

    Soft x-ray magneto-optic Kerr rotation has been measured using a continuously tunable multilayer linear polarizer in the beam reflected form samples in applied magnetic fields. Like magnetic circular dichroism, Kerr rotation in the soft x-ray can be element - specific and much larger than in the visible spectral range when the photon energy is tuned near atomic core resonances. Thus sensitive element-specific hysteresis measurements are possible with this technique. Examples showing large Kerr rotation from an Fe film and element-specific hysteresis loops of the Fe and Cr in an Fe/Cr multilayer demonstrate these new capabilities. Some consequences of the strong anomalous dispersion near the FeL{sub 2,3} edges to the Kerr rotation are discussed.

  5. Neural Controller Design-Based Adaptive Control for Nonlinear MIMO Systems With Unknown Hysteresis Inputs.

    PubMed

    Liu, Yan-Jun; Tong, Shaocheng; Chen, C L Philip; Li, Dong-Juan

    2016-01-01

    This paper studies an adaptive neural control for nonlinear multiple-input multiple-output systems in interconnected form. The studied systems are composed of N subsystems in pure feedback structure and the interconnection terms are contained in every equation of each subsystem. Moreover, the studied systems consider the effects of Prandtl-Ishlinskii (PI) hysteresis model. It is for the first time to study the control problem for such a class of systems. In addition, the proposed scheme removes an important assumption imposed on the previous works that the bounds of the parameters in PI hysteresis are known. The radial basis functions neural networks are employed to approximate unknown functions. The adaptation laws and the controllers are designed by employing the backstepping technique. The closed-loop system can be proven to be stable by using Lyapunov theorem. A simulation example is studied to validate the effectiveness of the scheme. PMID:25898325

  6. Tracking control of piezoelectric actuators using a polynomial-based hysteresis model

    NASA Astrophysics Data System (ADS)

    Gan, Jinqiang; Zhang, Xianmin; Wu, Heng

    2016-06-01

    A polynomial-based hysteresis model that describes hysteresis behavior in piezoelectric actuators is presented. The polynomial-based model is validated by comparing with the classic Prandtl-Ishlinskii model. Taking the advantages of the proposed model into consideration, inverse control using the polynomial-based model is proposed. To achieve better tracking performance, a hybrid control combining the developed inverse control and a proportional-integral-differential feedback loop is then proposed. To demonstrate the effectiveness of the proposed tracking controls, several comparative experiments of the polynomial-based model and Prandtl-Ishlinskii model are conducted. The experimental results show that inverse control and hybrid control using the polynomial-based model in trajectory-tracking applications are effective and meaningful.

  7. Evaluation technique for plasma-induced SiOC dielectric damage by capacitance–voltage hysteresis monitoring

    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.

  8. Grain-damage hysteresis and plate tectonic states

    NASA Astrophysics Data System (ADS)

    Bercovici, David; Ricard, Yanick

    2016-04-01

    deforms at a given stress can acquire two stable deformation regimes indicative of plate-like flows, i.e., it permits the coexistence of both slowly deforming plate interiors, and rapidly deforming plate boundaries. Earth seems to exist squarely inside the hysteresis loop and thus can have coexisting deformation states, while Venus appears to straddle the end of the loop where only the weakly deforming branch exists.

  9. [Mathematical models of hysteresis]. Progress report No. 4, [January 1, 1991--December 31, 1991

    SciTech Connect

    Mayergoyz, I.D.

    1991-12-31

    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.

  10. 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.

  11. Electroosmotic flow hysteresis for dissimilar ionic solutions.

    PubMed

    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

  12. Electroosmotic flow hysteresis for dissimilar ionic solutions

    PubMed Central

    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

  13. Hysteresis in the behavior of a long periodically modulated Josephson junction in a magnetic field for not small values of the pinning parameter

    NASA Astrophysics Data System (ADS)

    Zelikman, M. A.

    2016-03-01

    The magnetization curve for a long periodically modulated Josephson junction is calculated using the approach based on analysis of the continuous change in the configuration in the direction of the decrease in the Gibbs potential upon cyclic variation of the external magnetic field for not small values of pinning parameter I. It is shown that unlike in the case of small I, when the hysteresis loop is a part of a certain universal curve, the segments of the loops corresponding to a decrease in h in the first and second quadrants (and symmetric to them) pass below the universal loop, the degree of deviation increasing with pinning parameter I. The properties of the hysteresis loops are considered for various amplitudes of the magnetic field variation on the basis of analysis of vortex configurations.

  14. Effects of matching network on the hysteresis during E and H mode transitions in argon inductively coupled plasma

    SciTech Connect

    Gao Fei; Zhao Shuxia; Li Xiaosong; Wang Younian

    2010-10-15

    An experimental investigation of the hysteresis during the E (capacitive coupling) and H mode (inductive coupling) transitions at various matching situation in argon inductively coupled plasma is reported. At high pressure, the results show two hysteresis loops involved the plasma density, applied power, and forward power, as well as the electrical parameters in the discharge circuit, when the series capacitance is cycled. The measured electron density versus applied power shows that the hysteresis loop shrinks with the decrease of the matching capacitance, and the same trend is discovered on the input current, voltage, and phase angle. In addition, for the case of small capacitance, the current (or voltage) jumps to a low value when the discharge passes through the E to H mode transition regime. Contrarily, for the case of large capacitance, the current jumps to a high value while the voltage is almost constant. The evolution characteristics of the plasma and circuit parameters observed imply that the nonlinear behavior of the matching situation may be one of the determined factors for hysteresis.

  15. Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at nanoscale

    DOE PAGESBeta

    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

  16. Loop-to-loop coupling.

    SciTech Connect

    Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald

    2012-05-01

    This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

  17. Protonated polynucleotides structures - 23. The acid-base hysteresis of poly(dG).poly(dC).

    PubMed Central

    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

  18. Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Hernández-Gómez, P.; Muñoz, J. M.; Valente, M. A.; Torres, C.; de Francisco, C.

    2013-01-01

    Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer's formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

  19. Avalanches and hysteresis in frustrated superconductors and XY spin glasses.

    PubMed

    Sharma, Auditya; Andreanov, Alexei; Müller, Markus

    2014-10-01

    We study avalanches along the hysteresis loop of long-range interacting spin glasses with continuous XY symmetry, which serves as a toy model of granular superconductors with long-range and frustrated Josephson couplings. We identify sudden jumps in the T=0 configurations of the XY phases as an external field is increased. They are initiated by the softest mode of the inverse susceptibility matrix becoming unstable, which induces an avalanche of phase updates (or spin alignments). We analyze the statistics of these events and study the correlation between the nonlinear avalanches and the soft mode that initiates them. We find that the avalanches follow the directions of a small fraction of the softest modes of the inverse susceptibility matrix, similarly as was found in avalanches in jammed systems. In contrast to the similar Ising spin glass (Sherrington-Kirkpatrick) studied previously, we find that avalanches are not distributed with a scale-free power law but rather have a typical size which scales with the system size. We also observe that the Hessians of the spin-glass minima are not part of standard random matrix ensembles as the lowest eigenvector has a fractal support. PMID:25375434

  20. Magnetization and Hysteresis of Dilute Magnetic-Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Skomski, Ralph; Balamurugan, B.; Sellmyer, D. J.

    2014-03-01

    Real-structure imperfections in dilute magnetic oxides tend to create small concentrations of local magnetic moments that are coupled by fairly long-range exchange interactions, mediated by p-electrons. The robustness of these interactions is caused by the strong overlap of the p orbitals, as contrasted to the much weaker interatomic exchange involving iron-series 3d electrons. The net exchange between defect moments can be positive or negative, which gives rise to spin structures with very small net moments. Similarly, the moments exhibit magnetocrystalline anisotropy, reinforced by electron hopping to and from 3d states and generally undergoing some random-anuisotropy averaging. Since the coercivity scales as 2K1/M and M is small, this creates pronounced and -- in thin films -- strongly anisotropic hysteresis loops. In finite systems with N moments, both K1 and M are reduced by a factor of order N1/2 due to random anisotropy and moment compensation, respectively, so that that typical coercivities are comparable to bulk magnets. Thermal activation readily randomizes the net moment of small oxide particles, so that the moment is easier to measure in compacted or aggregated particle ensembles. This research is supported by DOE (BES).

  1. Quantum oscillations and ferromagnetic hysteresis observed in iron filled multiwall carbon nanotubes.

    PubMed

    Barzola-Quiquia, J; Klingner, N; Krüger, J; Molle, A; Esquinazi, P; Leonhardt, A; Martínez, M T

    2012-01-13

    We report on the electrical transport properties of single multiwall carbon nanotubes with and without an iron filling as a function of temperature and magnetic field. For the iron filled nanotubes the magnetoresistance shows a magnetic behavior induced by iron, which can be explained by taking into account a contribution of s-d hybridization. In particular, ferromagnetic-like hysteresis loops were observed up to 50 K for the iron filled multiwall carbon nanotubes. The magnetoresistance shows quantum interference phenomena such as universal conductance fluctuations and weak localization effects. PMID:22155967

  2. Stability of dithered non-linear systems with backlash or hysteresis

    NASA Technical Reports Server (NTRS)

    Desoer, C. A.; Shahruz, S. M.

    1986-01-01

    A study is conducted of the effect of dither on the nonlinear element of a single-input single-outout feedback system. Nonlinearities are considered with memory (backlash, hysteresis), in the feedforward loop; a dither of a given amplitude is injected at the input of the nonlinearity. The nonlinearity is followed by a linear element with low-pass characteristic. The stability of the dithered system and an approximate equivalent system (in which the nonlinearity is a smooth function) are compared. Conditions on the input and on the dither frequency are obtained so that the approximate-system stability guarantees that of the given hysteretic system.

  3. Hysteresis in particulate recording media. Experiment and simulation with Preisach and Jiles-Atherton models

    NASA Astrophysics Data System (ADS)

    Andrei, Petru; Stancu, Alexandru

    1999-12-01

    In order to describe the magnetisation processes in particulate media some new variants for the Jiles-Atherton model are developed. The differences between these models and the Preisach model are discussed. Due to the analogy between the parameters of the two model's, the Jiles-Atherton model's parameters may be determined using the Preisach model's identification methods. A good agreement between the simulated and the measured data is observed for the major hysteresis loop but it is no longer good for some more complex magnetisation processes.

  4. A theoretical study of the hysteresis behaviors of a transverse spin-1/2 Ising nanocube

    NASA Astrophysics Data System (ADS)

    El Hamri, M.; Bouhou, S.; Essaoudi, I.; Ainane, A.; Ahuja, R.

    2016-09-01

    The applied magnetic field dependencies of the surface shell, core and total magnetizations of a transverse spin-1/2 Ising nanocube are investigated within the effective-field theory with correlations, based on the probability distribution technique, for both ferro- and antiferromagnetic exchange interactions. We have found that interfacial coupling has a strong effect on the shape and the number of hysteresis loops and also on the coercive field and remanent magnetization behaviors. Furthermore, when the temperature exceeds a critical one, the coercivities of the core, the surface shell and the system become zero.

  5. Nonlinear space charge dynamics in mixed ionic-electronic conductors: Resistive switching and ferroelectric-like hysteresis of electromechanical response

    SciTech Connect

    Morozovska, Anna N.; Morozovsky, Nicholas V.; Eliseev, Eugene A.; Varenyk, Olexandr V.; Kim, Yunseok; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei V.

    2014-08-14

    We performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, current-voltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived.

  6. Hysteresis prediction inside magnetic shields and application.

    PubMed

    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

  7. 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.

  8. Hysteresis prediction inside magnetic shields and application

    SciTech Connect

    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.

  9. 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.

  10. Angle-dependent loop shifts in antiferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Mao, Zhongquan; Zhan, Xiaozhi; Chen, Xi

    2016-08-01

    Experimentally hysteresis loop shifts have been widely observed in antiferromagnetic (AF) nanoparticles. Here numerical investigations show that this effect is dependent on the angle between the easy axis of the AF spins and the applied magnetic field in uncompensated nanoparticles. In contrast, the loop shifts disappear in compensated nanoparticles. The results suggest that the uncompensated spins and field directions are essential ingredients to generate loop shifts in AF nanoparticle systems. The present study hints at a possible way to optimize the magnetic performance of AF nanostructures.

  11. 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.

  12. Hysteresis Analysis and Positioning Control for a Magnetic Shape Memory Actuator

    PubMed Central

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2015-01-01

    Magnetic shape memory alloys (MSM alloys), a new kind of smart materials, have become a potential candidate in many engineering fields. MSMs have the advantage of bearing a huge strain, much larger than other materials. In addition, they also have fast response. These characteristics make MSM a good choice in micro engineering. However, MSMs display the obvious hysteresis phenomenon of nonlinear behavior. Thus the difficulty in using the MSM element as a positioning actuator is increased due to the hysteresis. In this paper, the hysteresis phenomenon of the MSM actuator is analyzed, and the closed-loop positioning control is also implemented experimentally. For that, a modified fuzzy sliding mode control (MFSMC) is proposed. The MFSMC and the PID control are used to design the controllers for realizing the positioning control. The experimental results are compared under different experimental conditions, such as different frequency, amplitude, and loading. The experimental results show that the precise positioning control of MFSMC can be achieved satisfactorily. PMID:25853405

  13. Hysteresis Analysis Based on the Ferroelectric Effect in Hybrid Perovskite Solar Cells.

    PubMed

    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

  14. 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.

  15. Method and apparatus for sub-hysteresis discrimination

    SciTech Connect

    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.

  16. Targeting the Body and the Mind: Evaluation of a P.E. Curriculum Intervention for Adolescents

    ERIC Educational Resources Information Center

    Loukaitou-Sideris, Anastasia

    2015-01-01

    P.E. classes are often the only opportunity for inner-city youth to engage in physical activity, but budget cuts and pressure to perform well on standardized tests has made P.E. an afterthought for many school administrators. This study evaluated the effectiveness of a new P.E. curriculum in five Los Angeles inner-city schools. Interviews were…

  17. Assessing catchment connectivity using hysteretic loops

    NASA Astrophysics Data System (ADS)

    Keesstra, Saskia; Masselink, Rens; Goni, Mikel; Campo, Miguel Angel; Gimenez, Rafael; Casali, Javier; Seeger, Manuel

    2015-04-01

    Sediment connectivity is a concept which can explain the origin, pathways and sinks of sediments within landscapes. This information is valuable for land managers to be able to take appropriate action at the correct place. Hysteresis between sediment and water discharge can give important information about the sources , pathways and conditions of sediment that arrives at the outlet of a catchment. "Hysteresis" happens when the sediment concentration associated with a certain flow rate is different depending on the direction in which the analysis is performed -towards the increase or towards the diminution of the flow. This phenomenon to some extent reflects the way in which the runoff generation processes are conjugated with those of the production and transport of sediments, hence the usefulness of hysteresis as a diagnostic hydrological parameter. However, the complexity of the phenomena and factors which determine hysteresis make its interpretation uncertain or, at the very least, problematic. Many types of hysteretic loops have been described as well as the cause for the shape of the loop, mainly describing the origin of the sediments. In this study, several measures to objectively classify hysteretic loops in an automated way were developed. These were consecutively used to classify several hundreds of loops from several agricultural catchments in Northern Spain. The data set for this study comes from four experimental watersheds in Navarre (Spain), owned and maintained by the Government of Navarre. These experimental watersheds have been monitored and studied since 1996 (La Tejería and Latxaga) and 2001 (Oskotz "principal", Op, and Oskotz "woodland", Ow). La Tejería and Latxaga watersheds, located in the Central Western part of Navarre, are roughly similar to each other regarding size (approximately 200 ha), geology (marls and sandstones), soils (fine texture topsoil), climate (humid sub Mediterranean) and land use (80-90% cultivated with winter grain crops

  18. 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.

  19. Memory characteristics of hysteresis and creep in multi-layer piezoelectric actuators: An experimental analysis

    NASA Astrophysics Data System (ADS)

    Biggio, Matteo; Butcher, Mark; Giustiniani, Alessandro; Masi, Alessandro; Storace, Marco

    2014-02-01

    In this paper we provide an experimental characterization of creep and hysteresis in a multi-layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first-order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.

  20. Improving Atomic Force Microscopy Imaging by a Direct Inverse Asymmetric PI Hysteresis Model

    PubMed Central

    Wang, Dong; Yu, Peng; Wang, Feifei; Chan, Ho-Yin; Zhou, Lei; Dong, Zaili; Liu, Lianqing; Li, Wen Jung

    2015-01-01

    A modified Prandtl–Ishlinskii (PI) model, referred to as a direct inverse asymmetric PI (DIAPI) model in this paper, was implemented to reduce the displacement error between a predicted model and the actual trajectory of a piezoelectric actuator which is commonly found in AFM systems. Due to the nonlinearity of the piezoelectric actuator, the standard symmetric PI model cannot precisely describe the asymmetric motion of the actuator. In order to improve the accuracy of AFM scans, two series of slope parameters were introduced in the PI model to describe both the voltage-increase-loop (trace) and voltage-decrease-loop (retrace). A feedforward controller based on the DIAPI model was implemented to compensate hysteresis. Performance of the DIAPI model and the feedforward controller were validated by scanning micro-lenses and standard silicon grating using a custom-built AFM. PMID:25654719

  1. Experimental comparison of rate-dependent hysteresis models in characterizing and compensating hysteresis of piezoelectric tube actuators

    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.

  2. Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress

    SciTech Connect

    Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

    1992-01-01

    The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters.

  3. Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume.

    PubMed

    Abe-Ouchi, Ayako; Saito, Fuyuki; Kawamura, Kenji; Raymo, Maureen E; Okuno, Jun'ichi; Takahashi, Kunio; Blatter, Heinz

    2013-08-01

    The growth and reduction of Northern Hemisphere ice sheets over the past million years is dominated by an approximately 100,000-year periodicity and a sawtooth pattern (gradual growth and fast termination). Milankovitch theory proposes that summer insolation at high northern latitudes drives the glacial cycles, and statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity, obliquity and precession cycles. Yet insolation alone cannot explain the strong 100,000-year cycle, suggesting that internal climatic feedbacks may also be at work. Earlier conceptual models, for example, showed that glacial terminations are associated with the build-up of Northern Hemisphere 'excess ice', but the physical mechanisms underpinning the 100,000-year cycle remain unclear. Here we show, using comprehensive climate and ice-sheet models, that insolation and internal feedbacks between the climate, the ice sheets and the lithosphere-asthenosphere system explain the 100,000-year periodicity. The responses of equilibrium states of ice sheets to summer insolation show hysteresis, with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles. The hysteresis loop of the North American ice sheet is such that after inception of the ice sheet, its mass balance remains mostly positive through several precession cycles, whose amplitudes decrease towards an eccentricity minimum. The larger the ice sheet grows and extends towards lower latitudes, the smaller is the insolation required to make the mass balance negative. Therefore, once a large ice sheet is established, a moderate increase in insolation is sufficient to trigger a negative mass balance, leading to an almost complete retreat of the ice sheet within several thousand years. This fast retreat is governed mainly by rapid ablation due to the lowered surface elevation resulting from delayed isostatic rebound, which is the lithosphere

  4. 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.

  5. Hysteresis in Pressure-Driven DNA Denaturation

    PubMed Central

    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

  6. 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.

  7. 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.

  8. Kinetic effects on double hysteresis in spin crossover molecular magnets analyzed with first order reversal curve diagram technique

    SciTech Connect

    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.

  9. Hysteresis behavior during reactive magnetron sputtering of Al{sub 2}O{sub 3} using a rotating cylindrical magnetron

    SciTech Connect

    Depla, D.; Haemers, J.; Buyle, G.; Gryse, R. de

    2006-07-15

    Rotating cylindrical magnetrons are used intensively on industrial scale. A rotating cylindrical magnetron on laboratory scale makes it possible to study this deposition technique in detail and under well controlled conditions. Therefore, a small scale rotating cylindrical magnetron was designed and used to study the influence of the rotation speed on the hysteresis behavior during reactive magnetron sputtering of aluminum in Ar/O{sub 2} in dc mode. This study reveals that the hysteresis shifts towards lower oxygen flows when the rotation speed of the target is increased, i.e., target poisoning occurs more readily when the rotation speed is increased. The shift is more pronounced for the lower branch of the hysteresis loop than for the upper branch of the hysteresis. This behavior can be understood qualitatively. The results also show that the oxidation mechanism inside the race track is different from the oxidation mechanism outside the race track. Indeed, outside the race track the oxidation mechanism is only defined by chemisorption while inside the race track reactive ion implantation will also influence the oxidation mechanism.

  10. Testing of a Loop Heat Pipe Subjected to Variable Accelerating Forces

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Ottenstein, Laura; Kaya, Tarik; Rogers, Paul; Hoff, Craig

    2000-01-01

    This paper presents viewgraphs of the functionality of a loop heat pipe that was subjected to variable accelerating forces. The topics include: 1) Summary of LHP (Loop Heat Pipe) Design Parameters; 2) Picture of the LHP; 3) Schematic of Test Setup; 4) Test Configurations; 5) Test Profiles; 6) Overview of Test Results; 7) Start-up; 8) Typical Start-up without Temperature Overshoot; 9) Start-up with a Large Temperature Overshoot; 10) LHP Operation Under Stationary Condition; 11) LHP Operation Under Continuous Acceleration; 12) LHP Operation Under Periodic Acceleration; 13) Effects of Acceleration on Temperature Oscillation and Hysteresis; 14) Temperature Oscillation/Hysteresis vs Spin Rate; and 15) Summary.

  11. 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.

  12. Hysteresis and creep modeling and compensation for a piezoelectric actuator using a fractional-order Maxwell resistive capacitor approach

    NASA Astrophysics Data System (ADS)

    Liu, Yanfang; Shan, Jinjun; Gabbert, Ulrich; Qi, Naiming

    2013-11-01

    A physics-based fractional-order Maxwell resistive capacitor (FOMRC) model is proposed to characterize nonlinear hysteresis and creep behaviors of a piezoelectric actuator (PEA). The Maxwell resistive capacitor (MRC) model is interpreted physically in the electric domain for PEAs. Based on this interpretation, the MRC model is modified to directly describe the relationship between the input voltage and the output displacement of a PEA. Then a procedure is developed to identify the parameters of the MRC model. This procedure is capable of being carried out using the measured input and output of a PEA only. A fractional-order dynamics is integrated into the MRC model to describe the effect of creep, as well as the detachment of hysteresis loops caused by creep. Moreover, the inverse FOMRC model is constructed to compensate for hysteresis and creep in an open-loop positioning application of PEAs. Simulation and experiments are carried out to validate the proposed model. The PEA compensated by the inverse FOMRC model shows an excellent linear behavior.

  13. Modeling the Effect of Interface Wear on Fatigue Hysteresis Behavior of Carbon Fiber-Reinforced Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2015-12-01

    An analytical method has been developed to investigate the effect of interface wear on fatigue hysteresis behavior in carbon fiber-reinforced ceramic-matrix composites (CMCs). The damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and interface wear, fibers fracture, slip and pull-out, have been considered. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Upon first loading to fatigue peak stress and subsequent cyclic loading, the fibers failure probabilities and fracture locations were determined by combining the interface wear model and fiber statistical failure model based on the assumption that the loads carried by broken and intact fibers satisfy the global load sharing criterion. The effects of matrix properties, i.e., matrix cracking characteristic strength and matrix Weibull modulus, interface properties, i.e., interface shear stress and interface debonded energy, fiber properties, i.e., fiber Weibull modulus and fiber characteristic strength, and cycle number on fibers failure, hysteresis loops and interface slip, have been investigated. The hysteresis loops under fatigue loading from the present analytical method were in good agreement with experimental data.

  14. Magnetic evaluation of irradiation hardening in A533B reactor pressure vessel steels: Magnetic hysteresis measurements and the model analysis

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Yamamoto, T.; Klingensmith, D.; Odette, G. R.; Kikuchi, H.; Kamada, Y.

    2012-03-01

    We report results of measurements of magnetic minor hysteresis loops for neutron-irradiated A533B nuclear reactor pressure vessel steels varying alloy composition and irradiation condition. A minor-loop coefficient, which is obtained from a scaling power law between minor-loop parameters exhibits a steep decrease just after irradiation, followed by a maximum in the intermediate fluence regime for most alloys. A model analysis assuming Avrami-type growth for Cu-rich precipitates and an empirical logarithmic law for relaxation of residual stress demonstrates that an increment of the coefficient due to Cu-rich precipitates increases with Cu and Ni contents and is in proportion to a yield stress change, which is related to irradiation hardening.

  15. Rollercoaster Loop Shapes

    ERIC Educational Resources Information Center

    Pendrill, Ann-Marie

    2005-01-01

    Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.

  16. Rollercoaster loop shapes

    NASA Astrophysics Data System (ADS)

    Pendrill, Ann-Marie

    2005-11-01

    Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.

  17. Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

    SciTech Connect

    Heczko, O. Drahokoupil, J.; Straka, L.

    2015-05-07

    Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni{sub 50.0}Mn{sub 28.5}Ga{sub 21.5} single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

  18. Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

    NASA Astrophysics Data System (ADS)

    Heczko, O.; Drahokoupil, J.; Straka, L.

    2015-05-01

    Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni50.0Mn28.5Ga21.5 single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

  19. Square-loop cobalt/gold multilayers

    NASA Astrophysics Data System (ADS)

    Gambino, R. J.; Ruf, R. R.

    1990-05-01

    Multilayers of Co and Au with perpendicular hysteresis loop squareness ratios of ˜1 have been prepared by e-beam evaporation. These films have perpendicular anisotropy in the as-deposited condition in contrast to other work in which Co/Au multilayers, prepared by ion beam sputtering, showed perpendicular anisotropy only after annealing at 300 °C. The Faraday rotation of these square-loop multilayers is about 9×105 deg/cm of Co or 1×105 deg/cm of total thickness at a wavelength of 633 nm. These values indicate an enhancement of the Faraday rotation of Co at this wavelength by about a factor of 2. This may be a plasma-edge enhancement effect similar to that reported by Katayama et al. [Phys. Rev. Lett. 60, 1426 (1988)] in the Kerr effect of Fe/Au multilayers.

  20. 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.

  1. Adaptive feed-forward hysteresis compensation for piezoelectric actuators

    NASA Astrophysics Data System (ADS)

    Eielsen, Arnfinn Aas; Gravdahl, Jan Tommy; Pettersen, Kristin Y.

    2012-08-01

    Piezoelectric actuators are often employed for high-resolution positioning tasks. Hysteresis and creep nonlinearities inherent in such actuators deteriorate positioning accuracy. An online adaptive nonlinear hysteresis compensation scheme for the case of symmetric hysteretic responses and certain periodic reference trajectories is presented. The method has low complexity and is well suited for real-time implementation. Experimental results are presented in order to verify the method, and it is seen that the error due to hysteresis is reduced by more than 90% compared to when assuming a linear response.

  2. Static measurements of slender delta wing rolling moment hysteresis

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Levin, Daniel

    1991-01-01

    Slender delta wing planforms are susceptible to self-induced roll oscillations due to aerodynamic hysteresis during the limit cycle roll oscillation. Test results are presented which clearly establish that the static rolling moment hysteresis has a damping character; hysteresis tends to be greater when, due to either wing roll or side slip, the vortex burst moves back and forth over the wing trailing edge. These data are an indirect indication of the damping role of the vortex burst during limit cycle roll oscillations.

  3. Modeling the effect of piezoceramic hysteresis in structural vibration control

    NASA Astrophysics Data System (ADS)

    Ozer, Mehmet B.; Royston, Thomas J.

    2001-08-01

    Dielectric hysteresis in piezoceramic transducers can degrade their performance in structural vibration control applications. Different hysteresis models have been applied to piezoelectric transducers, including those based on Preisach, Jiles-Atherton and Ishlinskii concepts. Relationships between these and other models, new experimental identification schemes and multi-term describing function representations of some of them are reviewed. Then, system equations that incorporate the hysteretic behavior are formulated for two pedagogical smart structural systems: a passively shunted / actively driven PZT wafer on (1) a simply supported thin plate and (2) a simply supported thin beam. The effect of PZT hysteresis on optimized passive and hybrid vibration control strategies is evaluated.

  4. Critical hysteresis for n-component magnets

    NASA Astrophysics Data System (ADS)

    Silveira, Ravá Da; Kardar, Mehran

    1999-02-01

    Earlier work on dynamical critical phenomena in the context of magnetic hysteresis for uniaxial (scalar) spins is extended to the case of a multicomponent (vector) field. From symmetry arguments and a perturbative renormalization-group approach (in the path-integral formalism), it is found that the generic behavior at long time and length scales is described by the scalar fixed point (reached for a given value of the magnetic field and of the quenched disorder), with the corresponding Ising-like exponents. By tuning an additional parameter, however, a fully rotationally invariant fixed point can be reached, at which all components become critical simultaneously, with O(n)-like exponents. Furthermore, the possibility of a spontaneous nonequilibrium transverse ordering, controlled by a distinct fixed point, is unveiled and the associated exponents calculated. In addition to these central results, a didactic ``derivation'' of the equations of motion for the spin field are given, the scalar model is revisited and treated in a more direct fashion, and some issues pertaining to time dependences and the problem of multiple solutions within the path-integral formalism are clarified.

  5. 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.

  6. Hysteresis and transition in swirling nonpremixed flames

    SciTech Connect

    Tummers, M.J.; Huebner, A.W.; van Veen, E.H.; Hanjalic, K.; van der Meer, T.H.

    2009-02-15

    Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change from an attached swirling flame (unidirectional or with a weak bluff-body recirculation), to a lifted flame with a strong toroidal vortex occupying the bulk of the flame. Despite dramatic differences in their structures, mixing intensities and combustion performance, both flame types can be realised at identical flow rates, equivalence ratio and swirl intensity. We report here on comprehensive investigations of the two flame regimes at the same conditions in a well-controlled experiment in which the swirl was generated by the rotating outer pipe of the annular burner air passage. Fluid velocity measured with PIV (particle image velocimetry), the qualitative detection of reaction zones from OH PLIF (planar laser-induced fluorescence) and the temperature measured by CARS (coherent anti-Stokes Raman spectroscopy) revealed major differences in vortical structures, turbulence, mixing and reaction intensities in the two flames. We discuss the transition mechanism and arguments for the improved mixing, compact size and a broader stability range of the blue flame in comparison to the long yellow flame. (author)

  7. Electroosmotic Flow Hysteresis for Dissimilar Anionic Solutions.

    PubMed

    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

  8. Water Stream "Loop-the-Loop"

    ERIC Educational Resources Information Center

    Jefimenko, Oleg

    1974-01-01

    Discusses the design of a modified loop-the-loop apparatus in which a water stream is used to illustrate centripetal forces and phenomena of high-velocity hydrodynamics. Included are some procedures of carrying out lecture demonstrations. (CC)

  9. Hysteresis as a Marker for Complex, Overlapping Landscapes in Proteins

    PubMed Central

    Andrews, Benjamin T.; Capraro, Dominique T.; Sulkowska, Joanna I.; Onuchic, José N.; Jennings, Patricia A.

    2013-01-01

    Topologically complex proteins fold by multiple routes as a result of hard-to-fold regions of the proteins. Oftentimes these regions are introduced into the protein scaffold for function and increase frustration in the otherwise smooth-funneled landscape. Interestingly, while functional regions add complexity to folding landscapes, they may also contribute to a unique behavior referred to as hysteresis. While hysteresis is predicted to be rare, it is observed in various proteins, including proteins containing a unique peptide cyclization to form a fluorescent chromophore as well as proteins containing a knotted topology in their native fold. Here, hysteresis is demonstrated to be a consequence of the decoupling of unfolding events from the isomerization or hula-twist of a chromophore in one protein and the untying of the knot in a second protein system. The question now is- can hysteresis be a marker for the interplay of landscapes where complex folding and functional regions overlap? PMID:23525263

  10. Perovskite-Fullerene Hybrid Materials Eliminate Hysteresis In Planar Diodes

    SciTech Connect

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian; Maksymovych, Petro; Sargent, Edward H.

    2015-03-31

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite–PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3 antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  11. Thermal-expansion hysteresis in graphite/glass composites

    SciTech Connect

    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.

  12. Aspects of hysteresis in unsaturated porous media flow

    NASA Astrophysics Data System (ADS)

    van Duijn, Hans

    2016-04-01

    About 20 years ago, Peter Raats and I wrote a technical note related to the horizontal redistribution in unsaturated porous media with hysteresis in the capillary pressure (P.A.C. Raats & C.J. van Duijn, A note on horizontal redistribution with capillary hysteresis, WWR 31, p. 231-232, 1995). In the first part of my presentation, I will revisit the results of that paper. In particular the cases of unconventional flow, where the water flows from the dry region to the wet region. A comparison will be made with results obtained with the current interface area models as introduced by Gray & Hassanizadeh. I will explain and outline the differences. In the second part, travelling wave solutions of Richards equation with gravity and with hysteresis in both the capillary pressure and relative permeability will be discussed. It will be explained why such solutions oscillate in space-time and how they behave as the hysteresis regularization vanishes.

  13. Low-Hysteresis Flow-Through Wind-Tunnel Balance

    NASA Technical Reports Server (NTRS)

    Kunz, N.; Luna, P. M.; Roberts, A. C.; Smith, R. C.; Horne, W. L.; Smith, K. M.

    1992-01-01

    Improved flow-through wind-tunnel balance includes features minimizing both spurious force readings caused by internal pressurized flow and mechanical hysteresis. Symmetrical forces caused by internal flow cancelled.

  14. Hysteresis modeling of clamp band joint with macro-slip

    NASA Astrophysics Data System (ADS)

    Qin, Zhaoye; Cui, Delin; Yan, Shaoze; Chu, Fulei

    2016-01-01

    Clamp band joints are commonly used to connect spacecrafts with launch vehicles. Due to the frictional slippage between the joint components, hysteresis behavior might occur at joint interfaces under cyclic loading. The joint hysteresis will bring friction damping into the launching systems. In this paper, a closed-form hysteresis model for the clamp band joint is developed based on theoretical and numerical analyses of the interactions of the joint components. Then, the hysteresis model is applied to investigating the dynamic response of a payload fastened by the clamp band joint, where the nonlinearity and friction damping effects of the joint is evaluated. The proposed analytical model, which is validated by both finite element analyses and quasi-static experiments, has a simple form with sound accuracy and can be incorporated into the dynamic models of launching systems conveniently.

  15. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes

    NASA Astrophysics Data System (ADS)

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

    2015-05-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3- antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  16. Could linear hysteresis contribute to shear wave losses in tissues?

    PubMed

    Parker, Kevin J

    2015-04-01

    For nearly 100 y in the study of cyclical motion in materials, a particular phenomenon called "linear hysteresis" or "ideal hysteretic damping" has been widely observed. More recently in the field of shear wave elastography, the basic mechanisms underlying shear wave losses in soft tissues are in question. Could linear hysteresis play a role? An underlying theoretical question must be answered: Is there a real and causal physical model that is capable of producing linear hysteresis over a band of shear wave frequencies used in diagnostic imaging schemes? One model that can approximately produce classic linear hysteresis behavior, by examining a generalized Maxwell model with a specific power law relaxation spectrum, is described here. This provides a theoretical plausibility for the phenomenon as a candidate for models of tissue behavior. PMID:25701527

  17. A MHO-based magnetic hysteresis model for amorphous materials

    NASA Astrophysics Data System (ADS)

    Ma, Lianwei; Shen, Yu; Li, Jinrong; Zhao, Xinlong

    2014-12-01

    A magnetic hysteretic operator (MHO) is proposed in this paper. Based on the constructed MHO, the input space of neural networks is expanded from one-dimension to two-dimension using the expanded space method so that the one-to-multiple mapping of magnetic hysteresis is transformed into one-to-one mapping. Based on the expanded input space, a neural network is employed to identify magnetic hysteresis. The result of an experimental example suggests the proposed approach is effective.

  18. Stabilization of supercooled fluids by thermal hysteresis proteins.

    PubMed Central

    Wilson, P W; Leader, J P

    1995-01-01

    It has been reported that thermal hysteresis proteins found in many cold-hardy, freeze-avoiding arthropods stabilize their supercooled body fluids. We give evidence that fish antifreeze proteins, which also produce thermal hysteresis, bind to and reduce the efficiency of heterogenous nucleation sites, rather than binding to embryonic ice nuclei. We discuss both possible mechanisms for stabilization of supercooled body fluids and also describe a new method for measuring and defining the supercooling point of small volumes of liquid. PMID:7612853

  19. Mathematical models of hysteresis. Progress report, January 1993--December 1993

    SciTech Connect

    Mayergoyz, I.D.

    1993-09-01

    Progress is reported in 7 areas: development of vector Preisach-type models of hysteresis; modeling of rotational hysteretic losses; experimental testing of generalized vector Preisach models of hysteresis; development of Preisach-type models for aftereffect; analytical investigation of penetration of electromagnetic fields into superconductors with gradual resistive transitions; computation of magnetic fields in hysteretic media; and development of new techniques for calculating 3-D eddy current problems.

  20. Aileron roll hysteresis effects on entry of space shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Powell, R. W.

    1977-01-01

    Six-degree-of-freedom simulations of the space shuttle orbiter entry with control hysteresis were conducted on the NASA Langley Research Center interactive simulator known as the automatic reentry flight dynamics simulator. These simulations revealed that the vehicle can tolerate control hysteresis producing a + or - 50 percent change in the nominal aileron roll characteristics and an offset in the nominal characteristics equivalent to a + or - 5 deg aileron deflection with little increase in the reaction control system's fuel consumption.

  1. Controlling hysteresis in superconducting constrictions with a resistive shunt

    NASA Astrophysics Data System (ADS)

    Kumar, Nikhil; Winkelmann, C. B.; Biswas, Sourav; Courtois, H.; Gupta, Anjan K.

    2015-07-01

    We demonstrate control of the thermal hysteresis in superconducting constrictions by adding a resistive shunt. In order to prevent thermal relaxation oscillations, the shunt resistor is placed in close proximity to the constriction, making the inductive current-switching time smaller than the thermal equilibration time. We investigate the current-voltage characteristics of the same constriction with and without the shunt-resistor. The widening of the hysteresis-free temperature range is explained on the basis of a simple model.

  2. Self aligned hysteresis free carbon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Shlafman, M.; Tabachnik, T.; Shtempluk, O.; Razin, A.; Kochetkov, V.; Yaish, Y. E.

    2016-04-01

    Hysteresis phenomenon in the transfer characteristics of carbon nanotube field effect transistor (CNT FET) is being considered as the main obstacle for successful realization of electronic devices based on CNTs. In this study, we prepare four kinds of CNTFETs and explore their hysteretic behavior. Two kinds of devices comprise on-surface CNTs (type I) and suspended CNTs (type II) with thin insulating layer underneath and a single global gate which modulates the CNT conductance. The third and fourth types (types III and IV) consist of suspended CNT over a metallic local gate underneath, where for type IV the local gate was patterned self aligned with the source and drain electrodes. The first two types of devices, i.e., type I and II, exhibit substantial hysteresis which increases with scanning range and sweeping time. Under high vacuum conditions and moderate electric fields ( |E |>4 ×106 V /cm ), the hysteresis for on-surface devices cannot be eliminated, as opposed to suspended devices. Interestingly, type IV devices exhibit no hysteresis at all at ambient conditions, and from the different roles which the global and local gates play for the four types of devices, we could learn about the hysteresis mechanism of this system. We believe that these self aligned hysteresis free FETs will enable the realization of different electronic devices and sensors based on CNTs.

  3. Adhesion hysteresis and friction at nanometer and micrometer lengths

    SciTech Connect

    Szoszkiewicz, Robert; Bhushan, Bharat; Huey, Bryan D.; Kulik, Andrzej J.; Gremaud, Gerard

    2006-01-01

    Comparisons between adhesion hysteresis and friction at nanometer and micrometer length scales were investigated experimentally and theoretically. Nanoscale adhesion hysteresis was measured using the ultrasonic force microscopy (UFM) on mica, calcite, and a few metallic samples (Pt, Au, Cu, Zn, Ti, and Fe). Obtained adhesion hysteresis ranged between 4x10{sup -19} and 4x10{sup -18} J. At the microscale a similar setup with a nanoindenter was used and the same samples were investigated. Adhesion hysteresis measured at the microscale ranged between 8x10{sup -17} and 14x10{sup -17} J. Friction was investigated via lateral force microscopy, as well as by scratch tests done with the nanoindenter. Numerical simulations based on the UFM model as well as established theories of contact mechanics studied qualitative dependencies of adhesion hysteresis on experimental parameters. Quantitative relations between adhesion hysteresis and friction were obtained through an analytic model relying on elastic and adhesive properties of the contact. The model agreed with measurements and simulations.

  4. 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.

  5. A self-adaptive genetic algorithm to estimate JA model parameters considering minor loops

    NASA Astrophysics Data System (ADS)

    Lu, Hai-liang; Wen, Xi-shan; Lan, Lei; An, Yun-zhu; Li, Xiao-ping

    2015-01-01

    A self-adaptive genetic algorithm for estimating Jiles-Atherton (JA) magnetic hysteresis model parameters is presented. The fitness function is established based on the distances between equidistant key points of normalized hysteresis loops. Linearity function and logarithm function are both adopted to code the five parameters of JA model. Roulette wheel selection is used and the selection pressure is adjusted adaptively by deducting a proportional which depends on current generation common value. The Crossover operator is established by combining arithmetic crossover and multipoint crossover. Nonuniform mutation is improved by adjusting the mutation ratio adaptively. The algorithm is used to estimate the parameters of one kind of silicon-steel sheet's hysteresis loops, and the results are in good agreement with published data.

  6. A neural approach for the numerical modeling of two-dimensional magnetic hysteresis

    SciTech Connect

    Cardelli, E.; Faba, A.; Laudani, A.; Riganti Fulginei, F.; Salvini, A.

    2015-05-07

    This paper deals with a neural network approach to model magnetic hysteresis at macro-magnetic scale. Such approach to the problem seems promising in order to couple the numerical treatment of magnetic hysteresis to FEM numerical solvers of the Maxwell's equations in time domain, as in case of the non-linear dynamic analysis of electrical machines, and other similar devices, making possible a full computer simulation in a reasonable time. The neural system proposed consists of four inputs representing the magnetic field and the magnetic inductions components at each time step and it is trained by 2-d measurements performed on the magnetic material to be modeled. The magnetic induction B is assumed as entry point and the output of the neural system returns the predicted value of the field H at the same time step. A suitable partitioning of the neural system, described in the paper, makes the computing process rather fast. Validations with experimental tests and simulations for non-symmetric and minor loops are presented.

  7. Separation of ferromagnetic components by analyzing the hysteresis loops of remanent magnetization

    NASA Astrophysics Data System (ADS)

    Kosareva, L. R.; Utemov, E. V.; Nurgaliev, D. K.; Shcherbakov, V. P.; Kosarev, V. E.; Yasonov, P. G.

    2015-09-01

    The new method is suggested for separating ferromagnetic components in sediments through analyzing the coercivity spectra of the samples by the continuous wavelet transform with the Gaussian-based wavelet (MHAT). A total of 1056 samples of Lake Khuvsgul's sediments (Mongolia) are studied. At least four groups of magnetic components are identified based on the analysis of their magnetization and remagnetization curves. Almost all samples are found to contain two components of bacterial origin which are represented by the assemblages of the interacting single-domain grains and differ by the grain compositions (magnetite and greigite). The applicability of the magnetic data for diagnosing magnetotactic bacteria in sediments and building paleoecological and paleoclimatic reconstructions is demonstrated.

  8. INSIDE THE HYSTERESIS LOOP: MULTIPLICITY OF INTERNAL STATES IN CONFINED FLUIDS. (R825959)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy

    PubMed Central

    2011-01-01

    High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field. PMID:21711935

  10. Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets

    NASA Astrophysics Data System (ADS)

    Kalmykov, Yuri P.; Titov, Serguey V.; Coffey, William T.

    2015-11-01

    The nonlinear ac stationary response of uniaxial paramagnets and superparamagnets—nanoscale solids or clusters with spin number S ˜100-104 —in superimposed uniform ac and dc bias magnetic fields of arbitrary strength, each applied along the easy axis of magnetization, is determined by solving the evolution equation for the reduced density matrix represented as a finite set of three-term differential-recurrence relations for its diagonal matrix elements. The various harmonic components arising from the nonlinear response of the magnetization, dynamic magnetic hysteresis loops, etc., are then evaluated via matrix continued fractions indicating a pronounced dependence of the response on S arising from the quantum spin dynamics, which differ markedly from the magnetization dynamics of classical nanomagnets. In the linear response approximation, the results concur with existing solutions.

  11. Intelligent compensation of friction, ripple, and hysteresis via a regulated chatter.

    PubMed

    Zhao, S; Putra, A S; Tan, K K; Panda, S K; Lee, T H

    2006-07-01

    In this paper, a hybrid control scheme utilizing a PID feedback control with an additional regulated chatter signal is developed to compensate motion impeding influences such as the effects due to friction, force ripples, and hysteresis in linear piezoelectric motor. The regulated chatter signal is a pulse sequence superimposed on the PID control signal. It has a fixed amplitude, and a pulse width regulated via iterative learning control. As such, the scheme is expected to be useful for applications involving iterative motion sequences. An analysis of the closed-loop performance is presented in the paper. Simulation and experimental results are also furnished to demonstrate that the proposed control scheme can reduce tracking errors significantly. PMID:16856637

  12. Metallogrid Single-Molecule Magnet: Solvent-Induced Nuclearity Transformation and Magnetic Hysteresis at 16 K.

    PubMed

    Huang, Wei; Shen, Fu-Xing; Wu, Shu-Qi; Liu, Li; Wu, Dayu; Zheng, Zhe; Xu, Jun; Zhang, Ming; Huang, Xing-Cai; Jiang, Jun; Pan, Feifei; Li, Yao; Zhu, Kun; Sato, Osamu

    2016-06-01

    Structural assembly and reversible transformation between a metallogrid Dy4 SMM (2) and its fragment Dy2 (1) were established in the different solvent media. The zero-field magnetization relaxation was slowed for dysprosium metallogrid (2) with relaxation barrier of Ueff = 61.3 K when compared to Dy2 (1). Both magnetic dilution and application of a moderate magnetic field suppress ground-state quantum tunneling of magnetization and result in an enhanced Ueff of 119.9 and 96.7 K for 2, respectively. Interestingly, the lanthanide metallogrid complex (2) exhibits magnetic hysteresis loop even up to 16 K at a given field sweep rate of 500 Oe/s. PMID:27164298

  13. Automated setup for magnetic hysteresis characterization based on a voltage controlled current source with 500 kHz full power bandwidth and 10 A peak-to-peak current

    SciTech Connect

    Calabrese, G.; Capineri, L.; Granato, M.; Frattini, G.

    2015-04-15

    This paper describes the design of a system for the characterization of magnetic hysteresis behavior in soft ferrite magnetic cores. The proposed setup can test magnetic materials exciting them with controlled arbitrary magnetic field waveforms, including the capability of providing a DC bias, in a frequency bandwidth up to 500 kHz, with voltages up to 32 V peak-to-peak, and currents up to 10 A peak-to-peak. In order to have an accurate control of the magnetic field waveform, the system is based on a voltage controlled current source. The electronic design is described focusing on closed loop feedback stabilization and passive components choice. The system has real-time hysteretic loop acquisition and visualization. The comparisons between measured hysteresis loops of sample magnetic materials and datasheet available ones are shown. Results showing frequency and thermal behavior of the hysteresis of a test sample prove the system capabilities. Moreover, the B-H loops obtained with a multiple waveforms excitation signal, including DC bias, are reported. The proposal is a low-cost and replicable solution for hysteresis characterization of magnetic materials used in power electronics.

  14. Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

    NASA Astrophysics Data System (ADS)

    Fovet, O.; Ruiz, L.; Hrachowitz, M.; Faucheux, M.; Gascuel-Odoux, C.

    2015-01-01

    While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system-internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure, and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. We analysed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (Environmental Research Observatory ERO AgrHys (ORE AgrHys)). The saturated-zone storage was estimated using distributed shallow groundwater levels and the unsaturated-zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow and saturated, and unsaturated storages led us to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, the integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such a system-like approach is likely to improve model selection.

  15. Hydrological annual hysteresis: functional signature for assessing the consistency of catchment conceptual models?

    NASA Astrophysics Data System (ADS)

    Fovet, Ophelie; Laurent, Ruiz; Markus, Hrachowitz; Chantal, Gascuel-Odoux

    2015-04-01

    While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. In this study, the annual hysteric patterns observed between stream flow and water storage is analysed both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (ORE AgrHys). The saturated zone storage was estimated using distributed shallow groundwater levels and the unsaturated zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow, saturated, and unsaturated storages led to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such systems-like approach is likely to improve model selection.

  16. Hydrological hysteresis in catchments and its value for assessing process consistency in conceptual models

    NASA Astrophysics Data System (ADS)

    Fovet, O.; Ruiz, L.; Hrachowitz, M.; Faucheux, M.; Gascuel-Odoux, C.

    2014-05-01

    While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. We analyzed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (ORE AgrHys). The saturated zone storage was estimated using distributed shallow groundwater levels and the unsaturated zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow, saturated, and unsaturated storages led to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such systems-like approach is likely to improve model selection.

  17. A.S.P.E.N. Standards for Nutrition Support: Home and Alternate Site Care.

    PubMed

    Durfee, Sharon M; Adams, Stephen C; Arthur, Elaine; Corrigan, Mandy L; Hammond, Kathleen; Kovacevich, Debra S; McNamara, Kevn; Pasquale, Jack A

    2014-06-25

    The American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) is a professional society of physicians, nurses, dietitians, pharmacists, nurse practitioners, physician assistants, other allied health professionals, and researchers. A.S.P.E.N. envisions an environment in which every patient receives safe, efficacious, and high-quality nutrition care. A.S.P.E.N.'s mission is to improve patient care by advancing the science and practice of clinical nutrition and metabolism. These combined Standards for Nutrition Support: Home Care and Alternate Site Care are an update of the 2005 and 2006 standards. PMID:24964788

  18. Hysteresis in a synthetic mammalian gene network.

    PubMed

    Kramer, Beat P; Fussenegger, Martin

    2005-07-01

    Bistable and hysteretic switches, enabling cells to adopt multiple internal expression states in response to a single external input signal, have a pivotal impact on biological systems, ranging from cell-fate decisions to cell-cycle control. We have designed a synthetic hysteretic mammalian transcription network. A positive feedback loop, consisting of a transgene and transactivator (TA) cotranscribed by TA's cognate promoter, is repressed by constitutive expression of a macrolide-dependent transcriptional silencer, whose activity is modulated by the macrolide antibiotic erythromycin. The antibiotic concentration, at which a quasi-discontinuous switch of transgene expression occurs, depends on the history of the synthetic transcription circuitry. If the network components are imbalanced, a graded rather than a quasi-discontinuous signal integration takes place. These findings are consistent with a mathematical model. Synthetic gene networks, which are able to emulate natural gene expression behavior, may foster progress in future gene therapy and tissue engineering initiatives. PMID:15972812

  19. OPE for super loops

    NASA Astrophysics Data System (ADS)

    Sever, Amit; Vieira, Pedro; Wang, Tianheng

    2011-11-01

    We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.

  20. The preprocessed doacross loop

    NASA Technical Reports Server (NTRS)

    Saltz, Joel H.; Mirchandaney, Ravi

    1990-01-01

    Dependencies between loop iterations cannot always be characterized during program compilation. Doacross loops typically make use of a-priori knowledge of inter-iteration dependencies to carry out required synchronizations. A type of doacross loop is proposed that allows the scheduling of iterations of a loop among processors without advance knowledge of inter-iteration dependencies. The method proposed for loop iterations requires that parallelizable preprocessing and postprocessing steps be carried out during program execution.

  1. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  2. The origin of noise and hysteresis in permalloy ring-core fluxgate sensors

    NASA Astrophysics Data System (ADS)

    Narod, Barry

    2013-04-01

    in permalloy ring-core fluxgate sensors a single phenomenon may cause both fluxgate noise and magnetic hysteresis. It also provides an explanation for Barkhausen noise, remanence and coercivity. It can also resolve the "domain nucleation problem." in the unmagnetized state a high-quality permalloy foil takes a domain structure generally referred to as "stripe domains," which present at the free surface as parallel, uniformly spaced domain walls bounding regions of alternating 'in' and 'out' leakage flux, and domain walls crossing the entire thickness of the foil. The leakage flux is a requirement of the random orientation, grain-by-grain, of magnetic easy axes' angles with respect to the foil free surface, and creates a free space field with a magnetostatic energy cost. This together with domain wall energy determines an energy budget to be minimized. Throughout the magnetization cycle the free surface domain pattern remains essentially unchanged, due to the extreme magnetostatic energy cost such a change would elicit. Thus domain walls are 'pinned' to free surfaces. As the fluxgate core is driven to saturation, domain walls pinned at the free surfaces first bulge then reconnect to form a new domain configuration this author has called "channel domains", which are attached to free surfaces. Energy released during the domain wall reconnection manifests as Barkhausen noise, while the reconnection itself manifests as a Barkhausen jump. The approach to saturation now continues as reversible channel domain compression. Driving the permalloy into deep saturation will compress the channel domains to arbitrarily small thickness, but will not cause them to denucleate. Returning from saturation the channel domain structure will survive through zero drive H, thus explaining remanence. The Barkhausen jumps being irreversible, exothermic events are sources of fluxgate noise. It is also the case that fluxgate signal power is proportional to B-H loop curvature, that is to the

  3. Simulation of a vector hysteresis measurement system taking hysteresis into account by the vector Preisach model

    NASA Astrophysics Data System (ADS)

    Kuczmann, Miklós

    2008-02-01

    The paper deals with the numerical analysis of a rotational single sheet tester with round-shaped specimen (RRSST) which is now under construction. The measurement setup consists of an induction motor the rotor of which has been removed, and its windings have been replaced to a special two phase one which can generate homogeneous magnetic field inside the motor. The two orthogonal components of the magnetic field intensity and of the magnetic flux density vectors can be measured by H-coils and B-coils, respectively. The Finite Element Method (FEM) with the T, Φ-Φ potential formulation has been applied in the simulations. The vector hysteresis property of the specimen has been approximated by the vector Preisach model. Finally, the nonlinear problem has been solved by the fixed-point technique. The aim of the present work is to focus on the design aspects of this kind of measurement system.

  4. M-H loop tracer based on digital signal processing for low frequency characterization of extremely thin magnetic wires

    SciTech Connect

    Butta, M.; Ripka, P.; Infante, G.; Badini-Confalonieri, G. A.; Vazquez, M.

    2009-08-15

    A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5 {mu}m thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.

  5. Heterogeneous side chain conformation highlights a network of interactions implicated in hysteresis of the knotted protein, minimal tied trefoil

    NASA Astrophysics Data System (ADS)

    Burban, David J.; Haglund, Ellinor; Capraro, Dominique T.; Jennings, Patricia A.

    2015-09-01

    Hysteresis is a signature for a bistability in the native landscape of a protein with significant transition state barriers for the interconversion of stable species. Large global stability, as in GFP, contributes to the observation of this rare hysteretic phenomenon in folding. The signature for such behavior is non-coincidence in the unfolding and refolding transitions, despite waiting significantly longer than the time necessary for complete denaturation. Our work indicates that hysteresis in the knotted protein, the minimal tied trefoil from Thermotoga maritma (MTTTm), is mediated by a network of side chain interactions within a tightly packed core. These initially identified interactions include proline 62 from a tight β-like turn, phenylalanine 65 at the beginning of the knotting loop, and histidine 114 that initiates the threading element. It is this tightly packed region and the knotting element that we propose is disrupted with prolonged incubation in the denatured state, and is involved in the observed hysteresis. Interestingly, the disruption is not linked to backbone interactions, but rather to the packing of side chains in this critical region.

  6. Effects of Contact Angle Hysteresis on Ice Adhesion and Growth over Superhydrophobic Surfaces under Dynamic Flow Conditions

    SciTech Connect

    Sarshar, Mohammad Amin; Swarctz, Christopher; Hunter, Scott Robert; Simpson, John T; Choi, Chang-Hwan

    2012-01-01

    In this paper, the iceophobic properties of superhydrophobic surfaces are investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared by coating the substrates of aluminum and steel plates with nano-structured hydrophobic particles. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20 F accompanying micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by high-resolution CCD cameras. Results show that the superhydrophobic coatings significantly delay the ice formation and accretion even under the dynamic flow condition of the highly energetic impingement of accelerated super-cooled water droplets. It is found that there is a time scale for this phenomenon (delay of the ice formation) which has a clear correlation with the contact angle hysteresis and the length scale of surface roughness of the superhydrophobic surface samples, being the highest for the plate with the lowest contact angle hysteresis and finer surface roughness. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis (dynamic property) and the non-wetting superhydrophobic state under the hydrodynamic pressure of impinging droplets, rather than to only have a high contact angle (static property), in order to result in efficient anti-icing properties under dynamic conditions such as forced flows.

  7. Heterogeneous side chain conformation highlights a network of interactions implicated in hysteresis of the knotted protein, minimal tied trefoil.

    PubMed

    Burban, David J; Haglund, Ellinor; Capraro, Dominique T; Jennings, Patricia A

    2015-09-01

    Hysteresis is a signature for a bistability in the native landscape of a protein with significant transition state barriers for the interconversion of stable species. Large global stability, as in GFP, contributes to the observation of this rare hysteretic phenomenon in folding. The signature for such behavior is non-coincidence in the unfolding and refolding transitions, despite waiting significantly longer than the time necessary for complete denaturation. Our work indicates that hysteresis in the knotted protein, the minimal tied trefoil from Thermotoga maritma (MTTTm), is mediated by a network of side chain interactions within a tightly packed core. These initially identified interactions include proline 62 from a tight β-like turn, phenylalanine 65 at the beginning of the knotting loop, and histidine 114 that initiates the threading element. It is this tightly packed region and the knotting element that we propose is disrupted with prolonged incubation in the denatured state, and is involved in the observed hysteresis. Interestingly, the disruption is not linked to backbone interactions, but rather to the packing of side chains in this critical region. PMID:26291198

  8. Heterogeneous side chain conformation highlights a network of interactions implicated in hysteresis of the knotted protein, Minimal Tied Trefoil (MTTTm)

    PubMed Central

    Capraro, Dominique T.; Jennings, Patricia A.

    2015-01-01

    Hysteresis is a signature for a bistability in the native landscape of a protein with significant transition state barriers for the interconversion of stable species. Large global stability, as in GFP, contributes to the observation of this rare hysteretic phenomenon in folding. The signature for such behavior is non-coincidence in the unfolding and refolding transitions, despite waiting significantly longer than the time necessary for complete denaturation. Our work indicates that hysteresis in the knotted protein, the Minimal Tied Trefoil from Thermotoga maritma (MTTTm), is mediated by a network of side chain interactions within a tightly packed core. These initially identified interactions include proline 62 from a tight β-like turn, phenylalanine 65 at the beginning of the knotting loop, and histidine 114 that initiates the threading element. It is this tightly packed region and the knotting element that we propose is disrupted with prolonged incubation in the denatured state, and is involved in the observed hysteresis. Interestingly, the disruption is not linked to backbone interactions, but rather to the packing of side chains in this critical region. PMID:26291198

  9. The mechanism by which fish antifreeze proteins cause thermal hysteresis.

    PubMed

    Kristiansen, Erlend; Zachariassen, Karl Erik

    2005-12-01

    Antifreeze proteins are characterised by their ability to prevent ice from growing upon cooling below the bulk melting point. This displacement of the freezing temperature of ice is limited and at a sufficiently low temperature a rapid ice growth takes place. The separation of the melting and freezing temperature is usually referred to as thermal hysteresis, and the temperature of ice growth is referred to as the hysteresis freezing point. The hysteresis is supposed to be the result of an adsorption of antifreeze proteins to the crystal surface. This causes the ice to grow as convex surface regions between adjacent adsorbed antifreeze proteins, thus lowering the temperature at which the crystal can visibly expand. The model requires that the antifreeze proteins are irreversibly adsorbed onto the ice surface within the hysteresis gap. This presupposition is apparently in conflict with several characteristic features of the phenomenon; the absence of superheating of ice in the presence of antifreeze proteins, the dependence of the hysteresis activity on the concentration of antifreeze proteins and the different capacities of different types of antifreeze proteins to cause thermal hysteresis at equimolar concentrations. In addition, there are structural obstacles that apparently would preclude irreversible adsorption of the antifreeze proteins to the ice surface; the bond strength necessary for irreversible adsorption and the absence of a clearly defined surface to which the antifreeze proteins may adsorb. This article deals with these apparent conflicts between the prevailing theory and the empirical observations. We first review the mechanism of thermal hysteresis with some modifications: we explain the hysteresis as a result of vapour pressure equilibrium between the ice surface and the ambient fluid fraction within the hysteresis gap due to a pressure build-up within the convex growth zones, and the ice growth as the result of an ice surface nucleation event at

  10. Hysteresis in Transport Critical-Current Measurements of Oxide Superconductors

    PubMed Central

    Goodrich, L. F.; Stauffer, T. C.

    2001-01-01

    We have investigated magnetic hysteresis in transport critical-current (Ic) measurements of Ag-matrix (Bi,Pb)2Sr2Ca2Cu3O10–x (Bi-2223) and AgMg-matrix Bi2Sr2CaCu2O8+x (Bi-2212) tapes. The effect of magnetic hysteresis on the measured critical current of high temperature superconductors is a very important consideration for every measurement procedure that involves more than one sweep of magnetic field, changes in field angle, or changes in temperature at a given field. The existence of this hysteresis is well known; however, the implications for a measurement standard or interlaboratory comparisons are often ignored and the measurements are often made in the most expedient way. A key finding is that Ic at a given angle, determined by sweeping the angles in a given magnetic field, can be 17 % different from the Ic determined after the angle was fixed in zero field and the magnet then ramped to the given field. Which value is correct is addressed in the context that the proper sequence of measurement conditions reflects the application conditions. The hysteresis in angle-sweep and temperature-sweep data is related to the hysteresis observed when the field is swept up and down at constant angle and temperature. The necessity of heating a specimen to near its transition temperature to reset it to an initial state between measurements at different angles and temperatures is discussed. PMID:27500042

  11. Hysteresis and Back Transitions in Internal Transport Barriers

    NASA Astrophysics Data System (ADS)

    Kim, S. S.; Jhang, Hogun; Terzolo, L.; Kim, J. Y.; Kwon, J. M.; Diamond, P. H.; Malkov, M.; Hahm, T. S.

    2010-11-01

    Understanding and control of the transport barrier formation and back transition are essential to achieve the optimized plasma operation and performance in tokamak plasmas. Back transition dynamics, in particular, is complicated due to the phenomenon of hysteresis, whereby the barrier state persists when the driving power is lowered below the initial threshold value. Here we report new results from theoretical and computational studies of hysteresis in internal transport barrier (ITB) with reversed magnetic shear. A revised version of the global gyrofluid TRB code has been used to study ITG turbulence. ITB formation, back transition, and hysteresis are manifested during slow ramp-ups/downs of the central heating power. Comparisons are made of the similarity/difference in the characteristics of hysteresis when the control parameter is lowered dynamically. The strength of hysteresis is quantified as functions of ion Nusselt number, q-profile shape and lower order rational q surface. In addition to the computational study, an analytical study of a two-field model of pressure and density dynamics is presented for a reversed shear ITB plasma by extending a previous theory that is applied to the edge pedestal.

  12. A Comparison of Longitudinal and Transverse Cross Sections in the p (e,e'K)/Lambda and p(e,e'K)/Sigma Reactions

    SciTech Connect

    Richard Mohring

    1999-10-01

    Jefferson Lab Experiment E93-018 measured kaon electroproduction in hydrogen in two hyperon channels, p(e, e'K{sup +})Lambda and p(e,e'K{sup +})Sigma{sup 0}. Data in both channels were taken at three (3) different values of the virtual photon transverse linear polarization, epsilon, for each of four (4) values of Q{sup 2} = (0.52, 0.75, 1.00, 2.00) GeV{sup 2}. Cross sections averaged over the azimuthal angle, phi, were extracted (i.e., sigma{sub T} + epsilon sigma{sub L}) at each of these twelve points for each hyperon. Rosenbluth separations were performed to separate the longitudinal and transverse production cross sections.

  13. Hysteresis-driven structure formation in biochemical networks

    PubMed

    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

  14. Hysteresis Modeling in Magnetostrictive Materials Via Preisach Operators

    NASA Technical Reports Server (NTRS)

    Smith, R. C.

    1997-01-01

    A phenomenological characterization of hysteresis in magnetostrictive materials is presented. Such hysteresis is due to both the driving magnetic fields and stress relations within the material and is significant throughout, most of the drive range of magnetostrictive transducers. An accurate characterization of the hysteresis and material nonlinearities is necessary, to fully utilize the actuator/sensor capabilities of the magnetostrictive materials. Such a characterization is made here in the context of generalized Preisach operators. This yields a framework amenable to proving the well-posedness of structural models that incorporate the magnetostrictive transducers. It also provides a natural setting in which to develop practical approximation techniques. An example illustrating this framework in the context of a Timoshenko beam model is presented.

  15. Contact Hysteresis and Friction of Alkanethiol SAMs on Au

    SciTech Connect

    Houston, J.E.; Kiely, J.D.

    1998-10-14

    Nanoindentation has been combhed with nanometer-scale friction measurements to identi~ dissipative mechanisms responsible for friction in hexadecanethiol self-assembled monolayer on Au. We have demonstrated that friction is primarily due to viscoelastic relaxations within the films, which give rise to contact hysteresis when deformation rates are within the ranges of 5 and 200 k. We observe that this contact hysteresis increases with exposure to air such that the friction coefficient increases from 0.004 to 0.075 when films are exposed to air for 40 days. Both hysteresis and friction increase with probe speed, and we present a model of friction that characterizes this speed dependence and which also predicts a linear dependence of friction on normal force in thin organic films. Finally, we identify several short-term wear regimes and identify that wear changes dramatically when fdms age.

  16. Origin of J-V Hysteresis in Perovskite Solar Cells.

    PubMed

    Chen, Bo; Yang, Mengjin; Priya, Shashank; Zhu, Kai

    2016-03-01

    High-performance perovskite solar cells (PSCs) based on organometal halide perovskite have emerged in the past five years as excellent devices for harvesting solar energy. Some remaining challenges should be resolved to continue the momentum in their development. The photocurrent density-voltage (J-V) responses of the PSCs demonstrate anomalous dependence on the voltage scan direction/rate/range, voltage conditioning history, and device configuration. The hysteretic J-V behavior presents a challenge for determining the accurate power conversion efficiency of the PSCs. Here, we review the recent progress on the investigation of the origin(s) of J-V hysteresis behavior in PSCs. We discuss the impact of slow transient capacitive current, trapping and detrapping process, ion migrations, and ferroelectric polarization on the hysteresis behavior. The remaining issues and future research required toward the understanding of J-V hysteresis in PSCs will also be discussed. PMID:26886052

  17. 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.

  18. 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.

  19. 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.

  20. Large-scale separation and hysteresis in cascades

    NASA Technical Reports Server (NTRS)

    Rothmayer, A. P.; Smith, F. T.

    1985-01-01

    An approach using a two-dimensional thin aerofoil, allied with the theory of viscous bluff-body separation, is used to study the initial cross-over from massive separation to an attached flow in a single-row unstaggered cascade. Analytic solutions are developed for the limit of small cascade-spacing. From the analytic solutions several interesting features of the cascade are examined, including multiple-solution branches and multiple regions of hysteresis. In addition, numerical results are presented for several selected aerofoils. Some of the aerofoils are found to contain markedly enlarged regions of hysteresis for certain critical cascade spacings.

  1. Modeling of Switching and Hysteresis in Molecular Transport

    NASA Technical Reports Server (NTRS)

    Samanta, Manoj P.; Partridge, Harry (Technical Monitor)

    2002-01-01

    The conventional way of modeling current transport in two and three terminal molecular devices could be inadequate for certain cases involving switching and hysteresis. Here we present an alternate approach. Contrary to the regular way where applied bias directly modulates the conducting energy levels of the molecule, our method introduces a nonlinear potential energy surface varying with the applied bias as a control parameter. A time-dynamics is also introduced properly accounting for switching and hysteresis behavior. Although the model is phenomenological at this stage, we believe any detailed model would contain similar descriptions at its core.

  2. Low hysteresis FeMn-based top spin valve.

    PubMed

    Ustinov, V V; Krinitsina, T P; Milyaev, M A; Naumova, L I; Proglyado, V V

    2012-09-01

    FeMn-based top spin valves Ta/[FeNi/CoFe]/Cu/CoFe/FeMn/Ta with different Cu and FeMn layers thicknesses were prepared by DC magnetron sputtering at room temperature. It was shown that low field hysteresis due to free layer magnetization reversal can be reduced down to (0.1 divided by 0.2) Oe keeping the GMR ratio higher 8% by using both layers thicknesses optimization and non-collinear geometry of magnetoresistance measurements. Dependence of low field hysteresis and GMR ratio on the angle between applied magnetic field and pinning direction are presented. PMID:23035516

  3. A survey on hysteresis modeling, identification and control

    NASA Astrophysics Data System (ADS)

    Hassani, Vahid; Tjahjowidodo, Tegoeh; Do, Thanh Nho

    2014-12-01

    The various mathematical models for hysteresis such as Preisach, Krasnosel'skii-Pokrovskii (KP), Prandtl-Ishlinskii (PI), Maxwell-Slip, Bouc-Wen and Duhem are surveyed in terms of their applications in modeling, control and identification of dynamical systems. In the first step, the classical formalisms of the models are presented to the reader, and more broadly, the utilization of the classical models is considered for development of more comprehensive models and appropriate controllers for corresponding systems. In addition, the authors attempt to encourage the reader to follow the existing mathematical models of hysteresis to resolve the open problems.

  4. Blind loop syndrome

    MedlinePlus

    Blind loop syndrome occurs when digested food slows or stops moving through part of the intestines. This ... The name of this condition refers to the "blind loop" formed by part of the intestine that ...

  5. Seasonal variation in phosphorus concentration-discharge hysteresis inferred from high-frequency in situ monitoring

    NASA Astrophysics Data System (ADS)

    Bieroza, M. Z.; Heathwaite, A. L.

    2015-05-01

    High-resolution in situ total phosphorus (TP), total reactive phosphorus (TRP) and turbidity (TURB) time series are presented for a groundwater-dominated agricultural catchment. Meta-analysis of concentration-discharge (c-q) intra-storm signatures for 61 storm events revealed dominant hysteretic patterns with similar frequency of anti-clockwise and clockwise responses; different determinands (TP, TRP, TURB) behaved similarly. We found that the c-q loop direction is controlled by seasonally variable flow discharge and temperature whereas the magnitude is controlled by antecedent rainfall. Anti-clockwise storm events showed lower flow discharge and higher temperature compared to clockwise events. Hydrological controls were more important for clockwise events and TP and TURB responses, whereas in-stream biogeochemical controls were important for anti-clockwise storm events and TRP responses. Based on the best predictors of the direction of the hysteresis loops, we calibrated and validated a simple fuzzy logic inference model (FIS) to determine likely direction of the c-q responses. We show that seasonal and inter-storm succession in clockwise and anti-clockwise responses corroborates the transition in P transport from a chemostatic to an episodic regime. Our work delivers new insights for the evidence base on the complexity of phosphorus dynamics. We show the critical value of high-frequency in situ observations in advancing understanding of freshwater biogeochemical processes.

  6. 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

  7. Model-Based, Closed-Loop Control of PZT Creep for Cavity Ring-Down Spectroscopy

    PubMed Central

    McCartt, A D; Ognibene, T J; Bench, G; Turteltaub, K W

    2014-01-01

    Cavity ring-down spectrometers typically employ a PZT stack to modulate the cavity transmission spectrum. While PZTs ease instrument complexity and aid measurement sensitivity, PZT hysteresis hinders the implementation of cavity-length-stabilized, data-acquisition routines. Once the cavity length is stabilized, the cavity’s free spectral range imparts extreme linearity and precision to the measured spectrum’s wavelength axis. Methods such as frequency-stabilized cavity ring-down spectroscopy have successfully mitigated PZT hysteresis, but their complexity limits commercial applications. Described herein is a single-laser, model-based, closed-loop method for cavity length control. PMID:25395738

  8. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    PubMed

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application. PMID:27227427

  9. Coupled magnetoelastic theory of magnetic and magnetostrictive hysteresis

    SciTech Connect

    Sablik, M.J. ); Jiles, D.C. . Ames Lab.)

    1993-07-01

    A physical model is developed for the coupling between magnetic and magnetostrictive hysteresis and for the effect of mechanical stress on both types of hysteresis. The Jiles-Atherton-Sablik model for magnetomechanical hysteresis is reviewed and interpreted. In that model, under applied stress, the magnetization is coupled to magnetostriction through the derivative of the magnetostriction with respect to magnetization. The magnetostriction is also a function of the magnetization even in the absence of stress. An expression for the magnetostriction is derived from minimization of the internal energy with respect to strains, which is necessary for mechanical equilibrium. In the case where stress [sigma]/Y, where Y is Young's modulus, and a magnetostrain which goes to zero at saturation ([Delta]E effect). From the magnetostrain, the magnetostriction is obtained, using the convention that magnetostriction is zero in the unmagnetized state. By taking into account fluctuations in the magnetic energy due to hysteresis, one finds that the magnetostriction initially moves to higher values as the magnitude of the flux density B decreases from its extremum value in [lambda] versus B plots. Various numerical cases are evaluated, and the modeling is compared to previous measurements in polycrystalline iron and steel and in terfenol and Ni-Zn ferrites.

  10. Perovskite-Fullerene Hybrid Materials Eliminate Hysteresis In Planar Diodes

    DOE PAGESBeta

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey; et al

    2015-03-31

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite–PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3 antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solarmore » cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.« less

  11. 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.

  12. Causes and implications of colloid and microorganism retention hysteresis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1...

  13. Elastic guides reduce hysteresis effect in Belleville spring package

    NASA Technical Reports Server (NTRS)

    Mc Glashan, W. F., Jr.; Toth, L. R.

    1967-01-01

    Peripheral support guides that elastically flex with the slight breathing on radial displacement during actuation can greatly reduce the hysteresis present in a Belleville spring package. This technique provides a control device that enhances the precision of pressure regulating valves, pressure switches, and vacuum actuators.

  14. Periodic solutions of a forced system with hysteresis.

    NASA Technical Reports Server (NTRS)

    Drew, J. H.

    1972-01-01

    Hysteresis damping arising in an oscillatory system due to the phenomenon of slip damping analyzed by Goodman and Klumpp (1956) is considered. An idealized physical model is proposed, and the existence of certain periodic motions is investigated in a system with small forcing which are near the largest periodic motion in a corresponding unforced system. Periodic solutions of the forced system are obtained.-

  15. Perovskite–fullerene hybrid materials suppress hysteresis in planar diodes

    PubMed Central

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

    2015-01-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite–PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3− antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour. PMID:25953105

  16. Thermodynamics of a general stochastic model of magnetic hysteresis

    NASA Astrophysics Data System (ADS)

    Clatterbuck, D. M.; Morris, J. W., Jr.

    2001-03-01

    The thermodynamics of a general stochastic model of magnetic hysteresis are analyzed and the implications are discussed. The idea of modeling magnetic hysteresis in terms of a single degree of freedom evolving in a random potential was first proposed by Neel and subsequently studied by a number of authors. One difficulty with these models is the need for ad-hoc assumptions about the form of the random potential. Starting with a general stochastic model with no assumptions about the potential, an analysis of the conditions of equilibrium and stability demonstrates that the potential must divide into two components. One term represents the equilibrium behavior, and the other is a random pinning term with average slope of zero. This clarifies some of the past work on hysteresis and the magnetic Barkhausen effect. The thermodynamic analysis also demonstrates that the Jiles-Atherton hysteresis model can be derived from the stochastic model using a specific form of the potential. Research supported by DOE under Contract No. DE-AC03-76SF00098.

  17. 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.

  18. Back-Propagation Operation for Analog Neural Network Hardware with Synapse Components Having Hysteresis Characteristics

    PubMed Central

    Ueda, Michihito; Nishitani, Yu; Kaneko, Yukihiro; Omote, Atsushi

    2014-01-01

    To realize an analog artificial neural network hardware, the circuit element for synapse function is important because the number of synapse elements is much larger than that of neuron elements. One of the candidates for this synapse element is a ferroelectric memristor. This device functions as a voltage controllable variable resistor, which can be applied to a synapse weight. However, its conductance shows hysteresis characteristics and dispersion to the input voltage. Therefore, the conductance values vary according to the history of the height and the width of the applied pulse voltage. Due to the difficulty of controlling the accurate conductance, it is not easy to apply the back-propagation learning algorithm to the neural network hardware having memristor synapses. To solve this problem, we proposed and simulated a learning operation procedure as follows. Employing a weight perturbation technique, we derived the error change. When the error reduced, the next pulse voltage was updated according to the back-propagation learning algorithm. If the error increased the amplitude of the next voltage pulse was set in such way as to cause similar memristor conductance but in the opposite voltage scanning direction. By this operation, we could eliminate the hysteresis and confirmed that the simulation of the learning operation converged. We also adopted conductance dispersion numerically in the simulation. We examined the probability that the error decreased to a designated value within a predetermined loop number. The ferroelectric has the characteristics that the magnitude of polarization does not become smaller when voltages having the same polarity are applied. These characteristics greatly improved the probability even if the learning rate was small, if the magnitude of the dispersion is adequate. Because the dispersion of analog circuit elements is inevitable, this learning operation procedure is useful for analog neural network hardware. PMID:25393715

  19. Back-propagation operation for analog neural network hardware with synapse components having hysteresis characteristics.

    PubMed

    Ueda, Michihito; Nishitani, Yu; Kaneko, Yukihiro; Omote, Atsushi

    2014-01-01

    To realize an analog artificial neural network hardware, the circuit element for synapse function is important because the number of synapse elements is much larger than that of neuron elements. One of the candidates for this synapse element is a ferroelectric memristor. This device functions as a voltage controllable variable resistor, which can be applied to a synapse weight. However, its conductance shows hysteresis characteristics and dispersion to the input voltage. Therefore, the conductance values vary according to the history of the height and the width of the applied pulse voltage. Due to the difficulty of controlling the accurate conductance, it is not easy to apply the back-propagation learning algorithm to the neural network hardware having memristor synapses. To solve this problem, we proposed and simulated a learning operation procedure as follows. Employing a weight perturbation technique, we derived the error change. When the error reduced, the next pulse voltage was updated according to the back-propagation learning algorithm. If the error increased the amplitude of the next voltage pulse was set in such way as to cause similar memristor conductance but in the opposite voltage scanning direction. By this operation, we could eliminate the hysteresis and confirmed that the simulation of the learning operation converged. We also adopted conductance dispersion numerically in the simulation. We examined the probability that the error decreased to a designated value within a predetermined loop number. The ferroelectric has the characteristics that the magnitude of polarization does not become smaller when voltages having the same polarity are applied. These characteristics greatly improved the probability even if the learning rate was small, if the magnitude of the dispersion is adequate. Because the dispersion of analog circuit elements is inevitable, this learning operation procedure is useful for analog neural network hardware. PMID:25393715

  20. Carex opaca (Hermann) P.E. Pothrock & Reznicek (CYPERACEAE) new to North Carolina

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carex opaca (F. J. Hermann) P.E. Rothrock & Reznicek (CYPERACEAE) is reported from two sites in North Carolina. These are the first records of C. opaca from North Carolina and represent easternmost stations for this species in the United States. Previously C. opaca was known from Arkansas, Illino...

  1. Student Programming in the Introductory Physics Course: M.U.P.P.E.T.

    ERIC Educational Resources Information Center

    Redish, Edward F.; Wilson, Jack M.

    Since 1983, the Maryland University Project in Physics and Educational Technology (M.U.P.P.E.T.) has been investigating the implication of including student programming in an introductory physics course for physics majors. Many significant changes can result. One can rearrange some content to be more physically appropriate, include more realistic…

  2. The P.E.A.C.E. Pack: A Computerized Online Assessment of School Bullying

    ERIC Educational Resources Information Center

    Slee, Phillip T.; Mohyla, Jury

    2014-01-01

    School bullying is an international problem with harmful outcomes for those involved. This study describes the design and field testing of an innovative computer-based social learning tool for assessing student perceptions of bullying developed for an Australian intervention program called the P.E.A.C.E. Pack. Students rate their peer group…

  3. P.E.E.R.: Dickinson College's Summer Gown/Town Program for Elementary Children.

    ERIC Educational Resources Information Center

    Boytim, James A.

    Dickinson College has operated the Program for Education, Enrichment, and Recreation (P.E.E.R.) for 66 children ages 7-11 since 1968. The program operates for an 8-week summer session for elementary school children who may benefit from a supervised, structured, small group experience. Swimming instruction is provided along with other sports, arts…

  4. Minor loops modelling with a modified Jiles-Atherton model and comparison with the Preisach model

    NASA Astrophysics Data System (ADS)

    Benabou, A.; Leite, J. V.; Clénet, S.; Simão, C.; Sadowski, N.

    When modelling electrical devices, one has to estimate quite accurately the iron losses for the sake of efficiency. The use of non-sinusoidal electrical sources increases the harmonic content in electrical systems and, consequently, increases significantly the magnetic losses in devices feed by these sources. The harmonic content adds non-centred minor hysteresis loops over the classical major one. The numerical tool used for the material modelling must be able to represent the magnetic behaviour in such conditions. Then, the use of a hysteresis model is the more suited solution, but the chosen model has to take into account correctly the minor loops. The Jiles-Atherton hysteresis model is one of the most employed, due its well-known properties, but it is not able to represent closed minor loops. In this work, we propose a simple approach based on experimental observations and empirical considerations, to improve the representation of minor loops in this model by keeping its simplicity of use and implementation in a FE calculation code. Differently to other approaches found in the literature, the previous knowledge of the magnetic field evolution is not needed. A comparison between measured and calculated curves, as well with the Preisach model, is performed to validate the model.

  5. Loops and trees

    NASA Astrophysics Data System (ADS)

    Caron-Huot, S.

    2011-05-01

    We investigate relations between loop and tree amplitudes in quantum field theory that involve putting on-shell some loop propagators. This generalizes the so-called Feynman tree theorem which is satisfied at 1-loop. Exploiting retarded boundary conditions, we give a generalization to ℓ-loop expressing the loops as integrals over the on-shell phase space of exactly ℓ particles. We argue that the corresponding integrand for ℓ > 2 does not involve the forward limit of any physical tree amplitude, except in planar gauge theories. In that case we explicitly construct the relevant physical amplitude. Beyond the planar limit, abandoning direct integral representations, we propose that loops continue to be determined implicitly by the forward limit of physical connected trees, and we formulate a precise conjecture along this line. Finally, we set up technology to compute forward amplitudes in supersymmetric theories, in which specific simplifications occur.

  6. PREFACE: International Workshop on Multi-Rate Processes and Hysteresis

    NASA Astrophysics Data System (ADS)

    Mortell, Michael P.; O'Malley, Robert E.; Pokrovskii, Alexei; Rachinskii, Dmitrii; Sobolev, Vladimir A.

    2008-07-01

    We are interested in singular perturbation problems and hysteresis as common strongly nonlinear phenomena that occur in many industrial, physical and economic systems. The wording `strongly nonlinear' means that linearization will not encapsulate the observed phenomena. Often these two types of phenomena are manifested for different stages of the same or similar processes. A number of fundamental hysteresis models can be considered as limit cases of time relaxation processes, or admit an approximation by a differential equation which is singular with respect to a particular parameter. However, the amount of interaction between practitioners of theories of systems with time relaxation and systems with hysteresis (and between the `relaxation' and `hysteresis' research communities) is still low, and cross-fertilization is small. In recent years Ireland has become a home for a series of prestigious International Workshops in Singular Perturbations and Hysteresis: International Workshop on Multi-rate Processes and Hysteresis (University College Cork, Ireland, 3-8 April 2006). Proceedings are published in Journal of Physics: Conference Series, volume 55. See further information at http://euclid.ucc.ie/murphys2008.htm International Workshop on Hysteresis and Multi-scale Asymptotics (University College Cork, Ireland, 17-21 March 2004). Proceedings are published in Journal of Physics: Conference Series, volume 22. See further information at http://euclid.ucc.ie/murphys2006.htm International Workshop on Relaxation Oscillations and Hysteresis (University College Cork, Ireland, 1-6 April 2002). The related collection of invited lectures, was published as a volume Singular Perturbations and Hysteresis, SIAM, Philadelphia, 2005. See further information at http://euclid.ucc.ie/hamsa2004.htm International Workshop on Geometrical Methods of Nonlinear Analysis and Semiconductor Laser Dynamics (University College Cork, Ireland, 5-5 April 2001). A collection of invited papers has been

  7. Laminated BEAM loops

    NASA Astrophysics Data System (ADS)

    Danisch, Lee A.

    1996-10-01

    BEAM sensors include treated loops of optical fiber that modulate optical throughput with great sensitivity and linearity, in response to curvature of the loop out of its plane. This paper describes BEAM sensors that have two loops treated in opposed fashion, hermetically sealed in flexible laminations. The sensors include an integrated optoelectronics package that extracts curvature information from the treated portion of the loops while rejecting common mode errors. The laminated structure is used to sense various parameters including displacement, force, pressure, flow, and acceleration.

  8. Observational Evidence for Loop-Loop Interaction

    NASA Astrophysics Data System (ADS)

    Guiping, W.; Guangli, H.; Yuhua, T.; Aoao, X.

    2004-01-01

    Through analysis of the data including the hard x-ray(BASTE) microwave(NoRP) and magnetogram(MDI from SOHO) as well as the images of soft x-ray(YHKOH) and EIT(SOHO) on Apr. 151998 solar flare in the active region 8203(N30W12) we found: (1) there are similar quasi period oscillation in the profile of hard x-ray flux (25-5050-100keV) and microwave flux(1GHz) with duration of 85+/-25s every peak includes two sub-peak structures; (2) in the preheat phase of the flare active magnetic field changes apparently and a s-pole spot emerges ; (3) several EIT and soft x-ray loops exist and turn into bright . All of these may suggest that loop-loop interaction indeed exist. Through reconnection the electrons may be accelerated and the hard x-ray and microwave emission take place.

  9. Linear Stepper Actuation Driving Drop Resonance and Modifying Hysteresis.

    PubMed

    Katariya, Mayur; Huynh, So Hung; McMorran, Darren; Lau, Chun Yat; Muradoglu, Murat; Ng, Tuck Wah

    2016-08-23

    In this work, 2 μL water drops are placed on substrates that are created to have a circular hydrophilic region bounded by superhydrophobicity so that they exhibit high contact angles. When the substrate is translated by a linear stepper actuator, the random force components present in the actuator are shown to cause the drop to rock resonantly. When the substrate is translated downward at inclination angles of up to 6° with respect to the horizontal, the contact angle hysteresis increases progressively to a limiting condition. When the substrate is moved up at inclined angles, alternatively, the contact angle hysteresis increases initially to the limiting condition before it is progressively restored to its static state. These behaviors are accounted for by the reversible micro-Cassie to Wenzel wetting state transformations that are made possible by the hierarchical microscale and nanoscale structures present in the superhydrophobic regions. PMID:27479030

  10. Voltage hysteresis of lithium ion batteries caused by mechanical stress.

    PubMed

    Lu, Bo; Song, Yicheng; Zhang, Qinglin; Pan, Jie; Cheng, Yang-Tse; Zhang, Junqian

    2016-02-01

    The crucial role of mechanical stress in voltage hysteresis of lithium ion batteries in charge-discharge cycles is investigated theoretically and experimentally. A modified Butler-Volmer equation of electrochemical kinetics is proposed to account for the influence of mechanical stresses on electrochemical reactions in lithium ion battery electrodes. It is found that the compressive stress in the surface layer of active materials impedes lithium intercalation, and therefore, an extra electrical overpotential is needed to overcome the reaction barrier induced by the stress. The theoretical formulation has produced a linear dependence of the height of voltage hysteresis on the hydrostatic stress difference between lithiation and delithiation, under both open-circuit conditions and galvanostatic operation. Predictions of the electrical overpotential from theoretical equations agree well with the experimental data for thin film silicon electrodes. PMID:26799574

  11. 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.

  12. 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.

  13. Efficiency of Hysteresis Rods in Small Spacecraft Attitude Stabilization

    PubMed Central

    Farrahi, Assal; Sanz-Andrés, Ángel

    2013-01-01

    A semiempirical method for predicting the damping efficiency of hysteresis rods on-board small satellites is presented. It is based on the evaluation of dissipating energy variation of different ferromagnetic materials for two different rod shapes: thin film and circular cross-section rods, as a function of their elongation. Based on this formulation, an optimum design considering the size of hysteresis rods, their cross section shape, and layout has been proposed. Finally, the formulation developed was applied to the case of four existing small satellites, whose corresponding in-flight data are published. A good agreement between the estimated rotational speed decay time and the in-flight data has been observed. PMID:24501579

  14. Attachment/detachment hysteresis of fiber-based magnetic grabbers.

    PubMed

    Gu, Yu; Kornev, Konstantin G

    2014-04-28

    We developed an experimental protocol to analyze the behaviour of a model fiber-based magnetic grabber. A fiber is vertically suspended and fixed to the substrate by its upper end. A magnetic droplet is attached to the free end of the fiber and when a permanent magnet approaches the droplet, the fiber is forced to bow and finally jumps to the magnet. It appears that one can flex the micro-fibers by very small micro or even nano-Newton forces. Using this setup, we discovered a hysteresis of fiber attachment/detachment: the pathway of the fiber jumping to and off the magnet depends on the distance between the magnet and the clamped end. This phenomenon was successfully explained by the Euler-Benoulli model of an elastic beam. The observed hysteresis of fiber attachment/detachment was attributed to the multiple equilibrium configurations of the fiber tip placed in a dipole-type magnetic field. PMID:24668160

  15. Method of thermal strain hysteresis reduction in metal matrix composites

    NASA Technical Reports Server (NTRS)

    Dries, Gregory A. (Inventor); Tompkins, Stephen S. (Inventor)

    1987-01-01

    A method is disclosed for treating graphite reinforced metal matrix composites so as to eliminate thermal strain hysteresis and impart dimensional stability through a large thermal cycle. The method is applied to the composite post fabrication and is effective on metal matrix materials using graphite fibers manufactured by both the hot roll bonding and diffusion bonding techniques. The method consists of first heat treating the material in a solution anneal oven followed by a water quench and then subjecting the material to a cryogenic treatment in a cryogenic oven. This heat treatment and cryogenic stress reflief is effective in imparting a dimensional stability and reduced thermal strain hysteresis in the material over a -250.degree. F. to +250.degree. F. thermal cycle.

  16. Modeling of sharp change in magnetic hysteresis behavior of electrical steel at small plastic deformation

    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.

  17. Modeling of sharp change in magnetic hysteresis behavior of electrical steel at small plastic deformation

    SciTech Connect

    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.

  18. A new paradigm for modelling hysteresis in macroeconomic flows

    NASA Astrophysics Data System (ADS)

    Cross, R.; McNamara, H.; Pokrovskii, A.; Rachinskii, D.

    2008-02-01

    Macroeconomic processes are often conceptualised as “flows”, and analogies are drawn with physical flow processes. Most economic processes, however, carry inherent irreversibility, a fact which these analogies neglect. A better metaphor for economic flows is suggested, involving flows through porous media. This new conceptual framework incorporates important features such as irreversibility and heterostasis through the use of hysteresis. A simple example model is derived, which may be used to derive qualitative results.

  19. Novel thermal hysteresis proteins from low temperature basidiomycete, Coprinus psychromorbidus.

    PubMed

    Hoshino, T; Kiriaki, M; Nakajima, T

    2003-01-01

    The low temperature basidiomycete, Coprinus psychromorbidus, produced three kinds of thermal hysteresis proteins (THPs) in the extracellular space. Molecular mass of purified fungal THPs were approximately 23 kDa, respectively, however those fungal THPs had different N-terminal amino acid sequences. Those fungal THPs formed ice crystals resembling "stone Age arrow head". These observations indicate that fungal THPs did not form hexagonal ice crystals to inhibit its growth. PMID:12908023

  20. 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.

  1. 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.

  2. Robust homoclinic orbits in planar systems with Preisach hysteresis operator

    NASA Astrophysics Data System (ADS)

    Pimenov, Alexander; Rachinskii, Dmitrii

    2016-06-01

    We construct examples of robust homoclinic orbits for systems of ordinary differential equations coupled with the Preisach hysteresis operator. Existence of such orbits is demonstrated for the first time. We discuss a generic mechanism that creates robust homoclinic orbits and a method for finding them. An example of a homoclinic orbit in a population dynamics model with hysteretic response of the prey to variations of the predator is studied numerically.

  3. Tuning size and thermal hysteresis in bistable spin crossover nanoparticles.

    PubMed

    Galán-Mascarós, José Ramón; Coronado, Eugenio; Forment-Aliaga, Alicia; Monrabal-Capilla, María; Pinilla-Cienfuegos, Elena; Ceolin, Marcelo

    2010-06-21

    Nanoparticles of iron(II) triazole salts have been prepared from water-organic microemulsions. The mean size of the nanoparticles can be tuned down to 6 nm in diameter, with a narrow size distribution. A sharp spin transition from the low spin (LS) to the high spin (HS) state is observed above room temperature, with a 30-40-K-wide thermal hysteresis. The same preparation can yield second generation nanoparticles containing molecular alloys by mixing triazole with triazole derivatives, or from metallic mixtures of iron(II) and zinc(II). In these nanoparticles of 10-15 nm, the spin transition "moves" towards lower temperatures, reaching a 316 K limit for the cooling down transition and maintaining a thermal hysteresis over 15-20-K-wide. The nanoparticles were characterized by dynamic light scattering, TEM, and AFM, after deposition on gold or silicon surfaces. The spin transition was characterized by magnetic susceptibility measurements and EXAFS (in solid samples after solvent removal) and also by the color change between the LS (violet) and HS (colorless) states in an organic solvent suspension. The discovery of bistable magnetic nanoparticles of 6 nm with a wide thermal hysteresis above room temperature showcases the actual possibilities of spin crossover materials for nanotechnological applications. PMID:20503990

  4. Hysteresis of the resonance frequency of magnetostrictive bending cantilevers

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard

    2015-05-01

    Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.

  5. 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.

  6. Oscillating hysteresis in the q-neighbor Ising model.

    PubMed

    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

  7. Using stormwater hysteresis to characterize karst spring discharge.

    PubMed

    Toran, Laura; Reisch, Chad E

    2013-01-01

    Discharge from karst springs contains a mixture of conduit and matrix water, but the variations in groundwater mixing are poorly known. Storm events present an opportunity to try to map flow components because water entering during storms is more dilute and provides a tracer as it mixes with pre-event water along the flowpath from the recharge area to discharge at a spring. We used hysteresis plots of Mg/Ca ratios in a spring in the Cumberland Valley of Pennsylvania to map conduit (higher Ca) vs. diffuse (higher Mg) sources of recharge. We observed two types of temporal heterogeneity: within a storm event and from storm to storm. The timing of the variation in Mg/Ca suggested sources of mixing waters. An increase in the Mg/Ca ratio at the beginning of some storms while conductivity declined suggested diffuse recharge through the epikarst. The rapid changes in Mg/Ca ratios for low-intensity events probably occurred as the rainfall waxed and waned and illustrate that a variety of flowpaths are available at this spring because additional flushing of Mg occurred. In contrast, the conductivity hysteresis began with dilute water initially and rotation was similar from storm to storm. Hysteresis plots of the Mg/Ca ratio have the potential of revealing more of the complexity in discharge than conductivity alone. A better understanding of flow components in karst is needed to protect these aquifers as a groundwater resource. PMID:22974348

  8. The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors

    NASA Astrophysics Data System (ADS)

    Narod, B. B.

    2014-06-01

    available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which, are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B-H loop curvature (d2B/dH2). The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies fluxgate signal. B-H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire fluxgate signal with reduced noise.

  9. The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors

    NASA Astrophysics Data System (ADS)

    Narod, B. B.

    2014-09-01

    available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring-core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B - H loop curvature [d2B/dH2]. The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies the fluxgate signal. B - H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire the fluxgate signal with reduced noise.

  10. High temperature stress-induced ``double loop-like'' phase transitions in Bi-based perovskites

    NASA Astrophysics Data System (ADS)

    Webber, K. G.; Zhang, Y.; Jo, Wook; Daniels, J. E.; Rödel, J.

    2010-07-01

    Polycrystalline 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 samples were tested under uniaxial mechanical compression at various temperatures in the vicinity of the polar tetragonal to nonpolar tetragonal phase boundary. They are shown to display double loop-like stress-strain behavior, marked by a closed ferroelastic hysteresis loop. Thus, it forms a mechanical analog to the polarization-electric field hysteresis behavior of barium titanate above the Curie temperature. As temperature is increased there is an apparent loss of macroscopically observable ferroelasticity, despite the persistence of tetragonality. Macroscopic experimental results are discussed in conjunction with temperature-dependent and stress-dependent high-energy x-ray diffraction data. This reveals a phase transition below the Curie temperature, marked by a discontinuous change in lattice parameters and octahedral tilting during compressive mechanical loading.

  11. Development of a portable mechanical hysteresis measurement and imaging system for impact characterization in honeycomb sandwich structures

    SciTech Connect

    Barnard, Daniel J.; Hsu, David K.

    2011-06-23

    Honeycomb sandwich materials are commonly used for aero-structures, but because the outer skins are typically thin, 2-10 plys, the structures are susceptible to impact damage. NDI methods such as tap tests, bond testers and TTU ultrasound are successfully deployed to find impact damage, but identifying the type/degree of damage is troublesome. As the type/degree of impact damage guides decisions by the maintenance, repair and overhaul (MRO) community regarding repair, the ability to characterize impacts is of interest. Previous work demonstrated that additional impact characterization may be gleaned from hysteresis loop area, as determined from an out-of-plane load-vs-displacement plot, where this parameter shows a correlation with impact energy. This presentation reports on current work involving the development of a portable hysteresis measurement and imaging system based on an instrumented tapper. Data processing and analysis methods that allow production of the load/displacement data from a single accelerometer are discussed, with additional reporting of tests of software to automatically vary pixel size during scanning to decrease C-scans inspection time.

  12. Development of a Portable Mechanical Hysteresis Measurement and Imaging System for Impact Characterization in Honeycomb Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Barnard, Daniel J.; Hsu, David K.

    2011-06-01

    Honeycomb sandwich materials are commonly used for aero-structures, but because the outer skins are typically thin, 2-10 plys, the structures are susceptible to impact damage. NDI methods such as tap tests, bond testers and TTU ultrasound are successfully deployed to find impact damage, but identifying the type/degree of damage is troublesome. As the type/degree of impact damage guides decisions by the maintenance, repair and overhaul (MRO) community regarding repair, the ability to characterize impacts is of interest. Previous work demonstrated that additional impact characterization may be gleaned from hysteresis loop area, as determined from an out-of-plane load-vs-displacement plot, where this parameter shows a correlation with impact energy. This presentation reports on current work involving the development of a portable hysteresis measurement and imaging system based on an instrumented tapper. Data processing and analysis methods that allow production of the load/displacement data from a single accelerometer are discussed, with additional reporting of tests of software to automatically vary pixel size during scanning to decrease C-scans inspection time.

  13. Hysteresis of the Annual Exchange Circulation in the Tampa Bay Estuary

    NASA Astrophysics Data System (ADS)

    Meyers, S. D.; Wilson, M.; Luther, M. E.

    2014-12-01

    A nonlinear relation between the salinity field and the subtidal exchange circulation in the Tampa Bay estuary is demonstrated using 1999-2011 measurements of river discharge, salinity and velocity. These data are binned and averaged to form mean monthly values of freshwater input Q, axial (vertical) salinity gradient ΔS (ΔzS), and subtidal vertical shear σ, respectively. These interrelated quantities are found to cycle through three dynamical regimes. The first regime (January to May/June) is a vertically well-mixed state (ΔzS≈0) when Q is low and a complex relation between ΔS and σ occurs. This time period has high ΔzS with an estimated gradient Richardson number Ri ~0.25. A value of Ri > 0.25 is usually stably stratified. Regimes II and III are both partially mixed states and both show a near-linear relation σ=cΔS+c0. Regime II (July-Sept) is characterized by rapidly increasing Q, high ΔS, c=-0.053 km psu-1s-1 and Ri~0.6. The third regime (Oct-Dec) has low Q, and includes high to minimal ΔS, relatively high ΔS, c=-0.011 km psu-1s-1 and Ri ~0.4. This asymmetric annual cycle generates hysteresis in the exchange circulation relative to the axial salinity gradient where σ is multi-valued with regard to ΔS, forming a loop in state space. The loop forms because the σ developed during II persists through III even when the original source of its formation (ΔS) has declined to minimal levels. We hypothesize this large Richardson number during III suppresses vertical mixing of momentum and allows the exchange circulation to maintain higher values.

  14. Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

    NASA Astrophysics Data System (ADS)

    Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

    2015-11-01

    Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

  15. Soft-x-ray magneto-optical Kerr effect and element-specific hysteresis measurement

    SciTech Connect

    Kortright, J.B.; Rice, M.

    1997-04-01

    Interest in the utilization of x-ray magneto-optical properties to provide element-specific magnetic information, combined with recent development of tunable linear polarizers for spectroscopic polarization measurement, have led the authors to the study of magneto-optical rotation (MOR) near core levels of magnetic atoms in magnetic multilayer and alloy films. Their initial observation of Faraday rotation (in transmission) demonstrated that for Fe MOR is easily measured and is larger at its L{sub 3} resonance than in the near-visible spectral regions. This work also demonstrated that the spectroscopic behavior of the MOR signal in transmission, resulting from the differential reaction of left- and right-circular components of a linearly polarized beam, is related to the magnetic circular dichroism (MCD), or differential absorption, as expected by a Kramers-Kronig transformation. Thus MCD measurements using circular polarization and MOR measurements using linear polarization can provide complementary, and in some cases equivalent, information. On beamline 6.3.2 the authors have begun to investigate soft x-ray MOR in the reflection geometry, the x-ray magneto-optic Kerr effect (XMOKE). Early measurements have demonstrated the ability to measure element-specific hysteresis loops and large rotations compared to analogous near-visible measurements. The authors are investigating the spectral dependence of the XMOKE signal, and have initiated systematic materials studies of sputter-deposited films of Fe, Fe{sub x}Cr{sub 1{minus}x} alloys, and Fe/Cr multilayers.

  16. Application of the Preisach and Jiles-Atherton models to the simulation of hysteresis in soft magnetic alloys

    NASA Astrophysics Data System (ADS)

    Pasquale, M.; Bertotti, G.; Jiles, D. C.; Bi, Y.

    1999-04-01

    This article describes the advances in unification of model descriptions of hysteresis in magnetic materials and demonstrates the equivalence of two widely accepted models, the Preisach (PM) and Jiles-Atherton (JA) models. Recently it was shown that starting from general energy relations, the JA equation for a loop branch can be derived from PM. The unified approach is here applied to the interpretation of magnetization measured in nonoriented Si-Fe steels with variable grain size , and also in as-cast and annealed Fe amorphous alloys. In the case of NO Fe-Si, the modeling parameter k defined by the volume density of pinning centers is such that k≈A+B/, where the parameters A and B are related to magnetocrystalline anisotropy and grain texture. The value of k in the amorphous alloys can be used to estimate the microstructural correlation length playing the role of effective grain size in these materials.

  17. Matrix and size effects on the appearance of the thermal hysteresis in 2D spin crossover nanoparticles

    NASA Astrophysics Data System (ADS)

    Linares, Jorge; Jureschi, Catalin-Maricel; Boulmaali, Ayoub; Boukheddaden, Kamel

    2016-04-01

    The Ising-like model is used to simulate the thermal behavior of a 2D spin crossover (SC) nanoparticle embedded in a matrix, which affects the ligand field at its surface. First, we discuss the standard case of the isolated nanoparticle, and in the second part we consider the effect of the interaction between edge molecules and their local environment. We found that in the case of an isolated SC nanoparticle presenting a gradual spin transition, the matrix effect may drive a first-order spin transition accompanied with a hysteresis loop. An in-depth analysis of the physical mechanism underlying this unusual property is performed, leading to build up the system's phase diagram which clarifies the conditions of appearance of the first-order transition in the current 2D SC nanoparticles as function of their size and the strength of their interaction with their immediate environment.

  18. Thermal power loops

    NASA Technical Reports Server (NTRS)

    Gottschlich, Joseph M.; Richter, Robert

    1991-01-01

    The concept of a thermal power loop (TPL) to transport thermal power over relatively large distances is presented as an alternative to heat pipes and their derivatives. The TPL is compared to heat pipes, and capillary pumped loops with respect to size, weight, conservation of thermal potential, start-up, and 1-g testing capability. Test results from a proof of feasibility demonstrator at the NASA JPL are discussed. This analysis demonstrates that the development of specific thermal power loops will result in substantial weight and cost savings for many spacecraft.

  19. Natively Unstructured Loops Differ from Other Loops

    PubMed Central

    Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard

    2007-01-01

    Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%–70% of all worm proteins observed to have more than seven protein–protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long

  20. Superfluidity and mean-field energy loops: Hysteretic behavior in Bose-Einstein condensates

    SciTech Connect

    Mueller, Erich J.

    2002-12-01

    We present a theory of hysteretic phenomena in Bose gases, using superfluidity in one-dimensional rings and in optical lattices as primary examples. Through this study we are able to give a physical interpretation of swallow-tail loops recently found by many authors in the mean-field energy structure of trapped atomic gases. These loops are a generic sign of hysteresis, and in the present context are an indication of superfluidity. We have also calculated the rate of decay of metastable current-carrying states due to quantum fluctuations.

  1. Introduction to Loop Heat Pipes

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2015-01-01

    This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.

  2. 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.

  3. Hysteresis phenomenon in the galloping oscillation of a square cylinder

    NASA Astrophysics Data System (ADS)

    Luo, S. C.; Chew, Y. T.; Ng, Y. T.

    2003-08-01

    It is well known that a square cylinder with one side normal to a uniform stream will gallop when a critical flow velocity is exceeded. It is also quite well known that there is a hysteresis phenomenon in the variation of the cylinder's galloping amplitude with the flow velocity. However, little is known about the cause of this hysteresis phenomenon, and the objective of this paper is to study it more closely. In the present study, flow over a stationary square cylinder at different angle of attack (/α) and at Reynolds number (Re) of 250 and 1000 was investigated numerically by using a 2-D hybrid vortex computation scheme. The study reveals that the well known point of inflection which exists in the side force (Cy) versus /α plots at high Reynolds number only occurs at Re=1000, /α=4° in the present numerical simulation. Nonlinear analysis further reveals that this point of inflection is the cause of the hysteresis phenomenon. By further analysing the computed flow field, it is noted that at Re=1000, /α=4°, intermittent flow reattachment takes place at alternate vortex shedding cycle on one side of the cylinder. This results in larger side force fluctuation, and it is conjectured that such large side force fluctuation affects the increasing trend of the side force with angle of attack, resulting in the point of inflection reported earlier. The above-mentioned alternate cycle flow reattachment was much less prominent at /α=2° and 6° (Re=1000), and was not observed at Re=250. Finally, dye flow visualization was carried out in a recirculating water tunnel and the results at Re=1000 confirms the existence of the intermittent flow reattachment. However, in the experiment, flow reattachment does not take place in a very regular alternate cycle manner as in the computation. Instead, it occurs intermittently, possibly due to three-dimensional effects in real flow.

  4. 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.

  5. 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.

  6. Effect of contact angle hysteresis on moving liquid film integrity.

    NASA Technical Reports Server (NTRS)

    Simon, F. F.; Hsu, Y. Y.

    1972-01-01

    A study was made of the formation and breakdown of a water film moving over solid surfaces (teflon, lucite, stainless steel, and copper). The flow rate associated with film formation was found to be higher than the flow rate at which film breakdown occurred. The difference in the flow rates for film formation and film breakdown was attributed to contact angle hysteresis. Analysis and experiment, which are in good agreement, indicated that film formation and film breakdown are functions of the advancing and receding angles, respectively.

  7. Internal hysteresis experienced on a high pressure syn gas compressor

    NASA Technical Reports Server (NTRS)

    Zeidan, F. Y.

    1984-01-01

    A vibration instability phenomenon experienced in operating high pressure syn gas centrifugal compressors in two ammonia plants is described. The compressors were monitored by orbit and spectrum analysis for changes from baseline readings. It is found that internal hysteresis was the major destabilizing force; however, the problem was further complicated by seal lockup at the suction end of the compressor. A coupling lockup problem and a coupling fit problem, which frettage of the shaft, are also considered as contributors to the self excited vibrations.

  8. Effect of contact angle hysteresis on moving liquid film integrity

    NASA Technical Reports Server (NTRS)

    Simon, F. F.; Hsu, Y. Y.

    1972-01-01

    A study was made of the formation and breakdown of a water film moving over solid surfaces (teflon, lucite, stainless steel, and copper). The flow rate associated with film formation was found to be higher than the flow rate at which film breakdown occurred. The difference in the flow rates for film formation and film breakdown was attributed to contact angle hysteresis. Analysis and experiment, which are in good agreement, indicated that film formation and film breakdown are functions of the advancing and receding angles, respectively.

  9. Traffic jams and hysteresis in driven one-dimensional systems

    NASA Astrophysics Data System (ADS)

    Braun, O. M.; Hu, B.; Filippov, A.; Zeltser, A.

    1998-08-01

    The driven underdamped chain of anharmonically interacting atoms in the sinusoidal external potential is studied. It is shown that due to the interatomic interaction the system exhibits hysteresis for any nonzero rate of changing of the dc driving force. Before the transition to the running state the system passes through the traffic-jam inhomogeneous state. The system behavior is explained with the help of two simple models, the discrete lattice-gas model with two states of atoms, and the continuum mean-field model based on the Fokker-Planck equation.

  10. Long-term soil moisture variability from a new P-E water budget method

    NASA Astrophysics Data System (ADS)

    Zeng, N.; Yoon, J.; Mariotti, A.; Swenson, S. C.

    2006-05-01

    Basin-scale soil moisture is traditionally estimated using either land-surface model forced by observed meteorological variables or atmospheric moisture convergence from atmospheric analysis and observed runoff. Interannual variability from such methods suffer from major uncertainties due to the sensitivity to small imperfections in the land-surface model or the atmospheric analysis. Here we introduce a novel P-E method in estimating basin-scale soil moisture, or more precisely apparent land water storage (AWS). The key input variables are observed precipitation and runoff, and reconstructed evaporation. We show the results for the tropics using the example of the Amazon basin. The seasonal cycle of diagnosed soil moisture over the Amazon is about 200mm, compares favorably with satellite estimate from the GRACE mission, thus lending confidence both in this method and the usefulness of space gravity based large-scale soil moisture estimate. This is about twice as large as estimates from several traditional methods, suggesting that current models tend to under estimate the soil moisture variability. One of the advantage of the P-E method is to retrive long-term variability of the basin-scale soil moisture (including interannual and decadal time scales), which can provide valuable information to understand climate variability and to predict future climate condition. However, validation on reconstructed evaporation is very difficult due to lack of observation. The interannual variability in AWS in the Amazon basin is about 150mm, also consistent with GRACE data, but much larger than model results. We also apply this P-E method to the midlatitude Mississippi basin and discuss the impact of major 20th century droughts such as the dust bowl period on the long-term soil moisture variability. The results suggest the existence of soil moisture memories on decadal time scales, significantly longer than typically assumed seasonal timescales.

  11. Tuning the hysteresis voltage in 2D multilayer MoS2 FETs

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Zheng, Zhouming; Guo, Junjie

    2016-10-01

    The hysteresis tuning is of great significance before the two-dimensional (2D) molybdenum disulfide (MoS2) field-effect transistors (FETs) can be practically used in the next-generation nanoelectronic devices. In this paper, a simple and effective annealing method was developed to tune the hysteresis voltage in 2D MoS2 transistors. It was found that high temperature (175 °C) annealing in air could increase the hysteresis voltage from 8.0 V (original device) to 28.4 V, while a next vacuum annealing would reduce the hysteresis voltage to be only 2.0 V. An energyband diagram model based on electron trapping/detrapping due to oxygen adsorption is proposed to understand the hysteresis mechanism in multilayer MoS2 FET. This simple method for tuning the hysteresis voltage of MoS2 FET can make a significant step toward 2D nanoelectronic device applications.

  12. On the 2D-transition, hysteresis and thermodynamic equilibrium of Kr adsorption on a graphite surface.

    PubMed

    Diao, Rui; Fan, Chunyan; Do, D D; Nicholson, D

    2015-12-15

    The adsorption and desorption of Kr on graphite at temperatures in the range 60-88K, was systematically investigated using a combination of several simulation techniques including: Grand Canonical Monte Carlo (GCMC), Canonical kinetic-Monte Carlo (C-kMC) and the Mid-Density Scheme (MDS). Particular emphasis was placed on the gas-solid, gas-liquid and liquid-solid 2D phase transitions. For temperatures below the bulk triple point, the transition from a 2D-liquid-like monolayer to a 2D-solid-like state is manifested as a sub-step in the isotherm. A further increase in the chemical potential leads to another rearrangement of the 2D-solid-like state from a disordered structure to an ordered structure that is signalled by (1) another sub-step in the monolayer region and (2) a spike in the plot of the isosteric heat versus density at loadings close to the dense monolayer coverage concentration. Whenever a 2D transition occurs in a grand canonical isotherm it is always associated with a hysteresis, a feature that is not widely recognised in the literature. We studied in details this hysteresis with the analysis of the canonical isotherm, obtained with C-kMC, which exhibits a van der Waals (vdW) type loop with a vertical segment in the middle. We complemented the hysteresis loop and the vdW curve with the analysis of the equilibrium transition obtained with the MDS, and found that the equilibrium transition coincides exactly with the vertical segment of the C-kMC isotherm, indicating the co-existence of two phases at equilibrium. We also analysed adsorption at higher layers and found that the 2D-coexistence is also observed, provided that the temperature is well below the triple point. Finally the 2D-critical temperatures were obtained for the first three layers and they are in good agreement with the experimental data in the literature. PMID:26364074

  13. Magnetoresistance hysteresis in granular HTSCs as a manifestation of the magnetic flux trapped by superconducting grains in YBCO + CuO composites

    SciTech Connect

    Balaev, D. A. Gokhfeld, D. M.; Dubrovskii, A. A.; Popkov, S. I.; Shaikhutdinov, K. A.; Petrov, M. I.

    2007-12-15

    Hysterestic behavior of the magnetoresistance of granular HTSCs and its interaction with the magnetic hysteresis are studied by measuring magnetoresistance R(H) and critical current I{sub c}(H) of composites formed by HTSC Y{sub 0.75}Lu{sub 0.25}Ba{sub 2}Cu{sub 3}O{sub 7} and CuO. A network of Josephson junctions is formed in such composites, in which the nonsuperconducting component plays the role of barriers between HTSC grains. Hysteretic dependences R(H) of magnetoresistance are studied in a wide range of transport current density j and are analyzed in the framework of the two-level model of a granular superconductor, in which dissipation takes place in the Josephson medium and the magnetic flux can be pinned both in grains and in the Josephson medium. The interrelation between the hysteresis of critical current I{sub c}(H) and the evolution of the hysterestic dependence R(H) of the magnetoresistance upon transport current variation is demonstrated experimentally. The effect of the magnetic past history on the hysteretic behavior of R(H) and the emergence of a segment with a negative magnetoresistance are analyzed. It is shown for the first time that the R(H) dependences are characterized by a parameter that is independent of the transport current, viz., the width of the R(H) hysteresis loop.

  14. Hysteresis-free and submillisecond-response polymer network liquid crystal.

    PubMed

    Lee, Yun-Han; Gou, Fangwang; Peng, Fenglin; Wu, Shin-Tson

    2016-06-27

    We demonstrate a polymer network liquid crystal (PNLC) with negligible hysteresis while keeping submillisecond response time. By doping about 1% dodecyl acrylate (C12A) into the liquid crystal/monomer precursor, both hysteresis and residual birefringence are almost completely eliminated. The operating voltage and scattering properties remain nearly intact, but the tradeoff is enhanced double relaxation. This hysteresis-free PNLC should find applications in spatial light modulators, laser beam control, and optical communications in infrared region. PMID:27410631

  15. Hysteresis zone or locus - Aerodynamic of bulbous based bodies at low speeds

    NASA Technical Reports Server (NTRS)

    Covert, E. E.

    1979-01-01

    Experimental data are presented which seem to suggest that a well-defined hysteresis locus on bulbous based bodies at low speeds does not exist. Instead, if the experiment is repeated several times, the entire hysteresis region seems to fill with data rather than trace out a specific hysteresis locus. Data obtained on an oscillating model even at low reduced frequencies may be well defined but when applied to arbitrary motion lead to less accurate results than desired.

  16. pE-DB: a database of structural ensembles of intrinsically disordered and of unfolded proteins.

    PubMed

    Varadi, Mihaly; Kosol, Simone; Lebrun, Pierre; Valentini, Erica; Blackledge, Martin; Dunker, A Keith; Felli, Isabella C; Forman-Kay, Julie D; Kriwacki, Richard W; Pierattelli, Roberta; Sussman, Joel; Svergun, Dmitri I; Uversky, Vladimir N; Vendruscolo, Michele; Wishart, David; Wright, Peter E; Tompa, Peter

    2014-01-01

    The goal of pE-DB (http://pedb.vib.be) is to serve as an openly accessible database for the deposition of structural ensembles of intrinsically disordered proteins (IDPs) and of denatured proteins based on nuclear magnetic resonance spectroscopy, small-angle X-ray scattering and other data measured in solution. Owing to the inherent flexibility of IDPs, solution techniques are particularly appropriate for characterizing their biophysical properties, and structural ensembles in agreement with these data provide a convenient tool for describing the underlying conformational sampling. Database entries consist of (i) primary experimental data with descriptions of the acquisition methods and algorithms used for the ensemble calculations, and (ii) the structural ensembles consistent with these data, provided as a set of models in a Protein Data Bank format. PE-DB is open for submissions from the community, and is intended as a forum for disseminating the structural ensembles and the methodologies used to generate them. While the need to represent the IDP structures is clear, methods for determining and evaluating the structural ensembles are still evolving. The availability of the pE-DB database is expected to promote the development of new modeling methods and leads to a better understanding of how function arises from disordered states. PMID:24174539

  17. pE-DB: a database of structural ensembles of intrinsically disordered and of unfolded proteins

    PubMed Central

    Varadi, Mihaly; Kosol, Simone; Lebrun, Pierre; Valentini, Erica; Blackledge, Martin; Dunker, A. Keith; Felli, Isabella C.; Forman-Kay, Julie D.; Kriwacki, Richard W.; Pierattelli, Roberta; Sussman, Joel; Svergun, Dmitri I.; Uversky, Vladimir N.; Vendruscolo, Michele; Wishart, David; Wright, Peter E.; Tompa, Peter

    2014-01-01

    The goal of pE-DB (http://pedb.vib.be) is to serve as an openly accessible database for the deposition of structural ensembles of intrinsically disordered proteins (IDPs) and of denatured proteins based on nuclear magnetic resonance spectroscopy, small-angle X-ray scattering and other data measured in solution. Owing to the inherent flexibility of IDPs, solution techniques are particularly appropriate for characterizing their biophysical properties, and structural ensembles in agreement with these data provide a convenient tool for describing the underlying conformational sampling. Database entries consist of (i) primary experimental data with descriptions of the acquisition methods and algorithms used for the ensemble calculations, and (ii) the structural ensembles consistent with these data, provided as a set of models in a Protein Data Bank format. PE-DB is open for submissions from the community, and is intended as a forum for disseminating the structural ensembles and the methodologies used to generate them. While the need to represent the IDP structures is clear, methods for determining and evaluating the structural ensembles are still evolving. The availability of the pE-DB database is expected to promote the development of new modeling methods and leads to a better understanding of how function arises from disordered states. PMID:24174539

  18. 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.

  19. 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.

  20. Hysteresis in magnetic shape memory composites: Modeling and simulation

    NASA Astrophysics Data System (ADS)

    Conti, Sergio; Lenz, Martin; Rumpf, Martin

    2016-04-01

    Magnetic shape memory alloys are characterized by the coupling between the reorientation of structural variants and the rearrangement of magnetic domains. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the reorientation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the twin boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimality condition. We illustrate and discuss the influence of the particle geometry (volume fraction, shape, arrangement) and the polymer elastic parameters on the observed hysteresis and compare with recent experimental results.

  1. Deformation Hysteresis of Electrohydrodynamic Patterning on a Thin Polymer Film.

    PubMed

    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

  2. Hysteresis of soft joints embedded with fluid-filled microchannels

    PubMed Central

    Ghatak, Animangsu; Majumder, Abhijit; Kumar, Rajendra

    2008-01-01

    Many arthropods are known to achieve dynamic stability during rapid locomotion on rough terrains despite the absence of an elaborate nervous system. While muscle viscoelasticity and its inherent friction have been thought to cause this passive absorption of energy, the role of embedded microstructures in muscles and muscle joints has not yet been investigated. Inspired by the soft and flexible hinge joints present in many of these animals, we have carried out displacement-controlled bending of thin elastic slabs embedded with fluid-filled microchannels. During loading, the slab bends uniformly to a critical curvature, beyond which the skin covering the channel buckles with a catastrophic decrease in load. In the reverse cycle, the buckled skin straightens out but at a significantly lower load. In such a loading–unloading cycle, this localized buckling phenomenon results in a dynamic change in the geometry of the joint, which leads to a significant hysteresis in elastic energy. The hysteresis varies nonlinearly with channel diameters and thicknesses of the slab, which is captured by a simple scaling analysis of the phenomenon. PMID:18611846

  3. The capillary hysteresis model HYSTR: User`s guide

    SciTech Connect

    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.

  4. 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.

  5. Ionic Origin of Electro-osmotic Flow Hysteresis.

    PubMed

    Lim, Chun Yee; Lim, An Eng; Lam, Yee Cheong

    2016-01-01

    Electro-osmotic flow, the driving of fluid at nano- or micro- scales with electric field, has found numerous applications, ranging from pumping to chemical and biomedical analyses in micro-devices. Electro-osmotic flow exhibits a puzzling hysteretic behavior when two fluids with different concentrations displace one another. The flow rate is faster when a higher concentration solution displaces a lower concentration one as compared to the flow in the reverse direction. Although electro-osmotic flow is a surface phenomenon, rather counter intuitively we demonstrate that electro-osmotic flow hysteresis originates from the accumulation or depletion of pH-governing minority ions in the bulk of the fluid, due to the imbalance of electric-field-induced ion flux. The pH and flow velocity are changed, depending on the flow direction. The understanding of electro-osmotic flow hysteresis is critical for accurate fluid flow control in microfluidic devices, and maintaining of constant pH in chemical and biological systems under an electric field. PMID:26923197

  6. Hysteresis in magnetic shape memory composites: Modeling and simulation

    NASA Astrophysics Data System (ADS)

    Conti, Sergio; Lenz, Martin; Rumpf, Martin

    2016-04-01

    Magnetic shape memory alloys are characterized by the coupling between a structural phase transition and magnetic one. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the transformation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the phase boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimality condition. We illustrate and discuss the influence of the particle geometry (volume fraction, shape, arrangement) and the polymer elastic parameters on the observed hysteresis and compare with recent experimental results.

  7. Wavenumber selection and hysteresis in nonlinear baroclinic flow

    NASA Technical Reports Server (NTRS)

    Chou, Shih-Hung

    1995-01-01

    Wavenumber transition and hysteresis in a highly unstable baroclinic flow are investigated using a high-resolution spectral numerical model. As the flow becomes more supercritical, the dominant wave gradually shifts from the most unstable wave predicted by the linear theory to a longer wave with a larger time-averaged amplitude, while the rectified mean flow attains a stronger shear at the center of the channel. The numerical results display a complex hysteresis behavior, which occurs not only between the states of different dominant wavenumbers, but also between the states of identical dominant wavenumber but of different dynamic characteristics. In a certain parameter range three stable states, each with different dominant wavenumber, are possible, and in another parameter range four stable states are possible, among them three stable states with an identical dominant wave. The numerical results suggest that a multiple weather regime exists even without external forcing in which the flow aperiodically varies between two distinct behaviors. The effects of stable higher harmonics are assessed and it is found that their presence contributes not only to the better approximation of the model solutions but also to the selection of the final equilibrium state, due to the chaotic nature of the initial transient period.

  8. 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.

  9. Ionic Origin of Electro-osmotic Flow Hysteresis

    NASA Astrophysics Data System (ADS)

    Lim, Chun Yee; Lim, An Eng; Lam, Yee Cheong

    2016-02-01

    Electro-osmotic flow, the driving of fluid at nano- or micro- scales with electric field, has found numerous applications, ranging from pumping to chemical and biomedical analyses in micro-devices. Electro-osmotic flow exhibits a puzzling hysteretic behavior when two fluids with different concentrations displace one another. The flow rate is faster when a higher concentration solution displaces a lower concentration one as compared to the flow in the reverse direction. Although electro-osmotic flow is a surface phenomenon, rather counter intuitively we demonstrate that electro-osmotic flow hysteresis originates from the accumulation or depletion of pH-governing minority ions in the bulk of the fluid, due to the imbalance of electric-field-induced ion flux. The pH and flow velocity are changed, depending on the flow direction. The understanding of electro-osmotic flow hysteresis is critical for accurate fluid flow control in microfluidic devices, and maintaining of constant pH in chemical and biological systems under an electric field.

  10. Ionic Origin of Electro-osmotic Flow Hysteresis

    PubMed Central

    Lim, Chun Yee; Lim, An Eng; Lam, Yee Cheong

    2016-01-01

    Electro-osmotic flow, the driving of fluid at nano- or micro- scales with electric field, has found numerous applications, ranging from pumping to chemical and biomedical analyses in micro-devices. Electro-osmotic flow exhibits a puzzling hysteretic behavior when two fluids with different concentrations displace one another. The flow rate is faster when a higher concentration solution displaces a lower concentration one as compared to the flow in the reverse direction. Although electro-osmotic flow is a surface phenomenon, rather counter intuitively we demonstrate that electro-osmotic flow hysteresis originates from the accumulation or depletion of pH-governing minority ions in the bulk of the fluid, due to the imbalance of electric-field-induced ion flux. The pH and flow velocity are changed, depending on the flow direction. The understanding of electro-osmotic flow hysteresis is critical for accurate fluid flow control in microfluidic devices, and maintaining of constant pH in chemical and biological systems under an electric field. PMID:26923197

  11. 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.

  12. Switched capacitor charge pump reduces hysteresis of piezoelectric actuators over a large frequency range.

    PubMed

    Huang, Liang; Ma, Yu Ting; Feng, Zhi Hua; Kong, Fan Rang

    2010-09-01

    Piezoelectric actuators exhibit large hysteresis between the applied voltage and their displacement. A switched capacitor charge pump is proposed to reduce hysteresis and linearize the movement of piezoelectric actuators. By pumping the same amount of charges into the piezoelectric actuator quantitatively, the actuator will be forced to change its length with constant step. Compared with traditional voltage and charge driving, experimental results demonstrated that the piezoelectric stack driven by the charge pump had less hysteresis over a large frequency range, especially at ultralow frequencies. A hysteresis of less than 2.01% was achieved over a frequency range of 0.01-20 Hz using the charge pump driver. PMID:20886997

  13. Hysteresis analysis for the permanent magnet assisted synchronous reluctance motor by coupled FEM and Preisach modelling

    SciTech Connect

    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.

  14. Equivalent circuit representation of hysteresis in solar cells that considers interface charge accumulation: Potential cause of hysteresis in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Seki, Kazuhiko

    2016-07-01

    If charge carriers accumulate in the charge transport layer of a solar cell, then the transient response of the electric field that originates from these accumulated charges results in hysteresis in the current-voltage (J-V) characteristics. While this mechanism was previously known, a theoretical model to explain these J-V characteristics has not been considered to date. We derived an equivalent circuit from the proposed hysteresis mechanism. By solving the equivalent circuit model, we were able to reproduce some of the features of hysteresis in perovskite solar cells.

  15. Doping evolution of magnetization hysteresis in (Ba1-xKx)Fe2 As2 single crystals: Crossover from the second magnetization peak to peak effect

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Lograsso, Thomas

    Magnetic hysteresis loops (MHLs) have been systematically measured in a series of (Ba1-xKx)Fe2As2 single crystals from underdoped x =0.177 to end member x =1 with applied magnetic fields parallel to c axis (H//c). The second magnetization peak (SMP) or fishtail effect was observed within the doping range 0.177 <=x <=0.650. Remarkably, with further increasing doping the SMP becomes narrow and emerges very close to the irreversible field (Hirr) for the samples 0.692 <=x <=0.910. The similar peak effect (PE) had been widely observed in various conventional or low Tc superconductors. Meanwhile, the magnetization curves change from symmetrical to asymmetric hysteresis loops, which suggests a dominant surface pinning instead of bulk pinning in the samples. Our findings demonstrate that (Ba1-xKx)Fe2As2 system is a very unique system that that links the SMP and PE by its doping dependence. Our results will lead to a better understanding of the underlying mechanisms for the origin of the SMP and PE. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.

  16. Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress. Progress report, June 1991--December 1991

    SciTech Connect

    Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

    1992-01-01

    The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters.

  17. Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis.

    PubMed

    Hozumi, Atsushi; McCarthy, Thomas J

    2010-02-16

    Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis for probe liquids were prepared by chemical vapor deposition (CVD) of bis((tridecafluoro-1,1,2,2,-tetrahydrooctyl)-dimethylsiloxy)methylsilane (CF(3)(CF(2))(5)CH(2)CH(2)Si(CH(3))(2)O)(2)SiCH(3)H, (R(F)Si(Me)(2)O)(2)SiMeH). Oxidized aluminum surfaces were prepared by photooxidation/cleaning of sputter-coated aluminum on silicon wafers (Si/Al(Al(2)(O(3)))) using oxygen plasma. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) confirmed that this facile CVD method produces a monolayer with a thickness of 1.1 nm on the Si/Al(Al(2)(O(3))) surface without a discernible change in surface morphology. After monolayer deposition, the hydrophilic Si/Al(Al(2)(O(3))) surface became both hydrophobic and oleophobic and exhibited essentially no contact angle hysteresis for water and n-hexadecane (advancing/receding contact angles (theta(A)/theta(R)) = 110 degrees/109 degrees and 52 degrees/50 degrees, respectively). Droplets move very easily on this surface and roll off of slightly tilted surfaces, independently of the contact angle (which is a practical definition of ultralyophobic). A conventional fluoroalkylsilane monolayer was also prepared from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CF(3)(CF(2))(7)CH(2)CH(2)Si(OCH(3))(3), R(F)Si(OMe)(3)) for comparison. The theta(A)/theta(R) values for water and n-hexadecane are 121 degrees/106 degrees and 76 degrees/71 degrees, respectively. The larger hysteresis values indicate the "pinning" of probe liquids, even though advancing contact angles are larger than those of the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers. The (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers have excellent hydrolytic stability in water. We propose that the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers are flexible and liquidlike and that drops in contact with these surfaces experience very low energy barriers between metastable states, leading to the

  18. Wilson-loop instantons

    NASA Technical Reports Server (NTRS)

    Lee, Kimyeong; Holman, Richard; Kolb, Edward W.

    1987-01-01

    Wilson-loop symmetry breaking is considered on a space-time of the form M4 x K, where M4 is a four-dimensional space-time and K is an internal space with nontrivial and finite fundamental group. It is shown in a simple model that the different vacua obtained by breaking a non-Abelian gauge group by Wilson loops are separated in the space of gauge potentials by a finite energy barrier. An interpolating gauge configuration is then constructed between these vacua and shown to have minimum energy. Finally some implications of this construction are discussed.

  19. Automatic one-loop calculations with Sherpa+OpenLoops

    NASA Astrophysics Data System (ADS)

    Cascioli, F.; Höche, S.; Krauss, F.; Maierhöfer, P.; Pozzorini, S.; Siegert, F.

    2014-06-01

    We report on the OpenLoops generator for one-loop matrix elements and its application to four-lepton production in association with up to one jet. The open loops algorithm uses a numerical recursion to construct the numerator of one-loop Feynman diagrams as functions of the loop momentum. In combination with tensor integrals this results in a highly efficient and numerically stable matrix element generator. In order to obtain a fully automated setup for the simulation of next-to-leading order scattering processes we interfaced OpenLoops to the Sherpa Monte Carlo event generator.

  20. Bouc-Wen hysteresis model identification using Modified Firefly Algorithm

    NASA Astrophysics Data System (ADS)

    Zaman, Mohammad Asif; Sikder, Urmita

    2015-12-01

    The parameters of Bouc-Wen hysteresis model are identified using a Modified Firefly Algorithm. The proposed algorithm uses dynamic process control parameters to improve its performance. The algorithm is used to find the model parameter values that results in the least amount of error between a set of given data points and points obtained from the Bouc-Wen model. The performance of the algorithm is compared with the performance of conventional Firefly Algorithm, Genetic Algorithm and Differential Evolution algorithm in terms of convergence rate and accuracy. Compared to the other three optimization algorithms, the proposed algorithm is found to have good convergence rate with high degree of accuracy in identifying Bouc-Wen model parameters. Finally, the proposed method is used to find the Bouc-Wen model parameters from experimental data. The obtained model is found to be in good agreement with measured data.

  1. Optical Bistability And Hysteresis In A Solid State Ring Laser

    NASA Astrophysics Data System (ADS)

    Kornienko, L. S.; Kravtsov, N. S.; Shelaev, A. N.

    1985-01-01

    The phenomena of optical bistability, hysteresis and memory under the interaction of oppositely directed (OD) light waves in a CW YAG:Nd3+ solid state ring laser (SRL) have been experimentally discovered. The possibilities of spontaneous or forced (with modulated SRL parameters) commutation of the radiation direction without transients at the relaxation frequency (typical for solid state lasers) have been established both in the single-mode and in the mode-locking regimes with various feedback circuits. The mode-locking band was found to be substantially broadened by more than an order of magnitude when OD light waves primarily diffracted on a standing ultrasonic wave were returned into the acousto-optical modulator. With such acousto-optical feedback the mode-locking regime has been obtained using a modulator on a running ultrasonic wave.

  2. Asymmetric Hysteresis for Probing Dzyaloshinskii–Moriya Interaction

    NASA Astrophysics Data System (ADS)

    Han, Dong-Soo; Kim, Nam-Hui; Kim, June-Seo; Yin, Yuxiang; Koo, Jung-Woo; Cho, Jaehun; Lee, Sukmock; Kläui, Mathias; Swagten, Henk J. M.; Koopmans, Bert; You, Chun-Yeol

    2016-07-01

    The interfacial Dzyaloshinskii-Moriya interaction (DMI) is intimately related to the prospect of superior domain-wall dynamics and the formation of magnetic skyrmions. Although some experimental efforts have been recently proposed to quantify these interactions and the underlying physics, it is still far from trivial to address the interfacial DMI. Inspired by the reported tilt of the magnetization of the side edge of a thin film structure, we here present a quasi-static, straightforward measurement tool. By using laterally asymmetric triangular-shaped microstructures, it is demonstrated that interfacial DMI combined with an in-plane magnetic field yields a unique and significant shift in magnetic hysteresis. By systematic variation of the shape of the triangular objects combined with a droplet model for domain nucleation, a robust value for the strength and sign of interfacial DMI is obtained. This method gives immediate and quantitative access to DMI, enabling a much faster exploration of new DMI systems for future nanotechnology.

  3. Magnetic hysteresis in a lanthanide molecular magnet dimer system

    NASA Astrophysics Data System (ADS)

    Atkinson, James; Cebulka, Rebecca; Del Barco, Enrique; Roubeau, Olivier; Velasco, Veronica; Barrios, Leo; Aromi, Guillem

    Molecular magnets present a wonderful means for studying the dynamics of spin. Often synthesized as a crystal lattice of identical systems, ensemble measurements enable thorough detailing of the internal degrees of freedom. Here we present the results of characterization performed on a dimer system, CeTm(HL)2(H2L)NO3pyH2O (L = ligand, C45H31O15N3), consisting of two lanthanide spins (Cerium and Thulium) with expected local axial anisotropies tilted with respect to each other. Microwave EPR spectroscopy at low temperature reveals hysteresis in observed absorption features, with angle dependence studies indicating the presence of several ``easy axis'' orientations. We attempt to understand this system through modelling via a spin Hamiltonian, and to determine the strength and nature of the coupling between the lanthanide centers. This research was funded through NSF Grant # 24086159.

  4. On the thermal expansion hysteresis of a UK PBX

    NASA Astrophysics Data System (ADS)

    Williamson, David; Palmer, Stewart; Govier, Rebecca

    2011-06-01

    The thermal expansion coefficient of a UK PBX has been measured over the temperature range -40 to +80 C. A subtle but measurable hysteresis in length as a function of temperature was observed. This is attributed to a miss-match between the thermal expansion coefficients of its solid-fill and binder constituents. On heating or cooling this induces mechanical stresses within the binder system, which being viscous it can flow to relieve. A change in sample temperature results in an asymptotic relaxation to a mechanical equilibrium length, which is described by an exponential dependence on time. This is analogous to the type of stress relaxation and creep behaviour normally associated with the bulk response of viscoelastic materials when more conventional stresses are applied.

  5. 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.

  6. Wafer-level hysteresis-free resonant carbon nanotube transistors.

    PubMed

    Cao, Ji; Bartsch, Sebastian T; Ionescu, Adrian M

    2015-03-24

    We report wafer-level fabrication of resonant-body carbon nanotube (CNT) field-effect transistors (FETs) in a dual-gate configuration. An integration density of >10(6) CNTFETs/cm(2), an assembly yield of >80%, and nanoprecision have been simultaneously obtained. Through combined chemical and thermal treatments, hysteresis-free (in vacuum) suspended-body CNTFETs have been demonstrated. Electrostatic actuation by lateral gate and FET-based readout of mechanical resonance have been achieved at room temperature. Both upward and downward in situ frequency tuning has been experimentally demonstrated in the dual-gate architecture. The minuscule mass, high resonance frequency, and in situ tunability of the resonant CNTFETs offer promising features for applications in radio frequency signal processing and ultrasensitive sensing. PMID:25752991

  7. Hysteresis-free nanoplasmonic Pd-Au alloy hydrogen sensors.

    PubMed

    Wadell, Carl; Nugroho, Ferry Anggoro Ardy; Lidström, Emil; Iandolo, Beniamino; Wagner, Jakob B; Langhammer, Christoph

    2015-05-13

    The recent market introduction of hydrogen fuel cell cars and the prospect of a hydrogen economy have drastically accelerated the need for safe and accurate detection of hydrogen. In this Letter, we investigate the use of arrays of nanofabricated Pd-Au alloy nanoparticles as plasmonic optical hydrogen sensors. By increasing the amount of Au in the alloy nanoparticles up to 25 atom %, we are able to suppress the hysteresis between hydrogen absorption and desorption, thereby increasing the sensor accuracy to below 5% throughout the investigated 1 mbar to 1 bar hydrogen pressure range. Furthermore, we observe an 8-fold absolute sensitivity enhancement at low hydrogen pressures compared to sensors made of pure Pd, and an improved sensor response time to below one second within the 0-40 mbar pressure range, that is, below the flammability limit, by engineering the nanoparticle size. PMID:25915663

  8. The thermodynamic origin of hysteresis in insertion batteries.

    PubMed

    Dreyer, Wolfgang; Jamnik, Janko; Guhlke, Clemens; Huth, Robert; Moskon, Joze; Gaberscek, Miran

    2010-05-01

    Lithium batteries are considered the key storage devices for most emerging green technologies such as wind and solar technologies or hybrid and plug-in electric vehicles. Despite the tremendous recent advances in battery research, surprisingly, several fundamental issues of increasing practical importance have not been adequately tackled. One such issue concerns the energy efficiency. Generally, charging of 10(10)-10(17) electrode particles constituting a modern battery electrode proceeds at (much) higher voltages than discharging. Most importantly, the hysteresis between the charge and discharge voltage seems not to disappear as the charging/discharging current vanishes. Herein we present, for the first time, a general explanation of the occurrence of inherent hysteretic behaviour in insertion storage systems containing multiple particles. In a broader sense, the model also predicts the existence of apparent equilibria in battery electrodes, the sequential particle-by-particle charging/discharging mechanism and the disappearance of two-phase behaviour at special experimental conditions. PMID:20383130

  9. Dynamics and hysteresis in square lattice artificial spin ice

    NASA Astrophysics Data System (ADS)

    Wysin, G. M.; Moura-Melo, W. A.; Mól, L. A. S.; Pereira, A. R.

    2013-04-01

    Dynamical effects under geometrical frustration are considered in a model for artificial spin ice on a square lattice in two dimensions. Each island of the spin ice has a three-component Heisenberg-like dipole moment subject to shape anisotropies that influence its direction. The model has real dynamics, including rotation of the magnetic degrees of freedom, going beyond the Ising-type models of spin ice. The dynamics is studied using a Langevin equation solved via a second-order Heun algorithm. Thermodynamic properties such as the specific heat are presented for different couplings. A peak in specific heat is related to a type of melting-like phase transition present in the model. Hysteresis in an applied magnetic field is calculated for model parameters where the system is able to reach thermodynamic equilibrium.

  10. Hysteresis of unsaturated hydromechanical properties of a silty soil

    USGS Publications Warehouse

    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.

  11. Hysteresis in coral reefs under macroalgal toxicity and overfishing.

    PubMed

    Bhattacharyya, Joydeb; Pal, Samares

    2015-03-01

    Macroalgae and corals compete for the available space in coral reef ecosystems.While herbivorous reef fish play a beneficial role in decreasing the growth of macroalgae, macroalgal toxicity and overfishing of herbivores leads to proliferation of macroalgae. The abundance of macroalgae changes the community structure towards a macroalgae-dominated reef ecosystem. We investigate coral-macroalgal phase shifts by means of a continuous time model in a food chain. Conditions for local asymptotic stability of steady states are derived. It is observed that in the presence of macroalgal toxicity and overfishing, the system exhibits hysteresis through saddle-node bifurcation and transcritical bifurcation. We examine the effects of time lags in the liberation of toxins by macroalgae and the recovery of algal turf in response to grazing of herbivores on macroalgae by performing equilibrium and stability analyses of delay-differential forms of the ODE model. Computer simulations have been carried out to illustrate the different analytical results. PMID:25708511

  12. The extrinsic hysteresis behavior of dilute binary ferrofluids.

    PubMed

    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

  13. Large melting point hysteresis of Ge nanocrystals embedded inSiO2

    SciTech Connect

    Xu, Q.; Sharp, I.D.; Yuan, C.W.; Yi, D.O.; Liao, C.Y.; Glaeser,A.M.; Minor, A.M.; Beeman, J.W.; Ridgway, M.C.; Kluth, P.; Ager III,J.W.; Chrzan, D.C.; Haller, E.E.

    2006-05-04

    The melting behavior of Ge nanocrystals embedded within SiO{sub 2} is evaluated using in situ transmission electron microscopy. The observed melting point hysteresis is large ({+-} 17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.

  14. Overview of Loop Heat Pipe Operation

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    1999-01-01

    Loop heat pipes (LHP's) are two-phase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in the porous wicks to circulate the fluid. The LHP was first developed in the former Soviet Union in the early 1980s, about the same time that the capillary pumped loop (CPL) was developed in the United States. The LHP is known for its high pumping capability and robust operation mainly due to the use of fine-pored metal wicks and an integral evaporator/hydro-accumulator design. The LHP technology is rapidly gaining acceptance in aerospace community. It is the baseline design for thermal control of several spacecraft, including NASA's GLAS and Chemistry, ESA's ATLID, CNES' STENTOR, RKA's OBZOR, and several commercial satellites. Numerous LHP papers have been published since the mid-1980's. Most papers presented test results and discussions on certain specific aspects of the LHP operation. LHP's and CPL's show many similarities in their operating principles and performance characteristics. However, they also display significant differences in many aspects of their operation. Some of the LHP behaviors may seem strange or mysterious, even to experienced CPL practitioners. The main purpose of this paper is to present a systematic description of the operating principles and thermal-hydraulic behaviors of LHP'S. LHP operating principles will be given first, followed by a description of the thermal-hydraulics involved in LHP operation. Operating characteristics and important parameters affecting the LHP operation will then be described in detail. Peculiar behaviors of the LHP, including temperature hysteresis and temperature overshoot during start-up, will be explained. For simplicity, most discussions will focus upon LHP's with a single evaporator and a single condenser, but devices with multiple evaporators and condensers will also be discussed. Similarities and differences between LHP's and

  15. Livermore Compiler Analysis Loop Suite

    Energy Science and Technology Software Center (ESTSC)

    2013-03-01

    LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizationsmore » and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.« less

  16. Livermore Compiler Analysis Loop Suite

    SciTech Connect

    Hornung, R. D.

    2013-03-01

    LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizations and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.

  17. 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

  18. On damping characteristics of frictional hysteresis in pre-sliding range

    NASA Astrophysics Data System (ADS)

    Ruderman, Michael; Iwasaki, Makoto

    2016-06-01

    Frictional hysteresis at relative motion in the pre-sliding range is considered. This effect is characterized by an elasto-plastic interaction, and that on the micro-scale, between two rubbing surfaces in contact that gives rise to nonlinear friction force. The pre-sliding friction force yields hysteresis in displacement. In this study, the damping characteristics of frictional hysteresis are analyzed. It is worth noting that we exclude the viscous damping mechanisms and focus on the pure hysteresis damping to be accounted in the friction modeling. The general properties of pre-sliding friction hysteresis are demonstrated and then compared with the limit case of discontinuous Coulomb friction. Further we consider two advanced dynamic friction models, LuGre and Maxwell-slip, so as demonstrate their damping properties and convergence of the motion system to equilibrium state. Experimental observations of the free motion in pre-sliding range are also shown and discussed.

  19. 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.

  20. Role of connecting loop I in catalysis and allosteric regulation of human glucokinase

    PubMed Central

    Martinez, Juliana A; Larion, Mioara; Conejo, Maria S; Porter, Carol M; Miller, Brian G

    2014-01-01

    Glucokinase (GCK, hexokinase IV) is a monomeric enzyme with a single glucose binding site that displays steady-state kinetic cooperativity, a functional characteristic that affords allosteric regulation of GCK activity. Structural evidence suggests that connecting loop I, comprised of residues 47–71, facilitates cooperativity by dictating the rate and scope of motions between the large and small domains of GCK. Here we investigate the impact of varying the length and amino acid sequence of connecting loop I upon GCK cooperativity. We find that sequential, single amino acid deletions from the C-terminus of connecting loop I cause systematic decreases in cooperativity. Deleting up to two loop residues leaves the kcat value unchanged; however, removing three or more residues reduces kcat by 1000-fold. In contrast, the glucose K0.5 and KD values are unaffected by shortening the connecting loop by up to six residues. Substituting alanine or glycine for proline-66, which adopts a cis conformation in some GCK crystal structures, does not alter cooperativity, indicating that cis/trans isomerization of this loop residue does not govern slow conformational reorganizations linked to hysteresis. Replacing connecting loop I with the corresponding loop sequence from the catalytic domain of the noncooperative isozyme human hexokinase I (HK-I) eliminates cooperativity without impacting the kcat and glucose K0.5 values. Our results indicate that catalytic turnover requires a minimal length of connecting loop I, whereas the loop has little impact upon the binding affinity of GCK for glucose. We propose a model in which the primary structure of connecting loop I affects cooperativity by influencing conformational dynamics, without altering the equilibrium distribution of GCK conformations. PMID:24723372